U.S. patent application number 09/730197 was filed with the patent office on 2001-06-21 for light shutter device.
This patent application is currently assigned to MINOLTA CO., LTD.. Invention is credited to Doi, Isao, Kamoda, Yuji, Masuda, Tomohiko, Matsubara, Ken, Saito, Itaru, Yagi, Tsukasa.
Application Number | 20010004295 09/730197 |
Document ID | / |
Family ID | 26578756 |
Filed Date | 2001-06-21 |
United States Patent
Application |
20010004295 |
Kind Code |
A1 |
Doi, Isao ; et al. |
June 21, 2001 |
Light shutter device
Abstract
A light shutter device which has a plurality of light
transmitting portions (light shutter elements) on a planar PLZT
substrate. By applying voltages between a common electrode and
individual electrodes to apply electric fields to the light shutter
elements, the light shutter elements transmit and shut light
individually. Suppose each of the individual electrodes faces the
common electrode at a distance L and has a dimension W in a
direction perpendicular to the direction of electric field,
W/L>2. Suppose each of the individual electrodes has a dimension
D in the direction of electric field, preferably D/L> 0.5.
Further, the individual electrodes are so placed that the distance
between a side of one light shutter element which extends in a
direction perpendicular to the direction of electric field and each
of the individual electrodes which drive the other light shutter
elements is not less than 5L.
Inventors: |
Doi, Isao; (Toyonaka-Shi,
JP) ; Saito, Itaru; (Nishinomiya-Shi, JP) ;
Masuda, Tomohiko; (Otsu-Shi, JP) ; Yagi, Tsukasa;
(Kobe-Shi, JP) ; Matsubara, Ken; (Takatsuki-Shi,
JP) ; Kamoda, Yuji; (Ibaraki-Shi, JP) |
Correspondence
Address: |
SIDLEY & AUSTIN
717 NORTH HARWOOD
SUITE 3400
DALLAS
TX
75201
US
|
Assignee: |
MINOLTA CO., LTD.
|
Family ID: |
26578756 |
Appl. No.: |
09/730197 |
Filed: |
December 5, 2000 |
Current U.S.
Class: |
359/254 ;
359/245 |
Current CPC
Class: |
G02F 1/0316 20130101;
G02F 1/0551 20130101 |
Class at
Publication: |
359/254 ;
359/245 |
International
Class: |
G02F 001/03; G02F
001/07 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 8, 1999 |
JP |
11-348489 |
Jun 13, 2000 |
JP |
2000-176673 |
Claims
What is claimed is:
1. A light shutter device comprising: a planar substrate with an
electro-optical effect; and a plurality of pairs of electrodes
provided on the substrate, portions of the substrate between the
respective pairs of electrodes functioning as light shutter
elements when electric fields act between the respective pairs of
electrodes; wherein, suppose the electrodes in each pair are at a
distance L from each other and a side of one of the electrodes in
each pair which extends in a direction perpendicular to the
direction of electric field has a dimension W, W/L> 2.
2. The light shutter device according to claim 1, wherein the
dimension W is of the electrode in each pair which is shorter in
the direction perpendicular to the direction of electric field.
3. The light shutter device according to claim 1, wherein suppose a
side of one of the electrodes in each pair which extends in the
direction of electric field has a dimension D, D/L> 0.5.
4. The light shutter device according to claim 3, wherein the
dimension D is of the electrode in each pair which is shorter in
the direction of electric field.
5. The light shutter device according to claim 1, wherein the
plurality of pairs of electrodes are composed of a common electrode
which extends in a specified direction and a plurality of
individual electrodes which are arranged along at least one side of
the common electrode so that each of the individual electrodes
faces the common electrode.
6. The light shutter device according to claim 5, wherein the
common electrode has extensions which extend from a central portion
in a direction perpendicular to the specified direction.
7. The light shutter device according to claim 6, wherein the
individual electrodes face the central portion of the common
electrode and the extensions of the common electrode alternately
with respect to the specified direction.
8. The light shutter device according to claim 1, wherein the
substrate with an electro-optical effect is made of PLZT.
