JP2013047728A - Image forming apparatus, image forming method, and image forming program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrict unnecessary exposure to a photoreceptor.SOLUTION: The method comprises: the step in which after a predetermined time has elapsed after one of leading-end synchronization detecting sensors 139c, 139m, 139y, and 139k detects a light beam used for formation in color other than a control target color, an LD used for formation in control target color is turned on among LDs 132c, 132m, 132y, and 132k; and the step in which after a light beam used for formation in the control target color is detected by another one among the leading-end synchronization detecting sensors 139c, 139m, 139y, and 139k, an LD used for formation in the control target color is turned off among the LDs 132c, 132m, 132y, and 132k.

Description

  The present invention relates to an image forming apparatus that forms an image, an image forming method, and an image forming program.

  By forming an image in an image forming apparatus such as a copier or a multi function device (MFP: Multi Function Peripherals) in which a plurality of functions such as copying, faxing, and printers are housed in a single housing, The temperature in the writing optical unit rises due to the heat of the polygon mirror. Due to this temperature rise, the magnification of the lens in the main scanning direction is changed, so that the image is expanded or contracted. In order to correct this, it is known to perform magnification correction by changing the write clock frequency.

  Further, when the power is turned on or the temperature is changed, an initialization operation for detecting a threshold current or a light emission current is performed in order to adjust the light emission amount of the laser light source to an appropriate value. It is known to change the laser current while rotating the polygon mirror in order to prevent the photosensitive member from being deteriorated by irradiating only a part of the photosensitive member with laser light during the initialization operation.

  However, in the conventional image forming apparatus, the clock frequency is changed by changing the frequency division ratio of PLL (Phase Locked Loop), and the clock frequency is not stable for a certain period after the frequency division ratio is changed. For this reason, in a period in which the clock frequency is not stable, the synchronization detection lighting cannot be performed at the normal position, and for example, a one-line period synchronization detection signal is missed. Then, by continuing to turn on the laser light source until the synchronization detection signal is input, there is a problem that unnecessary irradiation is performed on the photoconductor, and unnecessary horizontal lines and the like are formed.

  In addition, since the conventional initialization operation is performed without distinguishing whether the main scanning position is an effective image area or a non-image area on the photosensitive member, the laser light source emits light during the initialization operation. In addition, there is a problem in that the effective image area portion of the photoconductor is exposed to accelerate deterioration and failure of the photoconductor.

  In Patent Document 1, in order to prevent the lighting start position with respect to the sensor position from changing due to the change of the writing clock frequency in order to correct the image magnification, the lighting timing of the lighting timing is prevented. It is disclosed that the set value is variable.

  However, the technique described in Patent Document 1 is to change the lighting position in accordance with the change of the write clock frequency so as not to miss the synchronization detection signal. However, the frequency is not stable when the write clock frequency is changed. Will miss the sync detection signal.

  The present invention has been made in view of the above, and an object of the present invention is to suppress unnecessary irradiation of a photoreceptor.

  In order to solve the above-described problems and achieve the object, the present invention is an image forming apparatus for forming an image composed of a plurality of colors, and a plurality of photoconductors respectively used for forming the plurality of colors. A plurality of light sources that output light beams respectively used for forming the plurality of colors, and a light beam output from the plurality of light sources in a main scanning direction of the plurality of photoconductors by a plurality of deflection surfaces. Deflecting means for deflecting; a plurality of detecting means for detecting light beams deflected by the deflecting means, respectively; and a control means for controlling lighting of the plurality of light emitting sources. The control means includes: a light beam used for forming a color other than the color to be controlled by one of the plurality of detection means, and a predetermined time has elapsed after the elapse of a predetermined time. The color of the controlled object When the light source used for formation is turned on and the other one of the plurality of detection means detects a light beam used for forming the color of the control target, the control target of the plurality of light emission sources is detected. A first control for turning off a light emitting source used for color formation is executed.

  The present invention also provides a plurality of photoconductors used for forming a plurality of colors, a plurality of light sources for outputting light beams respectively used for forming the plurality of colors, and the plurality of light sources. A light beam deflected in the main scanning direction of the plurality of photoconductors by a plurality of deflecting surfaces, and a light beam deflected by the deflecting unit is detected at each end of the plurality of photoconductors. An image forming method executed by an image forming apparatus comprising a plurality of detecting means and a control means for controlling lighting of the plurality of light emitting sources, wherein the light beam is used for forming a color other than the color to be controlled After a predetermined time has elapsed since one of the plurality of detecting means detects the light source used to form the color to be controlled among the plurality of light source, and For color formation A step of turning off a light source used for forming the color to be controlled among the plurality of light sources when another one of the plurality of detection means detects the light beam to be input. Features.

  The present invention also provides a plurality of photoconductors used for forming a plurality of colors, a plurality of light sources for outputting light beams respectively used for forming the plurality of colors, and the plurality of light sources. A light beam deflected in the main scanning direction of the plurality of photoconductors by a plurality of deflecting surfaces, and a light beam deflected by the deflecting unit is detected at each end of the plurality of photoconductors. An image forming program executed by an image forming apparatus comprising a plurality of detecting means and a control means for controlling lighting of the light emitting sources, and a light beam used for forming a color other than the color to be controlled Lighting a light-emitting source used for forming the color to be controlled among the plurality of light-emitting sources after a predetermined time has elapsed since one of the plurality of detecting means detects When the other one of the plurality of detection means detects the light beam used for forming the light source, turning off the light emission source used for forming the color to be controlled among the plurality of light emission sources, It is characterized by providing.

