JPH09127444A - Multibeam scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multibeam scanner which is strong against circumstance variance and is capable of high-quality recording. SOLUTION: With respect to a multibeam scanner 10, two semiconductor lasers 31 and 32, collimator lenses 38 and 39, a beam synthesizing prism 41, a half wave plate 42, etc., are formed as one body in a light source part 30, and two laser beams are synthesized by the beam synthesizing prism 41 and are separated by a prescribed angle in the subscanning direction and are emitted. Laser beams from the light source part 30 are thrown to a polarizing mirror 15 through a rotary polygon mirror 13 and an fθ lens 14. The polarizing mirror 15 can be moved to a separation position on the optical axis and a retraction position off the optical axis. When it is placed in the separation position, two laser beams are separated toward mirrors 16 and 17 and are allowed to scan in different positions on a photosensitive body 18 to realize color recording; and when it is placed in the retraction position, laser beams are made pass and are allowed to scan on the photosensitive body 18 with a prescribed scanning line pitch (p) through the mirror 16 to realize monochromatic recording.

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 device, and more particularly to a multi-beam scanning device for recording with a plurality of laser beams.

[0002]

2. Description of the Related Art In a writing apparatus such as a laser printer or a digital copying apparatus, one laser beam is conventionally used as a means for recording two colors of black and red. Modulate and scan a black image on the photoreceptor,
Next, a method of scanning with a red image by superimposing it on the photoconductor with the previous black image by modulating the red writing information is used.

However, in the above-mentioned conventional two-color recording method, it is necessary to rotate the photosensitive member by the amount of scanning in black and red, that is, it is required to rotate twice, and not only it takes a long processing time but also two-color recording. In order to record the sheet without misalignment, the conveyance accuracy of the recording sheet is required to be precise.

Therefore, conventionally, by writing two laser beams, which are respectively modulated by red writing information and black writing information, to a single photosensitive member at a time, the photosensitive member can be rotated only once. A multi-beam scanning device that performs two-color recording has been proposed.

An example of such a multi-beam scanning device is disclosed in Japanese Patent Laid-Open No. 58-79215, and this multi-beam scanning device includes two laser light sources having polarization characteristics and two laser light sources. It has a polarization beam splitter that combines the beams into one beam, a single polygon mirror, a single fθ lens, and a polarization beam splitter that separates the single beam into two beams. Further, there is one disclosed in JP-A-60-32019, which is a first and a second laser light source which emits a laser beam which is linearly polarized in directions perpendicular to each other and whose brightness is modulated by a signal to be recorded. Polarization combining means for combining two laser beams emitted from the laser source,
A deflecting unit that deflects the combined laser beam in the main scanning direction and a scanning lens that projects the combined laser beam deflected by the deflecting unit as separate spots on the scan recording surface are provided.

In each of these conventional multi-beam scanning devices, a light source device for emitting a laser is attached to a side wall of a separate device frame in a direction perpendicular to the beam splitter.

That is, as shown in FIG. 7, a multi-beam scanning device 1 is generally provided with a beam splitter 3 and two light source devices (for example, semiconductor lasers) 4 and 5 in a device frame 2. And the light source devices 4 and 5 are
They are arranged in separate device frames 2 that are positioned at right angles to the beam splitter 3. Beam splitter 3
The laser beams emitted from the respective light source devices 4 and 5 arranged in the direction orthogonal to the are modulated by the black writing information and the red writing information, respectively.
And is irradiated onto the rotary polygon mirror 6. The rotary polygon mirror 6 linearly converts the irradiated laser beam and irradiates it onto a photoconductor (not shown) via the fθ lens 7 and the folding mirror 8.

[0008]

However, in such a conventional multi-beam scanning device, since the two light source devices are attached to different device frames, environmental temperature and environmental humidity are reduced. When the device frames are distorted due to such environmental changes, the scanning line positions of the laser beams emitted from the two light source devices mounted on different device frames change, and the appropriate color superposition accuracy is obtained. However, there is a problem that the image quality is deteriorated. Further, when replacing one of the light source devices, it is necessary to adjust the optical axis with the laser beam of the other light source device, which makes the replacement work of the light source device cumbersome and the workability of maintenance work is poor. There was a problem.

Therefore, according to the first aspect of the present invention, the laser emitting elements for emitting two laser beams are aligned in the main scanning direction and integrally incorporated in the light source section so that the light source section can be attached or detached, and the ambient temperature can be increased. Even if a change in environment such as or environmental humidity occurs, it is possible to prevent the spot position irradiated on the photosensitive member from changing and improve the workability of the maintenance work of the multi-beam scanning device.
It is an object of the present invention to provide a multi-beam scanning device capable of improving color overlay accuracy.

