JPH0224321B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that can automatically measure the length of a crack that occurs in a test piece.

Generally, when conducting material tests by applying repeated loads to a test piece to generate cracks, knowing the length of the crack and the rate of crack growth is important in understanding the properties of the test piece as a material. That's true.

By the way, as a means of measuring the crack length, the test piece is converted into a video signal using a television camera, the video signal is passed through a film to correct the difference in brightness level depending on the position of the screen, and the video is then passed through the same filter. A conceivable method is to binarize the signal, detect the presence or absence of a black level signal in the horizontal scanning direction from the binarized signal, and count the detected signals in the vertical scanning direction to measure the crack length.

However, such measuring means has the following problems.

In other words, crack length measurement errors occur due to noise components in the binarized image due to dirt and scratches that remain even after the test piece is polished, and furthermore, the difference in brightness level due to the position of the screen cannot be corrected by the filter. Crack length measurement errors occur due to the difficult sound components of the binarized image.

Furthermore, since the crack is thin, it is difficult to detect the crack as a black level of the image, which causes the problem that the crack is measured too short.

The present invention aims to solve these problems all at once, and provides an automatic crack length measuring device that can continuously and automatically measure crack lengths accurately while maintaining high reliability. The purpose is to

Therefore, in order to automatically measure the length of a crack that occurs in a test piece, the automatic crack length measuring device of the present invention
A binarization circuit that binarizes the video signal containing information on the crack, and a window set in the horizontal scanning direction to detect a crack signal from the video signal binarized by the binarization circuit. A crack signal detector detects the presence or absence of a black level signal in the binarized signal for each horizontal scan; If the above-mentioned crack signal is detected for several scanning lines from 1 to 3, the above-mentioned crack signal is detected to be equal to or greater than a pre-given value, the above-mentioned measurement allowable band is extended, and if it is less than the above-mentioned value, the above-mentioned measurement allowable band is contracted to detect the crack. a tracking comparison type crack tip detector that detects the tip and stores the measurement allowable band;
The present invention is characterized in that it is provided with a crack length measuring device that outputs a crack length signal based on the above-mentioned stored value.

Below, an automatic crack length measuring device as an embodiment of the present invention will be explained with reference to the drawings. Fig. 1 is an overall configuration diagram showing its basic structure, Fig. 2 is a schematic diagram showing its test piece, and Fig. 3 a , b and 4 are schematic diagrams for explaining the state of the screen, Figure 5 is a block diagram thereof, Figures 6 to 11 are waveform diagrams of each part, and Figure 12 is a schematic diagram showing the marker. It is a diagram.

As shown in Figures 1 and 2, a television camera 1
(ITV) as the original video signal containing information on the crack 3, the video signal of the test specimen 4 containing the crack 3 extending from the notch 2 formed in advance is input in the range of the screen 5, and the binary value is The signal is supplied to the summing circuit A, and is also supplied to one input terminal of the adder circuit R via the switch S1.

This binarization circuit A amplifies and outputs the above-mentioned original video signal, and also corrects this amplified video signal with a filter 8 that corrects the difference in brightness level depending on the position of the screen 5, and converts it into a binarized image. This is a circuit that outputs as a signal.

That is, in this binarization circuit A, as shown in FIG. 5, the original video signal is amplified by the buffer 6 and outputted, and the video signal _a
(see FIG. b)] is supplied to the switch S1, the plus input terminal of the comparator 7, and the input terminal of the filter 8, respectively.

Further, the signal corrected by the filter 8 is attenuated by an attenuator 9 so that it becomes lower than the video signal level on which the noise component is superimposed at each point other than the crack part, and the signal a adjusted by the attenuator 9 is _B (see FIG. 6c) is supplied to the negative input terminal of the comparator 7.

Furthermore, the comparator 7 compares the output signal a _A amplified by the buffer 6 and the signal whose attenuation is adjusted by the attenuator 9 and binarizes it, and outputs the binarized signal a _C of the binarization circuit A. 6d], the signal is supplied to one input terminal of the adder circuit R via the input terminal of the crack signal detector B (see FIG. 1) and the switch S1.

As shown in FIG. 1, the crack signal detector B has two
The binarized signal a _C that has been binarized by the digitization circuit A is input, and this signal is scanned within a window set in the horizontal scanning direction in order to detect the crack signal by utilizing the fact that the crack extends almost linearly. This circuit detects the presence or absence of a black level signal in the binary signal _aC for each horizontal scan.

