KR100226904B1 - Detecting apparatus and method of surface fault of steel plate using laser - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for non-contact flaw detection of a cold rolled steel sheet using a laser. The surface roughness of the cold rolled steel sheet is set to a critical level and superimposed on a defect signal, thereby providing The purpose is to exclude the influence of surface roughness, to increase the flaw detection effect of the defect, and to easily determine the type of steel sheet defects by distinguishing the shape of the defect signal.

In order to achieve the above object, the present invention, the light beam scanned by the laser is incident to the photodetector to split into two branches, the other light beam is reflected on the specimen and incident on the photodetector to detect the surface roughness The light beam is reflected by the light shingles to be incident on the surface defect specimen of the translator, and the light beam reflected from the surface defect specimen is incident on the photodetector to detect the surface defect.

Description

Surface flaw detection method and apparatus for cold rolled steel sheet using laser

1 is a block diagram of a surface flaw detection apparatus for a cold rolled steel sheet using a laser according to the present invention

2 is a graph showing the setting of the noise level due to the surface roughness using the present invention.

3a-3f are graphs of a steel sheet surface flaw inspection example according to the present invention;

Explanation of symbols for main parts of the drawings

1: Laser 2,3: Light Garga

4,10,13,15: Lens 6,12,18: Photodetector

7: computer 8: psalms

9: Transducer 14: Spatial Filter

16: neutral filter

The present invention relates to a method and apparatus for non-contact flaw detection of a cold-rolled steel sheet surface using a laser. In particular, the intensity distribution of each reflected light after the laser beam is separated into two and scanned on the surface of the steel sheet The present invention relates to a method for detecting a surface flaw of a cold rolled steel sheet using a laser that can enhance the flaw detection effect by constructing an optical system that removes errors caused by the influence of surface roughness of the steel sheet.

In general, the cold rolled steel sheet is widely used as an exterior material for automobiles and electronics, so the quality of the surface is very important and fine surface flaws are not allowed.

However, the cold rolled steel sheet has various forms such as scratches, roll marks, slivers, and the like due to rolling during the manufacturing process for producing the same, and are affected by the influence of the surrounding environment. Rust is generated and various surface defects are occurring.

Therefore, in order to prevent the production of defective products of the cold rolled steel sheet and cope with the consumer's demand for quality assurance, surface flaw flaw detection technology of the steel sheet is required.

As a conventional method for measuring surface defects of a steel sheet using a conventional laser associated with such a technique, US Patent Nos. 4,298,808, Japanese Patent Application Laid-Open No. 61-25042, Japanese Patent Application Laid-open No. 61-45914, and the like are known.

According to the above publications, the surface of the cold rolled steel sheet is scanned by using a laser to measure surface defects, and since the inherent surface roughness of the steel sheet surface is not taken into consideration, the detection efficiency is very small for minute surface defects. Therefore, there was a problem that a measurement error occurs due to the surface roughness of the steel sheet.

The present invention is to improve the various problems as described above, the object is, by setting the size of the surface roughness of the cold-rolled steel sheet to the threshold level and superimposed on the defect signal, the effect of the surface roughness of the steel sheet The present invention provides a method for detecting a surface defect of a cold rolled steel sheet using a laser, which can eliminate the defects, increase the flaw detection effect, and distinguish the types of defect signals to easily identify the types of steel sheet defects.

Another object of the present invention is to provide an apparatus for detecting surface defects of a cold rolled steel sheet using a laser that can easily measure surface roughness and surface defects through a photo detector by scanning a laser through a light filter on a specimen on a translator. It is.

