JPH11295212A - Surface inspection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface inspection apparatus by which the uneven state on the surface of an object to be inspected can be inspected precisely and stably even when the object to be inspected is installed in a tilted state with reference to the inspection apparatus. SOLUTION: An inspection apparatus is constituted in such a way that, for example, white light which is emitted from a point source 1 is changed into parallel light by a lens 2, that it is then reflected by a semitransparent mirror 3 so as to irradiate the surface P of an object to be inspected and that its reflected light is received by a light receiving face 7 via the semitransparent mirror 3, a lens 4, a pinhole 5 and a lens 6 so as to be observed. In the inspection apparatus, the angle of inclination from a prescribed position on the surface P of the object to be inspected is measured by a gap sensor 8a, a gap sensor 8b or the like, and the position of, e.g., the point source 1 is moved on the basis of its measured value. Thereby, the angle of incidence on the surface P of the object, to be inspected, of the parallel light is adjusted in such a way that the light receiving optical system of the pinhole 5, the light receiving face 7 or the like is situated on the optical axis of the parallel reflected light reflected by the surface P of the object to be inspected. Thereby, even when the object to be inspected is installed in a tilted state with reference to the inspection apparatus, the uneven state on the surface P of the object to be inspected can be inspected precisely and stably.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light projecting optical system for projecting parallel light onto a surface of an object to be inspected, and a reflected light projected from the light projecting optical system and reflected by the surface of the object to be inspected. A light receiving optical system arranged to receive the reflected light, the light receiving optical system being arranged in the direction of the optical axis, and inspecting the unevenness of the surface of the inspection object based on the luminance distribution of the reflected light received by the light receiving optical system. It relates to an inspection device.

[0002]

2. Description of the Related Art As a method for measuring a minute angular displacement on a surface of a planar object, that is, a state of unevenness, a method applying the Schlieren method has been conventionally proposed. The above-mentioned Schlieren method is generally known as a qualitative measurement method for knowing a change in the refractive index gradient of a gas, a liquid, or the like. The light transmitted through the object to be inspected is collected at one point by a lens or a concave mirror, and a part of the light-collecting surface is cut off with a knife edge or the like, and the transmitted light is received. Is used to detect a change in the gradient of the refractive index of the object to be inspected based on the light / dark distribution. If there is a change in the refractive index of a part of the inspection object, the light passing therethrough is bent and blocked by the knife edge, so that it appears as a dark part on the image. A surface inspection apparatus to which the above-described Schlieren method is applied has been proposed in, for example, Japanese Patent Application Laid-Open No. 9-105724. As shown in FIG. 5, the surface inspection apparatus A0 constitutes a reflection type optical system to which the above-mentioned Schlieren method is applied. In the surface inspection apparatus A0 shown in FIG. 5, white light emitted from the light source 52 becomes a point light source through the
4 makes parallel light. Then, the light is reflected by the half mirror 55 and is irradiated perpendicularly to the inspection object surface 51. The light reflected by the inspection object surface 51 is transmitted through the half mirror 55 through a lens 56 and passes through a lens 57.
And is observed on the light receiving surface 58. At this time, the light incident parallel to the smooth surface (healthy portion) of the inspection object surface 51 is specularly reflected here (FIG. 6A) and appears as a bright portion on the light receiving surface 58. On the other hand, light incident parallel to the uneven portion of the inspection object surface 51 is reflected here in a direction deviated from the regular reflection direction (FIG. 6B). It cannot be reached and is observed as a dark part (defect) in a bright part (healthy part). If the deflection angle is small even if the surface has irregularities, the reflected light is condensed on the light receiving surface 58 as shown by oblique lines in FIG. By providing the pinhole 59 at the light condensing point A as shown by the dashed line, it is possible to completely block the reflected light from the uneven portion.

[0003]

In the conventional surface inspection apparatus A0, it is necessary that the surface 51 of the inspection object be perpendicular to the optical axis of the incident light in order to perform an accurate inspection. Become. However, when the above-described surface inspection apparatus A0 is incorporated in an actual operation line and used, it is difficult to always satisfy the above prerequisites. For example,
When the surface inspection of each inspection object flowing on the conveyor is continuously performed, the inspection object is easily inclined due to variation in the inclination or vibration of the conveyor. of course,
There is no problem if the inclination of the inspection object can be quickly and accurately adjusted on the conveyor, but it is not realistic in view of cost and the like. The present invention has been made in view of the above circumstances, and an object of the present invention is to accurately and irregularly state the surface of an inspection object even if the inspection object is installed in a state inclined with respect to the inspection apparatus. An object of the present invention is to provide a surface inspection device capable of performing stable inspection.

