JP3066457B2 - Optical pattern recognition device - Google Patents

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 apparatus using an optical writing type spatial light modulator in the field of optical information processing and optical measurement.

[0002]

2. Description of the Related Art As a conventional optical pattern recognition apparatus, a joint transform correlator using a correlation operation and a matched filter type correlator are widely known. Hereinafter, the joint transform correlator and the matched filter type correlator will be described. FIG. 3 shows a basic configuration diagram of the joint transform correlator. An image in which a reference image serving as a reference for recognition and a correlated image to be recognized are simultaneously arranged adjacent to each other is set as an input image.
As a spatial light modulator for converting a congruent Fourier transform image of a correlated image and a reference image into an intensity distribution image and displaying the intensity distribution image, a liquid crystal light valve 204 of an optical writing type and a reflection type will be described as an example. The light beam emitted from the writing laser 1 is expanded into a parallel light beam having a predetermined beam diameter by the writing beam expander 2 and then split into two light beams by the beam splitter 201. The luminous flux transmitted through the beam splitter 201 is
The film 3 on which the input image is recorded is irradiated, and the input image is converted into a coherent image. When this coherent image is subjected to Fourier transform using the writing lens 4, a congruent Fourier transform image of the reference image and the correlated image is obtained on the transform plane. Interference fringes due to interference between the Fourier transformed images of the correlated image and the reference image are superimposed on the joint Fourier transformed image. Therefore, the writing surface of the reflective liquid crystal light valve 204 is arranged on the conversion surface. Then, the joint Fourier transform image including the phase information is converted into an intensity distribution image by the liquid crystal light valve 204 and displayed.

Next, the light beam reflected by the beam splitter 201 is reflected by mirrors 202 and 203 and the polarizing beam splitter 8 to irradiate the reading surface of the reflection type liquid crystal light valve 204 and displayed on the reflection type liquid crystal light valve 204. The intensity distribution image is converted into a coherent image. This coherent image is read out as a negative image or a positive image by passing through the polarizing beam splitter 8 used in place of the analyzer. By subjecting the negative or positive image to Fourier transform again by the reading lens 9, a correlation output image including a correlation peak on the Fourier transform plane is obtained. Thus, by receiving the correlation output image with the light receiving element 10 arranged on the conversion surface, a correlation peak representing a two-dimensional cross-correlation coefficient between the correlated image and the reference image can be obtained as a correlation signal.

A congruent Fourier transform image of an input image is received by an imaging device such as a CCD camera, and its output is input to an electric writing type spatial light modulator such as a liquid crystal television to display an intensity distribution image. The method is the same in principle. Next, a matched filter type correlator will be described. FIG. 4 shows a basic configuration diagram of the matched filter type correlator. As a spatial light modulator for converting a Fourier transform image of a reference image into an intensity distribution image and displaying the intensity distribution image, a BSO crystal (Bi12SiO
This will be described with reference to (20 crystals) 303 as an example.

First, a matched filter for a reference image is prepared. The light beam emitted from the writing laser 1 is expanded into a parallel light beam having a predetermined beam diameter by the writing beam expander 2 and then split into two light beams by the beam splitter 201. The light beam transmitted through the beam splitter 201 reads a reference image displayed on a liquid crystal television (hereinafter abbreviated as liquid crystal TV) 304 and converts the reference image into a coherent image. This coherent image is Fourier-transformed by the writing lens 4, and is applied to the BSO crystal 303 as signal light at the time of producing a hologram. At this time, the light beam reflected by the beam splitter 201 at the same time is reflected by the mirror 202, passes through the shutter 301 in the open state, is reflected by the mirror 203, and is used as a BSO crystal 303 as reference light when producing a hologram.
Is irradiated. At this time, the BSO crystal 303 is irradiated with the signal light and the reference light at a predetermined angle, and the BSO crystal 303
Since an intensity distribution of interference fringes due to the signal light and the reference light is formed thereon, a hologram is recorded on the BSO crystal 303.
The hologram recorded on the BSO crystal 303 is called a matched filter.

Next, a correlation operation is performed using the above-mentioned matched filter. First, the shutter 301 is closed. Then, the correlated image is displayed on the liquid crystal TV 304. This correlated image is converted into a coherent image in the same manner as the reference image. The coherent image is Fourier-transformed by the writing lens 4 and irradiated to the BSO crystal 303 as a matched filter. The luminous flux transmitted through the BSO crystal 303, which is a matched filter, is again Fourier-transformed by the reading lens 9, so that the phase relationship between the reference image and the correlated image is obtained on the light-receiving element 10 arranged on the Fourier transform plane. A correlation peak representing a number can be obtained.

In order to analyze the recognition capability of the joint transform correlator and the matched filter type correlator, computer simulations are actively performed. Attempts have been made to further improve the recognition ability by computer simulation. As a result, it was found that in the joint transform correlator and the matched filter correlator, the non-linearity at the time of converting the Fourier transform image into the intensity image greatly affected the recognition ability. Rather than performing the correlation operation with the Fourier transform image of the input image as a linear value, the half-width of the correlation peak is smaller and the S / N ratio is better when the correlation operation is performed by binarizing with an appropriate threshold value. Improve your recognition ability.

Further, it has been found that a correlator having a very high recognition capability can be obtained by setting an optimum threshold value for binarizing a Fourier transform image of an input image into an intensity distribution image. (Eg Bee Javidi and Sea Jay Kuo, Applied Optics, 2
7, 663 (1988): B. Javidi and CJ Kuo, Applied Optics, 2
7,663 (1988). It is known that the optimum threshold value varies depending on the input image, and that the recognition ability may be improved by setting the threshold value with an appropriate spatial distribution.
(E.g. Bee Javidie and Jay One,
Applied Optics, 30, 967 (1991): B. Javidi and
J. Wang, Applied Optics, 30, 967 (1991). ) Also in recent years,
With the progress of research in the fields of optical information processing and optical measurement described above, a spatial light modulator having high resolution and high-speed response has been required. Heretofore, as an optical writing type spatial light modulator, a device using an electro-optic crystal such as a BSO crystal (Bi12SiO20 crystal) as a light modulation material, a liquid crystal light valve using a nematic liquid crystal, and the like have been widely used. Was. However, they did not sufficiently satisfy the requirements such as resolution and high-speed response. Therefore, in recent years, an optical writing type spatial light modulator (hereinafter, FLC-OASL) using a ferroelectric liquid crystal as a light modulation material has been developed.
M) has been developed and started to be used.

