JP3824566B2 - Optical writing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical writing device in a digital color image forming apparatus using a plurality of semiconductor lasers.
[0002]
[Prior art]
In recent years, digital color copying machines have become widespread and color copying has been performed for various purposes. This digital color copying machine generally has a configuration of a digital color image forming apparatus using an optical writing device of a type in which light of a semiconductor laser (hereinafter referred to as LD) is written on a photosensitive member.
[0003]
In this image forming apparatus, in response to the demand for higher printing speed and higher image quality, a plurality of image forming units are arranged in a row, and each of the four colors is formed separately by the plurality of image forming units. A tandem configuration that simultaneously forms four colors in one scan has been proposed (see, for example, Japanese Patent Laid-Open No. 2000-015870).
[0004]
Color image formation by semiconductor laser writing is performed by controlling the lighting of the LD according to the image data of each color component, and performing main and sub scanning on the surface of the image carrier (photosensitive body) for each color by the light beam emitted from the LD. However, this is done by superimposing the images of the respective color components.
FIG. 1 shows an overall configuration of a general digital color copying machine. An automatic document feeder (ADF) 100, an image reading unit 200, and an image forming unit 300 are configured to read a document conveyed to an image reading position by the ADF 100 with the image reading unit 200, and read image data is an image forming unit. Transfer to 300 to form an image.
[0005]
In the image reading unit 200, the reflected light of the original on the original glass 208 irradiated by the exposure lamp 201 is guided to the lens 203 by the three mirror groups 202 and forms an image on the CCD sensor 204. The exposure lamp 201 and the first mirror are scanned over the entire surface of the original on the original glass 208 by scanning with a scanner motor 209 in the direction of the arrow at a speed V corresponding to the magnification. The position of the exposure lamp 201 is calculated and controlled by the scanner home sensor 210 and the amount of movement (the number of motor steps) from the home position. The reflected light of the original incident on the CCD sensor 204 is converted into an electric signal in the sensor and subjected to analog processing, A / D conversion, and digital image processing of the electric signal by the image processing circuit 205, and then sent to the image forming unit 300. It is done.
[0006]
In the image forming unit 300 having the tandem configuration, the image data sent from the image reading unit 200 is converted into printing data of cyan (C), magenta (M), yellow (Y), and black (K). To an image writing control unit (not shown). The image writing control unit for each color emits a laser in accordance with the electrical signal of the image data sent thereto, scans the light one-dimensionally by the polygon mirror 301, and the image forming units 302c, 302m, 302y, The photoconductor in 302k is exposed. The image forming units 302c, 302m, 302y, and 302k are arranged in a line vertically along the paper transport direction of the paper transport belt 304, and each image forming unit performs an electrophotographic process centering on a photoreceptor. Necessary elements are arranged. Each image forming process is continuously performed by rotating the photoconductors for C, M, Y, and K clockwise. These image forming units necessary for image formation are integrated for each process, and the latent image on the photoreceptor in the image forming unit is developed by each color developing device. The toner image on the photosensitive member is transferred onto the sheet on the sheet conveying belt 304 by the transfer chargers 303c, 303m, 303y, and 303k installed in the sheet conveying belt 304 so as to face the above-described photosensitive members.
[0007]
The transfer paper is supplied from the paper cassette groups 310a, 310b, and 310c to the transport unit by paper feed rollers 312 attached to the paper cassettes 310a, 310b, and 310c. The sheet supplied to the conveyance path is sent to the sheet conveyance belt 304 by the conveyance roller pair 313, and after the sheet conveyance timing is adjusted to the image data by the registration sensor 306, the sheet is supplied to each image forming unit. The transfer paper onto which the toner image has been transferred is fixed with toner by a fixing roller and discharged onto a paper tray, completing the color image forming process. The sheet transport belt 304 can be retracted from the C, M, and Y image forming units by the behavior of the belt retracting roller 305, and the sheet transport belt 304 and the photosensitive member can be brought into a non-contact state. Therefore, since the driving of the C, M, and Y imaging units can be stopped during monochrome image formation, wear of the photosensitive member and peripheral processes can be reduced.
