JP2010194843A - Optical writing device, image forming device, and method for controlling optical writing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical writing device using a plurality of light emitting elements, an image forming device, and a method for controlling optical writing. <P>SOLUTION: A laser printer 1 corrects and controls light emission quantities of laser diodes LDa to LDd simultaneously lit based on light quantities correcting values corresponding to the laser diodes LDa to LDd simultaneously lit referring to a memory 32 recording the light quantity correcting values which are correcting information for correcting light quantity differences between the light emission quantities when individually lighting the plurality of laser diodes LDa to LDd and the individual light emission quantities of the laser diodes LDa to LDd which are simultaneously lit when combining and simultaneously lighting the plurality of laser diodes LDa to LDd in the case of simultaneously lighting the plurality of laser diodes LDa to LDd which can be individually lit and turned off. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical writing apparatus, an image forming apparatus, and an optical writing control method, and more particularly, to an optical writing apparatus using a plurality of light emitting elements, an image forming apparatus equipped with the optical writing apparatus, and an optical writing control method.

  As an image forming apparatus such as a digital copying machine, a digital printer, and a digital facsimile apparatus, a high-quality image can be recorded at a high speed. Therefore, a laser beam emitted from a laser diode using a laser diode (semiconductor laser) as a light source. 2. Description of the Related Art An electrophotographic image forming apparatus that forms an electrostatic latent image on a photosensitive member by using a toner and develops the electrostatic latent image with toner to form an image has become widespread.

  In such an electrophotographic image forming apparatus using a laser diode, it is necessary to keep the output of the laser diode constant in order to improve the image quality. Conventionally, APC (Auto Power Control; An automatic light output control) circuit is used to keep the output of the laser diode constant.

  In other words, since the light output characteristics of a laser diode are sensitive to changes in ambient temperature, even if the laser diode is driven with a constant current, the light output fluctuates due to changes in ambient temperature or self-heating. . In order to keep this optical output fluctuation constant, a photodiode that monitors the optical output of the laser diode is incorporated in the laser diode package, and the drive current of the laser diode is feedback controlled based on the detection result of the photodiode. Thus, the light output of the laser diode is controlled to be constant.

  This APC includes an initial APC performed during a predetermined period before image formation and a line APC performed for each scan, and both are performed using a period during which image formation is not performed.

  In recent years, there has been an increasing demand for higher speed and higher image definition in image forming apparatuses. In order to meet these demands, the rotational speed of a polygon mirror (rotating polyhedron) that deflects and scans a laser beam. However, the rotational speed of the polygon mirror is limited by the material of the bearing portion of the polygon motor, and there is a problem that the cost and size increase as the rotational speed increases.

  Therefore, conventionally, a plurality of light sources (laser diodes) arranged at predetermined intervals in the sub-scanning direction are mounted, and an image that achieves the demand for high speed and high definition without increasing the rotational speed of the polygon mirror. A forming apparatus is provided. That is, in such an image forming apparatus, a plurality of lines (n lines) are simultaneously written by simultaneously scanning the photosensitive member with laser beams from a plurality of light sources by one scanning of the scanning optical system.

  Even in such an image forming apparatus equipped with a plurality of light sources, since the light output characteristics of the laser diode as the light source are sensitive to changes in ambient temperature, APC using a photodiode is performed. In this APC, APC is performed by emitting a sample signal for each channel sequentially from a laser diode (see Patent Document 1).

  However, although the APC in the case of the multi-beam method has been described in the above prior art, this APC takes into account that the light source (laser diode) is affected by changes in the ambient temperature and the like. A process is performed in which the amount of light emitted from the light source is sampled at a timing other than the time of formation, and the amount of light is adjusted in accordance with the light source that is turned on when image formation starts.

  However, in the image forming apparatus, even when a plurality of light sources are used, the power source of the light source driving circuit and the power source of the light source itself are supplied from a single power supply unit common to the image forming apparatus due to cost.

  On the other hand, in an image forming apparatus using a plurality of light sources, the lighting timing of each light source is independently performed by image data, and when the lighting timing of each light source is controlled independently, a plurality of light sources are When power is supplied to the light source, the driving current of the light source and the current consumption of the light source driving circuit change according to the number of lighting of the light source. When the current consumption of the image forming apparatus changes, a voltage drop occurs even if it is very small due to the impedance of a transmission line such as a harness that supplies power from the power supply unit to the light source or the light source drive circuit. Therefore, depending on the number of light sources that are turned on simultaneously, the power supply voltage supplied from the power supply unit to the light source drive circuit and the light source itself changes, the light source drive current changes slightly, and the amount of light emitted from the light source changes, Image quality deteriorates.

