JP3210447B2 - Optical object extraction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in the field of optical information processing, for example, for extracting a specific object or character from an image containing many objects such as landscapes and characters. Object extraction device.

[0002]

2. Description of the Related Art One of methods for extracting a target pattern from an image (hereinafter, referred to as an input image) containing a pattern of a large number of objects and characters such as everyday scenes seen by humans. , There is a matched filtering method.
FIG. 2 is a schematic configuration diagram showing a configuration of an optical system using a conventional matched filtering method. In the matched filtering method, a Fourier transform image of the input image displayed on the image display device 14 is formed on the rear focal plane of the Fourier transform lens 15 and is incident on the matched filter of the target pattern arranged at the rear focal position. When the transmitted light is further Fourier-transformed by the Fourier transform lens 18, when the target pattern is present in the input image, a correlation spot representing a high correlation is formed on the rear focal plane of the Fourier transform lens 18 on the screen. This is a method in which the position of the target pattern in the input image can be known from the position of the target pattern. At this time, a hologram in which the Fourier transform of the intensity distribution of the target pattern is recorded in the form of an interference fringe with the reference light is generally used for the matched filter 21. Normal,
The light beam 12 emitted from the laser 11 is spread by the beam expander 13 into a substantially parallel light beam, and a correlation spot appears on the screen 19 through the image display device 14 as described above. The data is processed by the computer 17.

However, in this method, when a hologram is used as a filter, it is necessary to create a filter for each target pattern to be searched, the tolerance for the filter alignment is extremely small, and a positional deviation of several μm occurs. There is a problem that performance may be significantly reduced. Further, since the output image in this method is only a bright light point which is a correlation spot, when performing processing such as another pattern recognition after extracting an object, the output image is directly input to another processing. I couldn't use it. There is also a method that uses a spatial light modulator that can change the target pattern to be searched in real time without using a hologram as a filter.However, with the current spatial light modulator, interference fringes having the same fine pitch as a hologram can be obtained. There is a problem that there is no drawing ability, and the performance of the optical object extracting apparatus is considerably inferior.

As another method for extracting a target pattern from an input image, there is a template matching method used for image processing software of a computer.
This template matching method is a method of moving a target pattern in an input image to search for a best matching place. This method includes a residual sequential test method, a method using a cross-correlation coefficient, and the like. However, each of these methods basically has to scan a target pattern in an input image, which is time-consuming. This is a problem that appears more noticeably as the number of pixels increases.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and is a matched filter which draws interference fringes such as holograms which must be manufactured for each target pattern to be extracted. , The alignment of the optical system is relatively easy, the target pattern can be extracted from the input image as it is, not as a correlation spot, and scanning of the target pattern is not required. It is an object of the present invention to provide an optical object extracting device capable of processing time.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned technical problems, and comprises a light source that emits at least a coherent light beam; an input image having an intensity transmittance or a reflectance distribution. First image display means for displaying and providing an intensity distribution to the light beam; a first Fourier transform lens for optically Fourier transforming the intensity distribution of the light beam transmitted or reflected by the first image display means A Fourier transform image creating means for creating a Fourier transform image of the target pattern; and a Fourier transform image of the target pattern arranged on the Fourier transform surface of the first Fourier transform lens and obtained by the Fourier transform image creating means. Is displayed as an intensity transmittance or reflectance distribution, and a spatial light modulator that gives an additional intensity distribution to the light flux, and the intensity of the light flux transmitted or reflected by the spatial light modulator A second Fourier transform lens for optically further Fourier transforming the cloth; and imaging means for capturing an output image obtained by Fourier transform by the second Fourier transform lens; the captured output image Is displayed again as an input image of the first image display means,
Provided is an optical object extraction device, which forms a feedback loop that repeats the series of processing steps a plurality of times.

In the course of displaying the output image picked up by the image pickup means again as an input image of the first image display means, a density conversion means for improving the contrast of the output image substantially in real time is provided. Is preferred.
Further, the Fourier-transformed image creating means includes a light source that emits a coherent light beam, and a second pattern that gives an intensity distribution to the light beam by displaying the target pattern as an intensity transmittance or a reflectance distribution.
, A third Fourier transform lens for optically Fourier transforming the intensity distribution of the light beam transmitted or reflected from the second image display means, and a target pattern obtained by the third Fourier transform lens. It is preferable that the imaging device be configured to include an imaging unit that captures a Fourier transform image.

