JP2007331147A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a sub-scanning shift of an amount of one plane of a polygon mirror at the time of imaging processing while a phase of each index signal is prevented from skipping that of a reference index signal even when the index signal of each color causes a drift variation following a temperature change. <P>SOLUTION: This image forming apparatus is equipped with an image forming part 80 which carries out imaging processing by rotating the polygon mirror 34 on the basis of a reference-IDX signal and scanning a laser beam light to a photoreceptor drum 1Y or the like, a phase difference detecting part which detects a phase difference between a YMCK-IDX signal obtained by detecting the laser beam light scanned by the image forming part 80 to the photoreceptor drum 1Y or the like and the reference-IDX signal, and a controlling part 15 which interrupts imaging processing on the basis of the result of comparison between the phase difference detected by the phase difference detecting part and a threshold for judgement on the phase difference, and then carries out polygon phase control of matching the phase difference with a predetermined target phase difference. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is suitable for application to a tandem type color printer or color copier having a photosensitive drum and an intermediate transfer belt, and having a color misregistration correction mode and a polygon phase control mode, and a color complex machine thereof. The present invention relates to an image forming apparatus.

  In recent years, tandem color printers, color copiers, and these color multifunction devices have been increasingly used. According to this type of color image forming apparatus, in order to maintain the print quality (color reproducibility) of the color image optimally, yellow (Y), magenta (reproducing R, G, and B colors of the original image). M), cyan (C), and black (BK) colors are superimposed on the intermediate transfer belt. In order to superimpose each color of Y, M, C, and BK with good reproducibility, it is indispensable to positively correct color misregistration in the image forming unit (hereinafter referred to as color misregistration correction mode).

  Regarding the color misregistration correction mode, a color misregistration detection mark (hereinafter referred to as a registration mark) for position detection formed on an intermediate transfer belt or a conveyance material transfer belt is used as a detection means (hereinafter referred to as a resist) such as a reflective sensor. Sensor), calculate the color misregistration amount of the other color resist marks relative to the reference color resist mark, and feed back to each of the Y, M, and C image forming units so as to eliminate this color misregistration amount. By correcting the writing timing of the laser beam light, a high-quality color image is obtained.

  With respect to this type of color copying machine, Patent Document 1 describes a light beam scanning device. According to this light beam scanning device, when phase control is performed in response to rotation irregularities of polygon mirrors and changes in the rotation irregularities with time, the phase control means generates a rotation reference signal for controlling the rotation speeds of a plurality of polygon mirrors. And detecting a phase difference between the reference signal and the beam detection signal a plurality of times during standby and determining a phase position based on the maximum phase difference. The rotation reference signal generation unit always outputs the output of the laser beam detector corresponding to the remaining polygon mirror first in accordance with the output of the laser beam detector corresponding to the reference polygon mirror. By configuring the light beam scanning device in this way, it is possible to prevent sudden image shift in the sub-scanning direction such as uneven rotation of the polygon mirror.

Japanese Patent Laid-Open No. 9-212367 (page 8 FIG. 4)

  By the way, according to the color image forming apparatus according to the conventional example, in the light beam scanning apparatus as shown in Patent Document 1, the rotation speed of the polygon mirror is slightly changed by the temperature change of the polygon motor or the like, and the beam detection is performed. If the signal phase drifts and drifts, the phase position of the beam detection signal of each image forming color adjusted by phase control may shift, resulting in a sub-scanning shift. In particular, when a phenomenon occurs in which the phase of a beam detection signal (hereinafter referred to as a scanning light detection signal) overtakes a reference signal (hereinafter referred to as an imaging scan reference signal), the image formation timing is shifted by one surface of the worst polygon mirror (hereinafter referred to as a polygon mirror). Thus, there is a risk of sub-scanning deviation for one scanning line.

  Therefore, the present invention solves the above-described problem, and the phase of the scanning light detection signal is changed to image-forming scanning even when the scanning light detection signal undergoes a drift fluctuation due to a temperature change of a polygon motor or the like. An object of the present invention is to provide an image forming apparatus capable of preventing a sub-scanning shift for one surface of a polygon mirror during image forming processing without jumping over a reference signal.

