JPH04364446A - Defect inspecting apparatus - Google Patents

Abstract

PURPOSE:To detect the defects such as stripe-shaped defects, irregularities and flaws on a surface positively and accurately by picking up the image of a material under inspection with an image sensing device having general-purpose applications. CONSTITUTION:A defect inspecting apparatus is formed of an image sensing device 12 for picking up the image of a material under inspection, a processing device 20 for converting the data from the image sensing device 12 into the digital data and inspecting the good/bad states due to the defects such as stripe- shaped defects, irregularities and flaws on the surface of the material under inspection through a CPU 23 and an output part 30. The processing device 20 corrects the concentration gradient of lighting and compares the difference between the maximum value and the minimum value of the corrected concentration profile.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for inspecting defects such as irregularities and scratches on the surface of tapes, films, etc.

0002

2. Description of the Related Art Conventionally, a device for detecting defects existing on a surface has been used, for example, as shown in Japanese Patent Laid-Open No. 55-70732, which irradiates the surface of an object to be inspected with a He-Ne laser beam. There is a method for inspecting the surface condition based on the degree to which light is scattered in arbitrary directions due to unevenness.

0003

[Problems to be Solved by the Invention] However, the above-mentioned conventional surface condition inspection apparatus using the light irradiation-scattering method has the following problems:
There are the following problems.

(2) The optical system is complicated and the device becomes large. ■Poor detection ability for streak-like defects flowing in the line direction. ■Detection results do not necessarily match the sense perceived by the human eye.

(2) When inspecting wide tapes, films, etc., the detection ability at both ends is low. ■If the sensitivity is set high, even non-defects may be detected, such as foreign substances due to pulp on the tape surface.

[0006] The defect inspection/identification apparatus of the present invention aims to reliably inspect the state of defects in a state similar to that seen by the human eye, using a compact device configuration.

[0007]

[Means for Solving the Problems] The defect inspection apparatus of the present invention includes an illumination device that illuminates the surface of an object to be inspected, an imaging device that images the surface of the object to be inspected, and a defect inspection device that This is a surface defect inspection device that includes a processing device that inspects the surface condition of an object to be inspected and an output section that outputs the inspection results of the processing device. The reflected light is imaged from the top surface of the object to be inspected.
The processing device corrects the density gradient due to illumination from the average density at each end of the image, determines the maximum value and minimum value from the corrected density profile, and compares the difference between the maximum value and minimum value with a predetermined threshold value. This defect inspection device is characterized by detecting defects by detecting defects.

[0008]

[Function] According to the present invention, the following effects (1) to (4) are achieved. ■
The surface condition can be inspected using a versatile imaging device such as a television camera, and the device configuration can be made compact.

[0009] Surface defects can be reliably detected with a sense close to that of humans. ■The defect inspection device of this invention corrects the density gradient due to illumination from the average density of each end of the image captured by the imaging device, calculates the maximum value and minimum value from the corrected density profile, and calculates the difference between the maximum value and the minimum value. Defects are detected by comparing with a predetermined threshold value.

0010

[Example] Fig. 1 is a block diagram showing an example of a defect inspection/identification device of the present invention, Fig. 2 is a flow chart showing an inspection procedure of the device of the present invention, and Fig. 3 explains a concentration gradient correction method. 4 are schematic diagrams of density profiles before and after density gradient correction, and FIG. 5 is a diagram showing an example of inspection according to the present invention.

The defect inspection device includes an imaging device 12 and a lighting device 1.
1, a processing device 20, and an output section 30.
Inspect and identify 0 defects. The basic operations of the defect inspection apparatus are as follows: 1) The object to be inspected 10 is illuminated with the illumination 11 from diagonally above, and the reflected light is imaged by the imaging device 12.

The imaging device 12 transfers a multivalued image sampled pixel by pixel to the inspection device 20. 2) The inspection device 20 converts the photographic data of the imaging device 12 into an A/D
The converter 21 quantizes, for example, 8 bits (256 gradations) to create a digital image of M*N pixels, which is input to the image memory 22.

3) The inspection device 20 uses the CPU 23 to inspect the surface for defects based on the image input to the image memory 22. 4) The output device 30 displays the inspection results of the inspection device 20 and generates an alarm if necessary.

[0014] As the imaging device 12, a television camera or a line sensor having a spatial resolution of M can be used. When a line sensor is used, the line sensor and the object to be inspected are moved relative to each other, and the resulting N groups of data are stored in the image memory 22.

The inspection device 20 does not necessarily have the image memory 22.
The output data of the A/D converter 21 is sent directly to the CPU without using
23 may be entered. The flow up to abnormality determination according to the present invention will be explained with reference to FIG.

1) Average density μL at both left and right ends of the image
, find μR. That is, if the density of coordinates (i, j) is f(i, j),

0
017]

[Math 1]

[0018]

[Math 2]

[0019] 2) From these density average values, the density gradient due to illumination is corrected according to the following equation. The illumination is projected from the left side of the screen to the right side, and if the quantization is 8 bits and the density after correction is g (i, j),

002
0]

[Math 3]

[0021] However, a=(μR-μL)/255+μ
Lb: Any 3) The maximum value M from the density profile in the corrected direction
4) Find the minimum value MNj of
≦T: Determine that there is no defect (J=1, 2, . . . , N) and output the result.

[0022]

As described above, according to the present invention, defects in an object to be inspected can be reliably inspected and defects can be classified using a compact device configuration.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention.

FIG. 2 is a flow diagram showing the flow of abnormality determination according to the present invention.

FIG. 3 is a diagram illustrating a concentration gradient correction method.

FIG. 4 is a schematic diagram of density profiles before and after density gradient correction.

FIG. 5 is an example of test results according to the present invention.

[Explanation of symbols]

10 Object to be inspected 11　　　　　　　　Lighting device 12 Imaging device 20 Processing equipment 21 A/D converter 22 Image memory 23 CPU 30 Output section

Claims (1)

[Claims] 1. An illumination device that illuminates the surface of an object to be inspected, an imaging device that images the surface of the object to be inspected, and a processing device that inspects the surface state of the object to be inspected based on the imaging result of the imaging device. This is a surface defect inspection device comprising an output unit that outputs the inspection results of the processing device, and the device projects light from the upper surface of the object to be inspected in an oblique horizontal direction, and images the reflected light from the upper surface of the object to be inspected. Then, the processing device corrects the density gradient due to illumination from the average density at each end of the image, calculates the maximum value and minimum value from the corrected density profile, and calculates the difference between the maximum value and minimum value and a predetermined threshold value. A defect inspection device that detects defects by comparison.