JPS6219725B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical scanning device for scanning a subject with a light beam.

Conventionally, various apparatuses for scanning a subject with a light beam are known. In this type of device, for example, as typified by facsimile document reading, the document (subject) is moved at a constant speed (main scanning) while the light beam is sub-scanned in a direction perpendicular to the main scanning direction. Common. Although this scanning method is widely applicable, it has the disadvantage that as the target object becomes larger, the sub-scanning width of the light beam becomes larger, the sub-scanning mechanism becomes significantly more complex, and the required scanning speed cannot be achieved. It was hot. The increase in sub-scanning width also makes it difficult to meet the requirement that the light beam be set to a constant spot size at any position within this scanning width.

The object of the present invention is to provide an improved optical scanning device that eliminates the above-mentioned drawbacks.

According to the present invention, a means for circularly scanning a light beam is used instead of the conventional linear sub-scanning mechanism.

In the embodiments of the present invention described below, the present invention is used in a device for detecting defects in an object to be inspected, but it goes without saying that the present invention can be applied to any feature extraction device or other various devices that utilize scanning of a light beam.

FIG. 1 shows a defect inspection apparatus as an embodiment of the present invention. In the figure, reference numeral 1 indicates an object having a relatively large area, such as a textile.

The subject 1 is conveyed in the direction of arrow A by rollers 2 and 3 at a constant speed. Rotating disks 4 and 5 are arranged opposite the upper and lower surfaces of the subject 1 .
The rotating disks 4 and 5 are kept at a constant distance from the subject 1 by a holding mechanism (not shown), and are rotated in the same direction B at the same speed by pulse motors 6 and 7. Here, the rotational axes of the rotating disks 4 and 5 are aligned. A reflecting mirror 8 is located at the center of the rotating disk 4, and a reflecting mirror 9 and a hole 10 are provided at a certain distance from the center. Reflector 8,
9 is fixed to the rotating disk 4. On the other hand, a reflecting mirror 11 is arranged at a position facing the hole 10 of the rotating disk 5, and a reflecting mirror 12 and a hole 13 are provided at the center. The reflecting mirrors 11 and 12 are fixed to the rotating disk 5.

14 is a laser light source, and its output beam is incident on the reflecting mirror 8 via a collimating lens system 15. This laser beam is further transmitted through a reflecting mirror 9 and a hole 10.
The subject 1 is illuminated through. The transmitted light of the subject 1 passes through the reflecting mirrors 11, 12, and 13 to the lens 16.
incident on .

Here, the subject 1 is placed on the front focal plane of the lens 16 (that is, the transmitted light of the subject 1 is
(the length of the optical path until reaching the focal length f is the focal length f), thereby obtaining a Fourier transform pattern image of the subject 1 on the rear focal plane of the lens 16. Therefore, a filter 1 of an appropriate shape is placed on the back focal plane of this lens 16.
By arranging the light source 7, only the characteristics (defects in this case) of the object 1 are extracted. This light is transferred to the screen 1 using an inverse Fourier transform lens 18.
9, a characteristic pattern of the subject 1 is obtained on the screen 19.

The lens 16, filter 17, inverse Fourier transform lens 18, and screen 19 constitute a defect detection system for the object 1. The details of such a defect detection system are as proposed in Japanese Patent Application No. 31020/1983.
Alternatively, as filter 17, Proceedings of
IEEE pp. 447-448, April 1972 issue. Briefly, defects such as uneven weaving are detected by irradiating coherent light such as a laser beam onto a regularly arranged specimen such as a textile. A filter 17 is provided to extract only this defective portion. The filter 17 blocks the regularly arranged pattern information light and allows only the information light from the defective portion to pass through.

Next, since the reflecting mirror 8 in FIG. 1 rotates together with the rotating disk 4, it has a function as a rotating mirror.
That is, the reflecting mirror 8 converts the laser beam into a rotating beam. This rotating beam is bent by a reflecting mirror 9, creating a circular trajectory on the surface of the subject 1 as shown by a broken line C. In this manner, in this embodiment, the entire surface of the subject 1 is scanned by circular scanning of the laser beam and movement of the subject 1 in a fixed direction. As long as the area of the subject 1 is determined, the subject 1 may be kept stationary and the rotating disks 4, 5, etc. may be shifted.

