JP3216399B2 - Multi-beam scanning optical recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-beam scanning optical recording apparatus which divides a laser beam into a plurality of beams and processes a plurality of beams in parallel to realize high-speed scanning.

[0002]

2. Description of the Related Art Conventionally, an optical system for splitting a laser beam into a plurality of beams and making the laser beam incident on a multi-channel acousto-optic modulator has been conventionally known.
The optical system shown in FIG. 6 is used. In this optical system, in order to split a laser beam into a plurality of beams, a beam splitter in which a translucent film 30 is formed on an optical glass substrate formed of a parallel plane is used. It leads to a channel acousto-optic modulator 13.

[0003]

By the way, in order to enable the multi-channel acousto-optic modulator to modulate at high speed, it is necessary to form a laser beam to a very small beam diameter in this modulator. is there. For this purpose, FIG.
It is conceivable to insert a lens at a position indicated by an arrow 31 of the optical system shown in FIG. However, in this method, the optical path lengths of the respective laser beams passing from the lens to the multi-channel acousto-optic modulator are different, and a plurality of the respective laser beams are uniformly distributed in the multi-channel acousto-optic modulator. It is difficult to make a small beam spot.

An object of the present invention is to provide a high-speed and high-resolution multi-beam scanning optical recording apparatus using a multi-beam that can be modulated at a high speed.

[0005]

The above object can be achieved by using a polarizing element for splitting a laser beam, a multi-channel modulator for entering these beams, and a Dove prism for rotating a multi-beam after modulation. .

[0006]

According to the present invention, in order to achieve the above object, a laser beam is split into multiple beams by a polarizing element, and each beam is incident on a multi-channel modulator to modulate the light intensity, and the modulated multiple beams are emitted. Is rotated by the Dove prism and then scanned by the optical scanner.

[0007]

FIG. 2 shows an embodiment of the present invention.
FIG. 2 is a diagram for explaining the operation of an optical system using a Wollaston prism. The multi-channel acousto-optic modulator is located at four locations. Laser light 1 is a quarter-wave plate 8
The light is converted into circularly polarized light and enters the Wollaston prism 2. The Wollaston prism is formed by bonding uniaxial optical crystals having optical axes perpendicular and parallel to the paper surface, and outputs two beams 5 having different polarization directions at an angle. Since the Wollaston prism is disposed at the front focal position of the lens 3, the beam 6 emitted from the lens can form a minute spot in the multi-channel acousto-optic modulator 4 as convergent beams parallel to each other. Two beams emitted from the Wollaston prism have polarization directions orthogonal to each other, but when the multi-channel acousto-optic modulator operates only in a specific polarization direction, either one of the two beams or Both beams have a 1/1 between the Wollaston prism and the multi-channel acousto-optic modulator.
If a two-wavelength plate is arranged, the polarization direction can be adjusted.

The operation of the multi-channel acousto-optic modulator will be described with reference to FIG. One PbMoO ₄ crystal or TeO ₂
A plurality of transducers 16 are provided on an acousto-optic medium such as that described above, and can independently modulate incident multi-beam light. That is, when an independent electrical signal is given to each of the plurality of transducers, each signal independently propagates a sound wave through the crystal, and causes a corresponding light beam to be diffracted by the sound wave,
Modulate. Reference numeral 18 in FIG. 6 denotes a modulated beam,
Used for optical recording. Reference numeral 19 denotes transmitted light, which is shielded at an appropriate place so as not to reach the optical recording material. Since the light incident on the multi-channel acousto-optic modulator is parallel to each other, all the beams can be set close to the Bragg angle with respect to the ultrasonic wave generated at the electrode 16 and propagating through the crystal 13, so that high light utilization is achieved. It is possible to generate the diffracted light 18 with high efficiency, and thus to perform light modulation with high light use efficiency. Also, the multi-channel acousto-optic device 1
In 3, since the light spots are narrowed down to small light spots, the transit time of the ultrasonic waves crossing these small spots can be shortened, and high-speed light modulation becomes possible.

FIG. 1 shows a laser printer apparatus for performing optical recording by scanning multiple beams according to the present invention. Since optical recording is performed with multiple beams at a time, a high-speed or high-resolution laser printer can be realized. The laser beam 1 emitted from the laser device 11 generates a two-beam split by a quarter wavelength plate and a Wollaston prism, and is made to enter a multi-channel acousto-optic modulator. The lens 3 has already been described with reference to FIG. Reference numeral 25 denotes a circuit device for driving the multi-channel acousto-optic element. The light emitted from the multi-channel acousto-optic device is converted into an appropriate beam diameter by a lens, passes through a Dove prism 20, and enters a rotary polygon mirror 21. The rotating polygon mirror 21 is rotating, and simultaneously scans the photosensitive drum 24 with multiple beams. The lens 22 is for narrowing the multi-beam light on the photosensitive drum as a minute multi-point spot.

Incidentally, the multi-beam light is formed into a small spot row in the multi-channel acousto-optic device. If the spot diameter is D and the transducer array pitch is T, T / D is greater than 1. Therefore, the multi-point spots on the photosensitive drum are also arranged at this ratio, and the spot arrangement pitch becomes larger than the spot diameter. The multi-point spot 15 is shown on the photosensitive drum in FIG. 7 so as not to form an unirradiated area during the scanning of the multi-point spot, ie, to make the scanning line pitch smaller than the interval between the multi-point spots. Therefore, it is necessary to set the spot arrangement direction and the scanning direction to be oblique.
As a method for realizing this, there is a method in which the multi-channel acousto-optic element 13 and the polarization element 2 are simultaneously rotated with the optical axis direction as a rotation axis. It is very difficult to rotate while maintaining the accuracy of the incident position.

