JPS60152907A - Misalignment detector of shape or alingment of body - Google Patents

Abstract

PURPOSE:To make it possible to perform detection by a simple system constitution, by judging the change in central position of the width of a body, based on the change in interval from the position of the synchronization signal of the specified first and second image signals to the maximum position. CONSTITUTION:Scanning is performed by TV cameras 6a and 6b, which are arranged along the axis of a pipe 1, like scanning lines 3a and 3b approximately vertically with the axis of the pipe 1. Thus image signals 4a and 4b are obtained and inputted to a real-time electrooptical correlator 101 having two ultrasonic wave and light modulators (not shown) and a Fourier transformation optical system (not shown). A mutual correlation signal C(tau) of the signals 4a and 4b is detected by a peack detecting circuit 103. A deviation (e) from the center between horizontal synchronizing signals at the peak position is detected as the bending of the pipe 1.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a device that can detect irregularities in the shape, arrangement, etc. of objects by examining or comparing and contrasting correlation signals obtained from two video signals.

(Prior art) The task of determining whether a moving object, such as an object in the process of being produced during an assembly line process, maintains the shape specified in the standard has traditionally relied on the judgment of two people. Ta. Many efforts have been made to save labor and automate this type of work.

Some are in practical use, but there are slight differences in shape,
For example, it can be said that a practical device that can detect on-line the bending of the axis of a tubular object, the misalignment of the axis of a rod-shaped object, etc. has not yet been realized. This lump detection device used in the production process has three requirements: (1) simple system configuration, (2) high-speed operation, and (3) low cost. Moreover, since the basic technology of this type of detection device is pattern recognition and single image processing, using digital image processing, which is currently extremely advanced in technology, it is possible to detect the shape, arrangement, or irregularity of the object itself. Although it seems that it is not impossible to judge and detect the problem, there are many problems in realizing a device that is simple, inexpensive, and can maintain high speed that can be adapted to online processing (Summary of the Invention) The first object of the present invention is to realize a device that detects irregularities in the shape or arrangement of objects with a simple system configuration.

For this purpose, the present invention uses one or two television cameras to obtain two video signals t1'' for mutual comparison, creates a correlation signal between the two video signals, and calculates the form or structure of the correlation signal. Based on this, irregularities in the shape or arrangement of objects are detected.

Although it is possible to use digital signal processing as a correlation device to obtain a correlation signal between two video signals, in particular, when using an acousto-optic image correlation device, it is difficult to operate the detection device reliably online. can. The second objective of the present invention is to realize a method suitable for high-speed operation.

Furthermore, since the present invention employs a configuration using a television camera and a correlator, the system configuration is simple and a low-cost device can be realized.

That is the third purpose.

(Principle of operation) This invention can be realized in several embodiments as described later, but first, in order to understand the invention, we will use two television cameras to obtain two video signals from the roof crease. , the operating principle will be explained for the case where a correlation signal of those video signals is obtained. Referring to Figure 1, it is assumed that the object to be tested for irregularities in shape is, for example, a tube 1 whose longitudinal axis is bent. The two television cameras capture the input image 2 at two different points along the tube axis. Each has an angle of view (dotted rectangle) 2a and 2b, and the arrow scans in a direction almost perpendicular to the tube axis! Scan as shown in 3a13b to obtain video signal 4a.
, get persimmons. The video signal includes a horizontal synchronizing signal HORa.

There is HOR,b. Since the outside diameter of the tube is generally uniform,9 the surface image signal 4 is normally as shown in Figure 1.
a, 4b can be obtained. However, due to the presence of the test object,
A case will be described in which a signal appears at a white level with respect to a black level of the background. (It is clear that the opposite case can be considered in the same way.) Next, the principle of correlation calculation using a video signal will be explained with respect to an acousto-optic image correlation device. FIG. 2 shows a schematic diagram of its configuration. This device takes into account that the video output signal of a commonly used television camera has an appropriate repetition period and frequency band as the input signal of an electro-optic correlator, and uses the electro-optic correlator to generate signals for each horizontal scan. A correlation signal of a video signal is obtained and a correlation image is constructed on the screen of a receiver. In the image correlating device in figure wJ2, the input image 2 is sent to a sweep signal generator 5. An image is taken by an imaging device 100 comprising a television camera 6 and a synchronization signal separation circuit 7, and the obtained video signal is input to a correlator 101 to obtain a correlation signal of the video signal for each horizontal scan. This correlation signal is sent to the synchronous signal mixer 8. input to an image receiving device 102 consisting of an image receptor 9;
A correlated image of the input image 2 is displayed on the screen of the input image 2.

