JPH1183755A - Flaw inspecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flaw inspecting device which can be miniaturized and is capable of performing highly accurate inspection even on the textured surface of an object to be inspected. SOLUTION: This flaw inspecting device is provided with a light flux generating source 2, a deflecting means 3 to change the traveling direction of a light flux from the deflecting means 3, a condensing lens 4 to condense the light flux deflected by the deflecting means 3 onto an object to be inspected, a light divider 5 arranged between the deflecting means 3 and the light flux generating source 2 to guide the light flux reflected by the object to be inspected and passed through the condensing lens 4 and the deflecting means 3 to a light receiving element 6, and the light receiving element 6 to convert the light intensity of reflected light flux from the object to be inspected into electric signals. Then the optical axis of a light projecting system formed of the light flux generating source 2, the deflecting means 3, and the condensing lens 4 is made partially coaxial with the optical axis of a light receiving system formed of the condensing lens 4, the deflecting means 3, the light divider 5, and the light receiving element 6, and the deflecting means 3 is arranged on the focal plane of the condensing lens 4 on the incident side of light flux.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flaw inspection apparatus for optically detecting the presence or absence of a flaw on the surface of a long object such as a steel plate or a film, or a disk-shaped member in a non-contact manner.

[0002]

2. Description of the Related Art As a conventional flaw inspection apparatus, a surface of an object to be inspected is irradiated with light by an illuminating means, and reflected light from the object is imaged by an imaging means such as a television camera. There is known an apparatus that inspects the surface of an inspection object for the presence or absence of a scratch based on a change in the luminance distribution of the object. But,
In the above-mentioned conventional apparatus, detection may not be possible depending on the size of the flaw, the direction of the flaw, and the type of the flaw, and there is a problem in detection accuracy.

[0003] Therefore, the applicant has proposed a flaw inspection apparatus 100 shown in FIG.
(JP-A-9-81736). That is, three imaging devices 120A, 120B, and 120C are arranged at predetermined angles on a circular arc with respect to the position of the regular reflection corresponding to the principal ray of the incident light from the light source 110, thereby improving the detection accuracy. I let it. Reference numeral 121 denotes a condenser lens, reference numeral 122 denotes a light receiving element, and reference numeral 130 denotes an inspection object.

In some cases, the surface of the inspection object has a flaw (referred to as texture) having a fine uneven structure such as a fold of a cloth. When observing such a texture, there is a conventional flaw inspection apparatus shown in FIG.
That is, instead of observing specularly reflected light from the surface 170 of the inspection object using the spot light source 140 and the light receiving means 160, only the scattered light 220 due to texture is observed. However, in the conventional flaw inspection apparatus shown in FIG. 7, since the spot light source 140 has directivity, for example, even if the texture 180A in FIG. There was a problem that it was difficult to observe things in different directions. Therefore, as shown in FIG. 8, a diffusion plate 150 such as a ground glass plate is provided between the spot light source 140 and the surface 170 of the inspection object.
Is provided to uniformly illuminate the surface 170 of the object to be inspected by a surface light source having a minimum directivity so that textures having different processing directions can be observed. In FIG. 8, reference numeral 21 denotes scattered light by the diffusion plate 150, and reference numeral 230 denotes specular reflected light.

[0005]

However, in the flaw inspection apparatus shown in FIG. 6 and the flaw inspection apparatus shown in FIG. 8, the optical system (illumination optical system) on the light emitting side and the optical system on the light receiving side are separately provided. The configuration has a disadvantage that it is difficult to reduce the size of the device. Further, in the flaw inspection apparatus according to FIG. 6, since a plurality of image pickup means are required, an adjustment operation for matching the fields of view of the respective image pickup means is troublesome. Further, in the flaw inspection apparatus according to FIG. 8, when inspecting an inspection object having a texture, only the scattered light component due to the texture is received, and the direct light (specular reflection light) due to regular reflection is not received. Moreover, it has been difficult to obtain the effect of illuminating the surface of the inspection object from all directions with a light source having no directivity.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a flaw inspection apparatus capable of miniaturizing the apparatus and performing inspection with high accuracy even on the surface of the inspection object having a texture.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, according to the first aspect of the present invention, a light beam generating source, a deflecting means for changing a traveling direction of a light beam from the light beam generating source, and a deflecting device. A condensing lens for condensing a light beam on the object to be inspected, and disposed between the deflecting unit and the light beam generation source, the condensing lens reflected from the object to be inspected, and a light beam passing through the deflecting unit. A light splitter for guiding the light to the light receiving element; and a light receiving element for converting the light intensity of the reflected light beam from the inspection object into an electric signal. Then, the optical axis of the light projecting system including the light beam generating source, the deflecting unit, and the condensing lens is aligned with the optical axis of the light receiving system including the condensing lens, the deflecting unit, the optical splitter, and the light receiving element. Partial coaxial. Further, the deflecting means is arranged on a focal plane on the incident side of the light beam of the condenser lens.

