JPH06110367A - Optical associative memory device - Google Patents

Abstract

PURPOSE:To provide an optical associative memory device with stable optical characteristic. CONSTITUTION:A hologram recording medium 6 is stacked on the lover plane of a rotary transparent disk 4. Most part of an optical system for the recording/ reproduction of a hologram for the medium 6 are fixed on a transparent substrate 2 underneath the disk 4. The optical system fixed on the transparent substrate 2 is provided with an optical waveguide optical system 26a including a phase conjugate mirror for threshold value processing. Since the phase conjugate mirror is fixed on an optical waveguide, no alignment adjustment with high precision required, and it is hard to receive the influence of mechanical vibration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical associative storage device for optically reproducing stored data from input data.

[0002]

2. Description of the Related Art The progress and spread of computers are remarkable, and they play an important role in all fields. As a result of such a situation, there is an increasing demand for high-performance computers that can be applied to sophisticated processing that requires even higher speed computation. However, as the mechanical limitation of conventional sequential processing becomes a problem, the need for a completely new computer based on a different concept and hardware has been recognized.

For example, inferring an accurate output from an ambiguous input, reproducing perfect data from incomplete data, or selecting an image most similar to the input image from a large amount of stored images. The reasoning process of is one of the fields that is difficult to execute on a computer by sequential processing.

There is an increasing demand for a configuration and hardware suitable for such inference processing, and many proposals have been made to meet the demand. One of the powerful ones is an optical associative memory device using a hologram and an optical phase conjugate mirror. This device is an “All-optical associativ
e memory with shift invariance and multiple-imager
ecal ”Optics Letters / Vol.12, No.5 / May 1987 pp346〜
348.

FIG. 35 shows a schematic diagram of the optical associative memory device disclosed in the above-mentioned document. The operation for storing a plurality of images in the hologram storage medium by this device is as follows.

[0006] The recording beam undergoes spatial light modulation with a first image (eg the word WAVES) 1
The object wave of the first image 1 is generated. This object wave is
It is reflected by the beam splitter 3, condensed by the Fourier transform lens 5, and enters the hologram storage medium 7 as a Franhofer analysis image. At the incident position, the first
The reference wave 9 of is incident at the same time.

As a result of the interference between the object wave from the first image 1 and the first reference wave 9, the interference pattern is stored in the hologram storage medium 7 as a Fourier transform hologram. The Fourier transform hologram of the second image (for example, the word OPTIC) 11 is also stored in the hologram storage medium 7 as an interference pattern between the object wave from the second image 11 and the second reference wave 13. Here, the second reference wave 13 has an incident angle different from that of the first reference wave 9.

By using different angles of incidence of the reference waves, Fourier transform holograms of several different images can be stored in one hologram storage medium 7.

Generally, data recorded on a non-optical recording medium such as a hard disk or a floppy disk is output by designating an address where the data is recorded.

However, in this optical associative storage device, by inputting an input image corresponding to a specific image stored in the hologram storage medium 7 into the hologram storage medium 7, a specific image is output from the multiple storage hologram. . In this case, the input image required for the output image does not have to be exactly the same as the stored image, and within some tolerance, even an incomplete or fragmentary input image, or a similar input image. Good.
The operation for outputting such an image is as follows.

When an incomplete image 15 (for example, the letter W) forming a fragment of the first image (WAVES) 1 is input to the optical associative memory, the incomplete input image is a hologram storage medium in which the images are multiply stored. 7 is made to enter through the same optical path as the writing wave.

At this time, by the optical correlation calculation of the hologram,
Each stored image is output with a light intensity corresponding to the degree of similarity to the incomplete input image. It means that the output image with the highest light intensity has the highest similarity to the imperfect input image.

These mixed output images enter the optical phase conjugate mirror 17, are thresholded, and are re-propagated as a phase conjugate wave along the input optical path. Thresholding in the phase conjugate mirror enhances or amplifies only the complete output image that has the highest similarity to the incomplete input image, and suppresses the light intensity of all other output images.