  In order to solve the above problems, an image forming apparatus according to claim 1 rotates a polygon mirror based on an image forming scanning reference signal, scans light with the polygon mirror, and performs image forming processing on the image carrier. An image forming unit for detecting the phase difference between a scanning light detection signal obtained by detecting light scanned by a polygon mirror of the image forming unit at a predetermined position and an image forming scanning reference signal; The control means for interrupting the image forming process based on the result of comparing the phase difference detected by the detecting means and the threshold for phase difference determination, and executing phase control for adjusting the phase difference to a predetermined target phase difference Are provided.

  According to the image forming apparatus of the first aspect, the image forming unit rotates the polygon mirror based on the image forming scanning reference signal, scans light with the polygon mirror, and performs image forming processing on the image carrier. The detecting unit detects a phase difference between a scanning light detection signal obtained by detecting light scanned by the polygon mirror of the image forming unit at a predetermined position and an image forming scanning reference signal. Based on this assumption, the control means interrupts the image forming process based on the result of comparing the phase difference detected by the detection means and the threshold value for phase difference determination, and adjusts the phase difference to a predetermined target phase difference. Execute phase control.

  Therefore, before the phase of the scanning light detection signal is delayed with respect to the image scanning reference signal and before the phase advances (before the phase is skipped), the image scanning reference signal and the scanning light detection signal are The phase difference between them can be adjusted to a predetermined target phase difference, and the image forming process can be resumed after the phase adjustment.

  The image forming apparatus according to claim 2, wherein a lower limit threshold and an upper limit threshold for phase difference determination are set in one cycle of the image forming scanning reference signal, and the control means includes the image forming scanning reference signal and the scanning light detection signal. When the phase difference between and the phase difference falls below the lower threshold or when the phase difference exceeds the upper threshold, the imaging process is interrupted and the phase difference between the imaging scanning reference signal and the scanning light detection signal is reduced. After adjusting to zero, the phase difference between the image forming scanning reference signal and the scanning light detection signal is adjusted to a predetermined target phase difference based on the sub-scan correction amount obtained by the color misregistration correction process.

  The image forming apparatus according to claim 3 rotates the polygon mirror based on the image forming scanning reference signal, scans the light with the polygon mirror, and performs image forming processing for color misregistration correction on the image carrier. Detecting means for detecting a phase difference between a scanning light detection signal obtained by detecting light scanned by a polygon mirror of the image forming means at a predetermined position and an image forming scanning reference signal; and the detecting means Control means for interrupting the color misregistration correction processing based on the result of comparing the phase difference detected by the step and the threshold value for phase difference determination and executing phase control for adjusting the phase difference to a predetermined target phase difference. It is characterized by this.

  According to the image forming apparatus of the third aspect, the image forming means rotates the polygon mirror based on the image forming scanning reference signal, and scans the light with the polygon mirror so that the image carrier can be used for color misregistration correction. Perform image processing. The detecting unit detects a phase difference between a scanning light detection signal obtained by detecting light scanned by the polygon mirror of the image forming unit at a predetermined position and an image forming scanning reference signal. Based on this assumption, the control unit interrupts the color misregistration correction process based on the result of comparing the phase difference detected by the detection unit and the threshold for phase difference determination, and sets the phase difference to a predetermined target phase difference. Execute phase control to be adjusted.

  Therefore, before the phase of the scanning light detection signal is delayed with respect to the image scanning reference signal and before the phase advances (before the phase is skipped), the image scanning reference signal and the scanning light detection signal are The phase difference between them can be adjusted to a predetermined target phase difference, and the color misregistration correction process can be resumed after the phase adjustment.

  According to the image forming apparatus of the fourth aspect, one cycle of the image forming scanning reference signal is divided into a plurality of unit adjustment amounts, and a lower limit adjustment range and an upper limit adjustment range for phase difference determination are set in the cycle. The control means, when the phase difference between the image forming scanning reference signal and the scanning light detection signal becomes less than half of the unit adjustment amount of the lower limit adjustment range, or when the phase difference is the unit adjustment amount of the upper limit adjustment range. When the value is over half, the color misregistration correction process is interrupted, and the phase difference between the image forming scan reference signal and the scanning light detection signal is adjusted by adjusting the phase difference between the image forming scan reference signal and the scanning light detection signal to zero. Perform alignment.