Further, the spatial light modulator is an optical writing type spatial light modulator, and the Fourier transform image forming means is
A light source that emits a coherent light beam, a second image display unit that displays the target pattern as an intensity transmittance or a reflectance distribution to give an intensity distribution to the light beam, and a light transmitted or reflected from the second image display unit. And a third Fourier transform lens for optically Fourier transforming the intensity distribution of the light beam, wherein a writing surface of an optical writing type spatial light modulator is arranged on the Fourier transform surface of the third Fourier transform lens. Is preferred. Further, it is preferable that the Fourier transform image of the target pattern is displayed on the spatial light modulator as an image binarized by an appropriate threshold value substantially in real time.
Further, it is preferable that the optical writing type spatial light modulator performs a processing operation of binarizing an image written from a writing surface with a threshold value and displaying the image.

[0009]

In the configuration of the optical object extracting apparatus of the present invention as described above, the coherent light beam emitted from the light source enters the first image display means. In the first image display means, the input image is displayed with the intensity transmittance or reflectance distribution, so that the incident coherent light flux is modulated into the intensity distribution of the input image, and is transmitted as reflected light or reflected light. One image display means is emitted. The modulated coherent light beam passes through the first Fourier transform lens and forms a Fourier transform image of the input image on the focal plane. On the other hand, a Fourier-transformed image of the target pattern is created by the Fourier-transformed image creating means, and is displayed on the spatial light modulator with an intensity transmittance or reflectance distribution. Since this spatial light modulator is disposed on the focal plane of the first Fourier transform lens, the Fourier transform image of the input image enters the spatial light modulator and is further modulated by the intensity distribution of the Fourier transform image of the target pattern. And
The output of the product of the Fourier transform image of the input image and the Fourier transform image of the target pattern is transmitted or reflected.

As described above, since only a Fourier transform image is drawn on this spatial light modulator and no interference fringes are drawn, the use of a hologram or the like for drawing interference fringes used by a method such as a matched filter method is not possible. There is no need. for that reason,
This arrangement of the spatial light modulator does not require strictness as compared with a matched filter. Moreover, when the target pattern is changed, it is only necessary to change the Fourier transform image of the target pattern drawn on the spatial light modulator, and this can be easily executed by using a computer or the like. Thereafter, the coherent light beam is again Fourier-transformed by the second Fourier transform lens disposed behind the spatial light modulator by its own focal length, and becomes an output image. This output image is a result of the cross-correlation operation between the input image and the target pattern, and it can be said that a portion having a spatial frequency component similar to the target pattern in the input image remains. Therefore, by performing the process of capturing the output image by the imaging unit and displaying it again as the input image on the first image display unit a plurality of times, only the target pattern portion in the input image is output to the end. After all, the target pattern can be extracted from the input image. In addition, the output image is not a light spot such as a correlation spot but an image of the extracted target pattern itself. Further, in the above-described processing steps, the entire input image is simultaneously performed in parallel with one coherent light beam, so that scanning time such as template matching is not required.

[0011] By performing processing steps such as improving the contrast of an output image picked up by the image pick-up means using a gray scale modulating means such as an image processing device, the efficiency of extracting a target pattern is improved, and the contrast ratio of the image passing through an optical system is improved. Can be reduced. Further, the Fourier-transformed image creating means is used to detect that the coherent luminous flux emitted from the light source is incident on the second image display means in which the target pattern is displayed with a high transmittance or reflectance distribution, and the incident coherent luminous flux is used as the target. The intensity distribution of the pattern is modulated and emitted as transmitted or reflected light, and the modulated coherent light beam passes through the third Fourier transform lens, creates a Fourier transform image of the target pattern on the focal plane, and captures the pattern By means of imaging by means, the Fourier transform image of the target pattern can be created optically at high speed and easily simply by displaying the target pattern, and the change of the target pattern is performed by the second image processing means. Can be performed simply by changing the image to be displayed.

Further, by using a light-writing type spatial light modulator and making the Fourier transform image forming means write the Fourier transform image of the target pattern directly into the spatial light modulator, Just display
A Fourier transform image of the target pattern can be created optically at higher speed and more easily.

