BACKGROUND OF THE INVENTION
[0001] The present invention relates to a method and an apparatus for measuring the amount
of ink discharged, a printing apparatus, and a method of measuring the amount of ink
discharged while printing apparatus; and more particularly, to a method and an apparatus
for measuring the amount of ink discharged by a printhead, such as used by an ink-jet
printer, having fine nozzles which discharge a very small amount of ink from each
nozzle to print one dot.
[0002] For a printing apparatus, such as an ink-jet printer, which has a head consisting
of a plurality of fine nozzles, it is especially important to control the amount of
ink discharged from each nozzle of the printing apparatus to be uniform in order to
stabilize printing quality. For this purpose, it is desired to measure the amount
of ink discharged from each nozzle correctly and instantaneously.
[0003] There are known methods of measuring a small amount of colored ink droplet (e.g.,
color ink), namely, (1) a weighing method and (2) an absorbance method.
[0004] Followings are explanation when the amount of ink discharged from a nozzle of an
ink-jet printer is measured in the above two methods.
(1) Weighing Method
[0005] In this method, ink is discharged at a fixed interval for a predetermined time period,
and the amount (weight) of used ink in the time period is measured by a chemical balance
or the like (care must be used to minimize vaporization of ink during performing this
operation). Thereafter, by dividing the amount of ink used by the number of discharging
operation performed, an average amount of ink droplet in each discharging operation
can be obtained.
(2) Absorbance Method
[0006] This method uses the relationship between concentration of solution and light absorption,
which is known as Lambert-Beer's law. More specifically, solution having a certain
concentration is poured in a container having a fixed depth, and light having intensity
I0 is incidented on the container from one side, then intensity
I of the light transmitted through the solution in the container is measured. Since
a part of the incidented light is absorbed in the solution in the container, its intensity
is lowered while passing the solution. It is known that how the intensity is lowered
proportional to the concentration of the solution. Defining A as absorbance, then
an equation which represents the relationship of this law can be written as,
where
a is a slope,
b is the depth of the solution, and
c is the concentration of the solution. By using this equation, a calibration line
showing the relationship between concentration and absorbance for the ink to be used
is obtained in advance. Next, ink is discharged from a nozzle toward a transparent
solution (a solution which has a light absorbance as small as possible is preferred)
whose amount of ink discharged is correctly known, then absorbances by the solution
containing discharged ink after each discharging operation, namely absorbances corresponding
to the number of discharging operations, are measured. From the measured absorbances
and the calibration line which was obtained in advance, the concentration of the solution
including ink is determined. Then, the amount of ink mixed in the solution can be
found by taking the amount of the pure solution into consideration. Then the obtained
amount of ink is divided by the number of discharging operations, thereby finding
an average amount of ink discharged in each discharging operation.
[0007] However, in the aforesaid two conventional methods, there are problems in which a
certain amount of ink has to be discharged, and the amount of ink discharged per nozzle
per discharging operation can not be found instantaneously. Experimentally, when the
applicants of the present invention measured the amount of ink discharged per nozzle
in the weighing method, ink which was for 5,000 dots was discharged and it took 12
minutes. Thus, it takes quite a long time before finishing measuring the amount of
ink discharged from each nozzle of an ink-jet printer, having an ink discharge head
consisting of 64 or 128 fine nozzles. Furthermore, in the aforesaid two methods, since
the amount of ink per discharging operation is averaged, it is impossible to measure
the real amount of ink discharged per nozzle per discharging operation.
SUMMARY OF THE INVENTION
[0008] The present invention has been made in consideration of the above situation, and
has as its object to provide a method and apparatus capable of measuring the amount
of ink discharged from a nozzle instantaneously.
[0009] It is still another object of the present invention to provide a printing apparatus
adopting the aforesaid apparatus for measuring the amount of ink discharged and a
method of measuring the amount of ink discharged applicable to a printing apparatus.
[0010] According to the first aspect of a method of measuring the amount of ink discharged
of the present invention, the method comprising: a density measuring step of measuring
the density of an ink dot formed by an ink discharged from the printhead on a predetermined
medium; and a determining step of determining the amount of ink discharged on the
basis of the density of the ink dot measured at the density measuring step.
[0011] According to the second aspect of a method of measuring the amount of ink discharged
of the present invention, the method comprising: a preliminary measuring step of measuring
the amount of ink discharged from each of a plurality of ink-discharging nozzles of
the printhead in a single discharging operation under a predetermined condition in
advance; a first density measuring step of measuring densitys of ink dots made of
ink discharged from at least two different ink-discharging nozzles which discharge
different amounts of ink from each other out of the plurality of ink-discharging nozzles
onto a predetermined medium under the predetermined condition; a calibration line
generating step of generating a calibration line representing correlation between
the amount of ink discharged in a single discharging operation and a density of an
ink dot on the basis of data on the densitys of the ink dots, measured at the first
density measuring step, formed with the ink discharged from the at least two ink-discharging
nozzles and data on the amount of ink, measured at the preliminary measuring step,
discharged from the at least two ink-discharging nozzles; a second density measuring
step of measuring the density of an ink dot formed by an ink discharged from an arbitrary
nozzle of the printhead under an arbitrary condition; and a determining step of determining
the amount of ink discharged from the arbitrary nozzle under the arbitrary condition
on the basis of the data on the density of the ink dot, obtained at the second density
measuring step, and the calibration line.
[0012] Further, according to the first aspect of an apparatus for measuring the amount of
ink discharged of the present invention, the apparatus comprising: receiving means
for receiving the ink discharged from the printhead; density determining means for
determining the density of an ink dot formed by the discharged ink on the receiving
means; memory means for storing a calibration line representing correlation between
an amount of ink discharged and a density of an ink dot formed by the discharged ink
on the receiving means in a single discharging operation; and operation means for
finding the amount of the discharged ink on the basis of the density of the ink dot
determined by the density determining means and the calibration line.
[0013] Furthermore, according to the first aspect of a printing apparatus of the present
invention, the apparatus comprising: density determination means for determining a
density of an ink dot formed by an ink discharged from the ink-jet type printhead
on a receiving medium for receiving the discharged ink; memory means for storing a
calibration line representing correlation between the amount of ink discharged and
a density of an ink dot formed by the discharged ink on the receiving medium in a
single discharging operation; and operation means for finding the amount of the discharged
ink on the basis of the density of the ink dot determined by the density determining
means and the calibration line.
[0014] Further, according to the first aspect of a method of measuring the amount of ink
discharged adopted in a printing apparatus of the present invention, the method comprising:
a density measuring step of measuring the density of an ink dot formed by an ink discharged
from the printhead on a receiving medium for receiving the discharged ink; and a determining
step of determining the amount of ink discharged on the basis of the density of the
ink dot measured at the density measuring step.
[0015] According to the second aspect of a method of measuring the amount of ink discharged
adopted in a printing apparatus of the present invention, the method comprising: a
preliminary measuring step of measuring the amount of ink discharged from each of
a plurality of ink-discharging nozzles of the printhead in a single discharging operation
under a predetermined condition in advance; a first density measuring step of measuring
densitys of ink dots made of ink discharged from at least two different ink-discharging
nozzles which discharge different amounts of ink from each other out of the plurality
of ink-discharging nozzles onto a receiving medium for receiving ink under the predetermined
condition; a calibration line generating step of generating a calibration line representing
correlation between the amount of ink discharged in a single discharging operation
and a density of an ink dot on the basis of data on the densitys of the ink dots,
measured at the first density measuring step, formed with the ink discharged from
the at least two ink-discharging nozzles and data on the amount of ink, measured at
the preliminary measuring step, discharged from the at least two ink-discharging nozzles;
a second density measuring step of measuring a density of an ink dot formed by an
ink discharged from an arbitrary nozzle of the printhead under an arbitrary condition;
and a determining step of determining the amount of ink discharged from the arbitrary
nozzle under the arbitrary condition on the basis of the data on density of the ink
dot, obtained at the second density measuring step, and the calibration line.
