JP4646994B2 - Light beam scanning apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a light beam scanning device and an image forming apparatus equipped with the light beam scanning device, and more particularly to phase control of a pixel clock in the light beam scanning device.

  In an image forming apparatus using a light beam scanning device, a light beam is modulated by image data, a deflecting means (hereinafter referred to as a polygon mirror) is rotated to deflect at a constant angular velocity in the main scanning direction, and a constant angular velocity is deflected by an fθ lens. Is corrected to uniform velocity deflection, and is scanned on an image carrier (hereinafter referred to as a photoconductor).

  However, there is a problem that the image magnification varies from machine to machine due to variations in the characteristics of the light beam scanning device, particularly the characteristics of the lens. When a plastic lens is used, the shape and refractive index of the plastic lens change due to changes in the environmental temperature, changes in the in-machine temperature, and the like. For this reason, the scanning position on the image surface of the photoconductor changes, a magnification error occurs in the main scanning direction, and a high-quality image cannot be obtained. Furthermore, in an apparatus that forms a plurality of color images using a plurality of laser beams and a plurality of lenses, a color shift occurs due to the respective magnification errors, and a high-quality image cannot be obtained. Therefore, it is necessary to match the image magnification of each color as much as possible.

  Therefore, in the invention described in Patent Document 1, not only variable control of the frequency of a lighting control clock (hereinafter also referred to as a pixel clock) of a light emitting source that is controlled to light according to image data is performed, but also the phase is variably controlled. As a result, the image magnification in the main scanning direction is corrected to prevent deterioration in image quality.

  In recent years, in light beam scanning devices and image forming devices, printing speeds and resolutions have increased, and along with this, the transfer rate of image data has also increased, and radiation noise associated with high-speed signal transfer using cables has been increased. Suppression is required.

Therefore, in the invention described in Patent Document 2, measures against EMI are further strengthened by inserting a filter on an image data line of a low amplitude differential signal (LVDS) and performing signal transmission. Further, the image data is corrected by changing the data input to the control unit that generates the small-amplitude differential signal for the change in the image data due to the filter insertion, thereby preventing the degradation of the image quality as much as possible.
JP 2004-295083 A JP 2006-205404 A

  However, when the filter is inserted into the LVDS line, the signal waveform naturally becomes dull, and the input data is changed to correct the image data in order to eliminate the influence, but the state before the filter insertion is completely restored. Not only that, but it will have an effect. Naturally, the higher the pulse signal, the greater the influence, and the image quality is reduced by the influence.

  Therefore, the problem to be solved by the present invention is to spread the pixel clock frequency with a simple configuration that does not use a filter, suppress radiation noise, and prevent image quality from being degraded.

In order to solve the above problems, the first means includes a light source that is controlled to be turned on according to image data, a deflecting unit that deflects a light beam output from the light source in the main scanning direction, and a light source that is turned on. In the light beam scanning apparatus having the control means for variably controlling the phase of the clock for the light source, the control means turns on the light source when the light source has a light extinction period of two or more clocks. The phase of the control clock is changed , and a clock whose phase is advanced and a clock whose phase is delayed are set in the plurality of lighting control clocks to be changed, and the lighting control clock is moved within the extinction period. The amount of advance and the amount of delay are the same amount .
In this case, the control means changes the phase of the lighting control clock of the light emitting source outside the scanning area of the image data from when the synchronization detection signal is output until the scanning area is started. Further, the control unit changes a phase variable amount per clock of the lighting control clock of the light emitting source, and changes the phase variable amount in a plurality of periods in which lighting by image data is not performed.
The second means is characterized in that the image forming apparatus includes the light beam scanning device according to the first means.

  In the embodiment described later, the light source is the LD unit 120, the changing means is the polygon mirror 101, the control means for variably controlling the phase of the light emission source lighting control clock is the pixel clock generator 202, and the light beam scanning. The devices correspond to 1 respectively.