9. A light shutter device comprising: a planar substrate with an
electro-optical effect; a common electrode which extends in a
specified direction on the substrate; and a plurality of individual
electrodes which are arranged along the common electrode so that
each of the individual electrodes faces the common electrode,
portions of the substrate between the common electrode and the
respective individual electrodes functioning as light shutter
elements when electric fields act between the common electrode and
the respective individual electrodes; wherein suppose each of the
individual electrodes faces the common electrode at a distance L,
each of the light shutter elements is at a distance not less than
5L from each of the individual electrodes which drive the other
light shutter elements.
10. The light shutter device according to claim 9, wherein the
distance between each of the light shutter elements and each of the
individual electrodes which drive the other light shutter elements
means the distance between a side of the light shutter element
which extends in a direction perpendicular to the direction of
electric field acting on the light shutter element and each of the
individual electrodes which drive the other light shutter
elements.
11. The light shutter device according to claim 9, wherein the
substrate with an electro-optical effect is made of PLZT.
12. A light shutter device comprising: a planar substrate with an
electro-optical effect; a common electrode which extends in a
specified direction on the substrate; and a plurality of individual
electrodes which are arranged along both sides of the common
electrode so that each of the individual electrodes faces the
common electrode, portions of the substrate between the common
electrode and the respective individual electrodes functioning as
light shutter elements when electric fields act between the common
electrode and the respective individual electrodes; wherein the
common electrodes is separated by a groove which extends in the
specified direction.
13. The light shutter device according to claim 12, wherein suppose
each of the individual electrodes faces the common electrode at a
distance L, each of the light shutter elements is at a distance not
less than 5L from each of the individual electrodes which drive the
other light shutter elements.
14. The light shutter device according to claim 13, wherein the
distance between each of the light shutter elements and each of the
individual electrodes which drive the other light shutter elements
means the distance between a side of the light shutter element
which extends in a direction perpendicular to the direction of
electric field acting on the light shutter element and each of the
individual electrodes which drive the other light shutter
elements.
15. The light shutter device according to claim 12, wherein the
groove has a width not more than a width of the common electrode
minus 10 .mu.m.
16. The light shutter device according to claim 12, wherein the
groove has a depth not less than 5 .mu. m.
17. The light shutter device according to claim 12, wherein the
substrate with an electro-optical effect is made of PLZT.
Description
[0001] This application is based on application Nos. 11-348489 and
2000-176673 filed in Japan, the contents of which are hereby
incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a light shutter device, and
more particularly to a light shutter device which has a plurality
of light shutter elements on a substrate with an electro-optical
effect and which turns on and off the light by applying a voltage
to the light shutter elements.
[0004] 2. Description of Related Art
[0005] Conventionally, various kinds of light shutter devices have
been developed to be used to form an image on silver salt
photographic paper or film, or an electrophotographic
photosensitive member. Such a light shutter device has light
shutter chips made of PLZT, which is a material with an
electro-optical effect, arranged in an array and controls turning
on/off of the light pixel by pixel.
[0006] More specifically, as FIG. 17 shows, when a voltage is
applied between a pair of electrodes 32 and 33 provided on a light
shutter chip 30, the PLZT of the chip 30 causes birefringence. In
this state, light which is incident to a light transmitting portion
(light shutter element) 31 via a polarizer 35 which is arranged
before the light shutter chip 30, is polarized by 90 degrees, and
light is emergent from the light transmitting portion 31 and passes
through an analyzer 36. Thus, light is turned on.
[0007] When the light transmitting portion polarizes the incident
light at 90 degrees, the portion can transmit the light at the
maximum, and the voltage applied between the electrodes to achieve
the maximum quantity of transmitted light is referred to as a
half-wave voltage. Therefore, light shutter elements of this kind
are driven with the half-wave voltage applied; however, because of
crosstalk between adjacent light shutter elements, the quantity of
transmitted light fluctuates.
[0008] As far as one light shutter element is concerned, when all
the light shutter elements of the device including the element
concerned are turned on (all lighting), the light shutter element
has a light transmitting characteristic shown by the curve A in
FIG. 4a. On the other hand, when only the light shutter element
concerned is turned on (single lighting), the light shutter element
has a light transmitting characteristic shown by the curve B in
FIG. 4a. In the case of FIG. 4a, when the half-wave voltage at the
time of entire lighting is applied to the light shutter element for
single lighting, the quantity of transmitted light is reduced
approximately 12%, compared with the quantity of transmitted light
when the same voltage is applied for all lighting. There is an
approximately 25V shift in half-wave voltage between the time of
all lighting and the time of single lighting.
