JPH0369924A - Space light modulating element using liquid crystal - Google Patents

Abstract

PURPOSE:To provide the element which is high in response speed with a low voltage and has excellent characteristics by using a smectic liquid crystal exhibiting an electroclinic effect capable of making high-speed response for an electrooptical medium and impressing a control electric field for recording in tune to image input. CONSTITUTION:Transparent electrodes 104 are formed on a glass substrate 105 and an oriented film 102 is applied on the surface to form the substrate on one side. A photoconductor layer 107 and a dielectric mirror 106 are laminated on the transparent electrodes 104 of the opposite side substrate and an oriented film 102 is formed on the surface thereof. These two substrates are adhered via a spacer and the liquid crystal 101 is heated and sealed into the spacing. The transparent electrodes 104 are connected to a means 109 for impressing the electric field for recording. The electrooptical medium is formed so as to consist of the smectic liquid crystal which exhibits the electroclinic effect. The modulating element which is high in the response speed and has the excellent characteristics is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application 1] The present invention relates to an optical image storage device, and more particularly to a spatial light modulation element as a storage device that electrically controls an input two-dimensional image.

[Prior Art] Spatial light modulation elements have been developed as projection-type large screen displays. However, recently, its importance has been increasing in the field of optical information processing such as incoherent/coherent conversion. Particularly in the field of optical computing, it has become an indispensable device along with waveguide type elements.

Conventional spatial light modulators include deformable spatial light modulators that utilize geometric path differences using thermoplastic as a medium, electro-optic spatial light modulators that use electro-optic crystals such as PLZT, and electro-optic spatial light modulators that use electro-optic crystals as liquid crystals. It is classified as a liquid crystal spatial light modulator that has been replaced by a liquid crystal spatial light modulator.

In particular, devices using liquid crystals have the advantage that the optical properties of liquid crystals are the same as those of electro-optic crystals, and the operating voltage is extremely low, so many systems are being researched. (e.g. W, P., Bleha et al.: Opt.
.

Eng., 17 (197B) 317, F. J.
Kahn: Appl.

Phys, Lett, 22 (1973) 11
1, K. D. Hughes et al.: App.
L, Opt., 28 (1987) 1042, etc.)
[Problems to be Solved by the Invention] However, in each of the above methods, conventional spatial light modulation elements have problems such as the inability to electrically control the memory function of input images, extremely high operating voltage, and slow response speed. The present invention solves the above problems by using a smectic liquid crystal exhibiting an electroclinic effect capable of high-speed response as an electro-optic medium, and applying a recording control electric field in synchronization with image input. An object of the present invention is to provide a liquid crystal spatial light modulator having such characteristics.

[Means for Solving the Problems] In order to solve the above problems, the liquid crystal spatial light modulator of the present invention has the following main components: (1) An electro-optic medium, a photoconductor, and a power supply device for applying an electric field. The spatial light modulator is characterized in that the electro-optic medium is made of smectic liquid crystal exhibiting an electroclinic effect.

(2) The smectic liquid crystal is characterized in that it is composed of a group of compounds having an asymmetric carbon in its skeleton, or is a liquid crystal composition containing a compound having an asymmetric carbon.

(3) The power supply device for applying the electric field is characterized in that it supplies an alternating current electric field whose polarity changes at regular intervals.

[Example] (Example 1) FIG. 1 is a sectional view of a spatial light modulation element of the present invention. A transparent electrode 104 was formed on a glass substrate 105, and an alignment film 102 was applied to the surface to obtain a one-sided substrate. On the opposite substrate, a photoconductor layer 107 and a dielectric mirror 1 are disposed on a transparent electrode 104.
06 are laminated, and an alignment film 102 is formed on the surface thereof. The above-mentioned open substrate was adhered via a spacer 103, a liquid crystal 101- was heat-sealed in the gap, and a transparent electrode 104 was connected to a recording electric field applying means 109 to construct an element.

