JPH04240625A - Optical pattern recognizer - Google Patents

Abstract

PURPOSE:To attain correct recognition even when the intensity of correlation output light becomes irregular owing to aberrations of a lens, an irregularity in the light intensity of luminous flux, an irregularity in the transmissivity of a spatial light modulator, etc. CONSTITUTION:An image output means 1 outputs a pattern to be inspected and a reference pattern group with the same coherent light at the same time. Those patterns are transformed into a spatial light intensity distribution pattern by an optical Fourier transforming means 2. This light intensity pattern is detected by a two-dimensional photoelectric converting means 32 and converted into a two-dimensional projected light complex distribution by an image output means 3 correspondingly. This distribution is processed again by the Fourier transformation of an optical Fourier transforming means 4 to obtain the intensity of the correlation output light between the pattern to be inspected and a reference pattern and an optical detecting means 5 performs a recognizing process according to the light intensity. Consequently, the display positions of the reference pattern and pattern to be inspected are adjusted and the correlation output light intensity is easily corrected.

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 used in the field of optical information processing. That is, the present invention relates to an optical pattern recognition device for recognition associative processing, classification processing, and especially arithmetic processing of information processing in the field of optical measurement and image processing.

0002

2. Description of the Related Art In general, a conventional method for obtaining cross-correlation between a group of reference images and a test image is to create a Fourier transform hologram of the reference image by changing the direction of the reference light for each reference image. The first method is to create a hologram by taking a so-called multiple hologram and using it as a correlation filter.The first method is to record a joint Fourier transform image of the reference image group and the test image in the form of an intensity distribution, and then use coherent light to create a hologram. The second method is to read out the information in
10316, 58-21716) have been proposed.

However, the first method described above requires a hologram storage element, but with a photographic plate, which is a typical recording material, it takes time to develop the plate, and
Very complicated work is required to change the direction of the reference light for each reference image, and real-time processing is impossible.

[0004] On the other hand, in the second method described above, these drawbacks are solved, but the joint Fourier transform image is created by multiplexing each reference image and each reference image and the test image. Recording joint Fourier transform images with too many reference images for the dynamic range and resolution of the spatial modulator, resulting in interference fringes, will severely reduce the visibility of the interference fringes, effectively resulting in a large number of It is impossible to use it for recognition by comparing test images.

[Problem to be solved by the invention]

The present invention was made to solve the above-mentioned problems, and performs correlation calculation between a reference image group and a test image in real time without using any means such as holography.
As shown in FIG. 2, we have provided an optical identification device that can dramatically increase the number of reference image groups by using a feedback system. In the optical pattern recognition device having this configuration, a beam 12 emitted from a coherent light source 11 such as a semiconductor or a gas laser is transmitted to a beam expander 13.
The beam is converted into an appropriate diameter by the beam splitter 14, and divided into two optical paths by the beam splitter 14. Here, the spatial light modulator 15
The transmittance distribution can be spatially modulated by electrical signal input, and the most common example is a liquid crystal panel used as a liquid crystal television or computer display.

Furthermore, in this conventional recognition device, a test pattern and a reference pattern group are displayed on the spatial light modulator 15, as shown in FIG. That is, the test pattern T1
is the center of the display, and the test patterns R1, R2,
R3, R4, and R5 are simultaneously displayed at fixed display positions on the circumference centered on the test pattern T1 at equal intervals.

Next, the light beam 1 that has passed through the spatial light modulator 15
2 passes through the Fourier transform lens 21 and enters the screen 31 placed on the Fourier transform surface. On the screen 31, after passing through the spatial light modulator 15, a light intensity proportional to the square of the two-dimensional Fourier transform of the complex amplitude distribution is observed.

This light intensity distribution is detected by a two-dimensional photoelectric conversion element 32 such as a CCD, and the image is displayed as an electric signal on a spatial light modulator 35 through a video amplifier and a liquid crystal drive circuit 33. . Similarly to the spatial light modulator 15, the spatial light modulator 35 also has a function of modulating the complex amplitude of incident light. The incident light beam 36 to the spatial light modulator 35 is such that the light beam 12 emitted from the laser 11 is connected to the beam splitter.
It is divided by 14. That is, the light source of the image output means 1 and the light source of the image output means 3 are shared.

