JP2721510B2 - Identification method and apparatus using matched filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to the shape of an object, characters written on the surface of the object,
The present invention relates to an identification method and apparatus using a matched filter for optically detecting the presence or absence of a figure or a flaw and the position of the figure.

[Conventional technology]

For inspection of electronic circuit boards, character recognition, identification of general object shapes, and the like, it is desired to develop a technology for identifying a plurality of object shapes and positions and the number thereof in real time at a production site. .

The present inventor and applicant have already filed an application for an optical matched filter method capable of simultaneously measuring the shape, number, and position of a multi-shaped object as Japanese Patent Application No. 62-204579.

The matched filter producing optical system and the shape discriminating optical system will be schematically described with reference to FIG.

FIG. 5 is an explanatory view schematically showing an optical system for implementing the optical matched filter method, wherein 1 is a light source, 2 is a beam splitter, 3 and 4 are mirrors, 5 is a beam expander,
6 is a reference light, 7 is an object illumination light, 8 is an object surface, 9 is a beam combiner, 10 is a matched filter, 11 is an output surface, and 12 is a CCD.
Camera, 13 frame memory, 14 is a microcomputer, L ₁ is a Fourier transform lens, L ₂ is the inverse Fourier transform lens, the front focal plane of the P ₁ is the lens L _1, P ₂ is the focal plane of the lens L _1, P ₃ is a focal plane of the lens L _2.

First, in order to produce a matched filter, in a wide parallel beam 7 far away from each other to be measured shaped object located on the object plane 8 is placed on the front focal plane P ₁ of the Fourier transform lens L _1. Diffracted light generated from each shape object forms a respective diffraction pattern around the optical axis on the focal plane P ₂ of the lens L _1. These diffraction patterns including the phase shift information and the shape according to the position of the object are simultaneously converted into one reference light 6.
In this case, information on the shape and position of each object is frozen simultaneously into one hologram by one exposure. The hologram is produced on the focal plane P ₂ of the Fourier transform lens L _1.

To identify this way the object shape using a matched filter 10 that are created and their position is established a matched filter 10 to the focal plane P ₂ of the lens L _1. And the reference beam 6 is shielded and the other, give part of the narrow parallel beam of the object beam 7 on the front focal plane P ₁ of the lens L _1, to form a measurement field of view. Taking a measurement object group in the measurement field of view is identified on the focal plane P ₃ after the shape and the position of each object is the inverse Fourier transform lens L ₂ by the matched filter 10. With respect to these measured objects, the current position of the measured object around the position where the object of each shape was set when the filter was manufactured appears as a light spot of the reference light at a corresponding position. The above is expressed numerically as follows using FIG. 6 for explaining the relationship between the positions and coordinates of the planes P ₁ , P ₂ and P ₃ . X of the front focal plane P ₁ of the Fourier transform lens L ₁
In the y coordinate system, the image function at the reference position is g _i (x,
y), the n different objects shapes are i = 1 to n, arranged from the reference position x, respectively optionally in the y-direction x _ai, apart only y _ai. Image U ₀ by all objects, since the sum of each object image, is expressed as follows.

The back focal plane P ₂ of the lens L _{1 having} the focal length f ₁ from this object image
At (x _i -y _i coordinate), a Fourier transform image U _0f shown below is created.

Here, λ is the wavelength of the incident light, and g _i (x, y)
Is defined as G _i (x _i / λf ₁ , y _i / λf ₁ ).

U _0f is an object light, and a plane wave R traveling with the object light inclined by θ _x and θ _{y in the} (x _i , y _i ) direction from the optical axis, respectively.
(X _i , y _i ), that is, _{Is used} as a reference beam to interfere with U _0f to obtain a hologram having the following transmittance distribution. However, the average light intensity of the object light and the reference light has been removed.

Place the hologram with a carrier frequency containing information shape and position of the object as shown in equation (4) to the focal plane P ₂ of the lens L _1, a matched filter.

Next, put away the lens L ₁ of the front focal plane narrow measurement image during visual function on the Σg (x, y) a group of objects represented by x, x respectively from the reference point in the y-axis direction _bl, only y _bl If a new object to be measured is Fourier transformed by the lens L _1, given as an object light image function as follows.

This light U _0b is diffracted by a filter having a transmittance distribution represented by Expression (4). + 1st order diffracted light U
_d1 is expressed as follows from equations (4) and (5).

Further, the image lens the light focal length is f ₂
It is expressed on the back focal plane P ₃ (x ₀ -y ₀ coordinate) of L ₂ as follows.

This light intensity distribution is further expressed in the form of a correlation function as follows.