According to the second aspect of the present invention, by making the scanning positions of the two laser beams coincide with each other in the main scanning direction, the synchronization timing of one laser beam is controlled by the synchronization timing of one laser beam, An object of the present invention is to provide a multi-beam scanning device which can simplify the circuit configuration and can accurately adjust the writing start positions of two laser beams to improve the image quality of two-color recording.

According to the third aspect of the present invention, by controlling the output intensity of the laser beam based on the correction data in consideration of the light quantity characteristics of the two laser beams, the occurrence of density unevenness is suppressed, and two-color recording is performed. It is an object of the present invention to provide a multi-beam scanning device capable of improving the image quality of.

According to a fourth aspect of the present invention, by switching the polarization separating means between the separating position and the retracted position, high density (double density) corresponding to 2-color recording and 1/2 scanning line pitch at the time of 2-color recording. (1) A single-color recording or a double-speed single-color recording can be easily and easily switched to provide a multi-beam scanning device capable of improving the utility of the multi-beam scanning device. There is.

It is an object of the present invention to provide a multi-beam scanning device capable of appropriately controlling the exposure energy per unit time on the photoconductor to improve the image quality.

[0014]

According to another aspect of the multi-beam scanning device of the present invention, two laser beams that are modulated by writing information of different colors and have different polarization directions are combined and emitted. A light source section, a deflection means for deflecting the two laser beams emitted from the light source section in the main scanning direction, a polarization separation means for separating the two laser beams deflected by the deflection means, and the polarization separation A multi-beam scanning device comprising: an image forming means for scanning each laser beam separated by the means to a different position on one photoconductor; and a drive control means for controlling the laser beam by the light source section. The light source section is at least
A laser emitting element that emits two laser beams separated from each other in the main scanning direction by a predetermined amount, a collimator lens that converts the laser beams emitted from the laser emitting elements into parallel light beams, and a parallel light beam by the collimator lens. The above-described object is achieved by integrally assembling the beam combining means for combining and emitting the converted laser beams into the laser beam.

Here, as the laser emitting element, a semiconductor laser, a semiconductor laser array, or the like is used, and the laser emitting elements are mounted on a mounting means such as one substrate at a predetermined distance in the main scanning direction so that they are mutually positioned in the main scanning direction. A quantitatively separated laser beam is emitted.

The beam combining means moves the laser beams, which are separated from each other by a predetermined amount in the main scanning direction, in the main scanning direction to combine them.

The deflecting means is, for example, a rotating polygon mirror,
The polarization separation means separates the two laser beams by utilizing the fact that the two laser beams emitted from the light source section have different polarization directions.

A mirror, a lens, or the like is used as the image forming means, and an image of the laser beam is formed as a spot on the photosensitive member.

According to the above structure, since the laser emitting elements for emitting two laser beams are integrated in the light source unit side by side in the main scanning direction, the light source unit can be attached or detached, and the ambient temperature or Even if environmental changes such as environmental humidity occur, the optical axes of the two laser beams are kept relatively constant, and it is possible to prevent the spot position irradiated on the photoconductor from changing. The workability of the maintenance work of the beam scanning device can be improved, and
The color overlay accuracy can be maintained, and the recording accuracy of two-color recording can be improved.

In this case, for example, as described in claim 2, the beam combining means makes one of the two laser beams separated by a predetermined amount in the main scanning direction coincide with the other main scanning direction. The image forming means makes one of the laser beams separated by the polarized light separating means incident also on the synchronization detecting means provided in the vicinity of the photoconductor, and the drive control means, The synchronization timing of the two laser beams emitted by the laser emitting element may be controlled based on the detection result of the synchronization detection means.

Here, the beam synthesizing means moves one of the two laser beams apart from each other by a predetermined amount in the main scanning direction toward the other laser beam in the main scanning direction to move the two laser beams. Combine laser beams.

As the synchronization detecting means, for example, a known technique such as a photodiode can be used.

According to the above construction, since the scanning positions of the two laser beams in the main scanning direction coincide with each other, the synchronization timing of the two laser beams can be controlled by the synchronization timing of the one laser beam. The circuit configuration can be simplified, the writing start positions of the two laser beams can be accurately aligned, and the image quality of two-color recording can be improved.

Further, for example, as described in claim 3, the drive control means sets the output intensity of one of the two laser beams emitted from the laser emitting element to the output intensity of the other laser beam. It may be controlled according to the light amount characteristic.

Here, the drive control means sets the output intensity of one laser beam to the light amount characteristic of the other laser beam based on the correction data for correcting the difference in the light amount characteristic of the laser beam due to the difference in the polarization direction. Control together.

