JPH04333090A - Optical pattern recognition device - Google Patents

Abstract

PURPOSE:To accurately recognize a pattern even if the pattern to be recognized is partially absent or blurs. CONSTITUTION:The optical pattern recognition device which processes recognized pattern light by Fourier transformation and irradiates a matched filter where a reference pattern is written to find the correlation between the reference pattern and the pattern to be recognized from diffracted light generated by the matched filter is equipped with phase conjugate mirrors 42 and 43 which are arranged optically opposite at the positions where the matched filter is interposed on the optical path of diffracted light.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pattern recognition device that performs pattern recognition using optical correlation.

0002

2. Description of the Related Art In such a recognition device, a matched filter is first created. FIG. 11 is a block diagram of a matched filter creation device. The laser beam output from the laser oscillator 1 is split into two directions by the beam splitter 2, and one of the laser beams is reflected by each mirror 3 and 4, and the beam diameter is expanded by the expanding collimator system 5 and sent to the dry plate as a reference beam. 6 at a predetermined angle. The beam diameter of the other laser beam that is branched at the same time is expanded by an enlarging collimator system 7, passes through a reference pattern mask 8, is Fourier transformed by a Fourier transform lens 9, and is irradiated onto a dry plate 6. As a result, a Fourier spectrum of the reference pattern is generated on the dry plate 6 and written on the dry plate 6. Then, a plurality of reference patterns are written on the dry plate 6 by changing the incident angle of the reference light onto the dry plate 6. This dry plate 6 is developed and becomes a matched filter.

Next, pattern recognition is performed using the configuration shown in FIG. The beam diameter of the laser beam output from the laser oscillator 1 is expanded by the expanding collimator system 10, and the beam diameter is irradiated onto the pattern mask 11 to be recognized. The laser beam that has passed through the recognized pattern mask 11 is Fourier transformed by a Fourier transform lens 12 and then irradiated onto the matched filter 6 . As a result, a correlation calculation is performed between the reference pattern and the recognized pattern, and if the pattern is the same as the recognized pattern, the light is diffracted in the direction of the reference light, and the camera is directed in this direction.
3 is placed.

However, in such pattern recognition, if the pattern to be recognized is chipped or faded, it is difficult to accurately recognize the pattern. In this case, even if the pattern to be recognized has the same size and the same slope as the reference pattern written in the matched filter 6, it is difficult to accurately recognize the pattern.

[0005]

As described above, if the pattern to be recognized is chipped or faded, it is difficult to accurately recognize the pattern. SUMMARY OF THE INVENTION An object of the present invention is to provide an optical pattern recognition device that can accurately recognize a pattern even if the pattern to be recognized is chipped or faded.

[0006]

[Means for Solving the Problems] The present invention provides a method for Fourier-transforming a recognized pattern light to irradiate it onto a matched filter in which a Fourier spectrum of a reference pattern is written, and to obtain a reference pattern from diffracted light generated by the matched filter. An optical pattern recognition device that obtains a correlation between a pattern and a pattern to be recognized is equipped with phase conjugate mirrors that are optically placed opposite to each other on the optical path of the diffracted light generated by the matched filter and at positions where the matched filter is interposed. This is an optical pattern recognition device that attempts to achieve the above object.

The present invention also provides a matched filter in which a Fourier spectrum of an optically logarithmically transformed reference pattern is written, and an irradiation device that logarithmically transforms and then Fourier transforms the pattern light to be recognized and irradiates it onto the matched filter. An optical system, phase conjugate mirrors optically placed opposite to each other on the optical path of the diffracted light generated by the matched filter and with the matched filter interposed therebetween, and a reference pattern is generated from the diffracted light amplified by these phase conjugate mirrors. This is an optical pattern recognition device that attempts to achieve the above object by including recognition means for determining the correlation between the pattern and the pattern to be recognized.

In this case, if the reference pattern of the matched filter is optically converted into polar coordinates and written,
The pattern light to be recognized is subjected to polar coordinate transformation by an irradiation optical system, then Fourier transformed, and then irradiated onto a matched filter.