According to the present invention, even if phase control is performed in the image area, the image position is not shifted, and the image writing position is not shifted .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram illustrating a main part of an image forming apparatus according to Example 1 of the present embodiment. In FIG. 1, a light beam scanning device (optical unit) 1 configured as an optical unit includes a laser diode (hereinafter referred to as LD) that is turned on in accordance with image data, and a laser beam (hereinafter referred to as light beam) emitted from the LD. (Also referred to as) a collimating lens (not shown) that converts L into a parallel beam, a cylinder lens (not shown) that focuses in a line parallel to the sub-scanning direction, and a polygon mirror 101 that receives light from the cylinder lens and deflects the light. A polygon motor 102 that rotationally drives the polygon mirror 101 at a high speed, an fθ lens 103 that converts a constant angular velocity scan into a constant velocity scan, a BTL lens 104, and a mirror 105. With such a configuration, the light beam L emitted from the LD is converted into a parallel beam by a collimator lens (not shown), is deflected by the polygon mirror 101 that is rotated by the polygon motor 102 through the cylinder lens, Then, the light is reflected by the folding mirror 105 and scanned on the photosensitive member 106. BTL is an abbreviation for Barrel Toroidal Lens, and performs focusing in the sub-scanning direction (condensing function and position correction in the sub-scanning direction (surface tilt, etc.)).

  Around the photoconductor 106, a charger 107, a developing unit 108, a transfer unit 109, a cleaning unit 110, and a static eliminator 111 are arranged, and these constitute an image forming means, and charging, which is a normal electrophotographic process, An image is formed on the recording paper P by exposure, development, and transfer. Then, the image on the recording paper P is fixed by a fixing device (not shown).

  FIG. 2 is a schematic configuration diagram illustrating a light beam scanning device, an image formation control unit, and an optical unit in the image forming apparatus. In this figure, a peripheral control system is added to the plan view of the laser beam scanning device 1 of FIG. 1 as viewed from above. As a control system, a printer control unit 201, a pixel clock generation unit 202, a synchronization detection lighting control unit 204, an LD drive unit 205, and a polygon motor drive control unit 206 are provided. The pixel clock generator 202 further includes a reference clock generator 2021, a VCO (Voltage Controlled Oscillator) clock generator 2022, and a phase-synchronized clock generator 2023. Further, a synchronization detection sensor 123 that detects the light beam L on the scanning start side in the main scanning direction of the light beam scanning apparatus 1 is provided. Thus, the light beam L emitted from the LD unit 120, reflected by the polygon mirror 101 and transmitted through the fθ lens 103 is reflected by the mirror 121, collected by the lens 122, and incident on the synchronization detection sensor 123.

  In this configuration, when the light beam L passes over the synchronization detection sensor 123, a synchronization detection signal XDETP is output from the synchronization detection sensor 123 and sent to the pixel clock generation unit 202 and the synchronization detection lighting control unit 204.

  The pixel clock generation unit 202 generates a pixel clock PCLK synchronized with the synchronization detection signal XDETP, and sends the pixel clock PCLK to the LD control unit 205 and the synchronization detection lighting control unit 204. As described above, the pixel clock generation unit 202 includes the reference clock generation unit 2021, the VCO clock generation unit 2022, and the phase synchronization clock generation unit 2023.

FIG. 3 is a block diagram showing the configuration of the VCO clock generator (PLL circuit: Phase Locked Loop) 2022. The VCO clock generator 2022 inputs the reference clock signal FREF from the reference clock generator 2021 and a signal obtained by dividing VCLK by N by the 1 / N divider 20221 to the phase comparator 20222. The phase comparison of the falling edge of the signal is performed, and the error component is output at a constant current. Then, an unnecessary high frequency component and noise are removed by an LPF (low pass filter) 20223 and sent to the VCO 20224. The VCO 20224 outputs an oscillation frequency depending on the output of the LPF 20223. Therefore, the frequency of VCLK can be changed by changing the frequency of FREF and the frequency division ratio: N from the printer control unit 201.
The phase synchronization clock generation unit 2023 generates a pixel clock PCLK from VCLK set to a frequency eight times the pixel clock frequency, and further generates a pixel clock PCLK synchronized with the synchronization detection signal XDETP. Further, the frequency of VCLK can be changed by changing the frequency of FREF and the frequency division ratio: N from the printer control unit 201, and thus the frequency of the pixel clock PCLK can also be changed. Then, the overall magnification of the image can be changed by changing the frequency of the pixel clock PCLK.

