JP2827756B2 - Defect inspection equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defect inspection apparatus for judging the presence or absence of a defect on a surface to be inspected by using an image processing technique.

[0002]

2. Description of the Related Art FIG. 3 is a diagram showing a configuration of a defect inspection apparatus described in, for example, Japanese Utility Model Laid-Open No. 3-34155.
In the figure, 1 is a signal source (camera), 2 is an A / D converter for converting an image signal from the signal source 1 into a digital signal, 3 is an image memory for storing image values converted into a digital signal, and 4 is an image memory. A data processing device for determining the presence or absence of a defect on the surface portion of the inspection target based on the image value;
Denotes a test object, and 7 denotes a transport device that transports the test object 6.

[0003] The next operation will be described with reference to the flowchart of FIG. First, the surface of the inspection target 6 is illuminated by the illumination device 5, the surface of the inspection target 6 is scanned by the signal source 1, and an image signal is input (S1). The input image signal is converted into a digital signal by the A / D converter 2 (S2), and converted into an image value for each pixel in the image memory 3.
(S3). The image value for each pixel stored in the image memory 3 is subjected to a difference calculation (differential processing) of the image value between adjacent pixels by the data processing device 4 (S).
4). Finally, the difference calculation result is compared with a predetermined reference value (S5). If the difference calculation result is larger than the reference value, it is determined that the defective part has a defect in the surface portion corresponding to the pixel (S6). ). When the result of the difference calculation for all the pixels is equal to or less than the reference value, it is determined that there is no defect in the non-defective product (S
7). Note that the reference value is a value that can detect only a defect to be detected, and is determined by inputting an image of a sample to be inspected having such a defect.

[0004]

Since the conventional defect inspection apparatus is configured as described above, if there is a point (edge) that changes at an acute angle on the surface to be inspected, the point is generally removed. Is extremely large compared with the surrounding area, and the difference calculation result between adjacent pixels becomes large accordingly. Therefore, there is a problem that a non-defective edge portion is determined as a defect. Conversely, if the reference value is increased in consideration of the edge, the defect may not be detected.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and does not detect a sharply changing point (edge) on the surface of an inspection object as a defect, but can detect only a defect. The purpose is to obtain.

[0006]

SUMMARY OF THE INVENTION The defect inspection apparatus according to this inventions is the point which changes sharply on the surface (edge)
Exists, and when inspecting an inspection object whose edges are distributed symmetrically with respect to a reference line set on the surface, scan in a direction perpendicular to the reference line and input a grayscale image signal. Then, of the parts where the density is maximum, parts distributed at positions symmetrical with respect to the reference line are excluded, and a defect is determined between those parts as an inspection range.

[0007]

[Action] If you enter the image values to be inspected in the defect inspection apparatus according to this inventions, among the portion where the density is maximized, between them portions excluding the portions distributed symmetrically with respect to the reference line Is determined as the inspection range, so that only a true defective portion can be detected.

[0008]

[Embodiment 1 ] Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart illustrating a process of inspecting an inspection target having an edge, and FIG. 2 is a diagram illustrating a change in image data to be processed. As shown in Fig. 2, a cylindrical inspection with a cut surface
It is assumed that the inspection target 6 is inspected by the present apparatus. Cut surface
Although the edge is present on the surface because of the edge existing in the test object in this embodiment is as shown in FIG. 2 (b),
Objects distributed at symmetrical positions with respect to the reference line
I do.

[0009] The camera 1, as shown in FIG. 2 (a) (b), and inputs the image signal to scan the surface of the test object to the reference line at right angles with the direction (X) (U1). The input image signal is converted into a digital signal by the A / D converter 2 (U2) and stored in the image memory 3 as image data (U3). With respect to the stored image data, two pixels (pixels) having a maximum density value are searched for each line scanned by the camera, and these pixels are specified as points at which the surface shape changes at an acute angle, and the center of the pixels is determined. Are calculated and tied to obtain a reference line for image symmetry (U4).

[0010] subjected to differential processing in the range between by excluding the image of the two blocks existing <br/> symmetrically with respect to a more calculated reference line to the processing both images (U5), the differential value and the reference The pixel value is compared with the value (U6), and if there is a pixel having a larger differential value, it is determined to be defective (U7). If the differential values are smaller for all the pixels, the pixels are determined to be good (U8).

[0011] FIG. 2 (c) ~ (f) shows the image data obtained by the above process. That is, when it FIG. 2 (c) is an image signal input by the camera, there is part of a larger local maximum value corresponding to the edge portion to the position of the reference line and symmetrical, which is directly differential processing, FIG. 2 ( Since the output waveform shown in d) is obtained and the change amount of the edge of the cut surface is higher than the change amount (differential value) of the defect portion, the edge portion of the cut surface is extracted as a defect instead of a true defect. Will be done.

[0012] On the other hand Oite to an embodiment of the invention,
Since the differential process as part of the inspection range therebetween by excluding part of the maxima distributed in symmetry in FIG. 2 (e), as shown in FIG. 2 (f), truly part of the defect only Is extracted.

Embodiment 2 FIG . In the above embodiment, the width of the cut surface is set in the longitudinal direction of the inspection object.
It was different, but the width of the cut surface was inspected
Even if it is constant in the longitudinal direction of the
It is possible to expect the same effect as the above-described embodiment.
it can.

[0014]

As is evident from the foregoing description, since appears as a very <br/> Daine the image value of the edge portion according to the present invention are distributed in symmetrical positions with respect to the reference line, excludes these maxima portion Since the inspection range is set between the two, the defect can be accurately determined without erroneously determining the edge as a defect.

[Brief description of the drawings]

By [1] Example 1 of the present invention, with Edges
It is a flowchart which shows the process which inspects an inspection object .

FIG. 2 illustrates a change in image data due to the processing shown in FIG .
FIG.

FIG. 3 is a diagram showing a configuration of a conventional defect inspection apparatus.

FIG. 4 is a flowchart showing an inspection process by a conventional defect inspection apparatus .

[Explanation of symbols]

1 signal source (camera), 2 A / D conversion device, 3 image memory, 4 data processing device, 5 light source, 6 inspection object, 7 transport device.

Claims (1)

(57) [Claims] An image to be inspected is input as a grayscale image signal.
Means for storing the image value of each pixel, and
Means for calculating the amount of change from surrounding image values by
The issued change is larger than a predetermined reference value.
The surface of the inspection target corresponding to that pixel has a defect.
In a defect inspection device that determines that
There are changing points (edges)
Is symmetrical with respect to the reference line set on the surface
When inspecting distributed inspection objects, the inspection line
Scan in the direction of the corner and input a grayscale image signal, and the density is
Of the maximal part, divide it at a position symmetrical to the reference line.
Excluding the parts to be clothed and the area between them as the inspection range
A defect inspection apparatus characterized by determining a defect.