BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention relates to a recording apparatus and a recording method using
a recording head, on which a plurality of recording elements are arranged, when recording.
In particular the present invention relates to a recording apparatus such as an ink-jet
printer and the like using the recording head by ejecting ink from a plurality of
nozzles arranged thereon, when recording.
2. Brief Description of the Related Art
[0002] Recently recording apparatuses employing an ink-jet method for recording on a recording
medium by ejecting ink from nozzles arranged on the recording head, have been being
widely applied to printers, facsimile machines, copying machines and so forth. Particularly,
color printers capable of recording color images by using plurality of colors have
been remarkably widely being used as images of high quality have been enhanced with
progress of the color printers. In addition to a high quality image, a higher recording
rate is an important factor for the recording apparatus to spread widely so that liquid
droplet eject driving frequencies of recording heads have been being raised higher
along with the increasing number of nozzles arranged in the recording heads for higher-rated
recording.
[0003] However, in ink-jet apparatuses, sometimes statuses so called "non-eject", where
ink droplets can not be ejected, are caused by dust entered into nozzles of the recording
head during production of the head and deteriorated nozzles due to a long period use,
deteriorated elements to eject ink and so forth. In the case of the non-eject caused
by deteriorated nozzles or elements, it is likely that the non-eject happens casually
when the recording apparatuses are in use.
[0004] In some cases statuses where ejecting directions of ink droplets are deviated largely
from a desired direction (hereinafter also referred as "twisted ejection") and statuses
where ejecting volumes of ink droplets are different largely from a desired volume
(hereinafter also referred as "dispersion in droplet diameter") are observed in stead
of non-eject statuses. Since such deteriorated nozzles largely deteriorate quality
of recorded images, these nozzles can not be employed for recording. Hereinafter such
nozzles are also included in and explained as the non-eject statuses.
[0005] Such non-eject statues and so forth were not so problematic in the past, since non-eject
status generating frequencies could be suppressed by modifying manufacturing conditions
and the like. However, the non-eject statuses have become problems not to be ignored,
as nozzle numbers have been increased for attaining the above-mentioned higher-rate
recording. In order to manufacture recording heads which do not include non-eject
nozzles and excellent recording heads which hardly cause the non-eject statuses, manufacturing
costs will be increased, which leads to higher cost recording heads.
[0006] When the non-eject statuses occur, defects such as white streaks and the like are
observed in recorded images. In order to compensate such white streaks, techniques
such that white streaks are compensated by recording with other normal nozzles by
utilizing a divided recording method where the recording head is scanned a plurality
of times for recording.
[0007] However, in order to attain the above-mentioned higher-rate recording, it is preferable
to finish recording by one scanning, so called "one path recording", but it is very
difficult to compensate unrecorded portions due to the non-eject statuses or to make
such portions unrecognizable in the one path recording. In another recording method
for recording by executing a plurality of scanning on a predetermined area in a recording
medium, so called "multi scan", sometimes it is difficult to compensate completely
depending on positions or the number of non-eject nozzles.
SUMMARY OF THE INVENTION
[0008] The present invention is carried out in view of the above-mentioned problems, and
to provide an ink-jet recording apparatus capable of removing unevenness such as white
streaks and the like generated in recorded images due to unrecorded dots caused by
the non-eject statuses, or making white streaks unrecognizable by human eyes even
when the non-eject statuses occur in order to suppress cost increase of the recording
head. Further the present invention provides the recording apparatus capable of recording
at a higher recording rate.
[0009] The following constitution by the present invention solves the problems mentioned
above.
(1) A recording apparatus for recording a color image on a recording medium by utilizing
a recording head on which a plurality of recording elements are arrayed, comprising:
recording head driving means to drive the plurality of recording elements of the recording
head in accordance with image data; plurality of compensation means to compensate
a position to be recorded by a recording element which does not execute a recording
operation, among the recording elements, by utilizing respective different methods;
and selection means to employ selectively at least one compensation means from the
plurality of compensation means in accordance with a kind of medium to be recorded.
(2) The recording apparatus according to (1), wherein the plurality of compensation
means comprises a first compensation means which executes a compensation recording
operation on a corresponding position where the recording element does not execute
the recording operation, by a different color from the corresponding color to the
recording element which does not execute the recording operation.
(3) The recording apparatus according to (1), wherein the plurality of compensation
means comprises a second compensation means which compensates a position to be recorded
by the recording element which does not execute the recording operation by correcting
image data corresponding to recording elements in the vicinity of the recording element
which does not execute the recording operation based on image data corresponding to
the recording element which does not execute the recording operation.
(4) The recording apparatus according to claim (1), wherein: said plurality of compensation
means comprises; a first compensation means which executes compensation recording
on a position to be recorded by the recording element which does not execute the recording
operation, by a different color from the corresponding color to the recording element
which does not execute the recording operation; and a second compensation means which
execute compensation recording on a position to be recorded by the recording element
which does not execute the recording operation by correcting corresponding image data
to recording elements in the vicinity of the recording element which does not execute
the recording operation based on corresponding image data to the recording element
which does not execute the recording operation.
(5) The recording apparatus according to (4), wherein when the kind of medium is a
first medium to be recorded, only the second compensation means is selected, and when
the kind of medium is a second medium to be recorded, at least the first compensation
means is selected.
(6) The recording apparatus according to (4), wherein the selection means selects
only the second compensation means, when the kind of medium is the first medium to
be recorded, and the selection means selects both the first compensation means and
the second compensation means, when the kind of medium is the second medium to be
recorded.
(7) The recording apparatus according to (5) or (6), wherein the first medium to be
recorded is an ordinary paper, and the second medium to be recorded is a glossy paper.
(8) The recording apparatus according to (5) or (6), wherein the first recording medium
to be recorded is a medium with a blotting rate, 2.5 or more, and the second recording
medium to be recorded is a medium with a blotting rate less than 2.5.
(9) The recording apparatus according to either one of (2), (4), (5) and (6), wherein
the first compensation means executes recording operations corresponding to respective
plurality of colors, and at the same time executes compensation recording operations
by employing a color having similar lightness to a corresponding color to the recording
element which does not execute the recording operation.
(10) The recording apparatus according to (9), wherein the first compensation means
has a correction means for correcting image data corresponding to the recording element
which does not execute the recording operation in accordance with a corresponding
color to a recording element employed for a compensation recording operation, and
executes the compensation recording based on the corrected image data by the compensation
means.
(11) The recording apparatus according to either one of (3) to (6), wherein the second
means corrects density data indicated by corresponding image data to recording elements
in the vicinity of the recording element which does not execute a recording operation,
based on density data indicated by corresponding image data to the recording element
which does not execute the recording operation.
(12) The recording apparatus according either one of (1) to (11), wherein the recording
element which does not execute the recording operation includes a recording element
incapable of executing the recording operation.
(13) The recording apparatus according to either one of (1) to (12), wherein the recording
head is an ink-jet head having a plurality of nozzles from which ink is ejected for
recording when the recording elements are driven.
(14) The recording apparatus according to (13), wherein the recording element consists
of an electro-thermal body which supplies thermal energy to ink so that ink is ejected
from the nozzle by bubbles generated in ink by the thermal energy.
(15) The recording apparatus according to either one of (1) to (14), wherein the recording
head further comprises a measuring means to measure a blotting rate of the medium
to be recorded.
(16) The recording apparatus according to either one of (1) to (15), wherein the recording
head further comprises a control means to control ejecting quantity of the recording
head in order to execute the compensation recording operation only by the second compensation
means, when the first medium to be recorded is selected.
(17) A recording method for recording a color image on a recording medium by utilizing
a recording head on which a plurality of recording elements are arrayed, comprising
steps of: identifying a recording element which does not execute a recording operation;
recognizing a kind of medium to be recorded; selecting at least one compensation method
among the plurality of respectively different compensation methods for compensating
a position to be recorded by a recording element which does not execute the recording
operation; recording for compensation on the position to be recorded by the recording
element which does not execute the recording operation, wherein: in the selecting
step at least one compensation method is selected among the plurality of respectively
different compensation methods in accordance with the recognized medium to be recorded
in said recognizing step.
(18) A program for carrying out the method described in (17).
(19) A program to run a computer for controlling a recording apparatus for recording
a color image on a recording medium by utilizing a recording head on which a plurality
of recording elements are arrayed, comprising steps of: identifying a recording element
which does not execute a recording operation; recognizing kinds of media to be recorded;
selecting at least one compensation method among the plurality of respectively different
compensation methods for compensating a position to be recorded by a recording element
which does not execute the recording operation in accordance with a kind of recognized
medium to be selected.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010]
FIG.1A is a schematic drawing showing a defect status of a recorded image, FIG.1B
is a schematic drawing showing a compensated defect shown in FIG.1A.
FIG.2 is a block diagram showing a method for compensating non-eject nozzles of a
recording head by using only black ink nozzles in all cases of low recording duty
and high recording duty.
FIGs.3A, 3B, 3C, 3D and 3E are schematic drawings for explaining non-eject dots and
compensation ways in a case of an image formed by one dot per pixel.
FIG.4 is a graph showing a relation between input data and brightness (output data).
FIG.5 is a graph showing conversion examples when recording defects are compensated
by different colors.
FIG.6 is a graph showing conversion examples when recording defects are compensated
by different colors.
FIG.7 is a graph showing conversion examples when recording defects are compensated
by different colors.
FIG.8 is a flow chart showing operational procedures by a data conversion circuit.
FIG.9 is a side sectional view showing an arrangement of a color copying machine as
an example of the ink-jet recording apparatus by the present invention.
FIG.10 is a drawing for explaining a CCD line sensor (photo sensor) in detail.
FIG.11 is a perspective outline view of an ink-jet cartridge.
FIG.12 is a perspective view showing a printed circuit board 85 in detail.
FIGs.13A and 13B are drawings showing main circuit components of the printed circuit
board 85.