Equation (8) is a correlation function between g _i (x, y) and g _l (x, y).
If the functions match, ie g _l (x, y) is g
When it is equal to _i (x, y), the value of the expression (8) takes the maximum value. Therefore, the maximum value in the image is x ₀ is the next position of the i = l = k in equation (8) (x _0k, y _0k) Take.

Further, the value of the correlation function of the equation (8) taken by the image where i ≠ l is smaller than that in the case of i = 1. Therefore, the shape and the position of an object having a certain shape are measured as the light spot of the object identification signal at the position indicated by the relationship of the equation (9) with the position of the object having the same shape recorded in the filter.

To more clearly understand the output position of the object to be measured, obtaining the recognition signal point coordinates of the identified object on the coordinate axes relative to the position of the filter produced object on P ₃ sides.

Filter manufactured object g _i (x, y), for example, _{□: i = 1, g 1} (x,
y), ○: i = 2 , g 2 (x, y), △: i = 3, g 3 (x, y) and to the respective object in the input P ₁ side _{g 1 (xx a1, yy a1} ) , g ₂ (xx _a2 , y
-y _a2 ), g ₃ (xx _a3 , yy _a3 ) to create a filter. Then, the object to be identified g, l = 1, 2, 3 is input to the input surface, respectively.
Position g ₁ of _{P 1 (xx b1, yy b1} ), g 2 (xx b2, yy b2), g 3 (xx b3, y
-y _b3 ). Since be performed at the focal plane P ₃ of the lens L ₂ output observations 1-order diffracted light, the optical axis of the first order diffracted light in the _{(-f 2 sinθ x, -f 2} sinθ y), g i And g _l
The output from the correlation of Observed around.

Then, the output fields of □, ○, and △ are as shown in FIG.

Furthermore, the correlation signal by the identified object g is presented in the next coordinate point on P ₃ sides.

□: ( ₁ + _xb1 , ₁ + _yb1 ) ○: ( ₂ + _xb2 , ₂ + _yb2 ) Δ: ( ₃ + _xb3 , ₃ + _yb3 ) That is, each identification signal light point is a point. Around At the position (x _bl , y _bl ) of g _l (x, y), and the output is reversed (point-symmetrical position). Therefore, if the same thing is more present in the same object plane P ₁ as the object to be measured, the output field on P ₃ surfaces the object corresponds, the number of light spots corresponding to the number of objects to be measured It will appear in correspondence with the position in the P ₁ side of the face.

[Problems to be solved by the invention]

However, in the matched filter method, the relative position between the input image and the entire optical system of the matched filter is defined, and as the input image, a dry plate that displays a grayscale image with different transparency on a transparent film is usually used. ,
Therefore, since it is necessary to install all optical systems in a dark room, it has been difficult to introduce the optical system into a factory production site and use it in a product production process.

The present invention has been made to solve the above problems, and only a photographing camera and an illumination light source are arranged at a site where an identification target exists, and a photographed image is transmitted to an appropriate position by a cable or the like and displayed on a display device. By providing a display image as an input image of a matched filter, an identification method and apparatus using a matched filter capable of simultaneously measuring the shape, number and position of an object at a production site of a factory are provided. The purpose is to:

[Means for solving the problem]

The present invention arranges a plurality of discrimination targets at positions separated from each other in one light flux, and generates a Fourier transform image of each discrimination target while generating a phase difference between the Fourier transform images of each discrimination target. An identification method in which a hologram created simultaneously with one reference beam and used as a matched filter is used as a matched filter. A captured image of an identification target is displayed on a display screen as a difference in transparency, and the display image is displayed. An identification method using a matched filter for identifying an identification target as a matched filter input image, and a method in which a plurality of identification targets are arranged at positions separated from each other in one light beam, and between the Fourier transform images of the respective identification targets. A hologram created by simultaneously forming a Fourier transform image of each identification object while generating a phase difference depending on the position, and causing this to interfere with one reference beam. A discrimination apparatus for use as a matched filter, image capturing apparatus for capturing the identification target,
A display device for displaying a captured image, a conversion unit for converting an inverse Fourier transform image of an output optical image when a display image displayed on the display device is used as an input image of a matched filter into an electric signal, and an image signal from the conversion unit Is characterized by an identification device using a matched filter provided with a signal processing device for processing.

[Action]

The present invention arranges a plurality of discrimination targets at positions separated from each other in one light flux, and generates a Fourier transform image of each discrimination target while generating a phase difference between the Fourier transform images of each discrimination target. A hologram created at the same time and made to interfere with one reference beam is used as a matched filter, and the captured image to be identified is displayed on the display screen as a difference in transparency, and the displayed image is input to the matched filter. By using an image, even an identification target at a place such as a production site can be photographed with a TV camera or the like and transmitted as an image signal, and the display image can be used as an input image of the matched filter method. Rapid identification processing can be performed in real time.

