[0001] The present invention relates to electrophoretic information displays (EPID) in general
and more particularly to apparatus which operates in conjunction with an EPID display
enabling such a display to operate with grey scale capability.
[0002] The prior art is replete with a number of various patents and articles concerning
electrophoretic displays. Such electrophoretic displays have been widely described
and disclosed in the prior art and essentially the assignee herein, Copytele Inc.,
of Huntington Station, New York has developed an electrophoretic display which has
an image area of approximately 28 x 21.6 cm (11 x 8 1/2 inches) and is designed to
be used either as a separate display or to be combined with other displays. The company
has the ability to combine as many as four such displays to create larger area displays.
The information on such displays can be changed either locally or remotely and can
be viewed at an angle of nearly 180 degrees. Such displays have been extremely high
resolution and can accommodate over 160,000 pixels within an image area of approximately
7.1 cm (2.8 inches) diagonally.
[0003] In regard to such displays, reference is made to U.S. Patent No. 4,655,897 issued
on April 7, 1987 entitled ELECTROPHORETIC DISPLAY PANELS AND ASSOCIATED METHODS to
Frank J. DiSanto and Denis A. Krusos and assigned to Copytele Inc., the assignee herein.
In that patent, there is described an electrophoretic display panel which includes
a planar transparent member having disposed on the surface a plurality of vertical
conductive lines to form a grid of wires in the Y direction. On top of the grid of
vertical lines, there is disposed a plurality of horizontal lines which are positioned
above the vertical lines and insulated therefrom by a thin insulating layer at each
of the intersection points. Spaced above the horizontal and vertical line pattern
is a conductive plate. The space between the conductive plate and the X and Y line
pattern is filed with an electrophoretic dispersion containing chargeable pigment
particles. When a voltage is impressed on the X and Y lines, pigment particles which
are located in the wells or depressions between the X and Y pattern are caused to
migrate towards the conductive plate and deposited on the plate in accordance with
the voltage applied to the X and Y conductors. There is described in that patent an
electrophoretic dispersion suitable for operation with the display as well as techniques
for fabricating the display. Hence, in this manner the displays can be fabricated
to contain large effective display areas while being relatively thin. These displays
are capable of high resolution and relatively low power consumption.
[0004] As indicated, the above noted patent and others include information concerning the
fabrication, operation and resolution of such displays.
[0005] As explained in U.S. Patent No. 4,833,464, issued on May 23, 1989 and entitled ELECTROPHORETIC
INFORMATION DISPLAY (EPID) APPARATUS EMPLOYING GREY SCALE CAPABILITY to Frank J. DiSanto,
et al., it is a problem with such displays to provide grey scale capability. Grey
scale capability is a well known term of the art and has been utilized for example
in regard to the description of television receivers and various other types of data
presentation, such as facsimile and so on. In the case of television receivers, the
response of the receiver can be visually determined by means of typical test patterns
such as those test patterns that were previously transmitted and displayed when, for
example, a television station goes off the air. Various television stations frequently
transmit such a pattern for the convenience of service technicians and so on. The
pattern apart from showing correct linearity, for example, also shows correct reproduction
of the background shading which can indicate proper frequency response. The correct
reproduction of the five color shades in the center target area of the test pattern
indicates proper mid-frequency responses.
[0006] As one can ascertain, such test patterns are associated with grey scale capability,
namely with the display of various grey levels as located between black and white.
Such grey scale capability is a desirable feature in conjunction with any type of
display. An electrophoretic display either presents a black or white type of representation
of an image which is conveniently referred to as dark or light. Basically, the color
of the image is a function of the color of the pigment particles and the color of
the suspension that they are suspended in. The display may be black and white, yellow
and black and so on.
[0007] There is a wide variety of many potential color combinations which can be employed
in regard to such displays. The above-noted U.S. Patent No. 4,833,464, describes apparatus
and techniques for grey scale operation for an electrophoretic display panel. The
apparatus includes circuitry which operates with a timing generator which produces
a plurality of different time duration output wave forms which are applied to the
X and Y drive as associated with the display. In this manner, by applying a set of
voltages for a given duration time interval, a display is provided which results in
the incomplete removal of pigment from associated selected pixels. Hence, those pixels
appear darker than surrounding pixels but not as dark as the pure dye solution as
associated with the display. Thus, the amount of pigment removed and hence the darkness
of each pixel is a function of the time duration during which the appropriate voltage
is applied to the rows and columns of the display. The timing generator can cause
different pixels as displayed to have different darknesses or grey scale values by
varying the time during which the voltage is applied to the display.
[0008] In European application 0199272 there is described a means for generating grey scale
levels strictly according to the colour content of a video image. Specifically there
is described a colour to monochrome image transformation which transforms each colour
area of an original image into a corresponding area of monochromation image having
a particular pattern of light and dark dots corresponding to and representing the
original colour of the area. This does not however, allow the user to select grey
scale according to the user's preference in order to highlight an area, or to underline
an area, or to provide grey scale capability in a display, strictly according to the
user's requirements and independently of the data in the display.
[0009] It is therefore an object of the present invention to provide a new or improved electrophoretic
display having grey scale capability.
[0010] It is a further object of the present invention to provide an electrophoretic display
apparatus which has grey scale capability and which operates to modulate the area
about each character or the area within each character on a display.
[0011] According to one aspect of the invention we provide apparatus for providing grey
scale capability for an electrophoretic information display (EPID), wherein said electrophoretic
display is an X-Y addressable display with each X-Y coordinate indicative of a given
column and row intersection, with each X-Y coordinate defining a pixel, which pixel
when energized provides a different intensity display as compared to a non-energized
pixel comprising, characterized in that means are coupled to said display for impressing
upon said display a plurality of predetermined digital patterns that are independent
of data or an image written on said display to cause said pixels in said display to
be energized with respect to other pixels in said display according to a selected
one of such patterns, said energized pixels being of same intensity as those pixels
of an image on said display and each of said predetermined digital patterns being
distinct and arranged in repetitive configurations that produce different grey scale
levels, whereby the area about said image is effectively modulated according to said
pattern to vary the contrast of said image with respect to the display background.