As shown in Fig. 5, this crack signal detector B
generates a window pulse b _A [see Fig. 6 e] based on the horizontal blanking signal B _H [see Fig. 6 a], and uses this window pulse b _A to generate a signal from the binarized signal a _C. Crack signal b _B [See Figure 6 f]
It is now possible to extract crack signals and detect crack signals.

This horizontal blanking signal B _H is applied to the delay circuit 1
0, is adjusted to form the rising edge of window pulse _bA , is output as a signal of this delay circuit 10, and is input to a monostable multivibrator 11.

Furthermore, this monostable multivibrator 11
The window pulse width is adjusted and outputted based on the output signal from the delay circuit 10 to form the window pulse b _A , and the output signal of the monostable multivibrator 11 is 2
Together with the binary signal a _C , which is the output signal of the digitization circuit A, it is supplied to an AND circuit 12 (AND circuit), and further supplied to an AND circuit 23 that constitutes a crack length measuring device D. It's becoming like that.

In this AND circuit 12, the binary signal a _C and the window pulse b _A are ANDed, and only the crack signal b _B (see Fig. 7C) is taken out. The output of the signal detector B is input to a follow-up comparison type crack tip detector C.

In addition, in this AND circuit 12, even when two or more pulses of the binary signal a _C occur within the window of one scanning line, the monostable multivibrator 1
3, the output _bB of the AND circuit 12 has only one pulse.

As shown in Fig. 1, the tracking comparison type crack tip detector C detects the crack signal detected by the crack signal detector B.
b _B is input, and in order to detect the tip of a crack, this crack signal b _B is detected to be greater than or equal to a pre-specified value for several scanning lines from before and after the tip of the measurement allowable band extending in the vertical scanning direction. In this case, extend this measurement allowable band, and if it is less than that value,
This is a circuit for contracting this measurement allowable band, and is also a circuit for storing this expanded or contracted measurement allowable band.

As shown in FIG. 5, the follow-up comparison type crack tip detector C inputs the crack signal b _B , and based on the crack tip intermediate memory value that temporarily indicates the crack tip of the previous frame,
The tip of the crack is detected and output for each frame.

This counter 14 increases or decreases its value depending on whether or not a crack tip is detected within one frame.

At the start of a frame, this counter 15 uses the vertical blanking signal B _V input to its load terminal (LOAD) as a load signal to load the stored value of the counter 14, and inputs it to its clock terminal (CLOCK). It operates as a timer using the horizontal blanking signal B _H as a clock signal and the value stored in the counter 14 as an initial value, and a crack tip detection start signal c _A as the timer end signal (see Fig. 8b). ], and this signal c _A is supplied to the monostable multivibrator 16, and is also sent to the crack length measuring device D via the switch S2 as the output of the follow-up comparison type crack tip detector C. supply is becoming available.

This monostable multivibrator 16 determines the permissible band for crack tip detection, and here, the crack tip detection permissible band pulse c _B is set only during the number of scanning lines N (integer) (see Fig. 8c). is now output, and this pulse c _B is output from the AND circuit 1
7 is supplied to one input terminal of the counter 1.
The rising edge of this pulse _cB is supplied to the load terminal of No. 8 as a load signal.

This AND circuit 17 inputs the crack signal b B which is the output from the crack signal detector _B and the pulse c _B from the monostable multivibrator 16, and performs an AND operation between this crack signal b _B and this pulse c _B. , the ANDed signal c _C [see Figure 8 d] is output as the tip crack signal c _C , and this signal c _C is supplied to the clock terminal of the counter 18 as a clock signal. It's summery.

This counter 18 loads the initial value [here M] from the initial value setter 19 at the rising edge of the pulse c _B from the monostable multivibrator 16, and also loads the tip crack signal c _C from the AND circuit 17. It is designed to be input as a clock signal, and its initial value and the number of pulses of the tip crack signal c _C are compared within the allowable time for detecting the crack tip determined by pulse c _B , and the tip crack signal c When the number of pulses of _C is detected to be greater than or equal to the initial value given in advance, a count increase signal c _D is sent to the terminal (UP) of the counter 14 in order to extend the measurement allowable band (see Figure 8 e). , and also do not output the decrease signal c _E [see Figure 8 f]. If the number of pulses of the tip crack signal c _C [see Figure 8 g] is less than the initial value, the measurement allowable band In order to shrink the count, a decreasing signal c _E ′ [see Figure 8 j] is output to the terminal (DOWN) of the counter 14, and an increasing signal c _D ′ [see Figure 8 h] is not output. ing.

Also, from this counter 18, a tip crack signal c _C
The number of pulses may be compared with its initial value and an increase signal may be issued only when the number of pulses exceeds the initial value, which is a predetermined numerical value.