  In order to solve this problem, it is possible to provide a dedicated power supply unit for each of the plurality of light sources, or provide a regulator for each light source of the light source driving circuit. Providing a plurality has the problem that the number of parts increases and the cost increases. When a regulator is provided, the regulator generally has a smaller output voltage than the input voltage, and therefore, it is necessary to increase the voltage on the input side of the regulator. However, in general, a power source voltage of a light source driving circuit such as an LD driving circuit is about DC5V, and DC5V is used in other circuit portions of the image forming apparatus, but a regulator is provided in the light source driving circuit. It is necessary to supply a power supply voltage of about DC7V higher than DC5V to the input side of the regulator. As a result, there is a problem that the configuration of the power supply unit becomes complicated and the cost of the power supply unit is high. In particular, in the case of a color image forming apparatus, there is a problem that a power supply unit or a regulator for light sources for four colors of black, magenta, cyan, and yellow is separately required, and the cost is further increased. Such problems tend to increase as the demand for higher speed and higher definition of the image forming apparatus increases and the demand for an increase in the number of light sources increases.

  Accordingly, the present invention provides an optical writing device, an image forming apparatus, and optical writing control that control the light emission amount of each light emitting element to be lit at a target light amount inexpensively and appropriately without being affected by the number of light emitting elements that are simultaneously turned on. It aims to provide a method.

  In order to achieve the above object, the present invention provides a plurality of light emitting elements that are individually turned on when the plurality of light emitting elements are simultaneously turned on and off when the light emitting elements are individually turned on / off with a predetermined light amount. Correction information storage for storing correction information for correcting the light amount difference between the light emission amount when the light is turned on and the individual light emission amounts of the light emitting elements that are simultaneously turned on when a plurality of the light emitting elements are simultaneously turned on With reference to the means, based on the correction information corresponding to the light emitting elements that are simultaneously turned on, the light emission quantity of the light emitting elements that are simultaneously turned on is corrected and controlled.

  In addition, the present invention outputs a light amount control signal for designating the light emission amount of the light emitting element for each light emitting element to be turned on to the element driving means for driving the light emitting element to be turned on / off, and the correction of the correction information storage means The light quantity control signal for the light emitting elements to be turned on simultaneously based on information may be corrected to correct and control the light quantity of the light emitting elements.

  Furthermore, the present invention includes a light emission amount detecting means for detecting a light emission amount of the light emitting element and outputting a light amount detection signal corresponding to the light emission amount, and driving the plurality of light emitting elements independently, The light emitting elements are combined and driven to light simultaneously, and the correction information is acquired and stored in the correction information storage unit based on the light amount detection signal detected by the light emission amount detection unit during the single lighting and the simultaneous lighting. May be a feature.

  According to the present invention, when a plurality of light emitting elements are turned on at the same time, the amount of light that is reduced compared to when the light emitting elements are turned on alone can be corrected, which is influenced by the number of light emitting elements that are turned on simultaneously. Without being necessary, the amount of light emitted from each light-emitting element to be lit can be controlled at a low cost and appropriately to the target amount of light.

1 is a schematic configuration diagram of a main part of a laser printer to which an embodiment of the present invention is applied. The principal part perspective view of an optical writing part. The principal part block block diagram of a laser printer. Explanatory drawing of the light quantity correction process at the time of simultaneous lighting. The principal part block block diagram of the laser printer provided with four laser diodes. Explanatory drawing of the light quantity correction process when three laser diodes light simultaneously. The principal part block block diagram of the laser printer of 2nd Example.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, since the Example described below is a suitable Example of this invention, various technically preferable restrictions are attached | subjected, However, The range of this invention is unduly limited by the following description. However, not all the configurations described in the present embodiment are essential constituent elements of the present invention.

  1 to 7 are diagrams showing an embodiment of an optical writing device, an image forming apparatus, and an optical writing control method of the present invention. FIG. 1 is an optical writing device, an image forming apparatus, and an optical writing control of the present invention. It is a principal part schematic block diagram of the laser printer 1 to which one Example of the method is applied.