Furthermore, if the reference pattern of the matched filter is optically polar coordinate transformed and logarithmically transformed, the pattern light to be recognized is polar coordinate transformed and logarithmically transformed by the irradiation optical system, and then Fourier transformed, and then the matched filter is irradiated.

0010

[Operation] By providing such a means, the diffracted light generated when the matched filter on which the Fourier spectrum of the reference pattern is written is reflected between each phase conjugate mirror, increasing its light intensity. .

Furthermore, by providing the above means, the pattern light to be recognized is logarithmically transformed by the irradiation optical system, then Fourier transformed and irradiated to the matched filter, and the diffracted light generated at this time is transmitted between each phase conjugate mirror. It is reflected and the intensity of the light increases.

In this case, if the reference pattern of the matched filter is optically converted into polar coordinates and written,
The pattern light to be recognized is polar coordinate-transformed, then Fourier-transformed, and then irradiated onto a matched filter.

Furthermore, if the reference pattern of the matched filter is optically polar coordinate transformed and logarithmically transformed, the recognized pattern light is polar coordinate transformed, logarithmically transformed, Fourier transformed, and irradiated onto the matched filter. .

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an optical pattern recognition device, and FIG. 2 is a block diagram of a matched filter producing device used in the same device.

First, the matched filter creation device will be explained. Below the CCD camera 20 is a reference pattern 2.
1 is placed. An image output terminal of this CCD camera 20 is connected to a monitor television 22. A spatial light modulator 23 is arranged in front of the monitor television 22 so that an image displayed on the monitor television 22 is written into the spatial light modulator 23.

On the other hand, a laser oscillator 24 is provided, and an enlarging collimator system 25, a polarizing beam splitter 26, and a reference light incident angle changing mechanism 27 are arranged on the optical path of the laser beam output from the laser oscillator 24. This reference light incident angle changing mechanism 27 irradiates the dry plate 28 with the incident laser light as a reference light, and has a function of changing the irradiation angle to the dry plate 28. Further, a mirror 29 is arranged in the branching direction of the polarizing beam splitter 26, and a Fourier transform lens 30 is arranged in the reflection direction of this mirror 29.

With this configuration, the CCD camera 20 images the reference pattern and outputs the image signal. This image signal is displayed on a monitor television 22, and this image is written into a spatial light modulator 23.

On the other hand, the beam diameter of the laser beam output from the laser oscillator 24 is expanded by the expanding collimator system 25 and sent to the polarizing beam splitter 26 . The polarizing beam splitter 26 splits the laser beam and sends one of the laser beams to the spatial light modulator 23 and sends the other laser beam to the reference beam incident angle changing mechanism 27 . The reference light incident angle changing mechanism 27 irradiates the dry plate 28 with the incident laser light as a reference light, for example, in the incident direction R1.

At the same time, when the laser beam enters the spatial light modulator 23, the reference pattern written in the spatial light modulator 23 is called out, and this reference pattern light passes through the deflection beam splitter 26 and is reflected by the mirror 29. is Fourier transformed by the Fourier transform lens 30 and transferred to the dry plate 2.
8 is irradiated. As a result, a Fourier spectrum of the reference pattern is generated on the dry plate 28 and written on the dry plate 28. Here, the incident angle R2 of the reference light with respect to the dry plate 28 is
, R3, . . . a plurality of reference patterns are written on the dry plate 28, and this dry plate 28 becomes a matched filter. Next, the optical pattern recognition device of the present invention will be explained. Note that the same parts as in FIG. 2 are given the same reference numerals, and detailed explanation thereof will be omitted.

A half mirror 40 is disposed on the optical path of the deflection beam splitter 26 when viewed from the spatial light modulator 23.
A Fourier transform lens 30 is arranged on the reflected optical path of this half mirror 40. Also, matched filter 28
An inverse Fourier transform lens 41 is arranged in the direction in which the diffracted light is generated.

