JP2005193452A - Optical writing device and digital copying machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical writing device which can eliminate the effects of an offset luminescence by another (ch) during an initializing operation and thereby, can perform a highly precise operation and a digital copying machine. <P>SOLUTION: In the optical writing device which is so designed as to optically write data in a plurality of lines at the same time by simultaneously driving a plurality of semiconductor laser units 7, a writing control ASIC5 is provided which performs the following process: when either one of the semiconductor laser units 7 is lighted and a synchronous detection signal is detected, the lighting is terminated, and next, either one of the remaining semiconductor laser units 7 is lighted and the lighting is terminated when the synchronous detection signal is detected and further, the remaining semiconductor laser units 7 are sequentially switched to a desired quantity of light level by the lighting and the synchronous detection signal. as a preceding stage before switching to a line APC control for maintaining the quantity of light of an individual semiconductor laser unit 7 at a desired value under control. After completing the operation to switch all the semiconductor laser units 7 to a desired quantity of light level by selecting the supply of bias current to the semiconductor laser units 7, the control to switch the operation to the line APC operation is performed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical writing apparatus in which a plurality of semiconductor lasers are simultaneously driven to simultaneously perform optical writing on a plurality of lines, and a digital copying machine incorporating the optical writing apparatus.

In an optical writing apparatus in which a plurality of semiconductor lasers are simultaneously driven to simultaneously perform optical writing on a plurality of lines, the line APC of the remaining semiconductor lasers is synchronized with a synchronization signal obtained by one of the plurality of semiconductor lasers. A method of performing an APC control pull-in operation until control has been proposed (see Patent Document 1).
In a digital copying machine using an optical writing device, a laser chip composed of one light emitting element and one light receiving element (photodiode) is used, and one photoelectric negative feedback loop is provided for one laser chip. It had a semiconductor laser drive control device. Further, as the printing speed increases and the image quality becomes higher, in the configuration having a plurality of laser chips, the control configuration is prepared for the number of laser chips, and each APC control can be performed independently. It was. In the method of increasing the number of laser chips with higher image quality and higher speed, complication of components due to the adjustment of the pitch of the laser emission point, and the reference of the image start position of each channel (channel) There is a problem such as an increase in the speed of the synchronous detection plate.
As means for achieving high speed and high image quality, an LD array in which a plurality of light emitting elements are arranged in a single laser chip has been proposed. In this LD array, a plurality of light emitting elements are arranged at equal intervals, and therefore, the pitch adjustment in the sub-scanning direction is determined by the lens characteristics of the optical system. Can be reduced.
Since this LD array has a special configuration of one light receiving element for a plurality of light emitting elements, it is difficult to simultaneously perform the APC operation of the light emitting elements. Therefore, it is impossible to use the transition operation to the conventional APC operation as it is for a multi-beam writing apparatus using an LD array.
Japanese Patent Laid-Open No. 10-166649

Here, during the sequential initialization operation of the LD array composed of a plurality of light emitting elements and one light receiving element, offset light emission by supplying a bias current may affect the initialization operation of other lasers. In other words, since the offset light emission back beam affects the light receiving element, when performing the initialization operation of any light emitting element, the initialization operation is performed while being influenced by the offset light emission of other LDs. The initialization operation of the selected light emitting element may not be performed correctly.
In LD light emission control, the operation without offset light emission greatly affects the droop. In LDA control, the presence of offset light emission affects other channels. Therefore, on / off of the offset light emission (bias current) Control) needs to be implemented when necessary.
The present invention provides an optical writing apparatus capable of eliminating the influence of offset light emission due to other channels during the initialization operation and capable of performing a highly accurate operation, and a digital copying machine incorporating the optical writing apparatus. For the purpose.

