JPH0533332B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) In measuring stress distribution information of a test object using thermoelastic effect, the present invention provides an image of the test object loaded with a load signal using an infrared detector. In a stress imaging system that scans horizontally and vertically with a spot and displays stress distribution as an image based on the obtained temperature data,
The present invention relates to an automatic phase adjustment method in a stress imaging system, which adjusts the phase (timing) of temperature data detection with respect to a load signal.

(Prior Art) Many systems have been proposed for displaying stress distribution on a display device based on temperature distribution data obtained by scanning a subject with an image spot of an infrared detector.

An example of this conventional stress imaging system will be briefly explained.

FIG. 2 is a diagram for explaining the outline of a stress imaging system used to explain the conventional automatic phase adjustment method and the present invention. Reference numeral 1 denotes an object to be examined, and a load is applied to the object 1 by a load shaker 2. When this load signal is applied, a temperature distribution is generated on the surface of the object 1 due to the thermoelastic effect in a distribution corresponding to the stress distribution. 3 is an infrared scanner that scans this object 1 with an image spot, and reads the analog temperature data of the object 1 through this horizontal and vertical scanning, and after suitably amplifying it in the next stage signal processing system 4, sends it to the next A/ The D converter 5 converts it into digital temperature data and supplies it to the next stage computer 6. Reference numeral 7 denotes a timing circuit that determines the timing for supplying the load to the load shaker 2, and also supplies timing pulses to the A/D converter 5 and computer 6 to determine the timing for inputting digital temperature data to the computer 6.

This system is configured to convert the thus captured temperature data into stress distribution data through computer processing, and display the data as a stress image on the display device 8.

By the way, since the temperature change caused by the thermoelastic effect of the test object is generally small, the S/N ratio is extremely small in stress measurement using such a low-level signal, making it difficult to put it to practical use in displaying stress distribution images. Can not.

(Problems to be Solved by the Invention) By the way, in the conventional stress imaging system using the thermoelastic effect, the load signal applied to the object and
There is a slight phase shift between this load signal and the stress signal generated on the subject. Because of this,
It is necessary to match the timing of detecting the temperature data of the object to the phase of the stress signal.

However, the stress signal due to the thermoelastic effect is a very small signal, and its frequency is 1 to 1.
Since the frequency is as low as about 50 Hz, it is extremely difficult to perform this phase alignment manually.

Attempts have also been made to automatically perform this phase matching, but in order to obtain the required accuracy, it is necessary to scan the same measurement location multiple times and integrate the obtained temperature data to improve the S/N ratio. It is necessary. However, if temperature data is integrated by scanning the same number of times for all phases, it will take a long time to acquire the temperature data, which is not practical.

An object of the present invention is to provide an automatic phase adjustment method in a stress imaging system that automatically performs such phase adjustment in a short time.

(Means for solving the problem) In order to achieve this objective, according to the present invention,
In order to display the stress distribution as an image based on the temperature data obtained by horizontally and vertically scanning an object to which a load is applied periodically with an image spot of an infrared detector, the temperature with respect to the load signal of this periodic load is calculated. In an automatic phase adjustment method in a stress imaging system that adjusts the phase of data detection, preliminary stress values are calculated by integrating temperature data at the same measurement point for each set different phase. A step of determining a preliminary phase corresponding to the maximum preliminary stress value of The present invention is characterized by comprising a step of adjusting the phase to give the maximum stress value among these stress values.

Furthermore, in carrying out the present invention, in order to set different phases, the period of the load signal is detected,
It is preferable to set phase data that can be set to different delay times based on this detected cycle, and to determine the timing of temperature data detection based on this phase data.

Furthermore, in carrying out the present invention, temperature data detection forms compression and tension signals, respectively, which have a phase determined by the phase data with respect to the load signal and have the same period as this load signal, and these compression and tension signals It is preferable to form a horizontal effective timing signal by performing a logical operation on the horizontal scanning timing signal and the horizontal scanning timing signal, and to detect the temperature data for each horizontal effective timing signal for each set different phase.

Further, in a preferred embodiment of the present invention, the phase data can be set manually or automatically to set the phase that provides the maximum stress value among the stress values.