  The synchronization detection lighting control unit 204 first turns on the LD forced lighting signal BD to forcibly light the LD in order to detect the synchronization detection signal XDETP. However, after detecting the synchronization detection signal XDETP, the synchronization detection signal XDETP is detected. With the XDETP and the pixel clock PCLK, the LD is turned on at a timing at which the synchronization detection signal XDETP can be reliably detected without causing flare light. The data is sent to the LD control unit 205.

  The LD control unit 205 generates LD lighting data synchronized with the pixel clock PCLK from the synchronous detection forcible lighting signal BD and the input image data, converts it to LVDS, and sends it to the LD driving unit of the LD unit 120. . The LD driving unit controls the lighting of the LD according to the LD lighting data with the light amount set by the printer control unit 201. Then, a laser beam is emitted from the LD unit 120, deflected by the polygon mirror 101, passes through the fθ lens 103, and scans on the photosensitive member 106. The polygon motor control unit 206 controls the rotation of the polygon motor so as to maintain a prescribed number of rotations based on a control signal from the printer control unit 201.

  FIG. 4 is a timing chart showing the output timing of the pixel clock PCLK. The upper side shows the timing before the phase change, and the lower side shows the timing after the phase change. With respect to the correction data from the printer control unit 201, in this embodiment, no correction is made in the case of “00b”, the phase is delayed by 1/16 PCLK in the case of “01b”, and 1/16 PCLK in the case of “10b”. Only trying to advance the phase. The correction data is sent in synchronization with the pixel clock PCLK, and the phase is changed at the next rising edge of PCLK.

  If the phase is delayed, it is necessary to advance the phase by the same amount. Therefore, the phase is not changed in the light-off period (period in which there is no image data) of only one clock, and the phase is changed when there is a light-out period of 2 clocks or more (in this embodiment, 4 clocks). In the example of FIG. 4, the phase of the rising edge is delayed by a half period of VCLK, that is, 1/16 PCLK in the first clock when the light is turned off (A). Delay the phase (B)). In the third clock, the phase of the rising edge is advanced by 1/16 PCLK (C), and in the fourth clock, the phase of the rising edge is advanced by 1/16 PCLK (D). It is possible to make the lighting timing the same as before the phase is changed (variable control of the phase is performed), and as a result, no image shift occurs.

  In this embodiment, the phase is first delayed during the extinguishing period (FIGS. 4-A and B) and then advanced (FIGS. 4-C and D). However, the present invention is not limited to this, and vice versa. No problem.

  FIG. 5 is a timing chart showing the output timing of the pixel clock PCLK in the second embodiment. The image forming apparatus, the light beam scanning apparatus, and the image forming control unit are the same as those in the first embodiment shown in FIGS.

  In the timing chart of FIG. 5, the upper side shows the timing before the phase change, and the lower side shows the timing after the phase change. It differs from the first embodiment only in the amount of phase change. In the case of this embodiment, no correction is made in the case of “000b”, and PCLK has a cycle of 8 times VCLK. However, in the case of “001b”, the phase is delayed by 1/16 PCLK, and in the case of “010b”, 2 The phase is delayed by / 16 PCLK. In the case of “011b”, the phase is delayed by 3/16 PCLK. In the case of “100b”, the phase is advanced by 1/16 PCLK. In the case of “101b”, the phase is advanced by 2/16 PCLK. In the case of “110b”, the phase is advanced by 3/16 PCLK.

  As in the first embodiment, the phase is changed when there is no image data, that is, when the LD is not turned on (when the light is turned off), but when there is a turn-off period of two clocks or more (four clocks in this embodiment). Will change the phase.

  In the example of FIG. 5, the phase of the rising edge is delayed by a half cycle of VCLK, that is, 1/16 PCLK in the first clock when the light is turned off (E), and the rising edge is delayed by 2/16 PCLK in the second clock. Delay the phase (F). In the third clock, the phase of the rising edge is advanced by 1/16 PCLK (G), and in the fourth clock, the phase of the rising edge is advanced by 2/16 PCLK (H). The lighting timing can be made the same as the state before the phase is changed, and no image shift occurs.