In order to achieve the above object, an invention according to claim 1 is directed to an optical writing apparatus in which a plurality of semiconductor lasers are simultaneously driven to perform optical writing on a plurality of lines simultaneously. As a step before shifting to the line APC control for maintaining the control value, if any one of the plurality of semiconductor lasers is turned on and a synchronization detection signal is detected, the lighting is finished, and then the remaining semiconductor lasers are turned on. Turns on one of them and ends the lighting when a synchronization signal is detected, and sequentially turns the remaining semiconductor lasers to the desired light intensity by lighting and the synchronization signal. Whether or not a bias current is supplied to the semiconductor laser The most important optical writing apparatus having a write control ASIC that performs control to shift to the line APC operation after completing the operation of transitioning all the semiconductor lasers to a desired light amount. And butterflies.
The invention according to claim 2 is mainly characterized by the optical writing apparatus according to claim 1 which can set whether or not to supply a bias current of each semiconductor laser during the line APC operation.
The invention described in claim 3 is mainly characterized by a digital copying machine in which the optical writing device described in claim 1 is incorporated.

  In the optical writing apparatus in which a plurality of semiconductor lasers are simultaneously driven to perform optical writing on a plurality of lines at the same time, as a stage before shifting to line APC control for controlling and maintaining the light amount of each semiconductor laser at a desired value, Turns on when one of the multiple laser diodes is turned on and a synchronization detection signal is detected, then turns on, then turns on one of the remaining semiconductor lasers and turns on when a synchronization signal is detected Then, the process of shifting the remaining semiconductor lasers to the desired light quantity by turning on and synchronizing signals, selecting whether or not to supply a bias current to the semiconductor laser, and changing all the semiconductor lasers to the desired light quantity By providing the write control ASIC for performing control to shift to the line APC operation after completing the above, the intended purpose can be achieved.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a digital copying machine according to an embodiment of the present invention. This configuration is a copying machine 100 as an image processing apparatus, and a contact glass 206 is provided on the upper surface of the copying machine 100. In addition, an automatic document feeder (hereinafter simply referred to as ADF) 201 is provided on the upper side of the copying machine 100, and this ADF 1 is connected to the copying machine 100 via a hinge or the like (not shown) so as to open and close the contact glass 206. Has been. The ADF 201 separates documents one by one from a document tray 202 as a document placing table on which a document bundle composed of a plurality of documents can be placed, and faces the contact glass 206 from the document bundle placed on the document tray 202. The separation / conveying means that conveys the original and the document conveyed toward the contact glass 206 by the separation / conveying means are conveyed / stopped to a reading position on the contact glass 206, and the copy disposed below the contact glass 206 The document that has been read by the reading means (a known exposure lamp 251, mirrors 252, 255, 256, lens 253, CCD 254, etc.) 250 of the machine 100 is unloaded from the contact glass 206. The paper feed motor is driven by an output signal from the controller, and when the paper feed start signal is input from the copying machine 100, the controller drives the paper feed motor forward / reversely. When the paper feed motor is driven in the forward direction, the feed roller 203 rotates in the clockwise direction so that the uppermost original is fed from the original bundle and conveyed toward the contact glass 206. When the leading edge of the document is detected by the document set detection sensor 207, the controller rotates the paper feed motor in reverse based on the output signal from the document set detection sensor 207. This prevents subsequent documents from entering and prevents separation.
Further, when the document set detection sensor 207 detects the trailing edge of the document, the controller counts the rotation pulse of the conveyor belt motor from this detection point, and when the rotation pulse reaches a predetermined value, the controller By stopping the driving and stopping the feeding belt 204, the document is stopped at the reading position of the contact glass 206. Also, when the trailing edge of the document is detected by the document set detection sensor 7, the controller drives the paper feed motor again, separates the subsequent document as described above, and conveys the document toward the contact glass 206. When the pulse of the paper feed motor from the time when the original is detected by the original set detection sensor 207 reaches a predetermined pulse, the paper feed motor is stopped and the next original is put on standby. When the original stops at the reading position of the contact glass 206, the original is read and exposed by the copying machine 100. When this reading and exposure are completed, a signal is input from the copier 100 to the controller. When this signal is input, the controller drives the conveyor belt motor to rotate forward, and the document is transferred from the contact glass 206 by the conveyor belt 216. It is carried out to the discharge roller 205.
As described above, a document bundle placed on the document tray 202 in the ADF 201 with the image surface of the document facing up is pressed from the top document to the contact glass 206 when the print key on the operation unit is pressed. It is fed to a predetermined position. The fed original is read by the reading unit 250 after the image data of the original on the contact glass 206 is discharged to the discharge port A (discharge port at the time of reverse document discharge) by the feeding belt 204 and the reverse driving roller. Further, when it is detected that there is a next document on the document tray 202, it is fed onto the contact glass 206 in the same manner as the previous document.
The transfer sheets stacked on the first tray 208, the second tray 209, and the third tray 210 are fed by the first sheet feeding unit 211, the second sheet feeding unit 212, and the third sheet feeding unit 213, respectively, and are conveyed vertically. The unit 214 is transported to a position where it abuts on the photoreceptor 215. The image data read by the reading unit 250 is written on the photoconductor 215 by a laser from the writing unit 257, and a toner image is formed by passing through the developing unit 227. Then, the toner image on the photosensitive member 215 is transferred while the transfer paper is conveyed by the conveying belt 216 at the same speed as the rotation of the photosensitive member 215. Thereafter, the image is fixed by the fixing unit 217 and conveyed to the paper discharge unit 218. The transfer paper conveyed to the paper discharge unit 218 is discharged to the paper discharge tray 219 when the staple mode is not performed.