  According to the image forming apparatus of the first aspect, the image forming process is interrupted based on the result of comparing the phase difference between the image forming scanning reference signal and the scanning light detection signal with the threshold for phase difference determination. The phase control for adjusting the phase difference to a predetermined target phase difference is executed.

  With this configuration, before the phase of the scanning light detection signal is delayed from the state where the phase of the scanning light detection signal is delayed with respect to the image scanning reference signal (before the phase is skipped), the image scanning reference signal and the scanning light detection signal The phase difference between and can be matched with a predetermined target phase difference, and the image forming process can be resumed after the phase matching. Accordingly, even when the scanning light detection signal drifts due to a temperature change, the phase of the scanning light detection signal does not jump over the image forming scanning reference signal, and at the time of image forming processing, it corresponds to one surface of the polygon mirror. Sub-scanning deviation can be prevented.

  According to the image forming apparatus of claim 3, the color misregistration correction process is interrupted based on a result of comparing the phase difference between the image forming scanning reference signal and the scanning light detection signal with the threshold for phase difference determination. Then, phase control for adjusting the phase difference to a predetermined target phase difference is executed.

  With this configuration, before the phase of the scanning light detection signal is delayed from the state where the phase of the scanning light detection signal is delayed with respect to the image scanning reference signal (before the phase is skipped), the image scanning reference signal and the scanning light detection signal Can be matched with a predetermined target phase difference, and color misregistration correction processing can be resumed after phase matching. Therefore, even when the scanning light detection signal drifts due to a temperature change, the phase of the scanning light detection signal does not jump over the image forming scanning reference signal, and the color misalignment correction processing is performed for one surface of the polygon mirror. This makes it possible to prevent the sub-scanning deviation.

  Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a conceptual diagram showing a configuration example of a color copying machine 100 as an embodiment according to the present invention.

  A color copying machine 100 shown in FIG. 1 constitutes an example of a tandem type color image forming apparatus, and a polygon for each color based on a reference index signal (hereinafter referred to as a reference-IDX signal) as an example of an image forming scanning reference signal. An image forming process is performed on the photosensitive drum by rotating a mirror (polyhedral mirror) and scanning a laser beam for each color onto the photosensitive drum for each color. The toner images of the respective colors that have been subjected to image forming processing on the photosensitive drum are superimposed on the intermediate transfer belt to form a color image.

  The color copying machine 100 includes a copying machine main body 101 and an image reading device 102. An image reading device 102 including an automatic document feeder 201 and a document image scanning exposure device 202 is installed on the upper part of the copying machine main body 101. The document d placed on the document table of the automatic document feeder 201 is transported by a transport unit (not shown), and an image on one or both sides of the document is scanned and exposed by the optical system of the document image scanning exposure device 202. Incident light reflecting the image is read by the line image sensor CCD.

  The analog image signal photoelectrically converted by the line image sensor CCD is subjected to analog processing, A / D conversion, shading correction, image compression processing, and the like in an image processing unit (not shown) to become digital image information. The image information is sent to the image forming unit 80. The image forming unit 80 includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K each having an image carrier for each of Y, M, C, and K, an endless intermediate transfer belt 6, and a refeed mechanism. A sheet feeding / conveying means including (ADU mechanism) and a fixing device 17 for fixing the toner image are provided.

  In this example, the image forming unit 10Y includes a photosensitive drum 1Y, a charger 2Y, a writing unit 3Y, a developing unit 4Y, and an image forming body cleaning unit 8Y, and forms a yellow (Y) color image. It is made like. The photosensitive drum 1Y constitutes an example of an image carrier, and is provided, for example, so as to be rotatable in the vicinity of the upper right side of the intermediate transfer belt 6 so as to form a Y-color toner image. In this example, the photosensitive drum 1Y is rotated counterclockwise by a driving mechanism (not shown). A charger 2Y is provided on the lower right side of the photosensitive drum 1Y so as to charge the surface of the photosensitive drum 1Y to a predetermined potential.