The light beam 36 emitted from the spatial light modulator 35 is
The light passes through the Fourier transform lens 41 and enters the screen 51 located at the Fourier transform plane with respect to the spatial light modulator 35 . Here, on the screen 51, a peak of the correlation output light intensity (hereinafter referred to as a correlation peak) representing the degree of cross-correlation between the test pattern and each reference pattern is shown. appear.

Finally, the correlation peak is read by a two-dimensional photoelectric conversion element 52 and sent as an electrical signal to an image processing and liquid crystal driving circuit 53. Then, the obtained correlation output light intensity is normalized, and the light transmittance with respect to the reference pattern on the spatial light modulator 15 is determined according to the normalized ratio. That is, if the second strongest correlation output light intensity is normalized to the strongest correlation output light intensity among the obtained correlation output light intensities and is 0.5, then the correlation output light intensity is This means that the light transmittance on the spatial light modulation 15 for the reference pattern, which was the second highest, is set to 50% of the transmittance of the reference pattern, which has the highest correlation output light intensity.

Furthermore, the transmittances of other reference patterns are determined in the same manner. Then, by repeating the operations up to this point, the final result is the one that is equivalent to the test pattern among the reference patterns, that is, the finally read correlation after repeating the above operations. Among the output light intensities, the one with the strongest correlated output light intensity is recognized.

However, in the optical pattern recognition device as described above, the influence of aberrations caused by the lens, the influence of non-uniformity of the light intensity of the light beam, the non-uniformity of the transmittance of the spatial light modulator and the dynamic Due to reasons such as a lack of microwaves,
For example, if one test pattern is simultaneously displayed at different positions on the concentric circle of the test pattern on the spatial light modulator 15, the obtained patterns may be different even though they are the same pattern. A problem arises in that the intensity of the correlated output light varies depending on the position where each pattern is displayed on the spatial light modulator 15, which is the non-uniformity of the intensity of the correlated output light.

Furthermore, the display area of the reference pattern displayed on the spatial light modulator 15 also causes non-uniformity in the intensity of the correlated output light. In other words, the correlation output light intensity between the reference pattern and the test pattern that transmits a large amount of light on the spatial light modulator 15 is higher than that of the reference pattern that transmits a smaller amount of light on the spatial light modulator 15. This means that the correlation output light intensity between the pattern and the test pattern is greater than the correlation output light intensity between the pattern and the test pattern. Furthermore, as the number of reference patterns increases, the interference fringes formed on the screen 31 overlap, making it impossible to obtain a true correlated output light intensity. That is, non-uniformity of correlated output light intensity occurs.

The present invention has been made in order to solve the above-mentioned problems. Correct recognition may not be possible even if non-uniformity of the correlated output light intensity occurs due to reasons such as lack of quality or dynamic range, the influence of the display area of the reference pattern, or the influence of an increase in the number of reference patterns. The object of the present invention is to provide an optical pattern recognition device that uses the following methods.

[0015]

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned technical problem. a first image output means (for example, 1 in FIG. 1) that simultaneously displays a group of patterns and simultaneously outputs the displayed test pattern and the reference pattern group using coherent light; A first optical transformer that optically Fourier transforms the test pattern and the reference pattern group that are simultaneously output with the coherent light to obtain a spatial light intensity distribution pattern. Fourier transform means (for example, Fig.
2), the spatial light intensity distribution pattern obtained by the first optical Fourier transform means is detected by a first two-dimensional photoelectric conversion element, and the detected spatial intensity distribution is a second image output means (for example, 3 in FIG. 1) capable of changing the coherent two-dimensional complex distribution of emitted light according to the pattern; The two-dimensional complex amplitude distribution of the output light is optically Fourier transformed, and the correlation output light intensity between the test pattern and each reference pattern for the reference pattern group is obtained. an optical Fourier transform means (for example, 4 in FIG. 1) and the test pattern obtained by the second optical Fourier transform means;
The correlation output light intensity between the pattern and each reference pattern for the reference pattern group is detected by the second two-dimensional photoelectric conversion element (for example, 51 in FIG. 1), and the detected correlation is In an optical pattern recognition device comprising a light detection means (for example, 5 in FIG. 1) that performs recognition processing according to the intensity of output light intensity, each reference displayed on the first image output means The display position of the pattern (e.g., R1 in FIG. 4) is set to the test pattern (e.g., R1 in FIG. For a reference pattern (for example, R4 in FIG. 3) that is desired to be closer to T1) in FIG. The present invention provides the optical pattern recognition device. It is preferable to have feedback means for inputting a modulation signal corresponding to the correlation output light intensity obtained by the optical pattern recognition device to the first spatial light modulator. Further, the display position control means is operated under computer control, and controls the display position of each reference pattern displayed on the first image output means, depending on the reference pattern whose correlation output light intensity is desired to be increased. For the reference pattern, move it closer to the test pattern, and for the reference pattern you want to weaken the correlation output light intensity, change it so that it is farther away from the test pattern. It is preferable to have a display position control means for correcting. Furthermore, the second image output means at least
The complex amplitude distribution of the incident light beam is modulated based on a coherent light source and a signal from a first two-dimensional photoelectric conversion element that receives the output light from the first optical Fourier transform means. and a second spatial light modulator that outputs an output signal. The second image output means includes at least a coherent light source and the first optical frame.
The optical characteristics of the optical characteristics change two-dimensionally or three-dimensionally depending on the intensity distribution of the output light from the Rie transformer.
A spatial light modulator consisting essentially of a spatial light modulator is preferred.