According to a second aspect of the present invention, in the flaw inspection apparatus according to the first aspect, the deflecting means is a galvanometer-type mirror.

According to a third aspect of the present invention, in the flaw inspection apparatus according to the first aspect, the deflecting means is an acousto-optic deflector.

According to a fourth aspect of the present invention, in the flaw inspection apparatus according to the first, second or third aspect, the light receiving element is a one-dimensional array sensor.

According to a fifth aspect of the present invention, in the flaw inspection apparatus according to the first, second, or third aspect, the light receiving element is a two-dimensional array sensor.

[0012] The invention according to claim 6 is the invention according to claims 1, 2,
6. The flaw inspection apparatus according to 3, 4, or 5, wherein a cross-sectional intensity distribution of a light beam generated from the light beam source is a Gaussian distribution.

According to a seventh aspect of the present invention, there is provided a light beam generating source, means for converting a light beam from the light beam generating source into an annular light beam centered on an optical axis, and converting the annular light beam by the means into an object to be inspected. A condensing lens for converging light upward, and a light-receiving element disposed between the means for converting the light into a ring-shaped light beam and the light-collecting lens, and at a position other than the optical path of the ring-shaped light beam. The light receiving element detects only scattered light that has passed through the condensing lens among light rays that are condensed and reflected on the inspection object.

According to an eighth aspect of the present invention, in the flaw inspection apparatus according to the seventh aspect, the means for converting the light beam from the light beam generation source into an annular light beam centered on the optical axis is a biconvex conical lens. It is characterized by being.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a principle diagram of the first embodiment. In the first embodiment, a disc-shaped subject (test object)
Assuming that a scratch test of 90 is to be performed, the subject 90 is indicated by an arrow 9
5 shall rotate. The flaw inspection apparatus 1 according to the first embodiment has a light beam source 2, a deflecting unit 3, a condenser lens 4, a light splitter 5, and a light receiving element 6 integrally arranged in a housing member (not shown). It is.

The light source 2 includes a light source and means for generating a predetermined light beam. For example, a He-Ne laser or a semiconductor laser equipped with a collimating lens is used. Further, a beam shaping prism for obtaining a light beam of a predetermined shape, a beam expander for obtaining a light beam of a predetermined size, and a lens for changing the cross-sectional intensity distribution of the light beam to a predetermined distribution (for example, Gaussian distribution) And so on.

The deflecting means 3 is for controlling the direction of the light beam 50 generated from the light beam generating source 2 and, together with the condensing lens 4 described later, scans the condensed beam on the subject 90 one-dimensionally. Play a role. As the deflecting means 3,
For example, there are a galvanometer-type mirror, a polygon mirror (for example, a polygon mirror), and an acousto-optic deflector. In particular, the acousto-optic deflector can be controlled at high speed.

The condenser lens 4 is for condensing the light beam deflected by the deflecting means 3 on the subject 90. Light beams 51A and 51B incident on the subject after being deflected
The deflecting means 3 should be provided on the entrance-side focal plane of the condensing lens 4 so as to make a so-called telecentric optical system in which the principal ray is parallel to the optical axis 56 (the optical axis of the condensing lens). Is desirable. As described above, by using a telecentric optical system, a change in the state of focusing when the focused beam is scanned on the subject is reduced, and a detection error by the optical system can be reduced. Reference numeral 52 denotes a scanning line on the subject due to the deflected light beam. Further, the light beam condensed and reflected on the subject returns along an optical path substantially similar to the incident optical path.

