JPH02143994A - Light associative memory device - Google Patents

Abstract

PURPOSE:To perform the write of information in a short period of time and to dispense with the use of coherent light in the readout of storage information by using a liquid crystal cell driven by an active matrix type active element as a spatial light modulation element. CONSTITUTION:An active matrix type liquid crystal cell in which two amorphous silicon thin film transistor arrays are used as the active element and nematic liquid crystal twisted by 90 deg. is used as liquid crystal and its driving circuit are used in the storage of storage matrix and an input pattern, and a phototransistor array in the detection of an associated result, and an electrical analog processing circuit in the computation of a partial sum and a threshold value, and a computer 9 in control for entire system, the simulation of the storage matrix, and a feedback operation at the time of performing learning. In such a way, it is possible to perform the write of the information in a short period of time, and to dispense with the use of the coherent light in the readout of the storage information.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a self-remembering optical content addressable memory device.

Background of the Invention In recent years, with advances in neurophysiology, the human brain and nervous system have been regarded as a type of information processing system, and the brain's speech recognition,
There is increasing research into implementing neural network devices such as neurocomputers and associative memories that imitate superior parallel processing functions such as pattern recognition and learning.

Among these, an optical associative memory device that utilizes the parallelism of light as a means to realize associative memory has been proposed.

As a conventional example, here we will discuss the Optical Associatron (1988 (Showa 63) Spring 3
Proceedings of the 5th Applied Physics Association Lectures Volume 3
p732 30a-ZF-5 to 7) will be explained.

FIG. 3 is a block diagram of the optical content addressable memory device system in this conventional example. The basic configuration of this optical associatron is that two spatial light modulation tubes 27 (hereinafter abbreviated as MSLM) are used to store a memory matrix and an input pattern.
2 for writing the memory matrix M and writing the input pattern
A set of light emitting diode arrays 25 (hereinafter abbreviated as LED arrays), a phototransistor array 32 (hereinafter abbreviated as PTR arrays) for detection of recall results,
An electric analog processing circuit 33 is used for partial sum and threshold calculations, and is used for controlling the entire system, simulating storage matrices,
The configuration is such that a computer 35 is used for feedback calculations during learning.

Next, regarding the operating principle, first, the matrix-like 4X4 (
The storage information of ~18 points) is spatially multiplexed and written to the storage MSLM 27 using the 16×16 (~64 points) LED array 25 arranged in a matrix, and the storage information is stored in the storage matrix M.
form. Next, the matrix-like 4X4 (=IEt points) input pattern is also multiplexed so that it spatially corresponds to the memory matrix M, and the IE3X16 (~
256 points) is written into the MSLM 27 using the LED array 25 to form the input cover pattern X. After that, He-N
The e-laser 30 is connected to the MSLM 27 via the half mirror 28.
When the light is irradiated onto the photocathode side of the MSLM 27, it is reflected by the electro-optic crystal surface of the MSLM 27, and this reflected light is given a phase change corresponding to the written memory matrix M. The memory matrix M is read out by passing this reflected light through an analyzer 31 such as a polarizing plate. When this read memory matrix M is irradiated onto the photocathode side of the MSLM 27 through a half mirror, it is reflected by the electro-optic crystal surface of the MSLM 27.
This reflected light is given a phase change corresponding to the incident cover pattern X. By passing this reflected light through an analyzer 31 such as a polarizing plate, the product of the storage matrix M and the input cover pattern X, that is, the Hadamard product, is formed. This result is detected by the PTR array 32, and the recall φ(MX
).

In the learning process, the computer 35 calculates a correction term corresponding to the difference between the recall output and the input pattern, and the LED array 2
This is realized by an orthogonal learning method in which data is added to the storage MSLM 27 using 5. That is, the storage matrix to be modified is n
The memory matrix after learning times is M. , if the learning gain is α, then M n + H = M n + α (X - φ (Mn x )
) x' is given by the formula. The learning gain α is M
It can be set arbitrarily by changing the writing time of the correction pattern to the SLM 27. Then, learning may be terminated when all the recalled patterns match the input patterns.

