U.S. patent application number 11/492163 was filed with the patent office on 2008-01-24 for display element having groups of individually turned-on steps.
Invention is credited to Alan R. Arthur, Peter James Fricke, Tim R. Koch, Joseph W. Stellbrink.
Application Number | 20080018576 11/492163 |
Document ID | / |
Family ID | 38700227 |
Filed Date | 2008-01-24 |
United States Patent
Application |
20080018576 |
Kind Code |
A1 |
Fricke; Peter James ; et
al. |
January 24, 2008 |
Display element having groups of individually turned-on steps
Abstract
A display element corresponds to a pixel of a display. The
display element includes a first electrode connected to a first
addressable line of the display, and a number of second electrodes,
each of which is connected to a corresponding second addressable
line of the display. The display element includes a display
mechanism situated between the first and the second electrodes, and
which has a number of individually turned-on steps organized into a
number of groups corresponding to the number of second electrodes.
For each group of the individually turned-on steps, each step of
the group has a turn-on voltage threshold at which the step is
turned on upon a voltage applied between the first electrode and
the second electrode to which the group corresponds that is equal
to or greater than the turn-on voltage threshold.
Inventors: |
Fricke; Peter James;
(Corvallis, OR) ; Arthur; Alan R.; (Corvallis,
OR) ; Stellbrink; Joseph W.; (Corvallis, OR) ;
Koch; Tim R.; (Corvallis, OR) |
Correspondence
Address: |
HEWLETT PACKARD COMPANY
P O BOX 272400, 3404 E. HARMONY ROAD, INTELLECTUAL PROPERTY ADMINISTRATION
FORT COLLINS
CO
80527-2400
US
|
Family ID: |
38700227 |
Appl. No.: |
11/492163 |
Filed: |
July 23, 2006 |
Current U.S.
Class: |
345/88 |
Current CPC
Class: |
G02F 1/1391 20130101;
G02F 1/134345 20210101; G09G 3/3637 20130101; G02F 1/133371
20130101; G09G 3/364 20130101 |
Class at
Publication: |
345/88 |
International
Class: |
G09G 3/36 20060101
G09G003/36 |
Claims
1. A display element corresponding to a pixel of a display,
comprising: a first electrode connected to a first addressable line
of the display; a plurality of second electrodes, each second
electrode connected to a corresponding second addressable line of
the display; and, a display mechanism situated between the first
and the second electrodes, and having a plurality of individually
turned-on steps organized into a number of groups corresponding to
a number of the second electrodes, wherein, for each group of the
individually turned-on steps, each individually turned-on step of
the group has a turn-on voltage threshold at which the step is
turned on upon a voltage applied between the first electrode and
the second electrode to which the group corresponds equal to or
greater than the turn-on voltage threshold, and wherein each group
of the individually turned-on steps corresponds to a different
color of the pixel, as one of red, green, and blue.
2. The display element of claim 1, wherein the display element is
to realize a desired grayscale value by, for each group of the
individually turned-on steps, applying a voltage between the first
electrode and the second electrode to which the group
corresponds.
3. The display element of claim 1, wherein, for each group of the
individually turned-on steps, each individually turned-on step of
the group has a turn-off voltage threshold at which the step is
turned off upon a voltage applied between the first electrode and
the second electrode to which the group corresponds equal to or
less than the turn-off voltage threshold.
4. The display element of claim 1, wherein the display element has
a left side and a right side, the groups of the individually
turned-on steps and the second electrodes organized contiguously
from the left side to the right side of the display element.
5. The display element of claim 1, wherein the display element has
a left side and a right side, the groups of the individually
turned-on steps and the second electrodes organized
non-contiguously from the left side to the right side of the
display element.
6. The display element of claim 1, wherein the display element has
a front side and a back side, each individually turned-on step
extending from the front side to the back side of the display
element.
7. The display element of claim 1, wherein at least a sub-plurality
of the individually turned-on steps are organized such that the
individually turned-on steps of the sub-plurality have a common
center.
8. The display element of claim 1, wherein at least one of the
groups of the individually turned-on steps is unequal in area as
compared to other of the groups of the individually turned-on
steps, such that at least one of the second electrodes is unequal
in area as compared to other of the second electrodes.
9. The display element of claim 1, wherein at least one of the
second electrodes is non-rectangular in shape.
10. The display element of claim 1, wherein the display mechanism
comprises: a post aligned bi-stable nematic (PABN) liquid crystal
layer; and, a conductive layer.
11. The display element of claim 1, wherein the display element is
a bi-stable display element.