Further, the Fourier-transformed image of the target pattern is stored in the spatial light modulator substantially in real time.
By displaying an image binarized by an appropriate threshold value, it is possible to improve the contrast ratio of the target pattern remaining in the output image. Further, by reducing the contrast ratio of the target pattern by performing an operation of binarizing the image written from the writing surface with a threshold value and displaying the image, the optical writing type spatial light modulator may be used. Improvements can be made.

Next, the optical object extraction apparatus of the present invention will be described in more detail with reference to the following examples.
The present invention is not limited by them.

[0015]

Embodiment 1 FIG. 1 is a schematic configuration diagram showing the configuration of an embodiment of an optical object extracting apparatus according to the present invention. Now, the coherent light beam 12 emitted from the laser 11 is expanded to an appropriate light beam diameter by the beam expander 13, collimated, and incident on the image display device. Image display device 14
In the figure, an input image to be extracted as an object is drawn in the transmittance distribution of the intensity pattern, and the light beam 12 is transmitted to read the input image. The light flux 12 passes through the Fourier transform lens 15 and forms a Fourier transform image of the input image on a spatial light modulator 16 arranged on the focal plane of the Fourier transform lens 15. On the other hand, the computer 17 previously stores a Fourier transform image of the target pattern to be extracted, and displays the intensity pattern of the Fourier transform image of the target pattern on the spatial light modulator 16 as a transmittance distribution. Therefore, when the Fourier transform image of the input image is transmitted through the spatial light modulator 16, the Fourier transform image is modulated by the intensity pattern of the Fourier transform image of the target pattern, and the product of the corresponding spatial frequency components of the input image and the target pattern is obtained. Is performed. Thereafter, the light flux 12 is transmitted through the Fourier transform lens 18 and subjected to inverse Fourier transform, and the result of the cross-correlation operation between the input image and the target pattern is output on the screen 19. Then, after the screen 19, the imaging device 20
Is arranged, captures an output image formed on the screen 19, and sends it to the computer 17.

Specifically, the output image is an image in which an image having a small correlation with the target pattern in the input image is deleted.
The part of the input image that has a high degree of correlation with the target pattern
A portion which is output without a decrease in the contrast ratio, and conversely, has little correlation with the target pattern, is a portion which has been output with almost no contrast ratio. Therefore, the output image is captured by the imaging device 20, displayed again on the image display device 14 as an input image, and if the above series of processing steps are repeated several times, the degree of correlation with the target pattern in the input image is low. The portion disappears, and only the same pattern as the target pattern remains in the output image to the end, so that the target can be extracted. The number of repetitions is controlled to an appropriate number by a program of the computer 17. The result of extracting the target is output to a CRT or the like in the computer.

As the image display device 14 used here, a liquid crystal panel which is a general electric address type spatial light modulator can be used. Here, the spatial light modulator 16
For example, a liquid crystal panel or the like, which is a general electric address type spatial light modulator, can be used. Further, the imaging device 2
For 0, a CCD camera or an imaging tube can be used.

Further, a circular mask or the like having an appropriate radius centered on the optical axis is disposed on the spatial light modulator 16 to perform processing for cutting off a target pattern, an input image, or both images near the optical axis. Is also good. As a result, low spatial frequency components that are almost common to all patterns are cut, and the target pattern can be extracted more efficiently. In addition to the use of the mask, there is a method of preventing the image near the optical axis from being displayed when the Fourier transform image of the target pattern is displayed on the image display device 14 by the computer 17.

Furthermore, if the binarized image of the intensity pattern of the Fourier transform image of the target pattern is displayed on the spatial light modulator 16, the Fourier transform portion of the input image that matches the Fourier transform image of the target pattern will be spatially modulated. Since the light is transmitted without being affected by the light modulator, a decrease in the contrast ratio of the target pattern remaining in the output image can be prevented.
As such a spatial light modulator, an electric address type using a ferroelectric liquid crystal can be used. In particular, a spatial light modulator using a ferroelectric liquid crystal is suitable because not only binarization of an image but also high resolution and high contrast can be easily obtained in principle. In addition, if the binarization process is performed using an image processing device or the like, the same can be achieved using a general electric address type spatial light modulator.

