JPS6275236A - Surface inspection device - Google Patents

Abstract

PURPOSE:To obtain a small-sized and high-performance inspecting device of simple constitution by guiding reflected and diffracted light from the entire scanning area to mask surfaces and eliminating an uninspected area. CONSTITUTION:Laser light outputted by a laser light source 20 is reflected and scanned by a rotary mirror 30 and then scanned on the inspected surface of a rolled steel plate 1. Spherical lenses 40a-40c as converging parts have end parts cut and are joined together on those cut surfaces, and those individual lenses operates as independent lenses having respective focuses, but function as one lens which provides convergence at any position in the direction of a laser scanning range L. Therefore, diffracted light is converged by the spherical lenses 40a-40c and image-formed on the mask surfaces 50a-50c wherever it is reflected in the scanning range L. Then, images of respective small image- formation areas are put together by optical fibers 81-83 arranged opposite behind the surfaces 50a-50c, converted 61-63 photoelectrically, and supplied to signal processing circuits 71-73, which perform signal processing required to discriminate the reflection and diffraction pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in a surface inspection apparatus for inspecting the surface of a plate or the like using a laser diffraction pattern method.

[Technical background of the invention]

Conventionally, as an example of this type of apparatus, there is one shown in FIG. 3, for example. This device reflects the laser beams output from a plurality of (three in the figure) laser light sources 2a, 2b, and 2c, respectively, on rotating mirrors 3a, 3b, and 3c'Q to detect an object to be detected, for example, a rolled m temporary 1. Scan over the surface. And these scanning ranges La.

Each of the reflected and diffracted lights at Lb and Lc is transmitted through a spherical lens 4a.
, 4b and 4c to focus the light onto the mask surface 5a.

5b and 5c, and these mask surfaces 5
A plurality of photoelectric converters 6a, 6b are arranged to face each other in predetermined imaging small areas a, 5b, 5c.

6C detects the above image formation and sends the detection signal to each signal processing circuit. a, 7b, and 7c. The signal processing circuits 7a, 7b, and 7c perform predetermined signal processing to detect a reflected diffraction pattern, and the surface condition of the rolled steel plate 1 is determined from the detection results.

In addition, the mask surface 5a of each of the photoelectric converters 6a, 6b, 6c
, 5b.

Opposing positions to 5C are mask surfaces 5a and 5b.

It is set according to the shape of the reflection diffraction pattern imaged on 5C. For example, if there are no scratches on the surface of the rolled steel plate 1, the reflected diffraction pattern will be concentrated in the center of the mask surface, as shown in FIG. For example, the photoelectric converters 6a, 6b, and 6c are elongated as shown in FIG. 4(b), so in order to detect them, each photoelectric converter 6a, 6b, and 6c is connected to the broken line 5 in FIG. 4(a), (b).
It is only necessary to position it so that the imaging of the small imaging area shown in 1.52.53 can be detected.

If such a device is used, by setting the scanning repetition rate of each laser beam higher than the conveyance speed of the rolled steel plate 1, the existence and type of scratches on the surface of the rolled steel plate 1 can be uniformly and accurately detected. It is extremely useful.

[Problems with background technology]

However, in such a conventional device, a spherical lens 4a is provided for each scanning range La, Lb, and Lc of the laser beam on the surface to be inspected.
, 4b, and 4c are individually provided to collect the reflected and diffracted light, each spherical lens must collect not only the specularly reflected light but also the diffusely reflected light as shown in FIG. 5, for example. , therefore, a length longer than the scanning ranges La, Lb, and Lc is required. Therefore, the scanning range that can be focused by each spherical lens 4a, 4b, 4c is naturally limited to a range smaller than the size of the spherical lens, and as a result, as shown in FIG. 5, each scanning range La, Lb The region W in between cannot be inspected even if it is scanned with a laser beam, and this has the disadvantage that an uninspected region occurs on the surface to be inspected. Further, it has been considered to provide two inspection devices in order to eliminate the above-mentioned non-inspection area, but this has the disadvantage that the device becomes extremely large and expensive, and is not suitable for practical use.