FIG. 2 shows another embodiment of the invention. In this figure, the same parts as in FIG. 1 are given the same reference numerals, and their explanations will be omitted. A configuration different from that in FIG. 1 is that the laser beam is not perpendicularly incident on the subject 1
A rotating prism 20 is used to circularly scan the laser beam, and a lens 16 serves as a defect detection system.
and that the filter 17 rotates together with the reflecting mirrors 11 and 12. Both the lens 16 and the filter 17 can be provided on the rotating disk 5 shown in FIG. According to this embodiment, the rotating beam generation mechanism is simplified compared to the apparatus shown in FIG.
However, since the laser beam is obliquely incident on the subject, the design of the filter 17 becomes somewhat complicated.
Furthermore, since the filter 17 itself moves in a circular motion, it is desirable to use the omnidirectional spatial filter described in the above-mentioned Japanese Patent Application No. 31020/1983. Omnidirectional spatial filters have symmetrical characteristics with respect to the optical axis, so they are suitable for high-speed scanning systems, and have the advantage of not requiring high alignment accuracy.

Note that in both the embodiments shown in FIGS. 1 and 2, the defect of the object to be inspected is displayed on the screen, but instead of the screen, an ITV camera may be used to capture the image and the image may be displayed on the monitor TV. Furthermore, if only the presence or absence of defects is to be detected, a photoelectric conversion element can be used.

As described above, according to the present invention, it is possible to scan a relatively large area of an object at high speed with a simple configuration.
It can be widely used for feature extraction, etc.

FIG. 3 shows a modification of the condensing system used in the embodiment shown in FIG. Here, in the hollow box body 21,
An opening 22 is provided at one end of the upper surface, and an opening 23 is provided at the other end of the lower surface. Additionally, there is a reflecting mirror 24 for guiding the light beam incident from the opening 22 to the other end of the box 21, and a reflecting mirror 24 for supplying the light beam from the reflecting mirror 24 to the outside of the box 21 through the opening 23. A mirror 25 is provided. The box body 21 is rotated in synchronization with the circularly scanned light beam with the center of the aperture 23 as the rotation axis L. Such a condensing system can be used in place of the rotating disk 5 and reflecting mirrors 11 and 12 shown in FIG.

[Brief explanation of the drawing]

FIG. 1 shows one embodiment of the invention, FIG. 2 shows another embodiment of the invention, and FIG. 3 shows a modification of the invention. 1... Subject, 2, 3... Roller, 4, 5... Rotating disc, 6, 7... Pulse motor, 8, 9, 11, 12
...Reflector, 14...Laser light source, 15...Collimating lens system, 16...Lens, 17...Filter, 18
...inverse Fourier transform lens, 19...screen.

Claims (1)

[Scope of Claims] 1. A device for plane-scanning a predetermined area of the subject by relative movement between the subject and the inspection light beam, comprising: a light source that generates the inspection light beam; and an inspection from this light source. a reflecting mirror that irradiates an inspection light beam onto the subject; and a scanning system that rotates at least this reflecting mirror relative to the subject and scans the inspection light beam approximately circularly over the subject. and means;
Repeat circular scanning by this scanning means multiple times,
An optical scanning device characterized in that the predetermined area is scanned in a plane. 2. The scanning means consists of a rotating plate and first and second reflecting mirrors, and the optical path of the inspection light beam supplied from the light source along the central axis of rotation of the rotating plate is controlled by the first reflecting mirror. The optical path of the inspection light beam from the first reflecting mirror is changed to be substantially parallel to the surface of the rotating plate, and the optical path of the inspection light beam from the first reflecting mirror is again made parallel to the rotation center axis.
A passage hole is provided in the rotating disk corresponding to the optical path of the inspection light beam from the second reflecting mirror, and the rotating disk and the first and second reflecting mirrors are further provided integrally. An optical scanning device according to claim 1, characterized in that: