JP2002062496A - Multi-beam light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the curvature of field of a multi-beam light source device by making variance in reflection position on a polygon mirror small among laser lights. SOLUTION: The laser lights emitted by semiconductor lasers LD1 to LD4 have their X-axial positions adjusted so that they become pieces of parallel luminous flux through collimator lenses CL1 to CL4. The polarizing directions of the semiconductor lasers LD3 and LD4 are made 90 deg. different from the semiconductor lasers LD1 and LD2, the laser lights of the semiconductor lasers LD1 and LD2 are transmitted through a polarization beam splitter surface in a prism 9, and the laser lights of the semiconductor lasers LD3 and LD4 are reflected, so that the beams of the respective laser lights have the same position in a vertical scanning direction. The four laser lights are made incident on a 2nd prism 10 and split into lights which are transmitted through the beam splitter surface (unpolaried) and lights which are reflected, so that the light which has the same horizontal scanning direction and exits along the X axis will be the projection laser light of the light source.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a digital copying machine,
The present invention relates to an optical scanning device used in a writing system of an image recording device such as a laser printer and a laser facsimile, and more particularly to a light source of a multi-beam optical scanning device capable of remarkably improving a recording speed by simultaneously scanning a photosensitive member with a plurality of light beams. The present invention relates to a multi-beam light source device used as a light source.

[0002]

2. Description of the Related Art As a means for improving a recording speed in an optical scanning device used in a writing system of a recording apparatus such as a digital copying machine, a rotating polygon mirror (polygon mirror) as a deflecting means. There is a method to increase the rotation speed of the. However, in this method, the durability of the motor, noise and vibration, the modulation speed of the semiconductor laser, and the like become problems, and the recording speed is limited. Therefore, there has been proposed a multi-beam optical scanning apparatus in which a plurality of laser beams are scanned at a time to record a plurality of lines at the same time, thereby improving a recording speed. As an example, a method of combining light beams from a plurality of semiconductor laser light sources using a beam splitter or a semiconductor in which a plurality of light emitting sources are arranged in an array as disclosed in JP-A-56-42248. There is a method using a laser array.

However, the above-described semiconductor laser array has a plurality of light sources but has a common sensor for detecting the output. Therefore, although the optical output cannot be fed back in real time as in a normal semiconductor laser, Since the light sources are close to each other, the light output tends to fluctuate due to the crosstalk, so that there is a problem that high-precision light quantity control cannot be performed. In addition, it has a disadvantage of being expensive due to its specialty. Therefore, it becomes disadvantageous as the number of light sources increases.
On the other hand, a method of combining a plurality of general-purpose semiconductor lasers and combining light beams from the plurality of semiconductor lasers does not have the above-described problem, but requires improvement in environmental stability and handling.

As a multi-beam optical scanning device, there is known a system in which light beams from two semiconductor lasers are combined, and the two beams are simultaneously scanned by a deflecting means such as a rotary polygon mirror to record adjacent lines. Further higher speed and higher density are required, and three beams and four beams are required. Therefore, a semiconductor laser array has been proposed that uses a semiconductor laser array as a light source to cope with the problem.However, as described above, the semiconductor laser array has limitations in terms of control and can be handled in the same manner as a general-purpose semiconductor laser. In addition, it is not suitable for high-precision output control, and the collimating lens is common despite the fact that there are multiple light sources. Handling is troublesome, for example, because the beam emitted from the collimating lens is displaced or diverged in the direction away from each other.

Therefore, the technique disclosed in Japanese Patent Application Laid-Open No. H11-23988 realizes a multi-beam light source device having a simple structure and excellent in stability over time, and makes it possible to easily adjust the interval between beam spots. Is being planned.

FIG. 1 is a perspective view showing a device having the same configuration as an optical scanning device using a multi-beam light source device disclosed in JP-A-11-23988, and FIG. 2 is an enlarged perspective view showing the configuration of the light source unit. 3 is a plan view (A) and a side view (B).
The plurality of light beams emitted from the light source unit 1 are emitted with their emission positions approaching in the sub-scanning direction. In the main scanning direction, the beams intersect at an angle α, pass through the cylinder lens 2, and enter the polygon mirror 3. I do. The light beam is deflected and scanned by the polygon mirror 3, passes through the first scanning lens 4 and the second scanning lens 5, is reflected by the mirror 6, and reaches the photosensitive drum 7. A synchronization sensor 8 is provided outside the image area, and a write start position of the beam in the main scanning direction is controlled by a detection signal of the synchronization sensor 8.

The light source device 1 includes four semiconductor lasers LD1.
LD4, collimating lenses CL1 to CL4 provided corresponding to the semiconductor lasers LD1 to LD4, and a prism 9 having a beam splitter (BS) surface. The laser beams from the semiconductor lasers LD1 and LD2 are scanned in the main scanning direction. In the sub-scanning direction (Z direction), the semiconductor lasers LD1 to LD4 are arranged in two stages to perform beam combining.