As a technical means for achieving the above object, the present invention, the light beam is scanned by the laser is incident on the light splitter and divided into two, and one light beam is incident on the photodetector through the lens and the bandpass filter The other light beam is reflected on the specimen to be incident on the photodetector through the lens and the band pass filter to detect surface roughness, and the light beam is reflected through the light beam to form parallel light beams by the two lenses. The parallel light beam is formed through a spatial filter to form a circular cross-sectional area of the light beam, and then incident on the surface defect specimen of the translator, and the light beam reflected from the surface defect specimen is passed through the neutral filter and the bandpass filter to the photodetector. Surface flaw detection room of a cold rolled steel sheet using a laser comprising incident and detecting surface defects It depends on the maryeonham.

In addition, the light is installed in front of the laser so that the light source is split into the specimen and the light beam on the upper side of the laser positioned inclined at a predetermined angle, and the lens and band pass filter in front of the light beam on the upper side And a light detector through which the incident light source is transmitted to detect the incident light source, and a light detector in front of the lens and the band pass filter through which the light source reflected from the specimen is transmitted, thereby providing a surface that is integrally input with the photodetector. A spatial filter having a circular cross-sectional area of a beam formed between the computer for measuring roughness and two lenses in which the light source reflected by the upper light beam is formed as parallel light, and installed to enter the specimen; Neutral filter and bandpass filter are installed through which the light source reflected from the specimen is transmitted. By providing a surface flaw detection apparatus for a cold rolled steel sheet using a laser including a computer that shows a surface flaw detection signal as the intensity of a light source incident on the photodetector above.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of a surface flaw detection device for a cold rolled steel sheet using a laser according to the present invention, wherein a laser beam 1 is positioned at an angle to one side of the surface flaw detection device and positioned above the translator 9 ( 8) and the light shimmer 2 installed in front of the laser 1 to split the light source into the light shimmer 3 on the upper side, and the lens 4 in front of the light shimmer 3 on the upper side. And a band pass filter 5 is installed so that an incident light source is transmitted therethrough, and in front of the band pass filter 5 an optical detector 6 for detecting an incident light source is located, which is reflected from the specimen 8. A photo detector 12 is provided in front of the lens 10 through which the light source is transmitted and the band pass filter 11 so that the computer 7 is inputted integrally with the photo detector 6 so that the surface roughness of the steel sheet as a signal is obtained. To be measured.

In addition, a cross-sectional area of light is circularly formed between the two lenses 13 and 15 provided so that the light source reflected by the upper light shimmer 3 is formed in parallel light so that the spatial filter is incident on the specimen 8. (15) is installed, the neutral filter 16 and the bandpass filter 17 through which the light source reflected from the specimen 8 through the spatial filter 15 is transmitted is installed to the photo detector 18 in front of it. The intensity of the incident light source is transmitted to the computer 7 to represent the surface flaw detection signal of the steel sheet.

Referring to the embodiment of the present invention having such a configuration as follows.

The light rays generated by the laser (1) of the surface flaw detection device are incident on the light splitter (2) and split into two, and one of them is reflected and passes through the lens (4) and the bandpass filter (5). It is input to the computer 7 after it has entered the (6).

In addition, the other light beam passing through the light filter 2 is reflected by the specimen 8 and is incident on the photo detector 12 through the lens 10 and the bandpass filter 11 and then enters the computer 7. As such, the intensity of light incident on the photo detectors 7 and 12 is used to calculate the surface roughness after being input to the computer 7.

In addition, the rays used to detect the surface defects are reflected by the light filter 3, and then parallel rays are formed through the two lenses 13 and 15, and then pass through the spatial filter 14 After the cross sectional area becomes circular, it is incident on the specimen 8 for surface defect measurement provided on the translator 9.

After the incident light is reflected on the surface of the surface defect measurement specimen 8 and then the amount of light is adjusted in the neutral filter 6 according to the sensitivity of the photodetector, the band is prevented from entering light other than the laser wavelength. The defect signal is measured by entering the photodetector 18 through the pass filter 17, which is input to the computer 7 to represent the defect signal.

2 is a graph showing the setting of the noise level by the surface roughness using the present invention, which represents the correlation between the length of the laser beam scanned on the surface of the steel sheet and the intensity of the reflected light.