  1, the laser printer 1 includes an image forming unit 2 and a fixing unit 3, a main control unit 30, an LD control unit 40, a power supply unit 50, and an LDA 60 shown in FIG. An image processing unit that performs necessary image processing, a paper feeding unit that supplies paper to the image forming unit 2, and a paper discharge unit that discharges paper that has been image-formed by the image forming unit 2 and fixed by the fixing unit to a paper discharge tray A data receiving unit for receiving print data from an external device (personal computer, scanner, etc.), an operation display unit having operation keys for setting various operation modes of the laser printer 1 and a display for displaying various information, etc. ing.

  The image forming unit 2 includes a charging unit 11, an optical writing unit 12, a developing unit 13, a transfer unit 14, a separation unit 15, a cleaning unit 16, and the like around the photoconductor 10 that is driven to rotate. After the photosensitive member 10 to be driven is uniformly charged by the charging unit 11, an electrostatic latent image is formed on the photosensitive member 10 by irradiating the photosensitive member 10 with a laser beam from the optical writing unit 12. The image forming unit 2 forms a toner image by applying toner (developer) to the photosensitive member 10 on which the electrostatic latent image is formed by electrostatic force in the developing unit 13, and forms a toner image on the photosensitive member 10 by the transfer unit 14. The toner image is transferred from the paper supply unit to the paper fed between the photoconductor 10 and the transfer unit 14 through the paper supply path 17, and the paper on which the toner image is transferred by the separation unit 15 is transferred to the photoconductor 10. And is conveyed to the fixing unit 3. The fixing unit 3 includes a heating roller that is rotated and heated to a predetermined fixing temperature, a pressure roller that contacts the heating roller and rotates together with the heating roller, a heater that heats the heating roller to a predetermined fixing temperature, and the like. The sheet on which the toner image is transferred is conveyed while being heated and pressurized by a heating roller and a pressure roller, and the toner image is fixed on the sheet to form an image. Then, the image forming unit 2 discharges the photoconductor 10 after the transfer of the toner image by the cleaning unit 16 to clean the residual toner, and then uniformly charges the charging unit 11 to form an image again. .

  As shown in FIG. 2, the optical writing unit 12 includes an LD (laser diode) unit 21, a polygon mirror 22, an fθ lens 23, a reflection mirror 24, a synchronous reflection mirror 25, a synchronous detection element 26, and the like.

  The LD unit 21 is mounted on an LD control board, and includes an LDA (laser diode array) 60 shown in FIG. 3 and a collimating lens (not shown). As shown in FIG. 3, the LDA 60 includes a plurality (two in this embodiment) of laser diodes (light emitting elements) LDa and LDb and a photodiode PD. The LD unit 21 includes the laser diode LDa of the LDA 60. The divergent laser beam emitted from the LDb is converted into a parallel laser beam by a collimating lens, and irradiated to the polygon mirror 22.

  The polygon mirror 22 is driven to rotate at a high speed at an angular velocity corresponding to the image density of the laser printer 1, deflects the laser beam incident from the LD unit 21 in the main scanning direction (direction indicated by an arrow in FIG. 2), and fθ lens 23. Reflect on.

  The fθ lens 23 reflects the laser beam reflected and deflected by the polygon mirror 22 by the reflection mirror 24, forms an image on the photosensitive member 10, and forms an image on the scanning line of the laser beam of the photosensitive member 10. The light is also incident on the synchronous reflection mirror 25 disposed close to the position outside the region, and the synchronous reflection mirror 25 reflects the incident laser beam to the synchronous detection element 26. For example, a photodiode is used as the synchronization detection element 26, and when a laser beam is incident, a synchronization detection signal that is a pulse output is output to the LD drive circuit units 41a and 41b of the LD control unit 40 shown in FIG. To do. Based on the synchronization detection signal input from the synchronization detection element 26, the LD drive circuit units 41a and 41b determine an effective scanning period that is a period during which an image is written on the photoconductor 10.

