JPS63173940A - Optical type defect detector - Google Patents

Abstract

PURPOSE:To enable detection of a defect at a high detection accuracy while unnecessiating unidirectional mechanical scanning, by interposing a spatial filter using an array of a lens and a photo detection element to compactive an optical system. CONSTITUTION:When no defect exists in an object 10 to be inspected, parallel light 12 is incident into a refractive index distribution type lens 15 of a lens array 14 as it to be focused with a lens 15 on the outer surface of a cover material 19 of an image sensor 16, but not into a photo detection element 18 as being intercepted with a filter light shielding section 20A. On the other hand, when there is a defect such as scratches and foreign matters on the surface of the object 10 being inspected, incident light is scattered by this defect 21 and light beams scattered are incident into the lens 15 at a certain angle to the optical axis thereof. As a result, light is emitted at a position away from the optical axis and incident into the photo detection element 18 of the sensor passing through a light shielding section 20B in the perimeter of a light shielding section 20A of a spatial filter, namely, a transparent cover material 19 of the image sensor without focusing on a focal plane.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an apparatus for optically detecting defects such as scratches and foreign objects present in translucent or reflective objects.

[Description of Prior Art] A device shown in FIG. 6 has been widely used as a device for optically detecting surface defects such as scratches.

In the apparatus shown in FIG. 6, a parallel light beam 2 emitted from a laser light source 1 is reflected by a reflecting surface 3A of a rotating polygon mirror 3, and then condensed by a condensing lens 4 to form a minute spot 6 on the surface of a subject 5.
The spot 6 scans the surface of the subject 5 as the polygon mirror 3 rotates. If there are defects such as deposits or scratches on the irradiated minute spot, the irradiated light will be scattered and the scattered light 8 will enter the photodetector element 7 such as a photomultiplier tube, increasing the amount of light received. Therefore, the above defects can be detected without contact.

[Problems to be Solved by the Invention] The conventional optical defect detection apparatus described above has disadvantages in that the optical system requires a large space and requires expensive special parts such as a rotating polygon mirror.

Furthermore, since it is a one-point scan and the measurement point is mechanically changed, there is also the problem that it takes a long time to measure a wide-area object.

[Means for solving the problem] A light source (13) that projects a parallel light beam onto the subject (10);
an array of photodetecting elements (18) arranged in large numbers in a direction across the subject (10), facing the subject (10);
a lens (15) array that focuses the light flux transmitted or reflected by the subject (10) onto each of the photodetection elements (18), and arranged between the lens (15) and the photodetection element (18), A defect detection device was constructed by providing an array of spatial filters (20) that block light of a specific spatial frequency component out of the light transmitted through the lens and allow other component light to pass through.

[Function] When the object to be examined has no defects, the light transmitted or reflected by the object enters the lens in parallel, and is e.g. The light is blocked by the light shielding part and is not received by the photodetecting element.

In addition, if a defect exists on the surface or inside of the object, the projected light beam is scattered by the defect, enters the lens at an angle to the optical axis, exits at a position away from the optical axis at the lens exit surface, and is filtered through the spatial filter. The light passes through the light-transmitting part provided on the outer layer of the light-shielding part and enters the photodetecting element. In this way, defects present in the object can be detected by increasing the amount of light received by the photodetecting element.

In addition to making the spatial filter a high-pass transmission type that transmits high spatial frequency component light and blocks low spatial frequency component light as described above, it can also be used as a low-pass transmission type by reversing the pattern of the light-shielding part and the light-transmitting part. Similar detection can also be performed.

[Embodiments] The present invention will be described in detail below based on embodiments shown in the drawings.

In FIGS. 1 to 4, reference numeral 10 denotes an object to be examined, for example, a transparent plate such as a glass plate or a plastic plate, which is transported in the direction of an arrow 11. A light source 13 that projects parallel light 12 extending in a line in a direction perpendicular to the surface of the subject 10 and across the subject 10 is arranged below the transport path 11 . Further, above the subject 10 at the same location, a lens array 14 for condensing the light 12 is arranged.

This lens array 14 is made by integrally fixing a large number of gradient index lenses 15, each of which has a refractive index distribution that gradually decreases from the center toward the outer periphery, in a transparent cylindrical body, bundled in a row with their optical axes parallel to each other. The arrangement direction of the lenses 15 is perpendicular to the transport direction of the subject 10, and the lenses 15 are arranged slightly apart from the surface of the subject 10. Furthermore, a one-dimensional image sensor 16 is arranged above this lens array 14.

This image sensor 16 has a large number of photodetecting elements 18 arranged in a row in a package 17 and is protected by a transparent cover material 19. is transparent cover material 19
It is placed so that it matches the outer surface of the surface. Further, the optical system specifications are set so that an image of the surface of the subject 10 is formed on the detection element 18 at the same magnification (and a spatial filter 20 is provided on the cover material 18).

