JPS5810717A - Optical shutter - Google Patents

Abstract

PURPOSE:To keep always the quantity of transmitted light constant, by detecting the variance of the temperature of a substrate due to an electrostrictive material and controlling the voltage applied to the electrode on the substrate on the basis of the detection signal by a voltage controller. CONSTITUTION:In the PLZT optical shutter where a substrate 3 consisting of an electrostrictive material where an electrode 4 for voltage application is formed is arranged between a pair of polarizers 1 and 2, the variance of the temperature of the substrate 3 is detected by a thermosensitive element 7. When the temperature of the substrate 3 rises more than the initial temperature of 25 deg.C, a temperature correcting circuit 8 controls a high-voltage power supply circuit 5 on the basis of a detection signal SD from the thermosensitive element 7 so that the output voltage from the high-voltage power supply circuit 5 rises. As the result, the voltage applied to the electrode 4 is raised, and the double refractive index of the substrate 3 is kept constant. When the temperature of the substrate 3 falls, the applied voltage is dropped to keep the double refractive index constant, and thus, a quantityIof transmitted light from the polarizer 2 is kept constant independently of the variance of the temperature of the substrate 3.

Description

[Detailed description of the invention] The present invention relates to an optical shutter.

Conventionally, as an example of an optical shutter, as shown in FIG. 1, a pair of polarizers (1) (2) Seki KPLZT substrate (3) t-
The next electrode (4) is arranged on this PLZT substrate (3).
), a PLZT optical shutter is known in which a constant voltage is applied such that the voltage application direction is at 45° with respect to the vibration plane of polarized light. With this configuration, the electrode (4)
If no voltage is applied between them, light will be blocked, and if a voltage is applied, a certain amount of light will pass through the polarizers (1) and (2). Here, what is PLZT (P4, La)
(24%Tb) It is an abbreviation for Os porcelain, and due to its composition, it has a cy-order/second-order electro-optic effect and an optical memory function, so it is expected to be applied to optical fields such as optical shutters and displays. The PLZT optical shutter utilizes the so-called Kerr effect, which is a secondary electric effect of PLZT, and the amount of light transmitted through the polarizer (2) is expressed as Iax Io m''(j
・ΔV'λ) π. In this formula, 1. :
Light intensity of light source, t: thickness of PLZT substrate (3), λ: wavelength of transmitted light, Δ? &: Birefringence, that is, the difference no −me from the optical axis direction component ne of the refractive index.

However, when looking at the characteristic f:vI4 of pLZT, the birefringence Δn changes in a curved manner depending on the relationship between the PLZT temperature and the applied voltage (voltage), as shown in FIG.

In addition, this Figure 2 (Hatake) (a) shows PLZT with a different composition.
The characteristics of Therefore, in the conventional PLZT optical shutter, since a constant voltage is applied to the electrode (4), when a temperature change occurs in the PLZT substrate (3), the birefringence index also changes, and the above equation is expressed as follows: The amount of transmitted light displayed! This means that the amount of transmitted light cannot be maintained constant.

The present invention has been devised in view of these points, and an object of the present invention is to obtain an optical shutter that can maintain a constant amount of transmitted light.

The present invention uses a detection element to detect a temperature change in a substrate due to an electrostrictive substance that causes a change in birefringence, and performs variable control using a voltage controller on a voltage of the substrate to eliminate this change in birefringence. Therefore, the structure is such that the amount of transmitted light does not change.

An embodiment of the irises of the present invention will be described based on FIG. Components that are the same as those shown in FIG. 1 are designated by the same reference numerals, and description thereof will be omitted. First, a high-voltage power supply circuit (5) for voltage application and a switching circuit (6) for turning on and off the voltage application to the electrode (4) of this high-voltage power supply circuit (5) according to a control signal Sc are provided. . A part of the PLZT substrate (3), which is a substrate made of electrostrictive material, is covered with this PL.
A heat sensitive element (7) is attached as a detection element for detecting temperature changes of the ZT substrate (3). This heat sensitive element (7)
outputs a detection signal 5Dt- proportional to temperature, and this detection signal SD is input to the temperature correction circuit (8). This temperature correction circuit (8) takes into consideration the change characteristics of Δ9 as shown in FIG. This temperature correction circuit (8) is added to the high voltage power supply circuit (5) and the switching circuit (6) to form a voltage control device (9).