[0020]

[Operation] According to the above configuration of the present invention, the influence of aberration caused by the lens, the influence of non-uniformity of the light intensity of the light beam, the non-uniformity of the transmittance of the spatial light modulator, the lack of dynamic range, and the reference pattern Even if non-uniformity occurs due to the correlated output light intensity due to the influence of the display area of the reference pattern or the influence of an increase in the number of reference patterns, the display position of the reference pattern on the spatial light modulator and It is possible to individually change the distance to the test pattern display position and correct each correlation output light intensity. Therefore, by using such a correction method and correcting the non-uniformity of the correlated output light intensity in advance, it is possible to improve the recognition rate in the optical pattern recognition apparatus. Furthermore, since the display position control means is computer controlled, it is possible to easily and flexibly correct the correlation output light intensity.

Next, the optical pattern recognition device of the present invention will be explained in detail with reference to examples, but the present invention is not limited thereto.

[0022]

[Embodiment 1] FIG. 1 shows one of the optical correlation processing methods of the present invention.
1 is a schematic block diagram illustrating the functionality of an example optical pattern recognition device (i.e. incorporating a position control device); FIG.

As can be seen from the optical layout diagram of FIG. 1, the overall configuration is almost the same as that of the optical pattern recognition device of FIG. 2. The difference is that display position control means 6 is placed in front of spatial light modulator 15. However, the display position control means 6 is controlled by a computer.

FIG. 3 is an explanatory diagram showing a conventional display state. On the other hand, A, B, and C in FIG. 4 are explanatory diagrams showing display states by the optical pattern recognition device of the present invention, in which A is a standard display state and R1 is a standard display state. −
It is. Further, B indicates the display state during the correction process according to the present invention, and C indicates the display state after the correction process. The method of correcting the correlated output light intensity according to the present invention changes the display position of each pattern of the test pattern group (T1 etc.) on the spatial light modulator 15 so that the correlated output light intensity is uniform. The correction is made so that Each reference pattern displayed on the spatial light modulator 15 and each reference pattern
The display position of the test pattern (on the circumference centered on the test pattern) and the display position of the test pattern and the test pattern are already the same as the test pattern and reference in A of FIG. Assume that the display positions of the pattern group have been determined as shown in the explanatory diagram showing the display positions of the pattern group. Further, the display state of A in FIG. 4 is assumed to be the standard display position.

In A of FIG. 4, R1 to R5 represent each reference pattern, and A1, A2, A3, A4 in parentheses
, A5 represents the display position of each reference pattern, and T1 represents the test pattern. (The display position of the test pattern is fixed. Also, the number of reference patterns is not fixed at five patterns). However, the test pattern and reference pattern on the spatial light modulator 15 shown in FIG. 4A
In the current display method, the correlated output light intensity is non-uniform. Therefore, according to the optical pattern recognition apparatus of the present invention, the display position of the reference pattern is moved in advance to correct the correlation output light intensity.

The procedure for correcting the correlation output light intensity is to first select one pattern from a group of reference patterns to serve as a reference pattern. Here, the selected pattern R1 is used as a reference pattern. Next, FIG. 4B is an explanatory diagram showing the display positions of the test pattern and the reference pattern group. As shown there,
First, a reference pattern (R1) is placed at the display position A1 of A in FIG.
is displayed, and other reference patterns are not displayed. In addition, the reference pattern (R1) is also displayed at the display position of T1 (display position of the test pattern), the correlation output light intensity between R1 is detected, and the correlation output light intensity is set as the reference value. Set to 1.