To solve this difficulty, a Dove prism 2
0 is used. In this method, the Dove prism 20 is rotated in the optical axis direction as a rotation axis, thereby adjusting the spot arrangement direction. The image rotation mechanism itself of the Dove prism is well known. That is, as shown in FIG. 8, the light from the image 26 is totally reflected by the bottom surface in the Dove prism to be converted into the image 27. Therefore, when the Dove prism 20 is rotated as indicated by 28, the image 26 is also rotated as indicated by 29. The photodetector 23 receives multi-beam light, generates a signal corresponding to each light, and serves as a synchronization signal for the corresponding light.

FIG. 1 shows an optical system using a Wollaston prism, but a lotion prism or a Senarmont prism may be used. Further, a polarization beam displacement element may be used. FIG. 3 illustrates the operation of the polarization beam displacement element 40. Reference numeral 8 denotes a quarter-wave plate, which converts the polarization of the incident laser light into circularly polarized light. 40 is 1 such as calcite
If it is an axial optical crystal and its optical axis is in the plane of the paper and is set at an oblique angle from the top and bottom, the polarized light in the direction perpendicular to the plane of the paper operates as an ordinary ray, and proceeds straight as shown in the figure. On the other hand, light having a polarization direction in the plane of the paper travels obliquely as an extraordinary ray as shown in the figure. After the crystal is emitted, the two branched lights travel in parallel with each other. FIG. 4 is an example in which a lens 41 is introduced into the optical system of FIG. The optical path length from the lens to the image plane 4 is not greatly different between the two beams, and both beams are accurately focused on the image plane 4 and narrowed down to a minute spot.

As described above, FIGS. 1, 2, 3 and 4 show only the case where one stage of the polarizing element is used, however, it is natural that the scanning of more beams becomes possible by using the stage in multiple stages.

[0014]

The multi-beam scanning optical recording apparatus of the present invention described above utilizes the polarization of laser light to split into multiple beams.
Since the generated multi-beams are modulated by the multi-channel acousto-optic modulator and scanned at one time, a high-speed, high-resolution optical recording device can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example in which a multi-beam scanning optical recording device of the present invention is applied to a laser printer.

FIG. 2 is a diagram illustrating an optical system that forms a minute spot parallel to each other and on the same image forming plane using a Wollaston prism and a lens.

FIG. 3 is a diagram illustrating an operation principle of a polarization beam displacement element.

FIG. 4 is a diagram showing an optical system that forms a minute spot parallel to each other and on the same image plane using the polarized beam displacement element of FIG. 3;

FIG. 5 is a diagram illustrating a problem when a conventional beam splitter is used.

FIG. 6 is a diagram for explaining the operation of the multi-channel acousto-optic modulator used in the present invention.

FIG. 7 is a diagram illustrating a method for scanning a multipoint spot used in the present invention.

FIG. 8 is a diagram for explaining the operation principle of the Dove prism used in the present invention.

[Explanation of symbols]

1 is a laser beam, 11 is a laser light source, 2 is a Wollaston prism, 3 is a lens, 13 is a multi-channel acousto-optic modulator, 16 is a transducer electrode, 20 is a dove prism, 21 is a rotating polygon mirror, and 24 is a rotating polygon mirror. The photosensitive drum 23 is a light detecting device.

Claims (6)

(57) [Claims] 1. A light source for generating a beam, and said beam
A polarizing element that splits the beam into a plurality of beams;
A multi-channel modulator for modulating the light intensity of the
Of multiple beams modulated by a multi-channel modulator
A dove prism for adjusting the angle in the array direction;
Scanning means for scanning multiple beams emitted from the rhythm
And a multi-beam scanning optical recording device. 2. A polarizing element, comprising :
Polarized light that emits multiple beams with different angles at an angle
2. The multi-beam according to claim 1, wherein the multi-beam is a prism.
Scanning optical recording device. 3. The multi-channel modulator according to claim 2 , wherein
2. A tunneling acousto-optic modulator according to claim 1, wherein
Multi-beam scanning optical recording device. 4. A light source for generating one beam, and said light source
Polarization direction different from one beam emitted from source 2
Polarizing element that emits two beams at an angle to each other
And a multi-channel for performing light intensity modulation of the two beams
A multi-beam scanning optical recording device comprising an acousto-optic modulator.
The polarization element and the multi-channel acousto-optic modulation
A lens is provided between the polarizing element and the polarizing element.
The multi-channel lens is disposed at the front focal position of the lens.
An acousto-optic modulator was placed at the back focal position of the lens
A multi-beam scanning optical recording device, characterized in that: (5) The polarizing element is a Wollaston prism
5. The multi-beam scanning optical recording according to claim 4, wherein:
apparatus. 6. For the multi-channel acousto-optic modulator
On the downstream side in the beam traveling direction,
Angle of array direction of two beams modulated by modulator
Wherein a dove prism for adjusting the angle is provided.
Item 4. Multi-beam scanning optical record Recording device.