[0004]

In order to achieve the above object, the present invention provides a light projecting optical system for projecting parallel light onto a surface of an object to be inspected, and a light projecting optical system projected from the light projecting optical system. A light receiving optical system arranged in the direction of the optical axis of the reflected light reflected by the surface of the object, and receiving the reflected light; and the inspection object based on the luminance distribution of the reflected light received by the light receiving optical system. In a surface inspection device that inspects the unevenness of the surface of
An inclination angle detecting means for detecting an inclination angle of the surface of the inspection object from a predetermined direction, and a light reflected by the surface of the inspection object based on the inclination angle of the surface of the inspection object detected by the inclination angle detecting means. Adjusting means for adjusting an incident angle of light from the light projecting optical system to the surface of the inspection object and / or a position of the light receiving optical system so that the light receiving optical system is positioned on the optical axis of the parallel reflected light. The surface inspection apparatus is characterized by comprising: Further, when adjusting the incident angle of light from the light projecting optical system to the surface of the inspection object, the adjusting means can be configured to move the position of a light source constituting the light projecting optical system, for example. . Alternatively, if a plurality of light sources constituting the light projecting optical system are provided and the adjusting means selects one from the plurality of light sources, the movement of the light sources does not involve a mechanical operation, so that a higher speed can be achieved. Processing can be performed. Further, the adjusting means is
It is also possible to configure so as to adjust the angle of the mirror constituting the light projecting optical system. Further, if the inclination angle detecting means detects the distance to the surface of the inspection object at a plurality of positions and detects the inclination angle based on the detection result, non-contact measurement is possible. Of course, a so-called inclinometer utilizing gravity can be used.

[0005]

According to the surface inspection apparatus of the present invention, the parallel reflection reflected on the surface of the inspection object based on the inclination angle of the surface of the inspection object from the predetermined direction detected by the inclination angle detecting means. The adjusting means adjusts the incident angle of light from the light projecting optical system to the surface of the inspection object and / or the position of the light receiving optical system so that the light receiving optical system is positioned on the optical axis of light. Is done. Therefore, even if the inspection object is installed in a state inclined with respect to the inspection device,
It is possible to accurately and stably inspect the unevenness state of the surface of the inspection object. When adjusting the incident angle of light from the light projecting optical system to the surface of the inspection object, the adjusting means may be configured to move the position of a light source constituting the light projecting optical system, for example. If a plurality of light sources constituting the light projecting optical system are installed and the adjusting means selects one from the plurality of light sources, the movement of the light sources does not involve a mechanical operation, so that a higher speed can be achieved. Processing becomes possible. If the inclination angle detecting means detects the distance to the surface of the inspection object at a plurality of positions, and the inclination angle is detected based on the detection result, non-contact measurement is possible. .

[0006]

Embodiments and examples of the present invention will be described below with reference to the accompanying drawings to provide an understanding of the present invention. The following embodiments and examples are mere examples embodying the present invention, and do not limit the technical scope of the present invention. FIG. 1 is a schematic diagram showing a schematic configuration of a surface inspection apparatus A1 according to an embodiment of the present invention,
2 is a diagram showing an example of the moving stage 10, FIG. 3 is a diagram showing an example of a point light source array 10 ', and FIG. 4 is a schematic diagram showing a schematic configuration of a surface inspection apparatus A2 according to an embodiment of the present invention.
As shown in FIG. 1, a surface inspection apparatus A1 according to the present embodiment includes a point light source 1 installed on a moving stage 10 and movable in a vertical direction, and a lens for converting light from the point light source 1 into parallel light. 2, a half mirror 3 for reflecting parallel light from the lens 2 in the direction of the surface P of the inspection object, and condensing the light reflected from the surface P of the inspection object at one point (condensing point a) and receiving the light. Lenses 4 and 6 that reach the surface 7, a pinhole 5 that is provided at the position of the condensing point a and allows only predetermined reflected light to pass, and a light receiving surface that receives reflected light from the surface P of the inspection object A gap sensor 8 provided near the end of the surface P of the inspection object so as to face the surface P of the inspection object and measuring a gap between the surface P of the inspection object;
a, 8b and a control unit 9 for controlling the moving stage 10 based on the sensor outputs G1, G2 of the gap sensors 8a, 8b. Here, the point light source 1, lens 2, and half mirror 3 constitute a light projecting optical system, and the lens 4, pinhole 5, lens 6, and light receiving surface 7 constitute a light receiving optical system. For the point light source 1, for example, a halogen light source is guided by an optical fiber, and a pinhole is arranged at the fiber outlet, and a substantially point light source can be used. Alternatively, an LED or a laser can be used.
The white light emitted from the point light source 1 is converted into parallel light by the lens 2, reflected by the half mirror 3, and irradiated on the surface P of the inspection object. The light reflected on the inspection object surface P is transmitted through the half mirror 3, and the light is condensed at a focal point “a” by a lens 4. Are received by the light receiving surface 7 and observed. Here, the inspection object surface P
Is perpendicular to the incident light from the point light source 1, light incident parallel to the smooth surface (healthy part) of the surface P of the inspection object is specularly reflected here (FIG. 6 (a)). )), Light that appears as a bright portion on the light receiving surface 7 and is incident parallel to the uneven portion of the surface P of the inspection object is reflected in a direction deviated from the regular reflection direction here (FIG. 6B). , Cannot reach the light-receiving surface 7 out of the pinhole 5, and is observed as a dark part (defect) in a bright part (healthy part). However, when the inspection object surface P is not perpendicular (inclined) to the incident light from the point light source 1, the inspection object surface P
The light reflected on the smooth surface (healthy portion) of the pinhole 5
, It is impossible to perform an accurate inspection. Therefore, the surface inspection apparatus A1 according to the present embodiment solves the above-described problem by using the gap sensors 8a and 8b, the control unit 9, and the point light source 1 installed on the moving stage 10. ing. The details are described below.