First, the structure of the FLC-OASLM will be described. The difference from a liquid crystal light valve using a conventional nematic liquid crystal is that a ferroelectric liquid crystal having a clear bistability between light transmittance or light reflectance and an applied voltage is used as a liquid crystal layer. FIG. 2 shows the FLC-OASLM
FIG. 3 is a cross-sectional view showing the structure of FIG. Transparent substrates 101a, 101 such as glass and plastic for holding liquid crystal molecules
As for b, transparent electrode layers 102a and 102b are provided on its surface, and alignment film layers 103a and 103b on which silicon monoxide is obliquely vapor-deposited at an angle in the range of 75 to 85 degrees from the normal direction of the transparent substrate. The transparent substrates 101a and 101b are arranged so that their alignment film layers 103a and 103b face each other with a gap controlled therebetween via a spacer 109 to sandwich the ferroelectric liquid crystal layer 104 therebetween. Further, a photoconductive layer 105, a light shielding layer 106, and a dielectric mirror 107 are formed on the transparent electrode layer 102a on the writing side by light between the alignment film layer 103a and the transparent substrate 101a on the writing side. Side transparent substrate 1
01b, the anti-reflection coating layer 108
a, 108b are formed.

Next, the FLC-OASLM having the above structure
Here is how to initialize. The first method is once FLC-
The entire writing surface of the OASLM is irradiated with light, and a pulse voltage or a DC bias voltage sufficiently higher than a threshold voltage at the time of light irradiation or a DC bias voltage on which an AC voltage of 100 Hz to 50 kHz is superimposed is used as an erasing voltage and the transparent electrode layer 102
The ferroelectric liquid crystal molecules are aligned in a stable state in one direction by applying a voltage between a and 102b, and the state is stored. Second
The method of the above is, without light irradiation, a pulse voltage or a DC bias voltage sufficiently higher than the threshold voltage in the dark, or 10
A DC bias voltage on which an AC voltage of 0 Hz to 50 kHz is superimposed is applied between the transparent electrode layers 102a and 102b as an erasing voltage to align the ferroelectric liquid crystal molecules in a stable state in one direction and store the state. Normally, the threshold voltage in darkness is higher than that in light irradiation.

The operation after the FLC-OASLM is initialized as described above will be described. A transparent electrode is used as a transparent electrode as a writing voltage using a pulse voltage having a polarity opposite to that of the initialization or a DC bias voltage or a DC bias voltage obtained by superimposing an AC voltage of 100 Hz to 50 kHz, which is lower than the threshold voltage during darkness and higher than the threshold voltage during light irradiation. Layers 102a and 10
The image is optically written by a laser beam or the like while the voltage is applied between 2b. Carriers are generated in the photoconductive layer 105 in the region irradiated with the laser, and the generated carriers drift in the direction of the electric field due to the applied voltage. As a result, the threshold voltage is lowered, and the region irradiated with the laser is higher than the threshold voltage. The applied voltage of the opposite polarity to that at the time of initialization is applied, and the molecules of the ferroelectric liquid crystal are inverted due to the reversal of spontaneous polarization, and the state shifts to the other stable state, so the image is binarized. It is memorized. The recorded image remains recorded even when the driving voltage becomes zero.

The image thus binarized and stored is irradiated with linearly polarized readout light whose polarization axis is aligned with the direction of alignment of liquid crystal molecules (or a direction perpendicular thereto) aligned by initialization, and By passing the light through an analyzer arranged such that the polarization axis is perpendicular (or parallel) to the polarization direction of the light reflected by the dielectric mirror 107, it is possible to read in a positive state or a negative state. A polarizing beam splitter is often used as an analyzer.

Not limited to such FLC-OASLM,
A general optical writing type spatial light modulator (hereinafter abbreviated as OASLM) has begun to be widely used for optical information processing. A correlator such as a joint transform correlator or a matched filter correlator often used for character or image recognition, an optical neural network, and the like are typical examples. Previously, threshold processing for converting a Fourier transform image into an intensity distribution image in a joint transform correlator and production of a binarized matched filter were once taken into a computer by a CCD camera or the like, and then performed in a computer. And then display it on a liquid crystal television or the like.

However, with the advance of OASLM, non-linear processing in a joint transform correlator or a matched filter type correlator often used for binarization of an input image or image recognition can be processed in parallel with light. It has become possible to shorten the processing time.

[0015]

However, conventionally, the control of the sensitivity of the OASLM and the threshold value for binarization are performed by the OASLM.
Since it is controlled by the LM driving conditions, only spatially uniform processing can be realized. For this reason, it has been difficult to improve the recognition capability of the joint transform correlator and the matched filter type correlator. In order to improve the recognition ability, electrical processing by a computer or the like is forced, and the processing speed is significantly reduced. Further, when the OASLM is used, it is difficult to optically realize nonlinear processing having a certain spatial distribution. For this reason, in order to perform more advanced nonlinear processing, it was necessary to take in the computer once and perform the nonlinear processing in the computer. However, since optical information is converted to electrical information, the problem of large-scale parallelism of light cannot be used effectively, and the non-linear processing requires enormous computation time, making high-speed processing impossible. there were.