FIG.14 is an explanatory drawing showing an example of time sharing driving chart
for heating elements 857.
FIG.15A is a schematic drawing showing a recorded status by an ideal recording head
and FIG.15B is a schematic drawing showing a recorded status with drop diameter dispersions
and with twisted ejection.
FIG.16A is a schematic drawing showing a 50% half toned status by an ideal recording
head and FIG.16B is a schematic drawing showing a 50% half toned status with dispersed
drop diameters and twists.
FIG.17 is a block diagram showing an arrangement of an image processing unit by the
present embodiment.
FIG.18 is a graph showing a relation between input and output data in a γ conversion
circuit 95.
FIG.19 is a block diagram showing an arrangement of main portion of a data processing
unit 100 for explaining its functions.
FIG.20 is a graph showing examples of density compensation tables against nozzles.
FIG.21 is a graph showing examples of non-linear density compensation tables against
nozzles.
FIG.22 is a perspective outline view of the main body an ink-jet recording apparatus.
FIG.23 is an explanatory drawing showing recorded output status of a nonuniformity
pattern for reading.
FIG.24 is an explanatory drawing showing a recorded pattern by the recording head
having 128 nozzles.
FIGs.25A, 25B and 25C are explanatory drawings showing read recorded density curve
patterns.
FIG.26 is an explanatory drawing showing a relation between a recorded density curve
pattern and nozzles.
FIG.27 is a drawing for explaining statuses of pixels in an area to be read.
FIG.28 is a drawing for explaining data of pixel density.
FIG.29A is a graph showing a relation between brightness in compensated area b in
FIG.1B and distance of distinct vision of the compensated area b, FIG.29B is a graph
showing a relation between distance of distinct vision and unrecognized defect width
with and without compensation by minimum lightness(ca.56) and FIG.29C is an enlarged
graph of a lowermost and leftmost portion of FIG.29B
FIG.30A is a drawing showing an enlarged thinned Bk dot pattern 341 in FIG.30B. FIG30B
is a drawing showing a compensation examples of the defect portion b compensated by
the thinned Bk dot patterns.
FIG.31A is an example of a recorded pattern compensated by black ink dots from neighbor
nozzles and FIG.31B is a score table on non-uniformity of the recorded pattern in
FIG.32B.
FIG.32 is a graph based on the score table in FIG.31B.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0011] Hereinafter preferred embodiments by the present invention are explained.
[0012] In this specification nozzles where non-eject statuses occur, nozzles of which eject
directions of ink droplets are largely deviated from a desired direction and nozzles
which eject ink volumes largely different from a desired ink volume, are explained
as nozzles in incapable states of recording. In the present invention these nozzles
are treated as nozzles which do not execute recording operations or as recording elements
which do not execute recording operations. Recording operations to compensate positions
not recorded by these nozzles or positions not recorded by these nozzles are explained
in detail. Nozzles or recording elements brought to abnormal recording statuses are
also represented as bad nozzles or bad recording elements in this specification.
[0013] Through diligent research and study on compensation methods against non-eject statuses,
the present inventors learned that it is preferable to use a plurality of compensation
methods properly in accordance with media to be recorded.
[0014] Namely, since blotting behaviors of deposited ink droplets on media to be recorded
are different depending on the media, compensation methods to remove streaks caused
by non-eject statuses are different.
[0015] Here a blotting rate is defined for description hereinafter. An ink droplet ejected
from the recording head is impacted and diffused on a medium to be recorded so that
a dot is formed on the medium. The blotting rate is defined as a ratio of dot diameter
to ink droplet diameter.
[0016] A criterion value to judge whether the blotting rate is large or small is considered
ca. 2.5 times.
[0017] In other words, it is a known observed fact that an ink droplet ejected from the
ink-jet recording apparatus and impacted on the medium where a diameter of the impacted
droplet is about two times a diameter of a flying ink droplet.
[0018] Afterward, the impacted ink droplet is absorbed in the medium to be recorded. In
the medium to be recorded with high permeability of ink, even in a case of so called
ordinary paper such as PPC (Plain Paper Copier) in which sizing agent as anti-blotting
agent is included, the ink droplet permeated to a large extent so that the blotting
rate goes beyond 2.5 times. When permeability of ink is low, ink does not permeated
too much after the impact on the medium. Since ink dots are formed depending evaporating
and swelling statuses of volatile components in ink, the blotting rate exceeds not
too much from two times, sometimes less than two times.
[0019] Regardless of ink permeability, special media on which coat layers are formed for
controlling blotting behaviors of ink, are mainly used so as to make dot diameter
smaller for enhancing image quality by improving granular feel of the dot. The blotting
rate of glossy paper is around two times.
[0020] In other words, coat layers are formed so as to suppress permeability in a horizontal
direction on the media surfaces.
[0021] In a medium to be recorded with high blotting rate, it is possible to make nonuniformity
hardly to be seen by recording more dots from neighboring nozzles including next neighbor
nozzles to a non-eject nozzle, when a width of a non-eject portion is narrow. In a
recording operation with a high recording duty, when a solid area image is recorded
with increased quantity of ink per unit area of the medium, non-eject portions on
the image can not be recognized due to spreading blots of dot group toward non-eject
area on the medium.
[0022] On the other hand, in a recording operation with a low recording duty, it is possible
to make nonuniformity hardly to be recognized by recording more dots from neighboring
nozzles including next neighbor nozzles to the non-eject nozzle as shown in FIGs.3A
to 3E so as to compensate macroscopic density regardless of media to be recorded.
[0023] Though a width of a non-eject portion which is hardly recognized, is varies depending
on volume of ink droplets, the width is preferably within around 70 µm for compensating
the non-eject portion is compensated by dots from neighboring nozzles including neighbor
nozzles to the non-eject portion.
[0024] Ink with high permeability is preferable, when the ordinary paper is recorded. The
preferable blotting rate is more than 2.5 times. It is desirable to employ a coated
paper and the like with the blotting rate more than 2.5 times, even if ink with low
permeability is employed.
[0025] In the glossy paper with the blotting rate less than 2.5, original dot diameters
are small and dot group are hardly spread even when recorded more from neighboring
dots, consequently the non-eject portion is hardly compensated. Therefore, compensation
by other color dots is effective.
[0026] Whether compensations by other colors are executed on media to be recorded or not
can be predetermined by the main body of the recording apparatus, a printer driver
or the like. It is preferable to employ an arrangement where an ink droplet is recorded
on a recording medium and a dot diameter on the medium is measured.
[0027] Hereinafter, a recording method for compensating unrecorded portions caused by bad
nozzles and a method for making the white streak inconspicuous, are respectively explained
in detail.
<Compensation through Lightness>
[0028] Under-mentioned examples are recording methods in which dots are compensated by different
color nozzles instead of nozzles incapable of recording due to generated non-eject
statuses or the like. Based on output data (hereinafter also referred as image data)
corresponding to non-eject nozzles where non-eject statuses occur, compensated recording
operations are executed by generating output data corresponding to compensating nozzles
so that lightness of image to be recorded with original output data matches to lightness
of image to be recorded with other color nozzles used for compensation on a predetermined
level. In order to match lightness of uniformly recorded image by a compensating color
to lightness of uniformly recorded image by output data corresponding to the non-eject
color on the predetermined level, output data corresponding to the color nozzles to
be used for the compensation, are generated. When unrecorded portions caused by non-eject
statuses are recorded with even other compensating colors after matching lightness
on the predetermined level as mentioned above, it is possible to make non-eject portions
inconspicuous.
[0029] It is desirable to select a compensating color having a near chromaticity to that
of the non-eject color. A color combination comprising cyan (hereinafter referred
as C), magenta (hereinafter referred as M), yellow (hereinafter referred as Y) and
black (hereinafter referred as Bk), is employed in ordinary color ink-jet printers.
Among these colors it is possible to use M having nearly similar lightness to that
of C or to use Bk having a relatively near lightness to that of C for compensating
non-eject C nozzles. More specifically, data to be recorded by C nozzles are converted
to M or Bk data so that a difference in lightness between C and M or Bk is in a predetermined
range, and converted M or Bk data are added to original M or Bk data and outputted.
[0030] Even when non-eject statuses occur, it is possible to compensate non-eject statuses
by executing compensating procedures shown in FIG.2.
[0031] FIG.2 is the block diagram/the flow chart illustrating the above-mentioned compensation
procedure by lightness. At first, a non-eject head and non-eject nozzles are recognized
at step S1. More specifically, data on non-eject nozzles detected during manufacturing
are written in EEPROM beforehand and are readout afterward, non-eject nozzles are
judged from outputted image by a recording apparatus and non-eject nozzles are detected
by a sensor.
[0032] Various detecting arrangements such as an arrangement to detect eject statuses of
ink optically, an arrangement to detect non-eject portions by reading a tentatively
recorded image and so forth are applicable to this detecting step. At step S2, output
data (multi-data) on non-eject color are read and data are converted to lightness
(hereinafter also referred as L*) of the color. At step S3, data on a color to be
used for compensating the non-eject color are generated based on corresponding lightness
data of the non-eject nozzle. As mentioned above, the data for the compensation are
generated so as to match the lightness to the predetermined level. At this step, a
table where output data of respective colors and corresponding lightness of respective
colors are stored, can be used for converting output data corresponding to non-eject
color. A table 21 shown in FIG.2 is a table used for the compensation by the black
ink, which will be explained below.
[0033] The present inventors have found the fact that an unrecorded portion b with width
d in an image as shown in FIG.1A is recognized as a white streak before the compensation,
but when the unrecorded portion b is recorded by another compensating color, the recorded
portion b is merged into surrounding colors by adjusting lightness of the compensating
color near to that of an original color a, when the width d is sufficiently narrow
even if the compensating color is different from the original color.
