JPH08334712A - Multibeam optical scanner - Google Patents

Abstract

PURPOSE: To obtain an image whose printing quality is high by making output intensities of electric signals having frequencies of a radio frequency band to be inputted to transducers of a multichannel acoustic optical modulator change independently. CONSTITUTION: Circuits 19 adjusting output intensities of electric signals having frequencies of the radio frequency band to be inputted to transducers of a multichannel acoustic optical modulator 5 are added to AO drivers 12-15. Four lines of laser beams generated in a grating 3 are made incident on the multichannel acoustic optical modulator 5 by being passed through a spherical lens 4. Since AO drivers 12-15 respectively inputs electric signals having frequencies of the radio frequency band to respective transducers of the multichannel acoustic optical modulator 5 according to printing signals. four lines of laser beams arc respectively diffracted according to the printing signals. Then, AO drivers 12-15 are adjusted while respectively motoring the light intensities of four lines of the laser beams on a photo-sensitive drum 10 by a sensor 20 in which photodiodes are used.

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 which divides a laser beam into a plurality of beams and processes a plurality of beams in parallel to realize high speed.

[0002]

2. Description of the Related Art Optical scanning with a plurality of laser beams is effective in a high-speed laser beam printer because it can reduce the number of revolutions of a polygon mirror and can extend the irradiation time for one dot. well known.

The structure of a conventional multi-beam optical scanning device is
This will be described with reference to FIG. First, the laser light 2 emitted from the laser light source 1 enters the grating 3. In the grating 3, the laser light 2 is separated into four laser lights.
The four laser beams generated by the grating 3 pass through the spherical lens 4 and enter the multi-channel acousto-optic light modulator 5. Since the AO driver 12, the AO driver 13, the AO driver 14, and the AO driver 15 each input an electric signal having a frequency in the radio frequency band to the transducer of the multi-channel acousto-optical modulator 5 according to the print signal, four laser beams are emitted. Are respectively diffracted according to the print signal. The output intensities of four electric signals having frequencies in the radio frequency band input to the transducer of the multi-channel acousto-optic modulator 5 are set to be the same. The four modulated laser lights pass through the spherical lens 6 and are arranged in a predetermined beam by the Dove prism 7.
After that, the photosensitive drum 10 is optically scanned by the rotary polygon mirror 9 through the cylindrical lens 8. The lens 11 is for making the beam diameters and scanning speeds of the four laser beams scanning the photosensitive drum 10 uniform.

[0004]

In the conventional multi-beam optical scanning device, each channel of the multi-channel acousto-optical modulator is the same even if the light intensities of a plurality of laser beams incident on the multi-channel acousto-optical modulator are the same. The difference in the characteristics between the channels and the position where multiple laser beams are incident on each channel of the multi-channel acousto-optic modulator cause a difference in diffraction efficiency in each channel. , And the light intensity of the plurality of laser beams on the recording material was not uniform. In addition, the light intensity of the multiple laser beams incident on the multi-channel acousto-optic modulator also differs depending on the characteristics of the element that splits the laser beam into multiple, and the light intensity of the multiple laser beams on the recording material. Did not become uniform. When there are differences in the light intensity of multiple laser beams on the recording material, different laser beams cause different print densities and printing areas. Therefore, conventional multi-beam optical scanning devices provide uniform and highly accurate print quality. Was not obtained. An object of the present invention is to provide a multi-beam optical scanning device that forms an image with high print quality.

[0005]

SUMMARY OF THE INVENTION The above-mentioned object is to independently change the output intensities of a plurality of electric signals having a frequency in the radio frequency band input to the transducer of a multi-channel acousto-optic modulator, and to change the output intensity on a recording material. This is achieved by making the light intensities of a plurality of laser lights uniform.

[0006]

In the mechanism described above, when the output intensities of a plurality of electric signals having frequencies in the radio frequency band input to the transducer of the multi-channel acousto-optic modulator are independently changed, the diffraction efficiency in each channel is increased. Since the light intensity of the plurality of laser beams on the recording material changes independently, the light intensity of the plurality of laser beams on the recording material can be adjusted to be uniform.

[0007]

EXAMPLE An example of the present invention will be described with reference to FIG. In FIG. 1, a circuit 19 for adjusting the output intensity of an electric signal having a frequency in the radio frequency band input to the transducer of the multi-channel acousto-optic light modulator 5 is added to the AO drivers 12, 13, 14, and 15 only. Different from FIG. First, the laser light 2 emitted from the laser light source 1 enters the grating 3. In the grating 3, the laser light 2 is separated into four laser lights. Grating 3
The four laser beams generated in 1 pass through the spherical lens 4 and enter the multi-channel acousto-optic light modulator 5. Since the AO drivers 12, 13, 14, and 15 each input an electric signal having a frequency in the radio frequency band to the transducer of the multi-channel acousto-optic light modulator 5 according to the print signal, the four laser beams are diffracted according to the print signal. To be done. While monitoring the light intensities of the four laser beams on the photosensitive drum 10 by the sensors 20 using photodiodes, the AO drivers 12, 13, 14,
Adjust 15. The output intensity may be automatically controlled as in this embodiment, or the output intensity may be individually adjusted by the operator.