[0016] Further, according to the third aspect of a method of measuring the amount of ink
discharged of the present invention, the method comprising: a density measuring step
of measuring the density of a line of a line pattern formed with an ink discharged
from the printhead on a predetermined medium; and a determining step of determining
an amount of ink discharged on the basis of the density of the line of the line pattern
measured at the density measuring step.
[0017] According to the fourth aspect of a method of measuring the amount of ink discharged
of the present invention, the method comprising: a preliminary measuring step of measuring
an amount of ink discharged from each of a plurality of ink-discharging nozzles of
the printhead in a single discharging operation under a predetermined condition in
advance; a first density measuring step of measuring densitys of ink dots made of
ink discharged from at least two different ink-discharging nozzles which discharge
different amounts of ink from each other out of the plurality of ink-discharging nozzles
onto a predetermined medium under the predetermined condition; a calibration line
generating step of generating a calibration line representing correlation between
the amount of ink discharged in a single discharging operation and the density of
an ink dot on the basis of data on the densitys of the ink dots, measured at the first
density measuring step, formed with the ink discharged from the at least two ink-discharging
nozzles and data on the amount of ink, measured at the preliminary measuring step,
discharged from the at least two ink-discharging nozzles; a second density measuring
step of measuring a density of a line of a line pattern formed with an ink discharged
from an arbitrary nozzle of the printhead under an arbitrary condition; and a determining
step of determining an amount of ink discharged from the arbitrary nozzle under the
arbitrary condition on the basis of the data on the density of the line of the line
pattern, obtained at the second density measuring step, and the calibration line.
[0018] Further, according to the second aspect of an apparatus for measuring the amount
of ink discharged of the present invention, the apparatus comprising: receiving means
for receiving an ink discharged from the printhead; density determining means for
determining the density of a line of a line pattern formed with the discharged ink
on the receiving means; memory means for storing a calibration line representing correlation
between the amount of ink discharged and the density of an ink dot formed by the discharged
ink on the receiving means in a single discharging operation; and operation means
for finding an amount of the discharged ink on the basis of the density of the line
of the line pattern determined by the density determining means and the calibration
line.
[0019] Other objects and advantages besides those discussed above shall be apparent to those
skilled in the art from the description of a preferred embodiment of the invention
which follows. In the description, reference is made to accompanying drawings, which
from a part hereof, and which illustrate an example of the invention. Such example,
however, is not exhaustive of the various embodiments of the invention, and therefore
reference is made to the claims which follow the description for determining the scope
of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The accompanying drawings, which are incorporated in and constitute a part of the
specification, illustrate embodiments of the invention and, together with the description,
serve to explain the principles of the invention.
Fig. 1 depicts a configuration of an apparatus for measuring an amount of ink discharged
according to the first embodiment of the present invention;
Fig. 2 shows an example of a dot pattern printed by using an ink-jet printer;
Fig. 3 shows an example when an ink dot subjected to measurement is marked by a window;
Fig. 4 is an example of a calibration line based on an experiment according to embodiments;
Fig. 5 depicts a printing apparatus with an apparatus for measuring an amount of ink
discharged;
Fig. 6 illustrates a configuration of an ink-jet head;
Fig. 7 is an explanatory view showing a method of controlling an amount of ink to
be discharged by changing pulse widths to be applied to a heater;
Fig. 8 is an explanatory view showing a method of correcting differences in amount
of ink discharged from each nozzles;
Fig. 9 is an explanatory view showing the method of correcting differences in amount
of ink discharged from each nozzles;
Fig. 10 is an explanatory view showing the method of correcting differences in amount
of ink discharged from each nozzles;
Fig. 11 is an explanatory view showing a method of changing printing densities;
Fig. 12 is an explanatory view showing the method of changing printing densities;
Fig. 13 is an explanatory view showing the method of changing printing densities;
Fig. 14 depicts a configuration of an apparatus for measuring an amount of ink discharged
according to a fourth embodiment of the present invention;
Fig. 15 illustrates an example of a line pattern printed by using an ink-jet printer;
Fig. 16 shows an example when a line subjected to measurement is marked by a window;
Fig. 17 shows another example when a line subjected to measurement is marked by a
window;
Fig. 18 illustrates data of ink-discharge patterns for comparison between a dot density
method and a line pattern density method; and
Fig. 19 is a graph illustrating measured results based on the dot density method and
the line pattern density method.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] Preferred embodiments of the present invention will be described in detail in accordance
with the accompanying drawings.
(First Embodiment)
[0022] Fig. 1 depicts a configuration of an apparatus for measuring the amount of ink discharged
according to the first embodiment of the present invention. In Fig. 1, reference numeral
1 denotes an image processing unit for measuring density (it may be referred to as
tint) of an ink dot (simply referred as "dot", hereinafter); 2, a personal computer
(referred as "PC", hereinafter) used for controlling the image processing unit 1 and
an XY control stage 4; 3, an optical microscope; 4, the XY control stage to be used
when the density of object to be measured is continuously measured; 5, a color CCD
camera for inputting an image of the object to be measured into the image processing
unit 1; and 6, a light source placed under the XY control stage 4. The central part
of the surface of the XY control stage 4 is made of glass, and the object to be measured
is illuminated by the light source placed underneath of the glass and an object image
can be inputted from the color CCD camera 5. The PC 2 controls the XY control stage
4 through RS232C or GPIB interface as well as controls the image processing unit 1.
[0023] Fig. 2 is an example when a plurality of nozzle of an ink-jet printer discharge ink
on a transparent glass plate 10 three times. Further, 'same nozzle direction' in Fig.
2 indicates the direction of ink dots discharged from an identical nozzle, and 'different
nozzle direction' indicates the direction of ink dots discharged from a plurality
of different nozzles in a single discharging operation. It should be noted that, since
ink and glass are incompatible with each other, a special process for mediating between
the discharged ink and the glass plate 10 is to be necessarily applied on the glass
plate 10 (the glass plate is coated with polyvinyl alcohol to form an ink-absorbent
layer 12 in this example). With this process, ink discharged from each nozzle in a
single discharging operation is uniformly absorbed by the ink-absorbent layer 12 and
forms a round-shaped dot. As for the material of the ink-absorbent layer 12, a material
which is as transparent and colorless as possible (i.e., which do not absorb light)
is preferred.
[0024] Under the conditions in which the microscope 3 focuses on an arbitrary one of the
dots printed as shown in Fig. 2 and the magnification of the microscope 3 and the
intensity of the light source 6 are properly adjusted, an image of the focused dot
is inputted by the color CCD camera 5 to the image processing unit 1. In the image
Processing unit 1 used in this embodiment, a single color image can be decomposed
into images of red (R), green (G) and blue (B) which are the three primary colors
of light of optics, to form three monochromatic images, namely, a monochromatic image
representing luminance level of light in the red (R) wavelength range, a monochromatic
image representing luminance level of light in the green (G) wavelength range, and
a monochromatic image representing luminance level of light in the blue (B) wavelength
range. These monochromatic images are formed with minimal pixel units to which the
image processing unit 1 can resolve, and each minimal pixel can express luminance
level in 256 tones, between 0 and 255 tone, in accordance with the intensity of the
transmitted light through each pixel.
[0025] Next, a method of measuring density of a dot will be explained.
[0026] In this embodiment, the density of a dot is determined by how much the incidented
light (white light) is absorbed while transmitting through a dot with color (density)
which is subjected to measurement. The higher the density of a dot subjected to measurement,
the more the light is absorbed, and the intensity of the transmitted light is decreased.
Therefore, the luminance level of the minimum pixel in an area of the dot subjected
to measurement decreases. Contrarily, if the density of the dot is low, then the luminance
level of the minimum pixel must be high. This embodiment focuses on this fact, and
the density is replaced by light absorbances (although what the image processing unit
1 actually measures is a luminance level).
[0027] For example, in a case of measuring the light absorbance of a dot, printed with red
ink, subjected to measurement, since the red dot transmits red light, in a monochromatic
image which is responsive for red light the dot looks as blight as its surrounding.
Thus, it is impossible to measure the density of the red dot in a monochromatic image
which is responsive for red light. In contrast, in a monochromatic image which is
responsive for blue light, as the density of the dot becomes higher, less blue light
is transmitted. Accordingly, the intensity of the transmitted light changes depending
upon changes of the density of the dot, thus the density of the dot can be measured
in a monochromatic image which is responsive for blue light. Therefore, a band-pass
filter which selectively transmits light in the blue wavelength range is provided
over a dot printed with red ink, and the luminance level of the transmitted light
is measured in the monochromatic image which shows luminance levels of light in the
blue wavelength range. It should be noted that there is a method of measuring the
density of the dot printed with red ink by using the green monochromatic image, however,
it is considered most preferable to measure the luminance level of the red dot in
the blue monochromatic image since the overlapping wavelength range between the red
wavelength range and the green wavelength range is wider than the overlapping wavelength
range between the red wavelength range and the blue wavelength range.
[0028] In this embodiment, a dot pattern to be measured shown in Fig. 2 are printed with
blue ink on the glass plate 10. Therefore, luminance levels of the dots are measured
in the red monochromatic image because of the aforesaid reason.
[0029] Then, an image of a pixel subjected to measurement inputted as described above is
marked with a fixed sized frame (called "window", hereinafter) as shown in Fig. 3.
Basically, it is preferred to sum up all the luminance levels inside of the minimal
pixels of the dot to measure its density, However, when the dot is actually observed
by the microscope, it is very difficult to determine the border between the dot and
background since the density in the edge part of the dot is low. Therefore, a window
whose size is large enough to surely includes the entire dot subjected to measurement
(including its surrounding) is used to specify an area, then all the luminance levels
of the minimal pixels in the window are summed up. The sum is considered as the total
luminance of the dot subjected to measurement.
[0030] The window size can be arbitrarily determined in consideration with the size of a
dot subjected to measurement. However, if the window size is set too large, the luminance
level in too large a background area which is essentially nothing to do with the dot
density is included, which degrades accuracy of the measured data. Therefore, too
large a window size is not preferable.
[0031] Prior to finding the total luminance of the dot shown in Fig. 3, a part which does
not include a printed dot (i.e, a part where only the ink-absorbent layer 12 exists)
is first marked by the window, and the total luminance inside of the window is measured.
This total luminance is defined as a reference total luminance which indicates a state
in that light absorbance is the minimum (i.e., minimum density). Then, the actually
measured total luminance of the dot subjected to measurement is divided by the reference
total luminance, then the reciprocal of the quotient or the logarithm of the reciprocal
is defined as the absorbance (density data) of the dot subjected to measurement.
[0032] Next, a method of finding a calibration line which is to be the reference for measuring
the amount of ink discharged from an arbitrary nozzle of an ink-jet head in a single
discharging operation under arbitrary conditions will be described below. In the explanation
below, an amount of ink discharged in a single discharging operation usually indicates
an ink droplet. However, since there are cases in which the ink does not form a droplet,
thus an expression, "an amount of ink discharged in a single discharging operation"
is used instead of "an ink droplet".
[0033] As the first process, amounts of ink discharged from at least two different nozzles
which discharge different amounts of ink from each other as much as possible among
a plurality of nozzles of an ink-jet head, subjected to measurement of amount of ink
discharged, in a single discharging operation under a fixed condition are measured
by using the weighing method or the absorbance method which have been described as
the prior arts.
[0034] In this embodiment, the amounts of ink discharged from four different nozzles which
are known to discharge different amounts of ink in a single discharging operation
under a fixed condition are measured in advance by using the weighing method.
[0035] Next, ink is discharged again under the same condition as that the discharging amounts
are measured as above from the four nozzles whose discharging amounts of ink in a
single discharging operation have been found as above, and the densitys of the ink
dots formed with the discharged ink on the glass plate is measured in the aforesaid
method. By performing this measurement, the amounts of ink discharged from the four
nozzles and the densitys of the ink dots formed with the discharged ink can be found
in one-to-one relationship. Note, the density data of ink dots printed by the four
nozzles were found as averages of sampled densitys of 50 dots printed. Standard deviation
of the density data in the aforesaid measurement was within 5% with respect to the
averages.
[0036] Fig. 4 is a graph of densitys of ink dots formed on the glass plate 10 with respect
to amounts of ink, forming the ink dot, discharged in each discharging operation of
four nozzles. In Fig. 4, small black points show the densitys of ink dots with respect
to the amounts of ink discharged from the four nozzles. As seen in this graph, four
points are approximately on a single straight line. Therefore, by drawing a straight
line which fits the four points and using it, density of an ink dot corresponding
to an arbitrary amount of ink discharged can be found based on the straight line in
one-to-one relationship. This straight line is called a "calibration line".
[0037] It should be noted that, since the calibration line is expressed by a straight line,
at least two points on the graph are necessary to plot the calibration line. Therefore,
it is possible to find the calibration line by using minimum of two nozzles, instead
of using four nozzles as above. However, since data of amount of ink discharged measured
by using either the weighing method or the absorbance method is used to find the calibration
line, the accuracy of the used measuring method directly affects the method of measuring
an amount of ink discharged in this embodiment. Therefore, it is considered to be
preferable to use more than two nozzles to find the calibration line. Further, the
calibration line needs to be independently measured each time when ink to be used
is changed.
[0038] Thereafter, by measuring the density of a dot formed with ink discharged from an
arbitrary nozzle under an arbitrary condition in the aforesaid method, it is possible
to find the amount of ink discharged from the nozzle by referring to the calibration
line.
[0039] Further, it is possible to sequentially measure the densitys of dots by controlling
the XY control stage 4 by using the PC 2. For example, dots are printed at an interval
as shown in Fig. 2, series of dots are arraigned on the XY control stage 4, and pitches
of movement in the X and Y directions are designated. Accordingly, densitys of dots
printed by an identical nozzle or densitys of dots printed by different nozzles can
be sequentially measured. Then, an equation for converting the density to the discharged
amount is found in advance in accordance with the calibration line obtained in advance.
Accordingly, by using the equation, data obtained by measuring the density of a dot
can be instantly converted to data of amount of ink discharged by using the PC 2.
It should be noted that the data of the obtained calibration line is stored in a memory
of the PC 2.
[0040] Next, a printing apparatus having the aforesaid function for measuring amount of
ink discharged will be described below.
[0041] Fig. 5 is a printing apparatus which contains the apparatus for measuring the amount
of ink discharged as described above. In Fig. 5, reference numeral 51 denotes a personal
computer (referred as "PC", hereinafter), having image processing function, for controlling
the printing apparatus and the apparatus of measuring the amount of ink discharged;
52, a printer main body; 53, a printer stage where a printing medium is set; and 54,
an ink-jet type printhead which prints as moving left-to-right in this embodiment.
Further, reference numeral 55 denotes a printing medium, such as a paper sheet; 56,
a CCD camera; 57, a microscope for magnifying a printed dot; 58, a stage of the microscope
57 (has a hole in the central part so that it can utilize a light source); 59, a light
source; 60, a transparent plate, such as a glass plate; and 61, a roller used for
moving the transparent plate 60 on the stage 58 of the microscope 57.
[0042] In the aforesaid apparatus, the printhead 54 prints on the printing medium 55 as
it moves back and forth in the right and left direction. After the printhead 54 has
printed for a predetermined time period or the predetermined number of lines, it moves
to the transparent plate 60 where it prints dots by using the nozzles currently being
used for printing. The transparent plate 60 moves under the microscope 57, and the
densitys of the dots printed on the transparent plate 60 are measured in accordance
with the aforesaid method by using the light source 59 and the CCD camera 56. Next,
the PC 51 instantly converts each measured density into the amount of ink discharged
by referring to the calibration line obtained in advance. If the amount of ink discharged
is outside of a predetermined range, for example, a pulse width, or the like, to be
applied to the nozzle of the printhead is changed so as to properly control an amount
of ink discharged from the nozzle.
