JPH08271838A - Optical object extracting device - Google Patents

Abstract

PURPOSE: To extract an object pattern from an input image with the small number of feedbacks by displaying changes from the input image of a pickuped output image again on a first image display device while emphasizing them. CONSTITUTION: In this device, a density change measuring means 21 comparing the input image with the output image and measuring change amounts of contrasts of respective parts of the image and a density operating means 22 performing an operation in which contrasts of respective parts of the input image displayed again on a first image display means 14 are suppressed in parts in which outputs from the density change measuring means 21 are equal to or larger than a previously set prescribed value and are emphasized in parts in which the outputs of the density change measuring means 21 are equal to or smaller than a previously set prescribed value are provided in the mid-course displaying the output image photographed by a photographing means 20 again as the input image on the first image display means 14.

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, such as extracting a specific object or character from an image containing many objects such as landscapes or characters. The present invention relates to an optical object extracting device.

[0002]

2. Description of the Related Art A specific pattern to be searched (called a target pattern) from an image (hereinafter referred to as an input image) containing a pattern of many objects and characters such as everyday scenery seen by humans. ), There is a matched filtering method. FIG. 2 is a schematic configuration diagram showing a configuration of an optical system of a conventional matched filtering method. In the matched filtering method, an input image is displayed on the image display device 14, a Fourier transform image of the input image is formed on the back focal plane of the Fourier transform lens 15,
The transmitted light is incident on the matched filter 25 of the target pattern arranged at the back focal position and the transmitted light is transformed into the Fourier transform lens 1.
When the target pattern is present in the input image by further Fourier transform by 8, the correlation spot showing the high correlation appears on the screen 19 on the back focal plane of the Fourier transform lens 18, and the position thereof causes the correlation spot in the input image. 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 interference fringes with the reference light is generally used for 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 desired pattern to be searched, and the tolerance of filter alignment is extremely small, resulting in a positional deviation of several μm. There is a problem that performance may be significantly reduced. In addition, since the output image in this method is only a point of bright light that is a correlation spot, when performing another process such as pattern recognition after extracting the target object, the output image is directly input to another process. I could not use it. There is also a method of using a spatial light modulator that can change the desired pattern to be searched in real time without using a hologram for the filter, but in the current spatial light modulator, interference fringes with a fine pitch equivalent to that of a hologram are generated. There is a problem in that the ability to write is inferior and the performance of the optical extraction device is considerably deteriorated.

Another method for extracting a target pattern from an input image is a template matching method used in computer image processing software.
This template matching method is a method of moving a target pattern in an input image and searching for a best matching place. As this method, there are a method of sequentially testing residuals, a method using a cross-correlation coefficient and the like. However, in any of the methods, basically, the target pattern has to be scanned in the input image, which takes time. This is a problem that becomes more prominent as the number of pixels increases.

In order to solve the above problems, 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. 162622/1994).
However, in the proposed method, the output image of the device is input to the device as an input image again to form a feedback loop, 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 Therefore, the present invention has been made to solve the above problems, and a matched filter in which interference fringes of holograms or the like that must be produced for each target pattern to be extracted is drawn. Without using, and because of that, 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 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 extraction device that can perform extraction in a short period of time.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned technical problems, and includes a) a light source which emits a coherent light beam, and b) an intensity transmittance or reflection of an input image. A first image display means for displaying the distribution of the ratio to give an intensity distribution to the light beam; and c) optically Fourier transforming the intensity distribution of the light beam 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 arranged on the Fourier transform surface of the first Fourier transform lens and obtained by the Fourier transform image creating means is displayed as intensity transmittance or reflectance distribution, A spatial light modulator for further providing an intensity distribution; f) a second Fourier transform lens for optically further Fourier transforming the intensity distribution of the light flux transmitted or reflected by the spatial light modulator; and g) the second Image pickup means for picking up an output image obtained by Fourier transforming by a Fourier transform lens, whereby the picked-up output image is displayed again as an input image of the first image display means, In the optical object extracting device that forms a feedback loop that repeats the series of processing steps, a) the output image picked up by the image pickup means is again set to the first During the display as the 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. The density change measuring means for measuring the amount of change in the contrast of the portion, and (b) the contrast of each part of the input image to be displayed again on the first image display means, the output from the density change measuring means a) in advance. A portion having a predetermined value or more set is suppressed, and an output from the concentration change measuring means is provided, and a portion having a predetermined value or less, a concentration operating means for performing an emphasizing operation is provided. The above-mentioned optical object extracting device is provided.