  In this embodiment, the phase is first delayed during the extinguishing period (FIGS. 5-E and F) and then advanced (FIGS. 5-G and H). However, the present invention is not limited to this, and vice versa. No problem. Further, the amount of phase change is not limited to this.

  Other parts not specifically described are configured in the same manner as in the first embodiment and function in the same manner.

  FIG. 6 is a timing chart showing the output timing of the synchronization detection signal in the main scanning direction in the third embodiment. The image forming apparatus, the light beam scanning apparatus, and the image forming control unit are the same as those in the first embodiment shown in FIGS.

  As can be seen from the timing chart in the main scanning direction of FIG. 6, the synchronization detection signal XDETP is output once per scan, and the non-image area 1 is next to the effective image area between the synchronization detection signal XDETP and the effective image area. There is a non-image area 2 between the scanning line synchronization detection signal XDETP. Since neither the non-image area 1 nor the non-image area 2 has image data, the phase of the pixel clock can be changed as in the first and second embodiments. Since the control method of the phase variable control is the same as that in the first and second embodiments, a duplicate description is omitted.

  For the non-image region 1, the change in the phase of the pixel clock affects the image data in the effective image region, so that the amount of phase delay and the amount of advancement need to be the same as in the first and second embodiments. However, for the non-image area 2, the pixel clock whose phase has been changed is synchronized again by the synchronization detection signal XDETP of the next scanning line, and therefore does not affect the image of the next scanning line. Therefore, for the non-image area 2, it is not necessary to make the amount of phase delay and the amount of advancement the same. However, since the LD lighting signal BD is generated by the pixel clock, it is necessary to generate the LD forcible lighting signal BD for lighting the LD at a timing at which the synchronization detection sensor 123 can reliably detect the light beam even if the phase control is performed. is there.

  Other parts not specifically described are configured in the same manner as in the first embodiment and function in the same manner.

  FIG. 7 is a flowchart illustrating a control procedure of the printer control unit 201 according to the fourth embodiment. This control is performed by a CPU (not shown) of the printer control unit 201 executing a program stored in a ROM (not shown) while using a RAM (not shown) as a work area. The image forming apparatus, the light beam scanning apparatus, and the image forming control unit are the same as those in the first embodiment shown in FIGS.

  In FIG. 7, in this embodiment, in standby mode, that is, the time from when the power is turned on until the start of image formation, the time from the end of image formation to the start of the next image formation, the time from the end of image formation to the time when the power is turned off. For LD, the LD is turned on to detect the rotation of the polygon motor and the synchronization detection signal XDETP.

  Therefore, first, the polygon motor is rotated at a specified number of rotations (step S101). Then, the pixel clock is set (step S102), the phase control of the pixel clock (step S103) is performed, the LD lighting signal BD is generated to detect the synchronization detection signal XDETP, and the LD is turned on (step S104). Regarding the phase control of the pixel clock here, the control method is the same as in the first and second embodiments, but since there is no image data, the phase can be changed at an arbitrary position in one scan. There is no need to make the amount of delaying and the amount of advancement the same. When starting the image forming operation (step S105), the phase control of the pixel clock is stopped (step S106), the image forming operation is executed (step S107), and after the image forming operation is completed (step S108-N), The phase control of the pixel clock is started again (step S109).

  Note that when the image forming operation is started (step S105), the phase control of the pixel clock is stopped (step S106), but the control method of the first and second embodiments is performed during the image forming operation. There is no problem.

  Further, as shown in the flowchart of FIG. 8, it is possible to prevent the polygon motor, LD lighting, and pixel clock generation from being performed during standby. That is, from step S101 to step S109, the same processing as in the flowchart of FIG. 4 is performed. After starting the pixel clock phase control in step S109, the LD is turned off (step S110), and the pixel clock is also stopped (step S111). In addition, the polygon motor is also stopped (step S112). In other words, in the example of FIG. 8, the image forming operation is completed after the start (printing) of the image forming operation is instructed and until the image forming operation is actually started, and all the operations are completely stopped. Until then, the phase control of the pixel clock is performed.

  In this case as well, when the image forming operation is started (step S105), the phase control of the pixel clock is stopped (step S106). However, if the control method of the first embodiment and the second embodiment is used, image formation is performed. There is no problem even if it is done during operation.