FIGS. 4A and 4B are diagrams showing problems of the systems shown in FIGS. 1 to 3. FIG. That is, in the method shown in FIGS. 1 to 3, since the light beam has an angle α in the main scanning direction, the two beams B and C incident on the polygon mirror 3 are reflected beams by the rotation angle of the polygon mirror 3. The light is reflected by different reflection points of the polygon mirror 3 and enters the scanning lenses 4 and 5 like B 'and C' or reflected beams B "and C". Originally, scanning lens 4,
5 is designed assuming that the light beam is located at the center of the beams B and C, the reflected light B ′ and C ′ of the beams B and C or the reflected beams B ″ and C ″ are The scanning lenses 4 and 5 pass through positions deviated from ideal optical paths. 4 on the surface of the photosensitive drum 7.
A large curvature of field as shown in (B) occurs, and the quality is degraded when an image is formed.

Therefore, a multi-beam light source device according to the present invention is directed to a multi-beam light source device having a plurality of light emitting sources, wherein the light source device emits a plurality of lights in a main scanning direction and a sub-scanning direction. The positions of the two mirrors in both directions to reduce variations in the reflection positions of the polygonal mirror for a plurality of lights, thereby reducing the curvature of field, simultaneously recording a plurality of lines, increasing the writing speed and simultaneously increasing the writing speed. It is intended to make it possible to form a high quality image.

According to a second aspect of the present invention, when the multi-beam light source device of the first aspect is mounted on an optical scanning device, the sub-scanning pitch can be varied to adjust the size as desired. , The pitch setting accuracy can be improved.

According to a third aspect of the present invention, when the multi-beam light source device according to the second aspect is mounted on a scanning optical system, the sub-scanning beam pitch can be corrected with time, and the pitch can be accurately adjusted over a long period of time. It tries to make it possible to maintain.

[0012]

According to a first aspect of the present invention, there is provided a multi-beam light source device, comprising:
A light source and a plurality of light source units each including a coupling lens provided as a pair with the light source are arranged, and a beam combining unit that emits light from the plurality of light source units in the main scanning direction in proximity to each other; And a beam combining means for emitting light from the light emitting source in the sub-scanning direction.

According to a second aspect of the present invention, in order to achieve the above object, there is provided means for holding the light source device so as to be rotatable about its emission optical axis.

According to a third aspect of the present invention, in order to achieve the above object, the holding means has a drive source for driving the light source device to rotate.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. In the following, portions common to the related art are denoted by the same reference numerals, and redundant description is omitted. FIG. 5 is a perspective view of an example of an optical scanning device using one embodiment of the multi-beam light source device according to the present invention, and FIG. 6 is an enlarged view showing the configuration of the light source unit of one embodiment of the multi-beam light source device according to the present invention. FIG. 7 is a perspective view and FIG. 7 is a plan view (A) and a side view (B). The multi-beam light source device of the present embodiment includes:
The plurality of emitted light beams are emitted with emission positions approaching in the main scanning and sub-scanning directions.

The semiconductor lasers LD1 to LD4 are arranged with their positions in the X-axis direction shifted by collimating lenses CL1 to CL4 so that the respective laser beams become parallel beams, and all the laser beams are emitted in the same direction. Has become. The semiconductor laser LD3 and the semiconductor laser LD4 are arranged so that the polarization directions thereof are different from the semiconductor lasers LD1 and LD2 by 90 °. The four laser beams enter the prism 9, but due to the difference in the polarization direction, the light from the semiconductor laser LD 1 and the semiconductor laser LD 2 pass through the internal polarization beam splitter surface, and the laser beam from the semiconductor laser LD 3 and the semiconductor laser LD 4 are reflected. I do. As a result,
Semiconductor lasers LD1, LD arranged in the sub-scanning direction
The position of the beam 2 and the position of the beam of the semiconductor laser LD3, LD4 in the sub-scanning direction can be matched.

The four laser beams enter the second prism 10. A beam splitter surface (not a polarized light) is provided inside the prism 10, and the four laser beams are divided into light transmitted and reflected on the beam splitter surface. Therefore, light that coincides with the main scanning direction and is emitted in the X-axis direction can be used as the emitted laser light of the light source device.

As described above, the plurality of laser beams of the light source device coincide with each other in the main scanning direction and the sub-scanning direction.
As shown in FIG. 8A, the angles of incidence on the polygon mirror 3 are all the same as the beam A, and when they pass through the same point on the scanning lenses 4 and 5, the photosensitive member as shown in FIG. The fluctuation of the image plane on the surface of the drum 7 is suppressed to be small, and a high-quality image can be formed.