  According to the present invention, unnecessary irradiation to the photoconductor can be suppressed. Thereby, formation of unnecessary horizontal lines and the like can be suppressed, and deterioration and failure of the photoreceptor can be suppressed.

FIG. 1 is a block diagram illustrating a configuration of a mechanism of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a diagram showing a configuration of the light beam scanning apparatus of FIG. FIG. 3 is a functional block diagram showing an outline of the control unit of the image forming apparatus according to the embodiment of the present invention. FIG. 4A is a diagram illustrating a portion related to light beam scanning control of the GAVD of FIG. FIG. 4B is a diagram illustrating an internal configuration of the magnification error detection unit of FIG. 4A. FIG. 5 is a waveform diagram showing the operation of the synchronous detection lighting control unit of FIG. 4-1. FIG. 6 is a waveform diagram showing the operation of the synchronous detection lighting control unit of FIG. 4-1. FIG. 7A is a waveform diagram illustrating the operation of the synchronization detection lighting control unit of FIG. 4A. FIG. 7-2 is a waveform diagram showing an operation of the synchronization detection lighting control unit of FIG. 4-1. FIG. 8A is a waveform diagram illustrating the operation of the synchronization detection lighting control unit of FIG. 4A. FIG. 8-2 is a waveform diagram illustrating the operation of the synchronization detection lighting control unit of FIG. 4-1. FIG. 9 is a waveform diagram showing the operation of the synchronous detection lighting control unit of FIG. 4-1. FIG. 10 is a waveform diagram showing the operation of the synchronization detection lighting control unit of FIG. 4-1. FIG. 11 is a flowchart showing a writing initial operation after the image forming apparatus 100 is powered on. FIG. 12 is a flowchart showing the transition operation from the monochrome printing mode to the color printing mode. FIG. 13 is a waveform diagram showing the tip side synchronization detection signal and the forced lighting signal when the clock frequency is changed. FIG. 14 is a flowchart showing the magnification correction operation by changing the clock frequency. FIG. 15 is a waveform diagram showing an operation during LD initialization. FIG. 16 is a flowchart showing an initialization operation in the image forming apparatus. FIG. 17 is a diagram illustrating a configuration of an image forming apparatus including two polygon mirrors. FIG. 18 is a diagram showing a configuration of a writing unit when two polygon mirrors are provided. FIG. 19 is a block diagram illustrating a hardware configuration of the image forming apparatus according to the present embodiment.

  Exemplary embodiments of an image forming apparatus according to the present invention will be explained below in detail with reference to the accompanying drawings. FIG. 1 is a block diagram illustrating a configuration of a mechanism of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus 100 is an image processing apparatus including, for example, a facsimile machine, a printing apparatus (printer), a copying machine, and a multifunction machine.

  The light beam scanning device 101 converts light beams emitted from a light source (not shown) such as an LD (laser diode), an LD array, a VICSEL, an LED, and an EL into cyan (C), magenta (M), and yellow (Y). The black (K) photosensitive drums (hereinafter abbreviated as “photosensitive members”) 111c, 111m, 111y, and 111k are imagewise irradiated. In this embodiment, an LD is used as the light source.

  The photoreceptors 111c, 111m, 111y, and 111k include a photoconductive layer including at least a charge generation layer and a charge transport layer on a conductive drum such as aluminum. The photoconductive layers are disposed corresponding to the photoreceptors 111c, 111m, 111y, and 111k, respectively, and surface charges are applied by the chargers 112c, 112m, 112y, and 112k including a corotron, a scorotron, or a charging roller. Is done.

  The electrostatic charges imparted on the photoreceptors 111c, 111m, 111y, and 111k by the chargers 112c, 112m, 112y, and 112k, respectively, are imagewise exposed by the light beam from the light beam scanning device 101. As a result, electrostatic latent images are formed on the scanned surfaces of the photoreceptors 111c, 111m, 111y, and 111k.

  The electrostatic latent images formed on the scanned surfaces of the photoreceptors 111c, 111m, 111y, and 111k are respectively developed by developing units 113c, 113m, 113y, and 113k including a developing sleeve, a developer supply roller, and a regulating blade. Is done. As a result, developer images are formed on the scanned surfaces of the photoreceptors 111c, 111m, 111y, and 111k.

  The developers carried on the scanned surfaces of the photoconductors 111c, 111m, 111y, and 111k are conveyed by the primary transfer devices 114c, 114m, 114y, and 114k to the photoconductors 111c, 111m, 111y, and 111k. The image is transferred onto the intermediate transfer belt 120 that moves in the direction of the arrow by 121b, 121c, and 121d. The visible images remaining on the photoconductors 111c, 111m, 111y, and 111k are cleaned by the cleaning devices 115c, 115m, 115y, and 115k, and are neutralized by the neutralization devices 116c, 116m, 116y, and 116k. Visible images created in C, M, Y, and K colors are superimposed on the intermediate transfer belt 120.

  The intermediate transfer belt 120 carries the C, M, Y, and K developers transferred from the scanned surfaces of the photoreceptors 111c, 111m, 111y, and 111k, respectively, and transport rollers 121a, 121b, 121c, and 121d. Is conveyed in the direction of the arrow. Paper P, which is an image receiving material such as high-quality paper or plastic sheet, is supplied between the conveyance roller 121b and the secondary transfer device 122 from a paper feed cassette or the like. The secondary transfer device 122 applies a secondary transfer bias to transfer the multicolor developer image carried on the intermediate transfer belt 120 onto the paper P. The paper P is supplied to the fixing device 123 along with the conveyance of the transfer belt 120. The fixing device 123 is configured to include a fixing member such as a fixing roller containing silicone rubber, fluorine rubber, or the like, and pressurizes and heats the paper P and the multicolor developer image to the outside of the image forming apparatus 100. Discharge.