Further, when the correlated image is replaced,
Unless the sensitivity of the OASLM or the threshold for binarization is changed, high recognition ability cannot be obtained. In order to increase the processing speed, it is necessary to control the sensitivity of the OASLM and the threshold value for binarization. However, when the sensitivity of the OASLM is changed over time, the driving conditions of the OASLM must be changed over time, so that high-speed processing is difficult and the system becomes complicated.

For the reasons described above, the improvement of the processing speed and the recognition ability of the optical pattern recognition device has been hindered.
Also, in consideration of speeding up and parallel processing, it is desired that the control method uses an optical method. The purpose of the present invention is
An object of the present invention is to provide an optical pattern recognition device in which the operation threshold value of an optical writing type spatial light modulator is arbitrarily controlled and the processing speed and the recognition ability are improved.

[0018]

In order to solve the above-mentioned problems, the present invention uses an optical writing type spatial light modulator to automatically form a required pattern on a two-dimensional image obtained from an imaging device. An optical pattern recognition device for recognizing and measuring an optical writing type spatial light modulator; writing light irradiating means for applying writing light for writing an image to the optical writing type spatial light modulator; Reading light irradiating means for reading an image recorded or displayed on the optical writing type spatial light modulator, and a bias for irradiating the optical writing type spatial light modulator with bias light for adjusting and controlling sensitivity Light irradiation means, and bias light adjusting means for changing at least one of the irradiation time of the bias light and the light intensity, wherein the irradiation time of the writing light and the irradiation time of the bias light are the optical writing time. Of embedded spatial light modulator Be consistent operating time and each at least a predetermined time has an optical pattern recognition apparatus according to claim.

[0019]

In the optical pattern recognition apparatus constructed as described above, particularly when the FLC-OASLM is used, the light from the auxiliary light source is biased during the writing operation time of the FLC-OASLM or a part thereof. The light is emitted from the writing side of the FLC-OASLM as light. Where F
Check if there is a dielectric mirror and light shielding layer of LC-OAASLM
Or, if any, if they have a predetermined transmittance, the writing light and the bias light will be FLC-OASL
Since the same action is performed on the photoconductive layer of M, light from the auxiliary light source or writing light may be emitted from the reading side of the FLC-OASLM, and the bias light is not limited to light from the auxiliary light source. The reading light itself may be used as the bias light.

The sum of the light intensities of the writing light and the bias light is FLC
-When the OASLM threshold is exceeded, FLC-OAS
The image can be binarized and recorded on the LM. That is,
By controlling the bias light intensity, the threshold of the FLC-OASLM for the writing light can be apparently changed. Further, the threshold of the FLC-OAASLM is affected not only by the sum of the light intensities of the writing light and the bias light but also by the irradiation time. During the writing operation time of the FLC-OASLM, a bias light having a constant intensity is irradiated on the writing side of the FLC-OASLM, and the irradiation time is lengthened. Then, by irradiating the weak writing light to the FLC-OASLM, the FLC-O
When the value becomes equal to or larger than the ASLM threshold value, the image can be binarized and recorded on the FLC-OAASLM. In other words, by controlling the irradiation time of the bias light, the FLC
-It becomes possible to change the threshold value of OASLM apparently. Therefore, it is possible to control the threshold of the FLC-OASLM by controlling the light intensity of the bias light or the bias light irradiation time. Changing the threshold of the FLC-OASLM spatially uniformly can be realized by controlling the bias light irradiation time and / or the bias light intensity.

Further, by forming a spatial distribution of the light intensity of the bias light, it becomes possible to spatially control the threshold value of the FLC-OASLM corresponding to the spatial distribution of the bias light intensity. Further, by changing the bias light intensity over time, the time change of the threshold value of the FLC-OASLM can be realized. The above is the case of FLC-OASLM.
OA using material other than ferroelectric liquid crystal as light modulating material
The same can be realized for the SLM. However, 2
In the case other than the binarization (threshold), it may be considered that the apparent sensitivity of the OASLM is controlled instead of the binarization (threshold) control. In this way, it is possible to arbitrarily control not only the FLC-OASLM but also the more general OASLM apparent sensitivity by the method using the bias light irradiation. Hereinafter, the term “sensitivity” is widely used in the case of OASLM, and the term “threshold” is particularly used in the case of OASLM that performs binarization (threshold) processing.

By controlling the non-linear processing (threshold) processing of the optical pattern recognition apparatus using such a sensitivity (threshold) control method, the performance of a joint transform correlator or a matched filter correlator can be improved. it can.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of an embodiment of an optical pattern recognition device according to the present invention. This is a case where a joint transform correlator used for recognition of characters and images is used. Here, the description will be made on the assumption that the FLC-OASLM described in FIG. 2 is used as the OASLM.

FLC-OASLM5 is FLC-OAS
It is connected to the LM drive circuit 19. This FLC-O
The ASLM drive circuit 19 is controlled by a computer 20. The writing light irradiating means for irradiating the FLC-OASLM 5 with writing light for writing an image is a writing laser 1.
And a writing beam expander 2, a film 3 for presenting an input image, and a writing lens 4. Here, film 3
Is set on the front focal plane of the writing lens 4. The Fourier transform image of the input image of the film 3 is FLC-
FLC-OASLM5 to irradiate OASLM5
Are set on the rear focal plane of the writing lens 4. One reference image and one or more correlated images are recorded on the film 4.

A reading light irradiating means for reading an image recorded on the FLC-OASM 5 comprises a reading laser 6, a reading beam expander 7, a polarization beam splitter 8, a reading lens 9, and a light receiving element 10. The light beam emitted from the reading laser 6 reads an image recorded on the FLC-OASLM 5. The read image is irradiated onto the light receiving element 10 by the reading lens 9. FLC-
The OASLM 5 is set on the front focal plane of the reading lens 9. The light receiving element 10 is set on the rear focal plane of the reading lens 9.