[0034] FIG.1A shows a state where the unrecorded portion b with the width d is generated
in the image with the color a. FIG.1B shows a compensated state where the unrecorded
portion is compensated by another color so as to near its lightness to that of the
original color. Experiments whether the unrecorded portion b without compensations
and the compensated portion by another color, for example, by Bk can be recognized
as a nonuniformity or not, are carried out by varying a distance between the image
to be observed and eyes of an observer.
[0035] An experimental example where a red color with a lightness ca. 51 is selected for
the portion a in FIGs.1A and 1B and the portion b in FIGs.1A and 1B is compensated
by varying the lightness of a gray color, is explained.
[0036] FIG.29A is the graph where axis of abscissa represents lightness (L*, lightness of
the portion b) of compensating gray color and axis of ordinate represents range of
clear vision i.e. a distance from where nonuniformity in the compensated portion can
not be recognized.
[0037] In the experiment coated paper (product No.: HR101) manufactured by Canon Kabushiki
Kaisha (hereinafter referred as Canon K.K.) is used as the medium to be recorded.
One path recording on the coated paper is recorded by the ink-jet printer BJF850 manufactured
by Canon K.K. The gray color is generated by mixing C, M, Y and Bk.
[0038] Intermediate gradation is generated by mixing three colors, C, M and Y, i.e. by a
so-called process Bk and high gradation is generated by adding Bk and gradually extracting
C, M and Y. A process for generating the gray color employing color inks and black
ink is executed by referring to a table corresponding to a selected gradation value.
[0039] From FIG.29A it is understood that distances from where the white streak can not
be recognized (i.e. range of clear vision) are different from the lightness of the
compensated portion of b. From curves depicted in FIG.29A it is deduced that distances
from where the nonuniformety such as the white streak and the like can not be recognized,
indicate smaller values, when the lightness of the portion b nears to brightness of
the portion a, i.e. around 51.
[0040] It is also deduced from FIG.29A that when the lightness of the portion b is set within
a range of the lightness of the portion a ±10, the compensation is effective. The
digits ±10 corresponds to ±20% of the lightness 51 of the portion a. Almost the same
relations between two lightness are obtained when the lightness of the portion a is
varied.
[0041] Preferably when the lightness of the portion b is set within a range of ±10% of the
lightness of the portion a, compensation effects are raised.
[0042] It is also understood from FIG.29A that when the width of portion b is smaller, a
little bit larger lightness (a little bit brighter) of the portion b than that of
the portion a makes range of clear vision shorter. It is considered that this fact
is caused due to dense color (lower lightness) at blotted and overlapped boundaries
between portions of a and b.
[0043] Particularly since the gray color is formed by above-mentioned process Bk, blotted
areas are relatively spread.
[0044] In this case lightness of the white background of the medium is ca. 92.
[0045] FIG.29B is the graph depicting relations between range of clear vision (axis of abscissa)
and defect width (axis of ordinate) which can not be recognized in a case of compensating
with minimum lightness (ca. 56) in FIG.29A and in a case without compensation.
[0046] A lower portion around origin of coordinate (i.e. lower defect width) in FIG.29B
is enlarged and shown in FIG.29C.
[0047] A recognizable boundary of the defect with width d is plotted in FIG.29C as a curve
with ○ (circle). This curve indicates that when the defect width is ca. 30 µm, the
defect can not be recognized with the boundary value of distance 100cm and when the
defect width is ca. 5µm, the defect can not be recognized with the boundary value
of distance 20cm. In other words, it is concluded that when the defect with ca. 30µm
width is observed apart from more than 100cm, the defect can not be recognized and
when the defect with ca. 5 µm width is observed apart from more than 20cm, the defect
can not be recognized.
[0048] In a case where the defect portion b is recorded with compensating gray color so
as to set the lightness at a predetermined level, the unrecognizable defect with width
d shows a curve with ● (painted circle) as plotted in FIG.29C. This curve with painted
circle indicates that when the defect with ca. 130µm width is observed apart from
more than 100cm, the defect can be hardly recognized, and even when the defect with
ca. 40 µm width is observed apart from more than around 20cm, the defect can be hardly
recognized. Consequently, when the defect is compensated with another color with the
predetermined lightness, the defect portion is much hardly recognized than the case
without compensation.
[0049] From the above-mentioned result, it is concluded that if the lightness of the portion
b is set proper value and is compensate by another color, it is possible to make the
white streak less recognizable.
[0050] The gray color employed in the above-mentioned experiments is formed by mixing C,
M, Y and/or Bk inks, i.e. by the so-called process Bk. When the defect portion b is
compensated by a thinned Bk dot pattern, almost the same results are obtained as the
gray color compensation.
[0051] An example to compensate the defect portion b by the thinned Bk dot pattern is shown
in FIG.30B. A reference numeral "341" in FIG.30B is a thinned Bk dot pattern. Reference
numerals "342" and "343" are examples of compensated defect portion b by thinned Bk
dot patterns.
[0052] The compensated portion b (the thinned Bk dot pattern) bearing no nonuniformity,
of which enlarged pattern shows such a pattern in FIG.30A, is formed and lightness
of a predetermined area of the pattern is measured. When the measured lightness is
compared with the lightness of the portion a, it is concluded that respective lightness
indicate close values to each other as indicated in the case by compensated gray color.
[0053] One of the reasons why Bk dot patterns are employed is that recorded portions with
a high recording duty by another color including a secondary color with low lightness,
can be matched to thinned Bk dot patterns, since the lightness of Bk dot per se is
quite low.
[0054] Hereinafter a method of compensating a defect with width d smaller than 200µm is
explained in detail.
[0055] In the compensating method, one pixel with a resolution of 1200×1200dpi is formed
by using a recording head with a resolution of 1200dpi from which an ink droplet of
ca. 4p1 is ejected and impacted on the coated paper HR101 manufactured by Canon K.K..
[0056] A uniform gradation pattern is formed with C ink so as to generate one non-eject
portion by using non-eject free continuous nozzles and by adjusting an image to be
recorded.
[0057] The non-eject portion is compensated with Bk ink dots.
[0058] As explained below, conditions on which the non-eject portion can not recognized
as nonuniformity when observed from a certain distance, are determined.
[0059] In this method the pattern shown in FIG.31A is recorded. Each grid is recorded such
that it shows a uniform gradation, but with non-eject portions in it.
[0060] Several non-eject portions are scatteringly formed in each grid.
[0061] In FIG.31A, in a vertical direction, gradation expressed in 8bit in each grid is
varied from 0 to 255. And in a horizontal direction, coefficient to determine gradation
of compensating dot in each grid is varied from 0 to 1.2.
[0062] More specifically, when a coefficient value at a position of encircled A in the horizontal
direction is 0.2 and when a gradation value at a position of encircled B is 255, a
calculated gradation of a compensating dot is 255×0.2 = 51.
[0063] Since no nonufiformity is observed in a grid corresponding to the above-calculated
position, it is marked ○ as shown FIG.31B. Grids difficult to judge whether nonuniformity
is observed or not, are marked Δ. Grids where nonuniformity is observed are marked
×.
[0064] FIG.31B is completed when the above-mentioned evaluation procedure is repeated.
[0065] FIG.32 is obtained based on the results of FIG.31B.
[0066] In FIG.32 results marked ○ and Δ are depicted, but results marked × are omitted.
[0067] Actually a compensation curve depicted with a solid line in FIG.32 is obtained based
on a more finely divided grid pattern than the pattern shown in FIG.31A.
[0068] An area formed by two broken line curves sandwiching the solid line curve, indicates
the area where nonuniformity is inconspicuous.
[0069] Drawings shown in FIGs.31A, 31B and 32 are examples of neighbor compensations by
Bk carried out by raising multi-data of the next neighbor nozzles to a non-eject nozzle
1.5 times so that the number of dots from the next neighbor nozzles are raised 1.5
times.
[0070] Alternatively, the evaluation chart in FIG.31B and the compensation curve in FIG.32
can be produced by the following procedure. A similar test pattern to the pattern
in FIG.31A is recorded by a printing apparatus. The recorded pattern is read by a
scanner or a sensor and the like arranged in the printing apparatus. Read pattern
is evaluated so as to form an evaluation chart and a compensation curve respectively
similar to FIG.31B and FIG.32. In this procedure, sensor is defocused so as to adjust
its sensitivity at the same level as human eyes and grids where white streaks or black
streaks are distinctively recognized, are removed and remaining intermediate grids
are selected so as to form a compensation curve similar to that shown in FIG.32.
[0071] Non-eject portions to be recorded by M ink are also compensated by Bk in the same
way as the case of C ink explained in detail above.
[0072] As explained above, it is proved that white streaks due to non-eject statuses can
be compensated by another color having near lightness to that of the original color
and can be hardly recognized as streak nonuniformity, when non-eject widths are sufficiently
narrow against range of clear vision.
[0073] Based on the results of the experiments explained above, when lightness of the compensating
color is set in ± 20% range of lightness of the original color nonuniformity is improved
at least before compensation (on the contrary black steaks do not become more conspicuous).
Preferably, if the lightness of the compensating color is set in ±10% range of lightness
of the original color, the compensated results are remarkably improved.
[0074] In the above-explained examples, non-eject statuses are compensated by Bk ink, but
can be compensated by other inks in the same way as the Bk ink.
[0075] When one non-eject status on the ordinary paper is compensated, multi-data of next
neighbor nozzles are set 1.5 times so as to increase dot numbers recorded by the respective
next neighbor nozzles, in other words neighbor compensation is executed. No streaks
are observed in the paper recorded with 400dpi even without compensation by another
color provided that permeability of the ink is high and the width of defect portions
is ca. 60mµ, since increased ink from neighbor nozzles blots to the non-eject portion.
However, defect portions due to non-eject statuses are not always compensated completely,
when ejected quantities from nozzles and dot diameters are small.
[0076] Taking the above-mentioned points into consideration, the compensation should be
executed by adjusting ejected quantities from nozzles up to a status where nonuniformity
is observed.
[0077] Hereinafter compensation cases when recording is executed on the coated paper with
small blotting rate, i.e. around 2 times, are explained. Since the blotting rate is
small, the compensation by another color is executed.
