JP2878618B2 - 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. Optical object extraction apparatus.

[0002]

2. Description of the Related Art A specific pattern to be searched (hereinafter referred to as a target pattern) is selected from among images (hereinafter, referred to as input images) including patterns of a large number of objects and characters such as everyday scenes seen by humans. ) 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, an input image is displayed on an image display device 14, and a Fourier transform image of the input image is formed on a back focal plane of a Fourier transform lens 15,
The incident light is incident on the matched filter 25 of the target pattern arranged at the rear focal position, and the transmitted light is converted by the Fourier transform lens 1.
When the target pattern is present in the input image, a correlation spot showing a high correlation appears on the back focal plane of the Fourier transform lens 18 on the screen 19, and the position of the target spot in the input image depends on the position. This is a method by which the position of the target pattern can be known. 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 as the matched filter 25.

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 in that there is no writing ability and the performance of the optical extraction device 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.

In order to solve the above-mentioned problem, a method using a Fourier transform image of an input image and a Fourier transform image of a target pattern (Japanese Patent Laid-Open No. 6-162259).
However, in the proposed method, a feedback loop is formed by inputting the output image of the device again as an input image to the device, but at this time, if the feedback process is not performed many times, There is a problem that only the target pattern cannot be extracted from the input image.

[0006]

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. , And the alignment of the optical system is relatively easy, and the target pattern can be extracted from the input image as it is, not as a correlation spot, and the target pattern can be extracted from the input image with a small number of feedbacks. It is an object of the present invention to provide an optical object extracting apparatus that can perform extraction in a short time.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above technical problems, and comprises: a) a light source for emitting a coherent light beam; and b) an intensity transmittance or reflection of an input image. First image display means for giving an intensity distribution to the luminous flux, displayed as a distribution of rates, and c) optically Fourier-transforming the intensity distribution of the luminous flux transmitted or reflected by the first image display means. A first Fourier transform lens, d) Fourier transform image creating means for creating a Fourier transform image of a pattern to be extracted (hereinafter referred to as a target pattern), and e)
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, is displayed as an intensity transmittance or a reflectance distribution, and is displayed on the light beam. A spatial light modulator that further provides an intensity distribution; f) a second Fourier transform lens that optically further Fourier transforms the intensity distribution of a light beam transmitted or reflected by the spatial light modulator; and g) the second Imaging means for imaging an output image obtained by performing a Fourier transform by a Fourier transform lens, whereby the captured output image is displayed again as an input image of the first image display means. In the optical object extraction device forming a feedback loop for repeating the above series of processing steps, a) the output image captured by the In the course of displaying as an input image of the image display means, the input image displayed on the first image display means is compared with the output image obtained by being input to the optical object extracting device, and each of the images is compared. Density change measuring means for measuring the amount of change in the contrast of the portion; b) the contrast of each portion of the input image to be displayed again on the first image display means, And a density operation means for performing an emphasis operation in a part where the output from the density change measurement means is equal to or less than a predetermined value, which is suppressed in a portion where the density change is equal to or more than a predetermined value. An optical object extracting apparatus is provided.

The Fourier-transformed image creating means includes a light source for emitting a coherent light beam, and a second image display means for displaying a target pattern as an intensity transmittance or a reflectance distribution to give the light beam an intensity distribution. A third Fourier transform lens for optically Fourier transforming the intensity of the light flux transmitted or reflected from the second image display means, and a Fourier transform image of the target pattern obtained by the third Fourier transform lens. What is comprised from an imaging means to image is suitable.

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.

[0010]

In the configuration of the optical object extracting apparatus of the present invention as described above, the input image displayed on the first image display means of the optical object extracting apparatus, the output image picked up by the image pickup means, Is input to the concentration change measuring means. And
In the density change measuring means, a comparison process is performed between the input image and the output image by a subtraction operation or the like, and an image having a difference between the two images is obtained. This difference image reflects the degree of change in contrast of the output image from the input image. The part similar to the target pattern in the input image is
Since the change is small, the output is small, and a pattern with little similarity has a large change. The result of the concentration change measurement means is
Output to the density operation means.