(Function) As described above, according to the automatic phase adjustment method of the present invention, the image spot is scanned a plurality of times for the same measurement point at each of the different phases between 0° and 180°, and the image spot is scanned at each phase. The integrated temperature data is determined, the preliminary stress at each phase is determined from the integrated temperature data, the maximum preliminary stress is selected from among these preliminary stress values, and the preliminary phase corresponding to this maximum preliminary stress is first determined. Next, only for the peripheral phases including this preliminary phase, the same measurement point is scanned more times than the number of scans used when calculating the preliminary stress, and the accumulated temperature data at each phase is obtained, and from these accumulated temperature data. Stress values at each phase are determined, and the phase of temperature data detection is adjusted to the phase that provides the maximum stress value among these stress values.

Conventionally, scanning was performed approximately 256 times for each phase, but according to the present invention, the corresponding number of scans is approximately 64 times for determining the preliminary phase for each phase, and approximately 64 times for determining the phase of maximum stress. Since only about 256 scans are required per scan, the total scan time is reduced to less than half, which is significantly shorter than the conventional method.

(Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First, the present invention will be described with reference to an apparatus shown in FIG. 1 for implementing the automatic phase adjustment method for a stress imaging system of the present invention.

First, a load signal is supplied from the load shaker 2 to the periodic signal detection means 11, one period of the load signal is determined, a periodic signal (time delay signal) having this information is generated, and the compression and tension signal forming means 13 supply to.
In this compression and tension signal forming means 13, a phase of, for example, 45° is set relative to the load signal as an initial phase, and compression and tension signals having the same period as that of the load signal are respectively formed.

Next, these compression and tension signals and the scanner 3
The horizontal scanning timing signal from
The object 1 is scanned with an image spot based on this horizontal effective timing signal, the temperature data is taken into the computer 6, and this temperature data is converted into a video signal by the temperature data-stress distribution data conversion means 6a. Therefore, one screen of stress images is displayed on the display device 8.

Next, the cross point X of the horizontal and vertical cursors h and v is set at the portion R where the stress value is high. Subsequently, vertical scanning by the scanner 3 is advanced to the vertical position of the cursor, the vertical scanning is stopped, and horizontal (line) scanning is performed at this position.

At this time, since the phase is initially set to 45 degrees, the temperature data obtained by scanning, for example, 64 times for several points near the cursor cross point 5 to the computer 6, and the detection means 17 integrates the temperature data to obtain compressive and tensile stresses, and calculates the difference between the compressive and tensile stresses to obtain stress values. After that, the average value of the stress values for these several points is calculated, and this average stress value is input to the computer 6.
is stored in the memory 6c.

By the way, in this invention, a command is given to the A/D converter 5 from the preliminary scan/main scan setting means 18,
A preliminary scan is performed to determine the preliminary phase corresponding to the maximum prestress value. For this reason, the phase set to the sharpest position is changed, and the same measurement location is scanned, for example, 64 times for each phase. From the temperature data obtained by these scans, an average stress value is determined as a preliminary stress value in the same manner as described above and is stored in the memory 6c.

In this way, after the prestress values obtained by sequentially changing the phase are stored in the memory 6c, these are called to the phase adjustment means 19, where the maximum prestress value among these prestress values is determined. , a phase corresponding to this maximum prestress value is set, this phase information is sent to the preliminary scanning/main scanning setting means 18, and the main scanning of the image spot is performed using only the set phase and the phases around it.

This main scan is performed, for example, 256 times at the same measurement location for each phase. Stress values are obtained from the integrated temperature data obtained for each phase in the detector 17 in the same manner as described above, these stress values are temporarily stored in the memory 6c, and then these stress values are transferred from the memory 6c to the phase adjustment means 19. They are called sequentially or simultaneously to compare the magnitudes, determine the phase that gives the maximum stress value, and set that phase in the scanner 3 or the phase data generating means 12. Alternatively, the phase of the scanner 3 or the phase data generating means 12 is adjusted while the phase adjustment means 19 determines whether the stress value is the maximum value, and when the stress value is determined to be the maximum stress value, the phase at that time is fixed.

Thus, according to this invention, the N
Preliminary scans with a small number of scans are performed for each phase to predict the position that will give the maximum stress, and then main scans with a large number of scans are sequentially performed on several phases in the vicinity including this predicted phase to obtain the maximum stress. The phase that gives the stress value can be found with high precision and in a short time, and the phase can be adjusted to that phase.

Therefore, even if there is a phase shift between the load signal and the stress signal, temperature data can always be taken into the computer in an optimal state, and stress can be displayed in an optimal measurement state.

FIG. 4 is a block diagram showing a part of the device from periodic signal generation to obtaining a horizontal effective scanning timing signal for carrying out the automatic phase adjustment method of the present invention, and FIG. 5 is a signal waveform diagram for explaining the same. It is.