Next, reference pattern R2 is displayed at display position A2 in A of FIG. 4, and other reference patterns, including R1 that was displayed at display position A1, are not displayed. shall be. In addition, R2 is displayed at the display position of T1, and R2 is displayed at the display position of T1.
The correlation output light intensity between the two comrades is detected. And R2
So that the correlated output light intensity of the comrades is equal to the reference value 1,
If you want to increase the correlation output light intensity, use the reference pattern R2.
If you want to reduce the correlation output light intensity by moving the display position of reference pattern R2 closer to the test pattern display position, move the display position of reference pattern R2 to a position farther from the test pattern display position. The control means 6 moves the reference pattern R2 at the display position A2 to correct the display position.

The corrected reference pattern display position is then stored in the memory of the computer. below,
Regarding the reference patterns R3 to R5, the reference pattern display positions are corrected in the same manner as described above, and the finally obtained corrected reference pattern display positions are fixed. The position of the correlation peak appearing on the screen 51 changes as the display position of the reference pattern is moved, and the position of the display of the reference pattern is changed from that of the test pattern. - When moving to a position close to the optical axis, the correlated output light intensity appears to be strengthened at a position close to the optical axis by the amount that the reference pattern display position is changed, and the correlation output light intensity appears at a position close to the optical axis, Inspection pattern
When moving to a position far from the optical axis, the correlated output light intensity appears weakened at a position farther from the optical axis by an amount corresponding to the change in the display position of the reference pattern.

Here, if the correlation output light intensity of R2 is smaller than the reference value 1, the correlation output light intensity of R3 is equal to the reference value 1, and the correlation output light intensity of R4 and R5 and the reference value are larger than 1. After the display positions of all the reference patterns have been corrected, the display state of the test pattern and the reference pattern on the spatial light modulator 15 is as shown in FIG. 4C. become. In C of Figure 4, R1, R2, R3, R4, R
5 shows the same reference pattern as A in FIG.
represents the test pattern, and the display position of the test pattern is
This is exactly the same as the display position of T1 in A of FIG.

As shown in FIG. 4C, in order to strengthen the correlation output light intensity of R2, the display position of R2 is moved closer to the test pattern, and the correlation output light intensity of R3 is not changed.
It can be seen that in No. 3, the display positions of R4 and R5 are moved away from the test pattern in order to weaken the respective correlation output light intensities of R4 and R5 without changing the display positions. The method of correcting the correlation output light intensity explained in the above embodiments is suitable for pattern recognition when there are few reference patterns, since the correction is performed for each reference pattern. In the above description, the spatial light modulator 35 is an electrically addressed spatial light modulator that modulates and outputs the complex amplitude distribution of the incident light flux based on the electrical signal from the two-dimensional photoelectric conversion element 32. However, it is also possible to use an optically addressed spatial light modulator whose optical characteristics change two-dimensionally or three-dimensionally depending on the intensity distribution of the output light from the optical Fourier transform means 2. It is possible.

[0031]

Embodiment 2 FIG. 6 is a block diagram of an optical pattern recognition apparatus of the present invention which incorporates an optically addressed spatial light modulator. In FIG. 6, from the coherent light source 11,
The emitted light beam 12 follows the same optical path as in FIG. 1 until it passes through the spatial light modulator 15. However, in FIG. 6, the beam splitter 1 is included in the optical path up to the spatial light modulator 15.
4 is not present, the amount of light beam 12 is only doubled, and its behavior at the spatial light modulator 15 remains unchanged. That is,
The light beam 12 that has passed through the spatial light modulator 15 passes through the Fourier transform lens 21 and undergoes Fourier transform, and is then transformed into an optically addressed spatial light modulator 37 (hereinafter referred to as spatial light modulator) installed on the Fourier transform surface. (hereinafter referred to as an optical modulator 37).

Next, the light beam 12' emitted from the laser 11'
passes through the beam expander 13' and enters the polarizing beam splitter 38. Polarizing beam splitter 38
Then, only the S-polarized light component is reflected, and the P-polarized light component is transmitted. Subsequently, the light beam 16 consisting of the S-polarized component enters the spatial light modulator 37. Here, the spatial light modulator 37 is a reflective liquid crystal light valve as shown in FIG. This reflective liquid crystal light valve has a photoconductive layer 77 and a dielectric mirror 75 arranged between the liquid crystal light valve sandwiched between transparent electrodes 72 and 78. is sufficiently small compared to the interval between interference fringes appearing on the Fourier transform surface.