  The intermediate transfer belt 120 after transferring the multicolor developer image is supplied to the next image forming process after the transfer residual developer is removed by the cleaning unit 124 including the cleaning blade.

  Further, a light source 125 that emits light to the intermediate transfer belt 120 and a sensor 126 that detects light emitted from the light source 125 and reflected by the intermediate transfer belt 120 are provided between the conveyance roller 121a and the conveyance roller 121b. Is provided. The light source 125 irradiates the pitch shift detection pattern on the intermediate transfer belt 120 with light, and the sensor 126 detects the pitch shift amount by the reflected light or diffused light.

  FIG. 2 is a diagram illustrating a configuration of the light beam scanning apparatus 101. In the present embodiment, four polygons of C, M, Y, and K are deflected by one polygon mirror 135. Beams emitted from the LDs 132c, 132m, 132y, and 132k mounted on the LD driver boards 131c, 131m, 131y, and 131k are collimated by collimating lenses 133c, 133m, 133y, and 133k. The beams that have passed through the collimating lenses 133m and 133y are reflected in the direction of the polygon mirror 135 by the mirrors 134m and 134y.

  The beams made parallel by collimating lenses 133c, 133m, 133y, and 133k are deflected by polygon mirror 135, and dots are uniformly formed on photoconductors 111c, 111m, 111y, and 111k in the main scanning direction by fθ lenses 136 and 137. It is corrected so that it can be formed. The beams that have passed through the fθ lenses 136 and 137 are reflected by the folding mirrors 138c, 138m, 138y, and 138k, and are applied to the photoconductors 111c, 111m, 111y, and 111k. Further, the light beam scanning device 101 includes front end synchronization detection sensors 139c, 139m, 139y, and 139k that detect the main scan writing position, and rear end synchronization detection sensors 140c, 140m, 140y, and 140k that perform magnification correction described later. I have.

  FIG. 3 is a functional block diagram showing an outline of the control unit of the image forming apparatus according to the present embodiment. The control unit 300 includes a scanner unit 302, a printer unit 308, and a main control unit 330.

  The scanner unit 302 functions as a means for reading an image. A VPU 304 that performs A / D conversion on a signal read by the scanner to perform black offset correction, shading correction, and pixel position correction, and a mainly acquired image. , And an IPU 306 that performs image processing for digital conversion from RGB color system to CMYK color system image data. The read image acquired by the scanner unit 302 is sent to the printer unit 308 as digital data.

  The printer unit 308 is two-dimensionally arranged with a GAVD 310 that functions as a control unit that performs drive control of the LD 132, an LD driver 131 that supplies a current for driving the LD element to the LD 132 using a drive control signal generated by the GAVD 310. And an LD 132 mounted with the LD element. The scanner unit 302 and the printer unit 308 are connected to the main control unit 330 via the system bus 316, and image reading and image formation are controlled by commands from the main control unit 330.

  The main control unit 330 includes a central processing unit (hereinafter referred to as “CPU”) 320 and a RAM 322 that provides a processing space used by the CPU 320 for processing. Various CPUs can be used as the CPU 320, for example, a CISC (Complex Instruction Set Computer) type CPU, a RISC (Reduced Instruction Set Computer) type CPU, or the like can be used.

  The CPU 320 receives a command from the user via the interface 328, calls a program module that executes processing corresponding to the command, and executes processing such as copying, facsimile, scanner, and image storage.

  Further, the main control unit 330 includes a ROM 324. The ROM 324 stores initial setting data, control data, programs, and the like of the CPU 320 so that the CPU 320 can use them. The image storage 326 is configured as a fixed or removable memory device such as a hard disk device, an SD card (registered trademark), or a USB memory. The image storage 326 stores image data acquired by the image forming apparatus 100 and performs various processes by the user. It can be used. The I / O control 329 performs various motor drives and detection by various sensors.

  When the CPU 320 drives the printer unit 308 with respect to the image data acquired by the scanner unit 302 and outputs an image as an electrostatic latent image to the photoconductors 111c, 111m, 111y, and 111k, the CPU 320 receives an image receiving material such as fine paper or plastic film. Main scanning direction control and sub-scanning position control are executed. The CPU 320 outputs a start signal to the GAVD 310 when starting scanning in the sub-scanning direction. When the GAVD 310 receives the start signal, the IPU 306 outputs a MFSYNC_N signal, which is one of the image data interface signals, to the IPU 306, so that the IPU 306 starts the scanning process. Thereafter, the GAVD 310 receives the image data and stores it in the memory, processes the received image data, and outputs the processed image data to the LD driver 131. When receiving the image data from the GAVD 310, the LD driver 131 generates a drive control signal for the LD 132. After that, the LD driver 131 sends the drive control signal to the LD 132 to light the LD 132. Note that the LD driver 131 drives the LD 132 using PWM control or the like.

  FIG. 4A and FIG. 4B are diagrams illustrating portions related to the light beam scanning control of the GAVD 310. When the light beam passes over the leading edge synchronization detection sensor 139, the leading edge side synchronization detection signal DETP_N is output, and when the light beam passes over the trailing edge synchronization detection sensor 140, the trailing edge side synchronization detection signal EDETP_N is output. And input to the magnification error detector 344.

  The magnification error detection unit 344 measures the time from the falling edge of the leading end side synchronization detection signal DETP_N to the falling edge of the trailing end side synchronization detection signal EDETP_N, compares it with the reference time difference, and outputs the difference to the overall control unit 343. To do. The overall control unit 343 generates correction data corresponding to the difference and outputs the correction data to a PLL (Phase Locked Loop) 342. The PLL 342 corrects the image magnification by generating the output clock signal VCLK in which the frequency of the reference clock signal REFCLK generated by the reference clock generation unit 341 is changed based on the correction data.