[0043] In this case, it is not necessary for the printer to suspend the printing operation
after the printhead 54 has printed dots on the transparent plate 60 until the amount
of ink discharged is calculated, i.e., the calculation of the amount of ink discharged
and the printing operation can be carried on in parallel.
[0044] Further, by developing a print pattern of several lines on an image memory of the
apparatus, the PC 51 can predict which nozzle is used continuously for how long time.
The PC 51 decides a timing to measure amount of ink discharged in accordance with
the prediction. Therefore, there would be a case where amount of ink discharged is
not measured at all during a printing operation, depending on a printing pattern.
This series of control can be arbitrary changed by changing a control program stored
in the PC 51.
[0045] A configuration of an ink-jet head and a method of controlling the amount of ink
discharged in the ink-jet head will be explained below.
[0046] Fig. 6 shows a configuration of an ink-jet head IJH.
[0047] Referring to Fig. 6, the ink-jet head IJH mainly comprises a heater board 104 as
a board on which a plurality of heaters 102 for heating an ink are formed, and a ceiling
plate 106 mounted on the heater board 104. A plurality of discharging openings 108
are formed in the ceiling plate 106. Tunnel-like fluid passages 110 communicating
with the discharging openings 108 are formed therebehind. The respective fluid passages
110 are isolated from the adjacent fluid passages by partition walls 112. The respective
fluid passages 110 are commonly connected to one ink chamber 114 at the rear end of
the fluid passages. An ink is supplied to the ink chamber 114 via an ink inlet 116,
then supplied from the ink chamber 114 to each fluid passage 110.
[0048] The heater board 104 and the ceiling plate 106 are positioned such that the position
of each heater 102 coincides with that of a corresponding fluid passage 110, and are
assembled into the state shown in Fig. 6. Although Fig. 6 shows only two heaters 102,
the heater 102 is actually arranged in correspondence with each fluid passage 110.
When a predetermined driving pulse is supplied to the heater 102 in the assembled
state shown in Fig. 6, an ink above the heater 102 is led to film boiling and a bubble
is produced, and the ink is pushed and discharged from the discharging opening 108
upon volume expansion of the bubble. Therefore, the size of a bubble can be adjusted
by controlling a driving pulse applied to the heater 102, e.g., controlling the magnitude
of electric power. That is, the volume of the ink discharged from each discharging
opening can be controlled as desired.
[0049] Fig. 7 is a timing chart for explaining a method of controlling the amount of ink
discharged by changing electric power supplied to each heater in the aforesaid manner.
[0050] In this embodiment, two types of constant-voltage pulses are applied to each heater
102 to adjust the amount of ink discharged. The two pulses are a preheat pulse and
a main heat pulse (to be simply referred to as a heat pulse hereinafter) as shown
in Fig. 7. The preheat pulse is a pulse for heating the ink to a predetermined temperature
before the ink is actually discharged. The pulse width of this pulse is set to be
smaller than a minimum pulse width t5 required to discharge the ink. Therefore, the
ink is not discharged by this preheat pulse. The preheat pulse is applied to each
heater 102 to increase the initial temperature of the ink to a predetermined temperature
in advance so as to always make the amount of ink discharged constant when a constant
heat pulse is applied to the heater 102 afterward. In contrast to this, the temperature
of the ink may be adjusted in advance by adjusting the width of a preheat pulse. In
this case, for the same heat pulse, the amount of ink discharged can be changed. In
addition, by heating an ink before application of a heat pulse, the preparation time
required to discharge the ink upon application of the heat pulse can be shortened,
which improves the responsiveness of the printhead to the heat pulse.
[0051] The heat pulse is a pulse for actually discharging the ink. The pulse width of the
heat pulse is set to be larger than the minimum pulse width t5 required to discharge
the ink. Energy generated by each heater 102 is proportional to the width (application
time) of a heat pulse. Therefore, variations in the characteristics of the heaters
102 can be adjusted by adjusting the width of each heat pulse.
[0052] Note that the amount of ink discharged can be also adjusted by adjusting the interval
between a preheat pulse and a heat pulse to control the dispersing state of heat upon
application of the preheat pulse.
[0053] As is apparent from the above description, the amount of ink discharged can be controlled
both by adjusting the application time of a preheat pulse or a heat pulse and by adjusting
the interval between application of a preheat pulse and that of a heat pulse. Therefore,
by adjusting the application time of a preheat pulse and a heat pulse or the interval
between application of a preheat pulse and that of a heat pulse as needed, the amount
of ink discharged or the responsiveness of the printhead discharging the ink to an
applied pulse can be adjusted as desired.
[0054] Such adjustment of the amount of ink discharged will be described in detail next.
[0055] Assume that the ink is discharged in different amounts from the discharging openings
(nozzles) 108a, 108b, and 108c upon application of the same energy, as shown in Fig.
7. More specifically, assume that when predetermined energy is applied at a predetermined
temperature, the amount of ink discharged from the nozzle 108a is 36 pl (pico-liters);
the amount of ink discharged from the nozzle 108b, 40 pl; and the amount of ink discharged
from the nozzle 108c, 40 pl, and the resistance of heaters 102a and 102b respectively
corresponding to the nozzles 108a and 108b is 200 Ω, and the resistance of a heater
102c corresponding to the nozzle 108c is 210 Ω. Further, assume that the amounts of
ink discharged from the nozzles 108a, 108b, and 108c are to be adjusted to 40 pl.
[0056] The widths of a preheat pulse and a heat pulse may be adjusted to adjust the amounts
of ink discharged from the nozzles 108a, 108b, and 108c to the same amount. Various
combinations of the widths of preheat pulses and heat pulses are conceivable. In this
embodiment, the amounts of energy generated by heat pulses are made equal for the
three nozzles, and the amounts of ink discharged are adjusted by adjusting the widths
of preheat pulses.
[0057] Since the heaters 102a and 102b for the nozzles 108a and 108b have the same resistance,
i.e., 200 Ω, the amounts of energy generated by heat pulses can be made equal by applying
voltage pulses having the same width to the heaters 102a and 102b. In this embodiment,
the width of each voltage pulse is set to be t3 which is longer than the width t5.
However, the ink is discharged in different amounts, i.e., 36 pl and 40 pl, from the
nozzles 108a and 108b upon application of identical energy. In order to increase the
amount of ink discharged from the nozzle 108a, a preheat pulse having a width t2 longer
than a width t1 of a preheat pulse applied to the heater 102b is applied to the heater
102a. With this operation, the amounts of ink discharged from the heaters 108a and
108b can be adjusted to 40 pl.
[0058] The heater 102c for the nozzle 108c has a resistance of 210 Ω, which is higher than
the resistance of the two other heaters 102a and 102b. For this reason, in order to
cause the heater 102c to generate the same amount of energy as that generated by the
two other heaters, the width of a heat pulse must be set to be longer than that of
the above heat pulse. In this embodiment, therefore, the width of the heat pulse is
set to be t4 which is longer than the width t3. Since the amounts of ink discharged
from the nozzles 108b and 108c upon application of the same amount of energy are the
same, the width of a preheat pulse required is equal to that of a preheat pulse applied
to the heater 102b. That is, a preheat pulse having the width t1 is applied to the
heater 102c.
[0059] In the above manner, the same amount of ink can be discharged from the nozzles 108a,
108b, and 108c which discharge an ink in different amounts upon application of a predetermined
energy to corresponding heaters having different resistance from each other. In addition,
the amounts of ink discharged may be intentionally made different from each other.
Note that preheat pulses are used to reduce variations in the amount of ink discharged
from each nozzle.
[0060] Next, two typical method for reducing unevenness in printing by an ink-jet head will
be described.
[0061] Figs. 8 to 10 show a method of correcting differences between amounts of ink discharged
from a plurality of nozzles of the ink-jet head IJH (called "bit correction", hereinafter).
[0062] First, as shown in Fig. 8, three nozzles, a nozzle 1, a nozzle 2 and a nozzle 3,
for example, of the ink-jet head IJH is made discharge ink onto a predetermined plate
P. Then, the sizes of ink dots made of the ink discharged from respective nozzles
1, 2 and 3 on the plate P are measured, and the amount of ink discharged from each
nozzle is found. Upon measuring the amount of ink discharged, heat pulses (refer to
Fig. 7) to be applied to heaters of the nozzles are first set to a fixed pulse width,
and the preheat pulse widths (refer to Fig. 7) are changed as already described above.