The dielectric mirror 75 also has a photoconductive layer 77.
It is arranged on the liquid crystal layer side (on the right side in the figure), and this is the direction in which the readout light is incident. At this time, when a voltage is applied between the transparent electrodes on both sides (i.e., 72 and 78) and the writing light A is irradiated, the photoconductive layer is A voltage drop occurs at 77, and the voltage applied to the liquid crystal of each part changes,
The polarization plane of the incident readout light B is rotated. Therefore, the light beam 16 undergoes rotation of the plane of polarization according to the writing light A that is incident on the spatial light modulator 37, and the reflected light is rotated by the polarizing beam splitter according to the intensity distribution of the writing light A. Pass 38. However, at the beginning of the process, by setting the bias potential in advance and injecting the bias light, the light flux 16 that passes through the polarizing beam splitter 38 has a uniform amount of light over the entire range of light flux, and then passes through the Fourier transform lens 41. incident.

Further, the Fourier transform lens 41 of the light beam 16
The process after the light beam 12 is incident on the Fourier transform lens 41 in FIG. 1 is the same as that of the light beam 12 in FIG. As described above, with the configuration shown in FIG. 6, it is possible to construct an optical pattern recognition device incorporating an optically addressed spatial light modulator.

[0035]

Embodiment 3 Next, a method of correcting the correlation output light intensity in the pattern recognition apparatus shown in FIG. 1 will be explained. Further, the method for correcting the correlation output light intensity explained here consists of three steps, from the first correction to the third correction, and the first correction will be explained first. In the first stage correction process, when the same reference pattern is displayed at the display position of all the reference patterns in the spatial light modulator 15, the correlated output light intensity of each reference pattern is This is a correction to make it uniform. Similar to that shown in Example 1, in A of FIG.
to R5 represent each reference pattern, and A in parentheses
1, A2, A3, A4, and A5 represent the display positions of each reference pattern, and T1 represents the test pattern.

According to the present invention, A, B, C, and D in FIG.
FIG. 7 is an explanatory diagram showing a display state when correction processing is performed in the first to third stages. A indicates the display state before the first stage correction process, B indicates the display state after the first stage correction process, C indicates the display state during the second stage correction process,
D shows the display state after the third stage of correction processing. According to the present invention, first, a reference pattern is selected from a group of reference patterns.
The reference pattern R1 is selected as the reference pattern R1 as shown in the explanatory diagram A of FIG. 5 showing the display state before the first correction. In addition, the display position of each reference pattern and the test pattern at the standard display position.
displayed in the displayed position. Then, the correlation output light intensity (reference value 2) between R1 at the display position of the actual reference pattern (that is, A1) and R1 at the display position of the test pattern
The other A2, A3, A4, A5 so that it is equal to
When the reference pattern (R1) displayed in Sometimes, the display position is moved farther than the reference pattern (R1) located at the display position of the test pattern.

[0037] Here, suppose that the correlation output light intensity of the reference pattern (R1) at the position A2 is greater than the reference value 2,
If the correlation output light intensity of R1 at positions A3 and A5 is smaller than reference value 2, and the correlation output light intensity of R1 at position A4 is equal to reference value 2, then R1 at the reference pattern display position is displayed. The result of moving the position is the display state after the first stage correction shown in FIG. 5B. In FIG. 5B, the distances between the reference pattern (R1) moved from each of the display positions A1 to A5 and the reference pattern (R1) at the test pattern display position are expressed as D1, D2, and D2, respectively. D3, D
4. Set it as D5. Also, D1, D2, D3, D4, D5
The distance is stored in the computer's memory.

Next, the second stage correction processing will be explained. Second
The stage correction process is to correct the non-uniformity of the correlation output light intensity due to the type of reference pattern, and as shown in FIG. 5C, the display position where the reference pattern is actually displayed (i.e. R1 is displayed at the standard display position A1), R1 is also displayed at the display position of the test pattern, the correlation output light intensity of R1 is measured, and the value is set as the reference value 3.