FIG. 2 shows how the laser light is diffracted in the acousto-optic light modulator. In FIG. 2, when an electric signal having a radio frequency band is input to the transducer 16 according to a print signal, the laser light 18 is diffracted by the sound wave generated in the AO crystal 17, and the diffracted laser light 18 reaches the photosensitive drum. To reach. In FIG. 1, the four modulated laser beams pass through the spherical lens 6,
The dove prism 7 forms a predetermined beam arrangement. After that, the photosensitive drum 10 is optically scanned by the rotary polygon mirror 9 through the cylindrical lens 8. The lens 11 is the photosensitive drum 10.
This is to make the beam diameters and scanning speeds of the four laser beams that scan the upper part uniform.

As shown in FIG. 3, since the diffraction efficiency of the laser beam changes depending on the output intensity of the electric signal having the frequency in the radio frequency band input to the transducer of the multi-channel acousto-optic modulator, the diffraction efficiency of the laser beam 4 on the photosensitive drum 10 changes. While monitoring the light intensity of the laser light of the book by the sensors 20 each using a photodiode, the AO driver 1
By adjusting 2, 13, 14, and 15, the output intensity of the electric signal for each channel input to the transducer of the multi-channel acousto-optic modulator 5 is changed, and four laser beams on the photosensitive drum 10 are changed. To make the light intensity uniform.

Although the above description describes that the laser light is separated into four by the grating, the same effect can be obtained by using an element capable of separating the laser light into a plurality of laser lights, for example, a polarization prism. Further, although it has been described that the light intensity of the laser light on the recording material is monitored by the sensor using the photodiode, the same effect can be obtained by using other sensors capable of monitoring the light intensity.

[0011]

According to the present invention, the output intensities of a plurality of electric signals having a frequency in the radio frequency band input to the transducer of the multi-channel acousto-optic modulator are independently changed, so that the plurality of recording signals on the recording material can be changed. Since the light intensity of each laser beam was changed independently and the light intensity of multiple laser beams on the recording material was made uniform, the printing density and printing area by each laser beam became uniform, and high printing quality was obtained. Image quality can be obtained.

[Brief description of drawings]

FIG. 1 shows an example of a multi-beam optical scanning device according to the present invention.

FIG. 2 shows the operating principle of an acousto-optic light modulator.

FIG. 3 shows an example of characteristics of an acousto-optic light modulator.

FIG. 4 shows an example of a conventional multi-beam optical scanning device.

[Explanation of symbols]

1 ... Laser light source, 2 ... Laser light, 3 ... Wollaston prism, 4 ... Spherical lens, 5 ... Multi-channel acousto-optic modulator, 6 ... Spherical lens, 7 ... Dove prism, 8 ... Cylindrical lens, 9 ... Rotation Polyhedral mirror, 10 ... Photosensitive drum, 11 ...
Lens, 12 ... AO driver, 13 ... AO driver, 1
4 ... AO driver, 15 ... AO driver, 16 ... Transducer, 17 ... AO crystal, 18 ... Laser light, 19 ...
Output adjustment circuit, 20 ... Sensor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoji Hirose, 1060 Takeda Hitachinaka City, Hitachinaka City, Ibaraki Prefecture, Hitachi Koki Co., Ltd. Inventor Keiji Kataoka 1060 Takeda, Hitachinaka City, Ibaraki Prefecture Hitachi Koki Co., Ltd.

Claims (3)

[Claims] 1. A laser beam is split into a plurality of beams, each beam is subjected to light intensity modulation by a multi-channel acousto-optic modulator in accordance with a print signal, and an array direction of the plurality of beams thus modulated. In the multi-beam optical scanning device for scanning a plurality of beams on a recording material by one rotating polygon mirror after rotating the angle by a dove prism, a plurality of print signals input to the multi-channel acousto-optic modulator. The multi-beam optical scanning device is characterized in that an output adjusting circuit for independently changing the output intensity of each of the plurality of beams is provided to make the light intensities of a plurality of beams on the recording material uniform. 2. A plurality of prints, each of which is provided with a sensor for detecting an output of a multi-beam to be scanned on a recording material and feeding back the output to an output adjusting circuit of the multi-channel acousto-optical modulator, 2. The multi-beam optical scanning device according to claim 1, wherein the output intensity of the signal is independently changed according to the output of the sensor to make the light intensities of a plurality of beams on the recording material uniform. 3. The multi-beam optical scanning device according to claim 2, wherein the sensor is provided near the photoconductor.