[0008]
FIG. 2 shows a configuration in which the laser optical system including the polygon mirror 301 is viewed from above in the image forming unit 300. The LD is configured by a 1 polygon 4 beam system. When each color photoconductor is exposed with a laser, C and M, which are the drawing colors on the A side, are exposed and scanned in the reverse direction with respect to the drawing colors Y and K on the B side. Mirror image processing is performed in the main scanning direction of the two colors on the A side in the course of the above processing.
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-015870
[Problems to be solved by the invention]
Recently, there has been a demand for further speeding up of processing speed in the image forming apparatus, and thus speeding up of each processing step has been promoted. Among them, the image data writing processing to the photoconductor in the image forming step is rate limiting. A problem has occurred.
[0010]
The present invention has been made in view of the above-described problems in the prior art. In the image forming apparatus, it is possible to speed up the writing of image data onto the photosensitive member, and the image facing the polygon mirror becomes an appropriate image, and the parts It is an object of the present invention to provide an optical writing device that can be shared .
[0011]
[Means for Solving the Problems]
In order to solve the problem, the inventor made a study based on the idea of speeding up image data writing by forming LDs for each color into a plurality of channels and writing a plurality of lines at a time on the photosensitive member.
[0012]
However, if only two channels are used, for example, as shown in FIG. 3, the incident positions P1a of the light LD1a and LD2a of the image formation data emitted from one side (A side) of the polygon mirror 3 onto the photosensitive drum 7a. , The incident positions P1b and P2b of the light LD1b and LD2b of the image data emitted from the other side (B side) on the opposite side with respect to P2a are in the drum rotation direction (sub-scanning direction, paper conveyance) Direction), and the B side image does not become a proper image. As a countermeasure, a configuration in which the arrangement on the B side of the LD channel is reversed with respect to the A side can be considered, but with this, the writing unit is different on the A side and the B side. This is not preferable because the number of parts to be managed increases because the parts cannot be made common.
Accordingly, the inventor has focused on the editing process stage of the image data supplied to the LD, and has made the present invention through intensive studies.
[0013]
That is, the optical writing device according to the invention of claim 1 provided in order to solve the above problems, and one polygon mirror, a plurality of semiconductor laser units disposed across the polygon mirror, the semiconductor laser unit One-to-one correspondence to each, a plurality of mirror groups on which light from the semiconductor laser unit respectively enters through the mirror surface of the polygon mirror, and one-to-one correspondence to each of the semiconductor laser units, one row A plurality of photosensitive drums arranged in
The semiconductor laser unit includes a semiconductor laser device having two semiconductor lasers for each color, an image editing unit that edits and outputs image data to these semiconductor lasers, and the semiconductor laser based on an output signal from the image editing unit. A control unit to control, and can draw two lines at the same time,
The two lines of laser light emitted from each semiconductor laser unit are reflected by a mirror surface on the polygon mirror and a mirror group corresponding to each semiconductor laser unit, and an image is written on the surface of the corresponding photosensitive drum. An optical writing device that forms one image by the plurality of photosensitive drums,
In the image editing unit of another semiconductor laser unit in which light emitted from the surface opposite to the surface from which light from one semiconductor laser unit is reflected on the polygon mirror among the plurality of semiconductor laser units is reflected in the semiconductor laser unit The image data of the odd lines and the image data of the even lines of the image data for each sub-scan line to the apparatus are switched.
[0014]
As a result, a plurality of light beams from one semiconductor laser unit can be used, so that it is possible to increase the speed of writing image data to the photoconductor. In addition, it is possible to have a configuration in which image data supplied to each semiconductor laser device in one semiconductor laser unit can be reflected in an arbitrary line. The line can be optimized.
[0016]
In addition, since the image data supplied to each semiconductor laser device in the semiconductor laser unit in which the incident position of light on the photosensitive drum is reversed can be replaced, writing is performed corresponding to the front and back surfaces of the polygon mirror. A regular image can be formed in the drum rotation direction without having a unit individually, and it is possible to speed up the writing of image data to the photoconductor.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
The configuration of an optical writing apparatus according to an embodiment of the present invention will be described below with reference to the drawings. The present invention is applied as a writing device of a digital color copying machine having a tandem configuration as shown in FIG.
