JPH03223712A - Laser light scanner - Google Patents

Abstract

PURPOSE:To converge laser light into a fine spot by reflecting a parallel light beam which is made incident from the 1st focus of a semi-elliptic sphere by a mirror surface and converging it by an objective lens placed at the 2nd focus. CONSTITUTION:A parallel light source 103 is fixed in position, but freely changed in direction; and the projection point is invariably at the 1st focus and an place on the internal wall of the semi-elliptic sphere can be irradiated with the parallel beam 105. The parallel light beam 105 which is made incident from the 1st focus of the semi-elliptic sphere 101 and reflected by the internal mirror surface passes the 2nd focus without fail because of the characteristics of the focuses of an ellipse, so the objective 107 is arranged at the 2nd focus to converge the light into the fine spot 11 on the surface of a medium 109. When the angle of projection of the parallel light source is varied, the angle of incidence of the parallel light beam on the objective lens also varies, so the spot shift in position on the medium surface. Consequently, a fast random two-dimensional scan with the fine laser spot scan be made.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a laser beam scanning device used in laser-applied equipment such as laser printers, optical disks, and optical cards.

[Conventional technology]

As a conventional laser beam scanning device, a galvano mirror is used.
・There are polygon mirrors, hologram disks, etc.

A common feature of these methods is that scanning is performed after focusing the light beam near the light source.

Therefore, the focal length becomes extremely long, and there is a problem in that the laser beam cannot be narrowed down to a minute spot.

[Problem to be solved by the invention]

In general optical systems, the focal length of a lens and the minimum spot diameter are almost directly proportional, and a lens with a long focal length cannot focus the laser beam into a minute spot.

Conventional laser beam scanning devices all focus the beam near the light source before scanning, so the focal length is extremely long, making it necessary to focus the laser beam into a minute spot. It was impossible to scan the image while it was still there.

Therefore, it could not be used for optical disks, optical cards, and other devices that require a minute spot on the surface of the medium.

[Means to solve the problem]

Parallel light rays enter from the first focal point of a semi-ellipsoid with a mirrored interior, are reflected by the mirrored surface, and are focused by an objective lens placed at the second focal point. In other words, the objective lens does not need to be placed near the light source and can be placed close to the medium surface.
A lens with a short focal length can be used, so the spot can be made very small. By changing the direction of the incident light, the angle of the light beam incident on the objective lens changes, so the focal position can be scanned.

〔Example〕

The basic structure of the present invention is shown in FIG.

In Figure 1, 101 is a semi-elliptical sphere with a mirrored inside;
06 is a parallel light source, 105 is a parallel light beam, 107 is an objective lens, and 109 is a medium.

Although the position of the parallel light source 106 does not move, the direction of the parallel light source 106 can be changed freely, and the parallel light source 106 is structured so that the parallel light ray 105 can be irradiated anywhere on the inner wall of the semi-ellipsoid while the emission point remains at the first focal point.

In FIG. 1, a parallel ray 105 that is incident from the first focal point of the semi-elliptical sphere 101 and reflected by the inner mirror surface always passes through the second focal point due to the nature of the focal point of the ellipse.
By arranging the objective lens 107 at the focal point position, it becomes possible to narrow down the minute spora (111C) on the surface of the medium 109.

By changing the emission angle of the parallel light source, the angle of incidence of the parallel light rays on the objective lens also changes, so the spot position on the medium surface moves. For example, if the direction of the parallel rays is changed from solid line 105 to broken line 105', the spot moves to 111'. In other words, by changing the direction of the parallel light source according to external signals,
Two-dimensional random scanning of minute spots on a fixed plane becomes possible.

In this device, the only movable part is the part that changes the direction of the light source, so high-speed scanning is possible.

For the objective lens 107, an aspherical lens or a combination lens corrected for astigmatism and field curvature is used.

In addition to the method of changing the direction of the entire parallel light source as shown in FIG. 1, a method of using a galvano mirror or the like may be considered as a mechanism for the incidence of parallel light rays to the first focal point.

〔Effect of the invention〕

The present invention enables high-speed, undamaged, and
Two-dimensional scanning becomes possible.

By using the present invention in an optical disk/optical card drive device, access time can be shortened.

Further, by using the present invention in a laser printer, it becomes possible to print finer dots.

[Brief explanation of drawings]

FIG. 1 shows the basic structure of the present invention. 101...Semi-elliptical sphere with mirror surface on the inside, 103
...Parallel light source, 105...Parallel rays, 107...Objective lens. 109...Medium, 111...Spot. Figure 1

Claims (1)

[Claims] A semi-elliptical sphere with a mirrored interior, a parallel light source arranged so that the light beam exit point is the first focal point of the semi-elliptic sphere, and whose direction of emission is controlled according to an external signal, and a parallel light source arranged at the second focal point. A laser beam scanning device equipped with an imaging lens system.