JP3214162B2 - Optical scanning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device suitable for a laser printer which performs high-speed optical scanning with a plurality of laser beams modulated by an acousto-optic modulator.

[0002]

2. Description of the Related Art It is well known that optical scanning with a plurality of laser beams is an effective method for a high-speed laser printer. FIG. 5 is a schematic diagram showing an optical system of a laser printer using a plurality of laser beams in the related art.
The laser light 2 emitted from the laser light source 1 is incident on the grating 12 for generating a plurality of beams. Grating 12
Are designed and manufactured so as to be able to emit low to high order diffracted light with uniform light intensity. Grating 1
The plurality of laser beams generated in 2 are converted into parallel light by the lens 3 and enter the multi-channel acousto-optic modulator 13. The modulated plurality of laser beams are converted into parallel light by a lens 5 and optically scanned on a photosensitive drum 9 by a rotating polygon mirror 6. A scanning lens 7 forms an image of the beam on the photosensitive drum 9.

The operation of the multi-channel acousto-optic modulator 13 will be described with reference to FIG. Multiple transducers 1
When the frequency of the number of carriers in the radio frequency band modulated by the data signal is input to each of the
Light diffraction by the ultrasonic waves generated from 6 occurs. By this diffraction phenomenon, it is possible to generate a plurality of laser beams 18 which are independently modulated from the plurality of incident laser beams 17. The beam 19 is transmitted light that does not diffract.

[0004]

By the way, as shown in FIG. 6, a plurality of transducers 16 of the multi-channel acousto-optic modulator 13 are arranged separately so as to eliminate mutual coupling. For this reason, the interval between the light spot arrays formed by the plurality of laser beams formed on the photosensitive drum 9 is larger than the diameter of the light spot. In a laser printer, since a plurality of scanning lines formed by a plurality of laser beams must be close to each other, the light spot array 15 formed by the plurality of laser beams is oblique to the scanning direction 10 as shown in FIG. The angle is set so as to form If this angle is set incorrectly, the scanning line pitch will not be constant and will adversely affect print quality. In the optical system shown in FIG. 5, the grating 12 and the multi-channel acousto-optic modulator 1
It is necessary to precisely adjust 3 at a predetermined angle with respect to the horizontal direction. Although it is possible in principle to adjust the two parts together, it has been very difficult in practice. In particular, the multi-channel acousto-optic modulator 13
Is the first order diffracted light 18 for all beams, as shown in FIG.
In order for light to be diffracted efficiently, angle adjustment in the plane where light is diffracted, that is, adjustment of the Bragg angle requires extremely high accuracy. In addition to this, the angle is adjusted so that the light spot row is formed obliquely. It was very difficult to make adjustments.

Accordingly, an object of the present invention is to provide an optical scanning device that performs optical scanning with a plurality of laser beams using an acousto-optic modulator, and a light spot array formed by the plurality of laser beams on a scanning medium and a scanning direction. It is an object of the present invention to provide an optical scanning device capable of accurately and easily realizing the angle adjustment of the optical scanning device.

[0006]

An object of the present invention is to provide a laser light source.
Splits the laser beam emitted from the
Branching laser beam branching means and the plurality of laser beams
Multi-channel acousto-optic modulation means for modulating the
Of scanning multiple laser beams on a scanning medium
Means for scanning the multi-channel.
Double prism between the acousto-optic modulator and the deflecting means.
This is achieved by placing a system.

[0007]

According to the above construction, by appropriately rotating the Dove prism by the Dove prism rotation adjusting mechanism, the light spot array can be formed on the scanning medium at an arbitrary angle with respect to the scanning direction. Can be performed accurately and easily.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view showing an embodiment in which the optical scanning device according to the present invention is applied to a laser printer. The laser light 2 emitted from the laser light source 1 is incident on the grating 12 for generating a plurality of beams. The grating 12 is designed and manufactured so as to emit low to high order diffracted light with uniform light intensity. Plural laser beams generated by the grating 12 is converted into parallel light by a lens 3 and enters the multi-channel acousto-optic modulator 13. With the multi-channel acousto-optic modulator 13 is adjusted so that the position of the ultrasonic wave plural laser beams corresponding transducer occurs, the Bragg angle is also adjusted, thereby realizing a high diffraction efficiency. Laser beam modulated plural is converted into parallel light by the lens 5, and the deflection means
The photosensitive drum on 9 by the rotary polygon mirror 6 is scanned medium comprising optically scanning. Incidentally, 7 is a scanning lens for focusing the beam onto the photosensitive drum 9.