In the density operating means, the contrast of each part constituting the input image to be displayed again on the first image display means is changed from the output image picked up by the image pick-up means. In the measuring means, the contrast is suppressed for the portion where the value larger than the preset value is measured, and the contrast is enhanced for the portion where the value smaller than the preset value is measured. Accordingly, a pattern having a large decrease in contrast has a small similarity to the target pattern, and a pattern having a small decrease in the contrast ratio has a large similarity to the target pattern. Even when displayed, a pattern with a high contrast ratio is clearly displayed, but a pattern with a small similarity is displayed with a low contrast ratio. That is, the change in the captured output image from the input image is emphasized by the density change measuring unit and the density operating unit, and displayed again by the first image display unit. The target pattern can be extracted from the input image by the number of times.

Further, according to the present invention, the coherent light beam emitted from the light source is incident on the second image display means in which the target pattern is displayed with a strong transmittance or reflectance distribution. Modulated to the intensity distribution of the pattern, emitted as transmitted light or reflected light, 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 converts the pattern. By taking the method of imaging,
By simply displaying the target pattern, a Fourier transform image of the target pattern can be created optically at high speed and easily.
The change of the target pattern can be performed only by changing the image displayed on the second image processing means.

Further, by using an optical writing type spatial light modulator and writing the Fourier transform image of the target pattern directly to the spatial light modulator by using the Fourier transform image forming means, 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 displayed on the spatial light modulator in a substantially real-time manner as an image binarized by an appropriate threshold, so that the target pattern remaining in the output image is displayed. Can be reduced. Also, by improving the optical writing type spatial light modulator to perform an operation of binarizing an image written from the writing surface with a threshold value and displaying the image, the reduction of the contrast ratio of the target pattern can be improved. Can do it.

Next, the optical object extracting 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.

[0016]

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. The coherent light beam 12 emitted from the laser 11 is expanded to an appropriate light beam diameter by a beam expander 13 and collimated.
The light enters the image display device 14. In the image display device 14,
The input image to be extracted is drawn with 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, a Fourier transform image of the target pattern to be extracted is stored in the computer 17 in advance, and the intensity pattern of the Fourier transform image of the target pattern is displayed 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 converted to a Fourier transform lens 18.
, And undergoes an 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 2
0 is arranged to capture an output image formed on the screen 19 and send it to the computer 17.

More 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 input to the intensity change detection device 21 and the density conversion device 22.

FIG. 3 is an explanatory diagram showing an example of an input image, FIG. 4 is an explanatory diagram showing an example of a target pattern, and FIG. 5 is an explanatory diagram showing an example of an output image. .
The line thickness of the pattern in the figure reflects the strength of the contrast. When the input image shown in FIG. 3 is displayed on the image display device 14 and the Fourier transform image of the target pattern shown in FIG.
An output image as shown in FIG. 5 is captured. In the output image shown in FIG. 5, a circle pattern 50 having a high degree of correlation with the target pattern of FIG. 4 is output with a small change in contrast ratio from the input image, and a circle having a low degree of correlation with the target pattern shown in FIG. Those other than the pattern 50 are output in a state where the change in the contrast ratio from the input image is large. The result of extracting the target is output to a CRT or the like in the computer.

The density change measuring device 21 used here includes:
Output image captured by imaging device 20 and image display device 14
Are input and the subtraction of the two input images is performed. Here, FIG. 6 is an explanatory diagram showing an example of an output image of the density change measuring device 21 when the input image shown in FIG. 3 and the output image shown in FIG. 5 are input. The thickness of the line in the figure indicates the magnitude of the output from the density change measuring device 21. The result of the difference operation as shown in FIG. 6 reflects the degree of change in contrast of the output image from the input image. Information on the result of the subtraction is output to the density operation device 22.

The density operation device 22 receives information on the result of subtraction between the output image captured by the imaging device 20 and the image from the density change measuring device 21 and is based on the information on the result of image subtraction. The operation of contrast of the output image is performed. At this time, for a portion where the output of the density change measuring device 21 is larger than a preset value, that is, a portion where the output image greatly changes from the input image, the contrast is suppressed, and the output of the density change measuring device 21 is set in advance. The portion smaller than the value, that is, the portion where the change of the output image from the input image is small, is subjected to contrast enhancement, and then displayed again on the image display device 14 to be subjected to feedback processing.