[0012] Thus grey scale operation at different shades of grey can be provided on the electrophoretic
display by means of area modulation. Area modulation can be used to shade either the
foreground, the background or both the foreground and the background. Such electrophoretic
displays, as other displays, portray information by writing in two different colours
or shades of the same colour. These, of course, can be referred to as black or white,
although many other colour combinations are available as indicated above. Thus, in
an electrophoretic display, the normal background colour is the colour of the pigment
used in the display and the written characters and graphics are generated by removing
pigment from the appropriate areas. In the reverse or inverse video mode the pigment
is removed from the background while pigment is retained in the areas of the characters
or graphics. This is the same difference, for example, between a negative and positive
in photography.
[0013] By performing area modulation by writing a pattern of either black or white pixels
in either the background, foreground or both, permits generation of shades of grey.
It is also understood that area modulation can be used with any relatively high resolution
display to in fact provide a grey scale capability for the display.
[0014] In accordance with a second aspect of the invention we provide a method of providing
grey scale capability for electrophoretic information display (EPID) of the type employing
pixel selection, characterised by the steps of:
storing a plurality of digital patterns with each said digital pattern being distinct
and arranged in repetitive configurations that produce different grey scale levels,
said stored patterns, when applied to an electrophoretic display, to cause said pixels
in said display to be energized with respect to other pixels in said display in accordance
with a desired grey scale level, and with each said energized pixel being of same
intensity as those pixels of an image on said display, and selecting a stored pattern
for application to said display by means independent of data or an image written on
said display, to cause said display to exhibit said grey scale level whereby the area
about said image is effectively modulated according to said pattern to vary the contrast
of said image with respect to the display background.
Figure 1 is a side plan view of an electrophoretic display (EPID) employed in this
invention;
Figure 2 is a perspective plan view of an electrophoretic display panel showing a
given number of grid and cathode lines;
Figure 3 is a graph depicting a character block displayed on a conventional black
and white display;
Figure 4 depicts a character displayed with a predetermined area modulated background
pattern;
Figure 5 shows still another area modulated pattern;
Figure 6 is a diagram showing still another pattern;
Figure 7 is a diagram showing still another pattern;
Figure 8 is a diagram showing an alternate pattern;
Figure 9 is a diagram showing still another alternate pattern;
Figure 10 is a diagram of a character block showing an alternate background pattern;
Figure 11 is a diagram of a character block showing an alternate background pattern;
Figure 12 is a schematic diagram partially in block form showing a circuit for deriving
a grey scale value for an electrophoretic display employing area modulation;
Figure 13 shows an OR gate employed in this invention;
Figure 14 shown an AND gate employed in this invention;
Fig. 15 shows a logic circuit for providing grey background or characters; and
Fig. 16 shows a logic circuit for providing the character and background features.
[0015] Referring to Figure 1, there is shown a side view of a typical electrophoretic display
10. The display 10 of Figure 1 is filled with an electrophoretic solution 20 which
includes light colored pigment particles suspended in a dark dye solution. For examples
of such solutions and techniques, reference is made to the above cited U.S. Patent
No. 4,655,897.
[0016] It is also understood that the display can consist of a dark pigment suspended in
a light solution and so on. As seen from Figure 1, the display contains a front glass
sheet or viewing surface 21. The eye of the viewer 15 is shown viewing the front of
the display via the glass sheet 21. Superimposed upon the glass sheet 21 by suitable
etching techniques are columns 23 and rows 25. The rows are made from an extremely
thin layer of idiumtin-oxide (ITO) while the columns are made from thin layers of
aluminum or other suitable metal. These patterns, as indicated, are provided in extremely
thin layers and constitute an XY matrix. The layers of ITO as can be seen by reference
to the above-noted patent are relatively thin being approximately 3000 Angstroms thick.
The grid or columns and the rows or cathodes (XY) are spaced from one another and
insulated from one another by means of an insulating layer 22. While the grids and
cathodes have been specified in terms of rows and columns, it is understood that the
terms can be interchanged as desired. Each of the grid and cathode intersections are
associated with a pigment well 24. These wells contain electrophoretic solution which
is in the cavity 20. The columns and rows are separated from a back electrode 26 which
is also fabricated on a sheet of glass 27 and constitutes a thin layer of ITO. The
spacers such as 12 and 23 can be implemented in many different ways and essentially
serve to mechanically separate the display or panel 10. In operation of the display,
the pigment particles contained in the electrophoretic solution 20 are brought forward
towards the viewing surface in order to fill the wells formed between the rows and
columns. Once a well such as 24 is filled, the voltage on the rows and columns and
rear cover is then set, such that the wells remain filled, but pigment spaced between
the rear cover and the columns are swept onto the rear cover plate 26. At viewing
side 21, one sees the color of the pigment in the wells. By selectively applying voltages
to the rows and columns, the pigment in the individual wells 24 (at the intersection
of the rows and columns selected) is forced out of the wells exposing the dye solution
and making that intersection (pixel) dark. The removal of the pigment from the wells
is not instantaneous but requires a period of time which depends upon the dimension
of the cell or display, the fluid components, and the various supply voltages. The
above-noted U.S. Patent No. 4,833,464 discusses the control of the voltages and the
duration of the same to control grey scale operation. The techniques for performing
area modulation in conjunction with an electrophoretic display will be described in
detail.