First, the load signal is made into a sine wave signal as shown in FIG. 5A. This load signal is supplied to a comparator 53 via an amplifier 51, which generates an output signal of a constant level when the amplitude of the load signal is equal to or higher than the zero level. This signal is shown in FIG. 5B.

The output signal from the comparator 53 is supplied to rising and falling differentiating circuits 55 and 57, respectively, to obtain differentiated signals as shown in FIG. 5C and D. These rising differential signals and falling differential signals are used as compression start pulses and tension start pulses, respectively, as will be described later.

Next, the rising differential signal is generated by the periodic signal generating means 1.
Supply to 4. In this embodiment, this means includes two monomultivibrators 59 and 61 for time delay, a one-period counter 63, and a latch circuit 65.
It consists of:

On the other hand, 67 is a clock pulse generator that generates clock pulses at any suitable frequency, and is supplied to the clock input of the one-period counter 63. A rising differential circuit 55 is used as a signal input to the counter 63.
The differential signal from the monovibrator 59 and 61 is supplied via two monovibrators 59 and 61. Therefore, this first differential signal starts clock counting, and the next differential signal stops the counting. This count value is stored in the latch circuit 65, and on the other hand, the output from the monomultivibrator 59 is supplied to the latch circuit 65 as a latch pulse. The latch circuit 65 outputs this count value as one-cycle data representing one-cycle time.
Central processing unit 71 (hereinafter referred to as CPU) of computer 6 via input/output port 69 as Ts
send to

In the CPU 71, the phase data generation means 1
2 to obtain phase data Tθ from this one-cycle data Ts.
is calculated and transmitted to the compression and tension signal forming means 13.
supply to. The phase here corresponds to the phase difference between the cycle of the load signal and the cycle of measuring temperature data. This phase data Tθ represents a time delay with respect to the load signal. For this phase data, the number of divisions of one period is determined in advance as Ns,
For this number of divisions Ns, you can arbitrarily set N (0≦
N≦Ns) and calculate from Tθ=Ts×N/Ns. The value of N can be set by inputting it from the CPU 71, and can also be set according to the stress value, as will be described later.

This phase data Tθ is sent to the compression counter 7 of the compression and tension signal forming means 13 via the input/output port 73.
5 and tension counter 77. in this case,
Compression and tension counters 75 and 77 are supplied with compression start pulses and tension start pulses from differentiating circuits 55 and 57, respectively, and are loaded with respective phase data using these start pulses.

These counters 75 and 77 can be countdown counters or countup counters, but the case where they are countdown counters will be explained. In this case, the supplied phase data
For example, Tθ corresponds to a phase of 45°, a count corresponding to this is set in the compression counter 75, and the clock from the clock pulse generator 67 is subtracted from the count (FIG. 5F). When this count value becomes zero or less than zero, an underhollow signal is generated from this counter 75, so this is sent to a flip-flop (hereinafter referred to as FF) 79, and this FF79
is set to form a compressed signal (FIG. 5H).

Similarly, the phase data Tθ is loaded into the tension counter 77 by the tension start pulse from the falling differentiation circuit 57, the clock is subtracted, and when the counted value becomes zero or less than zero, an under-hollow signal is generated. (Figure 5G), this signal causes FF79
and inverts the compression signal described above to form a tension signal.

In this way, based on the periodic signal, it is possible to form compression and tension signals, respectively, which have an arbitrary phase with respect to the load signal and have the same period as the load signal.

Next, in order to form a horizontal effective timing signal from these compression and tension signals and the horizontal scanning timing signal, the compression and tension signals are supplied from the FF 79 to the logic operation circuit 15. On the other hand, this logic operation circuit 15 is supplied with a horizontal scanning timing signal H BL (FIG. 5 I) from the scanner 3, and, for example, the logical product of both signals is taken to determine the horizontal effective timing signal (FIG. 5 J) for the compression period. (shown as a solid line in FIG. 5J) and a horizontal effective timing signal (effective HBL) (shown as a dotted line in FIG. 5J) for the tension period, respectively.

The horizontal effective timing signal (effective HBL) obtained in this manner is sent to the scanner 3, and temperature data of the subject 1 is measured at such horizontal scanning timing (FIG. 1).

Next, by manually or automatically changing the value of N described above, the phase data Tθ can be sequentially changed within the range of 0° to 180°, thereby changing the phase of temperature data detection.