As a result, as shown in Fig. 9, curves showing relationship between preheat pulse
widths (referred as "heating time period" in Fig. 9) and the amounts of ink discharged
are obtained. If it is desired to fix the amount of ink to be discharged from each
nozzle to 20 ng, then it can be found from the graph shown in Fig. 9 that the pulse
width to be applied to the nozzle 1 is 1.0 µs, to the nozzle 2, 0.5 µs, and to the
nozzle 3, 0.75 µs. Therefore, by applying the preheat pulses having above pulse widths
to the heaters of the nozzles, it is possible to adjust the amount of ink discharged
from each nozzle to a fixed amount of 20 ng. To correct the amount of ink discharged
from each nozzle as described above is called bit correction. In this embodiment,
the pulse width of the preheat pulse is changed in four stages, which achieves correction
range of the amount of ink discharged by about 30% of the amount. Further, the resolution
of the correction is between 2% and 3%.
[0063] Next, Figs. 11 to 13 show a method of correcting unevenness in printing in the scanning
direction of the ink-jet head (called "shading correction", hereinafter) by adjusting
density of dots (i.e., the number of dots printed in a unit area) printed by ink-discharging
nozzles.
[0064] As shown in Fig. 11, for example, when the amount of ink discharged from the nozzle
3 of the ink-jet head is defined as reference, assume that the amount of ink discharged
from the nozzle 1 is about 10% less then the reference, and the amount of ink discharged
from the nozzle 2 is about 20% more than the reference. Under this condition, while
the ink-jet head IJH scans, the heater of the nozzle 1 is applied with heat pulses
once every nine reference clocks, the heater of the nozzle 2 is applied with heat
pulses once every 12 reference clocks, and the heater of the nozzle 3 is applied with
heat pulses once every 10 reference clocks as shown in Fig. 12. Thus, the number of
discharging operations in the scanning direction can be adjusted for each nozzle,
thereby it is possible to set density of printed ink dots in the scanning direction
to a uniform density, thus preventing unevenness in printing. To correct density of
printed ink dots in the scanning direction as described above is called "shading correction".
In this embodiment, this correction achieves correction range of the density of ink
discharged by about 30% of the density. Further, it is possible to control the distance
between each dots to be infinitely short (i.e., to increase resolution) theoretically.
However, if doing so, the amount of data greatly increases, which makes the processing
speed slower. Therefore, about 10% increase in resolution is the substantial limitation.
[0065] Upon measuring the amount of ink discharged by using the measuring apparatus according
to the first embodiment and actually performing printing operation by a printing apparatus
in accordance with the measured results, it is possible to correct unevenness in density,
caused by difference in the amount of ink discharged from each nozzle, by properly
adjusting the amount of ink discharged by using a method of the changing pulse width
of a preheat pulse or a method of changing density of printed dots.
(Second Embodiment)
[0066] In the first embodiment, the light source which emits white light is used. In a case
where density of a dot of blue (B) ink is to be measured, a proper band-pass filter
which transmits light in red (R) wavelength range is placed between the light source
and the dot, then absorbance of a dot is measured from the light transmitted through
the band-pass filter and the dot (light in red wavelength range). Upon measuring the
absorbance, it is necessary to optimize the intensity of light from the light source
and the band-width of the filter, needless to say. In addition to these optimizations,
to increase the tones of luminance levels (256 tones in the first embodiment) may
further increases accuracy of measured data.
(Third Embodiment)
[0067] The image processing unit is used to measure the density of a dot in the aforesaid
first and second embodiments, however, the present invention is not limited to this.
For example, transmitted light may be received by PMT (Photoelectron Magnification
Tube), then the output from the PMT may be analog-digital converted into a signal
in luminance level. At this time, by using an A/D converter having higher resolution,
better measurement accuracy can be achieved as mentioned in the second embodiment.
[0068] Further, luminance level (quantity of light) of the transmitted light is found as
a density in the above embodiments, however, the present invention is not limited
to the transmitted light, and reflected light received can be used instead.
(Fourth Embodiment)
[0069] Fig. 14 depicts a configuration of a measuring apparatus according to a fourth embodiment
of the present invention. In Fig. 14, reference numeral 201 denotes an image processing
unit for measuring density; 202, a personal computer (referred as "PC", hereinafter)
used to control the image processing unit 201 and an X control stage 204; 203, an
optical system for magnifying an image; 204, the X control stage used when densitys
of an object subjected to measurement are measured continuously; 205, a line sensor
camera for inputting an image of the object subjected to measurement into the image
processing unit 201; and 206, a light source set under the X control stage 204. The
central part of the surface of the X control stage 204 is made of glass so that an
image of the object to be measured can be inputted by the line sensor camera 205 by
utilizing light from the light source 206. The PC 202 controls the X control stage
204 via RS232C or GPIB interface as well as controls the image processing unit 201.
[0070] Fig. 15 shows a line pattern formed by discharging ink from a plurality of different
nozzles of an ink-jet printer onto a transparent glass plate 210. Further, 'same nozzle
direction' in Fig. 15 indicates the direction of ink lines discharged from an identical
nozzle, and 'different nozzle direction' indicates the direction of ink discharged
from a plurality of different nozzles. It should be noted that, since ink and glass
are incompatible with each other, a special process for mediating between the discharged
ink and the glass plate 210 is to be necessarily applied on the glass plate 210 (the
glass plate is coated with polyvinyl alcohol to form an ink-absorbent layer 212 in
this example). With this process, ink discharged from each nozzle is uniformly absorbed
by the ink-absorbent layer 212 and forms the line pattern as shown in Fig. 15. As
for the material of the ink-absorbent layer 212, a material which is as transparent
and colorless as possible (i.e., which do not absorb light) is preferred.
[0071] The optical system 203 focuses on an arbitrary line of the line pattern as shown
in Fig. 15 and the magnification of the optical system 203 and the intensity of light
from the light source 206 are properly adjusted. Under this condition, an image of
the focused image is inputted by the line sensor camera 205 into the image processing
unit 201. In the fourth embodiment, the magnification is 5, however, the present invention
is not limited to this.
[0072] The line sensor camera 205 in this embodiment is a black-and-white line sensor. An
image inputted by this line sensor camera 205 consists of a collection of minimal
pixel units that the image processing unit 201 can resolve, and each minimal pixel
can represent luminance level in 256 tones, between 0 and 255 tones, in accordance
with the intensity of the transmitted light.
[0073] Next, a method of measuring the density of a line of the line pattern will be described.
[0074] In this embodiment, the density of a line of the line pattern is determined by how
much the incidented light (white light) is absorbed while transmitting a line with
color (density) which is subjected to measurement. More specifically, the higher the
density of a line subjected to measurement is, the more the light is absorbed, and
the intensity of transmitted light is decreased. Therefore, the luminance level of
the minimal pixel in an area of the line subjected to measurement must be low. Contrarily,
if the density of the line is low, then the luminance level of the minimal pixel must
be high. This embodiment focuses on this fact, and the density is replaced by a light
absorbance (although what the image processing unit 1 actually measure is a luminance
level). The fourth embodiment is the same as the first embodiment in this point.
[0075] Then, an image of a line subjected to measurement inputted as described above by
using the line sensor camera is enclosed by a fixed sized frame (called "window",
hereinafter) as shown in Fig. 16. Basically, it is preferred to sum up all of the
luminance levels of the minimal pixels of a line subjected to measurement to measure
its density, however, when the line is actually observed through the microscope, it
is very difficult to determine the border between the line and the background since
the density in the edge part of the line is low. Therefore, a window whose size is
large enough to include the entire line subjected to measurement (including its surrounding)
is used to specify an area, then all the luminance levels of the minimal pixels in
the window are summed up. The obtained sum is considered as a total luminance of the
line subjected to measurement.