The Fourier transform image forming means includes a light source for emitting a coherent light beam, and a second image display means for displaying the target pattern as an intensity transmittance or reflectance distribution to give an intensity distribution to the light beam. , A third Fourier transform lens for optically Fourier transforming the intensity means 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. It is preferable that it is composed of an image pickup means for picking up an image.

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 an intensity distribution or a reflectance distribution of a target pattern and gives an intensity distribution to the light beam, and a light beam that is transmitted or reflected by the second image display unit. And a third Fourier transform lens that optically Fourier transforms the intensity distribution of the generated light flux, and the writing surface of the 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 spatial light modulator displays the Fourier transform image of the target pattern 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 the writing surface by a threshold value and displaying the image.

[0010]

In the configuration of the optical object extracting device of the present invention as described above, the input image displayed on the first image display means of the optical object extracting device and the output image taken by the image taking means are provided. 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 difference calculation or the like to obtain an image of the difference between the two images. The 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 the pattern having a small similarity has a large change. The result of the concentration change measuring means is
It is output to the concentration operating means.

In the density operation means, the contrast of each part constituting the input image displayed again on the first image display means is changed from the output image picked up by the image pickup 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 emphasized for the portion where the value smaller than the preset value is measured. Therefore, a pattern having a large decrease in contrast has a small similarity to the target pattern, and a pattern having a small decrease in 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 degree of similarity is displayed with a low contrast ratio. That is, since the change of the captured output image from the input image is emphasized by the density change measuring means and the density operating means and displayed again on the first image display means, less feedback is provided as compared with the conventional device. 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, and the incident coherent light beam is the object. The coherent light flux that has been modulated into the intensity distribution of the pattern and is emitted as transmitted light or reflected light passes through the third Fourier transform lens, creates a Fourier transform image of the target pattern on the focal plane, and By using the method of imaging,
By simply displaying the target pattern, it is possible to create a Fourier transform image of the target pattern optically at high speed and easily.
The target pattern can be changed only by changing the image displayed on the second image processing means.

Further, an optical writing type spatial light modulator is used, and the Fourier transform image creating means writes the Fourier transform image of the target pattern directly into this spatial light modulator. Just by displaying
A Fourier transform image of a target pattern can be created optically at higher speed and easily.

Further, the Fourier transform image of the target pattern is displayed on the spatial light modulator in substantially real time as an image binarized by an appropriate threshold value, so that the target pattern remaining in the output image is obtained. It is possible to improve the decrease in the contrast ratio of the. Further, by reducing the contrast ratio of the target pattern by making the optical writing type spatial light modulator perform a display operation by binarizing the image written from the writing surface with a threshold value. Can be done.

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

[0016]

[Embodiment 1] FIG. 1 is a schematic diagram showing the construction of an embodiment of an optical object extracting apparatus of the present invention. The coherent light beam 12 emitted from the laser 11 is expanded by a beam expander 13 to an appropriate light beam diameter and collimated,
It is incident on the image display device 14. The image display device 14 includes
The input image that is the target of object extraction is drawn with the transmittance distribution of the intensity pattern, the light flux 12 is transmitted, and the input image is read. The light flux 12 passes through the Fourier transform lens 15, and forms a Fourier transform image of the input image on the spatial light modulator 16 arranged on the focal plane of the Fourier transform lens 15.

On the other hand, the Fourier transform image of the target pattern to be extracted is stored in advance in the computer 17, and the intensity pattern of the Fourier transform image of the target pattern is displayed as a transmittance distribution on the spatial light modulator 16 from the memory. . Therefore, the Fourier transform image of the input image is modulated by the intensity pattern of the Fourier transform image of the target pattern when passing through the spatial light modulator 16, and the product of the corresponding spatial frequency components of the input image and the target pattern is obtained. Is calculated. After this, the light flux 12 is converted into the Fourier transform lens 18
And is subjected to inverse Fourier transform, and the result of the cross-correlation calculation 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, the output image formed on the screen 19 is captured, and it is sent to the computer 17.

Specifically, the output image is an image in which the input image having a small correlation with the target pattern is deleted.
The part of the input image that has a high degree of correlation with the target pattern is
The contrast ratio does not drop and is output, and conversely, the portion having almost no correlation with the target pattern is 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.

Here, 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. 4 is displayed on the spatial light modulator 16, the image pickup device 20 displays
An output image as shown in FIG. 5 is captured. In the output image shown in FIG. 5, the circular pattern 50 having a high degree of correlation with the target pattern shown in FIG. 4 is output in a state in which the change in the contrast ratio from the input image is small, and the circular pattern having a low degree of correlation with the target pattern shown in FIG. The patterns other than the pattern 50 are output in a state where the change in the contrast ratio from the input image is large. The extraction result of the target object is output to a CRT or the like in the computer.