According to the above structure, since the two laser beams have different polarization directions, there is a difference in the reflection characteristics of the laser beam by the polarization means, the image formation means, etc., and the amount of light on the photoconductor is large. Although a characteristic difference occurs, the output intensity of the laser beam can be controlled based on the correction data in consideration of the light amount characteristic, and the light amount characteristics of the two laser beams on the photoconductor can be matched. As a result, the occurrence of density unevenness can be suppressed, and the image quality of two-color recording can be improved.

Further, for example, as described in claim 4, the light source section emits the two laser beams in a state in which their optical axes are inclined in the sub-scanning direction by a minute angle, and the polarization separation means. Is movable to a separation position positioned on the optical path of the laser beam emitted from the light source section and a retracted position retracted from the optical path, and when in the separation position, the laser from the light source section is When the beam is separated and scanned at different positions of the photoconductor through the image forming means, and the laser beam from the light source section is not separated when the photoconductor is in the retracted position, the beam is separated through the image forming means. You may make it scan on the said photoconductor in the state which opened the scanning line pitch corresponding to the said fine angle.

According to the above construction, the two-color recording and the two-color recording are performed by switching the polarization separating means between the separating position and the retracted position.
Simple high-density (double-density) single-color recording or double-speed single-color recording corresponding to 1/2 scanning line pitch during color recording,
In addition, the switching can be easily performed, and the utility of the multi-beam scanning device can be improved.

Further, for example, as described in claim 5, the drive control means emits the laser emitting element depending on whether the polarization separating means is at the separating position or the retracted position. The output intensity of the laser beam may be controlled.

According to the above arrangement, the exposure energy per unit time on the photoconductor can be appropriately controlled, and the image quality can be improved.

[0031]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

Since the embodiment described below is a preferred embodiment of the present invention, various technically preferable limitations are attached, but the scope of the present invention is particularly limited in the following description. Unless specifically stated to limit the present invention, the present invention is not limited to these embodiments.

FIGS. 1 to 5 are views showing an embodiment of a multi-beam scanning device according to the present invention, which uses two semiconductor lasers, and a writing system such as a digital copying device or a laser printer. Applied to the scanning device.

FIG. 1 is an exploded perspective view of a multi-beam scanning device 10 to which an embodiment of the multi-beam scanning device of the present invention is applied. The multi-beam scanning device 10 includes a light source section 30 and a semiconductor laser driving circuit section. (Drive control means) 11,
Cylinder lens 12, rotating polygon mirror (deflecting means) 13, f
A θ lens 14, a polarization mirror (polarization separating means) 15, mirrors (imaging means) 16 and 17, a photoconductor 18, a synchronization detection sensor (synchronization detection means) 19 and the like are provided.

As will be described later, the light source section 30 is provided with two semiconductor lasers 31 and 32 and emits two laser beams. The two laser beams have different polarization directions by 90 degrees. Therefore, the two laser beams emitted from the light source unit 30 enter the rotary polygon mirror 13 via the cylinder lens 12.

The rotary polygon mirror 13 rotates at a predetermined constant angular velocity, repeatedly deflects the two incident laser beams in the main scanning direction, and reflects them in the fθ lens 14 direction. The fθ lens 14 performs constant-velocity linear conversion on each of the two laser beams incident from the rotary polygon mirror 13 to produce a polarization mirror 15.
Incident on. Now, since the two laser beams emitted from the light source unit 30 have different polarization directions by 90 degrees, one of the two laser beams incident on the polarization mirror 15 is mirrored by the polarization mirror 15. The light is reflected in the direction of 17 and is illuminated by the mirror 17 as a spot at a predetermined scanning position on the photoconductor 18, while the other passes through the polarization mirror 15 in the direction of the mirror 16 as it is,
And is irradiated as a spot at a predetermined scanning position on the photoconductor 18. The laser beam reflected by the mirror 16 is also made incident on the synchronization detection sensor 19 and used for synchronization processing.

The polarization mirror 15 is retractable, that is, it is moved between a separation position on the optical path of the laser beam from the fθ lens 14 and a retracted position retracted from the optical path of the laser beam from the fθ lens 14. When the laser beam from the f.theta. Lens 14 is disposed so that it can be separated, the laser beam from the f.theta.
However, when moving to the retracted position, fθ lens 1
All the laser beams from 4 go straight to the mirror 15.

The semiconductor laser drive circuit 11 includes semiconductor laser control units 21 and 22 and a beam intensity correction data memory 2.
3, the semiconductor laser control unit 21 receives a black write signal (black write information), and the semiconductor laser control unit 22 receives a black write signal.
A red writing signal (red writing information) is input respectively. The semiconductor laser control unit 21 drives and controls the semiconductor laser 31 of the light source unit 30 based on the input black writing signal, and causes the semiconductor laser 31 to emit a laser beam modulated based on the black writing signal. The semiconductor laser control unit 22 determines the light source unit 3 based on the input red writing signal.
Drive the semiconductor laser 32 of 0
The laser beam modulated based on the red writing signal is emitted.

