JPH0618953A - Optical neural computer and optical parts using the same - Google Patents

Abstract

PURPOSE:To integrate and miniaturize a device in an optical neural computer of such a type that each emitted light from a light emitting element array is modulated by a matrix spatial optical modulation element and emitted light output from the spatial optical modulation element is detected by a light receiving element so as to perform threshold processing. CONSTITUTION:A 1st transparent substrate 12 which is arranged between the light emitting element array 11 and the spatial optical modulation element 13, guides each emitted light beam from the array 11 to each matrix component of the element 13, and is provided with an optical element for distributional input; a 2nd transparent substrate 14 which is arranged between the element 13 and the light receiving element, couples plural output light beams from the element 13, and is provided with the optical element forming a propagation path for the output light beam; an optical logical element array 16 for the threshold processing arranged on the substrate 14; and a 3rd transparent substrate 17 for propagating each output light beam from the array 16 to the substrate 12 or the array 11 are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical neural computer and an optical computer component used for the optical neural computer or an optical component including the applied component.

[0002]

2. Description of the Related Art In recent years, research on optical neural computers that combine neural parallel computing with optical parallel processing has been actively conducted at academic conferences and the like. FIG. 10 is a block diagram of a conventional type optical neural computer which constitutes a typical associative memory. This optical neural computer is a model in which each output signal of a neuron is thresholded and then fed back to affect each input signal of the neuron. Finally, due to the action of this feedback signal, it converges to a specific output signal determined by the spatial light modulator for an arbitrary input signal.

The configuration of a conventional optical neural computer will be described with reference to FIG. In this optical neural computer, the output light L _IN from the light emitting element array 101 in which three LED elements are arranged in the vertical direction is arranged in a 3 × 3 matrix spatial light modulation element 102 located in the output light traveling direction.
Incident on and undergo modulation. The spatial light modulator is composed of an optical mask manufactured so that the light transmittance of each matrix component is different, and modulates the intensity of transmitted light.

The spatial light modulator can be realized by, for example, an element consisting of a fixed pattern mask formed by vapor-depositing metal on a glass plate or a variable pattern element using a ferroelectric liquid crystal. Next, the modulated output light L _OUT from the spatial light modulation element 102 is received by the light receiving element array 103 in which three light receiving elements are arranged in the horizontal direction. The signal obtained by photoelectrically converting each light receiving element of the light receiving element array 103 is input to three comparators 104, where it is electrically thresholded and each output signal is a binary value. The converted signal is fed back to the input of the light emitting element array 101.

In this structure, the light receiving element array 103
The part from the output to the light emitting element array 101 via the comparator 104 corresponds to the connection between the input and output to the neuron, and the blinking state of the light emitting element array 101 is the excitation from each neuron output input to the neuron. It corresponds to a signal indicating the state. On the other hand, the light transmittance of each matrix component of the spatial light modulator 102 corresponds to the synapse coupling strength of the neural computer.

Here, each light emitting element output light L _IN , p (p = 1,2,3) of the light emitting element array 101 is a component T of the matrix p row of the matrix components Tpq of the spatial light modulator 102.
The directivity of each element of the light emitting element array 101 is wide so that the light is uniformly input to p1, Tp2, and Tp3, and the spatial arrangement is also designed appropriately.

Similarly, of the matrix components Tpq of the spatial light modulator 102, the components T1q, T2 of the matrix q-th column
Output light L _OUT , 1q, L _OUT , 2 from q, T3q (q = 1,2,3)
q, L _{O UT} , and 3q have a wide directivity of each light-receiving element so that one light-receiving element in the q-th column of the light-receiving element array 103 can receive light with equal sensitivity, and the spatial arrangement can be appropriately designed. There is.
(However, there is a limit to miniaturization with this design.)

Next, the signal obtained by photoelectric conversion in the light receiving element array 103 is thresholded in each comparator 104 and fed back to the input of the light emitting element array 101. The corresponding process is performed electrically.

To supplement the function of the optical neural computer as a whole, an incomplete input signal is first input to the light emitting element array 101. By optically repeating vector-matrix calculation and threshold value processing, The most similar information is selected from the complete information stored in advance in some form such as the pattern of the spatial light modulator 102, and the complete output can be the blinking state (binary signal) of the light emitting element array 101. (Reference: Optics Vol. 17, No. 11 (November 1988) p. 552 "Neurocomputer" etc.).