In such a configuration, the PLZT optical shutter transmits or transmits light depending on whether the switching circuit (6) is turned on or off.
It will be cut off. Here, suppose that the birefringence Δ5 and the applied voltage are set, for example, as shown by the dotted line in FIG. Then, this temperature rise is detected by the heat sensitive element (7), and based on this detection signal 8D, the temperature correction circuit (8) controls the high voltage power supply circuit (5) so as to increase the output voltage from the high voltage power supply circuit (5). Control. As a result, the electrode (4) K of the PLZT substrate (3)
The applied voltage also increases, and as is clear from the characteristics shown in FIG. 2, the birefringence Δn is maintained constant. PLZT
When the temperature of the substrate (3) decreases, the applied voltage also decreases due to the reverse operation, and the birefringence Δn is kept constant. Therefore, the amount of transmitted light from the polarizer (2) when the PLZT optical shutter is ON is kept constant regardless of the temperature change of the PLZT substrate (3). Therefore, the ratio of transmitted light amounts when the pLZT shutter is turned on and off is always maintained constant.

Next, a second embodiment of the present invention will be explained with reference to FIG. In this embodiment, a half mirror (2) that receives transmitted light from a polarizer (2) is arranged at an angle of 45 degrees with respect to the polarizer (2), and the transmitted light is transmitted through this half mirror αQ to a photodetector as a detection element. The light is received by the conversion element αη. In other words, this photoelectric conversion element α theory detects the change in the amount of transmitted light I, but the change in the amount of transmitted light I is detected when the PLZT substrate (
Since this is caused by the temperature change in 3), the temperature change is indirectly detected. Based on the detection signal S6 of the photoelectric conversion element α power, a light amount correction circuit (6) increases or decreases the output voltage from the high voltage power supply circuit (5) to keep the birefringence Δnt constant, similarly to the temperature correction circuit (8). ) are provided to constitute a voltage control device (to).

Even in such a configuration, the PLZT substrate (3) K
@When a layer change occurs, it is detected as a change in the amount of transmitted light I by the photoelectric conversion element (11), and the voltage controller QIK increases or decreases the voltage applied to the electrode (4) to keep the birefringence Δ constant. Therefore, the amount of transmitted light I is kept constant without being affected by temperature changes.

As shown in Fig. 5, an electrode α◆ for light intensity detection is additionally provided on the PLZT substrate (3), and an applied voltage tube is applied to this electrode α◆ by a switching circuit (6) only during detection correction. Then, the transmitted light amount X'f at that time may be detected by the photoelectric conversion element a.

In addition, in the present invention, the expression "optical shutter" is simply used, but in addition to the nine ordinary PI and ZT optical shutters shown in the embodiment, there is also a PI and ZT optical shutter as shown in FIG. This includes a 7'1-PLZT optical shutter array in which a plurality of electrodes CLi are arranged and voltage application to each electrode (to) is controlled by a switching circuit (6).In this PLZT optical shutter array, too,
As in the first embodiment (the heat sensitive element (
7), or as shown in Figure 6, one of the electrodes) is used as a light amount detection electrode (15 m), and the amount of transmitted light when voltage is applied is detected by the photoelectric conversion element α. Effects can be obtained.

As described above, the present invention provides a detection element that directly or indirectly detects the temperature change of the substrate caused by the electrostrictive material, and controls the voltage applied to the electrode on the substrate by a voltage control device based on the detection signal. Therefore, even if a temperature change occurs in the substrate, the birefringence can be maintained constant, and the amount of transmitted light can be kept constant at a constant #IA.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the PLZT optical shutter! Figure 2 (a) (
Figure 3 shows the Δn-E characteristic diagram of PLZT, Figure 3 is an explanatory diagram showing the first embodiment of the present invention, Figure 4 is an explanatory diagram showing the second embodiment of the invention, and Figure 5 is a modified example. FIG. 6 is an explanatory diagram showing the case of a PLZT optical shutter array. 1-2...Polarizer, 3...Substrate, 4...Electrode, 7
...thermal element (detection element), 9... voltage control device,
11... Photoelectric conversion element (detection element), 13... Voltage control device, 15... Electrode

Claims (1)

[Claims] 1. An optical shutter in which a substrate made of a nine-electrostrictive material on which an electrode for voltage application is formed is arranged between two polarizers,
A voltage control device includes a detection element that directly or indirectly detects a temperature change of the substrate, and controls a voltage applied to the electrode on the substrate based on a detection signal of the detection element so as to maintain a constant birefringence. A light shutter is provided. The optical shutter according to claim 1, characterized in that a heat-sensitive element is used as the detection element, and the temperature change thereof is directly detected by installing it on the substrate. 3. The optical shutter according to claim 1, wherein a charging conversion element for detecting the amount of transmitted light is used as the detection element, and a temperature change of the substrate is indirectly detected by the change in the amount of transmitted light.