These semiconductor laser 31 and semiconductor laser 3
In the present embodiment, 2 emits a laser beam of the same polarization direction, for example, a P-polarized beam, but the semiconductor laser 3 is emitted to the light source unit 30 as described later.
The laser beam emitted from 1 is polarized 90 degrees 1 /
A two-wave plate 42 is provided, and the P-polarized beam emitted from the semiconductor laser 31 is converted into S by the half-wave plate 42.
Since it is polarized into a polarized beam, the light source section 30 emits a P-polarized beam and an S-polarized beam.

However, as is generally known, the S-polarized beam and the P-polarized beam are the rotating polygon mirror 13 and the mirror 1.
Since the reflection characteristics of 5, 16, 17, etc. are different,
As shown in, the light amount characteristics with respect to the main scanning direction at the time of irradiating the photoconductor 18 are different, and if the laser beams of the semiconductor laser 31 and the semiconductor laser 32 are directly radiated to the photoconductor 18, uneven light amount occurs. .

Therefore, in this embodiment, the beam intensity stored in the beam intensity correction data memory 23 is used to correct the intensity of the semiconductor laser 32 with which the emitted laser beam remains as the P-polarized beam and is applied to the photoconductor 18. It is based on the correction data. That is, the beam intensity correction data memory 23 stores beam intensity correction data that linearly increases in the main scanning direction as shown in FIG. 2, and the semiconductor laser control unit 22 uses the beam correction data memory. The intensity of the laser beam emitted from the semiconductor laser 32 is corrected and controlled based on the beam correction data stored in 23. The semiconductor laser control unit 22 corrects the beam intensity, for example, by changing the amount of current supplied to the semiconductor laser 32 based on the beam intensity correction data. The laser beam emitted from the semiconductor laser 32 has the same light amount characteristic at the time of irradiating the photoconductor 18.

Light source unit 3 of the multi-beam scanning device 10
As shown in the exploded perspective view of FIG. 3, 0 includes semiconductor lasers (laser emitting devices) 31 and 32, and the semiconductor lasers 31 and 32 are fixedly held by supports 33 and 34, respectively. The semiconductor lasers 31, 32 are attached to the supports 33, 34.
Holes 33a, 34 through which the laser beam emitted from
a is formed. The semiconductor lasers 31 and 32 are
The pn junction surfaces are aligned and aligned on the same surface, and are fixed to the supports 33 and 34.

The supports 33 and 34 are attached to the back surface of the base body 37 by screws 35 and 36, and two cylindrical portions 37 having a diameter of a predetermined size are provided at the substantially central portion of the front surface of the base body 37.
a and 37b are formed. Through holes are formed in the cylindrical portions 37a and 37b to penetrate the base body 37, and collimator lenses 38 and 39 accommodated in the lens barrel are accommodated in the cylindrical portions 37a and 37b. The collimator lenses 38 and 39 housed in the barrel are the semiconductor laser 31,
The cylindrical portion 37 of the base 37 is aligned with the optical axis of 32.
a and 37b are fixed by adhesion, and collimator lenses 38,
The lens barrel that houses 39 has collimator lenses 38, 3
Aperture plates 40 each having a perfect circular slit for 9 are integrally attached.

A beam combining prism (beam combining means) 41 formed in a substantially trapezoidal shape is provided on the front surface of the diaphragm plate 40, and the bottom of the beam combining prism 41 passes through the collimator lenses 38 and 39 to stop the beam. The laser beam shaped by the plate 40 enters the beam combining prism 4
1 laser beam on one side of the bottom surface (in this embodiment,
The half-wave plate 42 is attached to the incident surface of the laser beam emitted from the semiconductor laser 31. Therefore, the semiconductor laser 31 incident on the half-wave plate 42
The laser beam emitted from is incident on the beam combining prism 41 with its polarization plane rotated by 90 degrees.

The beam combining prism 41 has a polarization beam splitter surface 41a formed therein and an inclined surface 41b formed on the incident side of the semiconductor laser 32. The beam combining prism 41 uses the laser beam from the semiconductor laser 31 incident through the ½ wavelength plate 42 as a reference laser beam and emits the laser beam from the semiconductor laser 32 through the ½ wavelength plate 42. The beams are combined near the optical axis of the reference laser beam and emitted. That is, the laser beam from the semiconductor laser 32 that has entered without passing through the half-wave plate 42 is reflected by the inclined surface 41 b in the direction of the polarization beam splitter surface 41 a and enters without passing through the half-wave plate 42. The laser beam from the semiconductor laser 31 passes through the polarization beam splitter surface 41a and is emitted as it is. However, the laser beam from the semiconductor laser 31 is emitted from the semiconductor laser 32 in the vicinity of the passing position of the polarization beam splitter surface 41a. Laser beam is reflected by the inclined surface 41b and is incident. Therefore, the laser beam from the semiconductor laser 32 is emitted from the semiconductor laser 3
The laser beam from 1 is moved near the optical axis in the main scanning direction, combined, and emitted.