As a result, the phase conjugate wave for the complete output image re-enters the hologram storage medium 7 as a phase conjugate wave for the light emitted from the hologram storage medium 7. As a result, the complete output image (W
AVES) 19 is optically associated with the incomplete input image and output.

[0015]

An optical element having a nonlinear reflectance, which is important for realizing associative memory, that is, a phase conjugate mirror is a reflection mirror by degenerate four-wave mixing using barium titanate crystal. This phase conjugate mirror requires pump waves (not shown in FIG. 35) that are aligned to each other with high precision. Therefore, when the phase conjugating mirror is actually used by being incorporated in the system, the reliability of the system may be lowered due to undesired vibration such as mechanical vibration.

Since the characteristics of this phase conjugate mirror are very dependent on the optical properties of the optical material, the degree of freedom of the optical design values (threshold, wavelength and power of reference light, etc.) of the system is limited. To be done. As a result, the cost of the system can be high.

Therefore, an object of the present invention is to provide an optical associative memory device which does not require highly precise adjustment of an optical system and is highly reliable and low in cost.

[0018]

According to one aspect of the present invention, one input data is reproduced by optically associating the most similar one of a plurality of prestored data. An optical associative storage device for generating a reference wave, a storage medium in which a hologram is stored, a reference wave from the reference light source, and a plurality of storage data to be stored in the storage medium in advance. As a result of interfering with the object wave of, the storage means for storing the hologram corresponding to each stored data in the storage medium, the reference wave from the reference light source, and the object wave from any one input data , Reproduces multiple holographic images corresponding to multiple stored data with light intensity according to the correlation between the input data pattern and the stored data pattern based on the optical correlation calculation And a thresholding means for thresholding a plurality of reproduced holographic images so as to enhance the light intensity of one stored data having a pattern most similar to the pattern of the input data. An optical associative memory device including an optical waveguide including the optical waveguide.

[0019]

According to the above configuration, since the threshold value processing is executed in the optical waveguide, it is not necessary to perform highly accurate alignment such as a phase conjugate mirror made of a reflecting mirror, and the threshold value can be controlled electrically. Processing is also possible.

[0020]

1 shows an optical associative memory device according to a first embodiment of the present invention.

The optical associative memory device includes a first optical system fixed to the transparent substrate 2, a second optical system arranged above the substrate 2, and a space between the first and second optical systems. The transparent disk 4 is provided and has a hologram recording (or storage) medium 6 laminated on the lower surface thereof, and a drive mechanism (not shown) for the transparent disk 4.

The first optical system is composed of a plurality of small-sized optical elements forming a large part of the optical system of the optical associative memory device. Since these optical elements are fixed to the substrate 2, the entire optical system of the optical associative storage device can be downsized, and once fixed, no precise adjustment is required and the optical characteristics can be stabilized.

In particular, as shown in FIG. 2, the first optical system is
First and second prisms 8 and 10 and a mirror 14 for deflecting and splitting a beam, spatial light modulators 16 and 18 for spatially intensity-modulating light by electric signal control,
An image sensor 20 for converting reproduced two-dimensional optical information into an electric signal, and a phase conjugate mirror 22 by an integrated optical system.
The optical waveguide optical system 26a including the above, and the hologram element 24 for input / output to / from the optical waveguide optical system 26a.

The second optical system includes first and second mirrors 27a and 27b arranged above the substrate 2 so that the light guided from the first optical system is incident on the transparent disk 4.
And a split prism 12 arranged between the substrate 2 and the transparent disk 4. Of all the optical systems of the optical associative memory device, the one not fixed to the substrate 2 is the branch prism 1.
2 and the first and second mirrors 27a and 27b and the light source (not shown) only.