[0076] The window size can be arbitrarily determined in consideration with the size of the
line subjected to measurement. However, if the window size is set too large, the luminance
level in too large background area which is essentially nothing to do with the line
density is included, which degrades accuracy of the measured data. Therefore, too
large window size is not preferable.
[0077] Prior to finding the total luminance of the line shown in Fig. 16, the part which
does not include the line pattern (i.e., the part where only the ink-absorbent layer
12 exists) is first marked by the window of the same size (shown in doted line), and
the total luminance inside of the window is found. This total luminance is defined
as a reference total luminance which indicates a state in that light absorbance is
the minimum (i.e., minimum density). Then, the actually measured total luminance of
the line subjected to measurement is divided by the reference total luminance, then
the common logarithm of the reciprocal of the quotient is defined as the absorbance
(density data) of the line subjected to measurement.
[0078] Namely,
[0079] Fig. 17 shows a case where the reference total luminance is found near the line pattern.
According to experiments conducted by the applicants of the present invention, better
result was obtained when the reference total luminance was calculated near the line
pattern as shown in Fig. 17 than the reference total luminance was calculated in the
area apart from the line patterns by some distance. The reason for this would be effect
of the spatial distribution of the quantity of light from the light source.
[0080] Thereafter, remaining lines of the line pattern are marked by a window of the same
size in sequence, and absorbances (density data) of the lines can be obtained in the
same manner as described above.
[0081] Then, by controlling the X control stage 204 by using the PC 202, the line pattern
can be continuously inputted. Thereafter, each line of the line pattern is marked
with the window after inputting the line pattern, absorbances of all the lines of
the line pattern can be found. With a calibration line obtained in advance (a method
of measuring the calibration line is the same as that in the first embodiment), it
is easy to convert the density of each line of the line pattern into an amount of
ink discharged in a single discharging operation by using the PC 202.
[0082] Next, it will be shown that a method of finding the amount of ink discharged in a
single discharging operation based on the density of a line of the line pattern (line
pattern density method) can be used instead of a method of finding an amount of ink
discharged in a single discharging operation based on the density of an ink dot (dot
density method), which is described in the first embodiment.
[0083] Fig. 18 shows an ink-discharging pattern used in the measurement. Twelve dots are
printed by using an identical nozzle, then a line is printed. Each line of the formed
line pattern by a plurality of nozzles is formed with 50 dots. The densitys of the
dots are measured by using the dot density method, and the densitys of the lines are
measured by using the line pattern density method. Thereafter, the obtained data in
absorbance is compared. The average of the densitys of the 12 dots is taken as data
in the dot density method. The comparison result is shown in Fig. 19.
[0084] As seen in Fig. 19, it can be concluded that the line pattern density method according
to the fourth embodiment is worth replacing the dot density method.
[0085] Further, in the dot density method, since a plurality of dots are measured for finding
an average amount of ink discharged, it takes some time to find the average amount.
In contrast, a line of the line pattern is measured in a single measuring operation
according to the fourth embodiment, thus there is a merit that measuring time can
be shortened.
[0086] After an amount of ink discharged in a single discharging operation is measured as
described above, the obtained result is fed back to the printing apparatus so that
printing on a printing medium is performed without unevenness in density of each ink
dot by adjusting an amount of ink to be discharged by using an adjusting method as
described in the first embodiment.
(Fifth Embodiment)
[0087] In the fourth embodiment, the line sensor camera is used for inputting an image of
the line pattern, however, a CCD camera, or other area sensors can be used instead.
Further, by increasing the number of luminance levels used in the image processing
operation (256 tones are used in the fourth embodiment), accuracy of the measured
data can be further increased.
[0088] The present invention is not limited to the above embodiments, and various changes
and modifications can be made within the spirit and scope of the present invention.
[0089] Each apparatus described in the embodiments described above comprises means (e.g.,
an electrothermal transducer, laser beam generator, and the like) for generating heat
energy as energy utilized upon execution of ink discharge, and causes a change in
state of an ink by the heat energy, among the ink-jet printers. According to this
ink-jet printer and printing method, a high-density, high-precision printing operation
can be attained.
[0090] As the typical arrangement and principle of the ink-jet printing system, one practiced
by use of the basic principle disclosed in, for example, U.S. Patent Nos. 4,723,129
and 4,740,796 is preferable. The above system is applicable to either one of so-called
an on-demand type and a continuous type. Particularly, in the case of the on-demand
type, the system is effective because, by applying at least one driving signal, which
corresponds to printing information and gives a rapid temperature rise exceeding film
boiling, to each of electrothermal transducers arranged in correspondence with a sheet
or liquid channels holding a liquid (ink), heat energy is generated by the electrothermal
transducer to effect film boiling on the heat acting surface of the printhead, and
consequently, a bubble can be formed in the liquid (ink) in one-to-one correspondence
with the driving signal. By discharging the liquid (ink) through a discharge opening
by growth and shrinkage of the bubble, at least one droplet is formed. If the driving
signal is applied as a pulse signal, the growth and shrinkage of the bubble can be
attained instantly and adequately to achieve discharge of the liquid (ink) with the
particularly high response characteristics.
[0091] As the pulse driving signal, signals disclosed in U.S. Patent Nos. 4,463,359 and
4,345,262 are suitable. Note that further excellent printing can be performed by using
the conditions described in U.S. Patent No. 4,313,124 of the invention which relates
to the temperature rise rate of the heat acting surface.
[0092] As an arrangement of the printhead, in addition to the arrangement as a combination
of discharge nozzles, liquid channels, and electrothermal transducers (linear liquid
channels or right angle liquid channels) as disclosed in the above specifications,
the arrangement using U.S. Patent Nos. 4,558,333 and 4,459,600, which disclose the
arrangement having a heat acting portion arranged in a flexed region is also included
in the present invention. In addition, the present invention can be effectively applied
to an arrangement based on Japanese Patent Laid-Open No. 59-123670 which discloses
the arrangement using a slot common to a plurality of electrothermal transducers as
a discharge portion of the electrothermal transducers, or Japanese Patent Laid-Open
No. 59-138461 which discloses the arrangement having an opening for absorbing a pressure
wave of heat energy in correspondence with a discharge portion.
[0093] Furthermore, as a full line type printhead having a length corresponding to the width
of a maximum printing medium which can be printed by the printer, either the arrangement
which satisfies the full-line length by combining a plurality of printheads as disclosed
in the above specification or the arrangement as a single printhead obtained by forming
printheads integrally can be used.
[0094] In addition, not only an exchangeable chip type printhead which can be electrically
connected to the apparatus main unit and can receive an ink from the apparatus main
unit upon being mounted on the apparatus main unit but also a cartridge type printhead
in which an ink tank is integrally arranged on the printhead itself can be applicable
to the present invention.
[0095] It is preferable to add recovery means for the printhead, preliminary auxiliary means,
and the like provided as an arrangement of the printer of the present invention since
the printing operation can be further stabilized. Examples of such means include,
for the printhead, capping means, cleaning means, pressurization or suction means,
and preliminary heating means using electrothermal transducers, another heating element,
or a combination thereof. It is also effective for stable printing to provide a preliminary
discharge mode which performs discharge independently of printing.
[0096] Moreover, in each of the above-mentioned embodiments of the present invention, it
is assumed that the ink is a liquid. Alternatively, the present invention may employ
an ink which is solid at room temperature or less and softens or liquefies at room
temperature, or an ink which liquefies upon application of a use printing signal,
since it is a general practice to perform temperature control of the ink itself within
a range from 30°C to 70°C in the ink-jet system, so that the ink viscosity can fall
within a stable discharge range.
[0097] In addition, in order to prevent a temperature rise caused by heat energy by positively
utilizing it as energy for causing a change in state of the ink from a solid state
to a liquid state, or to prevent evaporation of the ink, an ink which is solid in
a non-use state and liquefies upon heating may be used. In any case, an ink which
liquefies upon application of heat energy according to a printing signal and is discharged
in a liquid state, an ink which begins to solidify when it reaches a printing medium,
or the like, is applicable to the present invention. In this case, an ink may be situated
opposite electrothermal transducers while being held in a liquid or solid state in
recess portions of a porous sheet or through holes, as described in Japanese Patent
Laid-Open No. 54-56847 or 60-71260. In the present invention, the above-mentioned
film boiling system is most effective for the above-mentioned inks.