  Although not shown, the PLL 342 includes a VCO (Voltage Controlled Oscillator), a phase comparator, and a frequency divider. A signal obtained by dividing the reference clock signal REFCLK from the reference clock generation unit 341 by M with a 1 / M divider and a signal obtained by dividing the output clock signal VCLK by N with a 1 / N divider are used as a phase comparator. Entered. The phase comparator compares the phases of the falling edges of both signals and outputs an error component at a constant current. The output signal of the phase comparator is freed of unnecessary high frequency components and noise by an LPF (low pass filter) and input to the VCO. The VCO outputs an output clock signal VCLK having an oscillation frequency corresponding to the voltage of the input signal. Therefore, the PLL 342 can vary the frequency of the output clock signal VCLK by varying the frequency division ratio: N based on the correction data from the overall control unit 343.

  The leading end side synchronization detection signal DETP_N is also input to the clock phase matching unit 345. The clock phase matching unit 345 generates a pixel clock signal PCLK obtained by synchronizing the clock signal VCLK generated by the PLL 342 with the front end side synchronization detection signal DETP_N, and outputs the pixel clock signal PCLK to the synchronization detection lighting control unit 346 and the magnification error detection unit 344. . Therefore, in the PLL 342, the frequency of the clock signal VCLK is varied by the correction data from the overall control unit 343, and thereby the frequency of the pixel clock signal PCLK is varied. Thus, by changing the frequency of the pixel clock signal PCLK, the overall magnification of the image can be changed.

  Further, the front end side synchronization detection signal DETP_N and the rear end side synchronization detection signal EDETP_N are also input to the synchronization detection lighting control unit 346. Although the synchronization detection lighting control unit 346 will be described later, the forced lighting signals BD and EBD output from the synchronization detection lighting control unit 346 are input to the LD driver 131. Further, the leading edge side synchronization detection signal DETP2_N used in the other colors is input to the synchronization detection lighting control unit 346.

  The LD driver 131 controls the lighting of the LD 132 according to the image data synchronized with the forced lighting signal BD for detecting synchronization and the pixel clock signal PCLK. The polygon motor control unit 311 controls the rotation of the polygon mirror 135 by controlling the rotation of the polygon motor at a specified rotational speed based on the control signal input from the overall control unit 343.

  FIG. 4B is a diagram illustrating an internal configuration of the magnification error detection unit 344 of FIG. 4A. The magnification error detection unit 344 includes a time difference counting unit 345 and a comparison control unit 346. The time difference counting unit 345 includes a counter 347 and a latch 348.

  The counter 347 is cleared by the front end side synchronization detection signal DETP_N and is counted up by the pixel clock signal PCLK. The latch 348 latches the count value of the counter 347 at the falling edge of the rear end side synchronization detection signal EDETP_N. That is, the latch 348 latches the time difference between the front end side synchronization detection signal DETP_N and the rear end side synchronization detection signal EDETP_N. The comparison control unit 346 compares the count value (time difference) T latched by the latch 348 with a preset reference count value (reference time difference) T0 and obtains difference data (magnification error data). And output to the overall control unit 343. The overall control unit 343 calculates a set value of the pixel clock frequency from the magnification error data, and outputs the calculated value to the PLL 342 as correction data. Note that, as the reference count value (reference time difference) T0, for example, six surfaces of the polygon mirror 135 are measured in advance and set as an average value thereof.

  Next, the synchronization detection lighting control unit 346 will be described. The operation of the lighting control unit 346 for synchronization detection includes a mode A that is generally performed and a mode B that is unique to the present embodiment. FIG. 5 is a waveform diagram showing the operation in mode A of the sync detection lighting control unit 346. When the signal LDON is asserted by the CPU 320, the synchronization detection lighting control unit 346 first turns on the forced lighting signal BD to forcibly light the LD 132 in order to detect the front end side synchronization detection signal DETP_N.

  The synchronization detection lighting control unit 346 performs an initial load (initial value 0) of the BD counter using the front end side synchronization detection signal DETP_N as a trigger, and then counts up the BD counter in synchronization with the pixel clock signal PCLK. Then, after detecting the front end side synchronization detection signal DETP_N once, the synchronization detection lighting control unit 346 does not perform unnecessary irradiation on the photoconductor based on the front end side synchronization detection signal DETP_N and the pixel clock signal PCLK. Further, the LD 132 is turned on at a timing at which the front end side synchronization detection signal DETP_N can be reliably detected without causing flare light.

  In FIG. 5, the synchronization detection lighting control unit 346 asserts the LD forcible lighting signal BD output to the LD driver 131 when the count value of the BD counter reaches 3 FDE (hex), and turns on the LD 132. Is set to In addition, the synchronization detection lighting control unit 346 negates the LD forced lighting signal BD output to the LD driver 131 when the front end side synchronization detection signal DETP_N is detected, and turns off the LD 132. As for the rear end side synchronization detection signal EDETP_N, after the front end side synchronization detection signal DETP_N is input, similar lighting control is performed by the BD counter.

  In the present embodiment, mode A is used when the image forming apparatus 100 is started up. Note that during the start-up operation of the image forming apparatus 100, LD irradiation to the photoconductors 111c, 111m, 111y, and 111k is not charged with the developing units 113c, 113m, 113y, and 113k, so abnormalities such as horizontal stripes are detected. It does not form an image.