In the graph, the noise level is set to include the maximum and minimum values of the surface irregularities centered on the average value of the irregularities, and the level can be arbitrarily adjusted as necessary.

3 is an embodiment of the surface flaw detection of the cold rolled steel sheet using a laser according to the present invention.

In FIG. 3A, a graph in the range of the noise level as a roll mark indicates unevenness due to surface roughness, and a portion protruding upward above the noise level indicates a defect signal due to the roll mark.

(B) of FIG. 3 shows Rust, the graph below the noise level is a defect signal due to rust, and (c) of FIG. 3 shows Point Rust, which is within the range of noise level. The graph shows unevenness due to surface roughness, and the portion protruding below the noise level indicates a defect signal due to rust.

3 (d) shows a defect signal due to scratches, and the defect signal is sawtooth slightly above or sharper than the noise level.

(E) of FIG. 3 is a line scab, and a sharp, deep defect signal appears at the bottom of the noise level. In FIG. 3, the graph of the noise level below the noise level is shown on the sliver. Due to surface defects.

As described above, by setting the size of the surface roughness to the threshold level in the present invention and superimposed on the defect signal, the effect of surface roughness can be eliminated and the flaw detection effect can be increased, and the shape of the defect signal can be distinguished. This makes it possible to easily determine the type of defect.

As described above, according to the present invention, it is possible to easily measure the surface roughness and surface defects through the photodetector by scanning the laser through the light shroud on the specimen on the translator, and the critical level of the surface roughness of the cold rolled steel sheet By superimposing the defect signal and setting it as, it is possible to eliminate the influence of the surface roughness of the steel plate, to increase the flaw detection effect of the combined steel, and to easily distinguish the types of the steel plate defects by classifying the shape of the defect signal. There is an excellent effect that can be done.

Claims (4)

The laser lighter 2 is installed at an angle to the laser beam 1 so that the light source is split into the specimen 8 positioned above the translator 9 and the light lighter 3 on the upper side. And a light detector 6 having a lens 4 and a band pass filter 5 installed in front of the light shingler 3 on the upper side to allow incident light to pass therethrough and detect incident light. Computer 7 for measuring the surface roughness as a signal input integrally with the photodetector is installed in front of the lens 10 and the bandpass filter 11 through which the light source reflected by 8) is transmitted. And a spatial filter formed in a circular cross-sectional area of the light beam between the two lenses 13 and 15 provided so that the light source reflected by the upper light shader 3 is formed as parallel light. 14 and a light source reflected from the specimen 8 through the spatial filter 14 The neutral filter 16 and the bandpass filter 17 which are transmitted are provided, and the computer 7 which shows the surface defect detection signal as the intensity of the light source incident on the photodetector 18 above is comprised, It is characterized by the above-mentioned. Surface flaw detection device for cold rolled steel sheet using laser. The apparatus of claim 1, wherein the neutral filter (16) adjusts the amount of light according to the sensitivity of the photo detector (18). The light beam emitted from the laser is incident on the light splitter and split into two branches. A reflected light beam is incident on the photodetector through the lens and the bandpass filter, and the other light is reflected on the specimen to reflect the lens and the bandpass filter. And detecting the surface roughness incident on the photodetector, and the light rays to be scanned are reflected through the light filter to form parallel rays by the two lenses, and the parallel rays pass through a spatial filter to determine the cross-sectional area of the rays. And forming a circular shape so as to be incident on the surface defect specimen of the translator, and the light reflected from the surface defect specimen is incident on the photodetector through the neutral filter and the band pass filter to detect the surface defect. Surface flaw detection method of the cold rolled steel sheet using the laser. The method according to claim 3, wherein the light beam scanned by the laser is incident on the light splitter and divided into two parts. The threshold level due to the surface roughness of the steel sheet is set to remove an error factor due to the surface roughness. Surface flaw detection method of a cold rolled steel sheet using a laser, characterized in that the flaw detection.