The transparent disk 4 is replaceably mounted on a rotary shaft (not shown) of the drive mechanism, and can be rotated by a predetermined angle by the drive mechanism when recording (storing) or reproducing information. The details of the drive control of the transparent disk 4 are as follows.
Since it is the same as the conventional optical disc, the description is omitted here.

The number of data that can be stored per unit area of the hologram recording medium is limited by the resolution of the hologram recording medium 6. However, according to the transparent disk 4, since the hologram storage medium 6 is a rotating disk, the details of the structure of the above-described optical associative storage device capable of dramatically increasing the recording capacity of one hologram recording medium 6 are described. Will be described together with the process of recording and reproducing information.

FIG. 3 shows the optical path of the information recording process in the optical associative memory device of FIG. A laser beam emitted from a light source (not shown) enters a first prism 8 and is split into a first beam and a second beam here. The first beam reflected in the direction normal to the surface 2 a of the substrate 2 is reflected by the mirrors 27 a and 27 b arranged above the substrate, passes through the transparent disc 4, and enters the hologram recording medium 6.

On the other hand, the second beam that has passed through the first prism 8 passes through the lower side of the substrate 2 and enters the second prism 10, where it is split into third and fourth beams again. .
The third beam reflected in the direction normal to the substrate surface 2a is
It is shielded by the spatial light modulator 16. The fourth beam that has passed through the second prism 10 is reflected by the mirror 14 in the direction normal to the substrate surface 2a, passes through the transparent disk 4, and enters the region near the waveguide optical system 26.

In this area, a hologram coupler 28 for coupling the spatial light with the waveguide light is provided. The beam incident on this region is guided through the coupler 28 into the waveguide optical system 26a. The optical waveguide of the waveguide optical system is a multimode waveguide. The beam incident on the hologram coupler 28 is coupled to a specific one of the natural waveguide modes of this multimode waveguide.

FIG. 4 shows a top view of the waveguide optical system 26a. The waveguide optical system 26a works as shown in FIG. 5 during recording. The guided light coupled from the hologram coupler 28 to a specific mode in the waveguide has its optical path converted by the first waveguide type switching mirror 30 and the first waveguide mirror 32, and enters the waveguide mode conversion element 34. .

In the guided mode conversion element, the incident beam of a specific mode is converted into a desired guided mode by external control. For example, all incident light in the 0th order mode is converted into the 1st or 2nd order mode.

The guided beam that has passed through the mode conversion element 34 propagates in a guided mode in accordance with external control, is subjected to optical path conversion by the second waveguide mirror 36 and the second waveguide type switching mirror 38, and is multiplexed. It is incident on the volume hologram coupler 40. The multi-volume hologram coupler 40 is a special coupler whose emission position and emission angle are different depending on the incident mode, and is designed so that any guided mode light is incident on the hologram recording position of FIG. . Therefore, the incident angle of the beam with respect to the hologram recording position can be changed according to the control by the waveguide mode conversion element.

As a result, at the hologram recording position, the hologram is recorded by the reference beams having different incident angles according to the external control.

At this time, the first beam reflected by the first prism 8 is two-dimensionally intensity-modulated by the spatial light modulation element 18 provided in the optical path to form a desired two-dimensional pattern on the hologram recording medium 6. Multiple recording is possible with reference beams having different incident angles within.

By performing the above-mentioned multiple recording operation while successively rotating the transparent disk 4, a large amount of multiple two-dimensional pattern data can be recorded on one disk 4 as a volume hologram.

In the multiple recording operation described above, several guided wave devices, described in detail below, play an important role.

The guided mode conversion element 34 for externally controlling the incident angle of the recording reference beam will be described. In order to convert a certain guided mode to another guided mode, phase modulation may be performed by a grating having the same wave number as the difference in propagation constant between the two. However, with a normal static grating, external control of the wave number of the grating is impossible.

