JPS6253768B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical inspection method suitable for a continuous plate material such as a veneer veneer wound from a rotary race.

Recently, an inspection method has been used in which a monochromatic light beam from a gas laser is scanned across a plate material to detect color defects and uneven dyeing in the material, but this method detects changes in the received light signal level due to changes in the chromaticity of the defect. There is a drawback that it is not possible to distinguish whether it is caused by an object or by unevenness. In view of the above points, the present invention uses a single optical system to eliminate uneven defects such as knots, insect holes, and chips in board materials, color defects such as bluing, reddish, and uneven dyeing, cracks, uneven thickness, and yellowing. The purpose is to simultaneously detect thickness or density defects such as streaks or pores that cannot be detected with reflected light, and to distinguish and classify these defects.

The method of the present invention will be explained in detail below using examples.
In FIG. 1, numeral 1 is a projector main body, which is designed to move back and forth in the direction of arrow A, and 2 is a holding arm for moving the projector. 3 is a board material such as a plywood veneer, which is conveyed in the direction of arrow B. 4 is an optical filter for scattered light, 5 is an optical filter for specularly reflected light, 6 is a light receiving box for both scattered light and specularly reflected light, 7 is a light receiving box for transmitted light, and 8 and 9 are each light receiving box. This is a semi-transparent light scattering plate attached to the light receiving surface of the sensor. FIG. 2 shows a slender reflecting mirror 10 provided inside the projector main body 1, with the projector main body 1 and light receiving boxes 6, 7 of FIG. 1 omitted. It also moves in the direction of arrow A. In Figure 2, 11 is
A He-Ne laser generates a red monochromatic beam, 1
2 is an Ar ion laser that generates blue and green monochromatic beams. Each laser beam is combined by dichroic mirrors 13 and 14, and collimator 1
5, is vibrated radially by a rotating mirror 16, and is converted into a scanning beam that is translated in a horizontal plane by a parabolic mirror 17.As shown in FIG. slit 1
8, and is further irradiated onto the surface of the plate material 3 by a reflecting mirror 10 arranged diagonally. In this way, the scanning beam is vibrated by the rotating mirror 16 and reflected by the reflecting mirror 1.
It is scanned in both the vertical and horizontal directions by the reciprocating movement of zero. In FIG. 3, from the point of incidence of the scanning beam on the surface of the plate material, that is, from the irradiation spot, specularly reflected light b heads toward a filter 5 for specularly reflected light, and scattered light a
is directed toward the filter 4 for scattered light. The filter 4 for scattered light is provided in a substantially normal direction, that is, substantially vertically upward, when viewed from the incident point, and the filter 5 for regular reflection light is provided in a direction symmetrical to the incident light with respect to the normal. That is, in the figure, the angle θ ₁
and θ ₂ have the same magnitude. When a scanning beam is applied to the surface of a plate, part of the beam is reflected by the surface, and part of the beam vibrates microparticles, such as atoms and molecules, on the surface.
After specific spectral components are absorbed, they are emitted to the outside as scattered light, some of which is absorbed by the plate, and the rest of the light is transmitted through the plate. As mentioned above, scattered light with colorimetric properties can be received most efficiently in the normal direction. It was placed in On the other hand, the light reflected from the surface, that is, the specularly reflected light, naturally does not have colorimetric properties.
By receiving this light in the direction of the regular reflection angle, it is possible to detect changes in gloss on the surface of the plate material, that is, irregularities defects. In FIG. 3, each of the above filters 4,
5 is provided with a hood 19 to prevent specularly reflected light and scattered light from mixing. The scattered light filter 4 transmits red and green, the regular reflection light filter 5 transmits blue, and each transmitted light enters the light scattering plate 8 of the dual-purpose light receiving box 6. Inside the dual-purpose light receiving box 6, there are as many photoelectric conversion elements 20, 21, and 22 as there are monochromatic lights combined in the scanning beam, and red, green, and blue filters 23, 2 are arranged on each photocathode, respectively.
4,25 are installed. Light scattering plate 8
This is to ensure that a constant amount of light is always incident on the photoelectric conversion element even if the irradiation spot moves. The light c transmitted through the plate material is evenly scattered in all directions by the light scattering plate 9 of the light receiving box 7, and is received by the photoelectric conversion element 26 for transmitted light. FIG. 4 is a schematic block diagram of the signal processing system, in which the output signals of the red, green, and blue photoelectric conversion elements 20, 21, and 22 and the transmitted light photoelectric conversion element 26 are preprocessed. After being waveform-shaped by the circuit 27, it enters the defect classification circuit 28 where it is classified as various defects, and then comprehensively judged by the pass/fail level setting circuit to select defective products. In this embodiment, in order to simplify the structure of the light receiver, a dual-purpose light receiving box 6 equipped with a light scattering plate 8 is used.
For example, a scattered light receiver and a specularly reflected light receiver may be separately provided inside the projector body 1, and the projector body 1 may have as many photoelectric conversion elements as the number of monochromatic lights. The plate material 3 may be conveyed in the direction of arrow A while being fixed.

As described above, in the present invention, light receivers are arranged in the specular reflection direction and the normal direction for one light beam, and the specular reflection light is used to inspect uneven defects and the scattered light is used to inspect color defects. Therefore, when inspecting continuous plate materials, the reflecting mirror can be moved in parallel to scan with incident light parallel to the fiber direction of the plate material, and noise components due to conduit grooves can be removed, and the structure is extremely simple. This method has the advantage that uneven defects and color defects can be detected separately.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, in which Fig. 1 is a partially cutaway perspective view, Fig. 2 is a partially omitted schematic perspective view, Fig. 3 is a sectional view of the main part, and Fig. 4 is a main part. FIG. 2 is a schematic block diagram. 3...Plate material, 4...Scattered light filter, 5...
Specular reflection filter, 6... Light receiving box for both scattered light and reflected light, 8... Light scattering plate, 20... Photoelectric conversion element for red, 21... Photoelectric conversion element for green, 2
2... Blue photoelectric conversion element, 23... Red filter,
24... Green filter, 25... Blue filter, a...
...scattered light, b... specularly reflected light, c... transmitted light.

Claims (1)

[Claims] 1. A light beam irradiated parallel to the surface of a plate is made obliquely incident on the surface of the plate by a reflecting mirror that travels back and forth in a direction perpendicular to the direction of conveyance of the plate, and is directed in the normal direction as seen from the point of incidence. A light receiver for detecting color that receives scattered light is provided, and a light receiver for detecting irregularities that receives specularly reflected light in a direction symmetrical to the incident light with respect to the normal is provided. A method for inspecting plate materials characterized by simultaneously detecting color defects and unevenness defects. 2. A method for inspecting a plate material according to claim 1, characterized in that a light receiver for receiving transmitted light is disposed on the back side of the plate material to simultaneously detect defects such as cracks and thickness of the plate material. 3. A light beam is formed by combining two or more types of monochromatic light, and an optical filter that transmits one or more types of monochromatic light in the normal direction is provided, and the remaining monochromatic light is transmitted in the regular reflection direction. An optical filter is provided, and a light receiving box for color detection and unevenness detection is provided above both filters with a translucent light scattering plate as a light receiving surface, and an optical filter that transmits each of the above monochromatic lights is installed in the box. Claim 1 is characterized in that the size and chromaticity of color defects and the size of unevenness defects are determined based on output signals of photoelectric conversion elements respectively arranged behind each filter. Inspection method for board materials.