JPS63178208A - Laser light scanner - Google Patents

Abstract

PURPOSE:To improve the printing quality by radiating a second laser light to a columnar mirror of a rotary polygon mirror device and deriving an angle deflection of a mirror axis from a deflection of a reflected light, and correcting continuously an angle of a first laser light which is made incident on the device together with an inclination quantity of each reflecting surface of the mirror. CONSTITUTION:From a difference of an optical output corresponding to a rotational angle of an axis of a rotary polygon mirror device 6 and an average values A in its angle, an arithmetic operation is executed by a signal processor 12, and an angle deflection of the axis of the rotary polygon mirror at that time point is derived. Also, in accordance with an angle deflection signal of the axis of the rotary polygon mirror device 6 from the signal processor 12, a deflector 15 is driven, and when an angle of a laser light 16 radiated to the rotary polygon mirror device 6 is changed, a shift of the scanning direction of a scanning line 19 of a photosensitive body 18 and the vertical direction, generated by an angle deflection of the axis of the rotary polygon mirror device 6 can be negated. In such a way, a laser beam printer, etc. can be operated at a high speed, and a high printing quality can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a laser beam scanning device, and particularly to a laser beam scanning device used in a laser beam printer or the like.

[Technological environment]

In recent years, laser beam scanning devices are required to suppress deviations in the direction perpendicular to the scanning direction of the scanning line during high-speed scanning in order to increase the speed of laser beam pre-printing and achieve high printing quality. .

[Conventional technology]

Conventional laser beam scanning devices include a rotating polygon mirror device that deflects and scans the laser beam irradiated onto the rotating polygon mirror in a direction perpendicular to the rotation axis, and an imaging lens that images the deflected and scanned laser beam onto the irradiation object. It is composed of units.

Next, a conventional laser beam scanning device will be described in detail with reference to the drawings.

FIG. 3 is a conceptual diagram showing an embodiment of a conventional laser beam scanning device, and shows an example used in a scanning section of a laser beam printer. The laser beam scanning device shown in FIG. 3 is a laser beam (laser beam) 16 emitted from a laser light source 14.
A rotating polygon mirror device 7 that polarizes and scans the polarization in a direction perpendicular to the rotation axis using a rotating polygon mirror 1, and a laser beam 16 that has been polarized and scanned.
The image forming apparatus includes an imaging lens unit (f-theta lens) 17 which forms an image on a photoreceptor 18 which is an irradiator and which is uniformly charged in advance. In the above configuration, the rotating polygon mirror 1
The laser beam 16 deflected and scanned passes through an imaging lens unit 17 and scans on a photoreceptor 18 that has been uniformly charged in advance to form an electrostatic latent image on the photoreceptor 18.

FIG. 4 is an explanatory diagram illustrating the deviation of scanning lines of a laser beam scanning device in a laser beam printer.

When the rotary polygon mirror 1 is tilted due to angular deviation of the axis of the rotary polygon mirror device 7, or when the reflective surface 21 of the rotary polygon mirror 1 is tilted with respect to the rotation axis, the laser beam 16 is emitted in a direction perpendicular to the scanning direction. Therefore, the scanning line 19 that is imaged on the photoreceptor 18 through the imaging lens unit 17 is oriented 19a in a direction perpendicular to the scanning direction.

This results in a positional shift such as 19b.

[Problem that the invention seeks to solve]

In the above-mentioned conventional laser beam scanning device, angular wobbling occurs in the rotation axis of the rotating polygon device, and if each reflective surface of the rotating polygon mirror is tilted, the scanning line on the irradiator may be perpendicular to the scanning direction. In order to keep the positional deviation to a minimum, the rotating polygon mirror device must have a bearing with high rigidity and high precision, and the balance must be adjusted with high precision. In addition, the rotating polygon mirror had to be used with a small surface inclination, making it unavoidably expensive.

[Means for solving problems]

The laser beam scanning device of the present invention includes a deflector capable of deflecting a first laser beam to be irradiated onto a rotating polygon mirror by a small angle in the direction of the rotation axis of the rotating polygon mirror; a rotating polygon mirror device that deflects and scans in a direction perpendicular to the rotation axis; an imaging lens unit that images the deflected and scanned first laser beam onto an irradiation body; A cylindrical mirror provided thereon receives reflected light of a second laser beam irradiated on the cylindrical mirror at a position rotated by 180@ with respect to a position where the first laser beam irradiates the rotating polygon mirror, and a light receiver that outputs an electrical signal according to the amount of received light; and a light receiver configured to block a part of the reflected light of the second laser beam in a direction perpendicular to the direction of the reflected light of the second laser beam, which changes depending on the angular deflection of the rotation axis. a knife disposed in front of the optical receiver, a signal processing device for measuring the angular deflection of the axis of the rotating polygon mirror device from changes in the output of the light receiver, and driving the deflector in accordance with the signal from the signal processing device. The structure includes a drive device that

〔Example〕

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a conceptual diagram showing an embodiment of the present invention, and shows an example used in a scanning section of a laser beam printer.

The laser beam scanning arrangement shown in FIG.
a deflector 15 capable of deflecting at a minute angle in the direction of the rotation axis;
A rotating polygon mirror device 6 deflects and scans the first laser beam 16 in a direction perpendicular to the rotation axis using a rotating polygon mirror 1, and the first laser beam 16 that has been deflected and scanned is applied to a uniformly charged photosensitive material which is an irradiator. An imaging lens unit (f-
θ lens) 17, a cylindrical mirror 2 provided coaxially with the rotation axis of the rotating polygon mirror device 6, and a cylindrical mirror 2 at a position rotated by 1800 degrees relative to the position where the first laser beam 16 irradiates the rotating polygon mirror 1. a second laser light source 8 that irradiates a second laser light 9 to
, a light receiver 10 that receives the reflected light of the second laser light 9 by the cylindrical mirror 2 and outputs an electric signal according to the amount of received light; A knife 11 (not shown) is arranged in front of the light receiver 10 so as to block a part of the reflected light of the laser beam 9 in the direction perpendicular to the direction of the reflected light of the laser beam 9 in FIG. It is configured to include a signal processing bag [12] that measures the angle of the rotation axis of the rotating polygon mirror device 6, and a drive device 13 that drives the deflector 15 in accordance with the signal from the signal processing device 12.