The bias light irradiating means for irradiating the bias light for controlling the threshold value of the FLC-OASLM 5 includes an auxiliary light source 11, a diffusion plate 12, a lens 13, and a bias light liquid crystal TV 14 for presenting a spatial distribution of the bias light. , A bias light lens 15, a mirror 16, and a half mirror 17 placed between the writing lens 4 and the FLC-OASLM 5 for irradiating the FLC-OAASLM 5 with bias light. Liquid crystal T for bias light
V14 is connected to the image memory 18 and controlled by the computer 20. Bias light lens 15
Is a liquid crystal TV14 for bias light and FLC-OASLM5
Are set so as to form an imaging relationship. The bias light liquid crystal TV 14 is used as bias light adjusting means for changing at least one of the irradiation time and the light intensity of the bias light. Here, the irradiation time of the writing light and the irradiation time of the bias light need to coincide at least a predetermined time with the writing operation time of the FLC-OAASLM 5, respectively.

The joint transform correlator of the embodiment shown in FIG. 1 operates as follows. The writing laser 1 is expanded by a writing beam expander 2 into a parallel light beam having a predetermined beam diameter. A film 3 on which an input image of one reference image and one or more correlated images is recorded with the parallel light flux
Is read out as a coherent image. This coherent image is Fourier-transformed by the writing lens 4. FL
The C-OASLM 5 irradiates the Fourier transform image of the coherent image from the writing side. And FLC-OASL
M5 binarizes this Fourier transformed image and records it as an intensity distribution image.

The reading laser 6 is expanded by a reading beam expander 7 into a parallel light beam having a predetermined beam diameter. This parallel light beam is reflected by the polarization beam splitter 8 and radiated to the reading side of the FLC-OASLM 5. Then, this parallel light beam is reflected by the FLC-OASLM 5, passes through the polarizing beam splitter 8, and reads out an intensity distribution image recorded on the FLC-OASLM 5. FLC-OASL
The intensity distribution image read from M5 is further subjected to Fourier transform by the reading lens 9, and is irradiated on the light receiving element 10.
Then, a correlation peak as a result of the correlation operation between the reference image and the correlated image is observed on the light receiving element 10. The intensity of the correlation peak as a result of the correlation operation is determined by the similarity between the reference image and the correlated image. If the reference image and the correlated image are the same image, a very sharp and strong correlation peak is obtained. If the reference image and the correlated image are completely different images, a very weak correlation peak is obtained.

In general, the recognition ability of the joint transform correlator largely depends on the nonlinearity when transforming the Fourier transform image of the input image into the intensity distribution image. When converting a Fourier-transformed image into an intensity distribution image, recognition ability can be improved by setting an optimal threshold value. That is, the recognition capability of the joint transform correlator in FIG.
It is greatly affected by the threshold value of SLM5. FLC-OASL
By spatially controlling the threshold value of M5, the recognition capability of the joint transform correlator can be improved. For such a purpose, bias light irradiation is performed to control the threshold.

FLC-OAASLM by bias light irradiation
The threshold control method of No. 5 will be described below. FLC-OASL
During the write operation time of M5 or a part of the write operation time, light from the auxiliary light source is irradiated as bias light from the write side of the FLC-OASLM5. The writing light and the bias light are FLC-
Since the same operation is performed on the photoconductive layer of the OASLM 5, the sum of the light intensities of the writing light and the bias light is FLC-OAS.
Even if it exceeds the threshold of LM5, that Do can be binarized record an image.

Further, the threshold of the FLC-OASLM is affected not only by the sum of the light intensities of the writing light and the bias light but also by the irradiation time. During the writing operation time of the FLC-OASLM, a bias light having a constant intensity is irradiated on the writing side of the FLC-OASLM, and the irradiation time is lengthened. Then, by irradiating the weak writing light to the FLC-OASLM, the FLC-O
When the value becomes equal to or larger than the ASLM threshold value, the image can be binarized and recorded on the FLC-OAASLM. In other words, by controlling the irradiation time of the bias light, the FLC
-It becomes possible to change the threshold value of OASLM apparently. Therefore, it is possible to control the threshold of the FLC-OASLM 5 by controlling the light intensity of the bias light or the bias light irradiation time.

In order to generate such a bias light intensity distribution, an auxiliary light source 11, a diffusion plate 12, a lens 13, a bias light liquid crystal TV 14, and a bias light lens 15 were used as bias light irradiating means. Liquid crystal TV1 for bias light
4 is connected to an image memory 18 and a computer 20
Is controlled by The light of the auxiliary light source 11 is once radiated to the diffusion plate 12 to remove the intensity distribution of the light source itself, and is radiated by the lens 13 to the bias light liquid crystal TV 14 as bias light. And the liquid crystal T for bias light
The image displayed at V14 is read as a bias light intensity distribution. The bias light intensity distribution obtained by the bias light liquid crystal TV 14 is adjusted by the bias light lens 15 to FL.
Irradiate the writing side of C-OASLM5. If the transmittance of the bias liquid crystal TV 14 for forming the intensity distribution of the bias light is made spatially uniform, the FLC-OAS is generated by the bias light.
The threshold value of LM5 can be controlled spatially uniformly. FLC-O
When it is desired to spatially change the threshold value of the ASLM 5, if the spatial distribution is displayed on the bias light liquid crystal TV 14, a threshold value of the FLC-OASLM 5 having an arbitrary spatial distribution can be realized.

There are many types of spatial intensity distribution of the bias light, such as central symmetry, inverse Gaussian distribution, and spatial frequency division. In this way, any spatial intensity distribution best suited to the purpose of the system can be realized. For example, using a centrally symmetric inverse Gaussian distribution, FLC-O
High frequency components can be recorded while leaving low frequency components of the Fourier transform image of the input image recorded on the ASLM. In this way, the intensity of the correlation peak in the autocorrelation is strong, and the shape of the correlation peak becomes sharper. Therefore, the recognition capability of the correlator is improved.