The direction in which the diffracted light of the matched filter 28 is generated, that is, the optical path of the inverse Fourier transform lens 41 as seen from the matched filter 28 and the matched filter 28
Phase conjugate mirrors 42 and 43 are arranged on the optical paths of the Fourier transform lens 30 and the half mirror 40, respectively, when viewed from above.

Further, a half mirror 44 is arranged on the optical path of the inverse Fourier transform lens 41 and the phase conjugate mirror 42, and a CCD camera 4 is arranged on the reflected optical path of this half mirror 44.
5 is placed. The image signal output from this CCD camera 45 is sent to a recognition processing device 46. Next, the operation of the apparatus configured as described above will be explained.

The CCD camera 20 images the pattern to be recognized 47 and outputs the image signal. This image signal is displayed on a monitor television 22, and this image is written into a spatial light modulator 23.

On the other hand, the beam diameter of the laser beam output from the laser oscillator 24 is expanded by the expanding collimator system 25 and sent to the polarizing beam splitter 26 . This polarizing beam splitter 26 splits the laser beam and sends one of the laser beams to the spatial light modulator 23 . When a laser beam enters the spatial light modulator 23, the reference pattern written in the spatial light modulator 23 is called out, and this reference pattern light is transmitted through the deflection beam splitter 26, reflected by the half mirror 40, and then The light is Fourier transformed by the transformation lens 30 and then irradiated onto the matched filter 28 . This irradiation generates diffracted light in the direction of the incident angle of the reference light when writing the reference pattern with the highest degree of correlation, for example, R1.

By the way, if the pattern to be recognized 47 is chipped or faded, the light intensity of the diffracted light will be lower than in the case of a normal pattern to be recognized 47. Here, the diffracted light is reflected by the phase conjugate mirror 42 to generate reflected diffracted light that is conjugate with the incident diffracted light, and this reflected diffracted light is transmitted through the inverse Fourier transform lens 41 and the matched filter 28, and then through the Fourier transform lens. 30, the light passes through the half mirror 40 and enters the other phase conjugate mirror 43. Similar to the phase conjugate mirror 42, this phase conjugate mirror 43 reflects diffracted light that is conjugate with the incident diffracted light, so this diffracted light is transmitted again along the same optical path and enters the phase conjugate mirror 42 again. In this way, the diffracted light reciprocates between the phase conjugate mirrors 42 and 43. The intensity of the diffracted light gradually increases as the diffracted light travels back and forth between the phase conjugate mirrors 42 and 43. As a result, even if the recognized pattern 47 is chipped or faded, the pattern reproduced by the matched filter 28 has a clear outline.

In this way, the intensity of the diffracted light transmitted through the half mirror 44 becomes high, and the transmission position of this diffracted light becomes clear. The position of this diffracted light changes depending on the recognized pattern incident on the matched filter 28, and
5 images the diffracted light that changes in position and outputs the image signal. When the recognition processing device 46 determines from the input image signal that the intensity of the diffracted light has exceeded a predetermined value, it recognizes the pattern to be recognized from the position of the diffracted light at this time.

As described above, in the first embodiment, the diffracted light generated when the recognized pattern light is irradiated onto the matched filter 28 on which the reference pattern is written is reflected between the phase conjugate mirrors 42 and 43. Since the light intensity is increased, the pattern can be accurately recognized even if the pattern to be recognized is chipped or faded. In addition, this light-based recognition allows for pattern recognition much faster than the pattern matching method that uses image processing.

Next, a second embodiment of the present invention will be described with reference to a block diagram of an optical pattern recognition apparatus shown in FIG. 3 and a block diagram of a matched filter producing apparatus used in the same apparatus shown in FIG. Note that the same parts as in FIGS. 1 and 2 are given the same reference numerals, and detailed explanation thereof will be omitted.