[0017] Referring to Figure 2, there is shown a plan view of an enlarged representation of
an electrophoretic display cell or panel according to Figure 1. As seen in Figure
2, each well is accommodated between an intersection of a column metal layer 23, which
is insulatively separated from a row layer of ITO 25. The well 24 forms a pixel area
which is indicative of an XY intersection of the ITO display. Thus, as one will understand,
the object of the present invention is to provide grey scale capability and this grey
scale capability is performed in a high resolution electrophoretic display. It is
noted that the resolution of the display has to be high to accommodate area modulation
and derive the particular aspects and benefits of this technique.
[0018] Referring to Figure 3, there is shown a representation of the letter E as for example,
displayed on a conventional electrophoretic display. In regard to the following discussion,
it will be indicated that the states of the electrophoretic display, for example as
shown in Figure 3, are black and white. It is understood that the letter E will be
visible if the pixels were darker than the background.
[0019] As indicated above, area modulation is accomplished by writing a pattern of either
black or white pels in either the background, the foreground or both. The high resolution
provided by an electrophoretic display permits the use of area modulation to generate
shades of grey. Area modulation can be employed with any relatively high resolution
display. Appearance of the grey scale due to area modulation is a physiological consequence
of the resolution of the human eye. The effect is obtained when the angle subtended
by the black and white pels as seen by the viewer, approaches the resolution of the
human eye. In a typical electrophoretic display as provided by the assignee herein,
Copytele Inc., a resolution of 200 lines per inch in both the horizontal and vertical
directions is available.
[0020] This resolution is ideal for producing grey scale by means of area modulation. On
an electrophoretic display with this resolution, characters are written using a character
block of 16 pixels horizontally and 24 pixels vertically. As seen in Figure 3, both
the horizontal and vertical directions are indicated by means of gradations as 30
and 31. These gradations encompass an area which is indicative of a pixel. Hence,
as one can see, there are essentially 16 boxes or pixels representing the top line
in the image area 32 depicted in Figure 3. Thus, again referring to Figure 3, it is
indicated that with the above-noted resolution of 200 lines per inch in both the horizontal
and vertical directions, character blocks consisting of 16 pixels or pels horizontally
and 24 pels vertically are typical. This character block yields a display with 25
lines of 80 characters each on a display whose dimensions are approximately 6.4 x
3.2 inches. Thus, as one can ascertain from Figure 3, there is shown the character
E which is represented in black on a relatively white background. It is, of course,
understood that the inverse of this image could also be provided by the electrophoretic
display.
[0021] Referring to Figure 4, there is again shown the character E within the character
block 32 having a 50 percent grey background. Essentially, the character E is the
same as shown in Figure 3 but the background consists of alternate pixels of black
and white as can be seen, for example, from Figure 4. Across the top line 40, the
16 pixels are indicative of white, black, white, black and so on. On line 41, the
pattern is black, white, black, white and so on. This pattern then continues to alternate
down and across the display so that it alternates as to the 16 horizontal pixels and
the 24 vertical pixels. The background appears grey when the image is viewed at a
distance where the individual pels are unresolved. Because of this property, the number
of grey shades obtainable via area modulation is again a function of the display's
resolution, the size of the character and the viewing distance. As one can ascertain,
the background area is modulated accordingly to produce patterns which have grey scale
capability due to the nature of the modulation technique.
[0022] Referring to Figure 5, there is shown the character block which now possesses an
area modulated background which is 93.25 percent black. This is obtained by formulating
each horizontal line within the character block, all within the display area by means
of a particular Hex code. As seen in Figure 5, line 50 is indicative of the Hex code
EE where black is equal to binary one and white is equal to binary 0. Based on the
display format shown in Figure 5, in order to obtain a background which his 93.25
percent black, one modulates the display lines as follows. The first line 50 as seen
is BBBWBBBWBBBWBBBW (Hex EE). The next three lines 51, 52, and 53 are all black or
all B (Hex FF). The fourth line is BWBBBWBBBWBBBWBB (Hex BB). At the right of each
line, there is shown the Hex code for the line. As one can see from the Hex code notation,
it is a repetitive pattern which specifies the display background as in Figure 5 to
obtain a background which is 93.25 percent black. The line pattern for the display
of Figure 5 is HEX, EE, FF, FF, FF, BB, FF, FF, FF and repeats for the 24 lines.
[0023] Referring to Figure 6, there is shown an area modulated background or character block
which is 87.5 percent black. The Hex line values are shown at the right hand side
to denote the repetitive pattern. As one can see from Figure 6, line 61 is BWBBBWBBBWBBBWBB
which is Hex code BB. Line 62 is all black which is Hex FF. Line 63 is BBBWBBBWBBBWBBBW
which is hex code EE. Line 64 is all black as Hex code FF.
[0024] Referring to Figure 7, there is shown an area modulated background pattern which
is 62.5 percent black. The Hex code is shown at the right and is a relatively simple
repeating code with the first line 70 being WBBBWBBBWBBBWBBB or Hex 77. Line 71 is
BBWBBBWBBBWBBBWB which is Hex DD and then the pattern repeats as Hex 77, DD, 77, DD,
77, DD...etc.
[0025] Referring to Figure 8, there is shown a pattern which is 50 percent black and has
a simple repeat as line 80 is BWBWBWBW... etc. Line 81 is WBWBWB etc. which respectively
denotes the Hex code of AA and 55, which code repeats for the 24 lines.
[0026] Referring to Figure 9, there is shown an area modulated display or character block
which is 37.5 percent black. The Hex code is shown on the right as line 90 is Hex
code AA as for example indicative of line 80 of Figure 8, while line 91 is Hex code
44 which is WBWWWBWWWBWWWBWW. Line 92 is the same as line 90 (AA) while line 93 is
Hex code 11 or WWWBWWWBWWWBWWWB. The code then alternates as seen in Figure 9.
[0027] Referring to Figure 10, it depicts a character block or display having 25 percent
black background. The Hex code is shown on the right hand side for each line.