FIG. 6 shows the structure of the grating for enabling the external control of the wave number. The waveguide layer 42 and the grating layer 44 sandwich a gap layer 46 as a phase modulation region between them. Any one of these layers may be external electrical (or magnetic, thermal, optical)
It is a material whose refractive index can be changed by various controls.

FIG. 7 shows, as an example, the structure of the gap layer 46 under electrical control.

In FIG. 7, the gap layer 46 is a material exhibiting electro-optical characteristics, and its refractive index can be changed by applying a voltage from the power supply 52 to the external electrode 50.

Since the gap layer 46 normally corresponds to the clad in the waveguide, the waveguide mode field distribution changes when the refractive index of the gap layer 46 changes. Specifically, the leakage amount of the evanescent wave in the gap layer 46 changes. Focusing on this point, by appropriately setting the thickness of the gap layer 46, the leakage of the guided light can be superimposed / non-superposed on the grating layer 44 in accordance with ON / OFF of the voltage application. The grating of FIG. 7 may be, for example, a device that causes a mode conversion when a voltage is applied from the outside and otherwise acts as a normal waveguide line.

As shown in FIG. 8, the above-mentioned devices are prepared in advance according to desired mode conversion, and arranged in an array along the propagation direction of guided light. By selecting the device to which the voltage is applied by using the switches SW1 to SW4, it is possible to execute the desired mode conversion according to the selection.
Although the device using the electro-optical effect has been described here, a device using another effect may be used as long as it can change the refractive index by external control.

The layer whose refractive index is to be changed is the gap layer 46.
However, the same function as described above can be realized in either case.

In order to convert each guided mode beam thus changed into a spatial beam and use it as a reference beam, the above-mentioned multi-volume hologram coupler 40 is required. This hologram coupler will be described.

A usual grating coupler can output guided modes having different propagation constants as different emission angles. However, the emission position of the beam is one (region where the grating exists) for any mode, and the irradiation position of the emission beam changes depending on the mode. Therefore, it is difficult to use the emitted beam as the reference light for the multi-volume hologram recording.

Therefore, in the present invention, the multiple hologram coupler 40 manufactured by the following special method is used.
The coupler 40 is multiplexed and recorded on the hologram recording material 54 provided on the waveguide by individual guided mode light and spatial reference light having different incident angles.

The form of the hologram recording material provided in the waveguide is, for example, a clad (FIG. 9A), a part of the waveguide layer (FIG. 9B), or the waveguide layer itself (FIG. 10A). , A loading film locally provided on the waveguiding layer (FIG. 10B),
Other forms are conceivable, but in principle any form is acceptable.

Referring to FIGS. 11 to 14, the steps of forming the hologram coupler 40 on the hologram recording material 54 of the waveguide are as follows.

(I) A volume hologram is recorded by a first reference beam having a first incident angle θ1 with respect to a 0th-order mode beam (FIG. 11).

(Ii) The second reference beam that propagates the first-order mode beam, has the second incident angle θ2 (where θ1 ≠ θ2), and intersects the first reference light at a certain point, Further, a volume hologram is recorded (FIG. 12).

(Iii) In the same manner as in steps (i) and (ii) above, recording is sequentially performed by using mode beams of the 2nd ... mth order to record a multi-volume hologram in the waveguide ( 13 and 14).

(Iv) By subjecting the multi-volume hologram in step (iii) above to a predetermined development process, a hologram coupler 40 having functions separated and multiplexed according to each mode is formed.

15 to 18 show the hologram coupler 4.
0 operation is shown.

When a 0th-order, 1st-order, 2nd-order, m-th order waveguide beam is incident on the hologram coupler 40 from the opposite direction from the recording (steps (i) to (iii)), the recording reference beam is generated. Is played. Since the hologram coupler 40 has the mode selectivity corresponding to the wavelength selectivity and incident angle selectivity of the volume hologram, the specific mode is coupled only to the recording reference beam of the hologram to which it corresponds. As a result, it becomes possible to convert the individual modes into spatial beams that are incident on the same place at different exit angles.

