JPH0421829A - Spatial light modulator and neural network device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to optical processing devices, spatial light modulation devices used in projection displays, and input/output operations similar to those in the nervous system, such as pattern recognition, associative memory, and parallel processing. It relates to a neural network device that performs processing and the like.

A conventional spatial light modulation device is a device that modulates incident light using two-dimensional information recorded in a spatial light modulation element, such as transmittance, reflectance, phase, polarization angle, etc. of the incident light.

Spatial light modulators that use optical crystals that utilize the Pockels effect, liquid crystals that utilize anisotropy of refractive index, and the like are often used.

In particular, the latter is attracting a lot of attention because it is easy to increase the area and is low cost.

Most of the spatial light modulation elements using liquid crystals are electro-optical spatial modulation elements that can easily modulate input light using electrical signals, and are liquid crystal cells used in liquid crystal televisions and the like that are equipped with drive circuits.

In addition, two-dimensional information is used as a modulation signal by light.
A spatial light modulator in which a photoconductive layer such as Bi+25io2p is laminated on a liquid crystal layer has been proposed as a light-light spatial modulator that also has a threshold processing function (Kuniharu Takizawa et al., 35th issue). Preliminary Lectures for the Association of Applied Physics Lectures, Spring 1986 30p-ZF-3, 30p
-ZF-4).

In many neurocomputers, a neural network circuit that imitates neural functions is realized in hardware using light.The function of simultaneously thresholding inhibitory and excitatory signals is implemented in hardware using optical wave technology. Instead, most of them separate these signals and rely on electrical signal processing, including computers, for excitatory and inhibitory functions. Collection, Autumn 1989, 30p-ZD-4).

Problems to be Solved by the Invention As described above, the conventional device has a problem in that it is not a spatial modulation device that can perform optical calculations simultaneously on the same optical path 1- and output the results as light.

Another problem is that the neural network circuit does not have a processing function that can simultaneously threshold inhibitory and excitatory signals using light bar 1ζware technology.

The present invention aims to solve such conventional problems.

Means for solving the problem consists of at least a polarizer, an analyzer, and a spatial light modulation element provided between them that modulates the polarization angle of input light using two-dimensional information, and uses the modulated transmitted or reflected light as output light. In the spatial light modulation device to be extracted, at least two spatial light modulation elements are arranged in which the polarization angle of a polarizer and an analyzer are approximately 45 degrees, and the spatial light modulation elements rotate the polarization angle of incident light in directions different from each other by approximately 45 degrees. is placed on the optical path, and an excitatory signal is sent to the spatial light modulator that rotates the polarization angle of the incident light in the direction that the polarization angle of the incident light matches the polarization angle of the analyzer, and vice versa. By applying a suppressive signal to the spatial light modulation element, the product-sum result is output as transmitted light or reflected light.

Effects of the present invention, for example, in these spatial light modulators, T N
When a liquid crystal material is used, a spatial light modulator that has a positive signal as a modulation signal when no voltage is applied rotates the polarization angle of the incident light by approximately 45 degrees, and although it is perpendicular to the analyzer, the following negative signal On the other hand, in the case of a spatial light modulator having a modulation signal of , the spatial light modulator is rotated by approximately 45 degrees, so that the incident light passes through as it is and enters the analyzer at approximately 4.5', so that about half of the light is transmitted.

Let us denote the signals applied to both as (positive, negative) and indicate them as 1 and 0. Now, when the signal is (0, 1), the incident light is rotated in the direction that matches the polarization angle of the analyzer. A voltage is applied to the spatial light modulator that was previously in use, and since the liquid crystal molecules stand in the direction of the voltage, the rotation angle of the polarization angle becomes O. This leaves only the direction in which the polarization angle is perpendicular to the analyzer, and the light transmitted through these spatial light modulators becomes O because it is perpendicular to the analyzer. vice versa,(
1,0), light matching the polarization angle of the analyzer is obtained from the spatial light modulator, so that the transmitted light is 1.

Also, in the case of (1, 1), since l-1=0, 1/2 of the transmitted light is obtained because it is not modulated by the spatial light modulator.

In this way, threshold processing that takes into account the subtraction function becomes possible.

Embodiments An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a front view showing an embodiment of the spatial light modulation device of the present invention.

The polarizer 11 and the analyzer 15 each use a polarizing plate. As the spatial light modulation elements 12 and 13, electro-optic elements are used. A drive circuit 14 that supplies a modulation signal is connected to the spatial light modulation elements 12 and 13.