The concentration change measuring device 21 used here includes
The output image captured by the imaging device 20 and the image display device 14
The input image displayed at is input and the difference between the two input images is calculated. Here, FIG. 6 is an explanatory diagram showing an example of an image output from 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 concentration change measuring device 21. The result of the difference calculation as shown in FIG. 6 reflects the degree of change in contrast of the output image from the input image. Information on the difference calculation result is output to the concentration operation device 22.

The density operation device 22 is inputted with information on the difference calculation result between the output image picked up by the image pickup device 20 and the image from the density change measuring device 21, and based on the information on the difference calculation result of the image. The contrast of the output image is being manipulated. At this time, the contrast of the portion where the output of the density change measuring device 21 is larger than a preset value, that is, the portion where the change of the output image from the input image is large is suppressed, and the output of the density change measuring device 21 is preset. Contrast enhancement is performed on a portion smaller than the above value, that is, a portion in which the change in the output image from the input image is small, and thereafter, the image is displayed again on the image display device 14 for feedback processing.

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

A circle pattern 30 is extracted from the input image shown in FIG. At this time, the concentration change measuring device 21
And the density operating device 22 emphasize the change in the contrast of the output image captured by the image capturing device 20 from the input image and display it on the image display device 14. Therefore, the density change measuring device 21 and the density operating device 22 The object can be extracted with a smaller number of repetitions as compared with the case where contrast is not emphasized by using. The number of repetitions is controlled by the program of the computer 17 to an appropriate number. Further, the result of extracting the target object is output to a CRT or the like in the computer.

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. The spatial light modulator 16 may be a liquid crystal panel, which is a general electric address type spatial light modulator. Further, here, as the image pickup tube 20, a CCD camera, an image pickup tube, or the like can be used.

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 both images near the optical axis may be performed. As a result, low spatial frequency components that are common to all patterns are cut, and the target pattern can be extracted more efficiently. Other than using a mask, there is also a method of not displaying the image near the optical axis when the Fourier transform image of the target pattern is displayed on the computer 17.

Furthermore, when 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 part of the Fourier transform of the input image that matches the Fourier transform image of the target pattern is spatially divided. Since the light is transmitted almost without being affected by the light modulator, it is possible to prevent the contrast of the target pattern remaining in the output image from being lowered. As such a spatial light modulator, an electrically addressed type using a ferroelectric liquid crystal can be used. In particular, a spatial light modulator using a ferroelectric liquid crystal is suitable not only for binarizing an image, but also because it has a high resolution in principle and is easy to obtain high contrast. Also, if the binarization process is performed using an image processing device or the like, the same can be done using a general electric address type spatial light modulator.

Further, to the density change measuring device 21 and the density operating device 22, a method of adding an image processing device to a digital computer and performing the above processing by software, or a similar function using an electronic circuit, It is possible by a method of making it hardware.

[0028]

[Embodiment 2] FIG. 8 is a schematic diagram showing the construction of another embodiment of the optical object extracting apparatus of the present invention. This embodiment is characterized in that the Fourier transform image of the target pattern displayed on the spatial light modulator 16 is optically obtained and the output image is subjected to the grayscale conversion by the image processing device.

That is, the coherent light beam 12 emitted from the laser 11 is expanded by the beam expander 13 to an appropriate light beam diameter, collimated, and incident on the half mirror 81, where it is divided into two light beams 12a and 12b. To 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, which is stored in the computer 17, is drawn as a transmittance distribution, and the light beam 12a is transmitted to read the target pattern. After that, the light flux 12a passes through the Fourier transform lens 33, and forms a Fourier transform image of the target pattern on the screen 84 arranged on the focal plane thereof. This image is captured by the image capturing device 85. Here, as the target pattern displayed on the image display device 82, the target pattern may be directly imaged by the imaging device and the image thereof may be displayed.

On the other hand, the light beam 12b enters the image display device 14 after being deflected by the mirror 86. On the image display device 14, the input image to be the target of object extraction 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 the spatial light modulator 16 arranged on the focal plane of the Fourier transform lens 15. Since the Fourier transform image of the target pattern imaged by the imaging device 85 is displayed on the spatial light modulator 16 as the transmittance distribution of the intensity pattern, the Fourier transform of the target pattern is performed when the light beam 12b is transmitted. Modulated by the intensity pattern of the image, the product of the corresponding spatial frequency components of the input image and the target pattern is calculated. Thereafter, the light flux 12b is transmitted through the Fourier transform lens 18 and is again Fourier transformed, and the screen 1
The result of the cross-correlation calculation of the input image and the target pattern is output on the screen 9. Specifically, the output image is an image in which the input pattern having a small correlation with the target pattern is deleted, and the contrast ratio of the portion of the input image having little correlation with the target pattern is lowered. However, on the contrary, the portion having almost no correlation with the target pattern is output with almost no contrast ratio.