  A writing unit 3Y having respective laser light sources and polygon mirrors is provided almost directly beside the photosensitive drum 1Y. The writing unit 3Y having each laser light source and a polygon mirror is provided for the pre-charged photosensitive drum 1Y. A laser beam for Y color having a predetermined intensity based on image data is scanned.

  The laser beam light is, for example, writing so-called Y color image data in the main scanning direction that is deflected and scanned by rotating a polygon mirror for Y color. The main scanning direction is a direction parallel to the rotation axis of the photosensitive drum 1Y. The photosensitive drum 1Y rotates in the sub-scanning direction. The sub-scanning direction is a direction orthogonal to the rotation axis of the photosensitive drum 1Y. The photosensitive drum 1Y rotates in the sub-scanning direction, and an electrostatic latent image for Y color is formed on the photosensitive drum 1Y by the deflection scanning of the laser beam light in the main scanning direction.

  The above-described laser beam is scanned onto the photosensitive drum 1Y with the reference period of the reference IDX signal as a control target. The scanning period of the laser beam light deflected by the polygon mirror 34 is detected by an index sensor 49 as shown in FIG. 2, and an index signal for Y color (hereinafter referred to as a Y-IDX signal) as an example of a scanning light detection signal. And output to the polygon drive control system. Here, the index signal refers to a signal for detecting that the mirror surface of the polygon mirror 34 is phase-adjusted at a predetermined angle by the index sensor 49 in each image forming unit. For example, in the polygon drive control system for Y color, polygon phase control is performed such that the Y-IDX signal maintains the target phase difference with respect to the reference-IDX signal (see FIGS. 2 and 3).

  A developing unit 4Y is provided above the writing unit 3Y, and operates to develop the electrostatic latent image for Y formed on the photosensitive drum 1Y. The developing unit 4Y has a Y-color developing roller (not shown). In the developing unit 4Y, a Y color toner agent and a carrier are stored.

  The Y-color developing roller has a magnet disposed therein, and rotates and conveys the two-component developer obtained by stirring the carrier and the Y-color toner agent in the developing unit 4Y to the opposite part of the photosensitive drum 1Y. The electrostatic latent image is developed by the color toner agent. The Y color toner image formed on the photosensitive drum 1Y is transferred to the intermediate transfer belt 6 by operating the primary transfer roller 7Y (primary transfer). A cleaning unit 8Y is provided below the left side of the photosensitive drum 1Y so as to remove (clean) the toner agent remaining on the photosensitive drum 1Y in the previous writing.

  In this example, an image forming unit 10M is provided below the image forming unit 10Y. The image forming unit 10M includes a photosensitive drum 1M, a charger 2M, a writing unit 3M, a developing unit 4M, and an image forming body cleaning unit 8M, and forms a magenta (M) color image. . An image forming unit 10C is provided below the image forming unit 10M. The image forming unit 10C includes a photosensitive drum 1C, a charger 2C, a writing unit 3C, a developing unit 4C, and a cleaning unit 8C for an image forming body, and forms a cyan (C) color image. .

  An image forming unit 10K is provided below the image forming unit 10C. The image forming unit 10K includes a photosensitive drum 1K, a charger 2K, a writing unit 3K, a developing unit 4K, and an image forming member cleaning unit 8K, and forms a black (BK) image. . An organic photoconductor (OPC) drum is used as the photoconductor drums 1Y, 1M, 1C, and 1K.

  Note that the functions of the members of the image forming units 10M to 10K can be applied by replacing Y with M, C, and K for the same reference numerals of the image forming unit 10Y, and thus description thereof is omitted. A primary transfer bias voltage having a polarity opposite to that of the toner agent to be used (positive polarity in this embodiment) is applied to the primary transfer rollers 7Y, 7M, 7C, and 7K.

  The intermediate transfer belt 6 constitutes an example of an image carrier, and forms a color toner image (color image) by polymerizing the toner images transferred by the primary transfer rollers 7Y, 7M, 7C, and 7K. For example, the color image formed on the intermediate transfer belt 6 is conveyed toward the secondary transfer roller 7A as the intermediate transfer belt 6 rotates clockwise. The secondary transfer roller 7A is positioned below the intermediate transfer belt 6 and is configured to collectively transfer the color toner image formed on the intermediate transfer belt 6 onto the paper P conveyed from the paper supply unit 20. (Secondary transfer).