[0020]

[Embodiment 2] Fig. 3 is a schematic diagram showing the structure of another embodiment of the optical object extracting apparatus of the present invention. This embodiment is characterized in that a Fourier transform image of a target pattern to be displayed on the spatial light modulator 16 is optically obtained, and that the output image is subjected to shading conversion by an image processing device. That is, the coherent light beam 12 emitted from the laser 11 is expanded to an appropriate light beam diameter by the beam expander 13, collimated, and incident on the half mirror 31, where the light beam 1 is emitted.
The light beam is divided into two light beams, 2a and 12b. Luminous flux 12
a is incident on the image display device 32. Image display device 32
In FIG. 7, an intensity pattern of a target pattern to be extracted stored in the computer 17 is drawn as a transmittance distribution, and the light beam 12a is transmitted to read the target pattern. Thereafter, the luminous flux 12a is converted to a Fourier transform lens 33.
And a Fourier-transformed image of the target pattern is formed on the screen 34 arranged on the focal plane. This image is
The image is captured by the imaging device 35. Here, the image display device 32
In the target pattern displayed in step (1), the target pattern may be directly imaged by the imaging device, and the image may be displayed.

On the other hand, the light flux 12b is incident on the image display device 14 after being deflected by the mirror 36. On the image display device 14, the input image to be extracted is drawn in the transmittance distribution of the intensity pattern, the light flux 12b is transmitted, and the input image is read. The light flux 12b passes through the Fourier transform lens 15, and forms a Fourier transform image of the input image on a spatial light modulator 16 arranged on the focal plane of the Fourier transform lens 15. Since the spatial light modulator 16 displays the Fourier transform image of the target pattern imaged by the imaging device 35 with the transmittance distribution of the intensity pattern, the Fourier transform of the target pattern is performed when the light flux 12b is transmitted. Modulation is performed by the intensity pattern of the image, and the product of the corresponding spatial frequency components of the input image and the target pattern is calculated. After that, the light flux 12b passes through the Fourier transform lens 18 and is again subjected to Fourier transform.
The result of the cross-correlation operation between the input image and the target pattern is output on 9. Specifically, the output image is an image in which an image having a low correlation with the target pattern in the input image has been removed, and a portion having a high degree of correlation with the target pattern in the input image has a low contrast ratio. Output, and conversely,
Portions having little correlation with the target pattern are output with almost no contrast ratio.

Thereafter, the output image is picked up by the image pickup device 20 and input to the image processing device 37 for improving the contrast ratio. Using the image processing device 37, various controls on the degree of target object extraction can be performed. For example, processing is performed so that a portion having a small contrast ratio is smaller and a portion having a large contrast ratio is larger. Also, if processing is performed to increase the contrast ratio as a whole, the effect of extracting the target pattern in the final output will be more reliable, and it will be possible to extract a pattern similar to the target pattern. I can give it. In addition, the image processing device 37 can be used for the purpose of correcting the deterioration of the image due to the input image having passed through the optical system.

The output pattern subjected to appropriate processing by the image processing device 37 is used as an input image again, and
4 and the above-described series of processing steps are repeated several times, a portion having low correlation with the target pattern in the input image disappears, and only the same pattern as the target pattern or image processing is performed. Depending on the processing method of the device 37, the similar pattern remains in the output image to the end, and the target object can be extracted. The number of repetitions is controlled to an appropriate number by a program of the computer 17. In addition, the extraction result of the object is stored in the CR in the computer.
Output to T etc.

As the image display devices 14 and 32 used here, a liquid crystal panel or the like which is a general electric address type spatial light modulator can be used. Here, as the spatial light modulator 16, a liquid crystal panel or the like, which is a general electric address type spatial light modulator, can be used. Further, as the imaging devices 20 and 35, a CCD camera, an imaging tube, or the like can be used. In this embodiment, the light flux 1
Although the laser beam 2 is divided into two by the half mirror 31, there is no problem even if two lasers and two beam expanders are prepared and two light beams 12a and 12b are separately formed.

[0025]

Embodiment 3 FIG. 4 is a block diagram showing the configuration of still another embodiment of the optical object extracting apparatus of the present invention. This embodiment is characterized in that an optical writing type device typified by a liquid crystal light valve is used as the spatial light modulator.
Coherent light beam 42 emitted from semiconductor laser 41
Are collimated by the collimator lens 43 and enter the image display device 32. On the image display device 32, the intensity pattern of the target pattern to be extracted stored in the computer 17 is drawn as a transmittance distribution, the light beam 42 is transmitted, and the target pattern is read.
Thereafter, the light beam 42 passes through the Fourier transform lens 33,
Optically-written spatial light modulator 44 disposed on the focal plane
A Fourier transform image of the target pattern is formed on the writing surface of. Accordingly, in the light writing type spatial light modulator 44, for example, in the case of a liquid crystal light valve, an electric field is generated in the liquid crystal due to a resistance change of the photoconductor layer in the light valve according to the light intensity distribution of the incident Fourier transform image. Is applied to change the liquid crystal partial arrangement, and a Fourier transform image of the target pattern is written.