A Dove prism 35 is arranged between the lens 5 and the rotary polygon mirror 6. FIG. 2 is a diagram illustrating the operation of the Dove prism. As is well known, the image rotation function of the Dove prism is such that when the light from the image 36 enters the Dove prism 35, the light is totally reflected at the bottom inside the Dove prism 35,
The image 37 is converted into an image 37 whose vertical direction is inverted. Therefore, when the Dove prism 35 is rotated as indicated by an arrow 38, the image 37
Will also rotate as indicated by arrow 39. Therefore, a Dove prism rotation adjustment mechanism (not shown) for rotating the Dove prism 35 with the light traveling direction as a rotation axis is added to the Dove prism 35, and the Dove prism 35 is rotated by this Dove prism rotation adjustment mechanism. The angle of the light spot array formed on the photosensitive drum 9 with respect to the scanning direction 10 can be accurately set to a predetermined value.

FIG. 3 is a schematic view showing another embodiment in which the optical scanning device according to the present invention is applied to a laser printer. In this embodiment, the acousto-optic modulator 4 has one transducer. In this case, when a plurality of frequencies of the number of carriers in the radio frequency band are input, a plurality of primary diffraction lights are generated, and a plurality of light spots are formed on the photosensitive drum 9,
Can be scanned. FIG. 4 is an explanatory diagram of the operation of the acousto-optic modulator 4. Assume that two beams are generated for simplicity. Data 33 and data 34 have carrier frequency 3
1 and 32 are modulated, combined by the combiner 30 and input to the transducer 25. When the laser beam 24 is incident on the acousto-optic modulator 4, two diffracted beams 2 are generated by the ultrasonic wave 26.
8, 29 occur. In this method, if the frequencies of a plurality of carrier frequencies used are appropriately set, they can be generated closely like two diffracted lights 28 and 29 in FIG. May be set perpendicular to the scanning direction 10. In this case, since a plurality of spots scan the same place in the scanning direction 10, each is modulated by a synchronized data signal, which is convenient. Also in the case of the present embodiment, the Dove prism 35 is disposed between the lens 5 and the rotary polygon mirror 6,
By rotating the Dove prism 35 by a Dove prism rotation adjusting mechanism (not shown), the arrangement of the light spot array perpendicular to the scanning direction 10 can be accurately set.

[0011]

According to the present invention, since the Dove prism is disposed between the acousto-optic modulator and the rotating polygon mirror, the high diffraction efficiency of the acousto-optic modulator is maintained, and the acousto-optic modulator is not affected on the scanning medium. It is possible to accurately and easily set the angle of the light spot array formed in the scanning direction with respect to the scanning direction, and to realize an optical scanning device in which the scanning line pitch is always constant.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing one embodiment of an optical scanning device according to the present invention.

FIG. 2 is a diagram illustrating the operation of a Dove prism.

FIG. 3 is a schematic view showing another embodiment of the optical scanning device according to the present invention.

FIG. 4 is an explanatory diagram of an operation of the acousto-optic modulator.

FIG. 5 is a schematic view showing an optical scanning device according to the related art.

FIG. 6 is an operation explanatory diagram of the multi-channel acousto-optic modulator.

FIG. 7 is a diagram showing a light spot array formed on a photosensitive drum.

[Explanation of symbols]

1 is a laser light source, 4 is an acousto-optic modulator, 6 is a rotating polygon mirror, 7 is a scanning lens, 9 is a photosensitive drum, 12 is a grating, 13 is a multi-channel acousto-optic modulator, 16 is a transducer, and 35 is a Dove prism. is there.

Claims (4)

(57) [Claims] 1. A laser beam emitted from a laser light source.
Laser beam branching means for branching into a plurality of laser beams,
Multi-channel sound modulating the plurality of laser beams
Sound modulation means and a plurality of modulated laser beams
An optical scanning device comprising a deflecting means for scanning on a scanning medium , wherein a Dove prism is arranged between the multi-channel acousto-optic modulation means and the deflecting means . 2. A laser beam emitted from the laser light source enters the acousto-optical modulation means, a plurality of laser beams is formed by driving the acousto-optic modulation means in a multi-frequency, on the scanning medium by deflection means the optical scanning device for scanning a plurality of laser beams, an optical scanning apparatus which is characterized in that a dove prism between <br/> and said deflecting means and the multi-channel acousto-optic modulation means. 3. A Dove prism rotation adjusting mechanism for rotating the Dove prism around a traveling direction of light as a rotation axis is added to the Dove prism.
The optical scanning device according to claim 1. 4. The optical scanning device according to claim 1, wherein said laser beam splitting means is a grating.