The optical axes of the semiconductor laser 32 and the collimator lens 39 are set so as to be deviated from the optical axes of the semiconductor laser 31 and the collimator lens 38 in the sub-scanning direction by a fine predetermined angle. The laser beam from the semiconductor laser 31 and the laser beam from the semiconductor laser 32 are emitted from the beam combining prism 41 at a predetermined angle (shown by θ in FIG. 3). The laser beam from the semiconductor laser 31 and the laser beam from the semiconductor laser 32 have their main scanning directions coincident with each other and have a predetermined emission angle difference θ in their sub-scanning direction.
The emission angle difference θ becomes the basis of the scanning line pitch p (see FIG. 1) in the sub-scanning line direction when the polarizing mirror 15 is retracted to the retracted position, as will be described later.

Beam combining prism 41 and diaphragm plate 40
Is a screw 44, at a predetermined position on the back surface of the flange member 43.
It is fixed together with the base body 37 by 45, and further, the flange member 43 and the base body 37 are fixed to the board 46 by screws not shown. The semiconductor laser drive circuit section 11 of the semiconductor lasers 31 and 32 is formed on the back surface of the substrate 46.

The flange member 43 is formed with a cylindrical portion 43a through which the laser beam emitted from the beam synthesizing prism 41 passes, and the cylindrical portion 43a projects from the front surface of the flange member 43 by a predetermined amount.

An aperture 48 for shaping the effective beam diameter of the laser beam emitted from the cylindrical portion 43a is attached to the cylindrical portion 43a, and the aperture 48 has its snap claw 48a as shown in FIGS. 4 and 5. , 48b are engaged with the ring groove 43b formed in the cylindrical portion 43a, so that they are rotatably attached to the cylindrical portion 43a.
The aperture 48 has a positioning protrusion 48c formed at a predetermined position on the outer peripheral portion thereof.
Is for determining the rotational angular position of the aperture 48.

The flange member 43, as shown in FIG.
The cylindrical portion 43a is inserted into a through hole 49a formed in the holding plate 49, and is held rotatably by a predetermined angle on the holding plate 49 about the cylindrical portion 43a, that is, about the optical axis. For example, it is a frame of a laser printer or the like to which the laser scanning device 1 is attached. As shown in FIG. 3, a positioning groove 49b is formed in the through hole 49a of the holding plate 49, and the cylindrical portion 43a of the flange member 43 to which the aperture 48 is attached is inserted into the through hole 4a.
When it is inserted in the aperture 9a, the positioning protrusion 48c of the aperture 48 enters the positioning groove 49b, and the aperture 48
The rotational angular position of is determined.

The semiconductor lasers 31, 32 and the support 3
3, 34, the base 37, the collimator lenses 38, 39, the beam combining prism 41, the half-wave plate 42, and the flange member 43 constitute the light source unit 30 as a whole.

A pair of screw holes 49c are formed in the holding plate 49 at positions opposed to each other with the through hole 49a interposed therebetween, and the light source section 30 is screwed into the screw hole 49c as shown in FIG. The screws 50 are connected and fixed.

When the light source section 30 is connected and fixed by the screw 50, the screw hole 49c allows the laser beam of the semiconductor laser 31 and the laser beam of the semiconductor laser 32 emitted from the beam combining prism 41 to move in the sub-scanning direction. It is formed so as to be in a lined position.

Next, the operation will be described.

First, a case where two colors, for example, two colors, red and black, are recorded by using the multi-beam scanning device of the present embodiment will be described. When performing two-color recording, the polarization mirror 47 is located on the optical path of the laser beam as shown in FIG.

In the multi-beam scanning device 10, the light source section 30 is provided with two semiconductor lasers 31 and 32. The semiconductor laser 31 and the semiconductor laser 32 have the same pn junction surface and are the same. It is arranged on a plane and its optical axis is slightly displaced in the main scanning direction. Further, the semiconductor laser 31 and the semiconductor laser 3
2 is attached to the same substrate 46,
It is integrated into one light source unit 30.