Problems to be Solved by the Invention However, in the above configuration, since the MSLM 27 is used as the spatial light modulation element, the stored information is converted into electrical information and then converted into light using the LED array 25. There are problems such as the need for a complicated system configuration for writing to the MSLM 27, the need to take time to write to the MSLM 27, and the need to use coherent light to read stored information.

In view of the above, an object of the present invention is to provide an optical associative memory device that has a simple system configuration, can write information in a short time, and does not require the use of coherent light to read stored information.

Means for Solving the Problem A liquid crystal cell driven by an active matrix type active element is used as a spatial light modulation element.

Effects According to the above configuration, it is possible to provide an optical associative memory device with a simple system configuration, in which information can be written in a short time, and in which coherent light does not need to be used to read stored information.

Embodiment FIG. 1 is a block diagram of an optical content addressable memory device according to an embodiment of the present invention.

The basic configuration of this optical associative memory device is an active matrix type liquid crystal cell (hereinafter referred to as "active matrix liquid crystal cell") using two amorphous silicon thin film transistor arrays as active elements and a 90° twisted nematic liquid crystal as the liquid crystal for storing memory matrices and input patterns. , AM-LC cell) and its driving circuit, a phototransistor array (hereinafter abbreviated as PTR array) is used to detect recall results, and an electrical analog processing circuit is used for partial sum and threshold calculations. A computer is used for controlling the entire system, simulating the memory matrix, and performing feedback calculations during learning.

In FIG. 1, 1 is a white light source and 2 is a lens system.

Reference numeral 3 designates a liquid crystal cell for input cover pattern, and 4 designates a liquid crystal cell for storage, which are arranged so that the light emitted from the white light source 1 and converted into pseudo-parallel light by the lens system 2 passes through them. 5 is a PTR array, which detects the light passing through the liquid crystal cell. 6 is a threshold processing element, 7 is an image digitizer,
8 is a monitor display, and 9 is a computer.

The AM-LC cell used here will be explained in detail using the schematic cross-sectional view shown in FIG. 2. This AM-LC cell has thin film transistors (hereinafter abbreviated as a-8i TFT) using amorphous silicon as a semiconductor as active elements formed in a matrix on one glass substrate 10. First, a gate electrode 1 is placed on a glass substrate 10.
1 is formed of Cr, for example, and then a gate insulating layer 12, a
-8i semiconductor layer 13 and semiconductor protective layer 14 by plasma Cv
Form fist buttering using method D. After interposing the n4-a-8i layer 15 to improve ohmic properties,
The source electrode 16 and drain electrode 17 are formed all at once using, for example, A1, and finally, the transparent electrode 18 is formed from, for example, ITO to complete the a-8i TFT. After that, the alignment film 2
Apply 1 and perform rubbing treatment. The other glass substrate 19 has a counter electrode 2O and a black matrix 2 for light shielding.
4, the alignment film 21 is similarly applied and rubbed, but this rubbing is carried out in a direction shifted by about 90' from the previous substrate. Then, a twisted nematic liquid crystal 22 may be sealed between both substrates, and polarizing plates 23 may be placed in front and behind the substrates. In this AM-LC, a storage capacitor can be added to improve the performance, and the source/drain electrodes and the transparent electrode can be formed of the same thin film.

Next, the operating principle will be explained. First, a matrix of 1eX1B (=25EI points) of storage information is spatially multiplexed and written into the storage liquid crystal cell 4 by a drive circuit.
Form a storage matrix M. Next, the matrix-like IE3X
The input pattern of IE3 (=256 points) is also multiplexed so as to spatially correspond to the memory matrix M, resulting in 256×25B (=E
3553e) is written in the liquid crystal cell 3 for input cover turn by the drive circuit, and input cover turn X is formed.

Thereafter, the light from the normal white light source 1 is made into pseudo-parallel light by the lens system 2, and is transmitted through the storage liquid crystal cell 4 in which storage information is written, thereby reading out the storage matrix M.