[0028] Referring to Figure 11, it shows a display or character block, the Hex code again
at the right exhibiting a 12.4 percent black background. As one can ascertain, the
above-noted figures essentially depict six different patterns which six patterns will
yield seven different shades of grey when viewed at normal viewing distance on a 200
x 200 line per inch electrophoretic display. These patterns coupled with black and
white yield a system with nine shades of grey. However, in practice, a background
of 12.5 percent black can be omitted as exhibiting a small difference from white.
The patterns as one can easily ascertain, which are distinct are shown in Figures
5-11. These figures represent various patterns which yield different shades of grey
when viewed at a normal viewing distance on a 200 x 200 line per inch electrophoretic
display.
[0029] The system as shown with a 200 line resolution including black and white can produce
eight different effective shades of grey. The patterns used to achieve area modulation
in a character type or graphics type display when the graphics are formed using special
characters must be a factor of the character block. For example, in a display using
a character block which is 16 pixels wide and 24 pixels high, the width of the area
modulated pattern must be a factor (divisor) of 24 and the height of the pattern must
be a factor (divisor) of 16. The figures shown in the above-noted application, as
indicated for example in Figure 3, are patterns which are designed for a 16 x 24 pel
character block. The figures show patterns which have increasingly more white (less
grey), however, the actual grey shade that the human eye perceives is dependent upon
many factors including display type, ambient lighting, color and other factors. It
may be necessary to have unequal increments in the percentages of black and white
in successive patterns to generate scales which are subjectively more and more grey.
[0030] There are many techniques as one can imagine for accommodating area modulation which
can be implemented simply by using registers and appropriate gating modules.
[0031] Displays using shades of grey require that an attribute which describes the image
foreground and background colors be designed for each character. The attribute length
depends on the total number of different color combinations required. For example,
if only one intermediate shade of grey is required between black and white then there
are only six combinations of foreground/background colors. These six states are most
readily encoded using 4 bits. Bit 0 and 1 specify the foreground color while bits
2 and 3 define the background color. In typical display systems, a byte is devoted
to the attribute even though not all 64 states definable by 8 bits are used. The implementation
of such a system can be done in a variety of ways.
[0032] Simple implementation for generating a grey background is to OR the pel data and
the selected AM pattern (Black = binary 1 and White = binary 0). This can be done
in real time as the pel data and the character data is loaded into shift registers
or into the drive circuitry. In systems which use a pixel memory it can be done as
the pel data is generated or is loaded into the pixel memory. To make the characters
or graphics a shade of grey, the procedures described can be used except that the
"OR" function is replaced with an "AND" function. In inverse video, the function used
to obtain a grey background is the AND function between the pixel data and the amplitude
modulated pattern. To make the characters grey in inverse video, one would employ
the OR function.
[0033] Referring to Figure 12, there is shown a circuit configuration in block form for
an electrophoretic display panel 10 which is associated with area modulation as described
above. Of course, it is understood that the cathodes and grids while described previously
in the XY planes can be reversed whereby the cathode lines can be arranged in the
Y plane with the grid lines in the X plane or vice versa. As one can see from Figure
12, each Y line such as 30 and 31 is associated with suitable drive amplifiers 32
and 33, where each X line such as lines 34 and 35 are associated with suitable amplifiers
36 and 37. It is of course seen in Figure 12, that the dots or dashes between amplifiers
36 and 37 and 32 and 33 are employed to indicate a plurality of additional individual
amplifiers indicative of a large number of lines. In this manner, by applying proper
biasing potentials to respective amplifiers, one can cause pigment particles to migrate
at any intersection between the X and Y matrix as formed by the associated grid and
cathode lines. Thus, based on the X and Y matrix, one can therefore produce any alphanumeric
character. For such displays with a large plurality of intersections or pixels, one
can provide graphic data such as a television picture and types of other displays
on the display panel 10. The display which is the electrophoretic display is provided
with high resolution based on the technique of fabricating line patterns and based
on presently available display techniques. The driver amplifiers 32 and 33 and 36
and 37 are fabricated by typical integrated circuit techniques and may for example
by CMOS devices, which are well known and many of which are available as conventional
integrated circuits. As indicated, the resolution of the electrophoretic display panel
is high based on modern integrated circuit techniques and including the fabrication
techniques employed in conjunction with such displays. It is anticipated that the
resolution of such displays can be as high as 40,000 dots per square inch. As seen
from Figure 12, the Y amplifier such as 32 and 33 are coupled to a Y address register
41. The address register 41 is a well known component consisting of various conventional
decoding devices including buffer registers and so on for the storage of data and
interfacing with the various columns associated with display 10. In a similar manner
the amplifiers 36 and 37 have inputs coupled to an address module 40 which is similar
to module 41 and operates to provide the Hex address information for the XY intersections
provided by the display. Means for addressing an XY matrix is solved by many typical
circuit solutions in the prior art and such decoders as the Y address register 41
and the X address register 40 are well known components in the prior art.
[0034] Both the X and the Y address registers are coupled to master decode module 50 which
operates to decode data and to generate the X and Y addresses for such data as is
conventionally known.
[0035] Coupled to the decode module 50 which again may be a typical microprocessor or another
programmed device is an area modulation memory 51. The area modulation memory 51 contains
in storage suitable digital patterns, such as for example the Hex codes as shown in
Figure 4-11 which will enable one to produce a display according to a desired grey
background. The stored data as indicated is associated with 4 bits which determine
the darkness or content of both the background and foreground depending upon whether
one wants to introduce the grey in the foreground or to introduce the grey in the
background. The area modulation memory contains the patterns as shown in the above-noted
figures to enable one to provide 6 or more levels of grey associated with a particular
display and according to the preference of the user. It is, of course, indicated that
each line of the display can be modulated by means of the code contained in memory
51 to thereby produce a uniform grey or other background for the entire display. In
a similar manner, one can also modulate each character block in a different manner
or modulate each line in a different manner or a portion of the display to produce
various grey formats throughout the display. This can enable one to highlight certain
regions of the display or certain areas of the displayed text with respect to the
other areas and according to the intensity of the foreground or background. The decode
module 50 is also coupled to a character generator 52 which character generator is
a conventional component. The character generator 52 is coupled to a keyboard 53.