Then, as described above, the semiconductor laser 31
Emits a P-polarized laser beam modulated by a black writing signal, and the semiconductor laser 32 emits a P-polarized laser beam modulated by a red writing signal. And
The laser beams emitted from the semiconductor laser 31 and the semiconductor laser 32 are converted into parallel light beams by the collimator lenses 38 and 39, shaped by the diaphragm plate 40, and incident on the beam combining prism 41. However,
The laser beam emitted from the semiconductor laser 31 is 1 /
The polarization plane is rotated by 90 degrees by the two-wave plate 42 and is incident on the beam combining prism 41 as an S-polarized beam.

The laser beam emitted from the semiconductor laser 31 is polarized by 90 ° by the half-wave plate 42 to become an S-polarized beam. Therefore, when it enters the beam combining prism 41, the polarization beam splitter surface 41a. The laser beam emitted from the beam synthesizing prism 41 and emitted from the semiconductor laser 32 is not P-polarized by the ½ wavelength plate 42 but is still a P-polarized beam without being reflected by. Therefore, the inclined surface 41b allows the semiconductor laser 31 of the polarization beam splitter surface 41a to be formed.
The laser beam emitted from is deflected in the main scanning direction and combined.

Further, since the optical axes of the semiconductor laser 32 and the collimator lens 39 are set so as to be deviated from the optical axes of the semiconductor laser 31 and the collimator lens 38 by a fine angle in the sub-scanning direction, the beam combining prism 41. As shown in FIG. 3, the laser beam emitted from the semiconductor laser 32 emitted from the semiconductor laser 32 is emitted at a predetermined angle θ in the sub-scanning direction with respect to the laser beam emitted from the semiconductor laser 31. It passes through the cylindrical portion 43 a of 43 and the aperture 48, and is emitted to the cylinder lens 12 shown in FIG. 1.

The laser beams emitted from the semiconductor laser 31 and the semiconductor laser 32 to the cylinder lens 12 are
The light enters the rotary polygon mirror 13 and is repeatedly deflected in the main scanning direction by the rotary polygon mirror 13 to generate an fθ lens 14
Is incident on. The fθ lens 14 linearly converts the laser beams from the semiconductor laser 31 and the semiconductor laser 32, which are incident from the rotary polygon mirror 13, at a uniform velocity, and makes the laser beams enter the polarization mirror 15.

Since two-color recording is now performed, as described above, the polarization mirror 15 is located at the separation position on the optical path and f
The laser beam from the θ lens 14 is separated, and one of them is moved to the mirror 17, and the other is moved to the mirror 16. Mirror 1
The laser beams that have traveled to 7 and the mirror 16 are reflected by the mirror 17 and the mirror 16, respectively, and are irradiated as spots on predetermined scan recording surfaces of the photoconductor 18, and are modulated by the red and black writing information. The two scan lines thus formed are simultaneously written on the photoconductor 18. At this time, the two scanning lines are finally scanned at the overlapping position.

Since the laser beam emitted from the semiconductor laser 32 remains the P-polarized beam as described above, it is affected by the reflection characteristics of the rotary polygon mirror 13, the mirrors 15, 16, 17 and the like. As shown in FIG. 2, the light amount characteristic is deteriorated as compared with the S-polarized beam, but the semiconductor laser control unit 22 for controlling the driving of the semiconductor laser 32 has a beam intensity correction data memory as shown in FIG. The semiconductor laser 32 is drive-controlled by correcting and controlling the amount of current based on the beam intensity correction data provided by the reference numeral 23.

Therefore, the laser beam emitted from the semiconductor laser 32 imparts the same amount of light as that of the laser beam emitted from the semiconductor laser 31 to the photoconductor 18, and the photoconductor 18 is appropriately generated without unevenness in the amount of light. Can be scanned. As a result, high-quality two-color recording without color unevenness can be performed.

The semiconductor laser 32 and the semiconductor laser 3
When the output control of the laser beam is performed in consideration of the light amount characteristics shown in FIG. 2 for both No. 1 and No. 1, the light amount characteristics can be made uniform in the main scanning direction.

As described above, the semiconductor laser 31 and the semiconductor laser 32 are mounted side by side in parallel on the same substrate 46 and are integrally incorporated in one light source section 30, so that the device Holding plate 4 for frames
The influence of the environmental change after fixing the light source unit 30 to 9 is small, the fluctuation of the scanning spot positions of the semiconductor laser 31 and the semiconductor laser 32 due to the environmental change can be suppressed, and the light source unit 30 can be replaced. Even if it is performed, it is possible to easily and easily secure an appropriate scanning spot position without performing fine pitch adjustment. As a result, the color overlay accuracy can be stabilized, the image quality can be improved, and the workability of maintenance work can be improved.

Next, the case of performing monochromatic recording will be described. When monochromatic recording is performed, recording is performed with the polarization mirror 15 being moved to the retracted position retracted from the optical path of the laser beam.