The electro-optical element used for the spatial light modulator 12.13 includes:
A liquid crystal or an optical crystal using the Pockels effect is used. TN liquid crystal, STN liquid crystal, or ferroelectric liquid crystal is used as the liquid crystal material, and LiNb is used as the optical crystal material.
O3 type crystal material, zinc blende type crystal, KDP type crystal, Bi
t23i020 etc. are listed. These need to be divided into pixels in order to electrically record two-dimensional information. For this purpose, there is a method in which transparent electrodes processed in a stripe shape are crossed and driven at an XY address, or a T
By adopting an element configuration that includes a built-in FT, it is possible to drive with higher precision.

The incident light is linearly polarized by the polarizer 11 and enters the spatial light modulator 12 . The analyzer 15 is arranged at approximately 45° clockwise ζ. Either of the spatial light modulators 12, 13 rotates the polarization angle approximately 45 degrees clockwise or counterclockwise. When the modulation signal is both O, rotate it, and when the rotation is 0 when the modulation signal is 1, rotate clockwise by 45
The spatial light modulator that is being rotated has a negative signal and the other one has a positive signal. Conversely, if both modulation signals have a rotation angle of 0 at 00 o'clock and are rotated approximately 45 degrees at 10 o'clock, the spatial light modulation element rotated clockwise will have a positive signal, and the other will have a negative signal. Uke has.

Further, processing may be performed by dividing 45° by a plurality of spatial light modulation elements.

FIG. 2 shows an example of a spatial light modulation element using a liquid crystal material for recording two-dimensional information by guiding light.

This is an example in which a photoconductive material 23 is directly laminated between an electrode 21 and an electro-optical element 22. 20.25 is a glass substrate, and 24 is an electrode. In this case, the electro-optical element has a certain threshold (
A liquid crystal material having a 1α voltage is suitable. When no light is irradiated, it is necessary to design the resistivity and capacitance of the photoconductive material so that the voltage applied to the electrodes 21.24 is below a threshold voltage applied to the liquid crystal material.

[Example 1] As an example of the spatial light modulation element shown in FIG.
TO was used in an X-Y address sandwich cell configuration, and TN liquid crystal was used as the liquid crystal material.

An alternating current voltage of 10011z and 6v was applied as an l signal to each liquid crystal serving as a spatial light modulator. The 0 signal is the applied voltage OV.

A negative signal was applied to the spatial light modulator that rotates the incident polarization angle clockwise by approximately 45 degrees when no voltage was applied, and a positive signal was applied to the other, and the output light was observed using a phototransistor.

FIG. 3 shows the AC signal applied to each spatial light modulation element and the intensity of output light. In the figure, (positive signal, negative signal) are each shown as 1.0.

It is confirmed that each sum signal is obtained centered on 1/2.

[Example 2] As an example in FIG. 2, an example is shown in which an electro-optical element, an i'N liquid crystal, and a spatial light modulation element using amorphous silicon as a photoconductive material are used.

As shown in FIG. 4, half mirrors 45 and 46 are arranged between a polarizer 41, an analyzer 44, and a spatial light modulator 42, 430. Record dimensional information using light.

An alternating current voltage of 10OIIz of 5cm is applied between the transparent electrodes.

Blue light of 500 nm or less was used as the modulation signal, red light of 650 nm or more was used as the incident light, and the transmitted pattern image was observed with a CCD camera.

FIG. 5 shows a positive signal pattern 51(a), a negative signal pattern 52(b), and an output signal pattern 53(c) which is a sum signal. It can be seen that signal processing is also possible with optical signals.

Such signal processing corresponds to discrete input values of a sigmoid function 54 (d'), which is a threshold processing circuit in a neural circuit.

[Example 3] Using a spatial light modulation device as shown in Figure 4 of ``2'',
We created a neural network circuit using the orthogonal learning method as shown in the figure, and attempted to recognize six English capital letters: A, b, C, d, 01, and ■. The coupling coefficient pattern to be recorded on the spatial modulation element is obtained by quantizing the excitatory coupling and inhibitory coupling coefficients into binary values of 1.0 using a simulation method using a computer, and then displaying the pattern on a blue light liquid crystal display device using a half-mirror. - to irradiate each photoconductive material built in the two spatial light modulators.

Human covert turns are displayed in a 5×6 matrix, patterns of excitatory and inhibitory coupling constants are displayed in a 25×36 matrix, and output patterns are displayed in the same pattern as human power. 6
1 is a human cover turn, 62.65 is a microlens array, 63.64 is a spatial light modulation element, and 66 is an optical threshold element that performs threshold processing with a built-in photoelectric conversion element, 1.0
indicate. 67 is a polarizer, 68 is an analyzer, 69.70 is a half mirror, and the coupling coefficient pattern is transferred to the spatial light modulator 63.
．． 64 photoconductive material-L.