On the other hand, the coherent light beam 46 emitted from the semiconductor laser 45 is collimated by the collimator lens 47 and enters the image display device 14. On the image display device 14, an input image to be extracted for an object is drawn in the transmittance distribution of the intensity pattern, and the light beam 46 is transmitted to read the input image. The modulated light flux 46 is reflected by the polarization beam splitter 48 and is applied to the Fourier transform lens 1.
5 is incident. At this time, in order to maximize the reflectance of the polarizing beam splitter 48, the image display device 14
May be changed to a linear polarization state (usually, an s-polarization state) corresponding to the total reflection of the polarization beam splitter. After passing through the Fourier transform lens 15, the Fourier transform image of the input image is incident on the readout surface of the optical writing type spatial light modulator 44 disposed on the focal plane and is reflected. The Fourier transform image of the target pattern as described above is written in the device 44, and the structure of the liquid crystal is changed. Therefore, the Fourier transform image of the input image corresponding to (corresponding to) the Fourier transform image of the target pattern. Part is
The polarization state changes according to the pattern written in the optical writing type spatial light modulator 44, and the reflected light passes through the Fourier transform lens 15 again and enters the polarization beam splitter 48 again. Here, the optical writing type spatial light modulator 4
The linearly polarized light component changed in accordance with the Fourier transform image of the target pattern written in 4, and a component (usually a p-polarized light component) orthogonal to that before the change passes through the polarizing beam splitter 48 as it is and reaches the screen 19. The resulting image is the output image.

This output image is the result of a cross-correlation operation between the input image and the target pattern. Specifically, the output image is an image in which the input image has a low correlation with the target pattern in the input image, and a portion having a high degree of correlation with the target pattern in the input image has a low contrast ratio. ,
A portion that is output and, conversely, has little correlation with the target pattern is output with almost no contrast ratio. Therefore, the output image is captured by the imaging device 20 and displayed again on the image display device 14 as an input image.
If the above series of processing steps are repeated several times, portions having low correlation with the target pattern in the input image disappear, only the same pattern as the target pattern remains in the output image to the end, and extraction of the target object Can be done. The number of repetitions is
An appropriate number of times is controlled by a program of the computer 17. In addition, the extraction result of the object is stored in the computer 17.
Can be output to a CRT or the like. As the image display devices 14 and 32 used here, a liquid crystal panel or the like, which is a general electric address type spatial light modulator, can be used. Further, as the imaging device 20, a CCD camera, an imaging tube, or the like can be used.

In this embodiment, an optical writing type spatial light modulator is used.
A liquid crystal panel combined with a photoconductor layer is generally used, and a liquid crystal panel using a nematic-type liquid crystal is practically suitable. The Fourier transform image of the target pattern is written to the optical writing type spatial light modulator 44 as a gray level or a binarized image. When the image is written as a binary image, the contrast ratio of the target pattern in the output image is obtained. The effect is obtained that the decrease of the temperature is suppressed. Such a spatial light modulator has not only binarization of an image but also a high resolution in principle,
This is preferable because the contrast ratio is high.

Further, as an optical address type spatial light modulator, BSO (bismuth silicon oxide; Ba ₁₂
A medium using a medium having a photoinduced refractive index change such as SiO ₂₀ ) can also be used. In particular, in the BSO material, writing and reading are performed simultaneously by using visible light from a short wavelength having high sensitivity as writing light and using light in a wavelength range from red having low writing sensitivity to an infrared region as reading light. be able to. However,
The BSO material can be used in a reflection type by using a reflection plate, but is usually used as a transmission type in many cases. In this case, it is necessary to change the incident direction of the reading light incident on the BSO material, but this is not the essence of the present invention.