FIG. 4 shows the details of the configuration of the optical system of the optical writing device in one embodiment of the optical writing device according to the present invention. A laser beam for four colors is swayed by one polygon mirror 3 and an image of each color is written on a photosensitive member (not shown). Here, a plurality of LDs (two) using a polygon mirror 3 in common. There are four LD units 1k, 1y, 1m, and 1c equipped with a total of eight laser beams (one polygon eight beam system).
[0018]
Specifically, as shown in FIG. 4B, the polygon mirror 3 has two upper and lower mirror surfaces 3u and 3d, and beams from the LD units 1c and 1k are applied to the mirror surface 3u and the LD units 1m and 1y. Is directed to the mirror surface 3d via the mirrors 2a and 2b. As a result, as shown in FIG. 4 (a), the beam from the LD units 1m and 1c is distributed to the A side and the beams from the LD units 1k and 1y are distributed to the B side around the polygon mirror 3, and then the fθ lens. And a total of eight light beams of four colors for cyan (C), magenta (M), yellow (Y), and black (K) are reflected by a reflecting mirror group (not shown). The photoconductor (not shown) is scanned.
[0019]
In the image writing optical system of this example, the main scanning direction of the beam is reversed between the A side and the B side, and in FIG. Is done. Therefore, on the A side, the upper side in FIG. 2 is the leading end (start position) of writing, and on the B side, the lower side is the leading end (start position) of writing.
[0020]
A predetermined resist is set for each color from the reference position provided on the scanning line in order to write the image in a state where no color misalignment occurs between the images of the respective colors. The reference position of the resist is a position where the synchronization detector 4 detects the beam. A total of four synchronization detectors 4au, 4ad, 4bu, and 4bd are provided on the A side and B side, respectively, in front of the writing tip position in the main scanning direction, and each generates a synchronization detection signal when a beam is incident.
[0021]
FIG. 5 is a block diagram showing a schematic configuration relating to image data processing. The image reading unit V1 performs color separation, A / D conversion on a signal obtained by reading a document image, and performs a VPU (Video Processing Unit) 400 that performs offset correction, shading correction, and pixel position correction, and an IPU (Image Processing) that performs image processing. Unit) 401. The LD unit 1 includes a writing image editing device (GAVD) 402 that edits image data from the IPU 401, an LD control unit 403 that controls a semiconductor laser based on a signal from the GAVD 402, and electrostatic latent image data on the drum. And an LD 404 that performs the image formation. The image reading unit V1 and the LD unit 1 store a control program and a CPU 405 that executes control of the entire apparatus based on a user instruction from the operation unit 411 via an interface (I / F) unit 410. Data is exchanged between the ROM 406, the RAM 407 temporarily used by the control program, and the internal system bus 409 connected to the image memory 408 for storing the read image.
[0022]
Image data separated into cyan (C), magenta (M), yellow (Y), and black (K) print data in the image reading unit V1 is sent to the GAVD 402 for each color, and information necessary for image formation After (APC control, pixel count, P sensor pattern creation, etc.) is given, LD lighting data is supplied to the LD control and LD light emission is performed based on this.
[0023]
FIG. 6 is a schematic diagram of the GAVD 402, the LD control unit 403, and the LD 404 constituting the LD unit 1. The LD driving unit 501 drives the LD 404 to emit a laser beam based on the information signal from the GAVD 4. The laser beam emitted forward from the LD 404 is collimated by a collimator lens (not shown), deflected by the polygon mirror 3, and imaged on the surface uniformly charged by the charger of the photosensitive drum 7 by the fθ lens 6. The imaging spot is repeatedly moved in the axial direction on the photosensitive drum 7 by the rotation of the polygon mirror 3, and at the same time, the photosensitive drum 7 is rotated to form an electrostatic latent image. Next, the electrostatic latent image is developed by a developing device and transferred to a transfer paper or the like by a transfer device. The synchronization detector 4 is provided outside the information writing area and detects the laser beam deflected by the polygon mirror 3 to generate a synchronization detection signal. The GAVD 402 applies the information signal to the LD drive unit 501 in the LD control unit 403, and the application timing is taken from the synchronization detection signal.