12. A display device comprising: a plurality of first addressable
lines; a plurality of second addressable lines; a plurality of
display elements corresponding to a plurality of pixels of the
display device, each display element connected to one of the first
addressable lines and a sub-plurality of the second addressable
lines, such that no two of the display elements are connected to a
same one of the first addressable lines and a same sub-plurality of
the second addressable lines, wherein each display element has a
plurality of individually turned-on steps organized into a number
of groups corresponding to a number of the sub-plurality of the
second addressable lines to which the display element is connected,
wherein for each group of the individually turned-on steps of each
display element, each individually turned-on step of the group has
a turn-on voltage threshold at which the step is turned on upon a
voltage applied between the first addressable line and the second
addressable line to which the group corresponds equal to or greater
than the turn-on voltage threshold, and wherein each group of the
individually turned-on steps corresponds to a different color of
the pixel, as one of red, green, and blue.
13. The display device of claim 12, wherein each display element is
to realize a desired grayscale value for each group of the
individually turned-on steps of the display element, by applying a
voltage between the first addressable line and the second
addressable line to which the group corresponds.
14. The display device of claim 12, wherein, for each group of the
individually turned-on steps of each display element, each
individually turned-on step of the group has a turn-off voltage
threshold at which the step is turned off upon a voltage applied
between the first addressable line and the second addressable line
to which the group corresponds equal to or less than the turn-off
voltage.
15. The display device of claim 12, wherein the display elements
are organized in rows and columns, such that over the columns of
the display elements, the groups of the individually turned-on
steps of the display elements alternate such that corresponding
groups among the display elements are not inline with one
another.
16. A method comprising: for each display element of a plurality of
display elements of a display device corresponding to a plurality
of pixels of the display element, connecting the display element to
a first addressable line of the display device and a plurality of
second addressable lines of the display device, such that no two of
the display elements are connected to a same first addressable line
and a same plurality of second addressable lines; and, providing a
plurality of individually turned-on steps of the display element
organized into a number of groups corresponding to a number of the
plurality of second addressable lines to which the display element
is connected, such that for each group of the individually
turned-on steps of the display element, each individually turned-on
step of the group has a turn-on voltage threshold at which the step
is turned on upon a voltage applied between the first addressable
line and the second addressable line to which the group corresponds
equal to or greater than the turn-on voltage threshold, wherein
each group of the individually turned-on steps corresponds to a
different color of the pixel, as one of red, green, and blue.
17. The method of claim 16, wherein each display element is to
realize a desired grayscale value by, for each group of the
individually turned-on steps of the display element, applying a
voltage between the first addressable line and the second
addressable line to which the group corresponds.
18. The method of claim 16, wherein, for each group of the
individually turned-on steps of each display element, each
individually turned-on step of the group has a turn-off voltage
threshold at which the step is turned off upon a voltage applied
between the first addressable line and the second addressable line
to which the group corresponds equal to or less than the turn-off
voltage.
Description
BACKGROUND
[0001] The most common type of display device requires the
individual display elements of the display device to be refreshed a
number of times per second to maintain the picture being displayed.
If power is removed from the display device, then no picture can be
displayed on the display device. Another type of display device is
one that only requires that power be provided to the display device
when the picture displayed on the device is modified or changed.
Otherwise, a static image remains displayed on the display device
substantially indefinitely even in the absence of power to the
display device, although power may still be needed for backlighting
purposes.
[0002] The latter type of display device includes those implemented
using bi-stable display elements. Bi-stable display elements have
an on state, in which the display element is on and displaying
image data, and an off state, in which the display element is off
and not displaying image data. Because such bi-stable display
elements have just two states, a number of independently
addressable elements may be needed to implement a single pixel of a
display device. For instance, to implement a single color of a
pixel having three bits, or eight levels, of color depth, three
such bi-stable display elements may be needed, since 2.sup.3 bits
equals eight levels.
[0003] To realize a display device using such bi-stable display
elements in which each pixel includes three colors, red, green, and
blue, and each sub-pixel has eight, sixteen, or more tonal levels,
a large number of bi-stable display elements may be needed. This in
turn means that a large number of addressable lines have to be
connected to the display elements, since each display element is
independently addressable. The resulting display device, however,
may be difficult to cost effectively manufacture, owing to the
large number of bi-stable display elements and the large number of
addressable lines connected to these elements.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIGS. 1A and 1B are diagrams of a front view and a
cross-sectional top view, respectively, of a display element having
a number of independently turned-on steps, according to an
embodiment of the invention.
[0005] FIGS. 2, 3, 4, and 5 are diagrams of a cross-sectional top
view of a display element, according to different embodiments of
the invention.
[0006] FIG. 6 is a diagram of a cross-sectional top view of a
number of display elements, according to an embodiment of the
invention.
[0007] FIG. 7 is a diagram of a display device, according to an
embodiment of the invention.
[0008] FIG. 8 is a diagram of a column of display elements of a
display device, according to an embodiment of the invention.
[0009] FIG. 9 is a flowchart of a method, according to an
embodiment of the invention.