  As shown in FIG. 3, the laser printer 1 includes a main control unit 30, an LD control unit 40, a power supply unit 50, and the like. The power supply unit 50 supplies power to the main control unit 30 and the LD control unit 40 through a transmission line 70. Supply voltage and power supply current. The transmission line 70 from the power supply unit 50 to the main control unit 30 and the LD control unit 40 has an impedance of about several mΩ. The optical writing unit 12, the main control unit 30, and the LD control unit 40 having the LDA 60 function as an optical writing device as a whole.

  The main control unit 30 includes a CPU 31, a memory 32, an LDa control unit 33 a, an LDb control unit 33 b, and the like, and a power supply voltage / power supply current is supplied from the power supply unit 50 through the transmission line 70. The memory 32 stores light amount correction values when the laser diodes LDa and LDb of the LDA 60 are individually lit and simultaneously lit, and the basic control program of the laser printer 1, the optical writing control program of the present invention, and the necessary system. Data etc. are memorized. The main control unit 30 controls each unit of the laser printer 1 based on a program in the memory 32 to execute basic processing as the laser printer 1 and executes the optical writing control method of the present invention.

  That is, the laser printer 1 includes a ROM, an EEPROM (Electrically Erasable and Programmable Read Only Memory), an EPROM, a flash memory, a flexible disk, a CD-ROM (Compact Disc Read Only Memory), a CD-RW (Compact Disc Rewritable), a DVD ( An optical writing control program for executing the optical writing control method of the present invention recorded on a computer-readable recording medium such as a digital video disk (SD), a secure digital (SD) card, or an MO (Magneto-Optical Disc) is read. By being introduced into the memory 32, it is constructed as an image forming apparatus provided with an optical writing device that executes an optical writing control method that performs inexpensive and appropriate light quantity adjustment according to laser diodes LDa and LDb that are simultaneously turned on later. Yes. This optical writing control program is a computer-executable program written in a legacy programming language such as assembler, C, C ++, C #, Java (registered trademark) or an object-oriented programming language, and is stored in the recording medium. And can be distributed.

  The LDa control unit 33a outputs an LDa lighting control signal for controlling turning on / off of the laser diode LDa and an LDa light quantity control signal for controlling the light quantity of the laser diode LDa based on the image data under the control of the CPU 31. It outputs to the drive circuit part 41a.

  The LDb control unit 33b outputs an LDb lighting control signal for controlling turning on / off of the first laser diode LDb and an LDb light quantity control signal for controlling the light quantity of the laser diode LDb based on image data under the control of the CPU 31. To the LDb drive circuit section 41b.

  The upper LDa control unit 33a, the LDb control unit 33b, and the CPU 31 function as a control unit as a whole.

  The memory (correction information storage means) 32 stores a light amount correction value (correction information) when the laser diode LDa and the laser diode LDb are turned on at the same time. The light amount correction value is a correction obtained in advance through experiments or the like. Value. That is, the amount of light when the laser diode LDa and the laser diode LDb are turned on in advance is measured at the same time as the light amount when the laser diode LDa and the laser diode LDb are turned on alone. A light amount correction value for correction is stored in the memory 32 in the CPU 31.

  The CPU 31 controls the LDa control unit 33a and the LDb control unit 33b to control the driving of the laser diode LDa and the laser diode LDb of the LDA 60 via the LD control unit 40, and simultaneously turns on the laser diode LDa and the laser diode LDb. In the case of performing the adjustment, the light amounts of the laser diode LDa and the laser diode LDb that are simultaneously turned on are adjusted based on the light amount correction value in the memory 32.

  The LD control unit 40 includes an LDa drive circuit unit 41a and an LDb drive circuit unit 41b, and a power supply voltage / power supply current is supplied from the power supply unit 50 through the transmission line 70 to the LDa drive circuit unit 41a and the LDb drive circuit unit 41b. The supplied LDa drive circuit unit 41a and LDb drive circuit unit 41b operate with the power supply voltage / power supply current.

  The LDa drive circuit unit 41a is connected to the laser diode LDa of the LDA 60, controls the drive current to the laser diode LDa based on the LDa lighting control signal from the LDa control unit 33a of the main control unit 30, and controls the laser diode LDa. While controlling on / off, the light amount of the laser diode LDa is controlled based on the LDa light amount control signal from the LDa control unit 33a.

  The LDb drive circuit unit 41b is connected to the laser diode LDb of the LDA 60, controls the drive current to the laser diode LDb based on the LDb lighting control signal from the LDb control unit 33b of the main control unit 30, and controls the laser diode LDb. While controlling on / off, the light quantity of the laser diode LDb is controlled based on the LDb light quantity control signal from the LDb control section 33b.

