JPH0248641A - Laser scanner - Google Patents

Abstract

PURPOSE:To eliminate mechanically movable parts and to perform scanning of high precision by using a fixed mirror having a cylinder mirror surface and deflecting the laser beam, with which this mirror surface is irradiated, in the peripheral direction of the cylinder mirror surface in accordance with the level of a scanning signal by an optical deflecting device. CONSTITUTION:The laser beam irradiating from a cylinder mirror surface 13 is deflected in the peripheral direction of the mirror surface 13 in accordance with the level of the horizontal scanning signal by an A/O optical deflector 11 to change the angle of incidence of the laser beam at respective irradiation points of the mirror surface 13 to smaller values, and therefore, the laser beam reflected on the mirror surface 13 is successively scanned on a display face in the direction of an arrow B, and this scanning is repeated at every period of the horizontal scanning signal. A waveform correcting circuit 14 is provided on the control input side of the deflector 11 to correct the waveform of the horizontal scanning signal, and the laser beam is deflected in accordance with the corrected waveform of the horizontal scanning signal, thereby fixing the scanning speed of the laser beam on the display face.

Description

TECHNICAL FIELD The present invention relates to a laser scanning device, and more particularly to a high-speed laser scanning device such as a laser projector.

Background Art An example of the configuration of a high-speed laser scanning device is shown in FIG. In this figure, the laser light modulated based on the video signal passes through the first cylindrical lens 21 for correcting pitch unevenness of the scanning line and enters the mirror surface of a polygon mirror 22 having, for example, a 25-sided shape. The polygon mirror 22 is used for horizontal deflection,
It is rotated at high speed by a drive motor 23. The laser beam horizontally deflected by the polygon mirror 22 passes through a first relay lens 24 for two-dimensional deflection, a second cylindrical lens 25 for correcting pitch unevenness of the scanning line, and a second relay lens 26 for two-dimensional deflection. Rear galvanometer mirror for vertical deflection
27. The laser beam vertically deflected by the galvano mirror 27 is directed to a screen (
(not shown).

Here, the principle of horizontal scanning when using, for example, a hexahedral polygon mirror will be explained with reference to FIG. While moving from the position shown by the solid line to the 1st position shown by the dashed-dotted line, the inclination angle of the mirror surface P changes moment by moment, so that the laser beam reflected by the mirror surface P sequentially moves along the display surface in the direction of the arrow B. This operation is repeated for each mirror surface of the polygon mirror.

In this high-speed laser scanning device, in the case of NTSC horizontal scanning, scanning must be performed at 945.000 [c, p, s,] for a horizontal scanning frequency of 15.75 [KHz], so the polygon mirror 22 For example, even if a 25-hedron is used, 37.800 [r, p, s, ]
It is necessary to rotate the polygon mirror 22 at extremely high speed. Therefore, a very special bearing such as a dynamic pressure air bearing is required as a bearing for the drive motor 23, and it is also difficult to control the rotation of the motor itself. It is also possible to lower the rotational speed of the drive motor 23 by using a speed increasing mechanism, but if the speed increasing mechanism is configured by a combination of gears, for example, there is a new problem in that it is necessary to eliminate negative effects such as jitter. A problem arises.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned conventional problems by eliminating mechanically movable parts, and to provide a laser scanning device that is capable of scanning with extremely high precision.

In the laser scanning device according to the present invention, a fixed mirror having a cylindrical mirror surface is used, and a laser beam irradiated toward the cylindrical mirror surface is deflected in the circumferential direction of the cylindrical mirror surface by a light deflecting means according to a scanning signal level. It has become.

Example Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

In FIG. 1 showing an embodiment of the present invention, a laser beam passes through a first cylindrical lens 21 in FIG. 3, for example, and enters an acousto-optic (A10) optical deflector 11, which is a light deflecting means. The laser beam that has passed through the A10 optical deflector 11 is irradiated onto the cylindrical mirror surface 13 of the fixed mirror 12, and is reflected by this cylindrical mirror surface 13. The reflected laser light is, for example, 1. in FIG. After passing through the first relay lens 24, the second cylindrical lens 25, and the second relay lens 26,
The image forming lens 2 is deflected vertically by the galvanometer mirror 27.
8 onto a screen (not shown).