The light beam condensed and reflected on the subject passes through the condenser lens 4 and the deflecting means 3 again, and is guided to the light receiving element 6 by the optical splitter 5 (reference numeral 53). As the optical splitter 5, for example, a half mirror on which a metal film is deposited,
A polarizing beam splitter composed of a dielectric multilayer film is used.

The light receiving element 6 detects direct light reflected from the surface of the subject. As the light receiving element 6, for example, a silicon photodiode (SPD), one-dimensional or two-dimensional
A three-dimensional CCD array sensor is used. FIG. 2 is a diagram illustrating an embodiment of the light receiving element 6. Symbols 6a to 6i are
The figure shows a pixel of a CCD (charge coupled device), and a pixel 6c at the center of the light receiving element 6 is arranged so as to receive the principal ray 54 (see FIG. 1) of the regular reflected light beam. Other pixels 6a,
The light beams 6b, 6d, 6e, 6f, 6g, 6h, and 6i receive light beams other than the main light beam (for example, the outermost light beams 55A and 55B in FIG. 1) in the regular reflected light beam.

The cross-sectional intensity distribution of the light beam incident on the light receiving element 6 changes depending on the state of the surface of the subject 90. In the present embodiment, the cross-sectional intensity distribution of the light beam emitted from the light beam source 2 is set to be a Gaussian distribution. If there is a defect such as a scratch on the surface of the subject 90, the cross-sectional intensity distribution of the regular reflection light beam incident on the light receiving element 6 changes (for example, the intensity distribution becomes asymmetric about the optical axis). Due to the change, a computer (not shown) can determine with high accuracy whether or not there is a defect on the object.

As described above, in the present embodiment, the light axis on the light projecting side composed of the light beam generating source 2, the deflecting means 3, and the condensing lens 4, and the light beam reflected from the subject 90 to the light receiving element 6 are collected. The optical axis on the light receiving side including the optical lens 4, the deflecting means 3, and the optical splitter 5 is partially coaxial.

FIG. 3 is a specific configuration diagram of the first embodiment. Galvanometer type mirror 3A as deflection means 3
It was used. In addition, the rotation axis of the galvanometer type mirror 3A is arranged so as to be positioned at the focal point on the incident side of the condenser lens 4, thereby realizing a telecentric optical system as in FIG.

FIG. 4 is a configuration diagram of the second embodiment.
The flaw inspection device 10 according to the second embodiment includes a light flux source 2
, A biconvex conical lens 11, a condenser lens 12, and light receiving elements 13A, 13B, 13C disposed between the biconvex conical lens 11 and the condenser lens 12.

The biconvex conical lens 11 is disposed between the light source 2 and the condenser lens 12, and converts the light from the light source 2 into an annular light 61 around the optical axis. . In addition, 63 is the principal ray of the optical path of the light beam 61, and 64 is the optical axis of the condenser lens 12 and the biconvex conical lens 11. The condenser lens 12 condenses the annular light flux 61 on the surface of the subject 90.

The light receiving elements 13A, 13B, 13C are provided between the biconvex conical lens 11 and the condenser lens 12, and
It is arranged at a position other than the optical path of the annular light beam 61.
This is for detecting only the scattered light component among the light beams condensed on the surface of the subject 90 and reflected. The direct light condensed on the surface 90 of the subject and specularly reflected travels backward in the optical path of the annular light flux 61. Therefore, the light receiving element 1
Direct light that is specularly reflected from the surface of the subject 90 is not incident on 3A, 13B, and 13C. In the case of the subject 90 having the texture 91 on the surface, when the light is condensed on the texture 91, scattered lights 71A, 71B, and 71C are generated. In the drawing, the light rays of the scattered light are indicated by reference numeral 71. Scattered light 71
A, 71B, 71C are light receiving elements 13A, 13B, 13
C receives the light.

FIG. 5 is a conceptual diagram in the case of performing a flaw inspection of a disc-shaped subject 90 using the second embodiment. By rotating the subject 90 in the direction of arrow A about the central axis and moving the flaw inspection device 10 in the radial direction of the subject 90 as shown by the direction of arrow B, the entire surface of the subject 90 can be inspected. Become.