[Purpose of the invention]

The present invention eliminates uninspected areas by guiding the reflected and diffracted light of the entire scanning area to the mask surface, and also enables this to be done with a single device without using multiple devices. The purpose of the present invention is to provide a surface inspection device that is simple, compact, and has high inspection performance.

[Summary of the invention]

In order to achieve the above object, the present invention provides a plurality of light beams arranged between the spot light scanning position of the surface to be inspected and the mask surface with their ends in line contact with each other in the scanning direction of the spot light. A condensing optical system with a spherical lens is interposed,
The above-mentioned spherical lenses condense reflected diffraction light from the entire scanning range of the surface to be inspected, and form a stationary image on each corresponding mask surface.

[Embodiments of the invention]

FIG. 1 shows the configuration of a surface inspection apparatus according to an embodiment of the present invention, and 20 indicates a laser light source. The laser light output from this laser light source 20 is transmitted to the rotating mirror 3
After being reflected and scanned at 0, it is reflected by the plane mirror 32 and the concave mirror 33 and scanned onto the surface to be inspected of the rolled steel plate 1. Note that L indicates the scanning range of the laser beam, and the figure shows the case where the entire width of the rolled steel plate 1 is scanned.

On the other hand, diagonally above the scanning range of the rolled steel plate 1, there is a spherical lens 40a as a condensing optical system.

40b, 40c and mask surfaces 50a, 50b.

50C are arranged respectively. Of these, each of the spherical lenses 40a, 40b, and 40c is made by cutting both ends in the scanning direction of laser light at a predetermined position, and using the cut surfaces as joints, adjacent lenses are joined and integrated. , the reflected and diffracted light from the entire scanning range of the surface to be inspected is focused without exception to the corresponding mask surfaces 50a, 50b, 50c.
to form an image. These mask surfaces 50a, 50b, 50
On the back side of C, the light introduction ends of optical fibers 81, 82, 83 are disposed opposite to each other in preset imaging small areas, and these optical fibers 81, 82, 83 are arranged to face each mask surface 50a. .
guided by. Each of the above images is formed by each photoelectric converter 6.
After photoelectric conversion at 1.62°63, the signal processing circuit 71
72 and 73, and these circuits perform the signal processing necessary to identify the reflected diffraction pattern.

With such a configuration, when the surface to be inspected of the rolled steel plate 1 is scanned with laser light by the projection optical system, the reflected light is diffracted on the surface to be inspected depending on the surface condition, and this reflected diffracted light corresponds to the spherical lens 40 according to its reflection position.
The light is focused on the mask surfaces 50a, 50b, 50c as a reflection diffraction pattern. At this time, the spherical lens 4
The distance between 0a, 40b, 40c and the laser scanning range on the surface to be inspected and the spherical lenses 40a, 40b
, 40c and the mask surface 50a.

The distance between 50b and 50c is spherical lens 4, respectively.
The focal lengths are set to 0a, 40b, and 40c. Therefore, the reflected diffraction light generated by the surface to be inspected is imaged as a static diffraction pattern on each mask surface 50a, 50b, 50c.

By the way, the above-mentioned spherical lenses 40a and 40 as light condensing parts
b and 40c have their ends cut off and joined together at the cut surfaces, as described above. For this reason, the spherical lenses 40a, 40b.

Each of the lenses 40c acts as an independent lens having a focal point, but it acts as a single lens having a condensing effect at any position in the direction of the laser scanning range. Therefore, the diffracted light reflected within the laser scanning range is always reflected by the spherical lens 40a, no matter where it is reflected within the scanning range.
40 b and 40 c are focused on the mask surface 50 a
, 50 b, and 50 c.

Figure 2 shows this situation. Furthermore, in this apparatus, depending on the position within the scanning range, the mask surface on which the reflected and diffracted light is focused may be different from that of the conventional mask. For example, the diffracted light reflected at any point P in the scanning range ■
1 is a spherical lens 4a as shown in FIG.
In the apparatus of this embodiment, the light is focused by a spherical lens 40b and focused at an image position Pb' on the mask surface 50b, as shown in FIG. 2. is imaged. However, even if the mask surfaces on which the images are formed differ in this way, the image formation positions on the mask surfaces are the same, and the images are grouped together by an optical fiber and are ultimately photoelectrically converted by a common photoelectric converter. So,
Similar problems will not occur.