<Embodiments of Lightness Compensation by Using Bk Ink>
[0078] Hereinafter a method to compensate non-eject nozzles by Bk dots is explained.
[0079] This method is based on adjusted image data such that lightness of image uniformly
recorded by dots for compensation is falls into a predetermined difference range from
lightness of image to be recorded uniformly by non-eject nozzles.
[0080] It is preferable to compensate by a color with similar chromaticity to that of a
color to be compensated. For example non-eject nozzles arranged in a head for cyan
ink can be compensated by magenta or black ink so as to match lightness. However,
boundaries of compensated portions are relatively conspicuous when compensated with
magenta due to a difference in chromaticity between cyan and magenta. Therefore non-eject
cyan nozzles are desirably compensated by Bk dots, if chromaticity is taken into consideration.
Original data on lightness of C nozzles are converted to data on lightness of Bk nozzles
so as to keep converted data within a predetermined lightness difference, and converted
data are added to original data of Bk nozzles and outputted afterward.
[0081] An example of conversion from C to Bk is carried out as follows.
[0082] FIG.4 is the graph showing relations between input data and lightness in respective
inks recorded on a coated paper with a low blotting rate. Axis of abscissa represents
input data in respective colors and axis of coordinate represents lightness in respective
colors.
[0083] From FIG.4, lightness indicates ca. 56, when gradation of C is 192. While in order
to obtain the same lightness value 56 in Bk, inputted gradation should be 56.
[0084] Consequently, from FIG.4, it is concluded that when gradation data on non-eject cyan
nozzles are 192, converted gradation data for black ink indicate 56.
[0085] In this way relations between C, M and Bk used for compensating are plotted in FIG.5.
FIG.5 is the graph showing relations between inputted data corresponding to non-eject
nozzles and converted outputted data for compensation recording. In this drawing a
curve designated by #C_Bk shows a relation of compensating cyan by black ink and another
curve designated by #M_Bk shows a relation of compensating magenta by Bk ink. When
defect portions caused by non-eject cyan or magenta are compensated by black ink,
a table as shown in FIG.5 is used so that influence by a non-eject color is reduced
by outputting added converted Bk data corresponding to defect portions to the original
Bk data. The lightness of Y against paper does not vary so much when its gradation
is varied. In other words, since yellow is a quiet color, it is not necessary to compensate
by another color. A curve designated by #Bk_cmy shows a relation of compensating Bk
by three colors C, M and Y. Non-eject portions of Bk can be compensated by using C,
M and Y.
<Compensation by Head Shading>
[0086] Hereinafter a method to make defect portions inconspicuous by a head shading treatment
is explained. The head shading is a technique to compensate density nonuniformity
mainly generated by fluctuating ejecting properties of respective plurality of nozzles,
and to make density nonuniformity inconspicuous by determining correcting data to
respective nozzles for equalizing densities. More specifically, a tentatively recorded
image is read by a scanner and correction data are determined for raising densities
corresponding nozzles to low density portions in the read image or lowering densities
corresponding nozzles to high density portions in the read image, thus densities are
equalized.
[0087] By executing the head shading treatment, corrections are made on areas corresponding
to non-eject portions (defect portions) in the original image such that recording
duties of at least neighboring peripheral pixels around the areas are raised, thus
non-eject portions are made inconspicuous.
[0088] The head shading is the method for removing nonuniformity by modifying output γ values
(which will be explained in detail below) of respective nozzles according to density
nonuniformity in a read test pattern recorded by the recording head. In ordinary resolution
range from 400dpi to 600dpi, read data on density nonuniformity are corrected in such
manner that an averaged density calculated from that of a present nozzle and of its
neighbor nozzles is considered as the corrected density of the present nozzle.
[0089] Since recorded densities corresponding to next neighbor nozzles to the non-eject
nozzle are lowered, data of next neighbor nozzles are corrected so as to raise their
densities by the head shading treatment.
[0090] The corrected dot number in a surrounding area of a pixel corresponding to the non-eject
nozzle is raised to the similar dot number to a case without non-eject nozzles, as
a result nonuniformity can not be recognized.
[0091] FIGs.3A to 3E are schematic drawings showing data correcting manners of neighbor
nozzles to the non-eject nozzle by the head shading treatment.
[0092] Four dots are recorded in respective grids shown in FIGs.3A to 3D, when recorded
with 100% recording duty. On the other hand, in respective grids shown in FIG.3E two
dots are recorded, when recorded with 100% recording duty. Nozzles are arrayed in
vertical directions in these respective drawings. An arrow "A" in respective drawings
indicates a position not recorded due to the non-eject nozzle.
[0093] FIG.3A shows a schematic image to be recorded with 1/4 recording duty, where data
on neighbor nozzles to the non-eject nozzle are corrected to raise their density so
that the dot number to be recorded are increased by the shading treatment. FIG.3E
shows a schematic image to be recorded with 1/8 recording duty. In low recording duties
as mentioned above, streaks caused by non-eject nozzles are inconspicuous so that
there are no significant differences between observed densities of corrected dot images
and densities of images recorded by a normal recording head due to the increased dot
number recorded by neighbor nozzles.
[0094] FIG.3B shows a schematic image to be recorded with 1/2 (50%) recording duty and FIG.3C
shows a schematic image to be recorded with 3/4 (75%) recording duty. Since the duty
of the image shown in FIG.3C is set high, density corresponding to the non-eject nozzle
can not be reproduced only by neighbor nozzles, so that data on second neighbor nozzles
are corrected to raise their density.
[0095] As shown in FIGs.3B and 3C, as dot densities to be recorded are raised, defect portions
corresponding to non-eject nozzles (indicated by the arrow A) become gradually conspicuous
as streaks.
[0096] Therefore the above-mentioned head shading treatment can effectively suppress density
drops caused by defects in images due to non-eject statuses, when image areas with
low duties are treated.
[0097] FIG.3F shows an example of γ correction to neighbor nozzles to the non-eject nozzle
judged by the head shading treatment. Reference character "4a" is a gradient with
no correction. Reference character "4b" is a gradient to raise the density 1.5 times
by the γ correction. γ corrections against neighbor nozzles to the non-eject nozzle
can be executed so as to raise the densities 1.5 times at the maximum.
[0098] As described above, in low recording duties the dot number in the vicinity of the
non-eject nozzle is almost similar to that of the surrounding area when the uniform
pattern is recorded. Even in high recording duties, when dots with a large diameter
are recorded on a medium with a high blotting rate, recorded dots are blotted to non-eject
area so that nonuniformity can hardly be conspicuous.
[0099] Hereinafter, another recording example on the coated paper with a low blotting rate
of about 2 times is explained. Since the blotting rate is low, the compensation by
another color and the head shading treatment are executed together.
<Combination of Lightness compensation with Head Shading Treatment>
[0100] Here the above-mentioned two combined compensation methods are employed. Namely non-eject
portions are compensated by using another color and next neighbor nozzles to the non-eject
portions.
[0101] Hereinafter a more effective arrangement to make defects in images caused by non-eject
nozzles is explained by combining the method to compensate the defects with another
color by adjusting its lightness with the head shading treatment.
[0102] It is preferable to adjust properly the above-mentioned respective compensation method
in order to optimize the combined compensation method. As described above, in areas
with low recording duties, the dot number in the vicinity of the pixel corresponding
to non-eject nozzle and neighbor nozzles is almost similar to the dot number of the
case without non-eject nozzle, the vicinity of the pixel can not be recognized as
nonuniformity by the head shading treatment (see FIG.3A and FIG.3E).
[0103] However, in the head shading treatment when a solid area image is recorded with a
high recording duty on a medium with low blotting rate, portions corresponding to
non-eject nozzles tend to be white streaks and recognized as streaky nonuniformity.
Therefore when recorded with low recording duty, non-eject portions should be compensated
by the head shading treatment and when recorded with high recording duty non-eject
portions should be additionally compensated by another color so that defect portions
in the recorded image due to non-eject nozzles are suppressed regardless of differences
of recording duties.
[0104] FIG.3F shows a compensation example constituted by combining the head shading treatment
with the compensation with another color. Neighbor nozzles to the non-eject nozzle
are compensated according to the line 4b in FIG.3F, and if a recording duty is high,
defect portions corresponding to non-eject nozzle are compensated by another color.
The line 4b shows a γ compensation which raises image density up to 1.5 times. When
the recording duty of image data exceed 2/3 (67%), image data corresponding to another
color are generated according to a line 4c in FIG.3F. Thus, when recording duty is
lower than 2/3, defect portions caused by non-eject statuses are made inconspicuous
by raising image density in areas corresponding to neighbor nozzles to non-eject nozzle,
and when recording duty is higher than 2/3, compensation recording can be executed
by another color so as to match lightness of non-eject portions to that of another
color.
[0105] Hereinafter, based on compensation by the above-mentioned methods, a compensation
procedure by an ink-jet recording apparatus is explained in detail.
[0106] The present invention can be executed by a printer having a function of scanner or
a printer capable of inputting density nonuniformity and data read from the pattern
for measuring non-eject nozzles. Here, however, the compensation procedure is explained
in the case of a color copy machine equipped with an ink-jet method capable of reading
and recording color images.
(First Embodiment)
[0107] Hereinafter, a case, where the coated paper with small blotting rate is identified
by the color copying machine, is explained.
<Method Combined with Lightness compensation with Bk Compensation>
[0108] The present embodiment is intended to compensate non-eject nozzles by using another
color, particularly black (Bk) against cyan (C) and magenta (M) so as to match lightness
of another color to that of non-eject color based on image data corresponding to non-eject
nozzles.
[0109] Hereinafter the preferred embodiment is explained by referring to drawings.
[0110] FIG.9 is the side sectional view illustrating arrangement of the color copying machine
employing the ink-jet recording apparatus by the present embodiment.