First, the matched filter creation device will be explained. A logarithmic conversion device 50 is connected to an image output terminal of the CCD camera 20. This logarithmic conversion device 50 has a function of logarithmically converting the reference pattern imaged by the CCD camera 20. For example, the reference pattern g(
x, y) is logarithmically transformed to obtain g'(x', y'). Here, x'=logx, y'=logy.

With this configuration, the CCD camera 20 images the reference pattern and outputs an image signal thereof, and this image signal is logarithmically converted by the logarithmic conversion device 50 and sent to the monitor television 22. This monitor television 22 displays a logarithmically transformed image, and this image is written into the spatial light modulator 23.

Hereinafter, as in the first embodiment, when a laser beam enters the spatial light modulator 23, the reference pattern written in the spatial light modulator 23 is called out by the laser beam incidence, and this reference pattern light is is Fourier-transformed by the Fourier-transform lens 30 and irradiated onto the dry plate 28 . At the same time, the reference light incident angle changing mechanism 27 irradiates the dry plate 28 with the incident laser light as a reference light, for example, in the incident direction R1. As a result, diffracted light corresponding to the reference pattern is generated on the dry plate 28 and written on the dry plate 28.
is a matched filter. Next, the optical pattern recognition device will be explained.

A logarithmic conversion device 50 is connected to the image output terminal of the CCD camera 20. Also, CCD camera 45
A recognition processing device 51 is connected to the image output terminal of. When this recognition processing device 51 determines from the input image signal that the intensity of the diffracted light has exceeded a predetermined value, it recognizes the pattern to be recognized from the position of the diffracted light at this time, and also determines the position of the diffracted light. It has a function of sending it to the monitor television 52. In this case, the monitor television 52
The size deviation of the recognized pattern with respect to the reference pattern is displayed as a positional deviation. That is, if the recognized pattern is shifted by a times in the x direction and b times in the y direction with respect to the reference pattern, the diffracted light will be displayed at the position (loga, logb) in the displayed xy logarithmic coordinates. Next, the operation of the apparatus configured as described above will be explained.

The CCD camera 20 images the pattern to be recognized 47, and the image is logarithmically converted by the logarithmic conversion device 50, displayed on the monitor television 22, and written into the spatial light modulator 23.

On the other hand, when the laser beam enters the spatial light modulator 23, the reference pattern written in the spatial light modulator 23 is called out, and this reference pattern light is Fourier transformed by the Fourier transform lens 30 to produce a matched pattern. The filter 28 is irradiated with light. This irradiation generates diffracted light in the direction of the incident angle of the reference light when writing the reference pattern with the highest degree of correlation, for example, R1.

Here, as in the first embodiment, the diffracted light reciprocates between the phase conjugate mirrors 42 and 43, and the intensity of the diffracted light gradually increases due to this reciprocation. As a result, even if the recognized pattern 47 is chipped or faded, it can still be matched.
The pattern reproduced by the filter 28 has a clear outline.

[0036] Thus, the position of the diffracted light reflected by the half mirror 44 changes depending on the recognized pattern incident on the matched filter 28, and the CCD camera 45 images the diffracted light whose position changes and generates the image signal. Output. When the recognition processing device 51 determines from the input image signal that the intensity of the diffracted light has exceeded a predetermined value, it recognizes the pattern to be recognized from the position of the diffracted light at this time. Further, the recognition processing device 51 recognizes the pattern to be recognized 47.
The size deviation with respect to the reference pattern 21 is displayed on the monitor television 52 as a positional deviation. 5 shows the case where the size of the recognized pattern 47 and the reference pattern 21 is the same, and FIG. 6 shows the case where the size of the recognized pattern 47 with respect to the reference pattern 21 is shifted by a times in the x direction and b times in the y direction This is the case.

As described above, according to the second embodiment, the same effects as those of the first embodiment can be achieved, and the size of the recognized pattern 47 relative to the reference pattern 21 is different in the x and y directions. Pattern recognition is possible.