The character generator 52, the decoder 50 and the keyboard 53 may be part of a conventional
computer system such as a PC system. There is another path shown in Figure 12, whereby
there is a data receiver 57 which is capable of receiving data from a typical telephone
line or other transmission medium. This data receiver may be a conventional modem.
The output of the data receiver is coupled to an analog to digital converter 56 for
transforming the analog signals at the input to digital signals at the output of the
analog-to-digital converter 56. The analog-to-digital converter 56 is associated with
a digital signal pixel generator 58 which operates in conjunction with the master
decoder 50 to allow one to perform area modulation at various pixel sites as desired.
The output of the decoder 50 is also coupled to the X address register and the Y address
register 40 and 41. The area modulation memory 51 is shown coupled to the decoder
50, but can of course be part of the microprocessor memory where a certain section
will be reserved for the different area modulation background codes. As shown in Figure
12, the module designated as grey scale select 60 is coupled to the area modulation
memory 51. The module 60 decodes the particular grey scale request which data may
be forwarded to the module 60 by means of the character generator 52 or by means of
the decoder 50. In this manner, the system by decoding the transmitted data would
automatically determine what grey scale is to be utilized for a particular display.
This can be automatically done by means of suitable decoders or can be implemented
at the preference of the user. As shown in Figure 12, the character generator 52 is
also coupled to the grey scale select module 60 and a user while viewing an image
can go ahead and select the grey scale value desired and according to the preference
of the user. As one can immediately ascertain from Figure 12, area modulation can
be simply implemented. One technique of implementing the area modulation is that the
decoder or microprocessor 50 combines the area modulation code as stored in the area
modulation memory with the data code. For example, if black is equal to 1 and white
is equal to 0 then an "AND" or "OR" function can be used. In the OR function, whenever
a pixel does not contain data, the pixel would receive the exact binary digit indicative
of the background code. Where a pixel does contain data, the output will be a 1 if
the data is a 1. If the data is 0 and the background is a 1, the output would also
be a 1 according to the area modulation pattern as stored. Thus, the OR function provides
a full black or dark character with the selected grey background as stored in the
area modulation memory 51. Thus, the patterns depicted in the above-noted Figures
5-11 can be combined with he data pattern, to provide AND and OR functions or both
as will be further explained. To present the characters or graphics with a desired
shade of grey, the procedures described above can be used except the OR is replaced
with an AND function.
[0036] In this manner, both the data and the area modulation bit must be the same in order
to produce a black spot at the output. If they are not the same then the color of
the pixel remains white. As one can see, one will produce a character having a different
grey scale which is presented on an all white or in the case of a negative application
on an all black background. In an inverse video mode the function used to obtain a
grey background is the AND function occurring between the pixel data and the stored
area modulation pattern. To make the characters grey in an inverse video mode, one
would employ the OR function between a grey background pattern and a pixel data pattern.
As indicated above and briefly described, either the characters (foreground) or the
background of a display can have grey scale. Both these options and the no grey scale
option can be readily generated by means of simple combinatorial circuits.
[0037] Referring to Figure 13, no grey scale requires no gating. The grey background is
accomplished by OR gating the character data bit stream with the grey scale pattern
bit stream as shown in Figure 13. Thus, as indicated in Figure 13, there is shown
an OR gate 70 with one input designated as CHAR representative of the character bit
stream and the other input designated as the grey bit steam.
[0038] As one can ascertain, the grey bit stream would be that stream or data which has
been defined in conjunction with Figures 5-11.
[0039] Referring to Figure 14, there is shown an AND gate 71 having one input designated
as by CHAR and indicative of the character bit stream and the other input receiving
the grey bit stream as again shown in the above-noted figures. The output of the AND
gate 71 is directed to the display or to the display drivers as is the output of gate
70. The grey characters are generated by the AND gate 71 which will produce grey character
on a constant background. Typically, the color of each character can be described
by a number of additional bits which are designated as attribute bits or an attribute
byte. This set of bits or byte are normally required for each character to be displayed.
The number of bytes of attribute data could be reduced by means of many different
schemes which are not pertinent to this aspect of the invention. For example, an attribute
byte with the following bit interpretations can be employed for generating grey scale
displays.
- 00000000
- no grey scale (black characters on white.
- 00000001
- grey background with black characters.
- 00000010
- grey characters with white background.
[0040] It is noted that in the above examples only 2 bits, as for example, the first and
second bits are needed to generated the grey display. The other bits typically are
used to specify the shade of grey desired. For simplicity, assume the desired grey
shade has been selected and will be used when grey is required. With these assumptions
and the example attribute code specified above, only a simple logic circuit is required
to generate the required bit stream.
[0041] Referring to Figure 15, there is shown a logic circuit capable of generating an output
signal for the display which provides a grey background or a grey character as controlled
by the attribute bits. As seen in Figure 15, the attribute bits designated as A0 and
Al define the type of display. For example, 00 is no grey, 01 is a grey background
and 10 is a grey character. As one can see, the character bit stream is directed to
a 3 input AND gate 80 and is also directed to a 2 input AND gate 81. The grey bit
stream is directed to one input of an OR gate 82 and to one input of the AND gate
81.