[0111] This color copying machine is constituted by an image reading and an image processing
unit (hereinafter referred as a reader unit 24) and a printer unit 44. The reader
unit 24 reads an image script 2 mounted on a script glass 1 via a CCD line censor
5 having three color filters, R, G and B as being scanned. The read image is processed
by an image processing circuit and processed image is recorded on a paper or other
recording media (hereinafter also referred as recording paper) by printer unit 44,
namely by four color ink-jet heads, cyan (C), magenta (M), yellow (Y) and black (Bk).
[0112] Image data from outside can be inputted, and inputted data are processed by the image
processing unit and recorded by printer unit 44.
[0113] Hereinafter, operational movements of the apparatus are explained in detail.
[0114] The reader unit 24 is consisted by members or portions 1 to 23 and the printer unit
is consisted by members or portions 25 to 43. A left upper side in FIG.9 corresponds
to a front face of the machine, to which an operator faces.
[0115] The printer unit 44 is equipped with an ink-jet head (hereinafter also referred as
a recording head) 32, which executes recording operations by ejecting inks. In the
ink-jet head 32, for example, 128 nozzles for ejecting inks are arrayed and eject
ports are formed at ejecting sides of nozzles. 128 eject ports are arranged in a predetermined
direction (in a sub-scanning direction, which will be explained below) with a 63.5
µm pitch so that the recording head can record a width of 8.128mm. Consequently when
the recording paper is recorded, once a feeding operation (feeding in the sub-direction)
of the recording paper is stopped and then the recording head 32 is moved in a perpendicular
direction to FIG.9 as the feeding operation being stopped. After the recording head
records a desired distance with the width of 8.128mm, the recording paper is fed by
8.128mm and stopped and, then the recording head starts recording. Thus, feeding operations
and recording operations are alternatively repeated. The recording direction is called
a main scanning direction and the paper feeding direction is called the sub-scanning
direction.
[0116] In the constitution by the present embodiment, the main scanning direction corresponds
to the perpendicular direction to the plane of FIG.9 and the sub-scanning direction
corresponds to the right/left directions in FIG.9,
[0117] The reader unit 24 repeats reading the script image 2 by the width of 8.128mm in
response to the movements of the printer unit 44. Here a reading direction is called
a main scanning direction and a feeding direction of the script image for the next
reading is called a sub-scanning direction. In the present constitution, the main
direction corresponds to the right/left directions in FIG.9 and the sub-scanning direction
corresponds to the perpendicular direction to the plane of FIG.9.
[0118] Hereinafter, operational movements of the reader unit are explained.
[0119] The script image 2 on the script mount glass 1 is irradiated by a lamp 3 mounted
on a main scanning carriage 7, and irradiated image is led to CCD line sensor 5 (photo
sensor) via a lens array 4. The main scanning carriage 7 is fitted to a main scanning
rail 8 mounted on a sub-scanning unit 9 so as to slide along the rail. The main scanning
carriage 7 is connected to a main scanning belt 17 via a connecting member (not shown)
so that it moves in the left/right directions in FIG.9 by rotating a main scanning
motor 16 for executing main scanning operations.
[0120] The sub-scanning unit 9 is fitted to a sub-scanning rail 11 fixed to an optical frame
10 so as to slide along the rail. The sub-scanning unit 9 is connected to a sub-scanning
belt 18 via a connecting member (not shown) so that it moves in the perpendicular
direction to the plane of FIG.9 by rotating a sub-scanning motor 19 for executing
main scanning operations.
[0121] Image signals read by CCD line sensor 5 are transmitted to the sub-scanning unit
9 via a flexible signal cable 13 capable of being bent in a loop. One end of the signal
cable 13 is held (bitten) by a holder 14 on the main scanning carriage 7. Another
end of the signal cable is fixed to a bottom surface 20 of the sub-scanning unit by
a member 21 and is connected to a sub-scanning signal cable 23 which connects the
sub-scanning unit 9 to an electrical component unit 26 of the printer unit 44. The
signal cable 13 follows movements of the main scanning carriage 7 and the sub-scanning
signal cable 23 follows movements of the sub-scanning unit 9.
[0122] FIG.10 is a detailed drawing of CCD line sensor 5 by the present embodiment. The
line sensor 5 consists of 498 photo cells arrayed in a line and can read actually
166 pixels since each pixel requires three color elements, R, G and B. Among 166 pixels,
the effective number of pixels is 144, which corresponds to a width of ca. 9mm.
[0123] Hereinafter operational movements of the printer unit 44 are explained.
[0124] A recording paper sent from a recording paper cassette 25 one by one by to a supply
roller 27 driven by a power source (not shown), is recorded by a recording head 32
between two pairs of rollers, 28, 29 and 30, 31. The recording head is monolithically
formed with an ink tank 33 and demountably mounted on a printer main scanning carriage
34. The printer main scanning carriage 34 is fitted to a printer main scanning rail
35 so as to slide along the rail.
[0125] Further, since the printer main scanning carriage 34 is communicated to a main scanning
belt 36 via a connecting member (not shown), the carriage is moved to perpendicular
directions to the plane of FIG.9 by rotating a main scanning motor 37 so that the
main scanning is executed.
[0126] The printer main scanning carriage 34 has an arm member 38, to which a signal cable
39 for transmitting signals to the recording head 32 is fixed. Another end of the
signal cable 39 is fixed to a printer intermediate plate 40 by a member 41 and further
connected to the electric component unit 26. The printer signal cable 39 follows movements
of the printer main scanning carriage 34 and is arranged such that the cable does
not contact with the optical frame arranged above.
[0127] The sub-scanning of the printer unit 44 is executed by rotating the two pairs of
rollers, 28, 29 and 30, 31 driven by the power source (not shown) so that the recording
paper is fed by 8.128mm. A reference numeral "42" is a bottom plate of the printer
unit 44. A reference numeral "45" is an outer casing. A reference numeral "46" is
a pressure plate for pressing the image script against the image script mounting glass
1. A reference numeral "1009" is a paper discharging opening (see FIG.22), A reference
numeral "47" is a discharged paper tray and a reference numeral "48" is an electrical
component unit 48 for operating the copy machine.
[0128] FIG.11 is the perspective view illustrating an external appearance of an ink cartridge
arranged in the printer unit 44 of the present embodiment. FIG.12 is the perspective
view illustrating the printed circuit board 85 shown in FIG.11 in detail.
[0129] In FIG.12, a reference numeral "85" is the print circuit board. A reference numeral
"852" is an aluminum radiator plate. A reference numeral "853" is a heater board consisting
of a matrix of heating elements and diodes. A reference numeral "854" is a memory
means where information on respective nozzles is stored. For the memory means a nonvolatile
memory such as EEPROM and the like, is employable in accordance with situations.
[0130] In the present embodiment, information whether respective nozzles are non-eject nozzle
or not is stored, but it is possible to store other information such as density nonuniformity
and the like.
[0131] A reference numeral "855" is a contact electrode connected to the printer unit of
the copying machine. Arrayed nozzle groups are not shown in FIGs.11 and 12.
[0132] When the recording head is mounted to the printer unit of the copying machine, the
printer unit reads information on non-eject nozzles from the recording head 32 and
controls the recording head based on the read information so as to improve density
nonuniformity. Thus good image quality can be maintained
[0133] FIGs.13A and 13B show arrangement examples of main portions of a circuit on the printed
circuit board 85 shown in FIG.12. FIG.13A shows a circuit arrangement of the heater
board 853, which consists of an N × M matrix structure where respective heating elements
857 and respective diodes 856 for preventing rounded electric current are connected
each other in series. These heating elements 857 allocated into N blocks and each
block consists of M heating elements. Respective blocks are activated one after another
according to a time sharing schedule as shown in FIG.14. Quantities of energy to activate
respective block are controlled by varying applied pulse widths (T) to the segment
side (in FIG.13A referred as Seg).
[0134] FIG.13B shows an example of the EEPROM 854 shown in FIG.12. In the present embodiment,
information on non-eject nozzles is stored in the EEPROM and outputted to the image
processing unit of the copying machine.
[0135] An example of constitution of the image processing unit in the present embodiment
is shown in FIG.17.
[0136] In FIG.17, image signals read by the CCD sensor 5 as one of solid state image sensors,
are corrected their sensor sensitivities by a shading correction circuit 91. Corrected
three primary colors of light, R (Red), G (Green) and B (Blue) are converted to colors
for recording, C (cyan), M (Magenta), Y (Yellow) and Bk (Black) by a color conversion
circuit 92.
[0137] Usually the color conversion is executed by utilizing a three dimensional LUT (Look
Up Table), but not limited to the LUT. It is also applicable to colors for recording
comprising low density LC (Light Cyan), LM (Light Magenta) and the like in addition
to C, M, Y and Bk.
[0138] Image data acquired outside can be directly inputted to the color conversion circuit
92 and be processed there.
[0139] C, M, Y and Bk signals converted from RGB signals are inputted to a data conversion
unit 94. Inputted signals are converted as mentioned below by utilizing the information
on non-eject nozzles stored in the memory means arranged in the ink-jet recording
head or information acquired by calculation based on measured data of non-eject nozzles,
and supplied to a γ conversion circuit 95. Properties on respective nozzles used here
are stored in a memory of the data conversion unit 94.
[0140] The γ conversion circuit 95 stores several staged functions, for example, as shown
in FIG,18 for calculating output data from input data. Stored functions are properly
selected based on density balances in respective colors and color taste of users.
These functions are also determined based on properties of inks and recording papers.
The γ conversion circuit 95 can be incorporated into the color conversion circuit
92. Output data from the γ conversion circuit are transmitted to a conversion to binary
data circuit 96.
[0141] In the present embodiment, an error diffusion method (ED) is employed for converting
transmitted data to binary data.
[0142] Outputted data from the conversion circuit 96 to binary data 96 are transmitted to
the printer unit and recorded by the recording head 32.