The gap sensors 8a and 8b (an example of an inclination angle detecting means) are provided near the end of the surface P of the inspection object and opposed to the surface P of the inspection object. The distance between the gap sensors 8a and 8b is L1, and the gap sensors 8a and 8b are in a state where the surface P of the inspection object is installed perpendicular to the incident light from the point light source 1. The sensor outputs (measured values of the distance from the inspection object surface P) G1 and G2 are set to be equal. When the inspection object is set at a predetermined position by, for example, a conveyor, distances G1 and G2 with respect to the inspection object surface P are measured by the gap sensors 8a and 8b. The gap sensor 8
Since the distance between a and 8b is L1, the inclination angle θ of the inspection object surface P is obtained by the following equation. θ = tan ⁻¹ ((G2−G1) / L1) (1) On the surface P of the inspection object installed with the inclination angle θ ≠ 0, the same accurate inspection result as in the state with the inclination angle θ = 0 In order to obtain the light receiving surface 7, the optical axis of the parallel reflected light reflected on the inspection object surface P passes through the pinhole 5 and
The incident angle of the parallel light on the inspection object surface P may be shifted by, for example, moving the position of the point light source 1 so as to reach. Here, the moving amount X of the point light source 1
1 is obtained by the following equation. X1 = tan2θ × L2 (2) where L2 is the distance between the point light source 1 and the lens 2 (the lens 2
The control unit 9 calculates the X1 from the outputs G1 and G2 from the gap sensors 8a and 8b and the X1 from the equations (1) and (2).
Is calculated, and the point light source 1 is moved by the moving stage 10 by the distance X1. As a result, similarly to the case where the surface P of the inspection object is not inclined, the optical axis of the parallel reflected light reflected by the surface P of the inspection object passes through the pinhole 5 as shown in FIG. The light reaches the light receiving surface 7.
Therefore, if inspection is performed as usual in this state, an accurate inspection result can be always obtained regardless of the presence or absence of the inclination angle of the surface P of the inspection object. Here, the control unit 9 and the moving stage 10 are examples of an adjusting unit. As described above, in the surface inspection apparatus A1 according to the present embodiment,
The surface P of the inspection object is determined by the gap sensors 8a and 8b.
Is detected, and the point light source 1 is moved by the amount of movement and the movement amount X1 obtained from the above equations (1) and (2), so that the parallel reflection reflected on the inspection object surface P is obtained. Since the light receiving optical system such as the pinhole 5 and the light receiving section 7 is adjusted on the optical axis of the light, an accurate inspection is always performed regardless of the presence or absence of the inclination angle of the surface P of the inspection object. The result is obtained.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the above embodiment, for simplicity, the inclination of the inspection object surface P is limited to only rotation about one horizontal axis. In general, the gap sensor should be at least 3
Required. In addition, the moving stage of the point light source 1 needs to be movable in two axial directions as shown in FIG. Further, instead of moving the position of the point light source 1 as described above, the point light source 1 is
A point light source array 10 ′ arranged in a lattice in the Y plane (in a plane substantially perpendicular to the optical axis) may be provided, and only one light source may be selectively turned on by the control unit 9. In this case, since the movement of the point light source does not involve any mechanical operation, the response is extremely good and the processing can be speeded up. In addition to the movement of the point light source, the angle of incidence of the parallel light on the inspection object surface P may be changed by adjusting the angle of the half mirror 3, for example. Also, instead of changing the angle of incidence of the parallel light on the inspection object surface P, the light receiving optical system, that is, the lens 4, 6, the pinhole 5, and the light receiving surface 7 are moved so that the inspection object surface P Even if the light receiving optical system can be adjusted so as to be located on the optical axis of the parallel reflected light reflected by the above, the same effect as in the above embodiment can be expected. Of course, it is needless to say that it can be used together with the change of the incident angle. In addition to the non-contact type gap sensor described above, various known sensors such as a so-called inclinometer using gravity can be used as the inclination angle detecting means. Further, instead of using a half mirror as in the above-described surface inspection apparatus A1, parallel light may be incident from an oblique direction as in a surface inspection apparatus A2 shown in FIG. In this case, since the surface to be inspected has a periodic rough surface structure in one direction such as a rolled surface due to oblique incidence, only the direction in which the reflected light is diffracted is emphasized and the normal surface is emphasized. However, there is a drawback that a periodic distribution cannot be dealt with because a luminance distribution occurs, but there is a merit that the number of parts can be reduced.