First and second waveguide type switching mirrors 30,
38 plays a role as a reflecting mirror in the above-described recording process, but needs to play a role as a transmitting mirror in the reproducing process. These two roles of the waveguide-type switching mirrors 30 and 38 are realized by switching the operation and non-operation of the grating according to the external control, similarly to the waveguide mode conversion element.

FIG. 19 shows the structure of the waveguide switching mirror 30 or 38. The difference between this mirror and the grating layer structure of FIG. 6 is that the grating is a waveguide beam splitter 56. The cross-sectional structure of this mirror is the same as the grating layer structure of FIG. This waveguide-type switching mirror can turn on / off the function of the beam splitter by changing the field distribution of the guided light under some control from the outside, just as in the case of FIG.

In the optical associative recording apparatus of the present invention, the waveguide type optical system including the above-mentioned waveguide type elements is a reference light source for hologram recording.

FIG. 20 shows an optical path in the reproducing process of the optical associative recording device.

A laser beam emitted from a light source (not shown) emits the first and second prisms 8 and 1 as in the recording process.
It is branched by 0 and the mirror 14.

The beam reflected by the first prism 8 in the direction normal to the substrate surface 2a is blocked by the spatial light modulator 18.

The beam reflected by the second prism 10 in the direction normal to the substrate surface 2a is intensity-modulated into a two-dimensional pattern to be input as a key pattern by the spatial light modulator 16, and then passes through the branch prism 12. Then, it is incident on the volume-type multiplex hologram of the transparent disk 4 as the reading light. As a result, each reference light is reproduced by the optical correlation calculation according to the correlation strength with the storage pattern, and is incident on the multiple volume hologram 40 (see FIG. 4) of the waveguide optical system 26a. Here, each reference light is converted into guided light of a corresponding mode and propagated.

FIG. 21 shows the waveguide optical system 26 during the reproducing process.
The top view of a is shown. The multimode waveguide beam introduced from the multi-volume hologram 40 passes through the waveguide switching mirror 38 and is incident on the nonlinear optical medium 58 provided in the waveguide optical system 26a. On the other hand, the beam that passes under the substrate 2 and is reflected by the mirror 14 in the direction normal to the substrate surface is guided by the hologram coupler 28 into the waveguide optical system 26a.
Guided in and propagate in the opposite direction.

The optical path of this guided beam, after passing through the guided switching mirror 30, is guided by the beam splitter 60.
The optical path is reflected by and is reflected by the waveguide mirrors 62 and 64, and the optical path that is transmitted through the waveguide beam splitter 60 and reflected by the waveguide mirrors 66, 68 and 70 is branched. The two branched waveguide beams enter the nonlinear optical medium 58 so as to face each other. These two guided beams and the above-mentioned multimode beam are combined into the nonlinear optical medium 68.
As a result of incidence on the beam, a beam re-propagating in the optical path of the multimode beam is generated. As a result, a phase conjugate mirror is formed by degenerate four-wave mixing.

Each waveguide mode beam whose intensity is modulated according to the correlation intensity as shown in FIG. 22 (A) is thresholded by the phase conjugate mirror in the waveguide, and then, as shown in FIG. 22 (B). An enhanced guided mode beam is emitted as shown.
This beam propagates backward in the incident light path, passes through the multi-volume hologram 24, and is incident on the multi-volume hologram on the transparent disk 11 again at the enhanced exit angle of the guided mode beam. As a result, the output pattern most similar to the input pattern is reproduced.

In FIG. 20, the reproduced pattern beam is branched by the prism 12 and reflected, and finally enters the image sensor 20 where it is photoelectrically converted.
In order to downsize the optical system, downsizing, low power consumption, high density, etc. of the image sensor 20 are required. The image sensor 20 that satisfies this request is, for example, a charge modulation device.

As described above, according to the optical associative memory device of the present invention, most of the optical elements are integrated on one substrate, and the optical system of the phase conjugate mirror, which is the most difficult to adjust, is placed in the waveguide. Since it is fixed and stabilized, the entire device can be downsized and stabilized.

FIG. 23 shows a second embodiment of the present invention. The difference between this embodiment and the first embodiment is that instead of the waveguide optical system 26a (FIG. 21) for optical threshold processing by the non-linear optical medium 58 in the first embodiment, the electric power by the photoelectric integrated circuit is used. Optical system 26 for dynamic thresholding
b is used. The configuration excluding the waveguide optical system 26a is the same as that of the first embodiment, and therefore its description and illustration are omitted. A second embodiment will be described. Further, in the waveguide optical system 26b, the same components as those in the first embodiment are designated by the same reference numerals.

The optoelectronic integrated circuit of the waveguide optical system 26b includes a detector array 74 and an electrical threshold processing circuit 86.

As shown in FIGS. 24 to 28, in the detection element array 74, a multimode waveguide 78 provided with a hologram recording material 76 is arranged with a number of detection elements 80 corresponding to the number of modes, and each detection element 80 is arranged in each element. It is a volume hologram array recorded by interference exposure of incident spatial light and guided light of each mode.

The detection element array 74 independently guides each mode light to the detector corresponding to the mode light due to the mode selectivity of the volume hologram.

The threshold value processing in the second embodiment is as follows.

The multi-waveguide beam that has entered the waveguide 78 from the volume-type multiplex hologram coupler 40 is reflected by the waveguide switching mirror 38 and the waveguide mirror 82 and enters the detector array 74. The array 74 independently detects individual modal powers and converts them into electrical signals. The electric signal is appropriately subjected to signal processing such as amplification and then given to the electric threshold value processing circuit 84. Here, the same processing as the threshold processing (see FIG. 21) of the first embodiment is electrically executed, and the result is given to the waveguide mode conversion element 86.
The mode conversion element 34 converts the guided light propagating in the opposite direction from the hologram coupler 28 based on the electrically processed threshold value treatment result, and makes it enter the volume type multiplex hologram coupler 40. This plays the same role as the optical phase conjugate mirror of the first embodiment.

Such electrical threshold processing is easier to control externally than optical threshold processing and does not use a special property such as optical nonlinearity. The degree of freedom in optical design such as setting, wavelength of the light source used, and light intensity is expanded, which is more practical.

As shown in FIG. 29, in the writing reference beam according to the second embodiment, the waveguide type switching mirror 38 is turned off, and the guided light from the hologram coupler 40 is converted into a desired mode order by the waveguide mode conversion element 34. Is converted to.

FIG. 30 shows a third embodiment of the present invention in which an optical associative memory device is used as a shape determining device. The structure of the apparatus of this embodiment is similar to that of the first or second embodiment.

Holographic recording medium 6 of transparent disk 4
For example, various triangular patterns 90 as shown in FIG. 31, for example, are multiply stored, and similarly, as shown in FIG. 30, various quadrangle 92, circle 94, and other various pattern patterns of various shapes are also multiply stored.

When an unknown figure pattern is input to this apparatus after storing a sufficient amount of information, a figure having a pattern most similar to the input pattern is stored in the stored information (all hologram information). You can search and play in a short time.

Here, the combination of the optical associative storage device and the information processing device (computer or the like) by the address designation method will be described. The format of the data processed by the optical associative memory is such that visible image data (eg, photographs,
If it is limited to only video, the range to which the optical associative memory device can be applied in information processing technology is limited.

On the other hand, an information processing apparatus based on the address designation method (hereinafter referred to as a non-associative information processing apparatus) is difficult to realize associative memory and is not suitable for processing visible image data.