[0143] The present embodiment utilizes the conversion circuit to binary data for outputting
image data, but not limited to this conversion circuit. For example a conversion circuit
to tertiary data for utilizing large/small dots or a conversion circuit to n+1th data
for utilizing 0 to n dots can be also selected depending on various outputting methods.
[0144] Hereinafter a non-eject nozzle/density nonuniformity measuring unit 93 and a data
conversion unit 94, which constitute a data processing unit 100, are explained.
[0145] FIG.19 is the block diagram showing a constitution of main portions of the data processing
unit 100 in FIG.17, where portions surrounded by broken lines are respectively the
non-eject nozzle/density nonuniformity measuring unit 93 and the data conversion unit
94.
[0146] To begin with, detailed functions of the non-eject nozzle/density nonuniformity measuring
unit 93, are explained.
[0147] In this unit, if information on non-eject nozzles is required to be renewed, operations
for printing the non-eject/nonuniformity pattern, reading printed pattern and processing
data are executed. If information on non-eject/onuniformity is not required to be
renewed, the above-mentioned operations can be omitted.
[0148] In the present embodiment, corrections on density nonuniformity are not executed,
but the non-eject nozzle/density nonuniformity measuring unit 93 can acquire information
on the density nonuniformity. However, the acquired information is used in other embodiments,
operations for acquiring the information is also explained.
[0149] When the information on non-eject nozzles is renewed, a recovery operation of the
recording head is executed prior to printing the non-eject/nonuniformity pattern for
reading. The recovery operation consisting of a series procedures for removing stuck
ink to the recording head 31, for removing bubbles by sucking ink from nozzles and
for cooling head heaters, is very desirable as a preparing operation for printing
the non-eject/nonuniformity pattern for reading on best conditions.
[0150] Then the non-eject/nonuniformity pattern for reading shown in FIG.23 is outputted
as a recorded pattern. In the recorded pattern four rows of respective color blocks
are recorded at 50% half tone in a vertical direction in FIG.23, as a result 16 blocks
are recorded in total. The patterns are recorded at predetermined positions on the
recording paper. Each block consists of 3 lines of recording where the first and third
lines are recorded by using uppermost and lowermost 16 nozzles respectively and the
second line is recorded by using 128 nozzles, consequently each recorded block at
the half tone has a width corresponding to 160 nozzles. Reasons for recording each
block with the width corresponding to 160 nozzles are as follows.
[0151] As shown in FIG.24, when the pattern recorded by the recording head 32 consisting
of for example 128 nozzles, is read the CCD sensor 5 and the like, density data An
tend to be blunted by the influence of a background color (for example white) of the
recording paper. Consequently, if each block is recorded with only 128 eject ports,
there are possibilities to lose reliabilities in density data of eject ports at both
sides of the recording head. In this embodiment, so as to avoid such possibilities,
the pattern is recorded with 160 eject ports and density data having values more than
a predetermined threshold value are treated as effective data. An eject port corresponding
to one density data in the center of the effective data is considered as the center
eject port. Density data positioned, the total eject port number)/2 (= 64 in this
case) apart from the center to right/left, are considered data corresponding to the
first eject port and 128th eject port respectively.
[0152] The nozzle number employed for recording first and third line of each block is not
always limited to 16. In this embodiment, in order to save data storing memory the
nozzle number is decided as 16.
[0153] After the non-eject/nonuniformity pattern for reading is recorded, as shown in FIG.22
an outputted recording paper 2 is placed on the script glass 1 as recorded surface
being faced downward so as to align recorded 4 blocked color rows in the main scanning
direction of the CCD sensor 5. Then a reading operation to read recorded pattern is
started.
[0154] Prior to reading the non-eject/nonuniformity pattern for reading, a shading treatment
against the CCD sensor 5 is executed by using a standard white plate 1002 shown in
FIG.22. Here "one line" is defined as one main scanning over 4 blocked color rows.
When one line is read, read density data corresponding to 4 blocked, for example,
black pattern are stored in an SRAM (see FIG.23). Respective color blocks are recorded
at predetermined positions so that read data (density data) on respective 4 blocked
colors are stored in a predetermined area of the SRAM. A profile of the read data
usually shows a curve shown in FIG.25A. In the figure, a horizontal direction represents
an SRAM address and a vertical direction represents density. As mentioned above, the
recorded area is defined as an area with a density more than the determined density
level (threshold). Here an address X1 corresponding to a first address of which density
exceeds the threshold value, is checked whether the address is in an allowable range.
In the same way an address corresponding to a last address of which density exceeds
the threshold value, is defined as "X2". When a starting address of reading is defined
as "X", whether X1 is in a range of X± Δ x or not, is checked and also whether data
corresponding to addresses is in a range of X1 + 160± Δ x or not, is checked.
[0155] When conditions mentioned above are not fulfilled, the reading operation is judged
as an error caused possibly by placing the pattern for reading obliquely. The reading
operation is executed again or read data are checked again after a rotating calculation
is executed on the read data. Thus, respective density data are matched to corresponding
nozzles. Density data for each pixel in a range from X1 to X2, which is judged as
the recorded area, is checked whether the density exceeds a threshold value for judging
a non-eject nozzle, or not.
[0156] When only one nozzle is judged as the non-eject nozzle as shown in FIG.25C, usually
the density of the judged nozzle is not lowered to the level of the background color
of the recording paper. Taking this fact into consideration, the threshold value for
judging the non-eject nozzle is set separately and when data in the recording area
have lower values than the threshold value, corresponding nozzles are judged as non-eject
nozzles.
[0157] When the recording head is in unstable statuses, sometimes eject ports are brought
to non-eject statuses abruptly.
[0158] For example, when non-eject statuses occur in four recording patterns shown in FIG.23,
it is judged as a perfect non-eject status. If there are no non-eject statuses except
in one area, the non-eject statuses are judged as unexpected ones, which may be excluded
for calculation, or judged as an error and the recording operation may start again,
instead. The threshold value for judging the non-eject status is not necessary to
set separately, but if the threshold value for judging the recorded area is set at
higher level a little bit both non-eject statuses and the recorded area can be checked
simultaneously.
[0159] Processed data in the above-mentioned way are inputted to a non-eject/nonuniformity
calculating circuit 135 (in FIG.19).
[0160] Calculations in the present embodiment are executed to determine non-eject nozzles,
calculations to determine density ratio for correcting nonuniformity are also explained.
[0161] After data in the form of a curve shown in FIG.25C are inputted, succeeding procedures
are explained by referring to FIG.26. An average value of data at both sides, X1 and
X2 is calculated and a center value of the recording area is determined. The determined
center is judged as a space between 64th and 65th nozzles. Therefore 64th pixels from
the center to the right/left correspond to respectively the first nozzle and the 128th
nozzle. Thus recording densities n(i) for respective nozzles including connecting
nozzles to both side nozzles. When recording densities n(i) for respective nozzles
are lower than the threshold value for detecting non-eject nozzle, corresponding nozzles
are determined as non-eject nozzles and density ratio information of the determined
nozzles is set as d(i) = 0. Since calculations on the density ratio are not executed
in the present embodiment, density ratio information on remaining nozzles are set
as d(i) = 1.
[0162] The density ratio information can be determined as follows.
[0163] An average value AVE of total nozzles except non-eject nozzles is calculated and
density ratio d(i) for respective nozzles is defined as d(i) = n(i)/AVE.
[0164] It is not desirable to use density data corresponding to an area with one pixel width
as it is. Because, as shown in FIG.27, a read area corresponding to one pixel certainly
includes densities from dots ejected from nozzles at both sides and it is natural
any nozzle deviates a little toward a right or left nozzle. In addition when calculations
are executed, the following point should be considered that density nonuniformity
of a pixel observed with human eyes is influenced by surrounding conditions around
the pixel.
[0165] For that purpose, before determining densities of respective nozzles, averaged density
data of one pixel and both next neighbor pixels (A
i-1, A
i, A
i+1) as shown in FIG.8 are successively calculated and the averaged value is defined
as a nozzle density ave(i). It is desirable to modify the density ratio information
into d(i) = ave(i)/AVE. Correction tables being mentioned below are formed by using
the modified density ratio information.
[0166] The density ratio information is processed by a correction table calculating circuit
136 (see FIG.19) so that correction tables for respective nozzles are determined.
[0167] When a correction table number is defined T(i), the following equations are obtained.
Here 64 correction tables #0 to #63 are prepared as shown in FIG.20, where each table
is plotted as its gradient gradually increasing/decreasing from center table #32.
[0168] Table #32 has a gradient 1 so that inputted values and outputted values are always
equal. FIG.20 includes tables for determining average densities of 128 eject ports.
The density of table #32 is set 50%(80H) equal to the density of recording sample.
Densities of other table numbers are varied 1% by 1% from the center table #32.
[0169] Accordingly, T(i) obtained by the above-described equations indicate converted signal
values corresponding to density ratios when signals are always inputted with 80H density.
#0 corresponds to the non-eject nozzles where all output data are set 0 (zero).
[0170] When all 128 T(i) are calculated, calculations on correction table numbers for one
line are finished.
[0171] However, since calculations to determine density ratios are not executed in the present
embodiment, determined density values to all nozzles are #0 or #32.
[0172] Operations for reading non-eject nozzles and nonuniformity and based on read data
calculations for determining corrected correction table numbers are finished for one
line, namely, for one color. The same operations and calculations are repeated in
other remaining three colors. When correction table numbers for 4 colors are completed,
data stored in a correction table number storing unit 137 (see FIG.19) are renewed.
Old correction table numbers in this storing unit read from stored information 854
in the recording head functioning as a memory means, and stored information 854 are
rewritten.
[0173] When a detecting operation to detect non-eject nozzle/nonuniformity is not executed,
correction table numbers stored in stored information 854 are utilized in succeeding
operations.
[0174] A data conversion circuit 138 (in FIG.19) converts outputted image signals to signals
for respective heads by utilizing correction tables for respective nozzles. The flow
chart of this conversion is illustrated in FIG.8.
