JPH06201608A - Method for inspecting surface - Google Patents

Abstract

PURPOSE:To realize a novel method for inspecting a surface which can effectively and easily detect an abnormal position of a surface to be inspected by removing influence of halation of an inspecting unit with an illumination light source. CONSTITUTION:A method for inspecting a surface at abnormal positions A, B, C of a part 0A to be inspected having the steps of illuminating the part 0A of a surface 0 to be inspected, reading an image of the illuminated part by a reader 20 to convert it into a signal, processing the signal with a threshold value to detect the abnormal positions A, B, C, comprises the steps of sequentially illuminating the unit from two or more different directions, reading the image of the illuminated part at each illuminating time, converting it into a signal with the threshold value, and calculating an AND operation of image data of each illumination processed with the threshold value to detect the abnormal positions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface inspection method.
INDUSTRIAL APPLICABILITY The present invention can be used for inspecting the body surface of an automobile.

[0002]

2. Description of the Related Art An inspection portion of a surface to be inspected, such as the surface of an automobile body, is illuminated, an image of the illuminated portion is read by a reading device and converted into a signal, and this signal is thresholded to detect an abnormal portion on the surface to be inspected. A method for detecting (a scratch or the like) is well known in the art.

For example, FIG. 2A schematically shows a case where the surface of the fender portion 0 of an automobile body is inspected as a surface to be inspected. The illumination light source 10 such as a halogen lamp is controlled to blink by the control unit 30 to illuminate the inspection unit 0A on the surface of the fender unit 0.

The CCD camera 20 as a reading device is controlled by the control unit 30 to read the portion of the inspection unit 0A illuminated by the illumination light source 10 on the surface of the fender unit 0, convert it into an image signal, and perform image processing by a computer or the like. It is output to the unit 40.

If "scratches" A, B, and C as shown in FIG. 2 (b) exist as abnormal parts in the inspection section 0A, for example, in the image read by the inspection section 0A, the scratches A, B, and C are detected. Areas are bright and areas without scratches are dark. The relationship between the lightness and darkness of the scratched portion and other portions in the read image differs depending on the positional relationship between the direction of the illumination light and the reading device. It is also possible to read as follows. Here, for the sake of concreteness of description, it is assumed that the scratched portion is bright and the non-scratched portion is dark as described above.

When "threshold processing" for binarizing the read image at an appropriate threshold level is performed, as shown in FIG. 2C, signals corresponding to abnormal points A, B and C in the inspection unit 0A are output. The parts a, b, c where the level becomes “H (high)” are obtained, whereby the abnormal parts A, B, C can be detected.

[0007] By the way, conventionally, such a surface inspection method has a problem that "abnormal portion detection failure due to halation". That is, when the surface to be inspected is a glossy surface such as the surface of an automobile body, when viewed from the reading device 20, for example, as shown in FIG.
When a portion indicated by reference numeral D in FIG. 2 causes halation due to the illumination light and the above-described image processing is performed in such a state, the portion D in which halation occurs is two-dimensionally changed as shown in FIG. The abnormal portion d having a spread is detected, and the scratch C, which is the actual abnormal portion, is not detected.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and is a novel surface inspection capable of reliably and easily detecting an abnormal point on a surface to be inspected by removing the influence of halation. The purpose is to provide a method.

[0009]

According to the surface inspection method of the present invention, "the inspection section on the surface to be inspected is illuminated, the image of the section to be illuminated is read by a reading device and converted into a signal, and this signal is thresholded. A method for detecting an abnormal portion in the inspection section "and is characterized by the following points. That is, “the inspection section is sequentially illuminated from two or more different directions, and the image of the illuminated section is read every time the illumination is performed, signalized to perform threshold processing, and the threshold-processed image data of each illumination is acquired. It calculates and detects the abnormal part. "

In order to sequentially illuminate the inspection part from two or more directions, for example, a single illumination light source is made displaceable, and this illumination light source is moved so that illumination is performed successively from different directions. Alternatively, a plurality of illumination light sources may be provided at predetermined positions and these may be sequentially blinked to illuminate the inspection unit from different directions.

