JPH03209432A - Space optical modulating element - Google Patents

Abstract

PURPOSE:To reduce the size of an optical system by using a polarization beam splitter as a substrate on the side where a photoconductive layer and a multilayered dielectric film mirror are not formed. CONSTITUTION:A transparent glass substrate is used on the writing side substrate 11a by light and the polarization beam splitter is used on the reading side substrate 11b as the substrates 11a, 11b for crimping liquid crystal molecules. Transparent electrode layers 12a, 12b consisting of ITO are provided on the surfaces of the two substrates. Further, oriented film layers 13a, 13b formed by diagonal vapor deposition of silicon monoxide are so provided that the incident directions of the substrates 11a, 11b on the writing side and reading side coincide in a combined state. The incident angle from the normal direction of the substrates of the oriented film layers 13a, 13b formed by the diagonal vapor deposition of the silicon monoxide may be selected within a 75 to 85 deg. range by taking characteristics into consideration. The optical system is miniaturized in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal spatial light modulator used in optical information processing, optical computing, machine vision, display terminals, and the like.

Summary of the Invention] The present invention relates to a liquid crystal spatial light modulator used in optical information processing, optical combining, machine vision, display terminals, etc. layer and a dielectric multilayer mirror,
As a film for orienting liquid crystal molecules on both substrates, silicon monoxide was obliquely deposited at an angle of 750 to 85 degrees with respect to the normal direction of the substrates, and these were controlled to have a constant gap so that they faced each other. By using a polarizing beam splitter as the substrate on the side on which the photoconductive layer and dielectric multilayer mirror are not formed, in a liquid crystal element using a ferroelectric liquid crystal composition as the liquid crystal composition sealed in the gap. , the optical system is miniaturized, thereby making it easier to apply it to systems such as optical information processing, optical computing, machine vision, and display terminals.

[Prior art] Conventionally, a spatial light modulator using ferroelectric liquid crystal has a polarizer and a half mirror or a cube beam splinter and an analyzer arranged outside the element, and readout light is irradiated through the polarizer and reflected. By reading out the light through an analyzer, a modulated image was obtained.

[Problems to be Solved by the Invention] However, in the conventional method, a polarizer and a half mirror or a cube beam splitter and an analyzer are arranged in the optical system, which requires a large space for the optical system and reduces the size of the system. The problem was that it was difficult to adapt.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides optical information processing,
A polarizing beam splitter was used as the substrate on the side on which the photoconductive layer and dielectric multilayer mirror are not formed in a ferroelectric liquid crystal spatial light modulator used in optical computing, machine vision, display terminals, etc.

[Effect]

An optical beam splitter is a pair of right-angled prisms pasted together, and the joined surfaces are coated with a dielectric multilayer film. can be split into two linearly polarized lights whose polarization planes are orthogonal to each other. The branching angle is 90@, and the two exit beams are each emitted at 0° to the outer surface, eliminating the need for an external polarizer, half mirror, or cube beam splitter analyzer, making the optical system more compact. can be converted into

[Example] The contents of the present invention will be explained in detail below using the drawings.

FIG. 1 is a conceptual diagram of a liquid crystal spatial light modulator according to the present invention. As the substrates 11a and 11b for sandwiching liquid crystal molecules, a transparent glass substrate is used for the optical writing side substrate 11a, and a polarizing beam splitter is used for the reading side substrate 11b.
was used. ■TOi! on the surface of both boards! Bright electrode layer 12a
, 12b were provided. Here, ITO electrodes 12a, 12b
There is no problem with tin antimony oxide, etc. The polarizing beam beam mirror is made by pasting the slopes of a pair of right-angle prisms together, and the pasted surfaces are coated with a dielectric multilayer film. The light can be split into two linearly polarized lights whose polarization planes are orthogonal to each other. The branch angle is 90″;
The two emitted lights are each emitted at 06 onto the outer surface. In this example, a He-Ne laser was used for the readout light, and 03PBSO37 (25.4+nm square) manufactured by Melles Griot was used as the substrate 11b using a polarizing beam splitter. The surface of both substrates has a distance of 85 mm from the normal direction of the substrates.
The angle of incidence is 22.5° from the plane of polarization of the incident light from the polarized beam splinter side, so that the directions of incidence on the substrates on the writing side and reading side match in the combined state. Alignment film layers 13a and 13b formed by obliquely vapor-depositing silicon monoxide were provided.

- The angle of incidence of the alignment film layers 13a and 13b on which silicon oxide is obliquely deposited from the normal direction of the substrate may be selected in the range of 75'' to 85'' in consideration of the characteristics. On the transparent electrode layer 12a on the writing side by light, an amorphous silicon photoconductive layer 15 was formed by discharging and decomposing a gas mainly composed of SiF to form an a-5i rH layer having a thickness of 2 μm. Here, the amorphous silicon photoconductive layer 15 may have a film composition to which P, N, etc. are added during discharge decomposition, or may be a semiconductor film of other composition such as n-type or p-type on the a-3i:8 layer. There is no problem even if the structure is a stacked structure.

Furthermore, a light shielding layer 16 was provided on the film to prevent projection light from entering the photoconductive layer 15, and a dielectric mirror 17 in which a total of 15 layers of SiO□ and St were alternately laminated was formed. Furthermore, the substrates 11a and llb have their alignment film layers 13a.
, 13b were placed opposite each other, and a gap was controlled and formed via a spacer 19 made of an adhesive to which glass fibers having a diameter of 1.0 μm were added, so that the ferroelectric liquid crystal layer 14 was sandwiched therebetween.

The gap was approximately 1.0 μm. 5CE-6 (manufactured by BDH) was used as the encapsulated ferroelectric liquid crystal composition.