Next, R2 is similarly displayed at the display position of A1, R2 is also displayed at the display position of the test pattern, and R2 is displayed at the display position of A1.
A so that the correlation output light intensity of A becomes equal to the reference value 3
If you want to strengthen the correlation output light intensity of R2 at the display position of A1, move the display position of R2 in A1 to a position close to R2 at the test pattern display position, and if you want to weaken the correlation output light intensity. , the display position control means 6 moves the display position of R2 located at A1 to a position far from R2 located at the test pattern display position.
The distance between the R2 comrades at the end of the movement is normalized by the distance between the reference pattern display position and the test pattern display position, and is stored in the computer memory.
to be memorized.

Regarding the other patterns (R3, R4, R5), the test pattern of each reference pattern is determined in the same manner as above.
The distance from the pattern display position is normalized by the distance between the reference pattern display position and the test pattern display position. Then, R1 to R5 are standardized, and the obtained values are respectively P1, P2, P3, P4, and P5. However, R
Since it is normalized with respect to 1, P1=1.

Next, the third stage correction processing will be explained. The third stage correction process is the final correction, and is based on D1 to D5 that have been stored in the computer memory so far.
, and for P1 to P5, D1*P1, D2*P
2. Each distance represented by D3*P3, D4*P4, D5*P5 (* indicates integration) is the distance from the final test pattern display position to the reference pattern display position. It is.

[0042] If D1=D4=1, D2=1.2, D
3=D5=0.8 Also, P1=1, P2=0.5, P3=1.5, P4=
1.2, and P5=1.5, then D1*P1=
1*1=1 D2*P2=1.2*0.5=0.6 D3*P3=0.8*1.5=1.2 D4*P4=1*1.2=1.2 D5* P5=0.8*1.5=1.2, as shown in FIG. 5C. In this way, the reference pattern display position obtained is fixed.

By the way, in this embodiment, each reference pattern
The display position order of the buttons is determined before the first stage correction process, that is, clockwise: R1, R2, R3, R4, R5.
The order is Each reference pattern after the third stage correction process
The display position order of the buttons is also the same as before the first stage correction, but the correction method shown in this embodiment is not limited to this.

Since the above-mentioned first stage correction processing and second stage correction processing are operationally independent, the display position order of each reference pattern after the third stage correction processing is completed is as follows. , 1st
It is possible to make the display position order different from the display position order before the column correction. For example, the display position of D1*P2 (i.e.,
This means that it is possible to display R2 at a display position corrected with respect to the display position of A1. In the first stage of correction processing, correction is made for non-uniformity of the correlation output light intensity due to the influence of lens aberrations, non-uniformity of the light intensity of the light flux, etc., and the display position of each corrected reference pattern is The correction is determined completely independently of the display position order of each reference pattern, and the same correction result is always obtained.

In the second stage of correction processing, each reference pattern is normalized using a standard pattern so as to correct the non-uniformity of the correlated output light intensity due to the display area of each reference pattern. The values obtained by normalization are also determined completely independently of the display position order of each reference pattern, and as long as the reference pattern remains the same and the reference pattern is not changed, the same correction result will always be obtained. obtain.

In the third stage correction process, which reference pattern is selected in order to obtain the final distance from the test pattern by integrating the values obtained in the first and second stage correction processes. But,
No matter where the reference pattern was displayed, distances were obtained that were compared to the respective values obtained in the first and second stage correction processes. In the correction method of this embodiment, for the reasons mentioned above, the display position order of each reference pattern after the third stage correction process is different from the display position order before the first stage correction. It is possible to do so. That is, in the correction process in this embodiment, when the same pattern (reference pattern) is displayed at the standard display position, all correlation output light intensities are corrected to be uniform, and the pattern is Since the non-uniformity of the correlation output light intensity due to the type of pattern is also corrected, it is suitable for pattern recognition when there are a large number of reference patterns.

In this embodiment, the spatial light modulator 35 can be an optically addressed spatial light modulator as described in the first embodiment. Further, FIG. 7 is a conceptual diagram illustrating the configuration of a reflective liquid crystal light valve. The reflective liquid crystal light valve 70 is composed of a large number of divided pixels 70a, which include an antireflection film 79, a glass substrate 71, a transparent electrode 72, a spacer 73, and a dielectric mirror 75.
, a photoconductive layer 77, a transparent electrode 78, a glass substrate 76, and an antireflection film 79 are laminated in this order. This configuration allows writing with write light A and reading with read light B. Next, by changing the display position of the reference pattern on the spatial light modulator 15,
It will be explained whether the optical correlation intensity is corrected. Assume that the test pattern on the spatial light modulator 15 is displayed on the optical axis, and the reference pattern is displayed at a distance a distance a from the test pattern. These patterns are
It is irradiated with coherent parallel light, and all of the light is converged to a focal point after passing through the Fourier transform lens 21. However, each light that has passed through the test pattern and the reference pattern is diffracted, and after passing through the Fourier transform lens 21, the light is reflected near the focal point.
Creates Rie-transformed images and forms interference fringes between them.