  FIG. 2 is a block diagram of the digital copying machine of the present invention. The digital copying machine includes a scanner unit 1 that has a VPU 2 that performs black offset correction, shading correction, and pixel position correction by A / D conversion of a read signal, and an IPU 3 that performs image processing, and a writing control. An ASIC 5, an LD control unit 6 for controlling a semiconductor laser, a printer unit 4 having an LD array 7 for forming electrostatic latent image data on a photosensitive member, a CPU 8 for controlling the entire apparatus, and a control program ROM 9 stored therein, RAM 10 temporarily used by the control program, image memory 11 for storing the read image, operation unit 12 for giving instructions by the user, and internal system for exchanging data between the devices The bus 13, the system bus 13 and the I / F 14 for interfacing with the IPU 3 are configured.

FIG. 3 is a configuration diagram of the printer unit. In addition to the unit shown in FIG. 2, the printer unit 4 includes a deflector 21, an fθ lens 22, a photoreceptor 23, and a photodetector 24. The laser beam emitted forward from the LD array 7 is collimated by a collimator lens (not shown), deflected by a deflector 21 composed of a rotary polygon mirror, and uniformly charged by a charger by an fθ lens 22. Imaged on the surface. The imaging spot is repeatedly moved in the axial direction of the photoconductor 23 by the rotation of the deflector 21, and at the same time, the photoconductor 23 rotates.
The photodetector 24 is provided outside the information writing area, detects the laser beam deflected by the deflector 21, and generates a synchronization detection signal. The write control ASIC 5 applies an information signal to the LD drive unit 31 in the LD control unit 5, and controls the timing by a synchronization signal from the photodetector 24. The LD driving unit 31 drives the LD array 7 by an information signal from the writing control ASIC 5 to form an electrostatic latent image on the photoconductor 23. This electrostatic latent image is developed by a developing device and transferred to a transfer paper or the like by a transfer device.
Further, the laser beam emitted backward from the light emitting unit 32 in the LD array 7 is incident on the light receiving unit 33 and the light intensity thereof is detected, and a light reception signal is supplied to the APC control unit 34. The APC control unit 34 controls the LD driving unit 31 according to the output signal of the light receiving unit 33 to control the output light amount of each light emitting element in the LD array 7 to be constant (APC control). Specifically, the drive power supply of each light emitting element of the LD array 7 is adjusted and held so that the output light amount of each light emitting element becomes constant according to the respective light reception signals. Further, it is determined whether or not the LD emits an offset light according to the bias signal.