Further, since the bias light liquid crystal TV 14 is used to realize the spatial intensity distribution of the bias light, it is possible to easily change the threshold of the FLC-OASLM 5 with time. By temporally changing the spatial distribution displayed on the bias light liquid crystal TV 14,
Time change of the threshold value of the FLC-OAASLM can be realized. Here, the auxiliary light source 11 may be a white light source, an LED, a laser, or the like. When a laser and a beam expander are used instead of the auxiliary light source 11, the diffusion plate 12, and the lens 13, attention must be paid to the interference between the writing laser 1 and the light beam. In this case, there is no interference fringe with the light beam by the writing laser 1 or FLC-OASLM.
It is necessary to set the number of interference fringes sufficiently larger than the resolution of 5.

Although the liquid crystal TV is used to create the intensity distribution of the bias light, the liquid crystal TV is not limited to the liquid crystal TV but may be any as long as it can create the intensity distribution of the bias light.
Or an output from an interferometer or an electric address type spatial light modulator other than the liquid crystal TV may be used. When the threshold value does not change with time, a photographic film or the like can be used instead of the bias light liquid crystal TV 14.

This embodiment is a reflection type FLC-OASL.
In the case of M, the same can be realized for a transmission type FLC-OASLM. Furthermore, FLC-OAS
If the dielectric mirror and the light shielding layer of the LM5 are not provided, or if they have a predetermined transmittance, the writing light and the bias light may be irradiated from the reading side of the FLC-OASLM5, The same threshold value control can be performed by irradiating the readout light itself as bias light to the readout side of the FLC-OASLM5.

An OAS using a material other than a ferroelectric liquid crystal as a light modulating material instead of the FLC-OASLM5.
The same can be achieved for the LM. However, in cases other than binarization, OASLM is not called threshold control.
Can be controlled. Next, FIGS. 5 and 6 show the state of the correlation peak when the writing side of the FLC-OAASLM 5 is irradiated with the spatially uniform bias light. Experimental results of an autocorrelation using a character A as a reference image and a character A as a correlated image as input images and a cross-correlation using a character B as a correlated image are shown.

FIG. 5 is a graph showing a change in the correlation peak intensity when the bias light intensity is changed. The vertical axis shows the correlation peak intensity, and the horizontal axis shows the bias light intensity. The total light amount of the input image converted into the coherent image was measured with a power meter, and the total light amount was used as the writing light amount. In the case of autocorrelation, two results, that is, a case where the writing light amount is small and a case where the writing light amount is large, are listed. In the case of autocorrelation with a small writing light amount, the correlation peak intensity increases as the bias light intensity increases. When the writing light amount is strong,
When the bias light intensity is increased from 0, the correlation peak intensity increases. However, when the bias light intensity becomes too strong, the correlation peak intensity becomes weaker.
In the case of cross-correlation, as the bias light intensity increases, the correlation peak intensity decreases. FIG. 6 is a graph showing a change in the full width at half maximum of the correlation peak when the bias light intensity is changed for the autocorrelation of the character A.
The vertical axis shows the full width at half maximum of the correlation peak, and the horizontal axis shows the bias light intensity.

FIG. 6 is a plot for the case of two writing light amounts of the autocorrelation of FIG. In both cases in FIG. 6, as the bias light intensity was increased, the full width at half maximum of the correlation peak was reduced. From the results of FIGS. 5 and 6, FLC
-It can be seen that there is an optimum bias light intensity for irradiating the OASLM 5. The recognition ability of the joint conversion correlator may be deteriorated by the irradiation of the bias light. In other words, it is understood that the recognition ability of the joint transform correlator is improved by irradiating the bias light and setting the threshold value of the FLC-OASLM 5 to an optimum value.

FIG. 7 is a block diagram of another embodiment of the optical pattern recognition device according to the present invention. This embodiment is shown in FIG.
Is made more compact. In the embodiment of FIG. 7, the two lasers of the writing laser 1 and the reading laser 6 of FIG.
A joint conversion correlator is realized by using a CRT 605 instead of the auxiliary light source 11, the diffusion plate 12, the lens 13, and the bias light liquid crystal TV 14 of FIG. The description of the present embodiment is partially omitted or simplified for portions having the same configuration and operation.

The writing light irradiating means for irradiating writing light for writing an image on the FLC-OASMLM 5 includes a writing laser 1 and a writing beam expander 2, two half mirrors 601 and 602, Input LCD TV6 for presenting an image
04, and a writing lens 4 for irradiating the writing side of the FLC-OASLM 5 with the Fourier transform image of the input image converted into the coherent image. Here, input liquid crystal TV
604 is placed on the front focal plane of the writing lens 4 and FLC
The OASLM 5 is located on the rear focal plane of the writing lens 4. The input liquid crystal TV 604 is connected to the image memory 18 and controlled by the computer 20. In addition, one reference image and one or a plurality of correlated images are presented on the input liquid crystal TV 604.

The reading light irradiating means for reading out the image recorded on the FLC-OASLM 5 shares the writing laser 1 and the writing beam splitter 2 of the writing light irradiating means, and the half mirror 601 and the mirror 603 It comprises a polarizing beam splitter 8, a reading lens 9, and a light receiving element 10. A parallel light beam emitted from the writing laser 1 and expanded to a predetermined diameter by the writing beam expander 2 is converted into a half mirror 601.
, Is reflected by the mirror 603, and is irradiated by the polarization beam splitter 8 on the reading side of the FLC-OASLM 5. Then, the Fourier-transformed intensity distribution image of the input image binarized and recorded on the FLC-OASLM 5 is read out, and the light-receiving element 10 is irradiated with the reading-out lens 9. Where FL
The C-OASLM 5 is placed on the front focal plane of the reading lens 9, the light receiving element 10 is placed on the rear focal plane of the reading lens 9, and the intensity distribution image of the intensity distribution image recorded on the FLC-OASLM 5 by the reading lens 9 is read. Fourier transform image is light receiving element 1
It is irradiated to 0.

