JPS6353493B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a surface defect detection device for optically detecting defects in the raceway surface of a rolling element of an object having a spherical or arcuate rotating surface with a relatively large radius of curvature, such as a spherical or spherical roller bearing. Regarding.

Various devices have been proposed for detecting surface defects on objects, such as in Japanese Patent Application Laid-Open No. 52-150091, but all of these conventional devices detect surface defects such as cylindrical or flat surfaces. However, it is not suitable for detecting surface defects such as rolling elements of spherical or spherical roller bearings and their raceway surfaces. This is because when illuminating a spherical surface or a rotating arc surface with a simple parallel light beam, the reflected light from the surface to be inspected becomes a diffused light beam, and only a small portion of the reflected light beam from the surface to be inspected is received by the imaging lens. Therefore, only a real image of a small portion of the surface to be inspected could be obtained. As a result, it could not be applied to a test object having a spherical surface or an arcuate surface of rotation.

The purpose of this invention is to enable the detection of surface defects on objects with spherical surfaces or arcuate surfaces of rotation with a relatively large radius of curvature. This relates to the area of

To explain an example, in FIG.
Reference numeral 1 denotes a lamp filament, which is equipped with a reflecting mirror 2 having an elliptical concave surface on its back surface, and a limiting plate 4 having a circular slit 3 is disposed at the position where the lamp filament 1 is imaged by the reflecting mirror 2. A light source section is configured by disposing a diffuser plate 5 on the light source 3. A half mirror 6 and a first lens 7 are arranged on the optical path of the light source to illuminate the test surface 9 of the test object 8 having a spherical surface or a circular arc rotation surface.
The circular slit 3, the first lens 7, and the test object 8 are arranged so that the light source, that is, the image 3' of the circular slit 3 is formed at the center of curvature O of the test surface 9, which is a spherical surface or a surface of circular rotation. do.

The reflected light from the surface to be inspected 9 that is emitted from the first lens 7 is reflected sideways in the right angle direction by the half mirror 6, and a second lens 10 whose optical axis coincides with the optical axis is disposed on the optical path of the half mirror 6. A surface image of the object to be inspected 8 is formed by a composite lens system consisting of the first and second lenses 7 and 10 on an image scanning device 11 that includes a photoelectric conversion device. In the figure, r is the radius of curvature of the surface 9 to be inspected.

In the case of FIG. 1, the lens 7 and the test object 8 are arranged so that the test surface 9 is located at the focal position of the first lens 7, and the first lens 7 and the second lens 10 are arranged as follows.
As shown in FIG. 3, the rear focal point of the first lens 7
Although the front focus F ₁ of the second lens 10 is made to coincide with F ₀ ′, this condition is not necessarily required, and the object 8 to be examined is rotated about its axis by a rotation device (not shown). However, since this point is not the gist of the present invention, its explanation will be omitted.

To simplify the explanation, a case where the light source (circular slit) is a point light source P as shown in FIG. 2 will now be described.

The light emitted from the point light source P is corrected by the first lens 7 and becomes a light beam that forms a point light source image on the center of curvature O of the surface to be inspected 9 . In this case, this illumination light flux becomes a light flux along the normal line of the surface to be examined 9, and thus enters the subject 9 perpendicularly. Therefore, the light beam reflected by the surface to be inspected 9 also becomes a light beam along the normal line and enters the first lens 7, and the emitted light is passed through the half mirror 6 to the second lens disposed laterally in the right angle direction. 10 and forms an image on the front surface of the image scanning device 11.

On the other hand, the imaging rule when two lenses are combined is given by the following equation.

Z ₁ ′=f ₁ ² z ₀ /f ₀ ² +CZ ₀ ... Here, Z ₀ ; Distance between the object point and the front focal point of the objective lens Z ₁ ′; Image point and the rear focal point of the imaging lens distance C; distance f ₀ between the rear focus of the objective lens and the front focus of the imaging lens; focal length f ₁ of the objective lens; focal length of the imaging lens. By the way, in the embodiment shown in FIG. , as shown in Figure 3, Z ₀ in the equation is O, so Z ₁ '=O
becomes. That is, an image 9' of the surface to be examined 9 is formed at the rear focal position of the imaging lens (second lens). Note that in this case, since the surface to be inspected 9 has a relatively large radius of curvature r, blurring of a point image on the surface to be inspected 9 that is distant from the optical axis does not pose a problem.

In Fig. 3, F ₀ ; Front focal position F ₀ ' of the first lens (objective lens); Back focal position F ₁ of the first lens; Front focal position F of the second lens (imaging lens). ₁ ′; Rear focal point position of the second lens H ₀ ; Front principal point position of the first lens H ₀ ′; Rear principal point position of the first lens H ₁ ; Front principal point position of the second lens H ₁ ′; Indicates the position of the rear principal point of the second lens.

4 and 5 are diagrams showing other embodiments, in which a condenser lens 12 is arranged between the circular slit 3 and the first lens 7, and the condenser lens 12 is positioned at the front focal point of the condenser lens 12. A circular slit 3 is arranged so that the focal position of the first lens 7 coincides with the center of curvature of the surface to be inspected 9. At this time as well, the condensing lens 12 and the first lens 7 operate according to the formula, so that a circular slit image 3' is formed at the center of curvature O of the surface to be measured 9, as in the previous embodiment.