To explain the action of this follow-up comparison type crack tip detector C on a drawing, as shown in FIG. (an integer smaller than N), move this part P downward by one position,
Similar measurements are repeated, and when the number of binarized signals is less than M, this portion P is moved upward by one position and the same measurements are repeated.

As shown in Fig. 1, a crack length measuring device D is provided, and a crack tip detection start signal c _A from a follow-up comparison type crack tip detector C is inputted via a switch S2 _. This is used as a memorized value to measure the crack length.

As _shown in FIG.
c _A is output as a crack tip signal d _B (see Figure 9 c).

This delay circuit 20 is set to an appropriate value in order to correct the deviation between the tip detection starting point and the tip in the follow-up comparison type crack tip detector C, and this crack tip signal _dB is flipflop 2
1 reset terminal (RESET).

In addition, the vertical blanking signal B _V is sent to the delay circuit 2 in order to correct the starting point of the crack to the end point of the notch 2.
2, the crack base signal _dA [Fig. 9b
Reference] is supplied to the set terminal (SET) of the flip-flop 21.

This flip-flop 21 receives the crack base signal d _A
is a negative logic set signal, and the crack tip signal d _B is a negative logic reset signal, and the output of this flip-flop 21 is the crack length signal d _C [see Figure 9 d].
The signal is supplied to one input terminal of the AND circuit 23 via the switch S2.

This AND circuit 23 is connected to the flip-flop 21
The crack length signal d _C which is the output of C and the crack signal detector B
The ANDed crack length pulse _{d D [} see Figure 9 e] is input to the crack length converter E as the output of the crack length measuring device D. It's becoming like that.

As shown in Figure 1, the crack length converter E performs range switching, averaging, sampling, and unit conversion in order to convert the crack length based on the crack length pulse d _D from the crack length measuring device D. This converted crack length is supplied to a digital display device and a printer F.

As shown in FIG. 5, the crack length converter E clears the clear terminal (CLEAR) of the counter 25 by inputting the vertical blanking signal B _V [see FIG. 10 a] to the frequency dividing circuit 24. Signal e _A [10th
(see FIG. 10) and a load signal e _B (see FIG. 10, c) is output to the load terminal of the time converter 26.

This counter 25 is a circuit that counts and outputs the crack length pulse d _D (see Fig. 10 d) from the crack length measuring device D using the clear signal e _A from the frequency dividing circuit 24 as a preset signal. In order to average the lengths, the crack lengths for several hundred frames are integrated here, and this integrated count number is output to the time converter 26.

The time converter 26 is configured to load the count accumulated by the counter 25 when the load signal e _B from the frequency dividing circuit 24 is input, and further converts the input count to the corresponding time. In order to convert this count number, the clock generator 27
The converted pulse width e _C (see FIG. 10e) is supplied to a crack length converter 28.

This crack length converter 28 inputs the pulse converted by the time converter 26 and counts its width e _C using a variable clock from a clock generator 29, thereby averaging and sampling the crack length. transformation,
It performs unit conversion and range switching.
First, a preset is performed using the input from the initial value setter 30, and after this preset, the time converter 26
The pulse width e _C from is converted into the average value or sampled value of the corresponding crack length, taking unit conversion into consideration, and the converted crack length is supplied to the digital display device and printer F. . Of course, the units may be μm, mm, cm, etc.
The range can also be changed automatically.

As a result, by setting the preset to length _L1 as shown in Figure 2, the crack length L
can also be easily converted into the output crack length _L2 .

As shown in Figure 1, the digital display device and printer F is a circuit that inputs the converted crack length from the crack length converter E into the printer, displays, records, and outputs the crack length. be.

As shown in FIG. 5, in this embodiment, a display converter 31 common to the digital display device and the printer is provided to simplify the configuration.

This display converter 31 inputs the converted crack length from the crack length converter E and converts the crack length into an input format that meets the input/output standards of each display device. ) and a printer 33 that prints out the crack length on recording paper in a format that matches each input/output format.

By the way, in addition to the above-mentioned functions, the device of this embodiment has a marker 35 on the CRT (cathode ray tube) 37 that indicates the allowable range for crack length measurement (see Figure 4), and a marker 35 for indicating the allowable range for measurement of the crack length. Carrier plate marker 36 of a certain length provided on the extension [first
2] can be displayed superimposed on the video signal _aA or the binarized image _aC by selecting the switch S2, and these will be explained below.

As shown in FIG. 1, a carrier plate circuit G is provided, and as shown in FIG.
Based on the crack base signal d _A , a carrier plate marker signal d _C ′ indicating a certain length is created.