The bias light irradiating means for irradiating the bias light for controlling the threshold value of the FLC-OAASLM 5 includes a CRT 605 for displaying the intensity distribution of the bias light and a bias light imaging lens 606. The intensity distribution of the bias light by the image displayed on the CRT 605 is FLC-OASLM.
The imaging lens 606 for bias light is set so that an image is formed on the imaging lens 5. The bias light based on the image displayed on the CRT 605 passes through the half mirror 602 and the writing lens 4 and is irradiated from the writing side of the FLC-OASLM 5 to FL.
An image is formed on the C-OASLM5.

In this embodiment, the bias light irradiating means is C
Using the RT 605, an image having a spatial distribution is displayed on the CRT 605 as bias light. Therefore CRT60
5, the bias light intensity is changed spatially by changing the spatial distribution of the image displayed in FIG.
The threshold of the SLM 5 can be spatially controlled. Also,
The threshold of the FLC-OAASLM 5 can be changed with time. According to the bias light intensity distribution displayed on the CRT 605, the FLC-OASLM5
Can be arbitrarily controlled, and an optical pattern recognition device having high recognition ability can be constructed.

Here, it goes without saying that a beam splitter may be used instead of the half mirror. This embodiment is a case of a reflection type FLC-OASLM,
The same can be realized for the transmission type FLC-OASLM. If the dielectric mirror and the light-shielding layer of the FLC-OAASLM 5 are not provided, or if they have a predetermined transmittance, the writing light and the bias light are FL.
Irradiation may be performed from the reading side of the C-OASLM5, or the reading light itself may be used as the bias light as the FLC-OASLM5.
The same threshold value control can be performed by irradiating the read side.

An OAS using a material other than a ferroelectric liquid crystal as a light modulating material instead of the FLC-OASLM5.
The same can be achieved for the LM. However, in cases other than binarization, OASLM is not called threshold control.
Can be controlled. FIG. 8 is a configuration diagram of another embodiment of the optical pattern recognition device according to the present invention. This is a case where a matched filter type correlator using a matched filter used for image recognition or the like is used. The bias light irradiating means for irradiating the bias light for controlling the threshold value of the FLC-OASLM 5 is the same as that of the embodiment of FIG.

The writing light irradiating means for irradiating the FLC-OASLM 5 with writing light for writing an image is composed of a signal light irradiating means called a matched filter for producing a hologram and a reference light irradiating means. The signal light irradiating means for producing the hologram includes a writing laser 1 and a writing beam expander 2.
And an input liquid crystal TV 604 for presenting a reference image and a writing lens 4. Here, the input liquid crystal TV 604 is placed on the front focal plane of the writing lens 4, and the FLC-OASLM
Reference numeral 5 is located on the rear focal plane of the writing lens 4. Here input LCD TV604 is connected to the image memory 18 are controlled by a computer-2 0.

The reference beam irradiating means at the time of producing the hologram comprises a beam splitter 701 and two mirrors 702 and 703. The collimated light beam emitted from the writing laser 1 and expanded to a predetermined diameter by the writing beam expander 2 is reflected by the beam splitter 701 and is directed to the writing side of the FLC-OASLM 5 by the mirrors 702 and 703. At an incident angle of

The readout light irradiating means for reading out the image recorded on the FLC-OASLM 5 includes a readout laser 6, a readout beam expander 7, a readout film 704 for presenting a correlated image, a Fourier transform lens 705, and a polarization. It comprises a beam splitter 8, a reading lens 9, and a light receiving element 10. Here, the reading film 704 is placed on the front focal plane of the Fourier transform lens 705, and the FLC-OASLM is used.
Reference numeral 5 denotes a rear focal plane of the Fourier transform lens 705 and a front focal plane of the reading lens 9. Further, light receiving element 1
0 is located on the rear focal plane of the reading lens 9.

First, a method for manufacturing a matched filter will be described. The writing laser 1 is expanded by a writing beam expander 2 into a parallel light beam having a predetermined beam diameter. This parallel light beam is applied to the input liquid crystal TV 604, and the reference image displayed on the input liquid crystal TV 604 is read as a coherent image. The read coherent image is irradiated with a Fourier-transformed image that has been Fourier-transformed by the writing lens 4 to the writing side of the FLC-OASLM 5 as signal light at the time of producing a hologram. At this time, the parallel light beam reflected by the beam splitter 701 at the same time is reflected by the mirror 702 and the mirror 703, and is radiated to the writing side of the FLC-OASLM 5 as reference light at the time of producing a hologram. At this time, the signal light and the reference light are applied to the FLC-OAASLM 5 at a predetermined angle, and the FLC-OA
An intensity distribution of interference fringes due to the signal light and the reference light is formed on the SLM 5.

The intensity distribution is calculated using FLC-OASLM.
5 is binarized and recorded. The hologram recorded on the FLC-OAASLM 5 largely depends on the ability of image recognition. Therefore, as a method of controlling the threshold value of the FLC-OASLM 5, bias light irradiation is performed. As in the embodiment of FIG. 1, the threshold of the FLC-OASLM 5 is controlled by the bias light. The threshold of the FLC-OASLM 5 is controlled by the optimum bias light intensity or the bias light irradiation time presented by the bias light liquid crystal TV 14, or both. FLC-O with this hologram recorded
ASLM5 is called a matched filter.

Next, a correlation operation is performed using the above matched filter. The light beam emitted from the reading laser 6 is expanded by the reading beam expander 7 into a parallel light beam having a predetermined beam diameter. The parallel light beam is irradiated on the reading film 704, and the correlated image recorded on the reading film 704 is read as a coherent image. This coherent image is converted to a Fourier transform lens 705
To perform a Fourier transform and FLC-O which is a matched filter
Irradiate from the read side of ASLM5. The readout light reflected by the FLC-OASML5, which is a matched filter, passes through the polarization beam splitter 8 and is again subjected to Fourier transform by the readout lens 9, so that the readout light is reflected on the light receiving element 10 arranged on the Fourier transform plane. A correlation peak representing a correlation coefficient between the reference image and the correlated image can be obtained. Since the FLC-OASLM 5 is used for producing the matched filter and the input liquid crystal TV 604 is used for displaying the reference image, the reference image can be changed in real time or at high speed, and a high-speed correlation operation can be realized. Then, by making the threshold value of the FLC-OASLM 5 an optimum value when producing a matched filter, an optical pattern recognition device having high recognition capability can be constructed.