DETAILED DESCRIPTION OF THE DRAWINGS
[0010] FIGS. 1A and 1B show a front view and a cross-sectional top
view, respectively, of a display element 100 corresponding to a
pixel of a display, according to an embodiment of the invention.
The display element 100 includes a top electrode 102 and two bottom
electrodes 104A and 104B, collectively referred to as the bottom
electrodes 104. The top electrode 102 is connected to a first
addressable line 114 of the display, and the bottom electrodes 104
are correspondingly connected to second addressable lines 116A and
116B of the display, collectively referred to as the second
addressable lines 116.
[0011] Between the electrodes 102 and 104 is a display mechanism
106. In the embodiment of FIGS. 1A and 1B, the display mechanism
106 includes a conductive layer 108 and a liquid crystal layer 110.
The conductive layer 108 may be polyethylenedioxythiophene (PEDOT),
or another type of conductive layer. The conductive layer 108 is
patterned such that the conductive layer 108A is connected to the
electrode 104A and the conductive layer 108B is connected to the
electrode 104B. The liquid crystal layer 110 may be a post aligned
bi-stable nematic (PABN) liquid crystal layer, or another type of
liquid crystal layer. The display element 100 is bi-stable, in that
once it has been turned on by applying a first voltage between the
electrodes 102 and 104A and/or a second voltage between the
electrodes 102 and 104B, the element 100 remains in its current
state, until it is turned off. That is, voltages do not have to be
continually applied between the electrodes 102 and 104A and the
electrodes 102 and 104B for the element 100 to remain in its
current state, once the element 100 has been switched to that
state. Stated another way and most generally, the display element
100 remains in its current state until one or more voltages are
applied to change the state of the display element 100.
[0012] The display mechanism 106 has a number of individually
turned-on steps 112A, 112B, and 112C, collectively referred to as
the individually turned-on steps 112, and a number of individually
turned-on steps 113A, 113B, and 113C, collectively referred to as
the individually turned-on steps 113. The steps 112 and 113 are
organized into two groups of steps: a first group corresponding to
the steps 112, and a second group corresponding to the steps 113.
While there are three such steps 112 and three such steps 113 in
the example of FIGS. 1A and 1B, in other embodiments there may be
more or less of the steps 112 and of the steps 113. Furthermore,
while there are two groups of steps in the example of FIGS. 1A and
1B, in other embodiments there may be more than two groups.
[0013] The group of steps 112 corresponds to the bottom electrode
104A, and to a first sub-display element 118A to the left of the
dotted line 120. The group of steps 113 corresponds to the bottom
electrode 104B, and to a second sub-display element 118B to the
right of the dotted line 120. The number of groups of steps
corresponds to the number of the bottom electrodes 104. The top
electrode 102 is shared by all the groups of steps. While there are
two sub-display elements 118A and 118B depicted in the example of
FIGS. 1A and 1B, in other embodiments there may be more than two
sub-display elements.
[0014] The steps 112 and 113 can further correspond to different
pillars or other types of structures within the display mechanism
106. That is, the terminology step as used herein is used in a
broad, encompassing sense. As such, this terminology encompasses
different types of structures that can be implemented within the
display mechanism 106, such as pillars.
[0015] The steps 112 and 113 are individually turned on in that
each of the steps 112 and 113 may be turned on, and display image
data, while the other of the steps 112 and 113 remain off. In one
embodiment, when a given step is turned on, it displays image data,
and when a given step is turned off, it does not display image
data. (Alternatively, when a given step is turned on, it does not
display image data, and when it is turned off, it does display
image data.) As depicted in FIG. 1B in particular, each of the
steps 112 and 113 corresponds to a different area of the display
mechanism 106.
[0016] The individually turned-on steps 112 and 113 are defined by
varying the heights of the layers 108 and 110, from top to bottom
in FIG. 1A, along the width of the display element 100, from left
to right in both FIGS. 1A and 1B. The steps 112 and 113 may have
the same or different widths from left to right in FIGS. 1A and 1B.
The smaller the gap between a given step of the conductive steps
112 and 113 and the opposing electrode 102, the lower the required
voltage to turn on that step.
[0017] Thus, the steps 112A, 112B, and 112C have positive turn-on
voltage thresholds PV1A, PV1B, and PV1C, respectively, where
PV1A>PV1B>PV1C. Therefore, a given applied positive voltage
PV1 between the electrodes 102 and 104A turns on all the steps 112
having positive turn-on voltage thresholds equal to or less than
the positive voltage PV1. Likewise, the steps 113A, 113B, and 113C
have positive turn-on voltage thresholds PV2A, PV2B, and PV2C,
respectively, where PV2A>PV2B>PV2C. A given applied positive
voltage PV2 between the electrodes 102 and 104B turns on all the
steps 113 having positive turn-on voltage thresholds equal to or
less than the positive voltage PV2.
[0018] Furthermore, the larger the gap between a given step of the
conductive steps 112 and 113 and the opposing electrode 102 in FIG.
