Light shutter device

This application is based on application No. 11-200018 filed in Japan, the content of which is hereby incorporated by reference.

1. Field of the Invention

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 made of a material with an electro-optical effect and which controls turning-on and turning-off of the light by applying a voltage to the light shutter elements.

2. Description of Prior Art

There have been provided various kinds of light shutter devices to form an image on a silver salt print paper, a silver salt film or a photosensitive member. Such a light shutter device has arrays of light shutter tips made of PLZT, which has an electro-optical effect, and controls turning-on and turning-off pixel by pixel.

Specifically, as FIG. 5 shows, when a voltage is applied to a pair of electrodes 32 and 33 provided on a light shutter tip 30 , birefringence by the PLZT of the light shutter tip 30 becomes possible. In this state, light which is incident to a light transmitting portion (light shutter element) 31 via a polarizer 35 is polarized by the PLZT at 90 degrees, and the light emergent from the light transmitting portion 31 passes through an analyzer 36 . In this way, light is turned on and off.

FIG. 6 shows an example of the electrode structure of a conventional light shutter tip. In the tip 30 , in two scan lines X to write one line, light shutter elements 31 a, 31 b, . . . are arranged. On respective one sides of the light shutter elements, individual electrodes 32 a, 32 b, . . . are provided, and on the other sides, a common electrode 33 which is connected to the ground is provided.

Such light shutter elements are driven with a half-wave voltage applied thereto so as to obtain the maximum light transmittance; however, crosstalk occurs between adjacent light shutter elements on each of the scan lines X, which fluctuates the light transmittance. For example, focusing on the element 31 c, the light transmittance characteristic when only the element 31 c is turned on is shown by the curve A in FIG. 7 . The curve B in FIG. 7 shows the light transmittance characteristic of the element 31 c when the neighboring elements are also turned on simultaneously with the element 31 c; in this case, the light transmittance decreases. The light transmittance of the element 31 c when a half-wave voltage is applied to the element 31 c and the neighboring elements is approximately 10% lower than that when the half-wave voltage is applied only to the element 31 c.

In order to solve this problem, as FIG. 8 shows and as Japanese Patent Laid Open Publication No. 60-159722 suggested, shield electrodes 34 a, 34 b . . . which extend from the common electrode 33 to among the light shutter elements 31 a, 31 b . . . are provided. FIG. 8 shows only the part around one of the two scan lines X.

In this structure, however, the shield electrodes 34 a, 34 b . . . and the individual electrodes 32 a, 32 b . . . are very close to each other, and it is difficult to adapt this structure for a high-definition device. Also, large capacitance occurs among the individual electrodes and the shield electrodes, which results in an increase in electric power consumption. Moreover, as the shield electrodes are thinned, the effect becomes weak, and in this point, also, this structure is not suited for a high-definition device.

An object of the present invention is to provide a light shutter device which inhibits crosstalk from occurring between adjacent light shutter elements, which can be adopted to achieve high definition and which does not increase electric power consumption.

In order to attain the object, a light shutter device according to the present invention comprises: a substrate made of a material with an electro-optical effect; a common electrode which extends in a specified direction on the substrate; a plurality of individual electrodes which are arranged by a side of the common electrode along the common electrode; and a plurality of light shutter elements which are located between the respective individual electrodes and the common electrode and which are driven by application of a voltage between the respective individual electrodes and the common electrode. In the light shutter device, the light shutter elements are arranged in such a way that adjacent light shutter elements are located in mutually different positions with respect to a direction perpendicular to the common electrode extending direction.

In the structure, since adjacent light shutter elements are arranged in mutually different lines in parallel to the common electrode extending direction, the distances among the elements are long. Therefore, the crosstalk among the elements is small, and the light transmittance of each element when all the elements are turned on is the same as that when only one element is turned on. Moreover, it is not necessary to provide shield electrodes among the elements, which means that adaptation for a high-definition device is possible and that the consumption of electric power does not increase.