[0024]
Further, a laser beam emitted backward from the light emitting unit 503 in the LD 404 is incident on a light receiving unit (PD) 504 and its light intensity is detected, and a light reception signal thereby is generated as an automatic output control unit (Auto Power Control (APC)). Control unit) 502. The APC control unit 502 feedback-controls the LD driving unit 501 in accordance with the output signal of the light receiving unit (PD) 504 to control the output light amount of each light emitting element of the LD 404 to be constant (APC control). Specifically, the drive power supply of each light emitting element of the LD 404 is adjusted and held so that the output light amount of each light emitting element becomes constant by the respective light reception signals.
[0025]
FIG. 7 is a schematic configuration diagram of the GAVD 402 that forms the basis of the present invention. Memory block 601 that performs speed conversion and format conversion on image data from IPU 401, image processing unit 602 that performs image processing on image data from memory block 601, and data that performs line-to-line replacement of image data from image processing unit 602 A replacement processing unit 603 and a P sensor pattern for applying a certain density of toner on the photosensitive drum to obtain data for determining process conditions are added to the image data from the data replacement processing unit 603. A pattern block 604, a γ conversion block 605 that changes the weight of data, an APC block 606 that gives an image in synchronization with the operation timing of APC control for keeping the light quantity of the LD constant, and the number of light emitting dots of each LD A pixel count block 607 for measuring the emission and emission data for synchronization detection And a Don / off block 608.
[0026]
Of these, the part particularly related to the present invention is a data replacement processing unit 603, which replaces image data of a plurality of lines in the sub-scanning direction coming from the upstream with arbitrary lines. .
[0027]
Example 1
8 and 9 show Embodiment 1 of the present invention. FIG. 8 shows that when the LD unit 1 for each color has two channels of LD 404, the AAV and B side two channel LDs (LD1a and LD2a, LD1b in FIG. 4) generated by the GAVD 402 for one main scanning operation. And the contents of the lighting signal input to LD2b).
Here, as the lighting signal for the LD on the A side, the preceding line is formed on the photosensitive drum by the LD 1a, and therefore, a lighting signal for image data of odd-numbered lines from the first line is input to the LD 1a. A light-up signal of image data of even-numbered lines after the second line is input to the LD 2a. On the other hand, as a lighting signal to the LD on the B side, the arrangement is reverse to that in the case of the A side, and the preceding line is formed on the photosensitive drum by the LD 2b. The line image data lighting signal is input, and the image data lighting signals of the second and subsequent lines are input to LD1b.
[0028]
As shown in FIG. 9, this is a signal processing stage in the data replacement processing unit 603 in the B-side GAVD 402, in which the odd-line image data and the even-line image data are replaced, that is, the image data is inverted. As a result, the image data for each line output from the LD unit 1 on the B side is replaced as described above.
As a result, as shown in FIG. 3, the irradiation position of the plurality of beams emitted from the B-side LD unit 1 onto the photosensitive drum 7b is the plurality of beams from the A-side LD unit 1 in the sub-scanning direction. Therefore, the electrostatic latent image formed on each of the photosensitive drums 7a and 7b with the LD control system mounted substrate having the same configuration on both the A and B sides is opposite to the incident position on the photosensitive drum 7a. Can be the same.
[0029]
(Example 2)
FIG. 10 shows a second embodiment of the present invention. In the case where the LD unit 1 for each color has a 4-channel LD 404, in the signal processing stage in the data replacement processing unit 603 in the GAVD 402, not only the front-rear switching between lines but also an arbitrary line image on an arbitrary transfer line. The data is reflected. As a result, channel replacement on the GAVD side is possible for any LD mechanical layout.
