JP2000028940A - Multibeam optical scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multibeam optical scanner which is simply constituted and which discriminates whether the defective light emission of a light source is caused or a synchronous detector is defective. SOLUTION: This multibeam scanner is provided with the plural light source arranged in a sub-scanning direction so as to emit light beams forward and backward. Besides, it is provided with the beam detector 13 detecting the light beams emitted backward from the plural light sources. Then, the defective light emission of the plural light sources are detected by the detector 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-beam optical scanning device used for a laser printer, a digital copying machine, or the like.

[0002]

2. Description of the Related Art In a multi-beam optical scanning device used in an electrophotographic laser printer or digital copying machine, a plurality of light beams from a plurality of light sources are deflected and scanned by a polygon mirror, and the plurality of light beams are scanned. Thus, a plurality of lines are scanned over the photoconductor in the main scanning direction. In this case, the photoconductor is scanned in the sub-scanning direction, and a plurality of light beams from a plurality of light sources are modulated by image signals, whereby an image is written on the photoconductor. Further, the light beam from the polygon mirror is detected by the synchronization detector outside the image writing area, and the light beam from the light source is modulated by the image signal in synchronization with the synchronization detector signal from the synchronization detector.

Japanese Patent Application Laid-Open No. Hei 9-187990 discloses a multi-beam optical scanning apparatus that simultaneously scans a photosensitive member with a plurality of beams arranged at right angles to the main scanning direction. (A single beam detector that detects that a plurality of beams have arrived at a predetermined position and outputs a detection signal) is provided. One beam is input, and all beams are made incident on the beam detector by multiple scans performed simultaneously by multiple beams, and the lighting state of multiple beams is provided on condition that all the multiple beams have been incident on the beam detector. (Light emission failure) is detected, and the beam detector serves as a recording signal input timing detecting means (synchronous detector) for modulating each beam. .

[0004]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No. Hei 9-187.
In the multi-beam optical scanning device described in Japanese Patent Application Laid-Open No. 990, there is a problem that when a beam cannot be detected, it cannot be distinguished whether a light emission failure of a light source has occurred or a synchronization detector has failed. SUMMARY OF THE INVENTION It is an object of the present invention to provide a multi-beam optical scanning device which can distinguish whether a light emission failure of a light source has occurred or a synchronization detector has failed with a simple configuration.

[0005]

According to a first aspect of the present invention, there is provided a multi-beam optical scanning apparatus having a plurality of light sources which are arranged in a sub-scanning direction and emit light beams forward and backward. Having a beam detector for detecting a light beam emitted backward from the plurality of light sources,
The beam detector detects the light emission failure of the plurality of light sources.

[0006]

FIG. 1 shows an embodiment of the present invention. The semiconductor laser array 1 has a light source composed of a plurality of, for example, four, semiconductor lasers arranged in the sub-scanning direction.
B4, and light beams BB1 to BB
4 is emitted. Each semiconductor laser of the semiconductor laser array 1 is connected to terminals ch1 to ch4 by a semiconductor laser driving unit.
FB1 to FB4, BB1 to BB driven by a modulation signal including an image signal from
4 is emitted.

The writing light beams FB1 to FB emitted forward from the respective semiconductor lasers of the semiconductor laser array 1
Numeral 4 is condensed by the coupling lens 2 and shaped by passing through the aperture of the aperture member 3, and is condensed by the cylindrical lens 4 to reflect the reflecting surfaces 5a, 5b, 5c,.・ It is deflected by The four light beams from the polygon mirror 5 are irradiated on the photoconductor 9 via the scanning lens 6, the long lens 7, and the bending mirror 8.

The polygon mirror 5 is rotationally driven at a constant speed by a polygon motor as a driving means, and plural light beams from the polygon mirror 5
Scan in the main scanning direction line by line. The photoreceptor 9 is, for example, a photoreceptor belt, and is rotationally driven at a constant speed by a rotation driving unit and moves in the sub-scanning direction. This photoconductor 9
Used a photoconductor belt, but a photoconductor drum or the like may be used.

The light beam from the scanning lens 6 is reflected by the bending lens 10 outside the image forming area, and is detected by the synchronization detector 12 via the correction lens 11.
This synchronization detector 12 outputs a synchronization signal from a terminal DS,
Each of the semiconductor lasers of the semiconductor laser array 1 is driven by a light source driving unit with a modulation signal including an image signal in synchronization with a synchronization signal from a terminal DS, and emits a light beam modulated by the modulation signal.

As shown in FIG. 2, a back beam detector 13 as a light emission failure detecting means is provided in a package 14 accommodating the semiconductor laser array 1 so as to face the rear side of the semiconductor laser array 1. . The back beam beam detector 13 is configured to write light beams FB <b> 1 to FB <b> 1 for writing forward from each semiconductor laser of the semiconductor laser array 1.
When FB4 is emitted, light beams BB1 to BB1 emitted backward from each semiconductor laser of the semiconductor laser array 1 at the same time are emitted.
BB4 are all detected, and these light beams BB1 to BB4 are detected.
From the terminal BS.