It has been confirmed that by using such discrete values, actual character recognition can be performed in the same way as the calculated results. Furthermore, using such a spatial light modulation element, a 100% response rate was obtained for learning pattern ζ vs.-C.

”2, without the use of electrical auxiliary means,
It was confirmed that excitatory and inhibitory signals can be processed using optical signals alone.

In this way, a neural network is formed using the spatial light modulation device of the present invention, and the coupling coefficient with a discrete value (1α) obtained by a computer is displayed optically and irradiated onto a spatial light modulation element containing a photoconductive material. , both are 1 for the character patterns after learning.
A response rate of 0.00% was obtained.

Effects of the Invention According to the present invention, sum of products with negative values (addition of multiple values)
It is possible to provide a spatial light modulation device in which this is easily possible using an optical signal.

Further, since the spatial light modulation device according to the present invention is capable of adding up positive and negative values in real time, it is possible to provide a neural network that can support various learning methods as necessary.

In addition, a neural network using these spatial light modulation elements does not require an auxiliary device for subtracting positive and negative values, so it is possible to construct a neural network that is inexpensive, compact, and high-speed.

[Brief explanation of drawings]

FIG. 1 is a front view of one embodiment of the spatial light modulation device of the present invention and a diagram showing an example of the polarization angle of each element, and FIG. 2 is a diagram showing calculations using the light of the embodiment of the spatial light modulation device of the present invention. 3 is a graph showing the calculation results using the spatial light modulation device shown in FIG. 1, and FIG. 4 is a front view of the spatial light modulation device shown in FIG. Front view shown, 5th
The figure shows an example of the arithmetic processing results using the spatial light arithmetic circuit shown in Fig. 4 and a configuration diagram showing the sigmoid function of the threshold processing function used in the neural network. 1 is a front view showing a configuration diagram of a character recognition device using a neural network; FIG. 11...Polarizer, 14...Analyzer, 12.13...
・Spatial light modulation element, 15...drive circuit, 21.24・
... Electrode, 20.25 ... Glass substrate, 23 ... Photoconductive material, 22 ... Electro-optical element, 41 ... Polarizer, 44 ... Analyzer, 42.43 ... Space Light modulation element, 45.46... Half mirror 51... Excitatory signal pattern, 52... Inhibitory signal pattern, 53...
Output pattern, 54...Sigmoid function, 61...
Input cover turn, 62.65... Microlens array, 63.64... Spatial light modulator, 67... Polarizer, 68... Analyzer, 69.7o... Half mirror 6
6...Photoelectric conversion element threshold processing display device.

Claims (3)

[Claims] (1) Spatial light modulation that includes at least a polarizer, an analyzer, and a spatial light modulation element installed between them that modulates the polarization angle of input light using two-dimensional information, and extracts the modulated transmitted or reflected light as output light. In the apparatus, the polarizer;
At least two spatial light modulation elements are provided on the optical path, the polarization angle of the analyzer being arranged at substantially 45°, and the spatial light modulation element rotating the polarization angle of the incident light by substantially 45° in different directions; A positive signal is sent to the spatial light modulator that rotates the incident light that has passed through the spatial light modulator in a direction in which the polarization angle matches the polarization angle of the analyzer, and conversely, the spatial light is rotated in a direction perpendicular to the analyzer. A spatial light modulation device characterized in that a product-sum result including a subtraction function is output by applying a negative signal to a modulation element. (2) Two spatial light modulators constituting the spatial light modulator control polarization angles using electrical signals, and the electrical signals are applied to the spatial light modulators via a photoconductive layer. The spatial light modulation device according to claim 1. (3) In a neural network device having a spatial light modulator that optically outputs an excitatory signal based on a threshold value of the sum of products of an excitatory signal and an inhibitory signal, the spatial light modulator includes at least a polarizer, an analyzer, and the like. , a spatial light modulation element provided between them that modulates the polarization angle of input light using two-dimensional information, and the polarization angle of the polarizer and analyzer is arranged at substantially 45 degrees, and the spatial light modulation element At least two spatial light modulators that rotate the polarization angle of light by 45 degrees in substantially different directions are provided on the optical path, and the polarization angle of the incident light transmitted through the spatial light modulator is the polarization angle of the analyzer. By applying an excitatory signal to a spatial light modulation element rotated in the same direction and an inhibitory signal to a spatial light modulation element rotated in a direction perpendicular to the analyzer, the product-sum result is applied to transmitted light or A neural network device equipped with a spatial light modulator that outputs reflected light.