However, if the laser beam is completely matched in the sub-scanning direction, a desired sub-scanning pitch cannot be obtained, and the first purpose of the multi-beam for simultaneously writing a plurality of lines cannot be achieved. Therefore, the laser light is installed at a small angle in the sub-scanning direction, and the laser light is arranged on the surface of the photosensitive drum 7 at the sub-scanning pitch P as shown in FIG.

FIG. 10 is a perspective view showing the appearance of the above-mentioned multi-beam light source device. Each component of the light source device described above is housed in the holder 11. Holder 11
Is provided with a hollow cylindrical portion 12, the center axis of which is made coincident with the emitted laser light. The housing (not shown) of the scanning optical system is provided with a hole that fits into the outer diameter of the hollow cylindrical portion 12, and the light source device shown in FIG. Attach to optical system.

Further, the holder 11 holds the actuator 1
By means of 3, it is possible to rotate in the θ direction about the central axis of the hollow cylindrical portion 12, and it is possible to slightly change the pitch. This is used when the pitch changes over time and when the pitch is adjusted at the time of initial setting. FIG. 11 is a view showing that the laser beam train rotates by θ ′ when the holder 11 is rotated by the angle θ, and the pitch changes from P to P ′.

The actual pitch value is obtained from the data measured by the beam detection unit 8 shown in FIG. The beam detection unit 8 is capable of performing synchronous detection and simultaneously measuring the sub-scanning pitch of a plurality of beams, and may use various appropriate means.

[0023]

As described above, in the multi-beam light source device according to the first aspect of the present invention, the light source device has a plurality of light emitting sources, and the main scanning direction in which a plurality of lights from these light emitting sources are emitted. And the position in the sub-scanning direction are matched in both directions by the two beam combining means, so that the dispersion of the reflection positions of the polygon mirrors of a plurality of lights is reduced, thereby reducing the field curvature and recording a plurality of lines simultaneously. Thus, not only the writing speed can be increased, but also a high-quality image can be formed.

As described above, the multi-beam light source device according to the second aspect of the present invention has the holding means that enables the light source device to rotate about the emission optical axis thereof. In addition to the common effects, it is possible to adjust the size as desired by changing the sub-scanning pitch when mounted on the optical scanning device, and to improve the pitch setting accuracy.

As described above, the multi-beam light source device according to claim 3 of the present invention has a drive source for driving the light source device to rotate about the emission optical axis substantially at the center. In addition to the same effects as those of the device according to the second aspect, by detecting the sub-scanning beam pitch when mounted on the scanning optical system and correcting the pitch based on the result, the pitch can be corrected over time. This has the effect that the pitch can be maintained with high precision over a long period of time.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of a conventional optical scanning device using a multi-beam light source device.

FIG. 2 is an enlarged perspective view showing a configuration of the light source unit.

FIG. 3 is a plan view (A) and a side view (B).

4A is a plan view showing a problem of the apparatus shown in FIG. 1, and FIG. 4B is a diagram showing an example of a large field curvature generated on a photosensitive drum surface due to the problem.

FIG. 5 is a perspective view of an example of an optical scanning device using an embodiment of the multi-beam light source device according to the present invention.

FIG. 6 is an enlarged perspective view showing a configuration of a light source unit of one embodiment of the multi-beam light source device according to the present invention.

FIG. 7 is a plan view (A) and a side view (B).

8 is a plan view (A) corresponding to FIG. 4 showing an example in which the angles of incidence of beams on a polygon mirror are all the same by the apparatus of FIG. 6, and an image plane on a photosensitive drum surface by the apparatus of FIG. FIG. 7B is a diagram illustrating an example of a state in which the fluctuation of the image is suppressed to be small.

FIG. 9 is a diagram showing an arrangement of light beams formed by the apparatus of FIG. 6 in the sub-scanning direction.

FIG. 10 is a perspective view showing the appearance of the multi-beam light source device of FIG.

FIG. 11 is a diagram showing a change in pitch of the arrangement of light beams when the holder of the multi-beam light source device is rotated.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 light source unit 2 cylinder lens 3 polygon mirror 4, 5 scanning lens 6 mirror 7 photosensitive drum 8 synchronous sensor 9 prism 10 prism 11 holder 12 hollow cylinder 13 actuator LD1 to LD4 semiconductor laser CL1 to CL4 collimating lens A, B, C , B ', C', B ", C" beam X beam emission direction Y main scanning direction Z sub scanning direction P, P 'sub scanning pitch

Claims (3)

[Claims] 1. A beam combining means for arranging a plurality of light sources including a light source and a coupling lens provided as a pair with the light source, and emitting light from the plurality of light sources in a direction close to a main scanning direction. And a beam synthesizing unit that emits light from the plurality of light sources in the sub-scanning direction. 2. The multi-beam light source device according to claim 1, further comprising means for holding said light source device so as to be rotatable about its emission optical axis. 3. The multi-beam light source device according to claim 2, wherein said holding means has a drive source for rotating said light source device.