JPS59218420A - Laser beam scanning optical system - Google Patents

Abstract

PURPOSE:To measure a position with a detection signal which is obtained when an image surface is scanned, by providing a marker, which scatters or absorbs a laser beam, and a photodetector which detects the reflected light from the marker. CONSTITUTION:When an image surface 6 is scanned with the laser beam, markers 7-1, 7-2, 7-3, 7-4, 7-5, and 7-6 receive the laser beam successively and radiate a scattered light at every reception. A photodetector 8 detects the scattered light radiated from all markers 7-1, 7-2, 7-3, 7-4, 7-5, and 7-6 and generates the detection signal. The relation between a length l from an optical scanner 5 to the image surface 6 and the detection signal of the photodetector 8 is determined unequivocally by the laser beam scanning speed of the optical scanner 5 and positions of markers on the image surface 6.

Description

Detailed Description of the Invention (A) Technical Field of the Invention The present invention relates to a laser beam scanning optical system used in laser printers, laser reading devices, laser processing devices, etc. (B) Technical Background For example, in laser printers, , a laser light source section,
a modulation unit that modulates a laser beam emitted by the laser light source unit according to print data; an optical scanner that repeatedly scans the laser beam modulated in the modulation unit; and a condenser that focuses the laser beam scanned by the optical scanner. an image forming optical system that receives a laser beam focused by the image forming optical system, and an image plane that receives the laser beam focused by the image forming optical system, and forms an electrostatic latent image of the print information on the image plane, The generated electrostatic latent image is developed with toner and then transferred to recording paper and fixed. In order to obtain clear print results, it is best to provide the image surface on the image formation surface obtained by the imaging optical system. In addition, in a laser reading device or laser processing device, correctly placing the object to be read or the workpiece on the imaging plane is a very important problem in improving the reading accuracy or processing accuracy. This is a very important problem, and as the laser beam condensing diameter tends to be reduced in any of the above devices, these problems are becoming particularly important technical issues.

(Q Conventional technology and problems In laser printers, conventionally, image plane positioning N
K depends on the design accuracy and machining accuracy of each part of the laser beam scanning optical system, but as mentioned above, due to the reduction in the laser beam diameter and the accompanying decrease in the depth of focus, this has reached its limit, and this can be improved by fine adjustment. There is a need to increase it.

In addition, in laser reading devices or laser processing devices, a method is used in which the quotient of the table on which the object to be read or the workpiece is placed is preset according to the thickness of the object to be read or the workpiece. ◎ ■Object of the Invention The purpose of the present invention is to easily and easily locate the position where the scanned laser beam is received in a laser printer/laser reading/laser beam scanning optical system. (G) Structure of the Invention The laser beam scanning optical system of the present invention is an optical scanning system that scans a laser beam. an imaging optical system that is provided before, after, or before and after the optical scanner on the laser beam path and focuses the laser beam, and an image that receives the laser beam that is focused by the imaging optical system. a laser beam scanning optical system having a plurality of markers provided at a plurality of predetermined positions on the image plane in a laser beam scanning direction and scattering or absorbing the laser beam, and detecting reflected light of the laser beam at the plurality of markers. Equipped with a photodetector to
The position of the image plane can be measured by the detection signal of the photodetector obtained when the laser beam scans the image plane. Figure 1 shows the configuration of an embodiment in which the present invention is applied to a laser printer or a laser processing device, where l is a light source that emits a laser beam, and 2 is a light source that emits a laser beam. A fixed reflector 3 converts the optical path of the laser beam; 3 an optical modulator converts the laser beam reflected by the fixed reflector 2 into print data or processing data; 4 an optical modulator 3 modulates the laser beam; An imaging optical system that focuses the received laser beam so as to form an image on a predetermined imaging plane; 5 is an optical scanner that repeatedly scans the laser beam that has been focused in the imaging optical system 4; Image planes 7-1, 7-2, 7-3, 7-4, 7-5, and 7-6 are image planes that receive the laser beam that is focused in the image optical system 4 and scanned by the optical scanner 5. Markers 6 are provided at six predetermined positions equally spaced in the laser beam scanning direction and scatter the laser beam; 8 is 6;
Markers 7-1, 7-2 @7-3-7-4, 7-5
and a photodetector for detecting the reflected light of the laser beam at 7-6.

With the above configuration, when the laser beam scans the image plane 6, the markers 7-1, 7-2, 7-37-4 and 7-
5 and 7-6 receive the j@th order laser beam and emit scattered light each time. Therefore, the photodetector 8 detects all the markers 7-1, 7-2-7-37-4, 7-5 and 7-5.
-6 detects the scattered light emitted, and the photodetector 8 generates a detection signal as shown in FIG.

In FIG. 2, the photodetector obtained when the distance t from the optical scanner 5 to the image plane 6 is an appropriate value, that is, when the image plane 6 is provided on the imaging plane of the laser beam. Letting the detection signal of 7 be (a), if t is longer than the appropriate value, the detection signal of photodetector 8 will be as shown in (b), and if t is shorter than the appropriate value, the detection signal of photodetector 8 will be as shown in (b). The detection signal of the device 8 is as shown in (c).

The relationship between the distance t from the optical scanner 5 to the image plane 6 and the detection signal of the photodetector 8 is determined by the laser beam scanning speed by the optical scanner 5 and the markers 7-1 and 7-247 on the image plane 6. 307-
4, 7-5 and 7-6, and therefore, the detection signal from the photodetector 8 obtained when the image plane 6 is scanned by the laser beam determines the distance from the optical scanner 5 to the image plane 6. The distance 11W &/or the position of the image plane can be easily determined.

Also, markers 7-1, 7-2, 7-3-7-4, 7-5
By accurately providing 7-6 and 7-6 at predetermined positions on the edge surface, the position of the image plane 6 can be determined accurately.

In a laser beam scanning optical system used in a link laser reader Δ or a laser processing device, it is possible to easily and accurately measure the position of the light receiving surface that receives the scanned laser beam, and therefore to easily and accurately align the image plane. Can be done accurately0

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention, and FIG. 2 is an explanatory diagram of the embodiment of FIG. 1. In FIG. 1, 4 is an imaging optical system;
5 is an optical scanner, 6 is an image plane, 7-1, 7-2, 7-3, and 7
-4, 7-5, and 7-6 are markers, and 8 is a photodetector.

Claims (1)

[Claims] An optical scanner that scans the laser beam, an Afr optical scanning scanner on the laser beam narrow path, or an imaging optical system that is provided at the back or front and back to focus the laser beam, and a laser beam that is focused by the imaging optical system. a laser beam scanning optical system having an image plane that receives a laser beam, and a plurality of markers provided at a plurality of predetermined positions on the image plane in the laser beam scanning direction to defeat or absorb the laser beam; a photodetector that detects the reflected light of the laser beam, and a detection signal of the photodetector obtained when the laser beam scans the image plane
A laser beam scanning optical system characterized in that the position of an image plane is fixed 1li11.