[0098] According to the present invention as described above, by measuring density of an
ink dot or a line of a line pattern formed with ink discharged from a head and finding
the amount of ink discharged on the basis of the measured density, the amount of ink
discharged can be obtained instantly by each dot.
[0099] Further, by finding correlation between the amount of ink discharged and the density
of an ink dot formed by the discharged ink in advance, the amount of ink discharged
from an arbitrary nozzle can be easily found by referring to the correlation and the
measured density of the ink dot or the line formed by the ink discharged from the
nozzle.
[0100] Furthermore, it is possible to instantly obtain the density of the ink dot or the
line pattern by forming ink dots or a line pattern on a transparent plate, inputting
an image of them by using a camera while illuminating the ink dots or the line pattern
with light, and applying image processing to the input image.
[0101] Further, by using at least two nozzles whose discharging amounts are known, and finding
a calibration line showing relationship between the density of ink dot formed by an
ink discharged from the nozzles and the amount of ink discharged in advance, the amount
of ink discharged from an arbitrary nozzle under an arbitrary condition can be determined
from the calibration line and the density of an ink dot or a line of a line pattern
formed with the ink discharged from the arbitrary nozzle.
[0102] Further, in order to determine the amount of ink discharged from a nozzle in advance,
the weighing method or the absorbance method can be used, thereby the amount of ink
discharged from the nozzle can be correctly determined.
[0103] Furthermore, it is possible to measure densitys of a plurality of dots or lines of
a line pattern continuously by providing the XY stage or the X stage capable of moving
with respect to a camera which performs image processing on an ink absorbent medium.
Thereby, amounts of ink discharged from a plurality of nozzles of a printhead can
be measured continuously.
[0104] Furthermore, by providing an apparatus for measuring an amount of ink in an printing
apparatus, it becomes possible to feed back data on the discharged amount of ink obtained
in the measuring apparatus to the printing apparatus so that the data is used to control
an amount of ink to be discharged by a uniform amount. Thereby, printing quality can
be improved.
[0105] The present invention is not limited to the above embodiments and various changes
and modifications can be made within the spirit and scope of the present invention.
Therefore to appraise the public of the scope of the present invention, the following
claims are made.
1. A method of measuring an amount of ink discharged from an ink-jet type printhead in
a single discharging operation, said method comprising:
a density measuring step of measuring a density of an ink dot formed by an ink discharged
from the printhead on a predetermined medium; and
a determining step of determining an amount of ink discharged on the basis of the
density of the ink dot measured at said density measuring step.
2. The method according to claim 1, further comprising a preliminary measuring step of
finding correlation between an amount of ink discharged in a single discharging operation
and a density of an ink dot formed by the discharged ink on the basis of experiment
prior to said density measuring step.
3. The method according to claim 1, wherein the predetermined medium is a transparent
plate, and at said density measuring step, the density of the ink dot is measured
by analyzing light transmitted through the ink dot emitted by a light source which
is placed behind the transparent plate in image processing.
4. The method according to claim 1, further comprising a discharging amount adjusting
step of adjusting an amount of ink to be discharged so as to become a desired amount
on the basis of the amount of ink discharged determined at said determining step.
5. The method according to claim 4, further comprising a discharging step of discharging
an ink onto a printing medium after said discharging amount adjusting step.
6. A method of measuring an amount of ink discharged from an ink-jet type printhead in
a single discharging operation, said method comprising:
a preliminary measuring step of measuring an amount of ink discharged from each of
a plurality of ink-discharging nozzles of the printhead in a single discharging operation
under a predetermined condition in advance;
a first density measuring step of measuring densitys of ink dots made of ink discharged
from at least two different ink-discharging nozzles which discharge different amounts
of ink from each other out of the plurality of ink-discharging nozzles onto a predetermined
medium under the predetermined condition;
a calibration line generating step of generating a calibration line representing correlation
between an amount of ink discharged in a single discharging operation and a density
of an ink dot on the basis of data on the densitys of the ink dots, measured at said
first density measuring step, formed with the ink discharged from the at least two
ink-discharging nozzles and data on the amount of ink, measured at said preliminary
measuring step, discharged from the at least two ink-discharging nozzles;
a second density measuring step of measuring a density of an ink dot formed by an
ink discharged from an arbitrary nozzle of the printhead under an arbitrary condition;
and
a determining step of determining an amount of ink discharged from the arbitrary nozzle
under the arbitrary condition on the basis of the data on the density of the ink dot,
obtained at said second density measuring step, and the calibration line.
7. The method according to claim 6, wherein, at said preliminary measuring step, the
amount of ink discharged from each of the plurality of ink-discharging nozzles is
measured by a weighing method or an absorbance method.
8. The method according to claim 6, wherein the predetermined medium is a transparent
plate, and at said first and second density measuring steps, a density of an ink dot
is measured by analyzing light transmitted through the ink dot emitted by a light
source which is placed behind the transparent plate in image processing.
9. The method according to claim 6, further comprising a discharging amount adjusting
step of adjusting an amount of ink to be discharged so as to become a desired amount
on the basis of the amount of ink discharged determined at said determining step.
10. The method according to claim 9, further comprising a discharging step of discharging
an ink onto a printing medium after said discharging amount adjusting step.
11. An apparatus for measuring an amount of ink discharged from an ink-jet type printhead
in a single discharging operation, said apparatus comprising:
receiving means for receiving an ink discharged from the printhead;
density determining means for determining a density of an ink dot formed by the discharged
ink on the receiving means;
memory means for storing a calibration line representing correlation between an amount
of ink discharged and a density of an ink dot formed by the discharged ink on the
receiving means in a single discharging operation; and
operation means for finding an amount of the discharged ink on the basis of the density
of the ink dot determined by said density determining means and the calibration line.
12. The apparatus according to claim 11, wherein said density determining means includes
a camera for inputting an image of the ink dot and image processing means for analyzing
the image inputted by said camera.
13. The apparatus according to claim 12, wherein said receiving means is a transparent
plate, and the apparatus further comprises a light source for illuminating the ink
dot from behind the receiving means.
14. The apparatus according to claim 12, further comprising an XY stage for moving said
receiving means with respect to said camera in order to continuously measure densitys
of a plurality of ink dots formed on the receiving means automatically and continuously
finding amounts of ink discharged forming the plurality of ink dots.
15. The apparatus according to claim 11, further comprising adjusting means for adjusting
an amount of ink to be discharged from the printhead on the basis of the amount of
ink discharged found by said operation means.
16. A printing apparatus having a function of measuring an amount of ink discharged from
an ink-jet type printhead which prints by discharging ink from the ink-jet type printhead
in a single discharging operation, said apparatus comprising:
density determination means for determining a density of an ink dot formed by an ink
discharged from the ink-jet type printhead on a receiving medium for receiving the
discharged ink;
memory means for storing a calibration line representing correlation between an amount
of ink discharged and a density of an ink dot formed by the discharged ink on the
receiving medium in a single discharging operation; and
operation means for finding an amount of the discharged ink on the basis of the density
of the ink dot determined by said density determining means and the calibration line.
17. The printing apparatus according to claim 16, wherein said density determining means
includes a camera for inputting an image of the ink dot and image processing means
for analyzing the image inputted by said camera.
18. The printing apparatus according to claim 17, wherein said receiving medium is a transparent
plate, and the apparatus further comprises a light source for illuminating the ink
dot from behind the receiving medium.
19. The printing apparatus according to claim 17, further comprising an XY stage for moving
said receiving means with respect to said camera in order to continuously measure
densitys of a plurality of ink dots formed on the receiving medium automatically and
continuously finding amounts of ink discharged forming the plurality of ink dots.
20. The printing apparatus according to claim 16, further comprising adjusting means for
adjusting an amount of ink to be discharged from the ink-jet type printhead on the
basis of the amount of ink discharged found by said operation means.