1A, the greater the magnitude of the negative voltage that is
needed to be applied to turn off that step. Thus, the steps 112A,
112B, and 112C have negative turn-off voltage thresholds NV1A,
NV1B, and NV1C, respectively, where |NV1A|>|NV1B|>|NV1C|,
where |x| is the absolute value of x. If the (negative) signage of
the voltage thresholds are taken into account, then
NV1A<NV1B<NV1C. Therefore, a given applied negative voltage
NV1 between the electrodes 102 and 104A turns off all the steps
having negative turn-off voltage thresholds having absolute
magnitudes equal to or less than the absolute magnitude of the
negative voltage NV1.
[0019] Likewise, the steps 113A, 113B, and 113C have negative
turn-off voltage thresholds NV2A, NV2B, and NV2C, respectively,
where |NV2A|>|NV2B|>|NV2C|, where |x| is the absolute value
of x. If the (negative) signage of the voltage thresholds are taken
into account, then NV2A<NV2B<NV2C. A given applied negative
voltage NV2 between the electrodes 102 and 104B turns off all the
steps having negative turn-off voltage thresholds having absolute
magnitudes equal to or less than the absolute magnitude of the
negative voltage NV2.
[0020] In general, the steps 112 and 113 are turned on in a desired
combination. For each sub-display element, a positive voltage is
applied that is equal to or greater than the step of this
sub-display element having the highest positive turn-on voltage
threshold that is to be turned on. This positive voltage turns on
all the steps of this sub-display element having positive turn-on
voltage thresholds less than the positive voltage applied. Next, a
negative voltage is applied that is equal to or less than the step
of the sub-display element having the lowest, most negative
turn-off voltage threshold that has been turned on but should be
turned off. That is, a negative-voltage is applied that has an
absolute magnitude that is greater than or equal to the step of the
sub-display element having a turn-off voltage threshold that has
the highest absolute magnitude and that has been turned on but
should be turned off. This negative voltage turns off all the steps
of the sub-display element having negative turn-off voltage
thresholds having absolute magnitudes less than the absolute
magnitude of the negative voltage applied.
[0021] This process is then repeated for the step having the
next-highest positive turn-on voltage threshold that is to be
turned on, the next-lowest negative turn-off voltage threshold
(i.e., the negative turn-off voltage having the next-highest
absolute magnitude) that is to be turned off, and so on, until the
steps of the sub-display element have been turned on in the desired
combination. The process is then repeated for each other
sub-display element, so that the desired step or steps of each
other sub-display element are turned on. Therefore, in the example
of FIGS. 1A and 1B, the process can be first performed for the
sub-display element 118A, and then performed for the sub-display
element 118B, or vice-versa.
[0022] For example, consider the situation where the steps 112A and
112C of the sub-display element 118A are to be turned on, and the
step 112B of the sub-display element 118A and all the steps 113 of
the sub-display element 118B are to remain off. A positive voltage
is applied between the electrodes 102 and 104A that is equal to or
greater than PV1A, the positive turn-on voltage threshold for the
step 112A. This turns on all the steps 112. Next, a negative
voltage is applied between the electrodes 102 and 104A that is
equal to or less than NV1B, the negative turn-off voltage threshold
for the step 112B, but greater than NV1A, the negative turn-off
voltage threshold for-the step 112A. (That is, the negative voltage
has an absolute magnitude that is equal to or greater than the
absolute magnitude of NV1B, but that is less than the absolute
magnitude of NV1A.) This turns off the steps 112B and 112C, while
the step 112A remains on.
[0023] However, the step 112C is also to be turned on. Therefore,
another positive voltage between the electrodes 102 and 104A is
applied, which is equal to or greater than PV1C, the positive
turn-on voltage threshold for the step 112C, but is less than PV1B,
the positive turn-on voltage threshold for the step 112B. This
turns on the step 112C. Because none of the steps 113 of the
sub-display element 118B have to be turned on, no voltages need to
be applied between the electrodes 102 and 104B.
[0024] There are advantages of having a display element 100 having
individually turned-on steps 112 and 113 organized into groups of
steps corresponding to the number of electrodes 104 and thus
defining multiple sub-display elements 118. As compared to having a
display element having individually turned-on steps in which there
is just one electrode 104 and thus not defining multiple
sub-display elements, embodiments of the invention provide for
improved manufacturability, yield, and design margin. These
advantages are now described in detail.
[0025] For example, consider the case where the display element 100
has six steps 112 and 113, as in the embodiment of FIGS. 1A and 1B.
In the embodiment of FIGS. 1A and 1B, where these steps are divided
over two sub-display elements, a greater margin is allowed in the
turn-on and turn-off voltage threshold differences among the steps
112, and in the voltage threshold differences among the steps 113.