[0010]

However, the above-mentioned neural computer has the following problems. Even if the design of the relative spatial arrangement of the light emitting and receiving element array and the spatial light modulating element and the design of the directivity of the light receiving and emitting element are optimized, the input light intensity to the spatial light modulating element matrix component and each output light sensitivity Is not easy to align. Further, when these optimized designs are performed, the size of the entire element becomes large in terms of shape. 2. The portion from the light receiving element array to the light emitting element array via the comparator has not been converted to light, and electrical wiring is required, which makes the integration and integration complicated. There was a problem. The present invention aims to solve the above drawbacks.

[0011]

In the optical neural computer of the present invention, a transparent substrate made of resin, glass or the like, which serves as a propagation path and a branch path due to internal reflection of light, is provided between the light emitting element array and the spatial light modulation element. By providing, between the light receiving element and the spatial light modulator, another transparent substrate made of resin, glass or the like to be a propagation path due to internal reflection of light and a light output coupling path is provided. In addition, the surface emitting semiconductor laser having a structure in which an optical logical operation element array is used instead of the light receiving element array and the comparator, and the light from the outside can be transmitted as the light emitting element array. By adopting an array and by providing a transparent substrate serving as a propagation path due to internal reflection of light between both element arrays, the above-mentioned 2. It is characterized by trying to solve the problem of.

Further, it is preferable that each transparent substrate of the present invention is provided with a diffraction grating and a total reflection mirror, or a thin film and a total reflection mirror to be a beam splitter, if necessary.

[0013]

In the optical neural computer of the present invention, the propagation path (and branch path or coupling path) due to internal reflection of light is used.
By using such a transparent substrate, it is easy to design for integration, and it is easier to downsize than the conventional type.
In addition, by adopting an optical logic operation element array and a surface-emitting type semiconductor laser array in addition, the feedback circuit is converted into an optical circuit, and the electrical wiring is basically a simple power supply circuit for each active element. It becomes a structure.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described below with reference to the drawings. FIG. 1 is an external perspective view of the optical neural computer of the present invention, in which the surface emitting semiconductor laser array 11, the spatial light modulator 13, and the incident light from the surface emitting semiconductor laser array 11 are directed to the spatial light modulator 13. A first transparent substrate 12 serving as a propagation path and a branch path of light for guiding, a second transparent substrate 14 serving as a propagation path by coupling a plurality of output lights from the spatial light modulator 13, and a second transparent board 14. 45 degree total reflection prism 15 for bending and propagating the output light from the transparent substrate 14 at a right angle, an optical logical operation element array 16 for light detection and threshold processing, and a surface emitting type from the optical logical operation element 16 A third transparent substrate 17, which serves as a propagation path of light to the semiconductor laser array 11, is its constituent element, and these are laminated or laminated from each direction to form an integrated structure. (In FIG. 1, the integrated product is illustrated with a large thickness, but in reality, each transparent substrate may be considered to have a thickness of about 1 mm (total thickness of about several mm).

Next, the operating principle of the optical neural computer of the present invention will be described. FIG. 2 is an exploded view of the optical elements. The details will be described with reference to the drawings of the respective parts shown in FIGS.

First, the light output from the surface-emitting type semiconductor laser array 11 obliquely enters the first transparent substrate 12 as shown in FIG. 3, and propagates in the horizontal direction while repeating internal reflection. However, a reflection mirror made of a metal film or the like is formed so that the propagating light is totally reflected on the transparent substrate side surface 31, and 1/3 of the light output is transparent on the opposite transparent substrate side surface 32 each time the output light strikes. The structure is such that the light is emitted from the substrate 12 toward the spatial light modulator 13.

As for the structure of this transparent substrate, as shown in FIG. 4, for example, a diffraction grating 33 or the like whose diffraction efficiency is controlled is produced at three positions on the side surface 32 of the transparent substrate where light is applied, and 1/3 of the total light output is produced. Each of them has a structure in which it is emitted from the transparent substrate 12 in the direction of the spatial light modulator 13, or instead of the diffraction grating 33, a thin film having optimized transmittance, reflectance, etc. is formed as a beam splitter to obtain a total light output of 1 It is possible to adopt a structure in which each / 3 is emitted from the transparent substrate 12 toward the spatial light modulator 13.

