JPH05107211A - Defect determining apparatus by thermography - Google Patents

Abstract

PURPOSE:To enable highly-precise detection of a defect from temperature information corresponding to the position of a moving specimen CONSTITUTION:A temperature change detecting means 7 for detecting the part of a temperature change of a temperature signal and a first defect level detecting means 8 for detecting a first defect level from an output of this temperature change detecting means 7 are provided. Moreover, an apparatus is constructed by providing it with a second defect level detecting means 12 for detecting a second defect level from an output of the temperature change detecting means 7 and a defect determining means 15 for determining a defect of a body O to be detected, on the basis of an output of this second defect level detecting means 12 and a line movement pulse.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defect determination device by thermography for detecting a defect from a temperature distribution change of an object to be detected such as a running belt.

[0002]

2. Description of the Related Art Conventionally, when detecting a defect in an object to be detected such as a running steel plate, papermaking or the like, a thermography device is used. Such a device is constructed as shown in FIG. The traveling detection target O is scanned by the scanning unit 1 in a direction orthogonal to the traveling direction F of the detection target O (traveling direction SC), and the infrared detector 2 detects infrared rays emitted from the detection target O. .. At this time, for example, if there is an abnormally high temperature portion (or low temperature portion) with respect to the normal temperature portion of the detected object O, infrared rays different from the normal portion are detected. The detected infrared ray is converted by the temperature converting section 3 into a temperature signal corresponding to the energy of the infrared ray and sent to one input of the comparing section 4. The defect level signal set by the defect level setting unit 5 is sent to the other input of the comparing unit 4 as a reference value. Comparison unit 4
When a signal of a defect level signal or higher, that is, a temperature signal of an abnormal portion of the object to be detected is input from the temperature conversion unit 3, the signal is output as a defect signal via the buffer amplifier 6 to detect the defect of the object to be detected O. I was trying to judge.

[0003]

However, in the above-mentioned conventional defect judgment, the defect is judged only by the magnitude of the defect signal. For this reason, if the judgment level is lowered in order to surely detect a small level defect, the signal level due to minute noise or the like will also be detected as a defect signal, which will cause erroneous detection. Further, in order to avoid erroneous detection of minute noise, raising the determination level reduces erroneous detection, but conversely misses small level defects. in this way,
In the conventional device, it is difficult to detect a minute defect and it is impossible to detect with high precision. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a defect determination device by thermography that can detect a defect with high accuracy based on temperature information corresponding to the position of a traveling object to be detected.

[0004]

In order to achieve such an object, the present invention, for example, as shown in FIG. 1, a scanning unit 1 for scanning a traveling object to be detected O in a direction orthogonal to its traveling direction, An infrared detector 2 for detecting infrared rays emitted from the detected object O, a temperature conversion unit 3 for converting an output of the infrared detector 2 into a temperature signal, and a defect of the detected object O having a predetermined value or more are determined. In a thermographic defect determining apparatus having defect determining units 4 and 5, a temperature change detecting unit 7 for detecting a temperature change amount of a temperature signal, and a first defect level is detected from an output of the temperature change detecting unit 7. Defect level detecting means 8; second defect level detecting means 12 for detecting the second defect level from the output of the temperature change detecting means 7; and output of the second defect level detecting means 12,
The defect determination unit 15 determines a defect of the detected object O based on the line movement pulse.

[0005]

According to the present invention having such a configuration, the defects of the object to be detected are detected by dividing them into large defects and small defects,
If a large defect is detected, it is output as it is.If a small level defect is detected, the defect signals per unit length are sequentially added, and the added output is compared with a predetermined defect level. By making a determination, it is possible to detect a small defect without overlooking, so that it is possible to make a highly reliable defect determination.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a thermographic defect determination apparatus of the present invention will be described below with reference to FIGS.
The parts corresponding to the conventional ones are given the same reference numerals and the description thereof will be omitted. The first difference of the present invention from the conventional example of FIG. 3 is that in the present example, the first defect level detection unit 8 that detects a large defect of the detected object O and the second defect that detects a small defect. The second difference is that the detection unit 12 is provided.
When a small defect is detected, the defect signal detected by the second defect detection unit 12 is used as the defect determination unit 15 together with the line information.
In addition to this, the unit length of the object to be detected O is added, and the defect is finally determined.

The structure for determining the defect level of the object to be detected O will be described below. The temperature change detection unit 7 is composed of, for example, a differentiator or the like, inputs a temperature signal for each scan from the temperature signal conversion unit 3, and if the temperature of the detected object O is abnormal, a defect signal The variation is extracted and output to the first defect level detecting unit 8 and the second defect level detecting unit 12, respectively. The first defect level detecting unit 8 detects a large defect, and includes a defect level setting unit 9 and a comparing unit 1.
It consists of zero. For large defects, the defect level setting unit 9 sets a corresponding required defect level in advance and sends it to one input of the comparison unit 10 as a reference level. The level of the defect level setting unit 9 can be set arbitrarily. The change of the temperature signal extracted by the temperature change detecting unit 7 is input to the other input of the comparing unit 10 and compared with a reference defect level. When the defect level is exceeded, the buffer amplifier 11 outputs a defect signal. Is output via. Since a large defect is less likely to be affected by noise or the like, if even one defect level is detected, it is determined as a defect. On the other hand, the second defect level detection unit 12 detects a small defect and is composed of a defect level setting unit 13 and a comparison unit 14. For small defects,
The defect level setting unit 13 presets a corresponding required defect level and sends it to one input of the comparing unit 14 as a reference level. The level of the defect level setting unit 13 can also be set arbitrarily. The change of the temperature signal extracted by the temperature change detecting unit 7 is input to the other input of the comparing unit 14 and is compared with a reference defect level. When the defect level is exceeded, the defect determining unit determines that the defect signal is a defect signal. 15
Is output to.