FIG. 7 is an explanatory diagram showing an example of the output of the density operation device 22. The thickness of the line in the figure reflects the strength of the contrast. When a constant value that is a boundary between contrast enhancement and suppression is set to a predetermined value, as shown in FIG. 7, the circular pattern 60 having a small output of FIG.
It becomes a circular pattern 70 with enhanced contrast,
The pattern other than the circular pattern 70 is a pattern in which the contrast is suppressed, as shown in FIG. Thereafter, the image output from the density operation device 22 is displayed again on the image display device 14 as an input image, and the above series of processing is repeated several times. The portion where the target pattern is low disappears, and only the same pattern as the target pattern remains in the output image to the end, so that the target object can be extracted.

In the input image shown in FIG. 3, a circular pattern 30 is extracted. At this time, the concentration change measuring device 21
The change in the contrast of the output image captured by the imaging device 20 from the input image is emphasized by the density operation device 22 and displayed on the image display device 14, so that the density change measurement device 21 and the density operation device 22 are displayed. Is used, the target object can be extracted with a smaller number of repetitions than when no contrast enhancement or the like is performed. 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.

Further, as the image display device 14 used here, a liquid crystal panel or the like which is a general electric address type spatial light modulator can be used. 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. Here, a CCD camera, an imaging tube, or the like can be used as the imaging tube 20.

Furthermore, a circular mask or the like having an appropriate radius centered on the optical axis is arranged on the spatial light modulator 16,
A process of shaving the target pattern, the input image, or images near both optical axes may be performed. As a result, low spatial frequency components that are almost common to any pattern are cut, and the target pattern can be extracted more efficiently. In addition to using a mask, there is a method of preventing the image near the optical axis from being displayed when displaying the Fourier transform image of the target pattern on the computer 17.

Furthermore, if a binary 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 Since the light is transmitted without being affected by the light modulator, the contrast of the target pattern remaining in the output image can be prevented from lowering. 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.

Further, an image processing device is added to the digital computer for the density change measuring device 21 and the density operating device 22 so that the above-described processing is performed by software, or the same function is performed by using an electronic circuit. It is possible by a method of implementing hardware.

[0028]

[Embodiment 2] Fig. 8 is a schematic configuration diagram showing the configuration 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 obtained optically and that an 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 81, where it is split into two light beams, a light beam 12a and a light beam 12b. Can be The light flux 12a enters the image display device 82. In the image display device 82, the intensity pattern of the 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 light beam 12a transmits through the Fourier transform lens 33, and forms a Fourier transform image of the target pattern on a screen 84 disposed on the focal plane. This image is captured by the imaging device 85. Here, the target pattern displayed on the image display device 82 may be such that the target pattern is directly imaged by the imaging device and the image is displayed.

On the other hand, the light flux 12 b is incident on the image display device 14 after being deflected by the mirror 86. 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 85 in 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 is deleted, and a portion of the input image having little correlation with the target pattern has a low contrast ratio. In contrast, a portion having little correlation with the target pattern is output with almost no contrast ratio.

Thereafter, the output image is output to the density change detecting device 2.
1 and input to the density converter 22 to improve the contrast. This processing is the same as that described in the first embodiment, and a description thereof will not be repeated. Also in the present embodiment, the change in contrast of the output image captured by the imaging device 20 from the input image is emphasized and displayed on the image display device 14 using the density change measurement device 21 and the density operation device 22. ,
Using the density change measuring device 21 and the density operating device 22, the target object can be extracted with a smaller number of repetitions as compared with the case where no contrast enhancement is performed. For example, parts with low contrast are smaller,
Processing is performed so that a portion having a large contrast becomes larger. In addition, if processing is performed to increase the contrast as a whole, the effect of extracting the target pattern more reliably or extracting a pattern similar to the target pattern can be obtained in the final output. be able to. In addition to this, it can also be used for the purpose of correcting image deterioration due to the input image having passed through the optical system.

The number of repetitions is determined by the computer 17
Is controlled to an appropriate number by the above program. The result of extracting the target is output to a CRT or the like in the computer.

As the image display devices 14 and 82 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. In addition, a CCD camera, an imaging tube, or the like can be used as the imaging devices 20 and 85.