  For example, the paper feeding unit 20 is provided below the writing unit 3K and includes paper feeding trays 20A, 20B, and 20C. The paper P stored in the paper feed trays 20A, 20B, and 20C is fed by the feed roller 21 and the paper feed roller 22A provided in the paper feed trays 20A, 20B, and 20C, respectively, and the transport rollers 22B, 22C, and 22D, The toner is conveyed to the secondary transfer roller 7A through the registration roller 23 and the like.

  A fixing device 17 is provided on the left side of the secondary transfer roller 7A to fix the paper P on which the color image has been transferred. The fixing device 17 includes a fixing roller, a pressure roller, and a heating (IH) heater. In the fixing process, the paper P is heated and pressed by passing the paper P between a fixing roller heated by a heater and a pressure roller. The fixed sheet P is nipped by the sheet discharge roller 24 and placed on the sheet discharge tray 25 outside the apparatus.

  In this example, a cleaning unit 8A is provided on the upper left side of the intermediate transfer belt 6 and operates to clean the toner agent remaining on the intermediate transfer belt 6 after transfer. The cleaning unit 8 </ b> A has a neutralization unit that neutralizes charges on the intermediate transfer belt 6 and a pad that removes toner remaining on the intermediate transfer belt 6. The intermediate transfer belt 6 after the belt surface is cleaned by the cleaning unit 8A and discharged by the discharging unit enters the next image forming cycle. As a result, a color image can be formed on the paper P.

  The copying machine main body 101 includes a control unit 15 that controls the image forming units 10Y, 10M, 10C, 10K and the like based on the color misregistration correction mode and the polygon phase control mode. Here, the color misregistration correction mode is a registration mark formed on the intermediate transfer belt 6 in order to superimpose toner images of each color of Y, M, C, and BK with good reproducibility. 12B or the like, and calculates the color misregistration amount of the other color resist mark with respect to the reference color resist mark, and feeds back to each Y, M, C color image forming unit so as to eliminate this color misregistration amount. An operation for correcting the writing timing of the light beam.

  The polygon phase control mode refers to each image formation obtained by detecting the laser beam light scanned by each polygon mirror 34 of each image forming unit 10Y, 10M, 10C, 10K for each image formation color at a predetermined position. This is an operation for adjusting the phase difference φx between the color index signal (hereinafter referred to as YMCK-IDX signal) and the reference-IDX signal to predetermined target phase differences φy, φm, φc, φk.

  FIG. 2 is a conceptual diagram illustrating a configuration example of the writing unit 3Y for Y color. The Y color writing unit 3Y shown in FIG. 2 includes a semiconductor laser light source 31, a collimator lens 32, an auxiliary lens 33, a polygon mirror 34, a polygon motor 35, an f (θ) lens 36, and a CY1 lens 37 for mirror surface imaging. And a drum surface imaging CY2 lens 38, a reflector 39, a polygon motor drive substrate 45, and an LD drive substrate 46.

  The semiconductor laser light source 31 is connected to a Y-color LD drive substrate 46. Write data Wy is supplied to the LD drive substrate 46 from an image processing unit (not shown). Write data Wy is PWM-modulated on the LD drive substrate 46, and a laser drive signal SLy having a predetermined pulse width after PWM modulation is output to the semiconductor laser light source 31. The semiconductor laser light source 31 generates laser beam light based on the Y color laser drive signal SLy. The laser beam light emitted from the semiconductor laser light source 31 is shaped into a predetermined beam light by the collimator lens 32, the auxiliary lens 33, and the CY1 lens 37.

  This laser beam light is deflected in the main scanning direction by the polygon mirror 34. For example, the polygon mirror 34 is driven by a polygon motor 35. A polygon driving board 45 is connected to the polygon motor 35, and a polygon driving clock signal for Y color (hereinafter referred to as YP-CLK signal) is supplied to the polygon driving board 45 from the controller 15 described above. The polygon drive board 45 is configured to rotate the polygon motor 35 at a predetermined rotation speed based on the YP-CLK signal.