High resistance a-8i is used for the photoconductor 107, and plasma C
It was formed by the VD method. The dielectric mirror 106 is made of Si,
It is a multilayer film made of SiO2.

Further, the alignment film 102 was obtained by subjecting the surface of a polyimide thin film to a rubbing treatment. The rubbing direction is set to 1 on the opposite substrate so that the liquid crystal has a homogeneous uniaxial alignment.
It was set to 80@. Merck's ZLI- as a liquid crystal material
3774 was used, and the environmental temperature of the device was maintained at a temperature (70° C.) at which the liquid crystal exhibits a smectic A phase.

Next, an image recording and reading method for the above device will be described. FIG. 2 is a time chart showing the sequence. In FIG. 2, 201 represents the image input light, 202 represents the drive voltage waveform applied between the electrodes of the element, and 203 represents the optical output.The input image light is applied at timing 1+, and the photoconductor layer (first When 107) in the figure becomes conductive, a driving voltage waveform 202 is applied to the liquid crystal layer, and the liquid crystal responds with an electroclinic effect. The driving voltage waveform 202 changes its polarity at arbitrary timings 2 and t3, but by making the polarization axis direction of the readout light (111 in FIG. 1) coincide with the long axis direction of the liquid crystal molecules when no electric field is applied, the liquid crystal The arrangement state of the molecules becomes optically equivalent when a positive polarity pulse is applied and when a negative polarity pulse is applied.

As a result, during the 0 image holding period in which the recorded image is held as long as the input light is not interrupted, an alternating current waveform is applied to the liquid crystal, so that deterioration of the element can be prevented.

Next, the characteristics of the fabricated device will be described. An image projection of CRT image light was used as an image input means, a He-Ne laser beam passed through a polarizing beam splitter was used as readout light, and the light output after passing through an analyzer was observed. ±20V between electrodes
, when a 100Hz square wave was applied, a4onse
We were able to achieve an extremely fast rise speed of c. In addition, the tilt angle induced in the liquid crystal molecules is dependent on the applied voltage.The second @ is the liquid crystal spatial light modulator of the embodiment of the present invention, and the output light intensity can be varied by changing the applied voltage.
This can be easily adjusted by adjusting the position when recording and reading out images using the camera. FIG.

[Effects of the Invention] As described above, according to the present invention, a smectic liquid crystal exhibiting an electroclinic effect capable of high-speed response is used as an electro-optic medium, and a recording control electric field is applied in synchronization with image input, thereby producing a low voltage. We were able to obtain a liquid crystal spatial light modulator with extremely fast response speed and excellent characteristics. High reliability can be achieved because a symmetrical AC waveform is applied to the liquid crystal.

Furthermore, the device of the present invention has versatility and can be used in both reflective and transmissive types, regardless of the image input means. It can be widely applied to image display systems, optical calculation devices, etc.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a liquid crystal spatial light modulator according to an embodiment of the present invention. 1 2 3 4 5 6 7 9 0 1 2 Liquid crystal alignment film spacer Transparent electrode Glass substrate Dielectric mirror Photoconductor Recording Electric field applying means Input light Reading light Light output 01 02 03 , Input light, Drive voltage waveform, Light output Figure 1!2

Claims (3)

[Claims] (1) A spatial light modulator whose main components include an electro-optic medium, a photoconductor, and a power supply device for applying an electric field, characterized in that the electro-optic medium is made of a smectic liquid crystal exhibiting an electroclinic effect. A liquid crystal spatial light modulator. (2) The smectic liquid crystal is composed of a group of compounds having an asymmetric carbon in its skeleton, or is a liquid crystal composition containing a compound having an asymmetric carbon. liquid crystal spatial light modulator. (3) The liquid crystal spatial light modulator according to claim 1, wherein the power supply device for applying the electric field supplies an alternating current electric field whose polarity changes at regular intervals.