Next, the principle of optical correlation calculation using video signals will be briefly explained. The correlator 1 (11 has two ultrasonic light modulators and a Fourier transform optical system ti.In one stock of real-time electro-optic correlator!!+1 Add to the two ultrasonic light modulators If the electrical signals are f, (x), t2(x), the correlation output signal C(t) is given by the following equation.

C(r)=/Fl (x-t) P2 (x+r
)dx・・・・・・・・・(1)d However, F+(X) = (fA))”, F*6C
1= (ft(X))2, but '+ (x), f
UP when both t(x) are binary signals, (x) = f
, ←), F, ←) = f, cutting) holds true. The integral interval [-d, d] in equation (1) is a value determined by the width of the light beam of the Fourier transform optical system. In addition, the integral calculation is performed by the action of the lens in the optical system, and f (
Since the movement (delay) T of x) is automatically hit, (13
It is possible to realize the calculation of expressions. Equation (1) will be explained using an example of autocorrelation calculation. FIG. 3 is a diagram showing how to capture a video signal by the imaging device 100. The sweep signal generator 2 causes the television camera 6 to perform two-way horizontal scanning as shown in the figure to obtain a video signal f(α, i) in which the scanning direction is reversed for each horizontal scan. a is the coordinate in the horizontal scanning direction, and i is the number of times of horizontal scanning. This video signal f(
It is assumed that σ, i) is a black and white binary signal. f(a,i)
is input to the correlator 101, and the correlation calculation performed within the correlator is shown in FIG. Figure 4 (a> (d)
shows a state in which the input video signal f(α, i) propagates in opposite directions at a speed of τ by the ultrasonic optical modulator in the correlator, and correlation calculation is performed in the central portion 2d. . The width 2d is the width of the light beam within the correlator.

This corresponds to the integral interval mentioned above. Further, in the correlator, a cross-correlation between the video signals f(α, i) and f(α, i+1) is performed. Figure (c) shows f(α
.

It shows the cross-correlation output between i) and ((a, i+1).

As is clear from the figure, f(α−)ki((a,i+i)) holds true in the optical correlator, and f(a,i) and f(”
The cross-correlation with f (a, i
) represents the autocorrelation C(T) of

C(y,i)=/'f(αgo, 1)f(α+r,
i) dα...(2) → The important point here is that f(α, i) in the integral interval 2d
In order to perform a correlation calculation between f(α, i+1) and f(α, i+1), there must be at least 1/2 or more of the length of no signal before and after the signals of f(α, i) and f(α, i+1). It would be bad if the part had to exist. That is, as shown in the figure, if the horizontal synchronization time is Th, the length of each horizontal scan of the video signal obtained from the input image is less than Th/2,
Will the remaining portion be designated as a no-signal section?

Alternatively, every other video signal is turned off for each scan,
It is necessary to alternately produce a video signal and a no-signal period with a length of horizontal synchronization time Th.

Now, in the present invention, we use an acousto-optic image correlation device that utilizes correlation calculation between ultrasonic waves and coherent light.
The position where the maximum amplitude value appears when the video signals from the TV camera are cross-correlated.

In other words, the electrical signal detects changes in the elapsed time from the horizontal synchronization signal that corresponds to the time, and determines whether or not the center positions of objects photographed by a television camera match (for example, at the center of the horizontal scan). to determine whether

According to the cross-correlation calculation, 2 should be correlated within the integral interval.
Even if two signals are shifted in the same direction (in the horizontal scanning direction) by the same distance (position or time), there is no change in the position of the maximum output value. That is, this is a property called invariance of the correlation output with respect to translation or erasure of phase information. In the present invention, this characteristic is utilized to extract features from a video signal. By taking advantage of this property.

The cross-correlation output of an object that is located one equal distance apart in the horizontal scanning direction within the fields of view of two television cameras indicates that the object will appear in the center of the television screen, and that the object will not appear in the field of view of the television cameras. No matter where they are located, their relationship remains unchanged. On the other hand, if the large blade object is located at different viewing positions for two television cameras, the position of the correlation output image will shift from the correlation output image position (center position of the screen) for the same position described above. . The magnitude of this shift is proportional to the difference in position of the object to be tested.

For example, when two arbitrary points on a rod-shaped object with a uniform diameter are imaged with a television camera, the video signal is binarized, and a correlation calculation is performed, the output shows the shape of an isosceles triangle. The correlation of equal rectangular waveforms becomes an isosceles triangle. In this case, the peak position of this triangle can be easily and accurately detected with an electrical circuit. Therefore, by comparing the peak positions of the cross-correlation outputs of the video signals obtained from the intersecting points of the test object, it is possible to detect irregularities in the shape or arrangement of the test object, tilt, curve, etc. with a simple system. Possible 0 (Configuration) Next, this invention will be specifically explained with reference to the drawings. Fifth
The figure is a block diagram of an embodiment of the present invention in which bent pipes are detected using two television cameras sa and sb. The symbols in the figure are the same as in FIGS. 1 to 4. The television camera scans parallel to the tube axis in a direction almost perpendicular to it (3a
, 3b) and the video signal 4a.