[0009] In order to solve the problem, Japanese Patent Laid Open
Publication No. 60-159722 suggested that shield electrodes are
provided to extend from a common electrode to among light shutter
elements. Also, Japanese Patent Laid Open Publication Nos. 58-95320
and 58-130321 suggested that grooves are provided among individual
electrodes to prevent crosstalk.
[0010] However, the former measure has the following demerits: this
is not suited to produce high-definition devices because the shield
electrodes and the individual electrodes are too close to one
another; and stray capacity occurring among the individual
electrodes and the shield electrodes are large, which results in an
increase in power consumption. Also, the latter measure has a
demerit that this is not suited to produce high-definition devices
because forming grooves among the individual electrodes complicates
the manufacturing process.
SUMMARY OF THE INVENTION
[0011] An object of the present invention is to provide a light
shutter device in which crosstalk between adjacent light shutter
elements can be suppressed and which is easy to be produced and
easy to be made into a high-definition device.
[0012] Another object of the present invention is to provide a
light shutter device which has a low half-wave voltage.
[0013] In order to attain the objects, a first light shutter device
according to the present invention comprises: a planar substrate
with an electro-optical effect; and a plurality of pairs of
electrodes provided on the substrate, portions of the substrate
between the respective pairs of electrodes functioning as light
shutter elements when electric fields act between the respective
pairs of electrodes; wherein, suppose the electrodes in each pair
are at a distance L from each other and a side which extends in a
direction perpendicular to the direction of electric field of one
of the electrodes in each pair has a dimension W, W/L> 2.
[0014] The present inventors gave an attention to the relationship
between the distance L between the electrodes in each pair and the
dimension W of one of the electrodes in each pair. In conventional
devices, W/L is around 1. As a result of experiments, however, when
W/L> 2, crosstalk between adjacent light shutter elements could
be suppressed, and there was substantially no difference in
quantity of transmitted light between a time of all lighting and a
time of single lighting. This first light shutter device according
to the present invention requires neither shield electrodes nor
grooves among the light shutter elements, and accordingly, this
device can be fabricated easily and can be made into a
high-definition device easily. Moreover, this invention is not
accompanied with an increase in power consumption, while providing
shield electrodes results in an increase in power consumption.
[0015] In the first light shutter device, further, suppose one of
the electrodes in each pair has a dimension D in the direction of
electric field, preferably D/L> 0.5. On this condition, the
half-wave voltage is lower.
[0016] A second light shutter device according to the present
invention comprises: a planar substrate with an electro-optical
effect; a common electrode which extends in a specified direction
on the substrate; and a plurality of individual electrodes which
are arranged along the common electrode so that each of the
individual electrodes faces the common electrode, portions of the
substrate between the common electrode and the respective
individual electrodes functioning as light shutter elements when
electric fields act between the common electrode and the respective
individual electrodes; wherein suppose each of the individual
electrodes faces the common electrode at a distance L, each of the
light shutter elements is at a distance not less than 5L from each
of the individual electrodes which drive the other light shutter
elements.
[0017] The present inventors gave an attention to the positional
relationship between each of the light shutter elements and the
individual electrodes which drive the other light shutter elements
and conducted various experiments about the relationship between
the distance L between each of the individual electrodes and the
common electrode, which means the dimension of each light shutter
element in the direction of electric field, and the distance
between the light shutter element and each of the individual
electrodes which drive the other light shutter elements. As a
result, when a light shutter element was located at not less than
5L from each of the individual electrodes which drive the other
light shutter elements, crosstalk between the light shutter element
and the adjacent elements could be suppressed, and the shift in
half-wave voltage and the reduction in quantity of transmitted
light at the time of single lighting were in an extent to cause
substantially no problem.
[0018] A third light shutter device according to the present
invention comprises: a planar substrate with an electro-optical
effect; a common electrode which extends in a specified direction
on the substrate; and a plurality of individual electrodes which
are arranged along both sides of the common electrode so that each
of the individual electrodes faces the common electrode, portions
of the substrate between the common electrode and the respective
individual electrodes functioning as light shutter elements when
electric fields act between the common electrode and the respective
individual electrodes; wherein the common electrode is separated by
a groove which extends in the specified direction.