  Next, mode B will be described with reference to FIG. FIG. 6 is a waveform diagram showing the operation in mode B of the lighting control unit 346 for synchronization detection. In the above-described mode A, the LD 132 is forcibly lit until the first tip side synchronization detection signal DETP_N is input, and unnecessary irradiation is performed on the photoconductors 111c, 111m, 111y, and 111k. On the other hand, in the mode B, the first tip side synchronization of the own color (the color to be controlled) using the tip side synchronization detection signal DETP2_N of the other color (the color other than the control subject) that is stably input. The lighting for detecting the detection signal DETP_N is started.

  When the signal LDON is asserted by the CPU 320, the synchronization detection lighting control unit 346 performs an initial load (initial value 0) of the BD counter using the leading edge side synchronization detection signal DETP2_N of another color as a trigger, and then the pixel clock signal PCLK. Synchronously, the BD counter is counted up. When the BD counter reaches 3FDE (hex), the forced lighting signal BD is asserted and the LD 132 is turned on. When the self-color front end side synchronization detection signal DETP_N is input by the first lighting, the BD counter is initially loaded in synchronization with the self color front end side synchronization detection signal DETP_N. As described above, in mode B, the lighting timing control using the front-end side synchronization detection signal DETP2_N of another color and the lighting timing control using the front-end side synchronization detection signal DETP_N of the own color are switched.

  Here, the phase difference between the self-color front end side synchronization detection signal DETP_N and the other color front end side synchronization detection signal DETP2_N must always be within a certain range. When the phase difference between the front-end-side synchronization detection signal DETP_N of the own color and the front-end-side synchronization detection signal DETP2_N of the other color changes every time the rotation of the polygon mirror 135 is turned on or off or changes with time, the photosensitive member 111c, Light is irradiated onto 111m, 111y, and 111k. This will be described with reference to FIGS. 7-1, 7-2, 8-1 and 8-2. FIG. 7A, FIG. 7B, FIG. 8A, and FIG. 8B are waveform diagrams illustrating the operation of the synchronization detection lighting control unit 346.

  When the phase difference between the self-color front end side synchronization detection signal DETP_N and the other color front end side synchronization detection signal DETP2_N is the difference shown in FIG. 7A (phase timing A), the photosensitive members 111c, 111m, 111y, and 111k are moved to. In order to prevent unnecessary irradiation, the timing for asserting the forced lighting signal BD is set when the BD counter reaches 3FDE (hex). After that, due to the change over time, the self-color front end side synchronization detection signal DETP_N is relatively delayed, and the phase difference between the self color front end side synchronization detection signal DETP_N and the other color front end side synchronization detection signal DETP2_N is shown in FIG. If the difference is as shown (phase timing B) and the forced lighting signal BD is asserted when the BD counter reaches 3FDE (hex), unnecessary irradiation is performed on the photoconductors 111c, 111m, 111y, and 111k. (The hatched part in FIG. 7-2).

  Further, when the phase difference between the front-end synchronization detection signal DETP_N of the own color and the front-end synchronization detection signal DETP2_N of the other color is the difference shown in FIG. 8B (phase timing B), the photoconductors 111c, 111m, 111y, In order to prevent unnecessary irradiation to 111k, the timing for asserting the forced lighting signal BD is set when the BD counter reaches 300 (hex). Thereafter, due to a change with time, the front-end synchronization detection signal DETP_N of the own color is relatively delayed, and the phase difference between the front-end synchronization detection signal DETP_N of the own color and the front-end synchronization detection signal DETP2_N of the other color is shown in FIG. When the difference shown in the figure (phase timing A) is reached and the forced lighting signal BD is asserted when the BD counter reaches 300 (hex), unnecessary irradiation is performed on the photoconductors 111c, 111m, 111y, and 111k. (The hatched portion in FIG. 8A).

  As described above, when the phase difference between the front-end synchronization detection signal DETP_N of the own color and the front-end synchronization detection signal DETP2_N of the other color varies due to changes over time, the forced lighting signal is generated using the front-end synchronization detection signal DETP2_N of the other color. When BD is asserted, unnecessary irradiation is performed on the photoconductors 111c, 111m, 111y, and 111k.

  Therefore, a condition that can prevent unnecessary irradiation of the photosensitive members 111c, 111m, 111y, and 111k is examined. FIG. 9 is a waveform diagram showing the operation of the sync detection lighting control unit 346.

As shown in FIG. 9, the timing at which the front-end-side synchronization detection signal DETP_N of the own color is input is time t ₁ , and the timing at the end of the main scanning rear end side of the photoconductors 111c, 111m, 111y, 111k is time t _3. , the time t ₅ the timing when the next own color on the front end side synchronization detection signal DETP_N is input. In this case, one line period, a time _t 1 ~t _5. Further, when the normal LD lighting time (generally, lighting is started from 3 mm before 5 mm of the self-color front end side synchronization detection signal DETP_N) is α, the timing at which the forced lighting signal BD is asserted is from time t ₅ . the front of the time t ₄ only α.

At this time, if the timing at which the forced lighting signal BD is asserted is in the range of time t _{3 to} t ₄ , unnecessary irradiation to the photoconductors 111c, 111m, 111y, and 111k can be prevented. Therefore, so long as the phase difference variation of time _t 0 ~t ₂ other colors of the tip-side synchronization detection signal DETP2_N, it is possible to prevent the photosensitive member 111c, 111m, 111y, unnecessary irradiation to 111k. Here, (t ₃ −t ₄ ) = (t ₀ −t ₂ ).