  The photodiode PD of the LDA 60 is connected to the LDa drive circuit unit 41a and the LDb drive circuit unit 41b of the LD control unit 40, receives the laser beams emitted from the laser diodes LDa and LDb, and receives the light amount of the laser beam. Is output to the LDa drive circuit unit 41a and the LDb drive circuit unit 41b. The LDa drive circuit unit 41a and the LDb drive circuit unit 41b are based on the monitor current from the photodiode PD at a predetermined timing before image formation or a timing before image formation for each line under the control of the CPU 31 of the main control unit 30. Then, the drive current to the laser diode LDa and the laser diode LDb is controlled to control the light amount of the laser diode LDa and the laser diode LDb. The LD control unit 40, that is, the LDa drive circuit unit 41a and the LDb drive circuit unit 41b function as element drive means.

  Next, the operation of this embodiment will be described. The laser printer 1 according to the present embodiment performs inexpensive and appropriate light amount correction when the two laser diodes LDa and LDb are turned on simultaneously.

  That is, in the laser printer 1, the LDA 60 includes two laser diodes LDa and LDb, and the LD control unit 40 includes LD driving circuit units 41a and 41b for the laser diodes LDa and LDb. A power supply voltage and a power supply current are supplied from the power supply unit 60 through the common transmission line 70 to the LD drive circuit units 41 a and 41 b of the LD control unit 40.

  Therefore, as shown in FIG. 4A, when the laser diode LDb is turned on while the laser diode LDa is turned on, the light amount of the laser diode LDa decreases as shown in FIG. 4A as an LDa light amount error. Variations occur.

  That is, if the laser diode LDb is turned on while the laser diode LDa is turned on, the current consumption increases as shown in the lowermost stage of FIG. The power supply voltage (LD power supply voltage) supplied through the transmission line 70 decreases. Actually, the power supply fluctuation rate is not so large, but when the length of the transmission line 70 or a mechanical contact such as a relay connector is inserted in the middle of the transmission line 70, the impedance increases, and the amount of power fluctuation As a practical problem, a light amount error that cannot be ignored may occur as shown by the LDa light amount error in FIG. In FIG. 4A, for the sake of explanation, the light amount fluctuation amount of the LDa light amount error is emphasized, but even if the light amount fluctuates by about several percent, the influence on the image occurs.

  Therefore, in the laser printer 1 of the present embodiment, the CPU 31 of the main control unit 30 controls the LDa control unit 33a, for example, as shown in FIG. When the laser diode LDa is turned on by the 40 LDa drive circuit unit 41a and the LDb control unit 33b is controlled to turn on the laser diode LDb by the LDb drive circuit unit 41b of the LD control unit 40, the LDa control unit 33a to the LDa An LDa light amount control signal obtained by correcting the LDa light amount control signal output to the drive circuit unit 41a based on the light amount correction value in the memory 32 is output to the LDa drive circuit unit 41a.

  When the LDa light quantity control signal corrected with this light quantity correction value is output from the LDa control section 33a to the LDa drive circuit section 41a, as shown in FIG. 4B, the laser diode LDb in the laser diode LDa is turned on simultaneously. A reduction in the amount of light can be prevented.

  In the above description, the case where there are two laser diodes has been described. However, the number of laser diodes LD is not limited to two. For example, as shown in FIG. Can be applied to.

  In this case, as shown in FIG. 5, the laser printer 1 includes two LDAs 60a and 60b, and each LDA 60a and 60b includes two laser diodes LDa and LDb and laser diodes LDc and LDd, respectively. The laser printer 1 includes LD control units 40a and 40b corresponding to the LDA 60a and LDA 60b. The LD control units 40a and 40b include an LDa drive circuit unit 41a and an LDb drive circuit unit 41b, and the LD control unit 40b includes: An LDc driving circuit unit 41c and an LDd driving circuit unit 41d are provided. Further, the main control unit 30 includes an LDa control unit 33a corresponding to the LDa drive circuit unit 41a of the LD control unit 40a, an LDb control unit 33b corresponding to the LDb drive circuit unit 41b, and an LDc drive circuit unit 41c of the LD control unit 40b. An LDd control unit 33d corresponding to the corresponding LDc control unit 33c and the LDd drive circuit unit 41d is provided, and the memory 32 is used when the laser diodes LDa, LDb, LDc, and LDd of the LDA 60a and the LDA 60b are lit individually and simultaneously. Are stored as well as the basic control program of the laser printer 1, the optical writing control program of the present invention, and necessary system data. In this case, the memory 32 is turned on simultaneously by combining any two of the laser diodes LDa, LDb, LDc, and LDd as light quantity correction values when the laser diodes LDa, LDb, LDc, and LDd of the LDA 60a and LDA 60b are turned on simultaneously. The light amount correction value when all three laser diodes LDa, LDb, LDc, and LDd are simultaneously lit and the light amount correction value when any three of them are lit simultaneously are stored. Yes.