[0019] Since the common electrode is separated by a groove,
crosstalk between the light shutter elements which are located on
both sides of the common electrode can be suppressed, and the
quantity of transmitted light at a time of single lighting is
almost equal to that at a time of all lighting. Forming one groove
is enough, and this does not complicate the manufacturing process
of this light shutter device.
[0020] Further, in the third light shutter device, suppose each of
the individual electrodes faces the common electrode at a distance
L, each of the light shutter elements is preferably at a distance
not less than 5L from each of the individual electrodes which drive
the other light shutter elements. With this arrangement, crosstalk
between adjacent light shutter elements can be suppressed more.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] These and other objects and features of the present
invention will be apparent from the following description with
reference to the accompanying drawings, in which:
[0022] FIG. 1 is a plan view of a principal part of a light shutter
device which is a first embodiment of the present invention;
[0023] FIG. 2 is a plan view of the light shutter device which is
covered with a shield mask;
[0024] FIG. 3 is a plan view of a principal part of a light shutter
device which is a second embodiment of the present invention;
[0025] FIGS. 4a, 4b and 4c are graphs which show the relationship
between driving voltage and quantity of transmitted light in the
first and second embodiments;
[0026] FIG. 5 is a graph which shows the relationship between W/L
and shift in half-wave voltage in the first and second
embodiments;
[0027] FIG. 6 is a graph which shows the relationship between W/L
and light quantity ratio in the first and second embodiments;
[0028] FIG. 7 is a graph which shows the relationship between D/L
and half-wave voltage in the first and second embodiments;
[0029] FIG. 8 is a plan view which shows the shape of electrodes of
a light shutter device which is a third embodiment of the present
invention;
[0030] FIG. 9 is a plan view of a principal part of a light shutter
device which is a fourth embodiment of the present invention;
[0031] FIG. 10 is a plan view of electrodes which shows the
fundamentals of placement of the electrodes in the fourth
embodiment;
[0032] FIG. 11 is a plan view of a test model according to the
fourth embodiment;
[0033] FIG. 12a and 12b are graphs which show the relationship
between driving voltage and quantity of transmitted light in the
fourth embodiment;
[0034] FIG. 13 is a plan view of a principal part of a light
shutter device which is a fifth embodiment of the present
invention;
[0035] FIG. 14 is a plan view of a principal part of a light
shutter device which is a sixth embodiment of the present
invention;
[0036] FIG. 15 is an enlarged sectional view of a light shutter
chip of the sixth embodiment;
[0037] FIG. 16 is a plan view of a principal part of a light
shutter device which is a seventh embodiment of the present
invention; and
[0038] FIG. 17 is a perspective view which shows the operation
principle of a light shutter device.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0039] Embodiments of a light shutter device according to the
present invention are described with reference to the accompanying
drawings. The embodiments below are light shutter devices which
operate (turn on and turn off the light) based on the well-known
principle illustrated in FIG. 17, and repetitious descriptions are
avoided.
First Embodiment; See FIG. 1
[0040] FIG. 1 shows a principal part of a light shutter device 1
which is a first embodiment of the present invention. This light
shutter device 1 has a plurality of light transmitting portions
(light shutter elements) 11a, 11b, . . . , which are shadowed in
FIG. 1, on a planar PLZT chip 10. The light shutter elements 11a,
11b, . . . are arranged in two lines X.sub.1 and X.sub.2
alternately, in other words, light shutter elements to form
adjacent pixels in one line of an image are arranged in mutually
different lines. The light shutter elements 11a, 11b, . . . in the
two lines are driven to be turned on and off in synchronization
with motion of a light receiving surface in a sub scanning
direction so as to form one line on the light receiving
surface.
[0041] In order to drive the light shutter elements 11a, 11b, . . .
, a common electrode 12 is provided in the center of the chip 10,
and individual electrodes 13a, 13a, . . . are provided at both
sides of the common electrode 12 with the light shutter elements
11a, 11b, . . . in-between.