In other words,
T + α + (phase difference variation time) ≦ (1 line cycle) (1)
If so, unnecessary irradiation to the photoconductors 111c, 111m, 111y, and 111k can be prevented. Here, T is the time from the leading end side synchronization detection signal DETP_N of the own color to the end of the photoconductors 111c, 111m, 111y, 111k on the main scanning rear end side.

  Note that when one polygon mirror 135 is used as in the present embodiment, it is considered that there is very little phase difference variation due to a change with time as described above. However, since the phase difference is different for each individual image forming apparatus 100, the timing for asserting the forced lighting signal BD in the mode B in which the forced lighting signal BD is asserted from the front-end side synchronization detection signal DETP2_N of other colors is, for example, It is measured and set for each individual image forming apparatus 100 in the factory.

For example, in consideration of the phase difference variation, the factory measures the phase difference a plurality of times, and sets the timing for asserting the forced lighting signal BD based on the median value of the phase difference variation. FIG. 10 is a waveform diagram showing the operation of the sync detection lighting control unit 346. Referring to FIG. 10, the timing at which the forced lighting signal BD is asserted is the self-color front end side synchronization detection signal DETP_N (time t ₁₃ ) and the photosensitive members 111c, 111m, 111y, and 111k when the measured median phase difference is present. Is set at the center (time t ₁₂ ) with respect to the rear end (time t ₁₁ ) in the main scanning direction. That is, if the times t _{11 to} t ₁₃ are X, the times t _{12 to} t ₁₃ are set to X / 2.

Also, for example, in the factory, the self-color front end side synchronization detection signal DETP_N and the other color front end side synchronization detection signal DETP2_N are measured for each individual image forming apparatus 100, and the forced lighting signal BD is expressed by the following equation (2). Set the timing to assert. In this case, the phase difference variation time is set to about 5 mm in image height.
(Timing to assert BD)
= (Time from DETP2_N to DETP_N)-(α + phase difference variation time)
... (2)
Here, α is a normal LD lighting time (generally, the light is turned on 5 to 3 mm before the tip side synchronization detection signal DETP_N), and the phase difference variation time is a scanning time of about 5 mm.

  FIG. 11 is a flowchart showing the writing initial operation after the power of the image forming apparatus 100 is turned on. First, as step S100, various GAVD settings such as a write clock are set. Next, as step S102, the rotation of the polygon mirror 135 is turned on. Next, as step S104, the tip side synchronization detection signal DETP_N is detected in mode A for K (black) color. Here, for the K color, since the front end side synchronization detection signal DETP_N is detected in the mode A, unnecessary irradiation is performed on the photoconductor 111k. In order to solve this, for example, a configuration may be adopted in which a shutter is provided on the exit window of the writing unit for only the K color. Next, in the case of color printing, in step S106, for the C (cyan) color, M (magenta) color, and Y (yellow) color, the K leading edge side synchronization detection signal DETP_N is used as the leading edge side synchronization detection signal of another color. Used as DETP2_N, detects the self-colored tip side synchronization detection signal DETP_N in mode B. In this case, the K-color front end side synchronization detection signal DETP_N is used as the phase difference when setting the timing for asserting the forced lighting signal BD at the factory.

  FIG. 12 is a flowchart showing the transition operation from the monochrome printing mode to the color printing mode. In the monochrome printing mode, the C, M, and Y LDs 132c, 132m, and 132y are turned off. Therefore, in step S108, the front end side synchronization detection signal DETP_N of K color is used as the front end side synchronization detection signal DETP2_N of other colors for the C color, M color, and Y color, and the front end side synchronization detection of the own color is performed in mode B. A signal DETP_N is detected.

  FIG. 13 is a waveform diagram showing the leading end side synchronization detection signal DETP_N and the forced lighting signal BD when the clock frequency is changed. As the clock frequency becomes faster or slower, the assertion timing of the forced lighting signal BD becomes faster or slower with respect to the front end side synchronization detection signal DETP_N. Therefore, as shown by hatching in FIG. Unnecessary irradiation occurs.

  FIG. 14 is a flowchart showing the magnification correction operation by changing the clock frequency. Here, it is assumed that Y magnification correction is performed. First, as step S110, the time from the Y-color front end side synchronization detection signal DETP_N to the rear end side synchronization detection signal EDETP_N is measured. A clock frequency setting, which is a correction value, is calculated from the measurement result. Next, in order to prevent unnecessary irradiation of the photosensitive member 111y as described with reference to FIG. 13 because the clock frequency becomes temporarily unstable due to the frequency change, the Y-color LD 132y is set as step S112. Turns off. Thereafter, the frequency is set in the PLL 342, and the time for the clock frequency to stabilize is waited. In step S114, lighting of the Y-color LD 132y is started in mode B using the K-color tip-side synchronization detection signal DETP_N as the other-color tip-side synchronization detection signal DETP2_N.

  Next, the operation at the time of LD initialization will be described. FIG. 15 is a waveform diagram showing an operation during LD initialization. When the LD 132 is in the off state at the initial stage and the leading edge side synchronization detection signal DETP2_N of another color is input after the LDON signal is asserted, the lighting control unit 346 for synchronization detection outputs the leading edge side synchronization detection signal of the other color. The BD counter is counted up using DETP2_N as a trigger, and an initialization lighting signal is asserted when the BD counter reaches a set value. At that time, initialization is not performed for the region where the return light from the polygon surface of the polygon mirror 135 exists. In addition, initialization is preferably performed outside the image area (to prevent unnecessary irradiation of the photosensitive member), and thus is performed at the position shown in FIG. In addition, in order to perform initialization lighting outside the image area, in this example, initialization is performed over a period of three lines. This period is determined from the initialization completion time of the LD driver 131, the area outside the image area, and the return light area.