[0042] In this manner, as one can ascertain, the attribute bits which are A0 and Al are
applied to inverters 83 and 84. The output of inverter 83 is directed to one input
of AND gate 80 and one input of AND gate 85. The output of inverter 84 is applied
to one input of AND gate 80 and to one input of AND gate 86. The output of OR gate
82 is coupled to one input of AND gate 86 while the output of AND gate 81 is coupled
to input of AND gate 85. As seen, the AND gates 85 and 86 also receive the attribute
bits which are the uninverted bits. The outputs of the three AND gates 85, 86 and
80 are coupled to three inputs of an output OR gate 87, which supplies the output
display bit stream. For the combination of attribute bits, the bit streams are suitably
directed through appropriate gates to provide a grey background with a black character,
to provide no grey, or to provide a grey character on a light background. The logic
implemented by the circuit should be well understood by those skilled in the art.
[0043] Referring to Figure 16, there is shown a logic arrangement which based on the attribute
bit table shown will produce either no grey, a grey background, a grey character,
grey background of a given intensity or a grey background of another intensity specified
as grey No. 2. Thus, as seen in the Figure 16, the attribute bits Al and A0 can combine
to produce no grey, a grey 1 background with black characters, grey No. 2 with a white
background, grey No. 1 background with grey No. 2 characters. Thus, the logic circuit
shown in Figure 16 defines a simplified logic circuit which is predicated on using
either a grey pattern of a first intensity for the background and another grey pattern
of a different intensity for the foreground and so on. These are indicated as a grey
No. 1 pattern and a grey No. 2 pattern. Both of these patterns are typical of those
patters, for example, shown in Figures 5-11 as described above. Again the character
bit stream is inserted into the circuit with the attribute bits A0 and A1 having the
binary characteristics depicted in the table of Figure 16.
[0044] In a similar manner, the circuit of Figure 16 has four output AND gates designated
as 90, 91, 92 and 93 with gate 90 being a no grey gate, gate 91 producing the grey
1 output as a background, gate 92 producing the grey 2 character and gate 93 enabling
one to provide a grey 1 background and a grey 2 character. A description of each of
the individual gates in the uninverted state as for example, gate 93 receives the
Al uninverted as does gate 92, while gates 91 and 90 receive the Al inverted signal.
One can immediately ascertain the operation of the above-described circuit by referring
to Figure 16.
1. Apparatus for providing grey scale capability for an electrophoretic information display
(EPID), wherein said electrophoretic display is an X-Y addressable display with each
X-Y coordinate indicative of a given column and row intersection, with each X-Y coordinate
defining a pixel, which pixel when energized provides a different intensity display
as compared to a non-energized pixel comprising, characterised in that
means are coupled to said display for impressing upon said display a plurality
of predetermined digital patterns that are independent of data or an image written
on said display to cause said pixels in said display to be energized with respect
to other pixels in said display according to a selected one of such patterns, said
energized pixels being of same intensity as those pixels of an image on said display
and each of said predetermined digital patterns being distinct and arranged in repetitive
configurations that produce different grey scale levels, whereby the area about said
image is effectively modulated according to said pattern to vary the contrast of said
image with respect to the display background.
2. The apparatus according to Claim 1, characterised in that said pixel when energized,
causes a dark intensity to be displayed as compared to a lighter intensity when not
energized, with said darker intensity corresponding to a black level and with said
lighter intensity corresponding to a white level.
3. The apparatus according to Claim 1, characterised in that said digital pattern is
impressed on said display by means of AND logic means to cause characters as written
on said display to exhibit said grey scale level with respect to the background of
said display.
4. The apparatus according to Claim 1, characterised in that said digital pattern is
impressed on said display by means of OR logic means to cause said background to exhibit
said grey scale level with respect to characters on said display.
5. The apparatus according to Claim 1, characterised in that said means further includes
logic means operative to cause both characters written into said display and said
background of said display to be energized according to said digital pattern and in
accordance with said desired grey scale level.
6. The apparatus according to Claim 1, characterised by including memory means for storing
therein a plurality of digital patterns each one indicative of a different desired
grey scale level, and
means coupled to said memory means for selecting any desired one of said stored
digital patterns for application to said display.
7. The apparatus according to Claim 6, wherein said electrophoretic display is a high
resolution display.
8. A method of providing grey scale capability for an electrophoretic information display
(EPID) of the type employing pixel selection, characterised by the steps of:
storing a plurality of digital patterns with each said digital pattern being distinct
and arranged in repetitive configurations that produce different grey scale levels,
said stored patterns, when applied to an electrophoretic display, to cause said pixels
in said display to be energized with respect to other pixels in said display in accordance
with a desired grey scale level and with each said energized pixel being of same intensity
as those pixels of an image on said display and
selecting a stored pattern for application to said display, by means independent of
data or an image written on said display, to cause said display to exhibit said grey
scale level whereby the area about said image is effectively modulated according to
said pattern to vary the contrast of said image with respect to the display background.
9. The method according to Claim 8, characterised in that said energized pixels are background
pixels to provide a grey background with respect to a different intensity character.
10. The method according to Claim 8, characterised in that said energized pixels are character
pixels to provide a grey character with respect to a different intensity background.
11. The method according to Claim 10, characterised in that said different intensity background
is indicative of white.
12. The method according to Claim 10, characterised in that said stored digital patterns
are at least six patterns indicative of six different grey scale levels.
13. The method according to Claim 10, characterised in that there is included the step
of "OR"ing said selected pattern with a character pattern prior to applying said character
pattern to said display to display a given intensity character on a background of
said selected grey scale level.
14. The method according to Claim 10, characterised in that there is included the step
of "AND"ing said selected pattern with a character pattern prior to applying said
character pattern to said display to display a given intensity background having a
character impressed thereon of said selected grey scale level.