  The laser printer 1 includes the main control unit 30, the LDa drive circuit unit 41a and the LDb drive circuit unit 41b of the LD control unit 40a, and the LDc drive circuit unit 41c of the LD control unit 40b through the transmission line 70 from one power supply unit 50. The power supply voltage / power supply current is supplied to the LDd drive circuit unit 41d, and the LDa drive circuit unit 41a and the LDb drive circuit unit 41b and the LDc drive circuit unit 41c and the LDd drive circuit unit 41dLDa are supplied with the power supply from one power supply unit 50. Operates according to voltage and power supply current.

  For example, as shown in FIG. 6A, when the laser diode LDb and the laser diode LDc are sequentially turned on while the laser diode 1 is turned on, the laser printer 1 in FIG. 6B shows a light amount error (LDb + LDc ), As shown as a light quantity error (due to LDc), a light quantity variation occurs in which the light quantity decreases as the number of laser diodes LDa, LDb, and LDc that are steadily lit increases.

  That is, if the laser diode LDb and the laser diode LDc are sequentially turned on while the laser diode LDa is turned on, the current consumption increases sequentially as shown in the lowermost stage of FIG. As a result, the power supply voltage (LD power supply voltage) supplied from the power supply unit 50 through the transmission line 70 decreases.

  In the laser printer 1, the CPU 31 of the main control unit 30 controls the LDa control unit 33 a and drives the LDa of the LD control unit 40 as shown in FIG. When the laser diode LDa is turned on by the circuit unit 41a, the LDb control unit 33b is controlled, and the laser diode LDb is turned on by the LDb drive circuit unit 41b of the LD control unit 40, the LDa control unit 33a to the LDa drive circuit unit 41a. The LDa light amount control signal corrected based on the light amount correction value in the memory 32 is output to the LDa drive circuit unit 41a, and the LDc control unit 33c is further controlled to control the LD control unit 40. When the laser diode LDc is turned on by the LDc driving circuit unit 41c, the LDa control unit 33a drives the LDa. The LDa light amount control signal obtained by correcting the LDa light amount control signal output to the path portion 41a based on the light amount correction value in the memory 32 is output to the LDa drive circuit portion 41a, and further, the LDb control portion 33b to the LDb drive circuit portion 41b. The LDb light quantity control signal corrected based on the light quantity correction value in the memory 32 is outputted to the LDb drive circuit unit 41b.

  The LDa light amount control signal corrected with this light amount correction value is output from the LDa control unit 33a to the LDa drive circuit unit 41a, and the LDb light amount control signal corrected with this light amount correction value is output from the LDb control unit 33b to the LDb drive circuit unit 41b. As shown in FIG. 6B, it is possible to prevent a decrease in the amount of light when the laser diode LDb of the laser diode LDa is simultaneously turned on.

  In FIG. 6, the case where the three laser diodes LDa to LDc are turned on simultaneously has been described. However, when the two laser diodes LDa to LDd are turned on simultaneously, the case where the four laser diodes LDa to LDd are turned on simultaneously is also described. The same can be applied.

  As described above, the laser printer 1 according to the present embodiment, when individually turning on / off the plurality of laser diodes LDa to LDd with a predetermined amount of light, simultaneously turns on the plurality of laser diodes LDa to LDd, The amount of emitted light when the plurality of laser diodes LDa to LDd are lit alone and the amount of emitted light of each of the laser diodes LDa to LDd that are lit simultaneously when the plurality of laser diodes LDa to LDd are lit simultaneously Referring to the memory 32 that stores the light quantity correction value that is correction information for correcting the light quantity difference between the laser diodes LDa to LDd that are simultaneously lit based on the light quantity correction values corresponding to the laser diodes LDa to LDd that are simultaneously lit. The amount of emitted light is corrected and controlled.