  After that, the synchronization detection lighting control unit 346 starts asserting the forced lighting signal BD in order to detect the leading color synchronization detection signal DETP_N of the own color. In this example, the initialization lighting is performed at a position where the front end synchronization detection signal DETP_N of the own color is not input, but the initialization lighting is performed at a position where the front end synchronization detection signal DETP_N of the own color is input. Also good. In this case, the synchronization detection lighting control unit 346 may ignore the self-colored tip side synchronization detection signal DETP_N. The LD driver 131 changes the internal light quantity control reference voltage during the period when the initialization lighting signal is asserted, examines the characteristics of the laser, and determines the initial value of the current value for obtaining the target light emission amount.

  FIG. 16 is a flowchart showing an initialization operation in the actual image forming apparatus 100. After the power is turned on, initial setting of the GAVD 310 is performed as step S120. Next, as step S122, the GAVD 310 rotates the polygon mirror 135. Thereafter, as step S124, the GAVD 310 lights the K-color LD 132k in the mode A with the provisional LD light quantity. Since the LD light quantity at this time does not form an image, it may be an appropriate light quantity to the extent that the front-end side synchronization detection signal DETP_N of its own color is input. Next, in step S126, the GAVD 310 initializes the C color, M color, and Y color LDs 132c, 132m, and 132y in mode B using the K color front end side synchronization detection signal DETP_N as the other color front end side synchronization detection signal DETP2_N. To do. After that, in step S128, the K-color LD 132k is initialized in mode B with the C-color, M-color, or Y-color front-end synchronization detection signal DETP_N as the other-color front-end synchronization detection signal DETP2_N.

  In the above description, the case where the image forming apparatus includes one Bolgon mirror has been described. However, the image forming apparatus may include two polygon mirrors. FIG. 17 is a diagram illustrating a configuration of an image forming apparatus including two polygon mirrors. As shown in FIG. 17, when two polygon mirrors 135 and 135a are provided, the same rotation clock signal is used for the two polygon mirrors 135 and 135a. By making the rotation clock signal common, the phase difference between the two polygon mirrors 135 and 135a is always substantially the same. FIG. 18 is a diagram showing a configuration of a writing unit when two polygon mirrors are provided. When two polygon mirrors 135 and 135a are provided, two sets of writing units for writing two colors with one polygon mirror 135 shown in FIG. 18 can be provided to support four-color color tandem.

  FIG. 19 is a block diagram illustrating a hardware configuration of the image forming apparatus according to the present embodiment. As shown in the figure, the image forming apparatus 100 has a configuration in which a controller 410 and an engine unit (Engine) 460 are connected by a PCI (Peripheral Component Interface) bus. The controller 410 is a controller that controls the entire image forming apparatus 100 and controls drawing, communication, and input from an operation unit (not shown). The engine unit 460 is a printer engine that can be connected to a PCI bus, and is, for example, a monochrome plotter, a one-drum color plotter, a four-drum color plotter, a scanner, or a fax unit. The engine unit 460 includes an image processing part such as error diffusion and gamma conversion in addition to a so-called engine part such as a plotter.

  The controller 410 includes a CPU 411, a north bridge (NB) 413, a system memory (MEM-P) 412, a south bridge (SB) 414, a local memory (MEM-C) 417, and an ASIC (Application Specific Integrated Circuit). 416 and a hard disk drive (HDD) 418, and the north bridge (NB) 413 and the ASIC 416 are connected by an AGP (Accelerated Graphics Port) bus 415. The MEM-P 412 further includes a ROM (Read Only Memory) 412a and a RAM (Random Access Memory) 412b.

  The CPU 411 performs overall control of the image forming apparatus 100, has a chip set including the NB 413, the MEM-P 412, and the SB 414, and is connected to other devices via the chip set.

  The NB 413 is a bridge for connecting the CPU 411 to the MEM-P 412, SB 414, and AGP 415, and includes a memory controller that controls reading and writing to the MEM-P 412, a PCI master, and an AGP target.

  The MEM-P 412 is a system memory used as a memory for storing programs and data, a memory for developing programs and data, a memory for drawing a printer, and the like, and includes a ROM 412a and a RAM 412b. The ROM 412a is a read-only memory used as a memory for storing programs and data, and the RAM 412b is a writable and readable memory used as a program / data development memory, a printer drawing memory, and the like.

  The SB 414 is a bridge for connecting the NB 413 to a PCI device and peripheral devices. The SB 414 is connected to the NB 413 via a PCI bus, and a network interface (I / F) unit and the like are also connected to the PCI bus.

  The ASIC 416 is an IC (Integrated Circuit) for image processing having hardware elements for image processing, and has a role of a bridge for connecting the AGP 415, the PCI bus, the HDD 418, and the MEM-C 417, respectively. The ASIC 416 includes a PCI target and an AGP master, an arbiter (ARB) that forms the core of the ASIC 416, a memory controller that controls the MEM-C 417, and a plurality of DMACs (Direct Memory) that rotate image data using hardware logic. (Access Controller) and a PCI unit that performs data transfer between the engine unit 460 via the PCI bus. The ASIC 416 is connected to an FCU (Facile Control Unit) 430, a USB (Universal Serial Bus) 440, and an IEEE 1394 (the Institute of Electrical and Electronics 94) via a PCI bus. The operation display unit 420 is directly connected to the ASIC 416.

  The MEM-C 417 is a local memory used as an image buffer for copying and a code buffer, and an HDD (Hard Disk Drive) 418 is a storage for storing image data, programs, font data, and forms. It is.