1. Vorrichtung zur Schaffung eines Graustufungsvermögens für eine elektrophoretische
Informationsanzeige (EPID), wobei besagte elektrophoretische Anzeige eine X-Y-adressierbare
Anzeige ist, in der jede X-Y-Koordinate einen gegebenen Schnittpunkt zwischen Spalten
und Zeilen bezeichnet und jede X-Y-Koordinate ein Bildelement definiert, das bei Erregung
eine Anzeige anderer Intensität ergibt als ein nichterregtes Bildelement, dadurch
gekennzeichnet, daß
an besagte Anzeige Mittel zum Aufdrücken von mehreren vorgegebenen Digitalstrukturen
auf besagte Anzeige angekoppelt sind, die unabhängig von den Daten oder einem auf
besagte Anzeige geschriebenen Bild sind und die Erregung besagter Bildelemente in
besagter Anzeige in bezug auf andere Bildelemente in besagter Anzeige gemäß einer
gewählten derartigen Struktur veranlassen, wobei besagte erregte Bildelemente die
gleiche Intensität haben wie jene Bildelemente eines Bildes auf besagter Anzeige und
jede besagte vorgegebene Digitalstruktur verschiedenartig und in sich wiederholenden
Konfigurationen angeordnet ist, die unterschiedliche Graustufen ergeben, und wobei
die Fläche um besagtes Bild zur Variierung des Kontrastes des besagten Bildes in bezug
auf den Anzeigehintergrund gemäß besagter Struktur wirksam moduliert wird.
2. Vorrichtung nach Anspruch 1, dadurch gekennzeichnet, daß besagtes Bildelement bei
Erregung eine dunkle Intensität im Vergleich zu einer helleren Intensität im nicht-erregten
Zustand zur Anzeige bringt, wobei besagte dunklere Intensität einer Schwarzstufe und
besagte hellere Intensität einer Weißstufe entspricht.
3. Vorrichtung nach Anspruch 1, dadurch gekennzeichnet, daß besagte Digitalstruktur mit
Hilfe von UND-Schaltungsmitteln so auf besagte Anzeige aufgedrückt ist, daß die auf
besagte Anzeige geschriebenen Zeichen besagte Graustufe in bezug auf den Hintergrund
besagter Anzeige aufweisen.
4. Vorrichtung nach Anspruch 1, dadurch gekennzeichnet, daß besagte Digitalstruktur mit
Hilfe von ODER-Schaltungsmitteln so auf besagte Anzeige aufgedrückt ist, daß besagter
Hintergrund besagte Graustufe in bezug auf Zeichen auf besagter Anzeige aufweist.
5. Vorrichtung nach Anspruch 1, dadurch gekennzeichnet, daß besagte Mittel weitere Schaltungsmittel
umfassen, die gemäß besagter Digitalstruktur und je nach besagter gewünschter Graustufe
sowohl die Erregung von auf besagte Anzeige geschriebenen Zeichen als auch die Erregung
besagten Hintergrundes besagter Anzeige veranlassen.
6. Vorrichtung nach Anspruch 1, dadurch gekennzeichnet, daß Speichermittel zur Speicherung
von mehreren jeweils eine andere Graustufe andeutenden Digitalstrukturen und
mit besagten Speichermitteln in Verbindung stehende Mittel zur Wahl einer beliebigen
gespeicherten Digitalstruktur zwecks Anwendung in besagter Anzeige vorgesehen sind.
7. Vorrichtung nach Anspruch 6, dadurch gekennzeichnet, daß besagte elektrophoretische
Anzeige eine hochauflösende Anzeige ist.
8. Verfahren zur Erstellung des Graustufungsvermögens für eine mit Bildelementwahl arbeitende
elektrophoretische Informationsanzeige (EPID), gekennzeichnet durch die folgenden
Schritte:
Speicherung von mehreren Digitalstrukturen, wobei jede besagte Digitalstruktur verschiedenartig
und in sich wiederholenden Konfigurationen angeordnet ist, die unterschiedliche Graustufen
ergeben und besagte gespeicherte Strukturen bei Anlegen an eine elektrophoretische
Anzeige die Erregung besagter Bildelemente in besagter Anzeige in bezug auf andere
Bildelemente in besagter Anzeige gemäß einer gewünschten Graustufe veranlassen und
jedes besagte erregte Bildelement die gleiche Intensität hat wie jene Bildelemente
eines Bildes auf besagter Anzeige, und
Wahl einer gespeicherten Struktur zur Anlegung an besagte Anzeige mit von den Daten
oder einem auf besagte Anzeige geschriebenen Bild unabhängigen Mitteln, um besagte
Anzeige zur Vorbringung der besagten Graustufe zu veranlassen, wobei die Fläche um
besagtes Bild zur Variierung des Kontrastes des besagten Bildes in bezug auf den Anzeigehintergrund
gemäß besagter Struktur wirksam moduliert wird.
9. Verfahren nach Anspruch 8, dadurch gekennzeichnet, daß besagte erregte Bildelemente
Hintergrund-Bildelemente zur Erzeugung eines grauen Hintergrundes in bezug auf ein
Zeichen anderer Intensität sind.
10. Verfahren nach Anspruch 8, dadurch gekennzeichnet, daß besagte erregte Bildelemente
Zeichen-Bildelemente zur Erzeugung eines grauen Zeichens mit in bezug auf einen Hintergrung
anderer Intensität sind.
11. Verfahren nach Anspruch 10, dadurch gekennzeichnet, daß besagter Hintergrund anderer
Intensität für Weiß bezeichnend ist.
12. Verfahren nach Anspruch 10, dadurch gekennzeichnet, daß besagte gespeicherte Digitalstrukturen
mindestens sechs Strukturen sind, die sechs verschiedene Graustufen bezeichnen.
13. Verfahren nach Anspruch 10, dadurch gekennzeichnet, daß der Schritt des ODERns der
besagten gewählten Struktur mit einer Zeichenstruktur vorgesehen ist, bevor besagte
Zeichenstruktur zur Anzeige eines Zeichens gegebener Intensität auf einem Hintergrund
der gewählten Graustufe an besagte Anzeige angelegt wird.