The voltage thresholds of the steps 112 are independent of the
voltage threshold of the steps 113, and indeed, the voltage
thresholds for the steps 112 can correspondingly equate to those
for the steps 113. Thus, there is greater separation among the
voltage thresholds for the steps 112 and among the voltage
thresholds for the steps 113, since for a given range of allowable
voltage thresholds, just three different voltage thresholds have to
be selected in the example of FIGS. 1A and 1B for each group of
steps 112 and 113.
[0026] If a display element were to have six steps that were not
divided over two sub-display elements, a lesser margin would be
afforded in the turn-on and turn-off voltage threshold differences
among the steps. For the same given range of allowable voltage
thresholds, six different voltage thresholds would have to be
selected for the six steps. Therefore, higher precision would be
needed in manufacturing the display element, which can result in
reduced yield and lesser design margin. By comparison, dividing the
six steps into two groups of three steps each means that less
precision would be needed in manufacturing the display element,
which can result in increased yield due to greater design margin.
Other design advantages include enabling large display sizes or
integration of addressing electronics.
[0027] For example, the range of allowable voltage thresholds may
be from V1 to V2, where V2 minus V1 is equal to Vrange. As such, if
a display element were to have six steps that were not divided over
two or more sub-display elements, and assuming the simple case
where the voltage thresholds for the steps are equidistant from one
another, then the voltage threshold of each step would be separated
by a voltage of Vrange divided by five from the voltage thresholds
of the adjacent steps. By comparison, the display element 100 of
FIGS. 1A and 1B, where the six steps are divided over two
sub-display elements, then the voltage threshold of each step of
each group is separated by a voltage of Vrange divided by two from
the voltage thresholds of the adjacent steps in that group.
[0028] Therefore, in this example, dividing the six steps of a
display element into two groups and two sub-display elements
increases the spacing between voltage thresholds of adjacent steps
by
Vrange 2 - Vrange 5 Vrange 5 . ##EQU00001##
The spacing between voltage thresholds of adjacent steps is thus
increased by 150%. Increasing the spacing between voltage
thresholds of adjacent steps means that less precision is needed in
manufacturing the steps of the display element as well as the
associated drive electronics used to address the display element,
thus resulting in increased yield.
[0029] The manner by which the individually turned-on steps of the
groups of the display element are realized is not limited by
embodiments of the invention. For instance, FIGS. 1A and 1B show an
example in which the display element 100 has a left side and a
right side. The groups of the steps 112 and 113, as well as the
bottom electrodes 104, are organized contiguously from the left
side to the right side of the display element 100. Thus, all of the
steps 112 of one group, and the electrode 104A, are to the left of
the dotted line 120, whereas all of the steps 113 of another group,
and the electrode 104B, are to the right of the dotted line
120.
[0030] FIG. 2 shows a top view of the display element 100 in which
the groups of steps 112 and 113 and the electrodes 104 are
non-contiguously organized from the left side to the right side of
the display element 100, according to a different embodiment of the
invention. In particular, the steps 112C and 113C are divided, as
are the electrodes 104A and 104B. Thus, from left to right, the
complete steps 112A and 112B of the group of steps 112 are
situated, followed by a first part of the step 112C of this same
group of steps. Thereafter, the complete steps 113A and 113B of the
group of steps 113 are situated, followed by the second part of the
step 112C of the group of steps 112. Finally, the second part of
the step 113C of the group of steps 113 is situated.
[0031] Even though the electrodes 104 are divided, the parts of the
electrode 104A are electrically connected to one another, which is
diagrammatically illustrated in FIG. 2 as a wire 202A for
illustrative convenience, and the parts of the electrode 104B are
electrically connected to one another, which is diagrammatically
illustrated in FIG. 2 as a wire 202B for illustrative convenience.
Organizing the groups of steps 112 and 113 non-contiguously from
the left side to the right side of the display element 100 can be
advantageous. In particular, it ensures that there are not large
lit or non-lit regions of the display element 100, reducing the
likelihood of generating observable patterns in the displayed
image. For instance, where just the step 112C is lit, having the
step 112C divided into two non-contiguous parts ensures that no
large non-lit region of the display element 100 exists.
[0032] The groups of steps 112 and 113 can be arranged
non-contiguous from the left side to the right side of the display
element 100 in other ways than is shown in FIG. 2. In FIG. 2,
non-contiguous arrangement or organization is achieved by splitting
one step of each group, namely the steps 112C and 113C, in
non-contiguous fashion. Alternatively, however, as one example,
none of the steps 112 and 113 may be divided or split. For
instance, the steps 112 and 113 may be organized from left to right
as follows: complete steps 112A, 112B, 113A, 112C, 113B, and 113C.
In this example, steps 112A and 112B are non-contiguous with the
step 112C of the same group of steps 112, and steps 113B and 113C
are non-contiguous with the step 113A of the same group of steps
113.