Therefore, by combining the optical associative storage device with an information processing device by the address designation system, not only visible image data but also a wide range of data processing can be performed, and associative storage can be realized.

FIG. 32 shows a fourth embodiment of the present invention. The illustrated personnel search system is an optical associative storage device 10 of the present invention.
0 and a workstation 110 having a known magneto-optical disk drive 102, display 104, etc. are combined. The optical structure of the optical associative memory device 100 is the same as that of the first to third embodiments.

In the recording area of the magneto-optical disk (not shown) of the workstation 110, detailed personal information (name, age, educational background, place of birth, etc.) of each individual is recorded for a large number of human resources list. ing.

On the other hand, as shown in FIG. 33, in the hologram recording medium 6 of the disk 4 of the optical associative storage device, facial expressions of various expressions and face directions of each individual are stored as one hologram for each person. There is. Further, the address of the magneto-optical disk on which personal information corresponding to the face photograph is recorded is stored at the edge of the face photograph as a pattern of bit numbers such as a barcode.

According to such a personnel retrieval system, the personal information stored can be retrieved by the workstation by inputting only the facial photograph into the optical associative storage device. In this case, the facial photograph that should be input is
It does not have to be exactly the same as the stored photo.

The operation steps for searching for an individual by the personnel search system are as follows.

(I) Input the obtained facial photograph of the specific individual into the optical associative memory.

(Ii) Scanner for reproducing beam (not shown)
And the address relating to the facial photograph having the most similar pattern to the input facial photograph is displayed on the display 104 of the workstation 110 as shown in FIG.

(Iii) Based on the address obtained in step (ii), the workstation 110 retrieves the personal information corresponding to the input facial photograph from the magneto-optical disk and displays it on the display 104. In this way, it is possible to search for a specific individual based on the ambiguous input data of only the facial photograph.

By adopting an appropriate operation system, the workstation 110 can simultaneously display the input face photograph, address, personal information, etc. by using a multi-window like the screen of the display 104 in FIG. Is.

According to this embodiment, the image data to be input to the optical associative storage device is simply used as an input pattern for data retrieval, and detailed data retrieval related to the image data can be easily retrieved by the workstation. And it can run very fast. This is applicable to various data search systems as well as human resource search systems.

Alternatively, the present invention can be applied to an artificial intelligence robot or the like which acts by judging the situation by itself even under the condition that the computer is not programmed.

[0092]

According to the optical associative memory device of the present invention, the threshold processing is executed by the optical waveguide, so that the optical characteristics are stabilized and the degree of freedom in the optical design is increased. As a result, a highly reliable and low cost optical associative memory device is provided.

[Brief description of drawings]

FIG. 1 is a side view schematically showing an optical associative memory device according to a first embodiment of the present invention.

FIG. 2 is a top view showing a substrate to which most of the optical system in FIG. 1 is fixed.

FIG. 3 is a diagram showing an optical path in a recording operation of the apparatus of FIG.

FIG. 4 is a top view showing a waveguide optical system in FIG.

5 is a diagram showing an optical path in a recording process of the waveguide optical system of FIG.

6 is a sectional view showing the structure of a grating of the device in FIG.

FIG. 7 is a cross-sectional view corresponding to FIG. 6 and showing a structure of a grating having a gap layer for electrically controlling a refractive index.

FIG. 8 is a cross-sectional view for explaining a method of forming the grating of FIG.

9A and 9B are diagrams showing a form of the hologram recording medium in FIG. 1, in which FIG. 9A is a sectional view showing a medium made of a clad, and FIG. 9B is a sectional view showing a medium made of a part of a waveguiding layer. .

10A is a cross-sectional view showing a medium composed of a waveguide layer itself, and FIG. 10B is a cross-sectional view showing a medium composed of a loading film locally provided on the waveguide layer. It is a figure.

FIG. 11 is a diagram showing a first step for forming a hologram coupler on a hologram recording medium, showing an operation of recording a hologram by a 0th-order mode beam.