In the above configuration, the first laser beam 16 is deflected and scanned by the rotating polygon mirror 1, and the imaging lens unit 17
scans the photoreceptor 18 uniformly charged in advance through the
An electrostatic latent image is formed on this photoreceptor 18. On the other hand, the second laser beam 9 is reflected by the rotating cylindrical mirror 2 and enters the light receiver 10 . When the reflecting surface of the cylindrical mirror 2 is vertical and there is no axial wobbling of the rotating polygon mirror device 6, the laser beam 9 reflected by the cylindrical mirror 2 is reflected by the knife 11 placed at a position passing through its center point. Approximately 1/2.
Since the reflected laser beam 9 is blocked and enters the light receiver 10, the center position of the reflected laser beam 9 may be affected by the tilted reflection surface of the cylindrical mirror 2 or the axial vibration of the rotating polygon mirror assembly wt6. moves, and the amount of light blocked by the knife 11 changes.

FIG. 2 shows this state, where the horizontal axis is the rotation angle of the rotating polygon mirror device 6, and the vertical axis is the amount of light detected by the light receiver 10. The light output according to the rotation angle shows a variation in the width B around the average value A. Here, the average value A is the cylindrical mirror 2
The variation B in the measurement value corresponds to the inclination of the reflecting surface of , and is caused by the angular deflection of the axis of the rotating polygon mirror device 6. That is, by calculating with the signal processing bag ft12 from the difference between the optical output according to the rotation angle and the average value A at that angle,
The angular deflection of the shaft of the rotating polygon mirror device 6 at that point can be determined. Furthermore, by driving the deflector 15 in accordance with the angular deflection signal of the axis of the rotating polygon mirror device 16 from the signal processing device 12 and changing the angle of the laser beam 16 irradiated to the rotating polygon mirror device 6, The deviation of the scanning line 19 on the photoreceptor 18 in the direction perpendicular to the scanning direction caused by the angular deviation of the axis of the device 6 can be canceled out.

Furthermore, if fixed correction data corresponding to the amount of inclination of each reflecting surface of the rotating polygon mirror 1 is incorporated into the driving device 13, scanning on the photoreceptor 18 due to the inclination of each reflecting surface of the rotating polygon mirror 1 can be prevented. It is clear that deviations of line 19 perpendicular to the scanning direction can also be canceled out.

In the above explanation, it is assumed that the first laser beam 16 and the second laser beam 9 are emitted from different laser light sources 14 and 8, but the laser beams emitted from the same laser light source are separated by a beam splitter. , first laser beam 16,
It can also be used as the second laser beam 9.

〔Effect of the invention〕

The laser beam scanning device of the present invention irradiates a WIJ2 laser beam onto a cylindrical mirror coaxial with the rotation axis of a rotating polygon mirror device, detects the deflection of the reflected light, and obtains the angle of the axis of the rotating polygon mirror device. By adjusting the tilt amount of each reflective surface of the rotating polygon mirror and continuously correcting the angle of the first laser beam incident on the rotating polygon mirror device, it is possible to cancel the deviation of the scanning line on the irradiation object. Therefore, the bearing part of the rotating polygon mirror device is not very rigid or precise, and the balance adjustment is not very accurate. When used in a laser beam printer or the like, the printing quality can be significantly improved.

[Brief explanation of the drawing]

Fig. 1 is a conceptual diagram showing one embodiment of the present invention, and Fig. 2 is a conceptual diagram showing an embodiment of the present invention.
FIG. 3 is a conceptual diagram showing an example of a conventional laser beam scanning device;
FIG. 4 is an explanatory diagram illustrating the deviation of the scanning line of the laser beam scanning device. 1...Rotating polygon mirror, 2...Cylindrical mirror, 6
, 7...Rotating polygon mirror device, 8.14...
・Laser light source, 10...Receiver, 12...
...Signal processing device, 13...Drive device, 15.
... Deflector, 17 ... Imaging lens unit, 18 ... Photoreceptor. Bamboo 2 diagram @ rotation angle yfif 3 diagram

Claims (1)

[Claims] a deflector capable of deflecting a first laser beam to be irradiated onto a rotating polygon mirror by a small angle in the direction of a rotation axis of the rotating polygon mirror; and a deflector scanning the first laser beam in a direction perpendicular to the rotation axis by the rotating polygon mirror. a rotating polygon mirror device; an imaging lens unit that images the deflected and scanned first laser beam onto an irradiation body;
a cylindrical mirror provided coaxially with the rotation axis of the rotating polygon mirror device; and a second laser beam irradiating the cylindrical mirror at a position rotated by 180 degrees with respect to the position at which the first laser beam irradiates the rotating polygon mirror. a light receiver that receives the reflected light of the laser beam and outputs an electrical signal according to the amount of the received light; and a light receiver that receives the reflected light of the second laser beam and outputs an electric signal according to the amount of the received light; a knife edge disposed on the front surface of the light receiver so as to block the light beam; a signal processing device that measures the angular deflection of the axis of the rotating polygon mirror device from changes in the output of the light receiver; a driving device for driving the deflector according to a signal from the laser beam scanning device.