After that, the output image is the density change detection device 2
1 and the density converter 22 to improve the contrast. This processing is the same as that described in the first embodiment, and will be omitted. In this embodiment as well, the density change measuring device 21 and the density operating device 22 are used to emphasize the change in the contrast of the output image captured by the image capturing device 20 from the input image and display it on the image display device 14. ,
By using the density change measuring device 21 and the density operating device 22, the object can be extracted with a smaller number of repetitions as compared with the case where the contrast is not emphasized. For example, the part with low contrast is smaller,
The part with high contrast is processed to be larger. In addition, if a process that increases the contrast as a whole is performed, the target pattern can be more reliably extracted in the final output, or a pattern similar to the target pattern can be extracted. be able to. In addition to this, it can be used for the purpose of correcting the deterioration of the image due to the input image passing through the optical system.

The number of times of repetition is determined by the computer 17
The program is controlled to an appropriate number of times. The extraction result of the target object 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. A CCD camera, an image pickup tube, or the like can be used as the image pickup 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 produced. There is no problem with the device.
Further, the concentration change measuring device 21 and the concentration operating device 22 are
An image processing apparatus may be added to a digital computer and the above-mentioned processing may be performed by software, or a similar function may be realized by a hardware method using an electronic circuit.

An optical writing type spatial light modulator was used. As such a spatial light modulator, a liquid crystal panel combined with a photoconductor layer is generally used, and a nematic liquid crystal is used. Is practically suitable. The Fourier transform image of the target pattern is written in the optical writing type spatial light modulator in the gray level or in the binarized image, but when writing in the binarized image, the contrast ratio of the target pattern in the output image is changed. The effect is that the decrease is suppressed. In such a spatial light modulator, not only binarization of an image but also
In principle, the resolution is high and the contrast ratio is high, which is preferable.

Further, as an optical address type spatial light modulator, BSO (bismuth silicon oxide; Ba ₁₂
It is also possible to use a medium having a light-induced refractive index change such as SiO ₂₀ ). In particular, in the BSO material, writing and reading are performed simultaneously by using visible light having a high sensitivity and a short wavelength as the writing light and using light having a wavelength range from red to infrared with a low writing sensitivity as the reading light. be able to. However,
The BSO material can be used as a reflection type by using a reflection plate, but usually, it is often used as a transmission type. 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, the following remarkable technical effects are obtained. That is, first, the change in the captured output image from the input image is changed by the density change measuring means and the density operating means.
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 times of feedback as compared with the conventional optical target extracting apparatus. Secondly, there is no need to use a matched filter that draws interference fringes such as holograms that must be manufactured for each target pattern to be extracted, and because of that, alignment of the optical system is relatively easy. Could be provided. Thirdly, there is provided an optical object extracting apparatus capable of extracting the target pattern from the input image in the form as it exists in the input image instead of the correlation spot. Fourthly, an optical object extracting apparatus that can process in a short time is provided because it is not necessary to scan the object pattern.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing the configuration of an embodiment of an optical object extracting device of 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 showing 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 the output of the concentration operating 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]

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 Device 25 Matched filter 30, 50, 60, 70 Circular pattern 81 Half mirror 86 Mirror

Claims (1)

[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; ) A first Fourier transform lens for optically Fourier transforming the intensity distribution of the light flux transmitted or reflected by the first image display means, and d) a pattern to be extracted (hereinafter referred to as a target pattern).
Fourier transform image creating means for creating a Fourier transform image of, and e) 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, A spatial light modulator for displaying the intensity distribution or reflectance distribution to give further intensity distribution to the light flux; and f) optically further Fourier transforming the intensity distribution of the light flux transmitted or reflected by the spatial light modulator. A second Fourier transform lens for transforming; and g) image pickup means for picking up an output image obtained by Fourier transforming by the second Fourier transform lens, whereby the picked up output image is re-shot. An optical object extracting apparatus that forms a feedback loop that displays the input image of the first image display means and repeats the series of processing steps a plurality of times. 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 the input image displayed on the first image display means with the output image obtained by inputting to the optical object extracting device to measure the amount of change in contrast of each part of the image. B) The contrast of each part of the input image to be displayed again on the first image display means is such that the output from the density change measuring means a) is a predetermined value or more,
The optical object extracting device according to claim 1, further comprising: a concentration operating unit that performs an operation of emphasizing in a portion where the output from the concentration change measuring unit is suppressed and is equal to or less than a preset predetermined value.