JP2801916B2 - Defect inspection equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defect inspection apparatus for inspecting minute defects of a substrate having a smooth surface or an industrial product having a synchronous pattern.

[Conventional technology]

For example, substrates with smooth surfaces such as photomask blanks, photographic plates, glass substrates, etc., and CCD color filters,
As methods for detecting defects of industrial products such as a mesh electrode for an image pickup tube, a method using dark field illumination, a method using an image pickup device, a method using a diffraction phenomenon, and the like are known.

The dark-field illumination method detects defects by optically enhancing defects with dark-field illumination.The method using an imaging device captures a sample image and automatically detects defects from this image. Is what you do. In addition, a method utilizing the diffraction phenomenon is a method in which a defect of a periodic pattern is enhanced and detected by using a spatial filter method or the like utilizing the diffraction phenomenon (for example, Japanese Patent Application Laid-Open No. 61-256241).

[Problems to be solved by the invention]

However, in the method using an image pickup apparatus, even when a defect is to be automatically detected with high inspection sensitivity, it is necessary to cause even a minute defect to appear in a video signal. for that reason,
Extremely strong illumination light is required. Further, in the case of inspection of a photosensitive substrate such as a photographic dry plate (emulsion substrate), it is necessary to use illumination light having a limited wavelength range (usually red to infrared) and intensity, and High brightness cannot be obtained, and defects cannot be detected. Furthermore, even under the condition that a predetermined detection sensitivity can be obtained, since the brightness ratio between the smallest defect to be detected and the large defect is large,
Under the condition that a small defect can be detected, the light amount at a large defect becomes excessive, causing a problem such as image sticking on the imaging surface. vice versa,
If seizure does not occur, there are disadvantages such as the inability to detect minute defects under such conditions.

In addition, the method using the diffraction phenomenon has a
The ratio to a large defect such as a large defect or the outer periphery of the periodic pattern portion is large, and there is a problem similar to the above-described example.
Furthermore, light having high parallelism is required for the illumination light, and a pinhole plate is used for the illumination optical system. For this reason, there is a restriction that sufficient intensity cannot be obtained for the emitted light. Therefore, when laser light is used for strong illumination, speckles and the like occur in an observation image due to the influence of reflected light from various parts of the optical system, and it is difficult to identify a minute defect.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems, and an object of the present invention is to provide a defect inspection apparatus that can detect a defect with stable sensitivity regardless of the size of the defect.

[Means for solving the problem]

For this purpose, the present invention provides a defect detection apparatus for detecting a defect based on a sample image in which a defect of an inspected sample having an optically smooth surface is emphasized, comprising a light source and a filter for cutting a specific wavelength range of the light source. Illuminating means for illuminating the sample obliquely through the filter, and a cooling type for capturing an optical image of the sample
A CCD camera, an optical system for forming an optical image in which a defect of the sample is emphasized by scattered light from the sample illuminated by the illumination means on the camera, a moving means for two-dimensionally moving the sample, and an image captured by the camera Image processing means for taking in the image data and the movement information thus obtained and detecting a defect of the sample.

[Action]

The defect inspection apparatus of the present invention includes a light source and a filter that cuts a specific wavelength range of the light source, an illuminating unit that illuminates the sample obliquely through the filter, and a cooled CCD camera that captures an optical image of the sample. An optical system for forming, on a camera, an optical image in which a defect of the sample is emphasized by scattered light from the sample obliquely illuminated by the illumination unit, a moving unit for two-dimensionally moving the sample, and image data captured by the camera And the image processing means to capture the movement information and detect the defect of the sample, so that the specularly reflected light does not enter the camera, and the camera captures an image due to scattered light from scratches on the sample surface or adhesion of foreign matter. And an image in which the defect is emphasized is obtained.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a view showing one embodiment of the present invention applied to defect inspection of a large photographic plate, wherein 1 is a reflecting mirror, 2 is a lamp,
Reference numeral 3 denotes a filter, 4 denotes a substrate to be inspected, 5 denotes a lens, 6 denotes a camera, 7 denotes an image processing unit, 8 denotes a control unit, and 9 denotes an XY moving mechanism.

In FIG. 1, a reflecting mirror 1 focuses the light emitted from a lamp 2 in the direction of a filter 3, and the filter 3
This is to cut off a specific wavelength range of the light source.
Out of the emitted light, for example, for a photosensitive substrate, the photosensitive wavelength is cut. The camera 6 cools the CCD image pickup device by an electronic cooling device to enable imaging by long-time exposure. The camera 6 is sequentially moved by the XY moving mechanism 9 and the optical image of the substrate 4 to be inspected by the lens 5 is several minutes. Captured in the remainder. The image processing unit 7 captures a video signal from the camera 5, performs A / D conversion, performs an arithmetic operation, and detects a portion having a different brightness from the surroundings as a defect.

As described above, the radiated light of the lamp 2 is collected by the reflecting mirror 1,
By irradiating the surface of the substrate 4 to be inspected through the filter 3, when the substrate 4 to be inspected is a photosensitive substrate, the photosensitive wavelength is cut so that the irradiation light is not exposed to light and the irradiation angle is reduced. The light is specularly reflected from the surface of the substrate 4 to be inspected so as not to enter the camera 6 as shown. Therefore, if there is a grease or foreign matter on the surface of the substrate 4 to be inspected, light is scattered at this portion, and a part of the scattered light enters the camera 6 through the lens 5 to form an image. Thus, the image can be processed by the image processing unit 7 and a defect can be detected by comparing with the surrounding brightness.

In this case, the brightness incident on the camera 6 through the lens 5 is completely different between the defect-free smooth surface and the defect portion.
The difference in brightness depending on the size of the defect is not so large as in the conventional case. Therefore, the defect can be detected with a stable detection sensitivity regardless of the size of the defect. In addition, even if the photosensitive wavelength is cut through the filter 3 and the intensity is lowered to such a degree that the irradiated light is not exposed, it is possible to use the cooled CCD camera 6 in which the CCD image pickup device is cooled by the electronic cooling device, and perform imaging by long-time exposure. Therefore, a high-sensitivity image can be captured by spending a sufficient exposure time.

〔The invention's effect〕

As is apparent from the above description, according to the present invention, defects are detected by the arithmetic processing of the image data captured by the scattered light when the sample to be inspected is illuminated obliquely. By repeating detection and movement, high-resolution imaging can be performed even when the detection area is large with respect to the number of pixels of the image sensor. In addition, since the photosensitive wavelength can be cut by a filter for photosensitive substrates, the sensitivity is high, and the dynamic range of video signals is large.
Even weak light due to minute defects can be detected without causing burning due to large defects.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of the present invention applied to defect inspection of a large photographic dry plate. 1 ... reflecting mirror, 2 ... lamp, 3 ... filter, 4 ...
Substrate to be inspected, 5: lens, 6: camera, 7: image processing unit, 8: control unit, 9: XY moving mechanism.

Claims (1)

(57) [Claims] 1. A defect detection apparatus for detecting a defect based on a sample image in which a defect of a sample to be inspected having an optically smooth surface is emphasized, comprising a light source and a filter for cutting a specific wavelength range of the light source. Illumination means for illuminating the sample obliquely through the filter, a cooled CCD camera for capturing an optical image of the sample, and an optical image in which defects in the sample are emphasized by scattered light from the sample illuminated obliquely by the illumination means A defect inspection system comprising: an optical system that forms an image on a camera; a moving unit that moves the sample two-dimensionally; and an image processing unit that detects image defects obtained by capturing image data and movement information captured by the camera. apparatus.