JPS6129453B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical defect detection device for identifying defects on the front and back surfaces of a transparent body.

BACKGROUND ART Techniques for detecting surface defects in opaque bodies such as steel plates by light scattering, reflection, etc. are known. However, even if glass, acrylic resin, or other transparent materials have defects such as scratches or adhesion of dust on the front or back surface, the scattering of light and disturbances in reflection caused by these can be detected to determine whether it is a defect on the front surface or the back surface. is difficult to identify.

In a transparent specimen, it is necessary to detect defects on only one side, such as when inspecting only the side where electronic devices are formed of a GGG crystal that is the substrate of an electronic device, or when detecting fine irregularities on one side. There are cases when inspecting single-sided frosted glass, where light scatters strongly and it is difficult to inspect for defects on the other mirror side, or when inspecting defects at each interface of a transparent body with a multilayer structure. . In such cases, a defect inspection apparatus that can clearly detect defects only on the desired surface has been desired. As described above, an object of the present invention is to provide a defect detection device that can easily detect only defects on the front or back surface of a transparent object.

The principle of the present invention will be explained with reference to FIG. 1A. 1
is a transparent specimen (glass, acrylic resin) with defects on the front and back surfaces, 2 is an irradiation light that irradiates the surface of the transparent specimen 1 diagonally, and 3 is a lens whose depth of focus is selected to be shallower than the thickness of the transparent specimen 1. It is. and,
Its focus is set on the surface of the transparent object 1.
4 is a pinhole whose position is set at the imaging point of the lens 3. 5 is a photoelectric converter. Note that when the position corresponding to the focal length f of the lens 3 is aligned with the surface, a condenser lens 3' may be added as shown in FIG. 1B, and the parallel light may be condensed by the condenser lens 3'.

In the above configuration, when the surface of the transparent object 1 is defect-free, the irradiated light 2 is divided into a component that is specularly reflected on the surface and a component that is refracted and transmitted into the transparent object 1, and is detected by photoelectric detection. The light incident on the vessel 5 is almost zero.

If there is a defect (flaw, adhesion of dust, etc.) on the surface of the transparent object 1, the irradiated light 2 will be scattered and diffracted at that portion. Since the lens 3 is focused on the surface and its imaging point corresponds to the pinhole 4, the scattered light on the surface enters the photodetector 5 as it is.

If there is a defect in a portion other than the front surface, such as the back surface or a portion beyond the depth of focus of the lens 3, the light will not be able to pass through the pinhole 4 at the imaging point even if it is scattered.

Therefore, defects only on the front surface will be detected, and defects on the back surface will be removed.

FIG. 2 shows an example in which the irradiation light 2 is perpendicularly irradiated onto the transparent object 1. In this case, the optical system 3,
4 and 5 are set so as to capture scattered light in the diagonal direction. The operating principle is shown in Figure 1 A and B.
The same is true for .

Now, when carrying out the present invention, a configuration as shown in FIG. 3 is adopted in order to detect a secondary surface defect in a transparent object. Here, 1 is a transparent object, which moves in the direction of the arrow. Reference numeral 6 denotes planar irradiation light that irradiates the surface of the transparent object 1 . 7 is a semi-cylindrical lens,
Its focus is set on the surface of the transparent object 1. A slit 8 is set on the imaging plane of the semicylindrical lens 7. The slit width of the slit 8 can be freely adjusted in accordance with the threshold value of the defect to be detected. Further, its position can also be adjusted in the axial direction of the semicylindrical lens 7. The scattered light is captured by a photoelectric detector (not shown).

The operation is similar to that in FIGS. 1A and 1B and FIG. 2, and the only difference is that defect detection is performed two-dimensionally in this embodiment.

FIG. 4 shows another embodiment. In this case, the irradiation light 9 enters in the form of a beam as shown in the figure, is scanned one-dimensionally by a galvanometer type vibrating mirror 10, is converted into parallel irradiation light 12 by a lens 11, and is applied to the transparent object to be examined. is configured to perform one-dimensional scanning over the surface of In this embodiment, since the irradiation light is beam irradiation, there is an advantage that the detection S/N ratio increases.

FIG. 5 shows still another embodiment, in which the irradiation beam 12 is made to enter from the back surface and the scattering on the front surface is detected as a signal.

FIG. 6 shows an example in which the lens 7 is focused on the back surface. In this case, focusing can be easily achieved by simply adjusting the position of the slit 8 without adjusting the lens 7.

FIG. 7 shows still another embodiment of the present invention. In this case, there is a slit 8 at the imaging point on the surface.
However, in this embodiment, a slit 13 is further provided at a position corresponding to the imaging point on the back surface. When the irradiation beam 12 is incident from an oblique direction, the image points on the front and back surfaces of the transparent object 1 correspond to different locations, and the arrangement of the slits 8 and 13 makes it possible to clearly distinguish between the front and back surfaces. here,
5 and 5' are photoelectric converters for separately detecting the front and back surfaces.

If it is necessary to detect only defects on both the front and back surfaces, it is sufficient to eliminate scattered light generated from defects inside the transparent object. For this purpose, the photoelectric converters 5 and 5' can be covered by a common photoelectric converter, and the slit width of the slits 8 and 13 is made to correspond to the threshold for defect detection on the front surface (detection accuracy) and the threshold value on the back surface. If you choose to do so, the table/
Even if it is impossible to identify the back side, defects on the front and back sides can be detected all at once using the same photoelectric converter.

As described above, the present invention has the effect of easily detecting defects only on the front or back surface of a transparent object. In the past, there was a problem in which scattered light from a surface other than the surface to be detected was detected and a transparent object was mistakenly judged as a defect, but according to the present invention, there is no such problem and transparent The accuracy of defect inspection on a test object can be improved.

[Brief explanation of the drawing]

Figures 1A and B and Figure 2 are configuration diagrams for explaining the principle of the present invention, Figures 3, 4, 5, and 6.
7 are configuration diagrams showing embodiments of the present invention, respectively. 1: Transparent object, 2, 6, 9, 12: Irradiation light,
3, 11: Lens, 4: Pinhole, 5, 5':
Photoelectric converter, 7: Kamaboko-shaped lens, 8, 13:
Slit, 10: Galvanometer type vibrating mirror.

Claims (1)

[Claims] 1. A lens system that is focused on the front or back surface of the transparent object and has a depth of focus shallower than the thickness of the transparent object, a light source that illuminates the focal point, and an imaging plane of the lens system. A slit is provided, whose width and position with respect to the lens system can be adjusted in accordance with a defect threshold, and which transmits the scattered light or diffracted light from the focal point, and which transmits the scattered light or diffracted light transmitted through the slit. A defect detection device comprising a photoelectric converter for detection.