Next, a third embodiment of the present invention will be described with reference to a block diagram of an optical pattern recognition apparatus shown in FIG. 7 and a block diagram of a matched filter producing apparatus used in the same apparatus shown in FIG. Note that the same parts as in FIGS. 1 and 2 are given the same reference numerals, and detailed explanation thereof will be omitted.

First, the matched filter creation device will be explained. A polar coordinate logarithmic conversion device 60 is connected to the image output terminal of the CCD camera 20. This polar coordinate logarithmic transformation device 60 has a function of polar coordinate transformation and then logarithmic transformation of the reference pattern imaged by the CCD camera 20. For example, g'(r, θ) is obtained by converting the reference pattern g(x, y). Here, r= log(x2 +y2)1/2, θ= ta
n-1(y/x).

With such a configuration, an image subjected to polar coordinate logarithm transformation is written to the spatial light modulator 23. Thereafter, as in the first embodiment, the reference pattern written on the spatial light modulator 23 is called by the incidence of laser light, and this reference pattern light is Fourier transformed by the Fourier transform lens 30 and irradiated onto the dry plate 28. . At the same time, the reference light irradiates the dry plate 28 in the incident direction R1, for example. As a result, a reference pattern is written on the dry plate 28, and the dry plate 28 becomes a matched filter. Next, the optical pattern recognition device will be explained.

A recognition processing device 61 is connected to the image output terminal of the CCD camera 45. This recognition processing device 61
When determining from the input image signal that the intensity of the diffracted light has exceeded a predetermined value, it recognizes the pattern of the recognized pattern 47 from the position of the diffracted light at this time, and monitors the position of the diffracted light. It has a function to send to. In this case, the degree of similarity of the recognized pattern 47 to the reference pattern 21 and the inclination θ are displayed on the monitor television 52 as a positional deviation. That is, if the recognized pattern 47 is shifted by c times in both the x and y directions with respect to the reference pattern 21 and has an inclination θ, then (logc
, tan-1(y/x)). Next, the operation of the apparatus configured as described above will be explained.

The pattern to be recognized 47 imaged by the CCD camera 20 is polar-logarithmically transformed by the polar-logarithm converter 60, displayed on the monitor television 22, and written into the spatial light modulator 23.

On the other hand, similarly to the above, the reference pattern written in the spatial light modulator 23 is called out by the incidence of laser light, and this reference pattern light is transmitted to the Fourier transform lens 30.
The signal is Fourier transformed and applied to the matched filter 28. This irradiation generates diffracted light in the direction of the incident angle of the reference light when writing the reference pattern with the highest degree of correlation, for example in the direction of R1.

Here, the diffracted light passes through each phase conjugate mirror 42,
43, and the intensity of the diffracted light gradually increases due to this reciprocation. As a result, even if the recognized pattern 47 is chipped or faded, the pattern reproduced by the matched filter 28 has a clear outline.

This diffracted light is imaged by the CCD camera 45, and the recognition processing device 61 recognizes the pattern to be recognized 47 from the input image signal. In addition, the recognition processing device 51
displays on the monitor television 62 the deviation and inclination θ of the recognized pattern with respect to the reference pattern in the x and y directions. 9 shows a case where the size of the recognized pattern 47 and the reference pattern 21 are the same and there is no inclination, and FIG. 10 shows the case where the size of the recognized pattern 47 with respect to the reference pattern 21 is c times in both the This is the case where θ occurs.

As described above, according to the third embodiment, the same effects as those of the first embodiment can be achieved, and the similarity and inclination of the recognized pattern 47 to the reference pattern 21 can be recognized.

Next, a fourth embodiment of the present invention will be described. In this embodiment, a polar coordinate conversion device for performing polar coordinate conversion is connected to the image output terminal of the CCD camera 20. It is clear that by connecting this polar coordinate conversion device, the inclination of the recognized pattern 47 with respect to the reference pattern 21 can be recognized.