Since the inspection unit is illuminated from at least two different directions, the minimum number of light sources required when using a plurality of illumination light sources is two. In this case, the arrangement of the two illumination light sources can be determined such that "the two illumination light sources are located so as to sandwich the reading device" (claim 2).

[0012]

As described above, in the present invention, the inspection portion of the surface to be inspected is illuminated from two or more different directions. Illumination from these different directions is temporally separated, and the position where halation occurs is different for each illumination.

[0013]

EXAMPLE FIG. 1 shows one example. To avoid complications, see Figure 2 for things that are not likely to be confused.
The same reference numerals were used as in. In FIG. 1 (a),
Reference numeral 12 indicates a second illumination light source. Second illumination light source 12
Are halogen lamps and the like like the first illumination light source 10, and are arranged on opposite sides via the CCD camera 20 which is a reading device.

For the sake of concreteness of the description, the positional relationship between each illumination light source and the CCD camera 20 is also "this is such that the scratched portion is bright and the non-scratched portion is dark" in the read image of the inspection portion. It shall be stipulated.

As shown in FIG.
It is assumed that the scratches A, B, and C as shown in (b) are present as abnormal parts. First, when only the illumination light source 10 is turned on to perform illumination, when viewed from the position of the CCD camera 20, FIG.
Halation occurs as indicated by reference numeral D1 in (c), and when this illumination state is read by the CCD camera 20 and binarized by threshold processing, the halation portion D1 becomes a signal level "H" together with the scratches A and B, As shown in FIG. 1E, the "H" portion becomes a, b, d1 and the abnormal portion C is not detected.

Next, when the illumination light source 12 is turned off and only the illumination light source 12 is turned on to illuminate the inspection unit 0A, C
The illumination state viewed from the CD camera 20 is as shown in FIG. 1D, and the halation portion D2 appears to overlap the scratch A. Therefore, when this state is read and binarized by threshold processing, the portions where the signal level becomes “H” according to the scratches B and C and the halation portion D2 are denoted by the symbols b, c, and d2 in FIG. 1 (f). It is detected as shown in.

Therefore, in the image processing device 40, the AND operation is performed on the image data ((e) and (f) in FIG. 1) obtained by the above two kinds of illumination states. That is, when the image data shown in (e) and (f) of FIG. 1 is AND-processed for each pixel, only the pixels whose signal level in the image data for each illumination is “H” become “H”. ,
As a result of the arithmetic processing, the portion having the signal level "H" is shown in FIG.
Like the parts a, b, and c shown in (g), the abnormal parts A, B, and C in the inspection part are correctly dealt with, and the influence of halation is removed to reliably detect the abnormal parts on the inspection surface. be able to.

[0018]

As described above, according to the present invention, a novel surface inspection method can be provided. Since the present invention is configured as described above, even when the surface to be inspected has gloss, the influence of halation can be removed to easily and surely detect the abnormal portion of the surface to be inspected. You can

[Brief description of drawings]

FIG. 1 is a diagram illustrating an embodiment of the present invention.

FIG. 2 is a diagram illustrating a conventional technique and its problems.

[Explanation of symbols]

 0 Surface to be inspected 0A Inspection part 10, 12 Illumination light source A, B, C Damage (abnormal part in inspection part) D1, D2 Halation part

Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI Technical display location G06F 15/64 400 J 7631-5L H04N 7/18 B

Claims (2)

[Claims] 1. A method for detecting an abnormal part in an inspection part by illuminating an inspection part on a surface to be inspected, reading an image of the illuminated part by a reading device to convert it into a signal, and subjecting this signal to threshold processing. Parts are sequentially illuminated from two or more different directions, the image of the illuminated part is read every time it is illuminated, signalized to perform threshold processing, and the thresholded image data for each illumination is ANDed and abnormal A surface inspection method characterized by detecting points. 2. The surface inspection method according to claim 1, wherein two illumination light sources for illuminating the inspection portion of the surface to be inspected are provided so as to sandwich the reading device, and these two illumination light sources are sequentially blinked to perform inspection. A surface inspection method, which comprises sequentially illuminating a part from different directions.