〔Example〕

FIG. 1 is a view showing one embodiment of the present invention, in which 21 is an object to be identified, 22 is a filter, 23 is an image enlargement / reduction optical system,
24 is an autofocus optical system, 25 is an image rotation mechanism, 26 is a TV camera,
27 is a liquid crystal drive control device, 28 is a liquid crystal display device, 29 is a laser light source, 30 is a collimator optical system, 31 is an enlargement / reduction optical system, 32 is an image input surface, 33 is a Fourier transform lens, 34 is a multi-matched filter , 35 is an inverse Fourier transform lens, 36
Is the output surface, 37 is the CCD camera, 38 is the frame memory, 39 is C
PU, 40 is an interface (IF), 41 and 42 are optical system controllers, 43 is a control device, and 44 is an image processing device.

In the figure, an image of an object to be identified 21 illuminated by a reflection type or transmission type illumination device is subjected to object shape by a filter 22 constituting an object shape feature extraction optical system such as a document filter, a polarizing filter, a color filter or a spatial filter. Are extracted. These images are adjusted to a size suitable for discriminating the images by the image enlargement / reduction optical system 23, and further, are rotated by a predetermined angle by the image rotation mechanism, if necessary, through the automatic focusing optical system 24. An object image is captured by the TV camera 26. When only the shape is identified irrespective of the object size and inclination, the size and inclination of the image are instantaneously changed in an analog manner by the object image enlargement / reduction optical system 23 and the image rotation mechanism 25, and the matched filter 24 is used. An object image that matches the original image of is searched for. Thus TV camera 26
The image captured by the camera is stored in an image processing device 44 having a frame memory as needed, and subjected to image processing to extract features of the image. When the image processing is not necessary, the analog signal is directly displayed on the liquid crystal display device 28 by the liquid crystal drive control device 27. Thus, a light transmittance distribution corresponding to the image is formed.

The light transmittance distribution on the liquid crystal display device 28 is incoherent / coherent light-converted by the coherent light collimated by the collimator optical system 30 and emitted from a laser light source 29 such as He-Ne, and image feature extraction is performed again. The size of the matched filter 34 is adjusted by the enlargement / reduction optical system 31 including the use optical system. The image on the liquid crystal display device 28 forms a coherent light image on the focal position BB plane 32 of the lens of the optical system 31. The diffraction pattern from the 32 coherent light images on the focal plane of lens 33
Multiple matched filters on the back focal plane of 33
The shape is determined by 34, and when there is an object image to be identified that matches the original image on the filter 34, on the identification signal light output surface 36 on the back focal plane of the inverse Fourier transform lens 35, on the set coordinates of each original image The identification signal light appears as a correlation light spot at the object position.

The intensity of the light spot on the identification signal light output surface 36 and its position are CC
The image signal taken by the D camera 37 is stored in a frame memory controlled by the CPU 39 and analyzed, and a check is performed for each product. In this case, the CCD
Other detecting means such as a line sensor may be used instead of the camera.

It should be noted that the optical system 31 such as enlargement / reduction, the optical system 22
26, the object to be identified 21 is an optical system controller 41, 4 connected to the CPU 39 via the interface 40, respectively.
2, controlled by the controller 43.

In this way, the TV camera 26 is arranged at the production site to photograph an object to be identified, this image signal is transmitted by a cable or the like and displayed on a display device, and the display image displayed on the display device is input to the matched filter by an input image. By doing so, it is possible to perform an inspection of the identification target or the like in taal time. The display device is not limited to a liquid crystal display device, and may be any display device as long as it can display images as transmittance or reflectance distribution.

FIG. 2 is a view showing another embodiment of the present invention.
In this case, a reflection type filter is used.

First, a matched filter is created by irradiating reference light from the object light and the reflection side to form a volume hologram. Then, a Fourier transform image of the object image is formed on the matched filter 34, the reflected light is incident on the lens 33, and the inverse Fourier transform image is photographed by the camera 37 via the half mirror 51. In this embodiment, the volume hologram is used as a matched filter also in the depth direction of the photosensitive material, so that the sensitivity as a filter can be improved, and the Fourier transform lens and the inverse Fourier transform lens can be used in one. Since a single lens can be used, the apparatus can be made compact and the problem of alignment between the Fourier transform lens and the inverse Fourier transform lens can be solved.

FIG. 3 shows a case where an object image is reduced using a reduction optical system.
FIG. 4 is a diagram showing a case where an object image is enlarged using an enlargement optical system.