That is, when the polarization mirror 15 moves to the retracted position, it is reflected by the rotary polygon mirror 13 and the fθ lens 14
All the laser beams emitted from the semiconductor laser 31 and the semiconductor laser 32 that have passed through are irradiated on the mirror 16, reflected on the mirror 16, and then irradiated on the photoconductor 18.

In this case, for example, the semiconductor laser 31 is modulated and driven by the write signals of the odd-numbered rows, and the semiconductor laser 32 is modulated and driven by the write signals of the even-numbered rows, whereby monochromatic recording can be performed.

Now, the laser beams emitted from the semiconductor laser 31 and the semiconductor laser 32 are set so that their optical axes are shifted by a minute predetermined angle in the sub-scanning direction. Therefore, the two laser beams emitted from the light source unit 30 are emitted with a predetermined angle θ offset in the sub-scanning direction, and are projected on the photoconductor 18 by the scanning line pitch p in the sub-scanning direction as shown in FIG. The spot position is shifted and irradiated. As a result, by fixing the light source unit 30 to the holding plate 49, the scanning line pitch p, that is, the recording density can be uniquely set, and it is necessary to finely adjust the scanning line pitch as in the conventional case. Thus, the work of mounting the multi-beam scanning device 10 and the work of replacing the light source unit 30 and the like can be performed easily and easily.

By setting a recording density of, for example, 300 dpi as the recording density in the case of two-color recording, two laser beams are applied to the photoconductor 18 in the case of single-color recording. , Double the recording density without changing the rotational speed of the rotary polygon mirror 13 or the transfer speed of the write information, that is, 600 dpi (scan line pitch p =
42.3 μm), and high-density recording can be easily performed.

In this case, the semiconductor laser control unit 22
By setting the output intensity of the laser beam of the semiconductor laser control unit 21 to 1/2 of that in the case of two-color recording, the exposure energy per unit area on the photoconductor 18 becomes the same as that in the case of two-color recording. It can be set, and high quality and high density recording can be performed easily and easily.

Also in this case, the semiconductor laser 31 and the semiconductor laser 32 are mounted on the same substrate 46 as described above, and at the same time, one light source section 3 is used.
Since the light source unit 30 is fixed to the holding plate 49 such as the device frame, the influence of environmental changes is small, and the semiconductor laser 31 and the semiconductor laser 32 are integrated.
The fluctuation of the scanning spot position can be suppressed. As a result, the accuracy of the scanning line pitch p can be stabilized and the image quality can be improved.

Further, when performing monochrome recording, the photosensitive member 18
The recording speed can be increased by increasing the rotation speed of. For example, the recording density for 2-color recording is 3
When it is 00 dpi, by making the rotation speed of the photoconductor 18 double, it is possible to perform single-color recording of 300 dpi, and the recording speed can be doubled.

The invention made by the present inventor has been specifically described above based on the preferred embodiments, but the present invention is not limited to the above, and various modifications can be made without departing from the scope of the invention. It goes without saying that it is possible.

For example, in the above embodiment, the case of two-color recording using two semiconductor lasers has been described, but the same applies to the case of using a semiconductor laser array.
Can be applied.

Further, in the above embodiment, the semiconductor lasers 31 and 32 are arranged on the same plane with their pn junction surfaces aligned, and one of the laser beams incident on the beam combining prism 41 is beam 1/2. The two planes of laser light are combined by the beam combining prism 41 by rotating the plane of polarization by 90 degrees by making them incident through the wave plate 42. The half-wave plate 42 may be omitted by emitting a laser beam rotated by 90 degrees.

Further, in the above embodiment, the case where two semiconductor lasers 31 and 32 are used as the laser emitting elements and two laser beams are emitted has been described. However, the laser beams emitted by the laser emitting elements are The number of laser beams is not limited to two, and the same applies to the case of emitting three or more laser beams at the same time.

In this case, as the number of laser beams emitted by the laser emitting element increases, the beam synthesizing prisms 41 may be provided in multiple stages in the laser beam emitting direction.

[0079]

According to the multi-beam scanning device of the first aspect of the present invention, since the laser emitting elements for emitting two laser beams are lined up in the main scanning direction and integrally incorporated in the light source section, Even if the light source unit is attached or detached or the environment such as environmental temperature or humidity changes, the optical axes of the two laser beams are kept relatively constant, and the spot position on the photoconductor is Can be prevented from fluctuating,
The workability of the maintenance work of the multi-beam scanning device can be improved, the color superposition accuracy can be maintained, and the recording accuracy of two-color recording can be improved.