[0033] The examples of FIGS. 1A, 1B, and 2 have the groups of the
steps 112 and 113 organized such that each step extends completely
from the top side to the bottom side of the display element 100.
For example, in FIG. 2, all of the steps 112 and 113 extend
completely from the top to the bottom of the display element 100,
even though the steps 112C and 113C are divided from the left side
to the right side of the display element 100. However, other
embodiments of the invention are not so limited.
[0034] FIG. 3 shows a top view of the display element 100 in which
none of the steps 112 and 113 extend completely from the top side
to the bottom side of the display element 100, according to a
different embodiment of the invention. Of the group of steps 112,
the step 112A is located within the interior of the sub-display
element 118A to the left of the dotted line 120. The step 112B is
divided into two parts, each of which has a top side flush with the
top side of the step 112A and a bottom side flush with the bottom
side of the step 112A. The step 112C is also divided into two
parts, each of which extend from the left side of the sub-display
element 118A to the right side of the sub-display element 118A.
[0035] Of the group of steps 113, the step 113A is located within
the interior of the sub-display element 118B to the right of the
dotted line 120. The step 113B surrounds the step 113A, and indeed
shares a common center with the step 113A. The step 113C is divided
into two parts, of which extend from the left side of the
sub-display element 118B to the right side of the sub-display
element 118B. Neither of the electrodes 104 is divided in the
example of FIG. 3.
[0036] It is noted that the steps 112A, 112B, and 112C can each
further be sub-divided into many non-contiguous areas distributed
throughout the entire area occupied by the steps 112A, 112B, and
112C, to further distribute lit and non-lit areas. In addition, the
ratio of the area of each of the steps 112A, 112B, and 112C to the
total area occupied by all the steps 112A, 112B, and 112C may be
unequal to optimally match the lightness response of the human
visual system.
[0037] The examples of FIGS. 1A, 1B, 2, and 3 substantially have
the groups of the steps 112 and 113 having equally sized areas,
such that the electrodes 104 substantially have equally sized
areas. For example, in FIG. 3, the area occupied by the group of
steps 112 is substantially equal to the area occupied by the group
of steps 113. As such, the area occupied by the electrode 104A is
substantially equally to the area occupied by the electrode 104B.
However, other embodiments are not so limited.
[0038] FIG. 4 shows a top view of the display element 100 in which
the groups of steps 112 and 113 have unequal areas and the
electrodes 104 have unequal areas, according to a different
embodiment of the invention. As depicted in FIG. 4, the group of
steps 112, of which the individual steps 112A, 112B, and 112C are
not particularly shown, has a larger area than the group of steps
113, of which the individual steps 113A, 113B, and 113C are not
particularly shown, does. Likewise, the electrode 104A has a larger
area than the electrode 104B does.
[0039] The examples of FIGS. 1A, 1B, 2, 3, and 4 substantially have
the groups of the steps 112 and 113 having a rectangular shape from
the top view, such that the electrodes 104 likewise have a
rectangular shape from the top view. For example, in FIG. 4, the
shape of the group of steps 112 is rectangular, and the
corresponding electrode 104A is rectangular. Likewise, the shape of
the group of steps 113 is rectangular, and the corresponding
electrode 104B is rectangular. However, other embodiments are not
so limited.
[0040] FIG. 5 shows a top view of the display element 100 in which
the groups of steps 112 and 113 have non-rectangular shapes and the
electrodes 104 likewise have non-rectangular shapes, according to a
different embodiment of the invention. As depicted in FIG. 5, the
groups of steps 112 and 113 both have non-rectangular shapes. The
electrodes 104 likewise correspondingly have non-rectangular shapes
that effectively mirror the shapes of their corresponding groups of
steps 112 and 113.
[0041] In one embodiment, each of the individually turned-on steps
of all the groups of steps of a display element corresponds to a
single color of a pixel of a display. For instance, the steps of
all the groups of the display element may correspond to the color
red of the pixel, the color green of the pixel, or the color blue
of the pixel. As such, the steps provide for multiple tone levels
of the display element for this color of the pixel. For example,
where there are N steps, the steps provide for 2.sup.N tonal levels
for the color of the pixel to which the display element
corresponds. That is, the display element can realize a desired
grayscale value in question by, for each group of the individually
turned-on steps, applying an appropriate voltage between the top
electrode and the bottom electrode to which the group of steps
corresponds.
[0042] In another embodiment, the individually turned-on steps of a
display element may be divided into groups, where each group is
connected to its own bottom electrode and corresponds to a
different color of a pixel of a display to which the display
element itself corresponds. For instance, the steps of the display
element may be grouped into three groups: a red group corresponding
to the color red of the pixel and connected to a first bottom
electrode, a green group corresponding to the color green of the
pixel and connected to a second bottom electrode, and a blue group
corresponding to the color blue of the pixel and connected to a
third bottom electrode. In this way, the steps provide for multiple
levels of contrast depth of the display element for each of the
three colors of the pixel. For example, where there are R steps in
the red group, G steps in the green group, and B steps in the blue
group, the steps provide for 2.sup.R levels of contrast depth for
red, 2.sup.G levels of contrast depth for green, and 2.sup.B levels
of contrast depth for blue of the pixel to which the display
element corresponds.