  Other parts not specifically described are configured in the same manner as in the first embodiment and function in the same manner.

  FIG. 9 is a timing chart showing the operation timing of the image forming operation in the fifth embodiment. The image forming apparatus, the light beam scanning apparatus, and the image forming control unit are the same as those in the first embodiment shown in FIGS.

  In FIG. 9, the polygon rotation signal XPMON output from the polygon motor drive control unit 206 is turned on (“H” level → “L” level) by a print start instruction, and is turned off (“L” level) by a print end instruction. → 'H' level). As for the gate signal XFGATE for determining the image writing start timing and the image length in the sub-scanning direction, the image writing operation is performed in the ‘L’ level section.

  The “A” period and the “C” period in FIG. 9 correspond to the period for performing the phase control of the pixel clock in the fourth embodiment, and in this embodiment, correspond to the interval between images (between sheets) during continuous printing. The phase control of the pixel clock is also performed during the “B” period. Regarding the phase control of the pixel clock, the control method is the same as in the first or second embodiment, but since there is no image data, the phase can be varied at any point in one scan, and the amount of phase delay It is not necessary to have the same amount to be advanced.

  FIG. 10 is a timing chart showing the operation timing of the 4-page image forming operation. In the figure, the polygon rotation signal XPMON is turned ON (“H” level → “L” level) by a print start instruction, and turned OFF (“L” level → “H” level) by a print end instruction. As for the gate signal XFGATE for determining the image writing start timing and the image length in the sub-scanning direction, the image writing operation is performed in the ‘L’ level section. In this embodiment, an image forming operation for four pages is shown. In each page image, the phase of the pixel clock is variably controlled by the same control method as in the first and second embodiments. If the same image is repeatedly output, of course, pixels having no image data have the same timing between pages, but the phase amount is changed for each page at the same timing.

  Note that the phase control during the image writing operation can be performed as long as the control method of the first and second embodiments is used. Further, if there are a plurality of images (image intervals), the phase amount may be varied for each.

  Other parts not specifically described are configured in the same manner as in the first embodiment and function in the same manner.

  FIG. 11 is a diagram illustrating the phase variable amount of each pixel in the sixth embodiment. The image forming apparatus, the light beam scanning apparatus, and the image forming control unit are the same as those in the first embodiment shown in FIGS.

  In FIG. 11, one square corresponds to one pixel clock, and a black pixel means that there is image data (LD is lit). For a pixel having no image data, +1 delays the phase by 1/16 PCLK, +2 delays the phase by 2/16 PCLK, +3 delays the phase by 3/16 PCLK, -1 is 1 / It means that the phase is advanced by 16 PCLK, -2 means that the phase is advanced by 2/16 PCLK, and -3 means that the phase is advanced by 3/16 PCLK.

  In this embodiment, when the image data is not continuous for two pixel clocks or more, the phase is changed, and the change amount is changed for each.

  FIG. 12 is a diagram illustrating the phase variable amount of each pixel in a plurality of lines. The example shown in FIG. 12 differs from the example shown in FIG. 11 only in that the phase variable amount is changed for each scanning line. In both the case of FIG. 11 and the case of FIG. 12, the control method is the same as in the first and second embodiments.

  Other parts not specifically described are configured in the same manner as in the first embodiment and function in the same manner.

  FIG. 13 is a diagram showing a schematic configuration of an example of a color image forming apparatus provided with the light beam scanning device described in the first to sixth embodiments. Since the light beam scanning device and the image formation control unit are the same as those in the first embodiment, duplicate descriptions are omitted.

  The image forming apparatus according to the seventh embodiment shown in FIG. 13 performs optical writing by the light beam scanning device 1 according to the image data, and forms an electrostatic latent image on the photosensitive drum 106 as a latent image carrier. The photosensitive drum 106 rotates counterclockwise, but around the photosensitive drum cleaning unit 110, the static eliminator 111, the charger 107, and the developing unit (BK developing unit, C developing unit, M developing unit, Y developing unit). 108, an intermediate transfer belt 130 as a carrier, and the like are disposed.