The invention is not limited to the embodiments described above. For example, each of the above-mentioned means 11,1
3, 15, and 18 may have configurations other than those described here, and these can be easily constructed using ordinary electronic techniques. Moreover, the phase data generation means 1
2. The detection means 17 may be made to function in the CPU of the computer 6, or separate CPUs may be provided, each or a portion of which is common. Further, the logic operation circuit 15 may be made to function in these CPUs. Further, separate means may be provided for setting the preliminary scan and the main scan.

In addition, the above-mentioned logic operation circuit 15 and detection means 1
7. Phase adjustment means 19, phase data generation means 1
2. The preliminary scanning/main scanning setting means 18 and other components can be easily formed or functioned by using or combining conventionally commonly used electronic elements and/or electronic circuits.

Furthermore, the present invention is suitable for application to point-scan or area-scan type stress imaging systems.

(Effects of the Invention) As is clear from the above description, according to the automatic phase adjustment method of the present invention, there is a slight difference between the load signal applied to the object and the stress signal generated in the object due to this load signal. However, even if there is a phase shift, the phase is automatically shifted and a small number of preliminary scans are performed at each different phase to obtain each preliminary stress value (preferably the average stress value), and these preliminary stress values are calculated. Among them, the preliminary phase that gives the maximum preliminary stress value is determined, and then main scanning is performed many times using only this preliminary phase and the phases around it to find the phase that gives the maximum stress value, and the phase is adjusted to that phase.

Therefore, according to the present invention, it becomes possible to perform phase adjustment more simply and easily, more precisely, and in a shorter time than before.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an apparatus for explaining the automatic phase adjustment method in the stress imaging system of the present invention, Fig. 2 is a block diagram showing a conventional stress imaging system, and Fig. 3 is an explanation of the present invention. FIG. 4 is a block diagram of essential parts to explain the invention, and FIG. 5 is a signal waveform diagram to explain the invention. 1... Subject, 2... Load shaker, 3... Scanner, 4...
Signal processing system, 5...A/D converter, 6...Computer, 6a...Control signal generation means, 6b...Temperature data-stress distribution data conversion means, 6c...Memory, 7
... timing circuit, 8 ... display device, 9 ... control circuit, 11 ... periodic signal detection means, 12 ... phase data generation means, 13 ... compression and tension signal formation means, 1
5...Logic operation circuit, 17...Detection means, 18...Preliminary scanning and main scanning setting means, 19...Phase adjustment means, 5
1... Amplifier, 53... Comparator, 55... Rising differential circuit, 57... Falling differential circuit, 59, 6
DESCRIPTION OF SYMBOLS 1... Mono multivibrator, 63... One period counter, 65... Latch circuit, 67... Clock generator, 69, 73, 83... Input port, 71... Central processing unit (CPU), 75... Compression counter, 77...
Tension counter, 79...Flip-flop.

Claims (1)

[Claims] 1. In order to visually display stress distribution based on temperature data obtained by horizontally and vertically scanning an object to which a load is applied periodically with an image spot of an infrared detector, In an automatic phase adjustment method for a stress imaging system that adjusts the phase of temperature data detection with respect to the load signal of a target load, preliminary scanning is performed multiple times for each set different phase to collect temperature data at the same measurement point. a step of calculating a preliminary stress value by integrating and determining a preliminary phase corresponding to a maximum preliminary stress value among these preliminary stress values;
A phase in which the main scan is performed more times than the number of preliminary scans for each of the peripheral phases including the preliminary phase, temperature data is integrated to obtain a stress value, and the maximum stress value among these stress values is obtained. 1. A method for automatic phase adjustment in a stress imaging system, comprising: a step for adjusting the phase of the stress image system; 2. In the automatic phase adjustment method in a stress imaging system according to claim 1, in order to set the different phases, detect the period of the load signal, and set different delay times based on the detected period. 1. An automatic phase adjustment method, comprising: setting phase data that can be set to , and determining timing of detecting temperature data based on the phase data. 3. In the automatic phase adjustment method in a stress imaging system according to claim 1, the temperature data detection includes compression having a phase determined by the phase data with respect to the load signal and having the same period as the load signal. and a tension signal, respectively, and perform a logical operation on these compression and tension signals and the horizontal scanning timing signal to form a horizontal effective timing signal, and adjust the temperature for each horizontal effective timing signal for each set different phase. An automatic phase adjustment method in a stress imaging system characterized by performing data detection. 4. In the automatic phase adjustment method in a stress imaging system according to claim 2, the phase data may be set manually or automatically so as to set the phase that gives the maximum stress value among the stress values. Features: Automatic phase adjustment method in stress imaging system.