According to the multi-beam scanning device of the second aspect, since the scanning positions of the two laser beams in the main scanning direction coincide with each other, the two laser beams are synchronized by the synchronization timing of one laser beam. It is possible to control the synchronization timing of the two, to simplify the circuit configuration, to accurately align the writing start positions of the two laser beams, and to improve the image quality of two-color recording. You can

According to the multi-beam scanning device of the third aspect of the invention, since the two laser beams have different polarization directions, there is a difference in the reflection characteristics of the laser beams by the polarizing means, the image forming means and the like. There is a difference in the light amount characteristic on the photoconductor, but the output intensity of the laser beam can be controlled based on the correction data in consideration of this light amount characteristic, and the two laser beams on the photoconductor can be controlled. The light amount characteristics of can be matched. As a result, the occurrence of density unevenness can be suppressed, and the image quality of two-color recording can be improved.

According to the multi-beam scanning device of the fourth aspect, by switching the polarization separating means between the separation position and the retracted position, the two-color recording and the scanning line pitch of 1/2 of the two-color recording are achieved. Corresponding high-density (double-density) single-color recording or double-speed single-color recording can be easily and easily switched to improve the usability of the multi-beam scanning device.

According to the multi-beam scanning device of the fifth aspect, the exposure energy per unit time on the photoconductor can be appropriately controlled, and the image quality can be improved.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a multi-beam scanning device to which an embodiment of the multi-beam scanning device of the present invention is applied.

FIG. 2 is a diagram showing light amount characteristics of S-polarized beams and P-polarized beams, correction data thereof, and light amount characteristics of P-polarized beams after correction.

3 is an exploded perspective view of a light source unit of the multi-beam scanning device of FIG.

FIG. 4 is an enlarged perspective view of an aperture portion of FIG.

5 is a cross-sectional view of the light source unit of FIG.

FIG. 6 is a front sectional view of an example of a conventional multi-beam scanning device.

[Explanation of symbols]

 10 multi-beam scanning device 11 semiconductor laser drive circuit unit 12 cylinder lens 13 rotating polygon mirror 14 fθ lens 15 polarizing mirror 16, 17 mirror 18 photoconductor 19 synchronization detection sensor 21, 22 semiconductor laser control unit 23 beam intensity correction data memory 30 light source Parts 31, 32 Semiconductor lasers 33, 34 Supports 33a, 34a Holes 35, 36 Screws 37 Bases 38, 39 Collimator lens 40 Aperture plate 41 Beam combining prism 41a Polarization beam splitter surface 41b Inclined surface 42 1/2 wavelength plate 43 Flange member 43a Cylindrical part 43b Groove 48 Aperture 48c Positioning protrusion 49 Holding plate 49a Through hole 49b Groove 49c Screw hole

Claims (5)

[Claims] 1. A light source section which is modulated by write information of different colors and which combines and emits two laser beams having different polarization directions, and two laser beams emitted from the light source section. Deflection means for deflecting in the main scanning direction, polarization separation means for separating the two laser beams deflected by the deflection means, and one laser beam separated by the polarization separation means
A multi-beam scanning device comprising: an image forming unit that scans at different positions on one photoconductor; and a drive control unit that controls a laser beam by the light source unit, wherein the light source unit is at least A laser emitting element that emits two laser beams separated by a predetermined amount in the main scanning direction, a collimator lens that converts each laser beam emitted from the laser emitting element into a parallel light beam, and a collimator lens that converts the laser beam into a parallel light beam. A multi-beam scanning device, characterized in that a beam synthesizing means for synthesizing and emitting the generated laser beams is integrally assembled. 2. The beam combining means combines one of the two laser beams separated by a predetermined amount in the main scanning direction with the other main scanning direction to emit the combined laser beam, and the image forming means One of the laser beams separated by the polarized light separating means is also made incident on a synchronization detecting means provided in the vicinity of the photoconductor, and the drive control means causes the laser based on the detection result of the synchronization detecting means. 2. The multi-beam scanning device according to claim 1, wherein the synchronization timing of the two laser beams emitted by the emitting element is controlled. 3. The drive control means controls the output intensity of one of the two laser beams emitted from the laser emitting element according to the light quantity characteristic of the other laser beam. The multi-beam scanning device according to claim 1 or 2. 4. The light source section emits the two laser beams with their optical axes inclined by a fine angle in the sub-scanning direction, and the polarization separation means emits the laser beams emitted from the light source section. Of the laser beam from the light source unit and separates the laser beam from the light source unit via the image forming unit. When the photoconductor is scanned at different positions, the scanning line pitch corresponding to the fine angle is opened through the image forming means without separating the laser beam from the light source unit when in the retracted position. The multi-beam scanning device according to any one of claims 1 to 3, wherein the photoconductor is scanned in a closed state. 5. The drive control means controls the output intensity of a laser beam emitted from the laser emitting element depending on whether the polarization separation means is at the separation position or the retracted position. The multi-beam scanning device according to claim 4.