In this embodiment, the light beam 12 is divided into two by the half mirror 81. However, two laser beams and two beam expanders are prepared and two light beams 12a and 12b are separately formed. There is no problem with the device.
Furthermore, the concentration change measuring device 21 and the concentration operating device 22
An image processing apparatus can be added to a digital computer, and the above-described processing can be performed by software, or a similar function can be realized by hardware using an electronic circuit.

An optical writing type spatial light modulator is used. As such a spatial light modulator, a combination of a liquid crystal panel and a photoconductor layer is generally used, and a spatial light modulator using a nematic liquid crystal is used. Is practically suitable. The Fourier transform image of the target pattern is written to the optical writing type spatial light modulator in a gray level or a binarized image, but when written in a binary image, the contrast ratio of the target pattern in the output image is calculated. This has the effect of reducing the drop. In such a spatial light modulator, not only binarization of an image but also
It is preferable because the resolution is high in principle and 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.

[0037]

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. That is, first, the change of the captured output image from the input image is determined by the density change measuring unit and the density operating unit.
By emphasizing and displaying again on the first image display means, it is possible to extract the target pattern from the input image with a smaller number of feedbacks compared to the conventional optical target object extracting device. Secondly, there is no need to use a matched filter which draws interference fringes such as holograms which have to be produced for each target pattern to be extracted, and furthermore, an object extracting apparatus which relatively easily positions the optical system. Could be provided. Third, there has been provided an optical target object extracting apparatus capable of extracting a target pattern from an input image as a correlation spot, as it is in the input image. Fourth, there has been provided an optical object extracting apparatus which can perform processing in a short time because there is no need to scan an object 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 an explanatory diagram illustrating an example of an input image according to the present invention.

FIG. 4 is an explanatory diagram showing an example of a target pattern according to the present invention.

FIG. 5 is an explanatory diagram showing an example of an output image according to the present invention.

FIG. 6 is an explanatory diagram showing an example of an output of the concentration change measuring device according to the present invention.

FIG. 7 is an explanatory diagram showing an example of an output of the concentration operation device according to the present invention.

FIG. 8 is a configuration diagram showing a configuration of another embodiment of the optical object extracting apparatus of the present invention.

[Explanation of symbols]

Reference Signs List 11 laser 12, 12a, 12b light flux 13 beam expander 14, 82 image display device 15, 18, 83 Fourier transform lens 16 spatial light modulator 17 computer 19, 84 screen 20, 85 imaging device 21 density change measuring device 22 density operation Apparatus 25 Matched filter 30, 50, 60, 70 Circular pattern 81 Half mirror 86 Mirror

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-3-156582 (JP, A) JP-A-4-110823 (JP, A) JP-A-6-162259 (JP, A) JP-A-7- 160869 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02B 27/46 G06K 9/20 310 G06T 7/00

Claims (1)

(57) [Claims] 1. a) a light source for emitting a coherent light beam; b) first image display means for displaying an input image with a distribution of intensity transmittance or reflectance to give an intensity distribution to the light beam; c. A) 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; and d) a pattern to be extracted (hereinafter referred to as a target pattern).
E) a Fourier transform image creating means for creating a Fourier transform image of: e) a Fourier transform image of a target pattern arranged on the Fourier transform surface of the first Fourier transform lens and obtained by the Fourier transform image creating means; A spatial light modulator, which is displayed as an intensity transmittance or reflectance distribution and gives an additional intensity distribution to the light beam; and f) an optically Fourier transforming the intensity distribution of the light beam transmitted or reflected through the spatial light modulator. A second Fourier transform lens for conversion; and g) imaging means for capturing an output image obtained by Fourier transform by the second Fourier transform lens. An optical object extracting apparatus which displays an input image of the first image display means and forms a feedback loop for repeating the series of processing steps a plurality of times is provided. Te, on the way to display as the input image again said first image display means outputs images captured by a) said imaging means,
Density change measuring means for comparing an input image displayed on the first image display means with an output image obtained by inputting to the optical object extracting device, and measuring a change in contrast of each part of the image. B) comparing the contrast of each part of the input image to be displayed again on the first image display means with the output from the density change measuring means a) being equal to or greater than a predetermined value,
The optical target object extracting apparatus, further comprising: a density operation means for performing an emphasizing operation when the output from the density change measuring means is equal to or less than a predetermined value set in advance.