The light from the test pattern and the reference pattern is
Since it is considered that the light consists of a collection of point light sources, 2
Considering the formation of interference fringes between two point light sources, coherent light of wavelength λ is generated by two point light sources spaced apart by a distance a distance r from the midpoint of the two point light sources. The interval △W between interference fringes formed on distant screen surfaces is △W
=λr/a (1) It can be expressed as follows. As can be seen from equation (1), the interval ΔW between the interference fringes is inversely proportional to the distance a between the two point light sources. That is, by increasing the distance between two point light sources, the interval between interference fringes can be increased. As described above, the interference fringes formed on the screen 31 in FIG.

Next, this interference fringe pattern is subjected to Fourier transformation by a Fourier transformation lens 41. Furthermore, as a result of the light passing through the interference fringe pattern being diffracted and Fourier transformed, a cross-correlation pattern appears near the back focal point of the Fourier transform lens. When the interval between interference fringes is a' and the wavelength of light is λ', the distance △ between the optical axis and the cross-correlation pattern appearing on the screen surface that is a distance r' from the surface where the interference fringes are formed is W' can be expressed as ΔW'=λ'r'/a'.../(2). That is, if the interval between the interference fringes is increased, the distance between the cross-correlation and the optical axis will become smaller, and if the interference fringes are made smaller, the distance will become larger.

Regarding diffraction, according to the Fresnel-Kirchhoff diffraction formula, when parallel light enters an aperture perpendicularly and is diffracted, the angle θ is made with respect to the normal to the aperture surface. It can be seen that the light intensity due to the diffracted waves in this direction is proportional to the square of (1+cos θ). However, -π/2≦θ≦π/2. That is, it can be said that the light intensity due to the diffracted waves becomes stronger closer to the optical axis.

Furthermore, since the resolution of the spatial light modulator is not infinite, if the spatial frequency of the interference fringes to be expressed exceeds its capability, the interference fringes will not be expressed and the correlation output light intensity will be reduced. This weakening is also one of the reasons why the correlation output light intensity weakens when the distance between the test pattern and the reference pattern is increased.

To summarize the above, when the interval between the test pattern and the reference pattern on the spatial light modulator 15 is made small, the interference fringes formed on the screen 31 by equation (1) are The spacing becomes larger and the screen 31
A cross-correlation pattern obtained by Fourier transforming the interference fringes formed above appears at a position close to the optical axis according to equation (2). Further, the cross-correlation pattern is formed by diffracted light in a finite aperture, and as described above, the light intensity of the diffracted light becomes stronger closer to the optical axis. Therefore, the cross-correlation pattern appears strengthened. Conversely, if the distance between the test pattern and the reference pattern is increased on the spatial light modulator 15, the above will be completely opposite, and the cross-correlation pattern will be closer to the optical axis. It appears at a far position and the correlated output light intensity is weakened. In addition, the interval between interference fringes becomes narrower, and interference fringes that exceed the resolution of the spatial light modulator 35 are not expressed.
The ease of use also weakens the correlated output light intensity.

For the above reasons, by moving the display position of the test pattern on the spatial light modulator 15, it becomes possible to correct the correlation output light intensity.

[0054]

Effects of the Invention As explained above, the optical pattern recognition apparatus of the present invention has achieved the above-mentioned effects. Putting these together, we get the following remarkable technical effects. That is, first, the influence of aberrations caused by the lens, the influence of non-uniformity of the light intensity of the light beam, the non-uniformity of the transmittance of the spatial light modulator, the lack of dynamic range, and the influence of the reference pattern.
Even if the correlation output light intensity becomes non-uniform due to the influence of an increase in the display area of the sample or the number of reference patterns, the reference pattern display position on the spatial light modulator and the test pattern - It is possible to obtain a high pattern recognition rate by individually changing the distance between the pattern and the display position, correcting each correlation output light intensity, and then correcting the correlation output light intensity. It became.