[0030]
【The invention's effect】
With the optical writing device according to the first aspect, a plurality of lights from one semiconductor laser unit can be made, so that it is possible to increase the speed of writing image data to the photosensitive member. In addition, it is possible to have a configuration in which image data supplied to each semiconductor laser device in one semiconductor laser unit can be reflected in an arbitrary line. The line can be optimized.
[0031]
Since the image data supplied to each semiconductor laser device in the semiconductor laser unit in which the incident position of the light on the photosensitive drum is reversed can be replaced, the writing unit is provided corresponding to the front and back opposing surfaces of the polygon mirror. A regular image can be formed with respect to the drum rotation direction without having it individually, and it is possible to increase the speed of image data writing to the photoconductor.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an overall configuration of a general digital color copying machine.
FIG. 2 is a diagram showing a schematic configuration of a conventional laser optical system.
FIG. 3 is a diagram showing an outline of the configuration of a laser optical system when an LD unit has a two-channel LD.
FIG. 4 is a block diagram showing an outline of a laser optical system in an embodiment of an optical writing device according to the present invention.
FIG. 5 is a block diagram showing a schematic configuration relating to image data processing in an embodiment of an optical writing device according to the present invention;
FIG. 6 is a schematic diagram of a GAVD, an LD control unit, and an LD 404 constituting an LD unit in an embodiment of an optical writing device according to the present invention.
FIG. 7 is a schematic configuration diagram of a GAVD in an embodiment of an optical writing device according to the present invention.
FIG. 8 is a schematic diagram illustrating a lighting signal pattern input to a two-channel LD of the optical writing apparatus according to the first embodiment of the present invention.
FIG. 9 is a schematic diagram illustrating a flow of image data in the first embodiment of the optical writing device according to the invention.
FIG. 10 is a schematic diagram showing a flow of image data in the optical writing apparatus according to the second embodiment of the present invention.
[Explanation of symbols]
1, 1k, 1y, 1m, 1c LD unit 2, 2a, 2b, 51a, 51b, 52a, 52b, 53a, 53b Mirror 3, 3u, 3d, 301 Polygon mirror 4, 4a, 4b, 4au, 4ad, 4bu, 4bd synchronous detector 6 fθ lenses 7, 7a, 7b photosensitive drums LD1a, LD2a, LD1b, LD2b, 404 Semiconductor laser device (LD)
P1a, P2a, P1b, P2b Laser beam incident position V1 Image reading unit 400 VPU
401 IPU
402 Written image editing device (GAVD)
403 LD control unit 405 CPU
406 ROM
407 RAM
408 Image memory 409 System bus 410 Interface unit 411 Operation unit 501 LD drive unit 502 Automatic output control unit (APC control unit)
503 Light emitting unit 504 Light receiving unit 601 Memory block 602 Image processing unit 603 Data replacement processing unit 604 Pattern block 605 γ conversion block 606 APC block 607 Pixel count block 608 LDon / off unit

Claims (1)

And one of the polygon mirror, a plurality of semiconductor laser units disposed across the polygon mirror, the corresponding semiconductor laser unit respectively one-to-one, a mirror of the polygon mirror light respectively from the semiconductor laser unit A plurality of mirror groups incident through a surface, and a plurality of photosensitive drums corresponding to each of the semiconductor laser units on a one-to-one basis and arranged in a line;
The semiconductor laser unit includes a semiconductor laser device having two semiconductor lasers for each color, an image editing unit that edits and outputs image data to these semiconductor lasers, and the semiconductor laser based on an output signal from the image editing unit. 2 lines can be drawn at the same time.
The two lines of laser light emitted from each semiconductor laser unit are reflected by a mirror surface on the polygon mirror and a mirror group corresponding to each semiconductor laser unit, and an image is written on the surface of the corresponding photosensitive drum. An optical writing device that forms one image by the plurality of photosensitive drums,
In the image editing unit of another semiconductor laser unit in which light emitted from the surface opposite to the surface from which light from one semiconductor laser unit is reflected on the polygon mirror among the plurality of semiconductor laser units is reflected in the semiconductor laser unit An optical writing apparatus, wherein image data of odd lines and image data of even lines of image data for each sub-scanning line to the apparatus are switched.

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