JPH0458007B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical shutter array element, and in particular is aimed at reducing the capacity thereof.

A conventional structure of an optical shutter array is shown in FIG.

In the figure, 1 is a polarizer, 2 is a ferroelectric substrate made of transparent ceramics such as PLZT and has an electro-optic effect, 3 is an analyzer, and ferroelectric substrate 2
is arranged between the polarizer 1 and the analyzer 3. The polarizer 1 and the analyzer 3 are arranged so that their optical axes are perpendicular to each other. A plurality of parallel electrodes 4 and 5 are formed on the surface of the ferroelectric substrate 2 so as to be inserted into each other from one side to the other, thereby forming an optical shutter array element. By applying a voltage between the electrodes 4 and 5, light passes through the region between the electrodes 4 and 5, and by removing the voltage application, the light is blocked.

FIG. 2 shows the specific structure of the ferroelectric substrate 2 described above.

The numbers shown in Figure 2 correspond to those in Figure 1.
In the figure, area A corresponds to the optical shutter portion. The equivalent circuit is shown in FIG. 4 based on FIG. 3, which is an enlarged view of area B in FIG. 2.

In FIG. 4, the capacitances C ₁ and C ₂ will be explained as follows. That is, the capacitance _C1 is the capacitance between the electrodes 4 and 5 formed by inserting them into each other from one side to the other, and this insertion area is the optical switching area of the optical shutter array element corresponding to area A in FIG. It is an active area involved in In addition, the capacitance C ₂ is formed by electrodes extending from the same direction, that is, electrodes 4 and 4, or electrodes 5 and 5.
This is the capacity between the drawer portions excluding area A in FIG. 2 for five comrades.

Here, among the electrodes 4 and 5 in FIGS. 3 and 4,
Especially when looking at the electrodes 4a and 5a, the electrodes 4a,
The capacitance between electrode 5a is the capacitance C ₁ of area A, and the capacitance between electrode 4b
Capacitance C ₁ C ₂ /(C ₁ +C ₂ ) generated through electrode 5b
The capacitance C ₁ C ₂ /(C ₁ +C ₂ ) generated through the electrodes 4a, 4b and the capacitances generated through the other electrodes 4 and 5 other than the electrodes 5a and 5b are synthesized.

According to the formation pattern of the electrodes 4 and 5 as shown in the figure, the distance D between the electrodes 4 and 4 and between the electrodes 5 and 5 can be kept secret compared to the case where the electrodes 4 and 5 are formed extending from the same direction. Capacity
Since the value of C ₂ can be reduced to some extent,
The value of capacitance C ₂ can be reduced to some extent.
Regarding these capacitances C ₁ and C ₂ , electrodes 4 and 5
, the distance between the electrodes 4 and 5, and the length of the lead-out portions of the electrodes 4 and 5, but they are generally in a relationship that cannot be ignored.

On the other hand, a transparent ceramic such as PLZT is used for the ferroelectric substrate 2 having an electro-optic effect, but for example, the dielectric constant of a material made of a ratio of 9/65/35 (La/Zr/Ti) is 100 KHz at room temperature. in
Since it has a value of 4600, the above structure has a capacitance of
C ₁ and C ₂ will be large. However, when the capacitance between the electrodes 4 and 5 increases as described above, there are drawbacks such as a slow switching speed and an increase in the load on the power supply capacity.

Therefore, the present invention includes a region of a ferroelectric substrate having an electro-optic effect excluding the optical shutter portion.
By forming an insulating layer with a low dielectric constant, the capacitance between the electrodes is reduced and the capacitance is lowered.

The outline of the structure of the present invention is as follows. That is, the optical shutter array element according to the present invention basically consists of a plurality of parallel linear electrodes on a ferroelectric substrate having an electro-optic effect. are formed so that they are inserted into each other from one side to the other, and this insertion area constitutes a light shutter portion. The improvement is that an insulating layer with a low dielectric constant is formed in the area above the ferroelectric substrate having an electro-optic effect, excluding the optical irradiator part, and the plurality of parallel linear lines are formed on this insulating layer. The present invention is characterized in that the electrodes are formed so as to extend to the edge side of the ferroelectric substrate having the electro-optic effect, and the tips of the plurality of parallel line electrodes are formed so as to reach the insulating layer on the other side.

According to the optical shutter array element according to the present invention, the electrodes are formed so as to be inserted into each other, and the insertion area constitutes an optical shutter, and a ferroelectric substrate having an electro-optic effect excluding the optical shutter portion is formed. An insulating layer with a low dielectric constant is formed in the upper region, and a plurality of parallel linear electrodes are formed on the insulating layer so as to extend to the edge side of the ferroelectric substrate having an electro-optic effect, and Since the tips of the parallel line electrodes are formed so as to reach the insulating layer on the other side, a parallel electric field is formed between adjacent electrodes in the light shutter area, and a parallel electric field is formed between the electrodes in the insertion area. By turning the voltage application on and off, an electric field is applied, and effective light switching can be performed. Moreover,
Even if there is a lead-out part of the electrodes or a region between the electrodes 4 and 4 or between the electrodes 5 and 5, the capacitance can be reduced by the insulating layer, and a decrease in switching speed can be suppressed. .