Here, the auxiliary light source 11 is a white light source or LE.
D, laser and the like are conceivable. In the case where a laser and a beam expander are used instead of the auxiliary light source 11, the diffusion plate 12, and the lens 13, attention must be paid to interference between the writing laser 1 and the light beam. In this case, there is no interference fringe with the light beam by the writing laser 1 or F
It is necessary to set the number of interference fringes sufficiently larger than the resolution of the LC-OASLM5.

Although the liquid crystal TV is used to generate the intensity distribution of the bias light, the liquid crystal TV is not limited to the liquid crystal TV as long as it can generate the intensity distribution of the bias light.
Or an output from an interferometer or an electric address type spatial light modulator other than the liquid crystal TV may be used. When the threshold value does not change with time, a photographic film or the like can be used instead of the bias light liquid crystal TV 14.

This embodiment is a reflection type FLC-OASL.
In the case of M, the same can be realized for a transmission type FLC-OASLM. Furthermore, FLC-OAS
If the LM dielectric mirror and the light-shielding layer are absent, or if they have a predetermined transmittance,
The writing light and the bias light may be applied from the reading side of the FLC-OASLM 5, or the same threshold control can be performed by irradiating the reading light itself as the bias light to the reading side of the FLC-OASLM 5.

An OASL using a material other than a ferroelectric liquid crystal as a light modulation material instead of the FLC-OAASLM.
The same can be realized for M. However, in cases other than the binarization, it can be said that the sensitivity of the OASLM can be controlled without saying threshold control. FIG. 9 is a configuration diagram of another embodiment of the optical pattern recognition device according to the present invention. This embodiment is similar to the embodiment shown in FIG. 7 and is designed to make the embodiment shown in FIG. 8 more compact. The two lasers of the writing laser 1 and the reading laser 6 of FIG. 8 are shared by one writing laser 1, and the auxiliary light source 11, the diffusion plate 12, the lens 13, the bias light and the bias light of FIG. CRT6 instead of liquid crystal TV14
05 realizes a matched filter type correlator. The description of the present embodiment is partially omitted or simplified for portions having the same configuration and operation.

The writing light irradiating means for irradiating the FLC-OASLM 5 with writing light for writing an image is, as in the embodiment of FIG. 8, a signal light irradiating means called a matched filter and a reference light irradiating means for producing a hologram. Consists of The signal light irradiating means includes a writing laser 1 and a writing beam expander 2, two half mirrors 601 and 602, an input liquid crystal TV 604 for presenting a reference image, and a FLC-OASLM5 for a Fourier transform image of the reference image. And a writing lens 4 for irradiating the writing side. Here, the input liquid crystal T
V604 is placed on the front focal plane of the writing lens 4 and FL
The C-OASLM 5 is placed on the back focal plane of the writing lens 4. The input liquid crystal TV 604 is connected to the image memory 18 and controlled by the computer 20.

The reference light irradiating means at the time of producing the hologram includes a reference light half mirror 801 and a beam splitter 802. A parallel light beam emitted from the writing laser 1 and expanded to a predetermined diameter by the writing beam expander 2 is split into two light beams by the half mirror 801. Half mirror 8
The light beam reflected by 01 is reflected by the beam splitter 802 and irradiated on the writing side of the FLC-OASLM5.

The reading light irradiating means for reading out the image recorded on the FLC-OASLM 5 shares the writing laser 1 and the writing beam splitter 2 of the writing light irradiating means, and the half mirror 601 and the half mirror 801 are used. , Reading film 704, mirror 603, Fourier transform lens 705, polarizing beam splitter 8, reading lens 9, and light receiving element 1
Consists of zero. Here, the reading film 704 is placed on the front focal plane of the Fourier transform lens 705, and FLC-OASL
M5 is located at the back focal plane of the Fourier transform lens 705. Further, a correlated image is presented on the reading film 704.

The bias light irradiating means for irradiating the bias light for controlling the threshold value of the FLC-OASLM 5 is shown in FIG.
C that displays the intensity distribution of the bias light
The intensity distribution of the image presented on the RT 605 and the CRT 605 becomes the bias light intensity distribution, and the FLC-OASLM
The imaging lens 606 for bias light is set so that an image is formed on the imaging lens 5. The bias light based on the image displayed on the CRT 605 passes through the half mirror 602 and the writing lens 4 and forms an image on the FLC-OASLM 5.

In this embodiment, the CRT 6
8 is basically the same as the embodiment in FIG. 8 except that the writing laser and the reading laser 6 in FIG. 8 are shared by one writing laser 1. Beam splitter 80 between writing lens 4 and FLC-OASLM 5
Although 2 is arranged, the method of controlling the threshold value of the FLC-OASLM 5 is the same as that of FIG.

The reference light at the time of producing the hologram is F
The LC-OASLM5 is irradiated. The light beam emitted from the writing laser 1 and expanded by the writing beam expander 2 into a parallel light beam having a predetermined diameter is converted into a half mirror 601.
Is split into two light beams. The luminous flux reflected by the half mirror 601 is the input liquid crystal TV6 on which the reference image is presented.
Then, the reference image is read as a coherent image. The read reference image is reflected by the half mirror 602, and is irradiated as a Fourier transform image on the writing side of the FLC-OAASLM5. The reference light at the time of producing the hologram is
The light flux transmitted through the half mirror 601 is reflected by the reference light half mirror 801 and the beam splitter 802, and
Irradiate the writing side of C-OASLM5. An interference fringe formed by the reference light and the signal light is formed on the FLC-OASLM 5, and a binary filter is recorded on the FLC-OASLM 5 to produce a matched filter.