The above-described ferroelectric liquid crystal spatial light modulator is brought into a stable state in which the ferroelectric liquid crystal molecules are uniaxially aligned when viewed from the substrate surface by applying a direct current electric field between the transparent electrodes of both substrates from the outside. Furthermore, by reversing the polarity of the applied electric field, a stable state is achieved in which the other ferroelectric liquid crystal molecules are uniaxially aligned when viewed from the substrate surface. This reversal between the two states due to the electric field has nonlinearity and a clear threshold with respect to the electric field applied to the ferroelectric liquid crystal layer. The applied electric field may be one in which alternating current is superimposed on direct current.

The angle between the two stable states corresponds to the cone angle of the ferroelectric liquid crystal, and in this example, the optical axes are each at an angle of 22.5"(45" between optical axes) from the oblique deposition direction of silicon monoxide. existed. The angle of the oblique deposition direction with respect to the polarization plane of the incident light may be set according to the cone angle of the ferroelectric liquid crystal used. The light incident from the polarization beam splinter is S-polarized light, and the plane of polarization and the oblique deposition direction of silicon monoxide are set at 22.5', so the plane of polarization is aligned with the optical axis of the ferroelectric liquid crystal molecules in one stable state. In this case, the incident light is reflected by the ferroelectric liquid crystal layer without being modulated. When observing from the readout direction (perpendicular to the element on the side using the polarizing beam splitter), only p-polarized light is transmitted through the polarizing beam splitter, so in this case no light is transmitted and the state is dark. becomes. In the other stable state when the direction of the applied electric field is reversed, the polarization plane of the incident light and the optical axis of the ferroelectric liquid crystal molecules form an angle of 45@, so the incident light undergoes birefringence within the ferroelectric liquid crystal layer. , a p-polarized light component is generated, and a bright state is achieved.

According to the ferroelectric liquid crystal spatial light modulator as described above, due to the bistability of the ferroelectric liquid crystal element, after erasing by applying an erasing electric field, the voltage divided across the liquid crystal layer in the opposite direction to the erasing electric field is While applying an electric field that is below the threshold value when the photoconductive layer is dark and above the threshold value when the photoconductive layer is dark, an optical image is irradiated with writing light 20 from the outside of the cell, or a polygon mirror or galvano mirror is used while modulating a semiconductor laser. By performing scanning, the liquid crystal molecules are inverted only in the area irradiated with light, and this is maintained stably, so that images can be written and formed on the ferroelectric liquid crystal layer 14. Ta. Further, the image formed by writing can be read out by irradiation with the projection light 21.

The applied voltage may be a direct current with an alternating current waveform superimposed thereon. Furthermore, while applying an electric field in the opposite direction to the electric field direction during writing, such that the voltage divided across the liquid crystal layer is below the dark value when the photoconductive layer is dark and above the dark value when the photoconductive layer is dark, By scanning using a polygon mirror or galvano mirror while modulating the laser, the liquid crystal molecules are inverted only in the areas of the ferroelectric liquid crystal layer that are irradiated with the laser light, and are stably maintained. Therefore, it was also possible to erase parts of the image.

Figure 2 shows a readout optical system when using a conventional ferroelectric liquid crystal spatial light modulator, and Figure 3 shows a readout optical system when a ferroelectric spatial light modulator according to the present invention is used. show.

In FIG. 2, after the readout light 21 passes through the analyzer 22,
It is reflected by the half mirror 23 (or beam splinter), enters the ferroelectric liquid crystal element 24, is modulated by the element, is reflected, passes through the half mirror 23 and the analyzer 25, and is read out as an image. In FIG. 3, by using the ferroelectric liquid crystal spatial light modulator 26 according to the present invention,
It can be seen that since a polarizing beam splitter is used as the reading side substrate, there is no need to arrange an external polarizer, half mirror, or cube beam splitter 1 analyzer, and the optical system can be miniaturized.

[Effects of the Invention] As described above, the ferroelectric liquid crystal spatial light modulator according to the present invention can be used as a ferroelectric liquid crystal spatial light modulator used in optical information processing, optical computing, machine vision, display terminals, etc. By using a polarizing beam splitter as the substrate on which the photoconductive layer and dielectric multilayer mirror are not formed, the optical system can be miniaturized, making it suitable for optical information processing, optical computing, machine viewing, display terminals, etc. can be easily applied to the system.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the structure of a ferroelectric liquid crystal spatial light modulator according to the present invention, and FIG. 2 is an example of a readout optical system using a conventional ferroelectric liquid crystal spatial light modulator. FIG. 3 is a schematic diagram showing an example of a readout optical system using the ferroelectric liquid crystal spatial light modulator according to the present invention. 11a... Transparent substrate 11b... Polarizing beam splitter 12a, 12b... Transparent electrodes 13a, 13b... Alignment film 14... Ferroelectric liquid crystal layer 15... Photoconductive film 16... Light shielding film 17...Dielectric mirror 19...Spacer 20...Writing light 21...Reading light 22...Polarizer 23...Half mirror 24...Conventional ferroelectric liquid crystal spatial light Modulation element 25...
・Analyzer 26...ferroelectric liquid crystal spatial light modulation element according to the present invention

Claims (1)

[Claims] (1) A photoconductive layer and a dielectric multilayer film mirror are provided on one electrode between a pair of substrates having electrodes, and the film serves as a film for orienting liquid crystal molecules on both substrates.
Silicon monoxide is obliquely deposited at an angle in the range of 5° to 85°, and these are controlled to have a certain gap and are faced to each other.
A liquid crystal element using a ferroelectric liquid crystal composition as a liquid crystal composition sealed in a gap, characterized in that a polarizing beam splitter is used as a substrate on the side on which a photoconductive layer and a dielectric multilayer mirror are not formed. Spatial light modulator.