[0043] FIG. 6 shows a top view of two display elements 602A and
602B, according to an embodiment of the invention. The display
elements 602A and 602B are collectively referred to as the display
elements 602. The display element 602A is connected to the first
addressable line 612A, whereas the display element 602B is
connected to the first addressable line 612B. Both of the display
elements 602 are connected to both second addressable lines 614A
and 614B.
[0044] The display element 602A has a red group of steps 604 and a
blue group of steps 606, where the former group 604 is connected to
the second addressable line 614A and the latter group of steps 606
is connected to the second addressable line 614B. Both groups of
steps 604 and 606 of the display element 602A are connected to the
first addressable line 612A. The electrodes of the display element
602A are not shown. The red group of steps 604 corresponds to a
first sub-display element of the display element 602A, and the blue
group of steps 606 corresponds to a second sub-display element of
the display element 602A. Therefore, by appropriately applying a
voltage between the lines 612A and 614A, and by appropriately
applying a voltage between the lines 612A and 614B, different
grayscale values of each of red and blue can be displayed by the
display element 602A, by turning on a different number of the red
steps 604 and a different number of the blue steps 606.
[0045] The display element 602B has two green groups of steps 608
and 610. The group of steps 608 is connected to the second
addressable line 614A and the group of steps 610 is connected to
the second addressable line 614B, where both groups of steps 608
and 610 are connected to the first addressable line 612B. The
electrodes of the display element 602B are not shown. The group of
steps 608 corresponds to a first sub-display element of the display
element 602B, whereas the group of steps 610 corresponds to a
second sub-display element of the display element 602B. By
appropriately applying a voltage between the lines 612B and 614A,
and by appropriately applying a voltage between the lines 612B and
614B, different grayscale values of green can be displayed by the
display element 602B, by turning on different of the steps 604 and
606.
[0046] For example, where each of the groups of steps 604, 606,
608, and 610 has three steps, there can be at most 2.sup.3, or
eight, shades of red, 2.sup.3, or eight, shades of blue, and
2.sup.6, or 64 shades of green. A display element is thus defined
in the example of FIG. 6 as having a number of different groups of
steps, where each group is connected to a different second
addressable line as compared to the other groups of steps of this
display element. A display element is also defined in the example
of FIG. 6 as connected to one and only one first addressable line,
which is connected to all the groups of steps of the display
element. Each of the display elements 602 of FIG. 6 may correspond
to the same pixel of a display, where the display element 602A is
responsible for displaying the red and blue color components of the
pixel, and the display element 602B is responsible for displaying
the green color component of the pixel. An advantage of this
approach is a reduction in the number of addressing lines
needed.
[0047] FIG. 7 shows a representative display device 700, according
to an embodiment of the invention. The display device 700 includes
a number of display elements 702A, 702B, . . . , 702N, collectively
referred to as the display elements 702, and which correspond to
the pixels of the display device 700. Each display element may
correspond to a different pixel, or groups of two or more display
elements may correspond to the same pixel, as in the example of
FIG. 6 that has been described. The display elements 702 are
organized in rows 704A, 704B, . . . , 704J, collectively referred
to as the rows 704, and columns 706A, 706B, . . . , 706K,
collectively referred to as the columns 706.
[0048] Each of the display elements 702 can be implemented as the
display element 100 as has been described. The display elements 702
can be bi-stable display elements, such that they retain their
current states being displayed even if power is removed from the
elements 702. Thus, power is needed only to change the states of
the display elements 702, and not to retain the states of the
display element 702.
[0049] The display device 700 also includes first addressable lines
708A, 708B, . . . , 708J, collectively referred to as the
addressable lines 708 and corresponding to the rows 704 into which
the display elements 702 are organized. The display device 700
further includes second addressable line groups 710A, 710B, . . . ,
710K, collectively referred to as the second addressable line
groups 710 and corresponding to the columns 706 into which the
display elements 702 are organized. Each second addressable line
group includes at least two second addressable lines. Thus, each
display element of the display device 700 is connected to a first
addressable line, and at least two second addressable lines. The
display device 700 can and typically will include other components,
in addition to the display elements 702, the addressable lines 708
and the addressable line groups 710, as can be appreciated by those
of ordinary skill within the art.