[0030]

As described above, the above-described effects are obtained by the optical object extracting apparatus of the present invention. Summarizing them has the following remarkable technical effects. First, there is no need to use a matched filter that draws interference fringes such as holograms, which must be produced for each target pattern to be extracted, and the alignment of the optical system is relatively easy. An extraction device could be provided. Secondly, there has been provided an optical target object extracting apparatus capable of extracting a target pattern from an input image without being a correlation spot, but as it exists in the input image. Third, there has been provided an optical target object extracting apparatus which can perform processing in a short time because there is no need to scan a target pattern.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing the configuration of an embodiment of an optical object extraction apparatus according to the present invention.

FIG. 2 is a schematic configuration diagram showing an optical system of a conventional matched filtering method.

FIG. 3 is a configuration diagram showing a configuration of another embodiment of the optical object extracting apparatus of the present invention.

FIG. 4 is a configuration diagram showing the configuration of still another embodiment of the optical object extracting apparatus of the present invention.

[Explanation of symbols]

Reference Signs List 11 laser 12, 12a, 12b, 42, 46 light flux 13 beam expander 14, 32 image display device 15, 18, 33 Fourier transform lens 16 spatial light modulator 17 computer 19, 34 screen 20, 35 imaging device 21 matched filter 31 Half mirror 36 Mirror 37 Image processing device 41, 45 Semiconductor laser 43, 47 Collimator lens 44 Optical writing type spatial light modulator 48 Polarizing beam splitter

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-174010 (JP, A) JP-A-4-171510 (JP, A) JP-A-4-240625 (JP, A) JP-A-4-174 240624 (JP, A) JP-A-4-255832 (JP, A) JP-A-3-259128 (JP, A) JP-A-3-251828 (JP, A) JP-A-2-293827 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G02B 27/46 G02F 3/00 502 G06E 3/00

Claims (6)

(57) [Claims] 1. A light source for emitting a coherent light beam, first image display means for displaying an input image with an intensity transmittance or a reflectance distribution and giving an intensity distribution to the light beam, and the first image display A first Fourier transform lens for optically Fourier transforming the intensity distribution of the light flux transmitted or reflected by the means, and a Fourier transform image creating means for creating a Fourier transform image of a pattern to be extracted (hereinafter referred to as a target pattern). Displaying the Fourier transform image of the target pattern, which is arranged on the Fourier transform surface of the first Fourier transform lens and obtained by the Fourier transform image creating means, as an intensity transmittance or a reflectance distribution, And a second Fourier for optically further Fourier transforming the intensity distribution of the light beam transmitted or reflected by the spatial light modulator. A conversion lens, and imaging means for capturing an output image obtained by Fourier transform by the second Fourier transform lens, wherein the captured output image is again used as an input image of the first image display means. An optical object extracting apparatus for displaying and forming a feedback loop for repeating the series of processing steps a plurality of times. 2. A density converter for improving a contrast of an output image substantially in real time while an output image picked up by said image pickup means is displayed again as an input image of said first image display means. 2. The optical object extracting apparatus according to claim 1, further comprising means. 3. A Fourier-transformed image creating means, comprising: a light source for emitting a coherent light beam; and a second image for displaying an object pattern as an intensity transmittance or a reflectance distribution to give the light beam an intensity distribution. Display means; a third Fourier transform lens for optically Fourier transforming intensity means of a light beam transmitted or reflected from the second image display means; and a target pattern obtained by the third Fourier transform lens. The optical object extracting apparatus according to claim 1, further comprising: an imaging unit configured to capture a Fourier transform image. 4. The spatial light modulator is an optical writing type spatial light modulator, and the Fourier transform image creating means includes a light source for emitting a coherent light beam and an intensity transmittance or a target pattern. A second display which gives an intensity distribution to the light flux by displaying it as a reflectance distribution
And a third Fourier transform lens for optically Fourier transforming the intensity distribution of the light flux transmitted or reflected from the second image display means. 3. The optical object extracting apparatus according to claim 1, wherein a writing surface of the optical writing type spatial light modulator is arranged on a Fourier transform surface. 5. The spatial light modulator according to claim 1, wherein the Fourier transform image of the target pattern is displayed as an image binarized by an appropriate threshold value in substantially real time. 4. The optical object extraction apparatus according to any one of 3. 6. The optical writing type spatial light modulator according to claim 4, wherein said optical writing type spatial light modulator performs a processing operation of binarizing an image written from a writing surface with a threshold value and displaying it. An optical object extraction apparatus according to claim 1.