It is also possible to arrange a deflecting means such as an acousto-optic polarizer between the biconvex conical lens 11 and the light receiving element 13 to scan the beam condensing position on the surface of the subject 90. . In this case, it is desirable to arrange the deflecting means on the incident-side focal plane of the condenser lens 12. By doing so, the condensing state of the condenser lens 12 (such as the inclination angle of the light beam) becomes substantially constant regardless of the deflection, and the light receiving element 13
Can detect only scattered light.

[0029]

As described above, according to the first to sixth aspects of the present invention, the optical axis of the optical system on the light projecting side and the optical axis of the optical system on the light receiving side are partially coaxial. Miniaturization is possible.

According to the fourth or fifth aspect of the present invention, since the light receiving elements are arrayed, the adjustment work after the light receiving elements are assembled is extremely easy.

Further, according to the present invention, when inspecting an object having a texture, only the scattered light component due to the texture is received, and the direct light due to regular reflection is not received. In addition, an effect of illuminating the surface of the inspection object with a light source having no directivity can be obtained, and the detection accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is a principle diagram of a first embodiment.

FIG. 2 is a diagram showing an embodiment of a light receiving element.

FIG. 3 is a configuration diagram of the first embodiment.

FIG. 4 is a configuration diagram of a second embodiment.

FIG. 5 is a conceptual diagram illustrating a case where a disk-shaped subject is inspected for damage using the second embodiment.

FIG. 6 is a conceptual diagram of a conventional flaw inspection device.

FIG. 7 is a conceptual diagram of a conventional flaw inspection apparatus when observing a texture.

FIG. 8 is a conceptual diagram of a conventional flaw inspection device when observing a texture.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 flaw inspection device 2 light beam generating source 3 deflecting means 3 A galvanometer-type mirror 4 condensing lens 5 light splitter 6 light receiving element 6 c , 6i Pixel that receives light other than the principal ray of the specularly reflected light beam 10 Scratch inspection device 11 Biconvex conical lens 12 Condensing lens 13 Light receiving element 13A, 13B, 13C Light receiving element

Claims (8)

[Claims] 1. A light source, a deflecting means for changing a traveling direction of a light beam from the light source, a condensing lens for condensing a light beam deflected by the deflecting means on an inspection object, and the deflecting means. A light splitter disposed between the light source and the light splitter for guiding a light beam reflected from the object to be inspected and passing through the condenser lens and the deflecting means to a light receiving element; and a light beam reflected from the object to be inspected. A light-receiving element that converts intensity into an electric signal, the light beam generation source, the deflecting unit, an optical axis of a light projecting system including the condenser lens, the condenser lens, the deflecting unit, the optical splitter, A flaw inspection apparatus, wherein the optical axis of a light receiving system including a light receiving element is partially coaxial, and the deflecting unit is arranged on a focal plane on the incident side of the light beam of the condenser lens. 2. The flaw inspection apparatus according to claim 1, wherein said deflecting means is a galvanometer-type mirror. 3. A flaw inspection apparatus according to claim 1, wherein said deflecting means is an acousto-optic deflector. 4. The flaw inspection device according to claim 1, wherein the light receiving element is a one-dimensional array sensor. 5. The flaw inspection device according to claim 1, wherein the light receiving element is a two-dimensional array sensor. 6. The flaw inspection device according to claim 1, wherein a cross-sectional intensity distribution of a light beam generated from the light beam generation source is a Gaussian distribution. 7. A light beam source, means for converting a light beam from the light beam source into an annular light beam centered on the optical axis, and a collector for converging the annular light beam on the inspection object by the means. An optical lens, and a light receiving element disposed between the means for converting the light into the annular light flux and the condenser lens, and at a position other than the optical path of the annular light flux, wherein the light receiving element is an object to be inspected. A flaw inspection device, wherein only the scattered light that has passed through the condenser lens is detected from among the rays converged and reflected on the upper side. 8. The flaw inspection device according to claim 7, wherein the means for converting the light beam from the light beam source into a ring-shaped light beam centered on the optical axis is a biconvex conical lens. Inspection equipment.