  Therefore, when the plurality of laser diodes LDa to LDd are turned on at the same time, the amount of light that is reduced can be corrected as compared with when the laser diodes LDa to LDd are turned on independently. The light emission amount of each of the laser diodes LDa to LDd to be lit can be controlled to the target light amount inexpensively and appropriately.

  Further, in the laser printer 1 of this embodiment, the main control unit 30 designates an LD light amount control signal (LDa light amount) for designating the light emission amount of the laser diodes LDa to LDd for each of the laser diodes LDa to LDd to be turned on by the LD control unit 40. Control signal to LDd light amount control signal), and the LD light amount control signal for the laser diodes LDa to LDd to be turned on simultaneously based on the light amount correction value of the memory 32 is corrected to correct and control the emitted light amount of the laser diodes LDa to LDd. ing.

  Therefore, it is possible to more easily and appropriately control the light emission quantity of each of the laser diodes LDa to LDd to be lit at the target light quantity without being affected by the number of laser diodes LDa to LDd that are lit simultaneously.

  As shown in FIG. 7, the laser printer 1 feeds back the monitor current output from the photodiode (light emission amount detection means) PD of the LDA 60 to the CPU 31 of the main control unit 30 as a light amount detection signal, and sets the light amount correction value. It may be acquired and stored in the memory 32.

  That is, as shown in FIG. 7, the laser printer 1 feeds back the monitor current output from the photodiode PD of the LDA 60 to the CPU 31 of the main control unit 30, and provides the CPU 31 with an ADC (analog / digital converter) 34. The laser printer 1 inputs an analog monitor current output from the photodiode PD of the LDA 60 to the ADC 34, and the ADC 34 digitally converts the analog monitor current input from the photodiode PD. The ADC 34 is not limited to the one provided in the CPU 31 and may be provided outside the CPU 31.

  The CPU 31 controls the LDa control unit 33a and the LDb control unit 33b at an arbitrary timing before the image forming operation, and the laser diode LDa and the laser diode LDb of the LDA 60 via the LDa drive circuit unit 41a and the LDb drive circuit unit 41b. Are individually driven to be lit, and the laser diode LDa and the laser diode LDb are simultaneously driven to be lit, and the monitor current when the laser diodes LDa and LDb are driven to be lit individually and the monitor current when simultaneously driven to be lit are Based on the monitor current value digitally converted by the AD converter 34, a light amount error is calculated when the laser diodes LDa and LDb are individually lit and simultaneously lit. When the CPU 31 calculates the light amount error when the laser diodes LDa and LDb are individually turned on and simultaneously, the CPU 31 stores the light amount correction value for correcting the light amount error in the memory 32.

  Then, the CPU 31 performs light amount correction based on the light amount correction value stored in the memory 32 when the laser diodes LDa and LDb are simultaneously turned on during image formation.

  As described above, the laser printer 1 includes the photodiode (light emission amount detection means) PD that detects the light emission amounts of the laser diodes LDa to LDd and outputs a monitor current (light amount detection signal) corresponding to the light emission amounts. The CPU 31 of the control unit 30 causes the LD control unit 40 to turn on and drive the plurality of laser diodes LDa to LDd alone, and simultaneously drives the plurality of laser diodes LDa to LDd to turn on, so that at the time of the single lighting and at the same time. A light amount correction value is acquired based on the monitor current detected by the photodiode PD during lighting and stored in the memory 32.

  Therefore, it is not necessary to perform a light amount measurement process for acquiring a light amount correction value in advance when the laser printer 1 is manufactured and store it in the memory 32, and the manufacturing cost can be reduced. Thus, even if the impedance characteristic of the transmission line 70 changes, the light amount correction value of the memory 32 can be set to an appropriate light amount correction value, and more appropriate light amount correction control can be performed at a low cost.

  In the above description, the case where the light emission amount of the two light emitting elements (laser diodes LDa and LDb) is detected by the photodiode PD, the light amount correction value is acquired and stored in the memory 32 has been described. The same applies to the case where the number is three or more.

