Photography – Camera detail – Shutter
Reexamination Certificate
2001-04-19
2003-05-13
Gray, David M. (Department: 2851)
Photography
Camera detail
Shutter
C359S271000, C359S323000, C349S056000
Reexamination Certificate
active
06561703
ABSTRACT:
This application is based on application No. JP 2000-125703 filed in Japan, the contents of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improved light shutter device, and more particularly, to an improved light shutter device driving method Specifically, it relates to a light shutter device driving method, and more particularly, to a light shutter device that comprises multiple light shutter elements located on a substrate made of a material having an electro-optical effect, wherein the ON/OFF control of light is carried out through the action on each light shutter element of an electrical field generated from a pair of electrodes, as well as to a driving method for such light shutter device.
2. Description of the Related Art
Various light shutter devices are provided that comprise light shutter substrates made of PLZT, a material that has an electro-optical effect, in an array and in which light is turned ON/OFF on an individual pixel basis in order to form an image on photographic paper or film using a silver halide material or on an electronic photosensitive medium.
A specific principle is shown in FIG.
9
. When no voltage is applied to the pair of electrodes
14
and
15
located on the light shutter chip
12
, the incident light is blocked by the polarizer
5
located in front of the light shutter chip and the analyzer
7
located on the light exit side, and therefore such light does not exit from the chip. When a voltage is applied to the electrodes
14
and
15
, double refraction occurs in the light that enters the PLZT. The light that enters the light transmitting area (light shutter element)
13
through the polarizer
5
is polarized 90 degrees by the light shutter chip
12
such that the light passes through the analyzer
7
. Through this operation, the light shutter device turns ON/OFF.
One example of the electrode construction on the conventional light shutter chip
12
is shown in FIG.
10
. In this chip
12
, light shutter elements
13
(
13
a
,
13
b . . .
) are alternately located on the lines X, X that divide the one line image data into two, a common electrode
14
, which is connected to ground and is formed therebetween, and individual electrodes
15
(
15
a
,
15
b . . .
), to each of which a prescribed voltage is individually applied and which are formed such that the light shutter elements
13
are situated between the individual electrodes
15
.
In each light shutter element, the largest amount of pass-through light may be obtained when the incident light is polarized by 90 degrees. The voltage applied to cause this polarization is called half-wavelength voltage. Therefore, driving of this type of light shutter element is carried out using the half-wavelength voltage with which the pass-through light amount is maximized, but a phenomenon occurs in which the half-wavelength voltage and pass-through light amount fluctuate due to the effect of the electrical fields that extend from the adjacent elements (in this specification, this phenomenon is called cross-talk).
For example, to focus on one element
13
e
in
FIG. 10
, the lit state (i.e., the amount of pass-through light) of the element
13
e
should be determined based on the voltage (electrical field) applied to the individual electrode
15
e
and the common electrode
14
. However, when the elements
13
c
and
13
g
that are adjacent to the element
13
e
on the line X are also lit, the electrical fields from the individual electrodes
15
c
and
15
g
also extend to the element
13
e
. Consequently, the half-wavelength voltage by which to drive the element
13
e
and the amount of pass-through light passing therethrough undergo changes depending on the ON/OFF state of the adjacent elements
13
c
and
13
g.
Such cross-talk does not ordinarily take place between elements that face each other across the common electrode
14
, because the common electrode
14
operates as an electrical field barrier. However, where the common electrode
14
is narrow, it is possible for the electrical fields from the individual electrodes
15
d
and
15
f
that face the element
13
e
across the common electrode
14
to extend to the element
13
e
, causing a cross-talk phenomenon.
FIG. 11
shows the relationship between the voltage applied to the target element
13
e
and the amount of pass-through light passing therethrough.
FIG. 12
shows the waveforms of the voltages applied to the elements
13
c
,
13
e
and
13
g
, respectively, and the photoresponse waveform of the element
13
e
for each one line image draw cycle.
Characteristic A shown in
FIG. 11
indicates the case in which both the adjacent elements
13
c
and
13
g
, as well as the element
13
e
, are simultaneously turned ON, and corresponds to the first cycle in FIG.
12
. Characteristic B indicates the case in which either adjacent element
13
c
or
13
g
is turned ON, and corresponds to the second or third cycle in FIG.
12
. Characteristic C indicates the case in which both adjacent elements
13
c
and
13
g
are turned OFF, and corresponds to the fourth cycle in FIG.
12
.
As is clear from these characteristics A, B and C, the half-wavelength voltage and the pass-through light amount of the element
13
e
change depending on the states of operation of the adjacent elements
13
c
and
13
g
. For example, where the element
13
e
is driven using the half-wavelength voltage (approximately 142V) when the elements
13
c
and
13
g
are simultaneously turned ON, if either element
13
c
or
13
g
is OFF, the element
13
e
pass-through light amount is reduced by approximately 5%, and if both of the elements 13
c
and
13
g
are OFF, the element
13
e
pass-through light amount is reduced by approximately 16%.
OBJECTS AND SUMMARY
The present invention was made in view of these circumstances, and an object hereof is to provide an improved light shutter device. Another object of the present invention is to provide an improved light shutter device driving method. More specifically, an object of the present invention is to provide a light shutter device and driving method therefor in which the cross-talk phenomenon in which the light shutter elements affect each other may be effectively prevented and the amount of pass-through light of each light shutter element is stabilized.
In order to attain these and other objects, one aspect of the present invention is a driving method for a light shutter device comprising multiple light shutter elements located on a substrate made of a material having an electro-optical effect, wherein light is controlled to turn ON/OFF through the action of an electrical field generated from a pair of electrodes on each light shutter element, and wherein an electrical field does not operate essentially simultaneously on light shutter elements as to which the cross-talk phenomenon occurs in their respective electrical fields.
In the driving method pertaining to the above aspect, an electrical field does not operate essentially simultaneously on light shutter elements that experience a mutual cross-talk effect. Therefore, each light shutter element can obtain a constant amount of pass-through light at all times based on the application of a constant voltage to the electrodes, resulting in the formation of high-quality images.
The concept that ‘an electrical field does not operate essentially simultaneously’ includes the case in which the effect of cross-talk does not appear in the image as a practical matter even if the electrical fields of the elements overlap slightly, as well as the case in which the actions of each electrical field on each light shutter element are completely separate from each other.
In order to perform driving while ensuring that each electrical field does not affect more than one element at the same time, it is preferred from the viewpoint of simplified driving that one line cycle be divided into at least two periods and that the light shutter elements that experience mutual cross-talk be alternately turned ON in eac
Kamoda Yuji
Masuda Tomohiko
Saito Itaru
Yagi Tsukasa
Blackman Rochelle
Gray David M.
Minolta Co. , Ltd.
Sidley Austin Brown & Wood LLP
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