[0042] The gap between the common electrode 12 and each of the
individual electrodes 13a, 13a, . . . is supposed to be L, and the
dimension of the individual electrodes 13a, 13a, . . . in the
direction perpendicular to the direction of electric field is
supposed to be W. According to an experiment conducted by the
inventors, when L and W were so designed that W/L would be over 2,
the mutual influences of the electric fields which occur on the
respective light shutter elements 11a, 11b, . . . could be
inhibited, and crosstalk could be suppressed.
[0043] In the first embodiment shown by FIG. 1, W/L is 4.7. The
relationship between driving voltage and quantity of transmitted
light in this embodiment is shown by FIG. 4b. In FIG. 4b, the curve
A shows a light transmitting characteristic of one of the light
shutter elements when all the light shutter elements are turned on,
and the curve B shows a light transmitting characteristic of the
light shutter element when only the light shutter element is turned
on. Compared with the case of FIG. 4a, in the first embodiment in
which W/L is 4.7, although there is a slight difference between the
characteristic curves A and B in shape, there are almost no
differences between the curves A and B in half-wave voltage and
maximum quantity of light.
Second Embodiment; See FIG. 3
[0044] FIG. 3 shows a principal part of a light shutter device 2
which is a second embodiment of the present invention. This light
shutter device 2 has a plurality of light transmitting portions
(light shutter elements) 11a, 11b, . . . , which are shadowed in
FIG. 3, on a planar PLZT chip 10. The light shutter elements 11a,
11b, . . . are arranged in four lines X.sub.1, X.sub.2, X.sub.3 and
X.sub.4 in such a way that light shutter elements to form adjacent
pixels in one line of an image are arranged in mutually different
lines. The light shutter elements 11a, 11b, . . . in the four lines
are driven to be turned on and off in synchronization with motion
of a light receiving surface in a sub scanning direction so as to
form one line on the light receiving surface.
[0045] In the second embodiment, the common electrode 12 has
extensions 12' which are drawn from both sides of the central
portion of the common electrode 12. The individual electrodes 13a,
13a, . . . face the central portion or the extensions 12' of the
common electrode 12. According to an experiment using the second
embodiment, by setting W/L over 2, the mutual influences of the
electric fields which occur on the respective light shutter
elements 11a, 11b, . . . could be inhibited, and crosstalk could be
suppressed.
[0046] In the second embodiment shown by FIG. 3, W/L is 7. The
relationship between driving voltage and quantity of transmitted
light in this embodiment is shown by FIG. 4c. The curve A in FIG.
4c shows a characteristic of one of the light shutter elements 11a,
11b, . . . when all the light shutter elements 11a, 11b, . . . are
turned on, and the curve B shows a characteristic of the light
shutter element when only the light shutter element is turned on.
Compared with the case of FIG. 4a, in the second embodiment in
which W/L is 7, although there is a slight difference between the
characteristic curves A and B in shape, there are almost no
differences between the curves A and B in half-wave voltage and
maximum quantity of light.
Shield Mask; See FIG. 2
[0047] When the light shutter devices 1 and 2 are installed in
printers, as FIG. 2 shows (FIG. 2 shows the first embodiment),
shield masks 20 which cover the respective light shutter devices
other than the light shutter elements 11a, 11b, . . . are
provided.
[0048] The shield mask 20 can be formed by forming a film on the
chip 10 and by making holes in the film on the light shutter
elements 11a, 11b, . . . by photolithography. An insulating and
light shielding material shall be selected for the film. For
example, resin on which a black pigment is dispersed is usable.
Also, a mask plate on which a shield film is patterned may be
placed on the chip 10 as the shield mask 20, and other various
shielding ways can be adopted.
Width and Placement of Light Shutter Elements
[0049] The width of the light shutter elements 11a, 11b, . . . ,
that is, the dimension of the light shutter elements in the main
scanning direction is determined depending on the image resolution.
For example, if the image resolution is 400 dpi, the width is 63.5
.mu.m, and if the image resolution is 600 dpi, the width is 42
.mu.m. Each of the light shutter elements is preferably positioned
in the center of the dimension W of the corresponding individual
electrode. In the above-described first embodiment and the second
embodiment, the image resolution is 400 dpi.