Further, the arrangement of the first lens 7 and the second lens 10 is the same as in the embodiment described above, and the imaging law is established according to the above-mentioned formula. Figure 5 shows C= in the formula
O, f ₀ = f ₁ = f, and in this case, the image ₉ ' of the surface to be inspected is r
It can be done at a distance of

In reality, the light source is not a point but a circle of a certain size as shown by the circular slit 3, so a certain point on the test surface is illuminated by the light flux represented by the cone abcdeA as shown in Figure 6a and b. , the light source image 3' becomes circular as shown by a'b'c'd'e', but there is no essential difference in the operation of the optical system.

FIGS. 7 and 8 show the case where the above-mentioned apparatus is applied to a test surface 9 consisting of a concave curved surface, and a light source image 3' is formed at the center of curvature O of the concave curved surface with a curvature r by the first lens 7. In this case as well, the image 9' of the surface to be inspected can be formed at a position a distance r forward from the rear focal position F ₁ ' of the second lens 10, as described above.

As detailed above, according to the present invention, the following excellent effects can be obtained, and it is possible to optically detect defects on the surface of an object having a spherical surface or a surface of circular rotation with a relatively large radius of curvature. A possible surface defect detection device can be provided.

(1) An illumination system for illuminating a surface of an object to be inspected having a spherical surface or a surface of circular rotation, comprising a light source and a first lens disposed on an optical path between the light source and the object to be inspected; The light source, the first lens, and the test object are arranged so that the light source image of the light source is focused on the center of curvature of the test object surface, so that the illumination light flux from the light source and the illumination light flux All of the reflected light beams from the surface of the object to be inspected (test surface) become light beams along the normal line of the test surface, and the reflected light beams from the entire surface to be inspected are sent to the second lens, which is an imaging lens. It can be made incident.

In other words, when a spherical test surface is illuminated with a parallel light flux like the illumination light flux in a conventional device of this type, the reflected light flux becomes a light flux that is emitted from the focal position of the test surface. If the object surface is illuminated from vertically above the center of the object surface, the light reflected only from the center of the object surface located at the center of the optical axis will be incident on the imaging lens, and the light reflected from other peripheral areas will be illuminated. does not enter the imaging lens.
As a result, images of the other peripheral areas cannot be formed, and only the central part of the surface to be inspected is formed as a bright image. In other words, only a portion of the image around the center of the surface to be inspected whose surroundings are darkened is formed.

In contrast, in the present invention, since the illumination light flux from the light source illuminates the test surface from the normal direction thereof, the light flux reflected from the entire test surface by this illumination light flux is incident on the second lens. can be done. As a result, the incident light flux will be along the normal line no matter where in the test image, and as a result, the image of the periphery of the test surface may be missing, or there may be a difference in brightness between the center and the periphery. By connecting a sharp image to be inspected to the front surface of the image scanning device, high defect detection accuracy can be ensured by the scanning device having a photoelectric conversion device.

(2) The imaging system that forms an image of the surface of the object is the first
and a second lens, and the second lens is arranged so that its optical axis coincides with the optical axis of the light emitted from the first lens. Since the illumination system and the imaging system are placed on the same side with respect to the object to be inspected, the optical system of the apparatus can be made very compact.

(3) Furthermore, since the optical system consisting of the illumination system and the imaging system is arranged on the same side with respect to the test object, it is possible to provide a mechanism for rotating the test object, etc. The configuration can be such that an optimum inspection position can be taken depending on the shape of the object to be inspected.

That is, when automating this type of apparatus, mechanical parts such as an operating mechanism for the object to be inspected and a rotation mechanism for inspecting the entire circumference of the object to be inspected, such as a spherical object, are essential. When considering the arrangement of this mechanism (mechanical system) and the optical system, if the optical system is arranged on the same side with respect to the object as in the present invention, the position of the optical system is limited. This allows the mechanism section to be placed at an optimal position, which is very advantageous in terms of the overall configuration of the device.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the configuration of the embodiment, Figures 2 and 3.
The figure is an explanatory diagram of the operation, FIG. 4 is a diagram showing the configuration of another embodiment, FIG. 5 is an explanatory diagram of the operation, FIGS. It is an explanatory view showing still another embodiment. 1...Lamp filament, 2...Oval concave reflector, 3...Circular slit, 5...Diffusion plate, 6
...Half mirror, 7...First lens, 8...
Test object, 9...Test surface, 10...Second lens,
11... Image scanning device.

Claims (1)

[Scope of Claims] 1. An apparatus for detecting defects on the surface of an object to be inspected having a spherical surface or a surface of circular rotation, wherein an illumination system that illuminates the surface of the object to be inspected includes a light source and a light source connected to the object to be inspected. and a first lens disposed on an optical path between the light source, the first lens, and the test object such that a light source image of the light source is formed on the center of curvature of the test object surface. The imaging system for forming an image of the surface of the object includes a composite lens system having the first lens and the second lens, the second lens having an optical axis thereof An apparatus for detecting surface defects on an object, wherein the first lens is arranged so as to coincide with the optical axis of the emitted light from the first lens. 2. The surface of claim 1, wherein the light source comprises a lamp filament, an elliptical concave mirror placed on the back side of the lamp filament, and a circular slit placed at the image position of the lamp filament by the elliptical concave mirror. Defect detection equipment. 3. Claim 1, wherein the light emitted from the first lens is reflected in a direction oblique to the optical axis of the light source by a half mirror disposed on an optical path between the light source and the first lens. The surface defect detection device described.