The read memory matrix M is directly transmitted through the input cover pattern liquid crystal cell 3 in which the input cover pattern X is written, thereby forming the product of the memory matrix M and the input cover pattern X, that is, the Hadamard product. This result is detected by the PTR array 5, and the sum of the corresponding portions and the threshold calculation φ processing are electrically performed by the threshold processing element 6, thereby realizing the recall φ(Mx).

Further, in the learning process, a correction term corresponding to the difference between the recall output and the input pattern is calculated by the computer 9, and is written in the storage liquid crystal cell 4 using the drive circuit, which is realized by an orthogonal learning method. In other words, the memory matrix to be corrected is M n + 1 '' M n + α (X - φ (Mnx)
)

Furthermore, in order to improve the recognition rate, if the contrast of the liquid crystal cell is approximately 10 or more, a recognition rate of 80% or more can be obtained. Furthermore, in order to improve storage capacity and recognition rate, it is desirable that the gradation of the liquid crystal cell be as large as possible, but it is generally acceptable for the system to have a gradation of 8 or more in practice. The contrast of the liquid crystal cell used in the above example was 3
0, and the gradation was 16.

The liquid crystal cell may be a super twisted nematic liquid crystal (STN-
LC) can also be used. Furthermore, SBE (Super-twlst) with a twist angle of about 270°
It is also possible to use a liquid crystal material in the Blrefringent Effect) mode.

It is also possible to use two ferroelectric liquid crystal cells using chiral smectic C liquid crystal as the liquid crystal cell.

Effects of the Invention According to the present invention, it is possible to provide an optical associative memory device that has a simple system configuration, can write information in a short time, and does not require the use of coherent light to read out stored information. The practical effects are significant.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of an optical associative memory device according to the present invention, FIG. 2 is a schematic cross-sectional view of an AM-LC cell using an a-8i TFT in an embodiment of the present invention, and FIG. is a block diagram of a conventional optical content addressable memory device. 1... White light source, 2... Lens system, 3...
Liquid crystal cell for input cover turn, 4...liquid crystal cell for memory,
5... Light receiving element, 6... Threshold processing element, 7...
...Image digitizer, 8...Monitor display, 9...Computer, 10...Glass substrate, 11...Gate electrode, 12...Gate insulating layer, 13...・a-8i semiconductor layer, 14... semiconductor protective layer, 15... n'-a-8i layer, 16.
...source electrode, 17...drain electrode, 1
8...Transparent electrode, 19...Glass substrate, 20...
... counter electrode, 21 ... alignment film, 22 ... liquid crystal layer, 23 ... polarizing plate, 24 ... black matrix. Agent's name: Patent attorney Shigetaka Awano; 1 person; Figure 31: 5 person cutout 9-li leather goods cell\ 8Mo = 9 tape orange Figure

Claims (6)

[Claims] (1) A photo-associative memory comprising a spatial light modulation element, a light emitting element, a light receiving element, and a threshold calculation element, characterized in that the spatial light modulation element is composed of a liquid crystal cell driven by an active matrix type active element. Optical associative memory device. (2) In a photo-associative memory device comprising a spatial light modulation element, a light emitting element, a light receiving element, and a threshold processing element, the spatial light modulation element is composed of a liquid crystal cell using super twisted nematic liquid crystal with a twist angle of 90° or more. An optical associative memory device characterized by: (3) A photo-associative memory device comprising a spatial light modulation element, a light emitting element, a light receiving element and a threshold processing element, wherein the spatial light modulation element is comprised of a liquid crystal cell using ferroelectric liquid crystal. Device. (4) The photo-associative memory device according to claim 1, wherein the active matrix type active element is a thin film transistor. (5) The photo-associative memory device according to any one of claims 1 to 3, wherein the liquid crystal cell has a contrast of approximately 10 or more. (6) The photo-associative memory device according to any one of claims 1 to 3, wherein the liquid crystal cell has approximately 8 or more gradations.