As described above, with the apparatus of this embodiment, even when scanning the entire width of the surface to be inspected, all of the diffracted light reflected over the entire width is reflected by the spherical lens 40a.

The light is focused by 40b and 40c onto the mask surface 50a.

50b and 50C, and as a result, it is possible to inspect the entire range of the surface to be inspected by preparing one device, making it possible to perform high-capacity inspection with a simple configuration. I can do it. Furthermore, in this embodiment, each spherical lens 4
Since 0a, 40b, and 40c are bonded together and integrated, it is easy to align them with respect to the surface to be inspected, and the lenses do not shift relative to each other due to vibrations, which increases reliability. It can also provide a simple device with a high mounting structure.

Note that the present invention is not limited to the above embodiments. For example, spherical lenses may be mounted by simply contacting them without bonding them together. Further, the projection optical system includes a set of laser light sources 20. In addition to the configuration using the rotating mirror 30 and the reflective optical system, a configuration may be adopted in which scanning is performed using a plurality of sets of laser light sources and rotating mirrors, as shown in FIG. Furthermore, as for the light receiving detection section, in addition to the one that uses a photoelectric converter to collectively detect the images of a small imaging area common to each mask surface, a photoelectric converter is installed for each mask surface as shown in Figure 3. It may also be configured to be provided and detected. others,
The shape, size, number of spherical lenses, bonding means, etc. of the spherical lenses can be modified in various ways without departing from the gist of the present invention.

〔Effect of the invention〕

As described in detail above, according to the present invention, a plurality of light beams are arranged between the spot light scanning position of the surface to be inspected and the mask surface with their ends in line contact with each other in the scanning direction of the spot light. A condensing optical system having spherical lenses is interposed, and the reflected and diffracted light from the entire scanning range of the inspection surface is condensed by each of the spherical lenses, and a static image is formed on each corresponding mask surface. , it is possible to guide all the reflected and diffracted light from the entire scanning area to the mask surface, thereby eliminating uninspected areas, and this can be done with one device without using multiple devices, and the configuration is simple. Moreover, it is possible to provide a surface inspection device that is small and has high inspection performance.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the configuration of a surface inspection device according to an embodiment of the present invention, FIG. 2 is a schematic diagram showing the passing position of reflected diffracted light with respect to a spherical lens used to explain the operation of the device, and FIG. The figure is a perspective view showing the configuration of a conventional surface inspection device.
4(a) and 4(b) are enlarged views showing an example of the position of the reflection diffraction pattern and the imaging small area on the mask surface;
The figure is a schematic diagram showing the passage position of reflected diffracted light with respect to a spherical lens of a conventional device. 1... Rolled steel plate, 20... Laser light source, 30...
Rotating mirror, 32... Plane mirror, 33... Concave mirror, 4
0a94Qb, 40C-' spherical lens, 50a, 50b
. 50c...Mask surface, 61,62.63...Photoelectric converter, 71,72.73...Signal processing circuit, 81°8
2.83...Optical fiber, L...Scanning range. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 2 Figure 3!0 (a) (b) Figure 4 Figure 5 Procedural amendment May 8, 1985

Claims (2)

[Claims] (1) It has a projection optical system that scans a spot light on the surface to be inspected of an object to be inspected, and a plurality of spherical lenses arranged with their ends in line contact with each other in the scanning direction of the spot light. and a condensing optical system that condenses the reflected diffraction light from the entire scanning range of the surface to be inspected using these spherical lenses and forms an image on the corresponding mask surface, and a preset imaging aperture for each of the mask surfaces. A surface inspection characterized by comprising: a light reception detection section that extracts an image of an area and detects it with a photoelectric converter; and a signal processing circuit that processes a predetermined signal by introducing the detection output of the photoelectric converter. Device. (2) Each spherical lens of the condensing optical system is formed by cutting the end portion of the spot light in the scanning direction at a predetermined position, and joining the cut surfaces together as a bonding surface to integrate them. The surface inspection device described in (1).