That is, a small circular light-shielding film centered on the optical axis of the lens 15 is formed by adhering a metal film or the like on the outer surface of the transparent cover material 19, and this is used as the light-shielding part 2OA of the spatial filter. The surrounding area is left transparent and used as the light-transmitting part 20B of the spatial filter. A large number of the filter light shielding parts 2OA are arranged and formed on the transparent cover material 19 at regular intervals as shown in FIG. 4, corresponding to each lens 15 of the lens array 14.

In the defect detection device configured as described above, if there is no defect in the object 10, the parallel light 12 emitted from the light source as shown in FIG. 2 enters each lens 15 in a parallel light state, and the lens Covering material 1 of image sensor 16 by 15
Although the light is focused on the outer surface of the filter 9, it does not enter the photodetecting element 18 because it is blocked by the filter light shielding part 2OA.

On the other hand, if there is a defect such as a scratch or a foreign object on the surface of the object 10, the incident light is scattered by the defect 21 as shown in FIG. The light enters at a position away from the optical axis, and passes through the light-transmitting part 20B1 around the light-shielding part 2OA of the spatial filter, that is, the transparent cover material 19 of the image sensor, without being focused on the focal plane. The light is incident on the photodetecting element 18 of the sensor.

In this way, only the scattered light due to defects such as scratches and deposits is imaged on the detection element 18 and detected, so that inspection with a good signal-to-noise ratio can be performed.

FIG. 5 shows another embodiment of the invention.

This example is a reflection type detection device suitable for detecting defects such as scratches and foreign objects on the surface of the specimen 10 made of non-transparent material such as metal. parallel light 12 from an oblique direction with respect to the surface of the subject 10
A lens array 14 and an image sensor 16 with a spatial filter similar to those in the previous example are arranged along the optical axis of the light reflected on the surface of the subject 10.

In the embodiment described above, the light shielding part 2 of the spatial filter 20
The OA was designed to have a shape and size that blocks parallel incident light to the lens and allows scattered incident light to pass through the outside of the light shielding part.However, on the contrary, the light shielding part 2OA is formed into, for example, an annular shape and the center part is a transparent part. The parallel incident light may be made incident on the detection element, and the scattered light may be blocked by the light shielding section.

In the present invention, the light blocking part 2OA and the light transmitting part 20B of the spatial filter
The shape of can be arbitrarily set depending on the optical characteristics of the defect to be detected. Further, the spatial filter may be provided separately from the image sensor 16. Furthermore, by arranging the lenses 15 and the photodetecting elements 18 in a two-dimensional matrix, the inspection speed can be further improved.

[Effects of the Invention] According to the present invention, since an array of lenses and photodetecting elements is used, the optical system becomes extremely compact, and unidirectional mechanical scanning is not required, allowing rapid defect inspection with inexpensive equipment. Can be implemented.

In addition, since a spatial filter is provided, only the area where scratches, deposits, etc. exist can be imaged onto the detection element array, and unnecessary noise components do not appear, resulting in a good S/N ratio and high detection. Defects can be detected with precision and without contact.

[Brief explanation of the drawing]

10...Object 12...Parallel light 1
3... Light source 14... Lens array
15... Gradient index lens 16...
・Image sensor 18...Photodetection element 19・
...Transparent cover material 20... Spatial filter 2OA... Light shielding part 20B... Light transmitting part 21... Defective part Fig. 1, Fig. 3 Figure 2 Figure 4 Figure 5 Figure 6 Procedure Amendment Book July 1939 I? Nittoku Kansho - issue January 1932 lψ Nittoku Kosho -
No. Patent application submitted (1) -6 Name of the invention Optical defect detection device 3 Relationship to the person making the amendment Case Patent applicant address Address 4-8 Doshomachi, Higashi-ku, Osaka-shi, Osaka Name (
<100) Nobu Saiga, Representative of Nippon Sheet Glass Co., Ltd.
Agent Ogu 7, Contents of the amendment 1) The following sentence is added between the blank line and the blank line on page 9 of the specification. 7 is a perspective view showing one embodiment of the present invention, FIGS. 2 and 3 are side sectional views showing the operation of the device shown in FIG.
5 is a side sectional view showing another embodiment of the present invention, and FIG. 6 is a perspective view showing a conventional device. "that's all

Claims (3)

[Claims] (1) A light source that projects a parallel light beam onto a subject; an array of photodetecting elements arranged in large numbers in a direction across the subject facing the subject; and a light source that projects a parallel light beam onto the subject; A lens array that focuses light on a photodetection element, and a spatial filter that is placed between the lens and the photodetection element and blocks light of a specific spatial frequency component of the light transmitted through the lens and allows light of other components to pass through. An optical defect detection device comprising an array. (2) In claim 1, the lens:
An optical defect detection device that is a gradient index lens that has a transparent cylindrical body with a refractive index distribution that changes from the center to the outer periphery. (3) An optical defect according to claim 1, wherein the light shielding part of the spatial filter is formed on the surface of the transparent cover of the photodetecting element array, and the surface is arranged to coincide with the focal plane of the lens. Detection device.