A correlation operation is performed using this matched filter. The light beam transmitted through the half mirror 801 irradiates the reading film 704 and reads the correlated image as a coherent image. The read coherent image is reflected by a mirror 603 and is subjected to a Fourier transform lens 705.
Is Fourier-transformed. This Fourier transform image is FL
The reading side of the C-OASLM 5 is irradiated as reading light.
The read light reflected by the FLC-OASLM 5, which is a matched filter, passes through the polarizing beam splitter 8, and is again subjected to Fourier transform by the read lens 9, so that the correlation coefficient between the reference image and the correlated image is formed on the light receiving element 10. A representative correlation peak can be obtained.

In this embodiment, the bias light irradiating means has a CR
Since T605 is used, the threshold of the FLC-OASLM5 can be spatially controlled by changing the bias light intensity spatially. FLC-OASLM5
Can also be controlled. in this way,
By irradiating the bias light, the threshold of the FLC-OAASLM can be controlled, and an optimal matched filter can be manufactured. Perform a correlation operation using this matched filter,
Obtain the correlation peak.

Here, it goes without saying that a beam splitter may be used instead of the half mirror. This embodiment is a case of a reflection type FLC-OASLM,
The same can be realized with a transmission type FLC-OASLM. Further, if there is no dielectric mirror and light shielding layer of the FLC-OASLM, or if they have a predetermined transmittance, the writing light and the bias light are irradiated from the reading side of the FLC-PASLM5. FLC-OASL using the read light itself as bias light
The same threshold value control can be performed by irradiating the reading side of M5.

An OASL using a material other than a ferroelectric liquid crystal as a light modulation material instead of the FLC-OAASLM.
For M, the OASLM processing is not necessarily binarized, but in that case, it can be said that the sensitivity of the OASLM can be controlled.

[0067]

According to the present invention, the threshold value of the OASLM can be temporally and spatially controlled using the bias light as described above. Conventionally, threshold processing that changes temporally or spatially has been fetched by a computer or the like, and thus required a huge amount of calculation time. However, according to the present invention, threshold processing can be performed on optical information as it is as optical information, so that threshold processing can be realized very quickly and easily, and by setting an optimal threshold,
A high-performance optical pattern recognition device can be realized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of an optical pattern recognition device according to the present invention.

FIG. 2 is a sectional view showing a structure of an optical writing type spatial light modulator using a ferroelectric liquid crystal.

FIG. 3 is a configuration diagram of a joint transform correlator.

FIG. 4 is a configuration diagram of a matched filter type correlator.

FIG. 5 is a graph showing a change in correlation peak intensity due to irradiation with bias light.

FIG. 6 is a graph showing a change in full width at half maximum of a correlation peak due to irradiation with bias light.

FIG. 7 is a configuration diagram of another embodiment of the optical pattern recognition device according to the present invention.

FIG. 8 is a configuration diagram of another embodiment of the optical pattern recognition device according to the present invention.

FIG. 9 is a configuration diagram of another embodiment of the optical pattern recognition device according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 writing laser 2 writing beam expander 3 film 4 writing lens 5 FLC-OASLM 6 reading laser 7 reading beam expander 8 polarizing beam splitter 9 reading lens 10 light receiving element 11 auxiliary light source 12 diffuser plate Reference Signs List 13 lens 14 liquid crystal TV for bias light 15 lens for bias light 16 mirror 17 half mirror 18 image memory 19 drive circuit for FLC-OAASLM 20 computer 201 beam splitter 202, 203 mirror 204 reflective liquid crystal light valve 301 shutter 302 beam splitter 303 BSO Crystal 304 Liquid crystal TV 601, 602 Half mirror 603 Mirror 604 Input liquid crystal TV 605 CRT 606 Bias light imaging lens 701 Beam splitter 702, 703 Miraー 704 Reading film 705 Fourier transform lens 801 Reference light half mirror 802 Beam splitter

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-280179 (JP, A) JP-A-3-110609 (JP, A) JP-A-3-204625 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G02B 27/46 G06T 7/00

Claims (4)

(57) [Claims] 1. An optical pattern recognition device for automatically recognizing or measuring a required pattern on a two-dimensional image obtained from an image pickup means, comprising: an optical writing type spatial light modulator; Writing light irradiating means for irradiating writing light for writing an image on the optical modulator; reading light irradiating reading light for reading an image recorded or displayed on the optical writing type spatial light modulator Means, bias light irradiating means for irradiating the optical writing type spatial light modulator with bias light, and bias light adjusting means for changing at least one of the irradiation time or light intensity of the bias light, The optical pattern, wherein the irradiation time of the writing light and the irradiation time of the bias light respectively correspond at least a predetermined time to a writing operation time of the optical writing type spatial light modulator. Recognition device. 2. The method according to claim 1, wherein the bias light irradiating means reflects or transmits an element for presenting an image by a reflectance distribution or a transmittance distribution, and an intensity of the element by reflecting or transmitting the element for presenting an image by the reflectance distribution or the transmittance distribution. reading,
A light source for irradiating the intensity distribution as a bias light intensity distribution to the optical writing spatial light modulator; and an imaging lens for imaging the bias light intensity distribution on the optical writing spatial light modulator. The optical pattern recognition device according to claim 1, wherein: 3. An element for displaying an incoherent image as a bias light intensity distribution, an imaging lens for forming an image of the bias light intensity distribution on an optical writing spatial light modulator. 2. The optical pattern recognition device according to claim 1, comprising: 4. The apparatus according to claim 1, wherein said bias light irradiating means is combined with a reading light irradiating means for reading an image recorded or displayed on said optical writing type spatial light modulator. Optical pattern recognition device.