Second, the display position control means
Since the present invention is based on data control, it has been possible to provide an optical pattern recognition device that is capable of easily and extremely flexible correction of the correlation output light beam.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an example of an optical system for realizing an optical pattern recognition device of the present invention.

FIG. 2 is a configuration diagram showing the configuration of a conventional optical pattern recognition device.

FIG. 3 is an explanatory diagram showing a display state on a spatial light modulator when performing correction processing in a conventional optical pattern recognition device.

FIG. 4 is an explanatory diagram showing a display state on a spatial light modulator when correction processing is performed in the optical pattern recognition apparatus of the present invention and will be described in a second embodiment.

FIG. 5 is an explanatory diagram showing the display state on the spatial light modulator when performing the correction process described in Example 3 in the optical pattern recognition apparatus of the present invention.

FIG. 6 is a schematic configuration diagram of an optical pattern recognition device of the present invention using an optically addressed spatial light modulator.

FIG. 7 is a conceptual diagram showing the configuration of a reflective liquid crystal light valve used in the optical pattern recognition device of the present invention.

[Explanation of symbols]

1, 3 Image output means 2, 4
Optical Fourier transform means 5
Light detection means 6
Display position control means 11, 11' Coherent light source 12, 12' Luminous flux 13, 13' Beam expander 14, 38
Beam splitter-15, 35
Spatial light modulator 16, 36 Light flux (readout light) 21, 41
Fourier transform lenses 31, 51
Screen 32 Two-dimensional photoelectric conversion element 33
, 53 Image processing device, video amplifier, liquid crystal drive circuit 34 Beam splitter 37
Optically addressed spatial light modulator 7
0 Reflective LCD light bulb 7
0a Divided pixels 71, 76 Transparent electrode 73 Spacer 74
liquid crystal layer

Claims (5)

[Claims] Claims: 1. A test pattern and a reference pattern group are simultaneously displayed on a first spatial light modulator, and the displayed test pattern and reference pattern group are a first image output means that simultaneously outputs coherent light; and optically Fourier transforms the test pattern and the reference pattern group that are simultaneously output using the coherent light; Spatial light intensity distribution pattern
a first optical Fourier transform means that obtains a signal, and a first two-dimensional photoelectric conversion element that converts the spatial light intensity distribution pattern obtained by the first optical Fourier transform means. a second image output means capable of detecting and changing a coherent two-dimensional complex distribution of emitted light according to the detected spatial intensity distribution pattern; The two-dimensional complex amplitude distribution of the output light obtained in the means is optically Fourier transformed to obtain the correlation output light intensity between the test pattern and each reference pattern for the reference pattern group. A second optical Fourier transform means, and a correlation output between the test pattern and each reference pattern for the reference pattern group, obtained by the second optical Fourier transform means. An optical pattern recognition device comprising a light detection means for detecting light intensity by the second two-dimensional photoelectric conversion element and performing recognition processing according to the intensity of the detected correlated output light intensity. In this step, the display position of each reference pattern displayed on the first image output means is moved closer to the test pattern for the reference pattern whose correlation output light intensity is desired to be increased, and The optical pattern recognition device is characterized in that the reference pattern whose correlation output light intensity is desired to be weakened is changed so as to be farther away than the test pattern. 2. Feedback means for inputting a modulation signal corresponding to the correlation output light intensity obtained by the optical pattern recognition device according to claim 1 to the first spatial light modulator. The optical pattern recognition device according to claim 1, characterized in that: 3. The display position control means operates under computer control, and increases the display position of each reference pattern displayed on the first image output means by increasing the correlation output light intensity. For the reference pattern, move it closer to the test pattern, and for the reference pattern you want to weaken the correlation output light intensity, change it so that it is farther away from the test pattern. 3. The optical pattern recognition apparatus according to claim 1, further comprising display position control means for correcting output light intensity. 4. The second image output means includes at least:
The complex amplitude distribution of the incident light beam is modulated based on a coherent light source and a signal from a first two-dimensional photoelectric conversion element that receives the output light from the first optical Fourier transform means. 4. The optical pattern recognition device according to claim 1, wherein the optical pattern recognition device essentially consists of a second spatial light modulator that outputs a spatial light modulator. 5. The second image output means includes at least:
A third space whose optical characteristics change two-dimensionally or three-dimensionally depending on the coherent light source and the intensity distribution of the output light from the first optical Fourier transform means. Claim 1, characterized in that it consists essentially of an optical modulator,
An optical pattern recognition device according to claim 2 or 3.