21. A method of measuring an amount of ink discharged adopted by a printing apparatus
having an ink-jet type printhead, said method comprising:
a density measuring step of measuring a density of an ink dot formed by an ink discharged
from the printhead on a receiving medium for receiving the discharged ink; and
a determining step of determining an amount of ink discharged on the basis of the
density of the ink dot measured at said density measuring step.
22. The method adopted by a printing apparatus according to claim 21, further comprising
a preliminary measuring step of finding correlation between an amount of ink discharged
in a single discharging operation and a density of an ink dot formed by the discharged
ink on the basis of experiment prior to said density measuring step.
23. The method adopted by a printing apparatus according to claim 21, wherein the receiving
medium is a transparent plate, and at said density measuring step, the density of
the ink dot is measured by analyzing light transmitted through the ink dot emitted
by a light source which is placed behind the receiving medium in image processing.
24. The method adopted by a printing apparatus according to claim 21, further comprising
a discharging amount adjusting step of adjusting an amount of ink to be discharged
so as to become a desired amount on the basis of the amount of ink discharged determined
at said determining step.
25. The method according to claim 24, further comprising a discharging step of discharging
an ink onto a printing medium after said discharging amount adjusting step.
26. A method of measuring an amount of ink discharged adopted by a printing apparatus
having an ink-jet type printhead, said method comprising:
a preliminary measuring step of measuring an amount of ink discharged from each of
a plurality of ink-discharging nozzles of the printhead in a single discharging operation
under a predetermined condition in advance;
a first density measuring step of measuring densitys of ink dots made of ink discharged
from at least two different ink-discharging nozzles which discharge different amounts
of ink from each other out of the plurality of ink-discharging nozzles onto a receiving
medium for receiving ink under the predetermined condition;
a calibration line generating step of generating a calibration line representing correlation
between an amount of ink discharged in a single discharging operation and a density
of an ink dot on the basis of data on the densitys of the ink dots, measured at said
first density measuring step, formed with the ink discharged from the at least two
ink-discharging nozzles and data on the amount of ink, measured at said preliminary
measuring step, discharged from the at least two ink-discharging nozzles;
a second density measuring step of measuring a density of an ink dot formed by an
ink discharged from an arbitrary nozzle of the printhead under an arbitrary condition;
and
a determining step of determining an amount of ink discharged from the arbitrary nozzle
under the arbitrary condition on the basis of the data on density of the ink dot,
obtained at said second density measuring step, and the calibration line.
27. The method adopted by a printing apparatus according to claim 26, wherein, at said
preliminary measuring step, the amount of ink discharged from each of the plurality
of ink-discharging nozzles is measured by a weighing method or an absorbance method.
28. The method adopted by a printing apparatus according to claim 26, wherein the receiving
medium is a transparent plate, and at said first and second density measuring steps,
a density of an ink dot is measured by analyzing light transmitted through the ink
dot emitted by a light source which is placed behind the receiving medium in image
processing.
29. The method adopted by a printing apparatus according to claim 26, further comprising
a discharging amount adjusting step of adjusting an amount of ink to be discharged
so as to become a desired amount on the basis of the amount of ink discharged determined
at said determining step.
30. The method according to claim 29, further comprising a discharging step of discharging
an ink onto a printing medium after said discharging amount adjusting step.
31. A method of measuring an amount of ink discharged from an ink-jet type printhead in
a single discharging operation, said method comprising:
a density measuring step of measuring a density of a line of a line pattern formed
with an ink discharged from the printhead on a predetermined medium; and
a determining step of determining an amount of ink discharged on the basis of the
density of the line of the line pattern measured at said density measuring step.
32. The method according to claim 31, further comprising a preliminary measuring step
of finding correlation between an amount of ink discharged in a single discharging
operation and a density of an ink dot formed by the discharged ink on the basis of
experiment prior to said density measuring step.
33. The method according to claim 31, wherein the predetermined medium is a transparent
plate, and at said density measuring step, the density of the line of the line pattern
is measured by analyzing light transmitted through the line of the line pattern emitted
by a light source which is placed behind the transparent plate in image processing.
34. The method according to claim 31, further comprising a discharging amount adjusting
step of adjusting an amount of ink to be discharged so as to become a desired amount
on the basis of the amount of ink discharged determined at said determining step.
35. The method according to claim 34, further comprising a discharging step of discharging
an ink onto a printing medium after said discharging amount adjusting step.
36. A method of measuring an amount of ink discharged from an ink-jet type printhead in
a single discharging operation, said method comprising:
a preliminary measuring step of measuring an amount of ink discharged from each of
a plurality of ink-discharging nozzles of the printhead in a single discharging operation
under a predetermined condition in advance;
a first density measuring step of measuring densitys of ink dots made of ink discharged
from at least two different ink-discharging nozzles which discharge different amounts
of ink from each other out of the plurality of ink-discharging nozzles onto a predetermined
medium under the predetermined condition;
a calibration line generating step of generating a calibration line representing correlation
between an amount of ink discharged in a single discharging operation and a density
of an ink dot on the basis of data on the densitys of the ink dots, measured at said
first density measuring step, formed with the ink discharged from the at least two
ink-discharging nozzles and data on the amount of ink, measured at said preliminary
measuring step, discharged from the at least two ink-discharging nozzles;
a second density measuring step of measuring a density of a line of a line pattern
formed with an ink discharged from an arbitrary nozzle of the printhead under an arbitrary
condition; and
a determining step of determining an amount of ink discharged from the arbitrary nozzle
under the arbitrary condition on the basis of the data on the density of the line
of the line pattern, obtained at said second density measuring step, and the calibration
line.
37. The method according to claim 36, wherein, at said preliminary measuring step, the
amount of ink discharged from each of the plurality of ink-discharging nozzles is
measured by a weighing method or an absorbance method.
38. The method according to claim 36, wherein the predetermined medium is a transparent
plate, and at said first and second density measuring steps, a density of a line of
a line pattern is measured by analyzing light transmitted through the line of the
line pattern emitted by a light source which is placed behind the transparent plate
in image processing.
39. The method according to claim 36, further comprising a discharging amount adjusting
step of adjusting an amount of ink to be discharged so as to become a desired amount
on the basis of the amount of ink discharged determined at said determining step.
40. The method according to claim 39, further comprising a discharging step of discharging
an ink onto a printing medium after said discharging amount adjusting step.
41. An apparatus for measuring an amount of ink discharged from an ink-jet type printhead
in a single discharging operation, said apparatus comprising:
receiving means for receiving an ink discharged from the printhead;
density determining means for determining a density of a line of a line pattern formed
with the discharged ink on the receiving means;
memory means for storing a calibration line representing correlation between an amount
of ink discharged and a density of an ink dot formed by the discharged ink on the
receiving means in a single discharging operation; and
operation means for finding an amount of the discharged ink on the basis of the density
of the line of the line pattern determined by said density determining means and the
calibration line.
42. The apparatus according to claim 41, wherein said density determining means includes
a camera for inputting an image of the line of the line pattern and image processing
means for analyzing the image inputted by said camera.
43. The apparatus according to claim 42, wherein said receiving means is a transparent
plate, and the apparatus further comprises a light source for illuminating the line
of the line pattern from behind the receiving means.
44. The apparatus according to claim 42, further comprising an X stage for moving said
receiving means with respect to said camera in order to continuously measure densitys
of a plurality of lines of the line pattern formed on the receiving means automatically
and continuously finding amounts of ink discharged forming the plurality of lines
of the line pattern.
45. The apparatus according to claim 41, further comprising adjusting means for adjusting
an amount of ink to be discharged from the printhead on the basis of the amount of
ink discharged found by said operation means.
46. A method or apparatus for determining the amount of ink discharged by an ink jet head
by measuring the density of an ink dot formed by discharged ink.
47. A method or apparatus for determining the amount of ink discharged by an ejection
nozzle of an ink jet head by interpolation or extrapolation using the measured density
of an ink dot formed by at least one other nozzle.