I got 4b. The cross-correlation signal C(r) of the two distorted video signals output from the correlator 101 is shown as a signal having a peak at a position e apart from the center between the horizontal synchronizing signals. The reason for this is that the Eirin signal 4a is off-center due to the tune JK on the tube axis. By outputting the cross-correlation signal C(τ) by the peak detection circuit 103 in a manner that emphasizes its peak position, deviation of the peak position from the center can be detected as a bend in the tube. In addition.

In this embodiment, even if the diameter of the tube 1 is slightly different (variation in thickness), the peak of the cross-correlation signal can be obtained at the center position of the image (position of the tube axis). , even if such a tube.

It can be seen that this method has the advantage of being able to determine whether the tube axis is straight or not (straight or curved).

In addition, although FIG. 5 illustrates the bending of one tube, the objects located within the angle of view 2a of the first television camera and the angle of view 2b of the second television camera are two different objects. In this case, the change in flesh color in the direction perpendicular to the horizontal scan (longitudinal direction or shaft direction).

In other words, irregularities in the arrangement of the two objects can be detected.

Next, a second embodiment of the present invention will be explained with reference to the block diagram of FIG. The feature of this embodiment is that one television camera 6 obtains two video signals one hour apart. The symbols in the figure are the same as in FIGS. 1 to 5. 6th
In the illustrated embodiment, the second video signal 4a applied to the correlator 101 passes through a delay circuit 104, and a correlation calculation is performed by matching the timing with the second video signal 4b. According to this embodiment, bending of the shaft can be detected when the object to be tested is being transported in the axial direction, and can be applied when there is a change in width in the direction perpendicular to the shaft.

As is clear from the above two embodiments (FIGS. 5 and 6), the following embodiments can be realized according to the present invention.

0) Arithmetic processing that uses convolution and integral calculations instead of cross-correlation calculations.

(b) The central axis is not straight, like a tube or rod.

For example, a device that inspects whether or not the center axis of a toroidal object, such as a donut, is correctly tracing an arc. In this case, it is only necessary to set the position where the arc is to be drawn to be the center of the field of view of the television camera. can. In the future, expensive high-speed digital signal processing technology must be put into practical use, for example, in dedicated LSIs.

(b) Instead of two parallel scans, the set meal is always scanned at the same location, and the difference in scanning time is used to create the same effect as scanning different locations on a moving object. The device configuration is as follows.

(Effects) As described above, the device for detecting irregularities in the shape or arrangement of objects according to the present invention obtains two video signals using a television camera, and then performs a correlation calculation on the two video signals. Since judgments are made by examining the calculation output, the invariance of correlation calculations to translation makes it possible to identify and judge the characteristics of irregularities using a simple system.

In particular, if an acousto-optic image correlation device is used as a device for performing correlation calculations, the correlation calculations can be performed online, so quality judgment of raw materials can be immediately performed in the actual production process. It can be used as a process feedback sensor.

The embodiments can be modified in various ways according to the applied force method, and the present invention has great industrial applicability.

[Brief explanation of the drawing]

FIG. 1 is a drawing for explaining the present invention in detail. FIG. 2 is a block diagram of one embodiment of a correlator which is an essential component of the present invention, FIGS. 3 and 4 are diagrams for explaining the entire operation of the correlator shown in FIG. 2, and FIGS. FIG. 6 is a block diagram of a different embodiment of the present invention. In the figure, 1: Test object, 3: Television camera scanning line, 4
: video signal, 100: imaging device, 101: correlation device,
102: Image receiver, C(r): Correlation signal. Figure 1. 2. Sengiku 3. β

Claims (1)

[Claims] (11) An imaging device that scans an object having a width of a finite length in the scanning direction to obtain a first video signal; an imaging device that scans different objects and generates a second video signal; a correlation device that receives the first and second video signals and obtains a correlation signal of the two signals; four arithmetic signal positions of the correlation signal; and determining means for determining that the center position of the width of the object has changed in the scanning direction due to a change in the interval from The device for detecting irregularities in the shape or arrangement of objects according to claim 1, wherein the imaging device that obtains the video signal and the imaging device that obtains the second video signal are the same imaging device. (3) The apparatus for detecting irregularities in the shape or arrangement of objects according to claim 1 or 2, wherein the apparatus 11 for obtaining the correlation signal is an acoustic optical image correlation apparatus.