JPS61223605A - Method for inspecting surface shape - Google Patents

Abstract

PURPOSE:To simplify the constitution of an inspecting system and to reduce the cost of inspection by picking up the image of an inspecting plate through the surface of an object to be inspected formed into a specular surface to inspect the surface shape of the object to be inspected. CONSTITUTION:An object 10 to be inspected has a surface 10a formed into a specular surface, and an inspecting plate 12 illuminated by a light source 11 is arranged above this object 10. Lines 12a are recorded at a certain pitch on the lower face of the object 10. The light from the plate 12 is made incident on the surface 10a of the object 10 through an optical path A. the light from the plate 12 is reflected on the surface 10a and passes an optical path B to reach a lens 16. The lens 16 forms the image of the stripe pattern recorded on the plate 12 on the image receiving face of an image pickup device 15. The device 15 converts this image to a video signal and sends it to a picture display device 17 and a picture processor 18. The stripe pattern for the flat surface 10a is stored in the processor, and this pattern is compared with the inputted stripe pattern, and the surface 10a is judged to be rugged if they are different from each other.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a surface shape inspection method for inspecting an object to be inspected whose surface is mirror-like.

[Conventional technology]

As a method for inspecting the surface shape of an object to be inspected, for example, as described on pages 905 to 906 of "Optical Technology Handbook" (published by Asakura Shoten in 1978),
A light cutting method is known in which the surface of an object to be inspected is illuminated in a line and the reflected light is projected onto a screen to inspect the surface irregularities. In this light cutting method, a light source is placed behind a slit plate with an elongated slit, and the slit light transmitted through the slit plate is imaged onto the object to be inspected using a slit projection lens, which is then illuminated in a line. It is something to do.

The reflected light from the object to be inspected illuminated in a line is enlarged and projected onto a screen by a projection lens. If the surface of the object to be inspected is flat, the slit image projected onto the screen will be a straight line; if the surface is uneven, the slit image will be a curved line depending on the degree of unevenness.

In the conventional surface inspection method described above, a high-precision slit projection lens with good aberration correction is required to illuminate the object to be inspected in a line, which complicates the structure of the inspection system and increases costs. There was a problem that it took a while. Furthermore, if the object to be inspected is large, a correspondingly large slit projection lens must be used, which causes an increase in the size of the apparatus.

[Problem that the invention seeks to solve]

An object of the present invention is to provide a surface shape inspection method that does not require a slit projection lens.

Another object of the present invention is to provide a surface shape inspection method that can simplify the configuration of an inspection system and reduce costs.

[Means for solving problems]

Some objects to be inspected have mirror-like surfaces, and the present invention utilizes these mirror-like surfaces for inspection. That is, using an inspection plate with patterns arranged at a constant pitch and an imaging device such as a television camera,
The inspection plate is imaged through the mirror-like surface of the object to be inspected.

If the surface of the object to be inspected has irregularities, the image of the pattern on the inspection plate will be deformed, and by examining the degree of this deformation, the condition of the mirror-like surface can be inspected.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

〔Example〕

In FIG. 1, an object to be inspected 10 has a mirror-like surface 10a and is continuously transported in the direction of the arrow. An inspection plate 12 illuminated by a light source 1) is arranged above the object to be inspected 10. The inspection plate 12 used has a striped pattern corresponding to the unevenness of the surface 10a of the object 10 to be inspected. The inspection plate 12 of this embodiment has lines 12a recorded at a constant pitch on its lower surface using, for example, black paint. TV camera 13
is arranged at an angle so as to image the inspection plate 12 through the surface 10a of the object 10 to be inspected. As is well known, the television camera 13 includes an imaging device 15 inside a camera body 14, and a lens 16 attached to the front surface.

When inspecting the object to be inspected 10, the focus is adjusted so that the lens 16 focuses on the inspection plate 12 located at the object point distance (A+B). The light from the inspection plate 12 passes through the optical path A and is incident on the surface 10a of the object to be inspected 10 at an incident angle α.

Here, if the length of the optical path A is increased, the pitch of the striped pattern image formed on the imaging device 15 becomes smaller, and the detection sensitivity also decreases accordingly. This object to be inspected 10 has a mirror-like surface 10a, so the inspection plate 12
The light from the lens is reflected by the surface 10a at a reflection angle α and reaches the lens 16 through the optical path B. This lens 16 is
The striped pattern recorded on the inspection plate 12 is captured by the imaging device 15.
The image is formed on the image receiving surface. Note that the angle α is set to a value that provides the best detection sensitivity.

The imaging device 15 converts the striped pattern image into a video signal, outputs it, and sends it to an image display device 17 and an image processing device 18. This image display device 17 reproduces a video signal and displays a striped pattern on a CRT screen. The image processing device 18 stores the striped pattern when the surface 10a is flat and normal, compares it with the inputted striped pattern, detects the presence or absence of a difference, and outputs it. If this difference exists, it means that the surface 10a has irregularities.

FIG. 2 shows an object to be inspected 10 having a convex portion 10b on a mirror-like surface 10a. When such an object to be inspected 10 is imaged by the television camera 13, as shown in FIG.
A disordered striped pattern 2 appears on the CRT display surface of the image display unit 17.
0 is displayed. From this change in the striped pattern 20, the surface 1
The shape of 0a can be inspected. The degree of unevenness of the surface 10a can be determined from the degree of disorder of the striped pattern 20. Although it depends on the inspection system, it is possible to inspect irregularities of about 3 μm.

〔Effect of the invention〕

In the present invention, since the inspection plate on which a regular pattern is recorded is imaged through the mirror-like surface, a slit plate, a slit projection lens, etc. are not required compared to the conventional surface shape inspection method. Therefore, the structure of the inspection system becomes simple and costs can be reduced.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an inspection system implementing the present invention. FIG. 2 is a perspective view showing an inspection plate and an object to be inspected having a convex portion formed on its surface. FIG. 3 is an explanatory diagram showing a state in which the object to be inspected shown in FIG. 2 is imaged and displayed on a CRT. 10...Object to be inspected 10a...Mirror surface 10b...Convex portion 12...Inspection plate 12a...Striped pattern 13...Television camera I5...Imaging device 20...Displayed on CRT Striped pattern. Figure 2 Figure 3

Claims (2)

[Claims] (1) In a method of inspecting the surface shape of a mirror-like object to be inspected, an inspection plate on which a regular pattern is recorded and an imaging device are placed above the object to be inspected, and the surface of the object to be inspected is inspected. A surface shape inspection method characterized in that the surface shape of an object to be inspected is inspected based on changes in the shape of a pattern by imaging an inspection plate through a camera. (2) The surface shape inspection method according to claim 1, wherein striped patterns are recorded on the inspection plate at a predetermined pitch.