As a result, light of uniform intensity enters each matrix component of the spatial light modulator 13. Next, the spatial light modulator 13 is capable of intensity-modulating light, as in the conventional example, such as a device consisting of a fixed pattern mask formed by vapor-depositing metal on a glass plate or a variable pattern device using a ferroelectric liquid crystal. Things can be used.

A variable pattern element using a ferroelectric liquid crystal has a switching speed of about 10 ^-6 sec, and when high speed processing is required, AlGaAs / GaAs MQW (Mu
A switching speed of about 10 ^-10 sec can be realized by using a spatial light modulator that combines a modulator using the QCSE effect of the ltiQuantum well structure and a CCD (Charge Coupled Device).

The modulated light is emitted from each component of the 3 × 3 matrix, and as shown in FIG. 5, the three components in the vertical direction are combined in the next second transparent substrate 14 to form one optical signal. Becomes That is, in each of the second transparent substrates 14 extending in the vertical direction, the diffraction grating 33 and the like are formed at three positions where the emitted light from each component of the matrix of the spatial light modulator 13 reaches. The light is taken into the inside of 14 and, while being combined, is reflected to the inside of the transparent substrate 14 and propagated to a predetermined position. At this time, the diffraction grating 33 is designed such that the diffraction efficiency and the like are controlled to be optimum, and the respective light outputs incident from the three positions are weighted equally.

In the example of FIG. 2, in the right side portion of the transparent substrate 14, the combined total output of the light outputs from three places is the transparent substrate 14.
, The same total light output propagates to the central part of the transparent substrate 14 to the central part of the transparent substrate 14, and the same total light output to the upper part of the transparent substrate 14 to the left part of the transparent substrate 14. Each diffraction grating 33 is designed so that diffracted light can be obtained.

On the surface opposite to the surface on which the diffraction grating 33 is formed, the exit window 41 (transmittance 100
%), The reflection mirror is formed by vapor deposition of a metal film or the like.

The light emitted from each light extraction port of the transparent substrate 14 is the 45 ° total reflection prism 1 of the next path.
At 45, the optical path is bent at 45 degrees, propagates to the end surface of the 45-degree total reflection prism 15, and enters the optical logical operation element array 16 attached on the end surface of the prism to detect the light intensity and keep the light intensity constant. If it is above, "1", and if it is less than a certain value, "0".

As an example of the optical logic operation element, as shown in FIG. 7, structurally, there is an integrated element in which a photodetector and a semiconductor laser are monolithically made of the same kind of material (for example, InGaAsP system). Electrically, as shown in FIG. 8, a photodetector 85 and a semiconductor laser 84 are connected in series,
The photodetector 85 receives the incident light 82 as well as the output light 86 from the semiconductor laser and gives a positive feedback corresponding to the magnitude thereof (reference document; IEEE.
Trans.Electron Devices, ED-31, 805/811 (1984)).

Next, signals of light intensity corresponding to "0" and "1" of the binarized signal are incident on the third transparent substrate 17 and repeatedly reflected inside the transparent substrate 17, and the transparent substrate 17 and others. Propagate to the edge. Then, an optical signal is emitted from the other end of the transparent substrate 17 and becomes a feedback signal light which returns to the surface-emitting type semiconductor laser array 11.

A diffraction grating or an input / output window made of a thin film is provided at the incident and outgoing positions of light on the surface of the third transparent substrate 17, and a reflection mirror made of a metal film or the like is formed at the internal reflection position. The surface-emitting type semiconductor laser array 11 emits light itself (light-emission output PL) by the drive current Iop. At that time, each surface-emitting type semiconductor laser array 11 is responsive to the intensity PI of light externally input to each element of the array. The magnitude of the threshold current of the element can be reduced by ΔIth, whereby the output light from each element of the surface-emitting type semiconductor laser array increases by PI at the same drive current Iop to realize the structure of PL + PI.

FIG. 6 shows the drive current-optical output characteristics of each element of the surface-emitting type semiconductor laser array. Thereby,
Equivalently, the input signal to the optical neural computer emits itself, and the feedback signal light is
The device can be regarded as a structure in which the sum of the emission intensity and the transmission intensity is apparently input to the spatial light modulator 13 after being transmitted.

An example of the structure of the semiconductor laser device which can be adopted in the surface-emitting type semiconductor laser array 11 shown in FIG. 9 will be described below by using the idea of the equivalent structure. n-
Clad layer (n-GaAlAs) on GaAs substrate 97
96, active layer (p-GaAs) 95, clad layer (n-
AlGaAs) 94, buffer layer (p-AlGaAs)
93 and a contact layer (p-GaAs) 92 are sequentially stacked, and a p-impurity diffusion region 89 is formed in the central portion thereof.