Therefore, each semiconductor laser of the semiconductor laser array 1 emits light beams FB1 to FB4, BB
Since the light beams 1 to BB4 are no longer emitted, the back beam beam detector 13 detects a light emission failure of each semiconductor laser of the semiconductor laser array 1. In this case, since the emission failure of each semiconductor laser of the semiconductor laser array 1 is detected by the back beam beam detector 13 separately from the synchronization detector 12, the timing other than the timing of scanning the image forming area with the light beams FB1 to FB4 is used. If so, the semiconductor laser light emission failure detection may be performed at any time, and the semiconductor laser light emission failure detection timing can be set relatively freely.

For example, as shown in FIG. 3, the light source driving unit includes the reflecting surfaces 5a, 5b, 5c,.
The modulation for generating the light beam detected by the synchronization detector 12 between the image signals respectively modulating the light beams reflected by (the timing other than the timing of scanning the image forming area with the light beams FB1 to FB4) The signal ds and the modulation signals bb1 to bb4 for emitting the light beams BB1 to BB to the respective semiconductor lasers of the semiconductor laser array 1 and detecting them with the back beam beam detector 13 are generated at mutually different timings.

One semiconductor laser of the semiconductor laser array 1 emits light beams FB1 and BB1 by the modulation signals ds and bb1 from the terminal ch1 and emits the light beams FB1 and BB1. The light beam FB1 based on the modulation signal ds is detected by the synchronization detector 12. In addition, a synchronization signal is output from the terminal DS, and the light beam BB1 based on the modulation signal bb1 is detected by the back beam beam detector 13, and a light emission failure detection signal is output from the terminal BS. The other three semiconductor lasers of the semiconductor laser array 1 emit light by the modulation signals bb2 to bb4 from the terminals ch2 to ch4, respectively, and emit light beams BB2 to BB4.
B4 is emitted, and light beams BB2 to BB4 based on the modulation signals bb2 to bb4 are detected by the back beam beam detector 13, and a light emission failure detection signal is output from the terminal BS.

The multi-beam optical scanning apparatus according to this embodiment is used in an electrophotographic image forming apparatus such as an electrophotographic laser printer or a digital copying machine. By scanning in the main scanning direction with four light beams from 8
Images are written simultaneously for four lines to form an electrostatic latent image. The electrostatic latent image on the photoconductor 9 is developed by a developing device into a toner image, and the toner image is transferred to a transfer material such as transfer paper by a transfer unit. Note that the modulation signals bb1 to bb4 are transmitted at timings corresponding to the respective transfer timings at which the respective toner images on the photoconductor 9 are respectively transferred onto the respective transfer materials (the respective image writing timings at which the respective images are written on the photoconductor 9). (Between).

In this embodiment, the back beam detector 13 separate from the synchronous detector 12 detects the light beams BB1 to BB4 from the respective semiconductor lasers of the semiconductor laser array 1 and detects the respective semiconductors of the semiconductor laser array 1. Since the light emission failure of the laser is detected, it is possible to distinguish with a simple configuration whether the light emission failure of each semiconductor laser of the semiconductor laser array 1 has occurred or the synchronous detector 12 has failed.

Optically, the light emitting points (light sources) are arranged in the sub-scanning direction, so that the light sources are multi-beams BB1 to BB.
4, the optical system having the same configuration as that of the conventional light source which is a single semiconductor laser emitting one light beam is sufficient, and the pitch of the light beam is stable. The properties are significantly increased.

Further, since a plurality of light beams BB1 to BB4 are detected by a single back beam beam detector 13,
When a plurality of light beams BB1 to BB4 are respectively detected by different back beam beam detectors, there is no variation in sensitivity of each back beam beam detector, which is a problem, and the back beam beam detector 13 If the light amounts of the light beams BB1 to BB4 are the same, the same current is generated, and the detection variation among the light beams BB1 to BB4 can be reduced.

In the above embodiment, a plurality of light sources other than the four semiconductor lasers may be used as the four semiconductor lasers as the plurality of light sources, and the beam detector 13 outputs the light beam emitted from the light source forward. May be detected.

[0019]

As described above, according to the first aspect of the present invention, with the above configuration, it is possible to distinguish, with a simple configuration, whether a light emission failure of the light source has occurred or a synchronization detector has failed. it can. Further, the optical system has the same configuration as that of the conventional light source which is a single light source that emits one light beam, and the stability of the pitch of the light beam is significantly increased. Further, detecting a plurality of light beams with a single beam detector may cause a variation in sensitivity of each beam detector, which is a problem when detecting a plurality of light beams with different beam detectors. Instead, the beam detector can reduce the detection variation among the light beams if the light amounts of the light beams are the same.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

FIG. 2 is a partially cutaway perspective view showing a part of the embodiment.

FIG. 3 is a timing chart showing operation timings of the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor laser array 5 Polygon mirror 9 Photoreceptor 12 Synchronous detector 13 Back beam detector

Claims (1)

[Claims] 1. A multi-beam optical scanning device having a plurality of light sources arranged in a sub-scanning direction and emitting light beams forward and backward, a beam detector for detecting light beams emitted backward from the plurality of light sources. A multi-beam optical scanning device, comprising: detecting a light emission failure of the plurality of light sources with the beam detector.