In general, the diffraction efficiency changes depending on the size of the object. If the size is too large, the diffraction efficiency is deteriorated. If the size is too small, such as lymphocytes in blood, light spreads too much and the diffraction efficiency is similarly reduced. Therefore, the diffraction efficiency can be improved by reducing the size of the image if the object is too large, and increasing the size of the image if the object is too small.

Therefore, in FIG. 3, the image of the object plane 28 is reduced to the plane 32 by the lenses 53 and 54, and in FIG.
6 and 57 enlarge the image of the object plane 28 to the plane 32.

〔The invention's effect〕

As described above, according to the present invention, an object is photographed using a TV camera, the image signal is transmitted to an arbitrary position by a cable, and an image is displayed on a liquid crystal display device or the like. The object to be identified can be identified by the optical matched filter method using it. Therefore, it is sufficient to install only the photographing part at the site and the main part of the identification device at an appropriate place, and to identify the object at the production site etc. Etc. can be performed in a central control room or the like. In addition, the configuration of the apparatus is made compact by using a reflective filter as a matched filter, and the matched filter method is applied after converting a three-dimensional object into a two-dimensional display image. Can be performed freely, the diffraction efficiency can be improved, and the identification accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing the configuration of an image recognition apparatus using a matched filter of the present invention, FIG. 2 is a diagram showing another embodiment of the present invention using a reflective matched filter, and FIG. FIG. 4 shows another embodiment of the present invention using an optical system, FIG. 4 shows another embodiment of the present invention using an enlarged optical system, and FIG. 5 implements an optical matched filter method. explanatory view showing an outline of an optical system for, FIG. 6 is an explanatory diagram, FIG. 7 is the shape object P ₃ faces showing the relationship between the position and the coordinates of P _1, P _2, P ₃ side of FIG. 5 FIG. 4 is an explanatory diagram for describing identification coordinates of FIG. 21 ... Identified object, 22 ... Filter, 23 ... Image enlargement / reduction optical system, 24 ... Autofocus optical system, 25 ... Image rotation mechanism,
26 …… TV camera, 27 …… Liquid crystal drive control device, 28 …… Liquid crystal display device, 29 …… Laser light source, 30 …… Collimator optical system, 31 …… Enlargement / reduction optical system, 32 …… Image input surface, 33 ……
Fourier transform lens, 34… Multiple matched filter, 35… Inverse Fourier transform lens, 36 …… Output surface, 37…
… CCD camera, 38 …… Frame memory, 39 …… CPU, 40…
... Interfaces (IF), 41, 42 ... Optical system controller, 43 ... Control device, 44 ... Image processing device.

Claims (11)

(57) [Claims] 1. A Fourier transform image of each discrimination object while arranging a plurality of discrimination objects at positions separated from each other in one light beam and generating a phase difference between the Fourier transform images of each discrimination object depending on the position. And a hologram created by interfering this with one reference beam as a matched filter, wherein a captured image of the identification target is displayed on a display screen as a difference in transparency, and the display image is displayed. Using the matched filter as an input image of the matched filter. 2. A Fourier transform image of each discrimination object while arranging a plurality of discrimination objects at positions separated from each other in one light beam and generating a phase difference between the Fourier transform images of each discrimination object depending on the position. And a hologram created by causing this and one reference beam to interfere with each other as a matched filter, comprising: a photographing device for photographing a discrimination target, a display device for displaying a photographed image, and a display device. A conversion unit that converts an inverse Fourier transform image of the output optical image into an electric signal when the displayed display image is used as an input image of the matched filter; and a signal processing device that processes an image signal from the conversion unit. Matched features
Identification device using a filter. 3. An identification device using a matched filter according to claim 2, wherein a feature extraction optical system is provided between the identification target and the photographing device. 4. The identification device using a matched filter according to claim 3, wherein the feature extraction optical system includes a filter, an enlargement / reduction optical system, and an image rotation mechanism. 5. An identification device using a matched filter according to claim 3, wherein the feature extraction optical system is driven and controlled by a signal processing device. 6. A matched image processing apparatus according to claim 2, wherein an image photographed by the image processing apparatus is processed to perform feature extraction.
Identification device using a filter. 7. The identification device using a matched filter according to claim 2, wherein the display device is a liquid crystal display device. 8. An identification device using a matched filter according to claim 2, further comprising an enlargement / reduction optical system between the display device and the matched filter. 9. An identification apparatus using a matched filter according to claim 8, wherein the enlargement / reduction optical system is driven and controlled by a control computer. 10. The matched filter is of a reflection type,
3. An identification apparatus using a matched filter according to claim 2, wherein the Fourier transform lens has a function of an inverse Fourier transform lens. 11. An identification device using a matched filter according to claim 2, wherein the identification target is driven and controlled by a signal processing device.