An electrode 91 is formed on the upper surface of the contact layer 92 except for a portion facing the p-impurity diffusion region 89 in the central portion, and an AR coat 99 is provided in the facing portion to form an output window. On the other hand, in the n-GaAs substrate 97, the substrate thickness of the portion facing the p-impurity diffusion region 89 in the central portion is thin, and the AR coat 99 is also provided in this portion to serve as an input window for the transmitted light 88 from the outside. , N-GaAs
The electrode 98 is formed on the other portion of the substrate 97.

Only the region including the p-impurity diffusion region 89 in the central portion has a pn structure, and the current flowing therethrough causes
The laser light emitted from the active layer 95 is emitted toward the output window. The feedback signal light is transmitted through the element from the input window toward the output window, and the sum 87 of the emission intensity and the transmission intensity is obtained from the output window.

In the above embodiments, the optical neural computer using the spatial light modulator composed of 3 × 3 matrix components has been described. Of course, the space composed of N × N matrix components (N: natural number). It can be easily inferred that the present invention can be applied to an optical neural computer using an optical modulator.

[0032]

As described above, the optical neural computer of the present invention described in the embodiment is designed for integration by using a transparent substrate which serves as a propagation path (and branch path or coupling path) due to internal reflection of light. It is easy to do, and it is easier to downsize than the conventional type. In addition, by adopting the optical logic operation element array and the surface emitting semiconductor laser array, the feedback circuit becomes a simple optical structure.

[Brief description of drawings]

FIG. 1 is an external perspective view of an optical neural computer according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view for explaining the operation principle of FIG. 1 separately for each optical element.

FIG. 3 is a side view of a first transparent substrate showing the propagation of incident light by internal reflection according to an embodiment.

FIG. 4 is a perspective view showing a structure of a first transparent substrate according to an embodiment.

FIG. 5 is a second transparent substrate structure diagram showing light coupling and propagation inside the transparent substrate according to the embodiment.

FIG. 6 is a characteristic diagram showing drive current vs. optical output characteristics of each element of the surface-emitting type semiconductor laser array according to the example.

FIG. 7 is a structural diagram showing an example of an optical logical operation element according to an example.

FIG. 8 is an equivalent circuit diagram of FIG. 7.

FIG. 9 is a structural diagram showing an example of a semiconductor laser device that constitutes a surface-emitting type semiconductor laser array according to an example.

FIG. 10 is a structural diagram showing a configuration of a conventional optical neural computer.

[Explanation of symbols]

 11 Surface Emitting Semiconductor Laser Array 12 First Transparent Substrate 13 Spatial Light Modulator 14 Second Transparent Substrate 15 45 Degree Total Reflection Prism 16 Optical Logic Operation Element Array 17 Third Transparent Substrate

Claims (4)

[Claims] 1. The light emitted from the light emitting element array is modulated by a spatial light modulating element in a matrix form, and the light output from the spatial light modulating element is detected by a light receiving element to perform threshold processing. In the optical neural computer of the type to be performed, it is provided between the light emitting element array and the spatial light modulating element to guide each emitted light from the light emitting element array to each matrix component of the spatial light modulating element, and to distribute and input. A first transparent substrate having an optical element, and an optical element provided between the spatial light modulation element and the light receiving element to couple a plurality of output lights from the spatial light modulation element and form a propagation path thereof are provided. A second transparent substrate, an optical logic element array for threshold processing provided on the second transparent substrate, and each output light of the optical logic element array propagated to the first transparent substrate or the light emitting element array. Let Light neural computer comprising a third transparent substrate. 2. The optical neural computer according to claim 1, wherein the optical element includes a diffraction grating and a total reflection mirror, or a thin film and a total reflection mirror to be a beam splitter. 3. The first transparent substrate and the second transparent substrate according to claim 1.
An optical component characterized in that the device is integrated and miniaturized by using at least one of the transparent substrate, the optical logic element array, and the third transparent substrate. 4. The first transparent substrate and the second transparent substrate according to claim 1.
Using at least one of the transparent substrate, the optical logic element array, and the third transparent substrate, the feedback signal circuit which is the threshold processing and its peripheral portion is processed by light. Optical neural computer to do.