This and other objects and features of the present invention will be apparent from the following description with reference to the accompanying drawings, in which:

FIG. 1 is a plan view of the principal part of a light shutter device which is a first embodiment of the present invention;

FIG. 2 is a graph which shows the relationship between the driving voltage and the light transmittance in the light shutter device;

FIG. 3 is a plan view of the principal part of a light shutter device which is a second embodiment of the present invention;

FIG. 4 is a plan view of the principal part of a light shutter device which is a third embodiment of the present invention;

FIG. 5 is a perspective view which shows the principle of operation of a light shutter device;

FIG. 6 is a plan view of a conventional light shutter device;

FIG. 7 is a graph which shows the relationship between the driving voltage and the light transmittance in the light shutter device of FIG. 6; and

FIG. 8 is a plan view of another conventional light shutter device.

Preferred embodiments of a light shutter device according to the present invention are described with reference to the accompanying drawings. The embodiments operate (turn on and off the light) in the well-known principle shown by FIG. 5, and repetition of the description will be avoided.

First Embodiment; See FIG. 1

FIG. 1 shows the principal part of a light shutter device which is a first embodiment of the present invention. In the light shutter device, on a planar PLZT tip 10 , a plurality of light transmitting portions (light shutter elements) 11 a, 11 b, . . . are arranged in two pairs of scan lines X 1 and X 2 , and adjacent elements are arranged in mutually different lines. Each pair of scan lines X 1 and X 2 correspond to each of the scan lines X shown in FIG. 6 .

In accordance with the arrangement of the elements 11 a, 11 b, . . . , individual electrodes 12 a, 12 b, . . . and a common electrode 13 are patterned.

The light shutter elements 11 a, 11 b, . . . , which belong to one scan line X in the conventional structure shown by FIG. 6, are arranged in two lines X 1 and X 2 alternately in the first embodiment. Therefore, the distances among the elements are long. Also, the common electrode 13 extend to the vicinity of each of the elements, which brings a shield effect. Thereby, crosstalk at the time of application of a voltage is inhibited, and the consumption of electric power is reduced.

FIG. 2 shows the relationship between the driving voltage and the light transmittance in the first embodiment. Here, the distance between the centers of two adjacent light shutter elements is approximately 1.25 times of that in the conventional structure shown by FIG. 6 . In FIG. 2, the curve A shows the light transmittance characteristic of a light shutter element when only the element is turned on, and the curve B shows the light transmittance characteristic of the light shutter element when the element and the neighboring elements are turned on. As is apparent from these curves A and B, substantially, neither fluctuation of the half-wave voltage nor reduction of the light transmittance occurs.

The crosstalk decreases in inverse proportion to the distances among the light shutter elements, and when the distances among the light shutter elements are approximately 1.5 times of those in the conventional structure shown by FIG. 6, there occurs almost no crosstalk. As the distances among the light shutter elements become longer, however, the power of the light source must be strengthened. Accordingly, the distances among the elements shall be designed in consideration for the shutter performance and other factors.

In the first embodiment, since the pixels which are arranged on one line X in the conventional structure are arranged in two lines X 1 and X 2 alternately, it is necessary to produce image signals for the respective lines X 1 and X 2 . In order to write one line on a receiving surface, the total of four scan lines are controlled with time lags.

Second Embodiment

FIG. 3 shows the principal part (corresponding to the part around one scan line X in the conventional structure) of a light shutter device which is a second embodiment of the present invention. In the light shutter device, the light shutter elements 11 a, 11 b, . . . , which are arranged in one scan line X in the conventional structure, are arranged in three lines X 1 , X 2 and X 3 , and adjacent elements are arranged in the three lines X 1 , X 2 and X 3 in this order. The second embodiment acts in the same way and brings the same effect as the first embodiment.

Third Embodiment

FIG. 4 shows the principal part (corresponding to the part around one scan line X in the conventional structure) of a light shutter device which is a third embodiment of the present invention. In the light shutter device, the light shutter elements 11 a, 11 b, . . . , which are arranged in one scan line X in the conventional structure, are arranged in three lines X 1 , X 2 and X 3 as those of the second embodiment are; however, adjacent elements are arranged on X 1 , X 2 , X 3 , X 3 , X 2 , X 1 , . . . in this order. The third embodiment acts in the same way and brings the same effect as the first embodiment and the second embodiment.

Other Embodiments

As the material with an electro-optical effect, LiNbO 3 as well as PLZT are usable. The number of lines in which the light transmitting portions (light shutter elements) are arranged and the details of the electrode pattern are arbitrary.

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 understood as being within the scope of the present invention.