The defect detection of the object to be detected O will be described with reference to FIG. A is a waveform showing a temperature signal for one scan of the detected object O detected by the infrared detector 2 in the scan of the scanning unit 1, and shows that it is in a normal temperature state. B is
Only the rising and falling portions of the temperature signal of A are detected in the differential waveform of the temperature signal detected by the temperature change detecting unit 7, and there is no abnormal temperature portion. When the detected object O runs and there is an abnormal large temperature change, for example, the detected temperature signal has a waveform of C. The temperature signal of C is differentiated, and the temperature change amount becomes like D. By setting a large defect level G for this change, for example, a signal exceeding this level G is extracted as a defect signal. Further, E is a detected waveform of the temperature signal when the detected object O has a small defect. Also in this case, similarly to the setting of the large defect level G, the small defect level S is set to the differential waveform shown in F obtained by differentiating the temperature signal of E, and the signal of the level S or higher is taken out as the defect signal. ing.

In the defect judgment unit 15, since a small defect has a small change in temperature signal and is confused with noise or the like, it is usually not judged as a defect by one detection, and a defect is generated according to the occurrence frequency per unit length of the object to be detected O. To judge. The defect determination unit 15 includes, for example, a serial-in / parallel-out type n-bit shift register 16, an analog adder 17,
It is composed of a defect reference setting unit 18 and a comparison unit 19. From the second defect level detection unit 12 described above, the defect signal of the detected small defect is applied to one input of the shift register 16, and the line movement pulse L is applied to the other input of this register 16. The line movement pulse L is input from, for example, a pulse generator (not shown) provided in the production line of the detection target O. The shift register 16 operates using the line movement pulse L as a clock signal. Assuming that the unit length to be determined as a defect of the detected object O is, for example, 1 m and the line movement pulse L is generated every 50 mm, the number of bits of the shift register 16 is 20 bits, and each value of 20 bits (1 Or 0) is output in parallel to the analog adder 17. This analog adder 17 has a line moving pulse L
Every time is input, the signal of '1' in the shift register 16, that is, all the signals corresponding to the defect signals detected and output by the second defect level detection unit 12 are added, and the added voltage is calculated. The output is sent to the comparison unit 19. Therefore, the output voltage of the adder 17 becomes proportional to the number of detected small defects of the detection target O having a unit length.

The defect reference setting unit 18 is provided in the shift register 1
Defect determination level n
K, and sends this value to the other input of the comparison unit 19 as a reference level. The constant K is usually selected to be 0.5 to 0.8. This is because when the defect is small, it is not always detected as a low level defect signal. However, it goes without saying that this defect determination level can be arbitrarily set depending on the type of the object to be detected O.

The comparison unit 19 inputs the output of the adder 17 and the defect determination level of the defect reference setting unit 18 and compares them. If the output exceeds the defect determination level n · K, it is determined as a defect and the buffer amplifier 20 is activated. Output through.

As described above, since the shift register is used to shift the contents as the object to be detected is moved, the added value of each bit output, that is, the defect can always be judged by the unit length, and a small defect can be overlooked. Will not occur.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the present invention.

[0014]

As described above, according to the present invention, since the unit length is set for the object to be detected and the judgment is made based on the frequency of occurrence of defects, even small defects can be detected without overlooking, and accuracy can be improved. High defect detection becomes possible, and when used in an inspection line, for example, there is an advantage that the yield of defect detection is significantly improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a defect determination device using thermography according to the present invention.

FIG. 2 is a diagram for explaining a signal waveform for defect detection.

FIG. 3 is a block diagram showing a configuration of a conventional example.

[Explanation of symbols]

 7 Temperature Change Detection Section 8, 12 First and Second Defect Level Detection Section 9, 13 Defect Level Setting Section 10, 14, 19 Comparison Section 15 Defect Judgment Section 16 Shift Register 17 Adder 18 Defect Reference Setting Section

Claims (1)

[Claims] 1. A scanning unit for scanning a traveling detection object in a direction orthogonal to the traveling direction thereof, an infrared detector for detecting infrared rays emitted from the detection object, and an output of the infrared detector. In a defect determination device by thermography having a temperature conversion unit for converting into a temperature signal and a defect determination unit for determining a defect of a predetermined value or more of the object to be detected, a temperature change detection unit for detecting a temperature change amount of the temperature signal, First defect level detecting means for detecting a first defect level from the output of the temperature change detecting means, and second defect level detecting means for detecting a second defect level from the output of the temperature change detecting means, According to the thermography, the image forming apparatus further comprises defect determining means for determining a defect of the object to be detected based on an output of the second defect level detecting means and a line moving pulse. Defect determination unit.