Dependency of Crosstalk on W/L
[0050] FIGS. 5 and 6 show the results of experiments. FIG. 5 shows
the relationship between W/L and half-wave voltage shift .DELTA.Vd
between the time of all lighting and the time of single lighting.
FIG. 6 shows the relationship between W/L and the rate of the
quantity of transmitted light at the time of single lighting to
that at the time of all lighting.
[0051] As is apparent from FIGS. 5 and 6, the larger W/L is, the
smaller crosstalk is. There are no practical problems when W/L>
2.
[0052] The value W/L can be set smaller by setting the value L
smaller. That L is small means that the area of the portion
functioning as a light shutter element is small, and if L is too
small, the illumination system will have too much burden to achieve
a sufficient quantity of transmitted light. Practically, L is
preferably not less than 5 .mu.m and shall be determined in
consideration for other factors of the print system and the desired
performance as a light shutter.
Dependency of Half-wave Voltage on D/L
[0053] If the individual electrodes 13a, 13a, . . . in the first
and second embodiments have a dimension D in the direction of
electric field, the value D/L influences the half-wave voltage.
FIG. 7 shows the results of an experiment about the relationship
between D/L and half-wave voltage Vd. Table 1 shows the values D,
D/L and Vd at the points "a" through "h" in the graph of FIG.
7.
1TABLE 1 D (.mu.m) D/L Vd 197 4.477 135 147 3.341 135 93 2.114 138
64 1.455 139 46 1.045 140 26 0.591 150 16 0.364 170 5 0.114 200
[0054] As is apparent from FIG. 7, when D/L becomes less than
approximately 0.5, the half-wave voltage Vd suddenly rises.
Accordingly, by designing the individual electrodes 13a, 13a, . . .
so that D/L>0.5, the driving voltage can be kept low. There are
no particular limitations on the maximum of D/L; however, the value
D/L shall be determined in consideration for the size of the chip
10.
Third Embodiment; See FIG. 8
[0055] The electrodes may be of the shape shown by FIG. 8, in which
large electrodes 12 and small electrodes 13 face each other. In
this case, even if the large electrodes 12 satisfy the conditions
W.sub.2/L>2 and D.sub.2/L>0.5, if the small electrodes 13 are
on the conditions W.sub.1/L< 2 and D.sub.1/L< 0.5, it is not
possible to suppress crosstalk. It is necessary that the small
electrodes 13 satisfy the conditions W.sub.1/L>2 and
D.sub.1/L>0.5.
Fourth Embodiment; FIGS. 9-12
[0056] FIG. 9 shows a principal part of a light shutter device 3
which is a fourth embodiment of the present invention. In the light
shutter device 3, a plurality of light shutter elements 11a, 11b, .
. . are arranged in four lines X.sub.1, X.sub.2, X.sub.3 and
X.sub.4 as in the second embodiment (see FIG. 3).
[0057] The characteristic of the fourth embodiment is described
referring to FIG. 10. The electrodes 12 and 13a to drive the light
shutter element 11a have a gap L in-between. The individual
electrode 13c to drive the light shutter element 11c is positioned
at a distance not less than 5L from the sides 11a.sub.1 and
11a.sub.2 of the light shutter element 11a. In other words, within
an area A at a distance not less than 5L from the sides of a light
shutter element, no other individual electrodes are arranged.
[0058] The reason why no other individual electrodes are arranged
within the area A is described. The inventors fabricated a model
shown by FIG. 11, and the driving voltage and the quantity of
transmitted light were measured. In order to drive a light shutter
element 11, an electric field was applied between a common
electrode 12 and an individual electrode 13. Another electrode 13'
was provided at a distance M from the light shutter element 11.
While fixing the distance L between the electrodes 12 and 13 at 20
.mu.m and at 40 .mu.m and changing the distance M between 50 .mu.m
and 250 .mu.m, the driving voltage and the quantity of transmitted
light were measured to figure out the half-wave voltage. These
measurements were carried out on the first condition that the
electrode 13' has the same potential as the individual electrode 13
(corresponding to all lighting) and on the second condition that
the electrode 13' has the same potential as the common electrode 12
(corresponding to single lighting). A difference in half-wave
voltage Vd between a case on the first condition and a case on the
second condition is referred to as a shift voltage .DELTA. Vd.
