JPH04188052A - Surface inspecting apparatus - Google Patents

Abstract

PURPOSE:To keep the level of reflected light from a roll surface at a sufficiently low state and to extract the effective component of the output of scanning accurately by selecting the color of the roll and the like in contact with a band-shaped material as a complementary color with respect to the color of an illuminating light source for scanning. CONSTITUTION:When a red light source such as He-Ne laser is used as an illuminating light source for scanning, the color of the surface of a roll is selected as a blue or green color. In an output (a) of a photodetector 4, the levels of scanning parts A and C of the roll 2 are sufficiently low in comparison with the level of a scanning part B of a band-shaped material 1. Then, an adequate threshold value (b) from a setting device 6 is compared with the output (a) of the received light in a comparator 7, and the level is discriminated. As a result, the accurate gate signal (c) is obtained. When a gate 8 is controlled with the signal (c), a signal (d) of the scanning part B of the band-shaped material 1 can be extracted. Thus, the effective part and the noneffective part of the output of the received light can be accurately divided.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention is directed to photoelectronizing the surface of a strip running in contact with a roll or the like in the width direction at a position in contact with the roll or the like. The present invention relates to a surface inspection device that detects defects by scanning the surface of the surface.

(Prior Art) A typical conventional configuration of this type of surface inspection device is shown in FIG. A long strip 1, which is an object to be inspected, is a roll 2.
Driving in contact with Since the strip 1 does not vibrate or bend at the position in contact with the roll 2, photoelectric scanning is performed at this position. That is, the surface of the strip 1 in contact with the roll 2 is illuminated by the light source 3, and the reflected light is received by the light receiver 4 to scan the strip 1 in the width direction. There are various scanning methods such as flying spot, flying image, and -dimensional camera.

Since the photoelectric scanning is performed over an area slightly longer than the width of the strip 1, the surface of the roll 2 is also scanned. roll 2
If there is reflected light from the surface of the strip 1 that is equivalent to that from the strip 1, the processing system for the received light signal cannot distinguish whether the inspection signal is from the surface of the roll 2 or the surface of the strip 1.

Therefore, in order to sufficiently reduce the intensity of the reflected light from the roll 2 that enters the light receiver 4, a light shielding device 5 is provided.
The illumination light from the light source 3 is prevented from hitting the part of the roll 2 that is not covered by the light source 3. That is, the light blocking device 5 is provided so that the exposed portions of the roll 2 on both sides of the strip 1 are shaded. In this way, the level of light reflected from the roll 2 becomes sufficiently low and can be reliably distinguished from the level of light reflected from the strip 1.

(Problems to be Solved by the Invention) In the conventional technology described above, if the strip 1 running in contact with the roll 2 does not change at all in the width direction,
The purpose can be achieved with a simple light shielding device 5. However, the strip 1 often fluctuates in the width direction as it travels, and it is practically difficult to keep the surface of the strip 1 free of shadows without exposing the exposed surface of the roll 2 to illumination light. Met.

This invention was made in view of the above-mentioned conventional problems, and its purpose is to use a surface inspection device that scans a strip in the width direction at a position in contact with a roll, etc., in which the strip moves in the width direction. Another objective is to keep the level of light reflected from the surface of the roll etc. sufficiently small compared to the level of light reflected from the surface of the strip.

[Structure of the Invention] (Means for Solving the Problems) Therefore, in the present invention, the color of the surface of the roll etc. is selected so as to be complementary to the color of the illumination light source for scanning.

(Function) The rolls, etc. are exposed on both sides of the strip-shaped object to be inspected,
Illumination light for scanning also hits there, and the reflected light from there also enters the receiver and is scanned, but the color of the surface of the roll etc. is complementary to the color of the illumination light. Therefore, the level of reflected light from the surface of the roll etc. becomes sufficiently small.

(Example) When a red light source such as a He-Ne laser is used as the illumination light source for scanning, the color of the surface of the roll etc. is selected to be blue or green.

Furthermore, it is more preferable to provide a polarizing filter in the light receiver for scanning to attenuate reflected light from the surface of the roll or the like.

In the output of the light receiver for scanning, if the level of light reflected from the surface of the roll, etc. is kept sufficiently small compared to the level of light reflected from the surface of the strip-shaped object to be inspected, the received light output will be effective. It is possible to easily and accurately distinguish between a portion (inspection signal of the strip) and an invalid portion (portion protruding from the strip).

Below, signal processing for this purpose will be explained.

In FIG. 1, 1 is a strip, 2 is a roll, 3 is an illumination light source, and 4 is a light receiver. As mentioned above, the color of the surface of roll 2 is complementary to the color of illumination light source 3. . Therefore, at the output a of the light receiver 4, the level of the scanning portions A and C of the roll 2 is sufficiently lower than the level of the scanning portion B of the strip 1.