[0009]

As described above, according to the present invention, there is provided a light projecting optical system for projecting parallel light to a surface of an inspection object, and a light projecting from the light projecting optical system and reflected by the surface of the inspection object. And a light receiving optical system arranged in the optical axis direction of the reflected light and receiving the reflected light, and the unevenness of the surface of the inspection object based on the luminance distribution of the reflected light received by the light receiving optical system A surface inspection device for inspecting a surface of the object to be inspected;
On the basis of the inclination angle of the surface of the inspection object detected by the inclination angle detecting means, the light receiving optical system is positioned on the optical axis of the parallel reflected light reflected on the surface of the inspection object.
The surface inspection apparatus is provided with adjusting means for adjusting an incident angle of light from the light projecting optical system to the surface of the inspection object and / or a position of the light receiving optical system. Therefore, even if the inspection object is installed in a state inclined with respect to the inspection device, the unevenness state of the inspection object surface can be inspected accurately and stably. Further, when adjusting the incident angle of light from the light projecting optical system to the surface of the inspection object, the adjusting means can be configured to move the position of a light source constituting the light projecting optical system, for example. But,
If a plurality of light sources constituting the light projecting optical system are provided and the adjusting means selects one from the plurality of light sources, the movement of the light sources does not involve a mechanical operation, so that higher-speed processing is possible. Becomes possible. Further, if the inclination angle detecting means detects the distance to the surface of the inspection object at a plurality of positions and detects the inclination angle based on the detection result, non-contact measurement is possible. is there.

[Brief description of the drawings]

FIG. 1 shows a surface inspection apparatus A1 according to an embodiment of the present invention.
FIG. 2 is a schematic diagram showing a schematic configuration of FIG.

FIG. 2 is a view showing an example of a moving stage 10;

FIG. 3 is a diagram showing an example of a point light source array 10 '.

FIG. 4 is a schematic diagram showing a schematic configuration of a surface inspection apparatus A2 according to an embodiment of the present invention.

FIG. 5 is a schematic diagram showing a schematic configuration of a conventional surface inspection apparatus A0.

FIG. 6 is an explanatory diagram showing reflection characteristics of light from the surface of the inspection object.

FIG. 7 is an explanatory diagram showing the operation principle of the surface inspection apparatus A0.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Point light source 2, 4, 6 ... Lens 3 ... Half mirror 5 ... Pinhole 7 ... Light receiving surface 8a, 8b ... Gap sensor (an example of an inclination angle detection means) 9 ... Control part 10 ... Moving stage 10 '... Point light source Array P: Inspection object surface

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Sadaharu Baba 15 Kinuigaoka, Moka City, Tochigi Prefecture Kobe Steel Moka Works Co., Ltd. Kobe Steel Moka Works

Claims (5)

[Claims] A light projecting optical system for projecting parallel light onto a surface of the inspection object; and a light projecting from the light projecting optical system and arranged in an optical axis direction of reflected light reflected by the surface of the inspection object. A light receiving optical system for receiving the reflected light, wherein the surface inspection device inspects the unevenness of the surface of the inspection object based on a luminance distribution of the reflected light received by the light receiving optical system. An inclination angle detecting means for detecting an inclination angle of the surface of the object from a predetermined direction, and a parallel light reflected on the surface of the inspection object based on the inclination angle of the surface of the inspection object detected by the inclination angle detecting means. Adjusting means for adjusting an incident angle of light from the light projecting optical system to the surface of the inspection object and / or a position of the light receiving optical system so that the light receiving optical system is positioned on the optical axis of the reflected light. A surface inspection device characterized by comprising: 2. The surface inspection apparatus according to claim 1, wherein said adjusting means moves a position of a light source constituting said light projecting optical system. 3. A surface inspection apparatus according to claim 1, wherein a plurality of light sources constituting said light projecting optical system are provided, and said adjusting means selects one of said plurality of light sources. 4. The surface inspection apparatus according to claim 1, wherein said adjusting means adjusts an angle of a mirror constituting said light projecting optical system. 5. The apparatus according to claim 1, wherein the inclination angle detecting means detects a distance from the surface of the inspection object at a plurality of positions, and detects the inclination angle based on the detection result. Surface inspection equipment.