[0059] The results of the experiment is partly shown by FIGS. 12a
and 12b. FIG. 12a shows a case in which L=20 .mu.m and M=70 .mu.m
on the first condition, and in this case, the half-wave voltage was
100V. FIG. 12b shows a case in which L and M are the same as in the
case of FIG. 12a on the second condition, and in this case, the
half-wave voltage was 130V. The shift voltage .DELTA.Vd was
30V.
[0060] Table 2 shows the relationship between distance M and shift
voltage .DELTA. Vd when L=20 .mu.m and when L=40 .mu.m.
2 TABLE 2 M (.mu.m) L (.mu.m) 50 70 100 140 170 200 230 250 20 50 V
30 V 8 V 5 V 0 C 0 V -- -- 40 -- -- 45 V 30 V 15 V 5 V 0 V 0 V
[0061] It is ideal that the shift voltage .DELTA. Vd is zero (which
means that there is no crosstalk); however, if the shift voltage
.DELTA. Vd is not more than 10V, the quantity of transmitted light
decreases only by at most 5%, which is practically no problem.
Therefore, the distance M shall be not less than five times the
distance L.
[0062] In the fourth embodiment, the shift voltage .DELTA. Vd was
8V, and the quantity of transmitted light decreased by 3%.
Fifth Embodiment; See FIG. 13
[0063] FIG. 13 shows a princiapal part of a light shutter device 4
which is a fifth embodiment of the present invention. This light
shutter device 4 is basically of the same structure as the fourth
embodiment shown by FIG. 9. However, the width of the extensions
12' of the common electrode 12 and the width of the individual
electrodes 13a, 13a, . . . are smaller than those of the fourth
embodiment, and the width of the central portion of the common
electrode 12 is larger than that of the fourth embodiment. The
individual electrodes 13a, 13a, ... are arranged out of the areas
A, that is, each of the individual electrodes is positioned at a
distance not less than 5L from the light shutter elements driven by
the other individual electrodes. In the fifth embodiment, the shift
voltage A Vd was 5V, and the quantity of transmitted light
decreased by 2%.
Sixth Embodiment; FIGS. 14 and 15
[0064] FIG. 14 shows a principal part of a light shutter device 5
which is a sixth embodiment of the present invention. The light
shutter device 5 is basically of the same structure as the first
embodiment shown by FIG. 1. The difference is that a groove 12a is
formed in the center of the common electrode 12. By separating the
common electrode 12 by the groove 12a, crosstalk between the light
shutter elements which are arranged on both sides of the common
electrode 12 can be suppressed.
[0065] In the sixth embodiment, the common electrode 12 has a width
of 60 .mu.m, and a groove 12a with a width of 25 .mu.m and a depth
of 50 .mu.m is formed. The groove 12a may be formed by cutting,
etching (plasma etching, reactive ion etching, wet etching, etc.)
or sand blasting. In the sixth embodiment, the shift voltage
.DELTA. Vd was 0V, and the reduction in quantity of transmitted
light was 0%.
[0066] The width of the groove 12a is preferably not more than the
width of the common electrode 12 minus 10 .mu.m, and the depth of
the groove 12a is preferably not less than 5 .mu.m. If the depth is
less than 5 .mu.m, the effect of suppressing crosstalk is weak.
Seventh Embodiment; See FIG. 16
[0067] FIG. 17 shows a principal part of a light shutter device 6
which is a seventh embodiment of the present invention. This light
shutter device 6 is basically of the same structure as the light
shutter device 4 of the fifth embodiment. In the seventh
embodiment, further, a groove 12a is formed in the common electrode
12. The groove 12a is the same as the groove in the sixth
embodiment. In the seventh embodiment, the shift voltage .DELTA.Vd
was 0.2V, and the reduction in quantity of transmitted light was
0%.
Other Embodiments
[0068] As the material with an electro-optical effect, not only
PLZT but also LiNbO.sub.3 and others are usable. The number of
lines of the light transmitting portions (light shutter elements)
and the details of the electrode pattern are arbitrary.
[0069] Although the present invention has been described in
connection with the preferred embodiments above, it is to be noted
that various changes and modifications are possible to those who
are skilled in the art. Such changes and modifications are to be
understood as being within the scope of the present invention.
* * * * *