FIG. 4 is a block diagram of the write control ASIC. Memory block 41 that performs speed conversion and format conversion on image data from IPU 3, image processing unit 42 that performs image processing on image data from memory block 41, γ conversion on image data from image processing unit 42, P The output data control unit 43 performs processing such as sensor pattern application.
FIG. 5 is a block diagram of the output data control unit of the write control ASIC. A P pattern block 51 for giving a P sensor pattern for placing toner of a certain density on the photoconductor 23 for data acquisition for determining process conditions to data input from the image processing unit 42, and data weight The γ conversion block 52 to be changed, the APC block 53 that gives an image in synchronization with the APC operation timing for keeping the light quantity of the LD constant, the pixel count block 55 that measures the number of light emitting dots of each LD, and the light emission for synchronization detection It consists of an LD on / off block 55 for giving data.
In the P sensor pattern and the APC pattern, the timing in the main scanning sub-scanning direction is determined by the gate signal supplied from the main scanning gate signal generation unit 56. The position of the gate signal can be changed by a register (not shown).

FIG. 6 is a timing chart from the start of the initial operation to the line APC operation according to one embodiment. In this embodiment, an operation using the 4ch LD array 7 is performed.
(1) After turning on the power, the deflector 21 is rotated and the ch1 lighting operation is performed.
(2) When the synchronization signal is obtained twice by the light emission of ch1, the lighting of ch1 is finished and the lighting operation of ch2 is started.
(3) When the synchronization signal is obtained twice by the light emission of ch2, the lighting of ch2 is finished and the lighting operation of ch3 is started.
(4) The ch3 → ch4 light emission is performed, and the initial operation in which the synchronization signal is obtained twice by the light emission of ch4 is completed.
Up to this point, no bias current is supplied to each light emitting element. Thereafter, when the initial operation is completed and a standby state is entered, a sequential line APC operation for continuously maintaining a desired light amount is performed. No bias current is supplied during the line APC operation period. Outside the line APC operation period (effective image area, etc.), a bias current is supplied. Shifting to line APC control synchronized with the synchronization signal while obtaining the synchronization signal at ch1.
The internal operation of the write control ASIC 5 is that the initial operation start flag is set during the initial operation period, and the initial operation start flag is reset when the initial operation is completed. By monitoring, the bias current can be switched on / off.
In this embodiment, the timing for sequentially operating the line APC operation and the bias current supply operation is cleared by the synchronization detection signal used in the write control ASIC 5, and the count UP operation is performed by the write CLK. It is created using a scan counter.
As an actual operation, it is set in advance how many times the main scanning counter is turned on and off, and a gate signal is output by comparing with the set value. The setting value can be changed in a special mode called SP mode, which is not particularly described, in which various setting data can be changed.

1 is a schematic configuration diagram of a digital copying machine according to an embodiment of the present invention. 1 is a block diagram of a digital copying machine of the present invention. It is a block diagram of a printer part. It is a block diagram of write control ASIC. It is a block diagram of the output data control part of write-control ASIC. FIG. 6 is a timing diagram from the start of an initial operation to a line APC operation according to an embodiment.

Explanation of symbols

1 Scanner unit 4 Printer unit 5 Write control ASIC
6 LD controller 7 LD array (semiconductor laser)

Claims (3)

  In the optical writing apparatus in which a plurality of semiconductor lasers are simultaneously driven to perform optical writing on a plurality of lines at the same time, as a stage before shifting to line APC control for controlling and maintaining the light amount of each semiconductor laser at a desired value, Turns on when one of the multiple laser diodes is turned on and a synchronization detection signal is detected, then turns on, then turns on one of the remaining semiconductor lasers and turns on when a synchronization signal is detected Then, the process of shifting the remaining semiconductor lasers to the desired light quantity by turning on and synchronizing signals, selecting whether or not to supply a bias current to the semiconductor laser, and changing all the semiconductor lasers to the desired light quantity An optical writing apparatus comprising a writing control ASIC for performing control to shift to a line APC operation after completing the above.   2. The optical writing apparatus according to claim 1, wherein whether or not a bias current is supplied to each semiconductor laser can be set during the line APC operation.   A digital copying machine in which the optical writing device according to claim 1 is incorporated.

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