Therefore, by comparing the appropriate threshold value from the setter 6 and the received light output a with the comparator 7 for level discrimination, an accurate gate signal C can be obtained as shown in the figure, and this signal C can be used to control the gate 8. If controlled, the signal d of the scanned portion B of the strip 1 can be extracted.

Another example of signal processing is shown in FIGS. 2 and 3. Here, the output a of the photodetector 4 is differentiated by a differentiating circuit 9, and the differential output e is sent to the comparators 10a and 10 to obtain the positive and negative threshold values +Vs from the setter 11.

-Discriminate the level by comparing with Vs.

The positive differential pulse f output from the comparator 10a includes the edge signal E1 of one edge of the strip 1, and the negative differential pulse g output from the comparator 10b includes the edge signal E2 of the other edge of the strip 1.

On the other hand, a scanning start signal is obtained by the sensor 12, and a signal synchronized with the running of the strip 1 is sent to the pulse generator 1.
Obtained from 3. The output of the pulse generator 13 is frequency-divided by a frequency divider 14, and is divided into a signal at a minute constant pitch of 1,
A signal is generated every time the vehicle travels a certain amount of distance. The memory controller 15 operates in response to the output of the frequency divider 14 and the scan start signal, and after being reset by the scan start signal, is counted up with a signal every fixed pitch l.

The memory 16a (16b) has an adder at its input stage, and the memory controller 15
Read the address of and generate a positive differential pulse (
If there is a negative differential pulse, add 1° and store it.

In other words, it works as a multi-addition type that adds address by address.

The timing of addition and storage in the memory 16a (16b) is at every constant pitch l obtained by dividing the signal from the pulse generator 13, which generates pulses in synchronization with the amount of progress each time the line advances, by the frequency divider 14. It takes the form of sampling and memorizing. In other words, the contents stored in the memory 16a (16b) are divided from the scanning start point in the width direction of the strip by memory address unit W, and in the direction of movement of the strip at every pitch l, the comparator 10a ( 1
This means that the number of output pulses of 0b) was extracted and the oblique shadow was obtained in the flow direction. Here, when the flow direction progress amount L (1<L) has elapsed, the comparator 1 is stored in the memory 16a (16b).
The pulse output of 0a (10b) is divided finely in each width direction, and the count value for each width position is stored. When the value reaches a certain value, the contents of the memory 16a (16b) are sequentially read out according to the addresses on the address bus, and the contents are passed to the positive and negative independent profile comparators 17a (16b).
7b) is compared with the set value of the setter 18a (18b), and the address exceeding the set value is sent to the latch circuit 19a (19
b) latches. At this time, the positive polarity latch 19a
is latched every time the set value is exceeded, but latching is prohibited after an address that exceeds the set value of negative polarity. The integrated profile shows that differential pulses are generated continuously at the edge of the strip, but if the roll 2 is dirty or has scratches, it becomes difficult to generate continuous differential pulses (in the case of a roll, it rotates, so intermittent defects occur). ), the integrated value is lower than the edge, so it can be reliably separated. The latched positive polarity address and negative polarity address are not advanced until the next travel distance signal, and the address synchronized with the scan start signal and the latched address are compared independently (positive/negative) by the comparator 10a (20b). By applying the positive address matching point as a set signal and the negative address matching point as a reset signal to the gate flip-flop 21 at the matching points, the output of the flip-flop 21 becomes the correct gate signal C.

If the profile integrated values of the edge of the strip and roll 2 are similar and the above conditions cannot be satisfied, the address bus is divided into two lines, one for positive polarity and one for negative polarity, and the readout is performed using a signal for each traveling distance. When the address counter is switched by the bus switching gate, positive polarity data is read out by counting down from 1/2 of the memory write range, negative polarity data is read out by counting up from 1/2, and the initial comparison setting value is read out. The exceeded address may be latched and obtained, and then the flip-flop 21 may be reset to set 1 in the same manner as described above, and the gate signal C may be output.

[Effects of the Invention] As explained in detail above, in this invention, the color of the roll, etc. that the strip-shaped object (object to be inspected) comes into contact with is selected in a complementary color relationship to the color of the illumination light source for scanning. Therefore, even if the strip moves in the width direction on the roll etc. as it travels, the level of light reflected from the surface of the strip will be lower than the level of reflected light from the surface of the strip, etc. The light level is always kept sufficiently low that only the useful portion of the scanning output can be accurately extracted with simple circuit processing.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration and waveforms of an example of a signal processing system in a device employing the present invention, FIG. 2 is a block diagram showing another example of the signal processing system, and FIG. 3 is the operation of FIG. 2. The waveform diagram and FIG. 4 are configuration diagrams of a conventional device.

Claims (1)

[Claims] (1) In a device that inspects defects by photoelectrically scanning the surface of a strip running in contact with a roll, etc. in the width direction at a position in contact with the roll, etc., the color of the illumination light source for scanning. A surface inspection device characterized in that the color of the surface of the roll or the like is a complementary color.