FIG. 12 is a diagram showing a second step using the primary mode beam, following the steps shown in FIG. 11;

FIG. 13 is a diagram showing a third step using the secondary mode beam following the steps shown in FIG. 12;

FIG. 14 is a diagram showing a fourth step using the m-th order mode beam, following the steps shown in FIG. 13;

FIG. 15 is a diagram showing an operation of the hologram coupler corresponding to the first step (FIG. 11).

16 is a diagram corresponding to the second step (FIG. 12), similar to FIG.

FIG. 17 is a diagram corresponding to the third step (FIG. 13), similar to FIG.

FIG. 18 is a diagram corresponding to the fourth step (FIG. 14), similar to FIG. 15;

19 is a cross-sectional view showing the structure of the waveguide type switching mirror in FIG.

20 is a diagram showing an optical path in a reproducing process of the optical associative recording device of FIG. 1. FIG.

21 is a top view showing the waveguide optical system in FIG. 1. FIG.

22A and 22B are diagrams related to thresholding processing by the phase conjugate mirror in FIG. 1, and FIGS. 22A and 21B are mode order-intensity of each waveguide beam incident on and emitted from the phase conjugate mirror. It is a graph which shows a characteristic.

FIG. 23 is a diagram showing an electrical threshold processing system in the optical associative memory device of the second embodiment.

FIG. 24 is a diagram showing a step of recording a volume hologram to form each element of the detection element array of FIG. 23, and a recording step using guided light of a 0th mode.

FIG. 25 is a diagram showing a recording step using guided light of a first-order mode, following FIG. 24;

FIG. 26 is a diagram showing a recording step using guided light of a secondary mode, following FIG. 25;

FIG. 27 is a diagram showing a recording step using guided light of an m-th mode, following FIG. 24;

FIG. 28 is a cross-sectional view showing a detection element array as a volume hologram array formed by the steps of FIGS. 23 to 27.

FIG. 29 is a diagram showing an optical system for forming writing reference light in the second example.

FIG. 30 is a diagram schematically showing an optical associative memory device as a shape determination device according to the third embodiment of the present invention.

FIG. 31 is a diagram showing an example of a shape pattern used in the third embodiment.

FIG. 32 is a perspective view showing a human resources search system in which an optical associative memory device and a workstation are combined according to the fourth embodiment of the present invention.

FIG. 33 is a diagram showing an example of a face photograph to be stored in the optical associative storage device in the fourth example.

FIG. 34 is a diagram showing a display example of a storage address of a workstation in which information about a face photograph having a pattern most similar to the input photograph is stored in the fourth embodiment.

FIG. 35 is a diagram schematically showing a conventional optical associative memory device.

[Explanation of symbols]

6 ... Hologram storage medium, 22 ... Phase conjugate mirror (threshold processing means), 26a, 26b ... Optical waveguide optical system, 28 ...
Hologram coupler (storage means, reproduction means), 84 ... Electrical threshold processing circuit (threshold processing means).

Claims (1)

[Claims] 1. An optical associative memory device for optically retrieving one input data, which is most similar to one of a plurality of prestored data, by optically associating with the input data and generating a reference wave. As a result of causing the reference light source, the storage medium in which the hologram is stored, the reference wave from the reference light source, and the object wave from each of the plurality of storage data to be stored in the storage medium in advance, each storage data Storage means for storing the corresponding hologram in the storage medium, the reference wave from the reference light source, and the result of causing the object wave from any one input data to interfere, based on the optical correlation calculation,
A reproducing means for reproducing a plurality of holographic images corresponding to a plurality of stored data with a light intensity according to the correlation between the input data pattern and the stored data pattern, and a pattern most similar to the input data pattern. An optical associative memory device comprising: an optical waveguide including thresholding means for thresholding a plurality of reproduced holographic images so as to enhance the light intensity of one stored data having.