  The AGP 415 is a bus interface for a graphics accelerator card that has been proposed to speed up graphics processing, and speeds up the graphics accelerator card by directly accessing the MEM-P 412 with high throughput. .

  The program executed by the image forming apparatus according to the present embodiment is provided by being incorporated in advance in a ROM or the like. A program executed in the image forming apparatus according to the present embodiment is a file in an installable format or an executable format, and is a computer such as a CD-ROM, a flexible disk (FD), a CD-R, or a DVD (Digital Versatile Disk). The information may be provided by being recorded on a recording medium that can be read by the user.

  Furthermore, the program executed by the image forming apparatus according to the present embodiment may be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network. Further, the program executed by the image forming apparatus of the present embodiment may be provided or distributed via a network such as the Internet.

  The program executed by the image forming apparatus according to the present embodiment has a module configuration including the above-described units (VPU 304, IPU 306, and GAVD 310). As actual hardware, a CPU (processor) executes a program from the ROM. By reading and executing, each unit is loaded on the main memory, and each unit is generated on the main memory.

  In the above embodiment, the image forming apparatus of the present invention has been described by taking an example in which the image forming apparatus is applied to a multifunction machine having at least two functions among a copy function, a printer function, a scanner function, and a facsimile function. The present invention can be applied to any image forming apparatus such as a printer, a scanner apparatus, and a facsimile apparatus.

100 Image forming apparatus 302 Scanner unit 304 VPU
306 IPU
308 Printer section 310 GAVD
131 LD driver 132 LD
320 CPU
322 RAM
324 ROM
326 Image storage 328 Interface 329 I / O control 330 Main control unit

JP 2005-193611 A

Claims (8)

An image forming apparatus for forming an image composed of a plurality of colors,
A plurality of photoreceptors respectively used for forming the plurality of colors;
A plurality of light emitting sources for outputting light beams respectively used for forming the plurality of colors;
Deflection means for deflecting light beams output from the plurality of light emitting sources in a main scanning direction of the plurality of photosensitive members by a plurality of deflection surfaces;
A plurality of detection means disposed at the ends of the plurality of photoconductors, respectively, for detecting light beams deflected by the deflection means;
Control means for controlling lighting of the plurality of light emitting sources;
With
The control means includes
After a predetermined time has elapsed since one of the plurality of detection means detects a light beam used to form a color other than the control target color, the control target color of the plurality of light emission sources is formed. When the light source to be used is turned on and the other one of the plurality of detection means detects the light beam used for forming the color to be controlled, the color of the color to be controlled among the plurality of light source is detected. An image forming apparatus that performs first control to turn off a light emitting source used for forming. The control means includes
After execution of the first control, after a predetermined time elapses after another one of the plurality of detection means detects a light beam used for forming the color to be controlled, When the light source used for forming the color to be controlled is turned on and the other one of the plurality of detection means detects the light beam used for forming the color to be controlled, the plurality of light source 2. The image forming apparatus according to claim 1, wherein second control is performed to turn off a light emitting source used for forming the color to be controlled. Clock generation means for supplying a clock signal to the control means;
The control means includes
The clock signal operates in synchronization with the clock signal, and the frequency of the clock signal is unstable with a change in the frequency of the clock signal. The image forming apparatus according to claim 1, wherein the first control is executed and then the second control is executed. The control means includes
The initialization operation for adjusting the light emission amounts of the plurality of light emitting sources in the light-off state is executed by the first control, and then the second control is executed. The image forming apparatus according to claim 1.   5. The image forming apparatus according to claim 1, further comprising: one of the deflecting units, wherein the one deflecting unit deflects the light beams output from the plurality of light emitting sources. 6. .   Two or more deflecting units are provided, the two or more deflecting units operate in synchronization with the same clock signal, and a light beam output from one of the plurality of light emitting sources emits the plurality of light emitting units. The image forming apparatus according to claim 1, wherein the image forming apparatus is deflected by the deflecting unit different from a light beam output from another one of the sources. A plurality of photoconductors respectively used for forming a plurality of colors, a plurality of light sources for outputting light beams respectively used for forming the plurality of colors, and a plurality of light beams output from the plurality of light sources. Deflection means for deflecting in the main scanning direction of the plurality of photoconductors by a deflection surface; a plurality of detection means for detecting the light beams deflected by the deflection means, which are respectively disposed at end portions of the plurality of photoconductors; A control means for controlling lighting of the plurality of light emitting sources, and an image forming method executed by an image forming apparatus comprising:
After a predetermined time has elapsed since one of the plurality of detection means detects a light beam used to form a color other than the control target color, the control target color of the plurality of light emission sources is formed. Turning on the light source used;
When the other one of the plurality of detection means detects a light beam used for forming the color to be controlled, the light source used for forming the color to be controlled among the plurality of light emission sources is turned off. A process of
An image forming method comprising: A plurality of photoconductors respectively used for forming a plurality of colors, a plurality of light sources for outputting light beams respectively used for forming the plurality of colors, and a plurality of light beams output from the plurality of light sources. Deflection means for deflecting in the main scanning direction of the plurality of photoconductors by a deflection surface; a plurality of detection means for detecting the light beams deflected by the deflection means, which are respectively disposed at end portions of the plurality of photoconductors; An image forming program executed by an image forming apparatus comprising: a control unit that controls lighting of the plurality of light emitting sources;
After a predetermined time has elapsed since one of the plurality of detection means detects a light beam used to form a color other than the control target color, the control target color of the plurality of light emission sources is formed. Illuminating the light source used;
When the other one of the plurality of detection means detects a light beam used for forming the color to be controlled, the light source used for forming the color to be controlled among the plurality of light emission sources is turned off. Step to
An image forming program comprising:

Images