  The developing unit 108 includes a developing sleeve 108a that rotates so that the developer faces the photosensitive drum 106 in order to develop the electrostatic latent image, and a developing paddle (not shown) that rotates to pump up and stir the developer. Etc. The intermediate transfer belt 130 is stretched between the driving roller 131, the driven roller 131 and the belt transfer bias roller 133, and is in contact with the surface of the photosensitive drum 106 by the belt transfer bias roller 133. A paper transfer unit 140 is disposed at a position facing the drive roller 131 with the intermediate transfer belt 130 interposed therebetween, and a paper transfer bias roller 141 of the paper transfer unit 140 is provided so as to face the intermediate transfer belt 130. Yes. In addition, a belt cleaning unit 132 for cleaning residual toner on the intermediate transfer belt 130 is provided at the rear stage of the driving roller 131 so as to be able to contact the intermediate transfer belt 130.

  The image forming operation of the image forming apparatus configured as described above is as follows. Here, the order of the developing operation is BK, C, M, Y here, but is not limited to this.

  When the printing operation is started, first, optical writing and latent image formation by the light beam scanning device 1 are started based on the BK image data. In order to enable development from the leading edge of the BK latent image, the developing sleeve 108a starts rotating before the latent image leading edge reaches the developing position of the BK developing device, and the BK latent image is developed with BK toner. Thereafter, the developing operation of the BK latent image area is continued, but the development inactive state is set when the rear end of the BK latent image passes the BK developing position. This is completed at least before the leading edge of the C latent image by the next C image data arrives.

  The BK toner image formed on the photosensitive drum 106 is transferred to the surface of the intermediate transfer belt 130 that is driven at the same speed as the photosensitive drum 106. This belt transfer is performed by applying a predetermined bias voltage to the belt transfer bias roller 133 while the photosensitive drum 106 and the intermediate transfer belt 130 are in contact with each other. The intermediate transfer belt 130 forms a belt transfer image by sequentially aligning the BK, C, M, and Y toner images sequentially formed on the photosensitive drum 106 on the same surface, and superimposing four colors. Batch transfer to paper P. In the photosensitive drum 106, the process proceeds to the C process after the BK process, and then continues to the M process and the Y process.

  As described above, the intermediate transfer belt 130 is wound around the drive roller 131, the belt transfer bias roller 133, and the driven roller 132, and is driven and controlled by a drive motor (not shown). The belt cleaning unit 132 includes a blade, a contact / separation mechanism, and the like, and prevents the blade from coming into contact with the belt by the contact / separation mechanism while the BK image, C image, M image, and Y image are transferred to the belt. ing.

  The paper transfer unit 140 includes a paper transfer bias roller 141 and a contact / separation mechanism. The paper transfer bias roller 141 is usually separated from the surface of the intermediate transfer belt 130, but is formed on the surface of the intermediate transfer belt 130. When the four-color superimposed image is collectively transferred to the recording paper P, it is pressed by the contact / separation mechanism, a predetermined bias voltage is applied, and the image is transferred to the recording paper P.

  The recording paper P is fed from a paper feeding unit (not shown) at the timing when the leading end of the four-color superimposed image on the surface of the intermediate transfer belt 130 reaches the paper transfer position. The toner image transferred to the recording paper P is fixed by a fixing unit (not shown).

  If the timing chart shown in FIG. 12 is replaced with this embodiment, the first page corresponds to black, the second page corresponds to cyan, the third page corresponds to magenta, and the fourth page corresponds to yellow. The variable phase control is the same as in the previous embodiment.

  In addition, each part which is not demonstrated especially is comprised similarly to the above-mentioned Example 1 thru | or 6, functions equivalently, and is controlled equally.

    FIG. 14 is a diagram showing a schematic configuration of another example of a color image forming apparatus provided with the light beam scanning apparatus described in the first to sixth embodiments. Since the light beam scanning device and the image formation control unit are the same as those in the first embodiment, duplicate descriptions are omitted.

  The image forming apparatus according to the eighth embodiment illustrated in FIG. 14 is a four-drum type image forming apparatus. The image forming apparatus includes four image forming units (photosensitive members) for forming a color image in which four color images of yellow (Y), magenta (M), cyan (C), and black (BK) are superimposed. A drum 106, a developing unit 108, a charger 107, a transfer device 109, a cleaning unit 110 (not shown) and four sets of optical units (laser beam scanning device 1) are provided. Therefore, the four image forming apparatuses shown in FIG. 1 are arranged, and the first color image is formed on the recording paper P conveyed in the direction of the arrow by the transfer belt B, and then the second color, the third color, By transferring the images in the order of the fourth color, a color image in which the four color images are superimposed is formed on the recording paper, and the image on the recording paper is fixed by a fixing device (not shown).