  Further, the laser printer 1 of this embodiment includes the LDa drive circuit unit 41a and the LDb drive circuit unit 41b of the LD control unit 40 or the LDa drive circuit unit 41a, the LDb drive circuit unit 41b, and the LDc drive circuit of the LD control units 40a and 40b. The analog voltage is supplied to the unit 41c and the LDd drive circuit unit 41d, and the light amount is controlled according to the DC level of the analog voltage. The LD drive circuit unit of the LD control unit controls the light amount by the analog voltage. The present invention is not limited to this, and the present invention can be similarly applied to the case where the light amount is controlled by controlling the pulse width of the PWM signal or the light amount is controlled by controlling the frequency of the CLK signal.

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

  The present invention can be used for an optical writing apparatus, an image forming apparatus, and an optical writing control method in which the number of light emitting elements such as laser diodes that are driven to be turned on simultaneously is changed.

DESCRIPTION OF SYMBOLS 1 Laser printer 2 Image formation part 3 Fixing part 10 Photoconductor 11 Charging part 12 Optical writing part 13 Development part 14 Transfer part 15 Separation part 16 Cleaning part 21 LD unit 22 Polygon mirror 23 f (theta) lens 24 Reflection mirror 25 Synchronous reflection mirror 26 Synchronization Detection element 30 Main control unit 31 CPU
32 Memory 33a LDa control unit 33b LDb control unit 33c LDc control unit 33d LDd control unit 40, 40a, 40b LD control unit 41a LDa drive circuit unit 41b LDb drive circuit unit 41c LDc drive circuit unit 41d LDd drive circuit unit 50 Power supply unit 60 60a, 60b LDA
70 Transmission line LDa, LDb, LDc, LDd Laser diode PD Photo diode

JP 2006-91553 A

Claims (5)

Multiple light-emitting elements that can be turned on and off individually,
Element driving means for individually turning on and off the plurality of light emitting elements with a predetermined light amount;
Correction for correcting a light amount difference between a light emission amount when a plurality of the light emitting elements are individually turned on and a light emission amount of each light emitting element that is simultaneously turned on when a plurality of the light emitting elements are combined and simultaneously turned on Correction information storage means for storing information;
When the element driving means turns on the light emitting element and simultaneously turns on a plurality of the light emitting elements, the simultaneous driving of the element driving means based on the correction information of the correction information storage means corresponding to the light emitting element. Control means for correcting and controlling the light emission amount of the light emitting element;
An optical writing device comprising:   The control means outputs a light amount control signal for designating a light emission amount of the light emitting element for each of the light emitting elements to be lit by the element driving means, and the light emitting elements to be turned on simultaneously based on correction information in the correction information storage means The optical writing apparatus according to claim 1, wherein the light quantity control signal is corrected to control the quantity of light emitted from the light emitting element. The optical writing device includes a light emission amount detection unit that detects a light emission amount of the light emitting element and outputs a light amount detection signal corresponding to the light emission amount,
The control means causes the element driving means to drive the plurality of light emitting elements independently, and simultaneously drives the light emitting elements in combination to drive the light emission amount at the time of the single lighting and the simultaneous lighting. The optical writing apparatus according to claim 1, wherein the correction information is acquired based on a light amount detection signal detected by the correction information and stored in the correction information storage unit.   The uniformly charged photosensitive member is irradiated with light writing light modulated based on image data from the light writing means to form an electrostatic latent image, and the electrostatic latent image on the photosensitive member is developed as a developer. In the image forming apparatus for forming an image by transferring the developer image developed in step 1 to a recording medium, the optical writing device according to any one of claims 1 to 3 is mounted as the optical writing unit. An image forming apparatus. An element driving process step for individually turning on / off a plurality of light emitting elements;
When simultaneously lighting a plurality of the light emitting elements in the element driving process step, the light emission amount when the plurality of light emitting elements are individually driven to light and the simultaneous lighting when the plurality of light emitting elements are combined and lighted simultaneously The correction information corresponding to the light emitting elements to be simultaneously turned on is referred to from the correction information storage means for storing correction information for correcting the light amount difference with the light emission amount of each individual light emitting element, and based on the correction information, the correction information is stored. A control processing step for correcting and controlling the light emission amount of the light emitting elements that are simultaneously turned on in the element driving processing step;
An optical writing control method comprising:

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