This signal d _C ' has its pulse length variably adjusted and becomes a wavelength signal that can be adjusted to the same pulse as the crack length signal d _C , and is sent to the AND circuit 23 and the AND circuit 34 via the switch S2. supply is becoming available.

The calibrated marker signal d _C ′ (see FIG. 11b) supplied to the AND circuit 34 is ANDed with the window pulse b _A and becomes the marker pulse r1 (see FIG. 11c), which is sent to the adder circuit. R
By adding the video signal a _A [see Figure 11 d] or the binary image a _C selected by the switch S1 and this marker pulse r1, the output video signal is obtained. r2 (see FIG. 11e) is created and supplied to the CRT 37.

On the other hand, the carry plate marker signal _dC ' supplied to the AND circuit 23 is used to adjust and set each variable part to a reference value, and is used to adjust the length of a certain part of the test piece projected on the CRT in advance. Measure the crack length by the following means, set the carrier plate marker signal d _C ′ at that position on the CRT, convert and convert as described above, and compare the output crack length with the length measured by other means. , used to adjust clocks, etc.

This results in the advantage of fewer erroneous measurements.

Furthermore, a marker on a CRT screen, which will be described later, is compared with the image, and the base end of the crack length is also adjusted.

The marker so regulated is CRT37
For example, the variable part of the calibrate marker G and the variable part of the crack length proximal end of the crack length measuring instrument D can be measured on the CRT37 screen. This has the advantage that the length in the vertical direction on the screen can also be measured by manually adjusting it while visually observing it.

As described in detail above, according to the automatic crack length measuring device of the present invention, a video signal containing the crack 3 is input, and measurement tolerances for noise removal that are effective against noise included in this video signal are provided. By establishing a zone, measuring the crack length within that zone, and then tracking and comparing the tip of the crack to detect it, it is possible to accurately and automatically measure and record the crack length, as well as continuously. The advantage is that it can be done.

[Brief explanation of drawings]

The figures show an automatic crack length measuring device as an embodiment of the present invention, in which Fig. 1 is an overall configuration diagram showing its basic configuration, Fig. 2 is a schematic diagram showing its test piece,
Figures 3a and 4 are schematic diagrams for explaining the state of the screen, Figure 5 is its block diagram, Figures 6 to 11 are waveform diagrams of each part, and Figure 1
Figure 2 is a schematic diagram showing the marker. 1... Television camera, 2... Notch, 3... Crack, 4... Test piece, 5... Screen, 6... Buffer, 7... Comparator, 8... Filter, 9...
...attenuator, 10...delay circuit, 11...monostable multivibrator, 12...AND circuit,
13... Monostable multivibrator, 14,15
... Counter, 16 ... Monostable multivibrator, 17 ... AND circuit, 18 ... Counter, 1
9...Initial value setter, 20...Delay circuit, 21...
...Flip-flop, 22...Delay circuit, 23...
... AND circuit, 24 ... Frequency divider circuit, 25 ... Counter, 26 ... Time converter, 27 ... Clock generator, 28 ... Crack length converter, 29 ... Clock generator, 30 ... Initial value Setting device, 31... Display converter, 32... Digital display, 33... Printer, 34... AND circuit, 35... Marker, 3
6...Carry plate circuit, 37...CRT, A
...Binarization circuit, B...Crack signal detector, C...
Follow-up comparison type crack tip detector, D...Crack length measuring device, E...Crack length converter, F...Digital display device and printer, G...Carry plate marker, L...Crack length, L ₁ ... Length, L ₂ ... Output crack length, P ... Crack tip, R ... Addition circuit,
S1, S2...Switch, B _H ...Horizontal blanking signal, B _V ...Vertical blanking signal.

Claims (1)

[Scope of Claims] 1. A binarization circuit that binarizes a video signal containing information on the crack, and a binarization circuit that binarizes the video signal containing information on the crack, in order to automatically measure the length of a crack that occurs in a test piece. a crack signal detector that detects the presence or absence of a black level signal in the binarized signal for each horizontal scan within a window set in the horizontal scanning direction in order to detect a crack signal from the converted video signal; Based on the signal from the crack signal detector, if the crack signal is detected at a predetermined value or more for several scanning lines from the front and back of the measurement permissible band extending in the vertical scanning direction, the measurement is permitted. A follow-up comparison type crack tip detector that detects the crack tip by extending the band and contracting the measurement allowable band when the band is less than the numerical value, and storing the measurement allowable band; and a crack length measuring device that outputs a crack length signal.
Automatic crack length measuring device. 2. The automatic crack length measuring device according to claim 1, wherein the crack length measuring device is connected to a display device that receives a signal from the crack length measuring device and displays the length of the crack.