JPH0410612B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an electro-optical shutter using translucent ceramic, particularly an optical shutter array, which has a plane of polarization parallel or perpendicular to the direction of the array, and which does not cause a decrease in switching speed or contrast. Regarding.

An optical shutter is well known in which a ferroelectric material exhibiting a second-order electro-optic effect, the so-called Kerr effect, is arranged between orthogonal polarizers, and light is turned on and off by applying a voltage.

PLZT ceramics is an example of a ferroelectric material used for this purpose.
Its composition is (Pb ₁ −x, Lax) (Zr ₁ −y, Tiy)
It is represented by the chemical formula of O ³ , and depending on the x and y values, the primary and secondary
Since it has the following electro-optic effect and optical memory function, its application to electro-optic fields such as optical shutters and displays is being studied.

Among them, those with x=0.086~0.1 and y=0.35 are
It exhibits paraelectricity at room temperature, but when a DC voltage is applied, a ferroelectric phase is induced and it begins to exhibit the Kerr effect. Moreover, since it has no memory function, it is suitable for application to optical shutters, and is called a slim lube secondary electrical material.

The basic structure of an optical shutter using PLZT is, as shown in Figure 1, in which a PLZT plate 3 is placed between polarizers 1 and 2 that are perpendicular to each other, and a voltage is applied parallel to the plate surface. An electrode 4 is provided. Then, the PLZT plate is arranged so that the direction of voltage application is 45° with respect to the polarization plane of the light incident on the PLZT plate.

If no voltage is applied, the light is blocked by the polarizer 2. If voltage is applied between electrodes 4 and 4', PLZT
The refractive index n _p of the plate 3 for ordinary light and the refractive index n _e for extraordinary light are Δn = n _p −n _e = 1/2n ³ RE ² , where n: refractive index of PLZT R: constant E: difference in applied electric field This produces an optical phase difference P=2π/λ·Δn, d where d: the effective thickness of the PLZT plate, and the emitted light generally becomes elliptically polarized light. Therefore, the amount of light passing through the polarizer 2 is I=Ii sin ² P/2 where Ii is the amount of light incident on the PLZT plate.

If a voltage Vλ/2 such that P=π is applied, the amount of light I passing through the polarizer 2 becomes maximum.

FIG. 2 shows an example of constructing an optical writing shutter array for an electrophotographic printer or the like using such an optical shutter. That is, a large number of signal electrodes 4a are provided on the PLZT plate 3 disposed between the orthogonal polarizing plates 1 and 2, facing the common electrode 4b, and among these electrodes 4a, the electrode to which a voltage is applied is Only the light shutter section allows light to pass through.

However, in this type of optical shutter array, if the distance between each light spot is set to 100 to 50 μm between the electrodes, which can be used for image recording, the switching speed decreases due to the capacitance generated between adjacent electrodes, and the switching speed decreases due to voltage leakage through the capacitance. The drawbacks were a decrease in contrast and the inability to use a polarized beam splitter PBS, which has high light utilization efficiency, as a polarizer. This is because the polarized light obtained with PBS is limited to planes of polarization that are parallel or perpendicular to the direction of the array.

The present invention attempts to obtain an optical shutter array that does not have the above-mentioned drawbacks by applying an electric field in a direction inclined at 45 degrees to the direction of the optical shutter array by devising the shape of the electrodes.

FIG. 3 shows an example of the electrode shape for this purpose,
The electrodes 4 are thin linear ones tilted at 45 degrees in the direction of the array, and are arranged at equal intervals, and when a voltage is applied to adjacent electrodes, the portion 5 between the electrodes exhibits birefringence, and the light is incident. Converts linearly polarized light into elliptically polarized light, and when the voltage is Vλ/2, it becomes linearly polarized light with the plane of polarization rotated by 90°.

With this electrode shape, it is necessary to apply an electric field between both sides of the light shutter section, so now terminals a and b
If a voltage V is applied between them, the shutter section 5 is turned on. At this time, to turn on the adjacent shutter section 5', apply a voltage of 2V to terminal c, or set the voltage to terminal b to 0, turn off shutter section 5, and apply voltage V to terminal c. There is a need. but,
When scanning such an optical shutter array,
No problem will occur as you can turn on the shutter in order.

FIG. 4 shows an example in which an optical shutter array is constructed using such a PLZT plate, and the polarization plane of incident linearly polarized light is perpendicular or parallel to the array.

FIG. 5 shows another example of an electrode shape having a similar effect, in which adjacent electrodes 4a have opposite slopes and are connected to the same terminal. In the case of electrodes with such a structure, by applying a voltage between the upper terminal rows b, d, f, h and the lower terminal rows a, c, e, g, all shutter sections of the array can be turned on simultaneously. It can be done.

FIG. 6 shows the pattern of the light-shielding mask, which has holes 6 corresponding to the light shutter portions 5. As shown in FIG. By covering the PLZT board with such a light shielding mask, leakage of light from parts other than the optical shutter section 5 can be reduced.

The optical shutter array of the present invention is as described above.
Due to the shape of the electrode on the ferroelectric material that exhibits the Kerr effect,
By applying an electric field in a direction 45 degrees from the direction of the optical shutter array, even if each shutter section is small and arranged closely, the distance between adjacent signal electrodes can be approximately the same as that of the shutter sections. Therefore, it is possible to reduce the reduction in switching speed and contrast due to the capacitance generated between the electrodes, and it is possible to arrange the shutter portions closely without spacing.

In addition, as a polarizer, for example, a polarized beam splitter PBS using a multilayer thin film can
Since the plane of polarization of the reflected light can only be parallel or perpendicular to the direction of the shutter array, it could not be used in conventional optical shutter arrays, but it became possible for the first time by using the ferroelectric material of the present invention. . Figure 7 shows the structure of an optical shutter array using PBS7 as a polarizer.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the principle of an optical shutter, Fig. 2 is a conceptual diagram of the structure of a conventional optical shutter array, Fig. 3 is an explanatory diagram of one embodiment of the electrode shape of an optical shutter array of the present invention, and Fig. 4 is also a diagram of the shutter array. Fig. 5 is an explanatory diagram of another embodiment of the electrode shape.
Figure 6 is a plan view of a light shielding mask, and Figure 7 is a conceptual diagram of the structure of a shutter array using PBS. 1, 2...Polarizer, 3...PLZT plate, 4...Electrode, 5...Light shutter section, 7...PBS element.

Claims (1)

[Claims] 1. In a ferroelectric material exhibiting a secondary electro-optic effect having electrodes arranged between mutually orthogonal polarizers and applying a signal voltage, the electrodes are arranged at an angle with respect to the optical shutter array direction, and the electrodes are arranged at an angle with respect to the array direction. 1. An optical shutter array characterized in that an electric field of 100% is applied to the shutter array.