Hereinafter, this invention will be explained in detail based on one embodiment.

FIG. 5 is an enlarged view of a part of the optical shutter array element according to the present invention. To explain according to the figure, 11 is a ferroelectric substrate having an electro-optic effect, 12a to 12c, 13a to 13d are inserted into each other. A plurality of parallel line-shaped electrodes 14 formed in an open state are an insulating layer having a low dielectric constant. This insulating layer 14 is connected to the ferroelectric substrate 11 and the electrodes 12a to 12c, 13a to 1 except for the optical shutter portion S which is the insertion area of the electrodes 12a to 12c and 13a to 13d.
3d. In addition, the electrode 12a
The tips of ~12c and 13a~13d are formed so as to reach the opposing insulating layer 14, respectively.
For example, SiO ₂ is selected as the insulating layer 14 considering its low dielectric constant and ease of formation.

As a specific example, as the ferroelectric substrate 11, La/
A transparent ceramic made of PLZT with a Zr/Ti ratio of 9/65/35 and a thickness of 300 μm was used. On this ferroelectric substrate 11, except for the optical shutter portion S,
An insulating layer 14 made of SiO ₂ was formed by electron beam evaporation. The thicker the SiO ₂ film is, the better, but in this case there will be a step between the electrode that will be formed later and the ferroelectric substrate 11.
The thickness was 3 μm. Next, Al was vacuum-deposited and etched so that the electrode width was 60 μm and the electrode spacing was 40 μm.
3d was formed.

Regarding the optical shutter array element thus obtained, for example, all electrodes other than electrode 13b were grounded, and the capacitance between electrode 13b and the ground side was measured and found to be about 290 pF. For comparison, the capacitance was similarly measured for an example in which no insulating film made of SiO ₂ was formed, and it was approximately 570 pF.

If calculated from these actual measurements, the electrode 12
The capacitance C ₁ between electrode 13b and electrode 13b is about 130 pF, while the capacitance C ₂ between electrode 13b and electrode 13c is about 10 pF.
The calculated value is obtained. Note that in an example in which an insulating film made of SiO ₂ is not formed, the capacitance C ₂ is approximately 150 pF.

FIG. 6 shows another embodiment of the invention. In other words, the density of the optical shutter portion S is increased, and the electrode 1
In order to secure bonding portions near the edges of the ferroelectric substrates 11 in Nos. 2 and 13, it is conceivable that electrodes are formed radially toward the edges of the ferroelectric substrates 11 as shown in FIG. . In this case, the electrodes 12 and 13 near the center of the ferroelectric substrate 11
This results in a difference in the lengths l ₁ and l ₂ of the respective lead-out portions of the electrodes 12 and 1 that are located away from the center position, and variations occur in the capacitance C ₂ between the lead-out portions. In order to overcome such disadvantages, the present invention has the advantage that the capacitance C ₂ is much smaller than the capacitance C ₁ , so that the variation in the capacitance as a whole can be reduced.

As is clear from the above embodiments, the optical shutter array element according to the present invention can reduce the capacitance generated between the electrodes, thereby increasing the switching speed.
It is possible to reduce the capacity of the power supply.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view showing the conventional structure of an optical shutter array, FIG. 2 is a plan view of a ferroelectric substrate having an electro-optic effect, FIG. 3 is a partially enlarged plan view of FIG. 2, and FIG. 3 is an equivalent circuit diagram, FIG. 5 is a partial plan view of an optical shutter array element according to the present invention, and FIG. 6 is a schematic plan view showing another embodiment of the optical shutter array element. 11 is a ferroelectric substrate having an electro-optic effect, 1
2a to 12c and 13a to 13d are electrodes, and 14 is an insulating film.

Claims (1)

[Claims] 1. On a ferroelectric substrate having an electro-optic effect,
In an optical shutter array element in which a plurality of parallel line-shaped electrodes are inserted into each other from one side to the other, and the optical shutter part is formed in this insertion area, the electro-optic effect excluding the optical shutter part can be obtained. an insulating layer with a low dielectric constant is formed in a region on the ferroelectric substrate having the electro-optic effect, and the plurality of parallel line electrodes are formed on the insulating layer on the edge side of the ferroelectric substrate having the electro-optical effect. 1. A light shutter array element, characterized in that the plurality of parallel line electrodes are formed so as to extend up to 100 degrees and such that tips of the plurality of parallel line electrodes reach an insulating layer on the other side.