It should be noted that the present invention is not limited to the above embodiments, and may be modified without changing the gist thereof. For example, the spatial light modulator may be one that obtains a coherent image, such as an MSLM or a liquid crystal light valve, and the phase conjugate mirror may be one that is a nonlinear crystal such as BSO or KTP.

[0049]

As described in detail above, according to the present invention, it is possible to provide an optical pattern recognition device that can accurately recognize a pattern even if the pattern to be recognized is chipped or faded.

[Brief explanation of drawings]

FIG. 1: A first optical pattern recognition device according to the present invention.
FIG. 2 is a configuration diagram showing an example.

FIG. 2 is a configuration diagram of a matched filter creation device used in the same device.

FIG. 3: A second optical pattern recognition device according to the present invention.
FIG. 2 is a configuration diagram showing an example.

FIG. 4 is a configuration diagram of a matched filter creation device used in the same device.

FIG. 5 is a diagram showing the position of diffracted light displayed on the device.

FIG. 6 is a diagram showing the position of diffracted light displayed on the device.

FIG. 7: Third part of the optical pattern recognition device according to the present invention.
FIG. 2 is a configuration diagram showing an example.

FIG. 8 is a configuration diagram of a matched filter creation device used in the same device.

FIG. 9 is a diagram showing the position of diffracted light displayed on the device.

FIG. 10 is a diagram showing the position of diffracted light displayed on the device.

FIG. 11 is a configuration diagram of a conventional matched filter creation device.

FIG. 12 is a configuration diagram of a conventional optical pattern recognition device.

[Explanation of symbols]

20, 45... CCD camera, 22... Monitor television, 23... Spatial light modulator, 24... Laser oscillator, 25... Enlargement collimator system, 26... Polarizing beam splitter, 28...
Matched filter, 30...Fourier transform lens, 40
, 44...half mirror, 41...inverse Fourier transform lens,
42, 43... Phase conjugate mirror, 46... Recognition processing device, 5
0...Logarithmic conversion device, 60...Polar coordinate logarithm conversion device.

Claims (4)

[Claims] Claim 1: Fourier-transforming the recognized pattern light and irradiating it onto a matched filter on which a reference pattern is written, and determining the correlation between the reference pattern and the recognized pattern from the diffracted light generated by the matched filter. An optical pattern recognition device, characterized in that each phase conjugate mirror is arranged optically opposite to each other on the optical path of the diffracted light generated by the matched filter and at a position with the matched filter interposed therebetween. Expression pattern recognition device. 2. A matched filter in which a reference pattern that has been optically logarithmically transformed is written;
An irradiation optical system that irradiates the filter, phase conjugate mirrors that are optically placed opposite each other on the optical path of the diffracted light generated by the matched filter and at a position with the matched filter interposed, and amplification by these phase conjugate mirrors. What is claimed is: 1. An optical pattern recognition apparatus comprising: recognition means for determining a correlation between the reference pattern and the recognized pattern from the diffracted light. 3. A matched filter in which a reference pattern that has been optically converted into polar coordinates is written; an irradiation optical system that performs polar coordinate conversion on the recognized pattern light and then Fourier transform it to irradiate the matched filter;・
On the optical path of the diffracted light generated in the filter and the matched
Each phase conjugate mirror is optically arranged opposite to each other at a position where a filter is interposed, and a recognition means for determining the correlation between the reference pattern and the recognized pattern from the diffracted light amplified by these phase conjugate mirrors. An optical pattern recognition device featuring: 4. A matched filter in which a reference pattern that has been optically polar coordinate transformed and logarithmically transformed is written;
an irradiation optical system that performs polar coordinate transformation, logarithmic transformation, Fourier transformation, and irradiation of the recognized pattern light to the matched filter; and a position on the optical path of the diffracted light generated in the matched filter and with the matched filter interposed therebetween. An optical system comprising: phase conjugate mirrors arranged optically opposite each other, and recognition means for determining the correlation between the reference pattern and the recognized pattern from the diffracted light amplified by the phase conjugate mirrors. Expression pattern recognition device.