The A10 optical deflector 11 uses an acousto-optic effect in which periodic changes in the refractive index are formed in a substance by ultrasonic waves, and the frequency of the ultrasonic waves is changed to change the diffraction angle of the light beam, and the waveform correction circuit is used. The laser beam is deflected in the circumferential direction of the cylindrical mirror surface 13 in accordance with the horizontal scanning signal level supplied via the mirror 14. Note that the A10 optical deflector 11 is used as the optical deflection means.
However, an electro-optical (Elo) optical deflector that utilizes changes in the refractive index of a material due to the application of an electric field may also be used.
Any device that can deflect the laser beam in the circumferential direction of the cylindrical mirror surface 13 according to the horizontal scanning signal level may be used.

Here, the principle of horizontal scanning when using a fixed mirror 12 having a cylindrical mirror surface 13 will be explained with reference to FIG.
The laser beam irradiated onto the cylindrical mirror surface 13 is transmitted through the A10 optical deflector 1
1 in the circumferential direction (for example, direction A) of the cylindrical mirror surface 13 in accordance with the horizontal scanning signal level, the incident angle of the laser beam at each irradiation point on the cylindrical mirror surface 13 changes in the direction of decreasing. The laser beam reflected by the cylindrical mirror surface 13 sequentially scans the display surface in the direction of arrow B, and this operation is repeated every cycle of the horizontal scanning signal. Note that if the deflection angle (range) by the A10 optical deflector 11 is α and the corresponding reflection angle at the cylindrical mirror surface 13 is β, β/α becomes the angle amplification gain.

In this horizontal scanning, the reflective surface of the laser beam is a circle f7im.
Due to the surface 13, the rate of change in the deflection angle of the laser beam is not proportional to the rate of change in the reflection angle, so the A10 optical deflector 1
Even if the deflection speed of the laser beam according to No. 1 is constant, the scanning speed of the laser beam on the display surface will not be constant. For this reason, a waveform correction circuit 14 is provided on the control input side of the A10 optical deflector 11.
The horizontal scanning signal waveform, which should be a sawtooth wave as shown by the broken line in the figure, is corrected as shown by the solid line, and the laser beam is deflected according to the corrected horizontal scanning signal waveform, thereby scanning the laser beam on the display surface. The speed is kept constant. The correction coefficient of the waveform correction circuit 14 is set according to the curvature of the cylindrical mirror surface 13 so that the scanning speed of the laser beam on the display surface is constant.

In the above embodiment, the case where the present invention is applied to a laser projector has been described, but the present invention can be applied not only to a display but also to any device that requires laser scanning, such as a liquid crystal printer.

As described in detail, in the laser scanning device according to the present invention, a fixed mirror having a cylindrical mirror surface is used, and a laser beam irradiated toward the cylindrical mirror surface is deflected into a cylindrical shape according to a scanning signal level by an optical deflection means. Since it is configured to deflect in the circumferential direction of the mirror surface, various problems caused by using a motor as in conventional devices can be solved, and since there are no mechanically moving parts, extremely high precision scanning is possible. Moreover, it is easy to adjust the position of the optical system, etc.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram showing an embodiment of the present invention, Fig. 2 is a diagram for explaining the principle of horizontal scanning when a cylindrical mirror surface is used, and Fig. 3 shows an example of a high-speed laser scanning device. The configuration diagram, FIG. 4, is a diagram for explaining the principle of horizontal scanning when a rotating polygon mirror is used. Explanation of symbols of main parts 11...A10 Optical deflector 13...Cylindrical mirror surface 14...Waveform correction circuit 22...Rotating polygon mirror Applicant Pioneer Co., Ltd. Company agent Patent attorney Motohiko Fujimura d Book 1 Illustrations 11 Book 2 Illustrations Lace book 4 Illustrations

Claims (3)

[Claims] (1) A fixed mirror having a cylindrical mirror surface, irradiation means for irradiating laser light toward the cylindrical mirror surface, and light deflection means for deflecting the laser light in the circumferential direction of the cylindrical mirror surface in accordance with a scanning signal level. A laser scanning device comprising: (2) The laser scanning device according to claim 1, wherein the light deflecting means is an acousto-optic light deflector or an electro-optic light deflector. (3) Claim 1 further comprising a correction means for correcting the scanning signal level according to the curvature of the cylindrical mirror surface.
The laser scanning device described.