[0175] Image signals on C, M, Y and Bk inputted to the data conversion unit 94, are associated
with identified corresponding nozzles (step S2001). If recording operations continue,
respective color data constituting the same pixel are selected and processed together.
[0176] Here correction tables for respective nozzles are read (step S2002), and converted
afterward. On the whole the conversion procedure consists of two cases, a case where
the correction table corresponds to any one from #1 to #63 and a case where the correction
table corresponds to #0, i.e. a non-eject case (step S2003).
[0177] When the correction table corresponds to any one of #1 to #63, inputted data are
transmitted to respective color data adding units without processing (step S2005).
[0178] On the other hand when the correction table corresponds to #0, i.e. corresponds to
a non-eject nozzle, compensation data for compensating the correction table is generated
(step S2004), When inputted signals correspond to C, the correction table #C_Bk is
selected, and when inputted signals correspond to M, the correction table #M_Bk is
selected so as to generate Bk data. When inputted signals correspond to Y, Bk data
is not generated. And when inputted signals correspond to Bk, the correction table
#Bk_cmy is selected for generating respective C, M and Y data.
[0179] In this embodiment, compensation data are generated such that lightness of the original
color indicates nearly the same value as that of compensating color, as mentioned
above. FIG.4 is the graph showing the relation between inputted values of respective
colors and corresponding outputted lightness. Compensation tables are made based on
this figure. For example when input data of cyan (C) is 192 (inputted on 8bit basis),
its lightness indicates ca. 56.
[0180] While in black (Bk), when its lightness indicates ca. 56, inputted data on 8 bit
basis is ca. 56 (Bk = 56), consequently, C = 192 is converted to Bk = 56. A compensation
table (#M_Bk) for magenta (M) compensated by black (Bk) obtained in the same way as
mentioned above, as well as the compensation table for C (#C_Bk) are plotted in FIG.5.
[0181] Compensations against yellow (C) are not executed particularly, since yellow (C)
always shows high lightness. Compensation against black Bk is made by respective colors
C, M and Y in the same ratio. The compensation table for Bk (#Bk_cmy) is also plotted
in FIG.5.
[0182] Compensation data are formed by utilizing these compensation tables. Actually, however,
relations between dot diameters to be recorded and pixel pitches should also be considered.
In the present embodiment, for example, a dot diameter to be recorded is ca. 95 µm
and a pixel pitch is 63.5 µm. Which means that an area factor of 100% can obtained,
even when impacted dot recorded with 100% recording duty is deviated a little bit.
[0183] Accordingly, it can be concluded that, for example, when only one nozzle is in the
non-eject status, influences from dots of neighbor pixels on the non-eject pixel are
fairly significant.
[0184] In other words, a compensated dot recorded on a non-eject portion influences neighbor
pixels not a little.
[0185] This is also expressed as follows: when non-eject nozzles are not continued, a lower
compensation data than the obtained data from the relation in lightness can applicable.
[0186] Consequently, compensation tables shown in FIG.6 are employed in the present embodiment.
[0187] Generated compensation data of respective colors in the above-mentioned ways are
transmitted to a data adding unit (step S2005).
[0188] The data adding unit has a function for holding respective color data and a calculating
function. If compensation data is inputted to this unit in the first place, data is
kept as it is. If other data are already kept, inputted data are added. If added results
exceed 255 (FFH), they are kept as 255. In the present embodiment, simple adding procedures
are employed, but other calculating methods and tables may be utilized, if necessary.
[0189] After adding procedures to all colors C, M, Y and Bk, are finished, added results
are transmitted to a data correction unit and data kept in the data adding unit is
reset so as to wait for processing the next pixel. Data transmitted to the data correction
unit are converted according to correction tables (#0 to #63) (step S2006). Thus a
series data conversion procedures are finished.
[0190] Converted data in the above-mentioned way are transmitted via a γ conversion circuit
95, a conversion circuit to binary data 96 (see FIG. 17) and so forth and outputted
as images.
[0191] When images outputted in this way are intently observed from a close distance, non-eject
portions can be recognized, but image quality is excellent on the whole.
<Processing Examples by Head Shading>
[0192] Among a series operations of the head shading, i.e. nonuniformity compensations,
compensations against non-eject nozzles are executed. Hereinafter compensation procedures
are explained more specifically.
[0193] The present embodiment is executed in the same system as mentioned above. Different
features from the previous examples are: (1) corrections to nonuniformity are executed
and (2) correction data by other colors are not generated in the present example.
[0194] Hereinafter data conversions, namely, processing operations by the non-eject nozzle/density
nonuniformity measuring unit 93 and the data conversion unit 94 (in FIG.17), mainly
on the two features (1) and (2), are explained.
[0195] Processing operations by the non-eject nozzle/density nonuniformity measuring unit
93, are basically the same as the previous example as shown in FIG.18. As shown in
the block diagram in FIG.19, at first the non-eject/nonuniformity pattern for reading
is recorded. The recorded pattern is read by employing the CCD sensor. The read data
are processed such as adding calculations, averaging calculations and the like so
that density n(i) to be recorded corresponding to respective nozzles as shown in FIG.26
is obtained.
[0196] Fundamental factors to generate nonuniformity are explained for more easily understanding
the present example.
[0197] FIG.15A is the schematic view showing the enlarged recording status recorded by an
ideal recording head 32. In the figure, a reference numeral "61" is ink eject ports
arranged in the recording head 32. When recorded by the recording head 32, ink spots
60 with uniform drop diameter (liquid droplet diameter) are recorded in arrayed state
on the recording paper.
[0198] The schematic drawing in the figure is an example recorded with so called full ejection
(all eject ports are activated). However, even when recorded with a half tone of 50%
ejection, nonuniformity is not generated in this case.
[0199] On the other hand, in a case shown in FIG.15B, diameters of drops 62 and 63 ejected
from second and (n― 2)th eject ports are smaller than the other, and drops from (n
- 2)th and (n - 1)th eject ports are recorded on positions deviated from ideal positions.
More specifically, drops from (n - 2)th eject port are recorded at right-upward positions
from ideal centers and drops from (n - 1)th are recorded at left-downward positions
from ideal centers.
[0200] Area A indicated in FIG.15B appears as a thin streak on a recorded image. Area B
also result in a thin streak, because a distance between centers of drops from (n
- 1)th and (n - 2)th eject ports is larger than an average distance l
0 between two neighbor drops. On the other hand, area C appears a thicker streak than
other areas because a distance between centers of drops from (n - 1)th and nth eject
ports is smaller than the average distance I
0 between two neighbor drops.
[0201] As mentioned above, density nonuniformity appears mainly due to dispersed drop diameters
and deviated drops from centers (usually called as the twisted state).
[0202] As a means to cope with the density nonuniformity, it is effective to employ the
following method such that image density of a certain area is detected and quantity
of ink to be ejected to that area is controlled based on the detected image density.
[0203] The density nonuniformity, caused by dispersed drop diameters or twisted states as
shown in FIG.16B compared with a recorded image by the ideal recording head recorded
with a 50% half tone as shown in FIG.16A, can be made inconspicuous, in the following
way. For example, when summed dot areas existing in area a surrounded by a broken
square in FIG.16B, is adjusted so as to near to summed dot area a surrounded by a
broken square in FIG.16A, even an image by recorded by a recording head having characteristics
as shown in FIG.16B is judged by human eyes that the recorded image has the same density
as that of the image in FIG.16A.
[0204] In the same way an area b shown in FIG.16B can be adjusted so as to remove the density
nonuniformity.
[0205] FIG.16B illustrates adjusted density compensation results in a model form for explaining
simply. Reference characters " α "and " β " represent dots for compensation.
[0206] This system can be applied to non-eject nozzles, when drop diameters from non-eject
nozzles are set nearly zero.
[0207] In this respect, modified density ratio data D(i) for respective nozzles in the previous
example defined as follows are important.
Here ave(i) is a density obtained by averaged densities of three successive nozzles
(n(i- 1), n(i), n(i+1)), namely.
And AVE is defined as follows.
When a i
0th nozzle is a non-eject nozzle, it is set that n(i
0) = d(i
0) = 0. Consequently, effective density of both neighbor (i
0+1)th (i
0 - 1)th nozzles, i.e., ave(i
0+1) and ave(i
0 - 1), respectively indicate much smaller values than (n(i
0 - 1) and n(i
0+1). As a result, since density ratio information d(i
0+1) and d(i
0 - 1) become virtually smaller, higher density output values are set by a compensation
table being mentioned below so as to compensate non-eject nozzles. Therefore effective
density ave(i) for respective nozzles are not limited to simply averaged values, but
properly weighted averaged values, for example, ave(i) = (2n(i- 1) + n(i) + 2n(i +
1))/5 and the like can be employed.
[0208] The density ratio information d(i) obtained in the above mentioned way is processed
by a correction table calculating circuit 136 (see FIG.19) of the data conversion
unit 94 so that correction tables for respective nozzles are determined. Since this
processing procedure is the same as the previous embodiment, further explanations
are omitted.
[0209] 64 density correction tables are depicted in FIG.20, but correction tables are increased
or decreased in accordance with required conditions. Non-linear correction tables
as shown in FIG.21, for example, can be also employed in accordance with properties
of media to be recorded and inks.
[0210] After correction tables for all nozzles are determined, contents in a correction
table number storing unit 137 and stored information on recording head 854 are renewed
(see FIG.19). Data conversion on an image to be outputted is executed by a data conversion
circuit 138 by utilizing the determined correction tables. In this case data are converted
in the same way as the previous example, but simpler, since compensations by other
colors are not executed.
[0211] A flow chart for the present case is similar to the flow chart shown FIG.8, but the
following steps are omitted; correction table identifying step (S2003), generating
different color data (step S2004) and data adding step (S2005). Compensated data are
transmitted to a γ conversion circuit 95, if required, then converted to binary data
by a conversion circuit 96 to binary data and outputted as images.