  The transfer belt B is stretched between the rollers R and is driven by a conveyance motor M. As for the optical unit, four sets shown in FIG. 2 are provided. Since the configuration and control of each optical unit 1 are the same as those in the first embodiment, description thereof will be omitted. The matters described in the first to sixth embodiments can also be applied to the image forming apparatus having this configuration. In this case, since the light beam scanning device and the image formation control unit are provided independently for each color, the same control is performed for each color.

  In addition, each part which is not demonstrated especially is comprised similarly to the above-mentioned Example 1 thru | or 6, functions equivalently, and is controlled equally.

  As described above, according to the present embodiment, EMI countermeasures can be performed with simple control, and good image quality can be guaranteed.

  Needless to say, the present invention is not limited to this embodiment, but covers all technical matters included in the technical idea described in the claims.

1 is a schematic configuration diagram illustrating a main part of an image forming apparatus according to Embodiment 1. FIG. 1 is a schematic configuration diagram illustrating a light beam scanning device, an image formation control unit, and an optical unit in an image forming apparatus according to Embodiment 1. FIG. FIG. 3 is a block diagram showing a configuration of a VCO clock generation unit in FIG. 2. It is a timing chart which shows the output timing of the pixel clock recorded from the pixel clock generation part. 6 is a timing chart illustrating the output timing of a pixel clock in Embodiment 2. 10 is a timing chart showing output timing of a synchronization detection signal in the main scanning direction in Embodiment 3. 10 is a flowchart illustrating a control procedure of a printer control unit according to a fourth embodiment. 16 is a flowchart illustrating another control procedure of the printer control unit according to the fourth embodiment. 10 is a timing chart illustrating the operation timing of an image forming operation in Embodiment 5. 12 is a timing chart illustrating the operation timing of an image forming operation for four pages in Embodiment 5. It is a figure which shows the phase variable amount of each pixel in Example 6. FIG. It is a figure which shows the phase variable amount of each pixel in the some line in Example 6. FIG. 1 is a diagram illustrating a schematic configuration of an example of a color image forming apparatus including a light beam scanning device described in Embodiments 1 to 6. FIG. FIG. 10 is a diagram illustrating a schematic configuration of another example of a color image forming apparatus including the light beam scanning device described in the first to sixth embodiments.

Explanation of symbols

1 Light Beam Scanning Device 101 Polygon Mirror 106 Photoconductor (Drum)
120 LD Unit 123 Synchronization Detection Sensor 201 Printer Control Unit 202 Pixel Clock Generation Unit 204 Synchronization Detection Lighting Control Unit 205 LD Control Unit 206 Polygon Motor Control Unit

Claims (5)

A light source that is controlled to light according to image data;
Deflection means for deflecting the light beam output from the light source in the main scanning direction;
In the light beam scanning device comprising a control means for variably controlling the phase of the lighting control lighting control clock,
The control means changes the phase of the lighting control clock of the light source when the light emitting source is turned off and the lighting control clock of the light source continues for two or more clocks, and the plurality of lighting control clocks to be changed are changed. The phase-advanced clock and the phase-delayed clock are set, and the amount of movement and the amount of delay of the lighting control clock movement within the extinction period are the same amount. Light beam scanning device. The light beam scanning apparatus according to claim 1.
The light beam scanning device characterized in that the control means changes a phase of a lighting control clock of the light emitting source outside a scanning region of image data from when a synchronization detection signal is output to when the scanning region is started. . The light beam scanning device according to claim 1 or 2 ,
The light beam scanning apparatus according to claim 1 , wherein the control means changes a phase variable amount per clock of a lighting control clock of the light emitting source . The light beam scanning apparatus according to claim 3 .
The light beam scanning device , wherein the phase variable amount is changed in each of a plurality of periods during which lighting by image data is not performed . An image forming apparatus comprising the light beam scanning device according to claim 4.

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