[0050] The first addressable lines 708 are connected to all of the
display elements 702 within their respective rows 704. Thus, the
first addressable line 708A is connected to all of the display
elements 702 within the row 704A, the first addressable line 708B
is connected to all of the display elements 702 within the row
704B, and so on. Similarly, the second addressable line groups 710
are connected to all of the display elements within their
respective columns 706. Thus, the second addressable lines of the
second addressable line group 710A are connected to all of the
display elements 702 within the column 706A, the second addressable
lines of the second addressable line group 710B are connected to
all of the display elements 702 within the column 706B, and so
on.
[0051] In this way, each of the display elements 702 is addressable
by a unique pair of a first addressable line and a second
addressable line group, including one of the addressable lines 708
and all the second addressable lines of one of the second
addressable line groups 710. That is, no two display elements are
connected to both the same one of the addressable lines 708 and the
same one of the addressable line groups 710. To change the state of
a given display element, positive and/or negative voltages are
applied between the first addressable line and at least one of the
second addressable lines to which the display element in question
is connected. This process is performed for each of the display
elements 702, to change the states of all of the display elements
702.
[0052] In one embodiment, all the display elements 702 are
instances of the same display element. For instance, all of the
display elements 702 may be instances of the same display element
100, as in FIG. 4, where the left side of each display element is
occupied by a first group of steps 112 that is larger in area than
the right side of the display element as occupied by a second group
of steps 113. However, other embodiments of the invention are not
so limited.
[0053] FIG. 8 shows the column 706A of the display device 700 of
FIG. 7 in more detail, according to a particular embodiment of the
invention. Those of the display elements 702 of the display device
700 of FIG. 7 residing within the column 706A are referenced as
display elements 802A, 802B, 802C, . . . , 802J, for descriptive
convenience, and collectively referred to as the display elements
802. The display elements 802 reside in different instances of the
rows 704 as shown. The display elements 802 correspondingly have
first groups of steps 804A, 804B, 804C, . . . , 804J, collectively
referred to as the first groups of steps 804, and second groups of
steps 806A, 806B, 806C, . . . , 806J, collectively referred to as
the second groups of steps 806. The first groups of steps 804 are
larger in area than the second groups of steps 806.
[0054] In the embodiment of FIG. 8, not all the display elements
802 are instances of the exact same display element. Rather, the
display elements 802 within the column 706A alternate by row as to
being instances of two different display elements. The display
elements 802 within odd-numbered rows, such as the display elements
802A and 802C, have their corresponding first groups of steps 804,
such as the first groups of steps 804A and 804C, to the left side,
and their corresponding second groups of steps 806, such as the
second groups of steps 806A and 806C, to the right side. By
comparison, the display elements 802 within even-numbered rows,
such as the display element 802B, have their corresponding first
groups of steps 804, such as the first group of steps 804B, to the
right side, and their corresponding second groups of steps 806,
such as the second group of steps 806B, to the right side.
[0055] Thus, within the example of FIG. 8, there are two types of
display elements, where even-row display elements are of one type,
and odd-row display elements are of another type. As such,
corresponding groups of steps among the display elements 802 are
not inline with one another. That is, all of the groups of steps
804 are not inline with one another, but rather alternate in
position. Likewise, all of the groups of steps 806 are not inline
with one another, but also rather alternate in position. This
implementation can be advantageous, in that it ensures if a large
number of display elements are all displaying the same color and/or
grayscale value, imaging artifact patterns resulting from each
display element being an instance of the same display element type
may not be perceptible to the human eye.
[0056] FIG. 9 shows a rudimentary method 900, according to an
embodiment of the invention. As indicated by part 902 of the method
900, the method 900 is performed for each display element of a
display device that corresponds to a pixel of the display device.
First, the display element in question is connected to a unique
pair of a first addressable line and more than one second
addressable line of the display device (904), such as has been
described in relation to FIG. 7. Second, the display element is
provided with a number of individually turned-on steps as desired
(906), as has been described above. That is, the steps are
organized into a number of groups corresponding to the number of
second addressable lines to which the display element is
connected.
[0057] Embodiments of the invention thus provide for advantages
over other approaches to achieve multiple-bit contrast depth
display elements (i.e., display elements with multiple levels of
contrast), particularly to achieve multiple-bit contrast depth
bi-stable display elements. Within the prior art, a given bi-stable
display element has just two states, on and off. As a result, to
achieve multiple-bit contrast depth, a number of such display
elements may need to be used to correspond to a given pixel or a
given pixel color. However, where these display elements each is
addressable by a unique pair of addressable lines of the display
device, the resulting number of addressable lines needed can be
quite large, resulting in a cost-prohibitive display device
design.
[0058] By comparison, embodiments of the invention provide for a
bi-stable display element that has more than two states.
Multiple-bit contrast depth can then be achieved by using a single
display element. All of the states of such a display element are
controlled by the same unique pair of a first addressable line and
more than one second addressable line of the display device
connected to this display element. As a result, as compared to the
prior art, less addressable lines are needed to achieve the same
multiple-bit contrast depth, which renders the resulting display
device design more cost effective.
* * * * *