[0212] Images obtained in the above-mentioned way are excellent in such a manner that effects
by non-eject statuses are hardly observed particularly in highlighted portions.
[0213] However, white streaks caused by non-eject statuses are not always compensated in
portions recorded with high duty.
(Second Embodiment)
[0214] In the present embodiment, examples where the coated papers with blotting rate around
2.0 are employed, are explained.
<Head Shading and compensation with different colors>
[0215] Since the present embodiment is an embodiment where compensations of non-eject statuses
by different colors and by the head shading are combined, the compensation can be
executed by the same system employed in the head shading of the first embodiment.
[0216] Hereinafter data conversion processes by the present embodiment are explained.
[0217] The non-eject nozzle/density nonuniformity measuring unit 83 shown in FIGs.17 and
19, executes the same operations as the first embodiment, more specifically, the operation
to record non-eject/nonuniformity pattern for reading, the operation to detect non-eject
nozzles, the operation to calculate recording densities for respective nozzles and
the operation to calculate the density ratio information of respective nozzles are
executed.
[0218] The calculated density ratio information is processed by the correction table calculating
circuit 136 in the data conversion unit 94 in the same as the first embodiment and
correction tables for respective nozzles are determined. The determined correction
tables renew contents in the correction table number storing unit 137 and stored information
on recording head 854, and the renewed contents are utilized by the data conversion
circuit 138. Processing operations in the data conversion circuit 138 are basically
the same as operations in the above-mentioned embodiment (see FIG.8).
[0219] A different point from the previous embodiment is that when a nozzle indicates the
non-eject status, namely the correction table number is #0, contents of the compensation
table by different colors for generating compensation data by different colors, are
different from the previous embodiment. In the present embodiment, it is desirable
not to compensate highlighted portions recorded with relatively low recording duty
by different colors, since density corrections for respective nozzles are executed
by the shading and densities of nnext eighbor nozzles to the non-eject nozzle are
corrected so as to compensate the non-eject nozzle. Even when portions recorded with
high recording duty are compensated, extents of compensations by different colors
can be reduced compared with the above-mentioned embodiment due to above-mentioned
effects by density corrections in next neighbor nozzles.
[0220] More specifically, when correction curves for C and M as shown in FIG.5 are expressed
as f(x), new correction curves by Bk are expressed as β * f (x― δ). An example of
the new correction curve is plotted in FIG.7. The factor " β " in the new correction
curves has a range of 0<β<1 and the factor " δ " has a range of 0≦ δ ≦ 255. In the
correction curve plotted in FIG.7, β is ca. 0.3 and δ is ca. 128.
[0221] In the present embodiment, data conversions are executed by employing correction
tables by different colors shown in FIG.7.
[0222] Dot numbers for compensations by different colors can be reduced, since dots ejected
from next neighbor nozzles to the non-eject nozzle are recorded more by the above-mentioned
head shading operations. For example, FIG.3F is the conceptual diagram showing the
compensation table so as to correct densities of neighbor nozzles to the non-eject
nozzle to raise 1.5 times (corresponds to a correction curve 4b) of the inputted values
as shown in FIG.20 compared with the case without compensations (corresponds to a
correction curve 4a). These compensations recorded with 1.5 times density correspond
to FIGs.3A, 3B and 3D. Dots up to 4 can be recorded in respective grids shown in FIGs.3A,
3B, 3C and 3D. Therefore, FIG.3A illustrate a uniform pattern to be recorded with
low duty, i.e. one dot/grid.
[0223] Nozzles in a recording head to be used for recording dots in FIG.3C, are arrayed
in a vertical direction of this figure, where a non-eject nozzle corresponds to a
third row from the top. In these figures, circles in solid line indicate dot positions
recorded by normal nozzles, circles in fine broken line indicate dot positions to
be recorded by non-eject nozzles and circles in coarse broken line indicate dot positions
to be compensated. As can be understood from these figures, it is desirable that compensations
by the next neighbor nozzles to the non-eject nozzle should be recorded with densities
of 1.5 times.
[0224] However, in images recorded with high recording duty, white streaks are tend to be
seen conspicuously. Since sometimes dots are recorded in small sizes depending on
recording media, white streaks are seen conspicuously in images recorded with more
than 1/2 recording duty. In images to be recorded with high recording duty, defect
portions can be made inconspicuous, when positions corresponding to non-eject nozzles
are compensated by dots from other colors. Therefore in images to be recorded with
more than 2/3(67%) recording duty, dots from neighbor nozzles to non-eject nozzles
are recorded with 100% recording duty and at the same time positions corresponding
to the non-eject nozzles are compensated by other colors. When defects are made inconspicuous
only by neighbor nozzles to the non-eject nozzles, theoretically it is necessary to
record with more than 100% recording duty. However, since positions corresponding
to non-eject nozzles are compensated by other colors, recording duty to record dot
numbers from the neighbor nozzles can be reduced to 100%.
[0225] When images are recorded by converting data as mentioned above, images with high
quality almost all portions including highlighted portion and shadow portions, are
obtained.
[0226] Operating conditions whether compensations by other colors are executed on a selected
medium to be recorded or not, can be determined and stored in recording apparatus
or in a printer driver beforehand. However it is preferable to employ successive procedures
comprising steps of recording ink droplets on top end of a medium to be recorded,
measuring diameters of formed dots from droplets by the recording apparatus and determining
a blotting rate of the medium to be recorded.
[0227] The present invention exhibits its features more effectively when applied to recording
heads or recording apparatuses employing ink-jet recording methods, particularly,
methods utilizing thermal energy generating means (electro-thermal energy conversion
body, laser light source and the like) in order to utilize the generated energy for
causing a phase change in ink.
[0228] It is preferable to employ such typical methods, constitutions or principals of recording
apparatuses, for example, disclosed in the U.S. Patent Nos. 4,723,129 and 4,740,796.
The disclosed methods can be applied either to a so-called on-demand typed recording
apparatus or to a continuous typed recording apparatus. However, the on-demand typed
recording apparatus is effective in the following feature where at least one driving
signal corresponding to information to be recorded is applied to an electro-thermal
energy conversion body arranged on a sheet or a liquid path where ink is kept so as
to raise temperature above a nuclear boiling in a short period by generating energy
in the electro-thermal energy conversion body, consequently, bubbles can be formed
in accordance with the applied driving signal. Ink is ejected via an opening for ejecting
by growing/shrinking generated bubbles so that at least one droplet is formed. It
is more preferable to adjust the applied signal into a pulse form, since bubbles are
instantly and properly grown/shrunk in accordance with the applied signal, namely,
liquid (ink) ejection with excellent response in particular is attained. Driving signal
forms disclosed in the U.S. patent Nos. 4,463,359 and 4,345,262 are suitable to employ
as the driving signals with pulse forms. In addition, when conditions described in
the U.S. patent No. 4,313,124, an invention relating to temperature raising rate on
the above-mentioned thermal active surface, are employed, more excellent recording
results can be attained.
[0229] Arrangements of recording heads described in the U.S. patent Nos. 4,558,333 and 4,459,600
disclosing eject ports arranged on bending areas to which thermal energy applied as
well as combinations of eject ports, liquid paths and electro-thermal conversion bodies
are included in the present invention. In addition, effects by the present invention
are also exhibited in an invention described in the Japanese laid open patent No.
59-123670 relating to a common slits as eject ports corresponding to a plurality of
electro-thermal energy conversion bodies, and in an invention described in the Japanese
laid open patent No. 59-138461 disclosing an arrangement where openings to absorb
pressure waves from thermal energy are arranged against eject ports. In other words
recording operations are effectively executed without fail by the present invention,
no matter what types of recording head are employed.
[0230] The present invention also can be applied to a full line typed recording head capable
of recording on a recording medium with a maximum width. The full line typed recording
head can be constituted either by combining a plurality of recording heads or a monolithically
formed recording head.
[0231] Further, the present invention can be applicable to any type of recording heads such
as the above-mentioned serial type, an exchangeable tip typed recording head capable
of being supplied ink from a recording apparatus, on/to which the recording head is
mounted or electrically connected and a cartridge typed recording head where an ink
tank is monolithically formed with the recording head.
[0232] It is preferable add a recording head recovery means and auxiliary supporting means
as the components to the recording by the present invention, since the present invention
can exhibit its features more effectively. More specifically, a capping means against
the recording head, a cleaning means, a pressing or sucking means, a spare heating
means comprising electro-thermal conversion body, another heating element, a combination
of these heating bodies or pre-ejecting means except recording.
[0233] Either one recording head for mono color ink or a plurality of recording head for
mono color inks with different densities or a plurality of inks are applicable to
the present invention. Namely, the present invention is applicable not only to a recording
apparatus employing a recording mode with a main color such as black, but to a recording
apparatus employing a monolithically arranged recording head or a combination of a
plurality of recording heads. In addition the present invention is quite effective
to a recording apparatus employing at least one of the following recording modes:
a mode of a plurality of different a full color mode attained by mixing primary colors.
[0234] The present invention dissolves nonuniformity in a recorded image such as white streaks
generated by non-eject dots or the present invention makes the nonuniformity caused
by non-eject statuses not to be recognized by human eyes, which suppress operating
costs of the ink-jet recording apparatus from increasing and further attains effects
enabling recording rates raise much faster.
[0235] A recording system comprising a recording apparatus, a recording method and a program
to control the recording apparatus for recording a color image on a recording medium
by utilizing a recording head on which a plurality of recording elements are arranged,
is provided. The recording system further comprising, a plurality of compensation
means having respective own compensation methods to compensate a position to be recorded
by a recording element which does not execute a recording operation among said plurality
of recording elements; a selection means to select an appropriate compensation means.
Such recording system can dissolve nonuniformity in the recorded image such as white
streaks and the like generated by non-eject dots and can make the nonuniformity be
unrecognized by human eyes. In addition the recording system by the invention can
suppress raising costs of the recording head and can raise recording rates much faster.