14. Verfahren nach Anspruch 10, dadurch gekennzeichnet, daß der Schritt des UNDens der
besagten gewählten Struktur mit einer Zeichenstruktur vorgesehen ist, bevor besagte
Zeichenstruktur zur Anzeige eines Hintergrundes gegebener Intensität mit einem aufgedruckten
Zeichen der gewählten Graustufe an besagte Anzeige angelegt wird.
1. Appareil pour procurer une capacité de reproduction des gris pour un affichage d'informations
électrophorétique (EPID), dans lequel ledit affichage électrophorétique est un affichage
adressable X-Y, chaque coordonnée X-Y étant indicative d'une intersection colonne
et rangée donnée, chaque coordonnée X-Y définissant un pixel qui lorsqu'il est excité
procure un affichage d'une intensité différente par rapport au pixel non excité, caractérise
en ce que
des moyens sont couplés sur ledit affichage pour appliquer sur ledit affichage
une pluralité de motifs numériques prédéterminés qui sont indépendants des données
ou d'une image écrite sur ledit affichage pour exciter lesdits pixels dans ledit affichage
par rapport aux autres pixels dans ledit affichage selon un motif sélectionné parmi
ces motifs, lesdits pixels excités étant de la même intensité que les pixels d'une
image sur ledit affichage et chacun des motifs numériques prédéterminés étant distincts
et disposés en configurations répétitives qui produisent différents niveaux de l'échelle
des gris, par quoi la zone autour de ladite image est efficacement modulée conformément
audit motif pour varier ladite image par rapport à l'arrière-plan de l'affichage.
2. L'appareil suivant la Revendication 1, caractérisé en ce que ledit pixel, quand il
est excité, affiche une intensité foncée par rapport à une intensité plus claire quand
il n'est pas excité, ladite intensité plus foncée correspondant à un niveau de noir
et ladite intensité plus claire correspondant à un niveau de blanc.
3. L'appareil suivant la Revendication 1, caractérisé en ce que ledit motif numérique
est appliqué sur ledit affichage au moyen de moyens logiques ET pour que les caractères,
tels qu'ils sont écrits sur ledit affichage, présentent ledit niveau de l'échelle
des gris par rapport à l'arrière-plan dudit affichage.
4. L'appareil suivant la Revendication 1, caractérisé en ce que ledit motif numérique
est appliqué sur ledit affichage au moyen de moyens logiques OU pour que ledit arrière-plan
présente ledit niveau de l'échelle des gris par rapport aux caractères sur ledit affichage.
5. L'appareil suivant la Revendication 1, caractérisé en ce que ledit moyen comprend
de plus des moyens logiques qui fonctionnent pour que les caractères écrits dans ledit
affichage et ledit arrière-plan dudit affichage soient excités selon ledit motif numérique
et conformément audit niveau souhaité de l'échelle des gris.
6. L'appareil suivant la Revendication 1, caractérisé en incluant des moyens de mémoire
pour y stocker une pluralité de motifs numériques, chacun étant indicatif de différents
niveaux souhaités de l'échelle des gris, et
des moyens couplés auxdits moyens de mémoire pour sélectionner le motif souhaité
parmi lesdits motifs numériques stockés pour une application sur ledit affichage.
7. L'appareil suivant la Revendication 6, dans lequel ledit affichage électrophorétique
est un affichage de haute résolution.
8. Une méthode pour procurer une capacité de reproduction des gris pour un affichage
d'informations électrophorétique (EPID) du type qui emploie la sélection des pixels,
caractérisées par les étapes :
de stockage d'une pluralité de motifs numériques, chaque motif numérique étant distinct
et disposé en configurations répétitives qui produisent différents niveaux de l'échelle
des gris, lesdits motifs stockés, lors de leur application sur un affichage électrophorétique,
causant l'excitation desdits pixels dans ledit affichage par rapport aux autres pixels
dans ledit affichage conformément au niveau souhaité de l'échelle des gris, et chaque
pixel excité étant de la même intensité que les pixels d'une image sur ledit affichage,
et
de sélection d'un motif stocké pour application sur ledit affichage par un moyen indépendant
des données ou d'une image écrite sur ledit affichage, pour que ledit affichage présente
le niveau d'échelle des gris par quoi la zone de ladite image est efficacement modulée
selon ledit motif pour varier le contraste de ladite image par rapport à l'arrière-plan
de l'affichage.
9. La méthode suivant la Revendication 8, caractérisée en ce que lesdits pixels excités
sont des pixels d'arrière-plan pour procurer un arrière-plan gris par rapport à un
caractère d'une intensité différente.
10. La méthode suivant la Revendication 8, caractérisée en ce que lesdits pixels excités
sont des pixels de caractère pour procurer un caractère gris par rapport à un arrière-plan
d'une intensité différente.
11. La méthode suivant la Revendication 10, caractérisée en ce que ledit arrière-plan
d'une intensité différente est indicatif de blanc.
12. La méthode suivant la Revendication 10, caractérisée en ce que lesdits motifs numériques
stockés sont au moins six motifs indicatifs de six niveaux différents de l'échelle
des gris.
13. La méthode suivant la Revendication 10, caractérisée en ce qu'il y a d'inclus l'étape
d'opération "OU" sur ledit motif sélectionné avec un motif de caractère avant d'appliquer
ledit motif de caractère sur ledit affichage pour afficher un caractère d'une intensité
donnée sur un fond dudit niveau sélectionné de l'échelle des gris.
14. La méthode suivant la Revendication 10, caractérisée en ce qu'il y a d'inclus l'étape
d'opération "ET" sur ledit motif sélectionné avec un motif de caractère avant d'appliquer
ledit motif de caractère sur ledit affichage pour afficher un arrière plan d'une intensité
donnée ayant un caractère appliqué dessus dudit niveau sélectionné de l'échelle des
gris.