  After the polygon phase control, the rotation control is locked so that the polygon motor 35 rotates at a constant speed. The laser beam light deflected by the polygon mirror 34 is imaged toward the photosensitive drum 1Y by the f (θ) lens 36 and the CY2 lens 38. By this operation, in the normal operation mode or the color misregistration correction mode, an electrostatic latent image of the original image or the registration mark CR for color misregistration correction is formed in the image area of the photosensitive drum 1Y.

  A reflecting plate 39 is provided at a predetermined fixed portion of the writing unit 3Y, and a laser index sensor 49 is attached at a position facing the reflecting plate 39. The laser index sensor 49 detects the laser beam light deflected by the polygon mirror 34 and outputs a Y-IDX signal to the phase difference detector 61 shown in FIG. Although not shown in FIG. 2, the M-IDX signal, the C-IDX signal, and the K-IDX signal are respectively output from the laser index sensors 49 of the writing units 3M, 3C, and 3K for other M, C, and K colors. It is output to the phase difference detector 61.

  FIG. 3 is a block diagram illustrating a configuration example of a control system of the color copying machine 100. The control system of the copying machine 100 shown in FIG. 3 includes a control unit 15, an operation unit 16, a display unit 18, a phase difference detection unit 61, a phase correction unit 62, a Y polygon drive unit 63, an M polygon drive unit 64, and a Y polygon drive. A unit 63, a K polygon drive unit 66, and a crystal oscillator 67 are included.

  The control unit 15 constitutes an example of control means, and includes, for example, a CPU (central processing unit) 51 for image data writing control, a CPU 52 for polygon drive control, and a memory unit 53. The CPU 51 is connected to an image processing & LD driving block 70 that includes an image processing unit (not shown) and an LD driving substrate 46 provided for each image forming color.

  In the image processing & LD driving block 70, image processing is performed based on the image processing control data D70 output from the CPU 51, and laser beam light is generated for each image forming color based on the writing data after the image processing. The laser beam light generated for each image forming color is deflected and scanned by the Y polygon driving unit 63, the M polygon driving unit 64, the Y polygon driving unit 63, and the K polygon driving unit 66, and the photosensitive drums 1Y, 1M, 1C, An exposure process is performed at 1K.

  A CPU 52 is connected to the CPU 51. The CPU 52 is connected to a phase difference detection unit 61, which compares the reference-IDX signal with the Y-IDX signal, the M-IDX signal, the C-IDX signal, the K-IDX signal, etc., and outputs the phase difference data Dφ. . For example, the phase difference detection unit 61 inputs a reference-IDX signal, a Y-IDX signal, an M-IDX signal, a C-IDX signal, and a K-IDX signal, and outputs between the reference-IDX signal and the Y-IDX signal. A phase difference is detected, and phase difference detection data Dφy for Y color is output.

  Similarly, the phase difference between the reference-IDX signal and the M-IDX signal is detected and phase difference detection data Dφm for M color is output, and the level between the reference-IDX signal and the C-IDX signal is output. The phase difference is detected and the C color phase difference detection data Dφc is output, the phase difference between the reference-IDX signal and the K-IDX signal is detected, and the K color phase difference detection data Dφk is output. The In the figure, the phase difference data Dφ is represented by Dφ = (Dφy, Dφm, Dφc, Dφk).

  The Y-IDX signal is obtained by detecting the laser beam light scanned by the polygon mirror 34 of the image forming unit 10Y at a predetermined position. The M-IDX signal is obtained by detecting the laser beam light scanned by the polygon mirror 34 of the image forming unit 10M at a predetermined position. The C-IDX signal is obtained by detecting the laser beam light scanned by the polygon mirror 34 of the image forming unit 10C at a predetermined position. The K-IDX signal is obtained by detecting the laser beam light scanned by the polygon mirror 34 of the image forming unit 10K at a predetermined position.

  In addition to the CPU 52, a phase correction unit 62 is connected to the phase difference detection unit 61. The CPU 52 compares the phase difference for each image forming color detected by the phase difference detecting unit 61 with the threshold for phase difference determination, interrupts the image forming process based on the comparison result, and sets the image forming color for each image forming color. Polygon phase control for adjusting the phase difference to a predetermined target phase difference is executed.

  For example, for each image forming color system, a lower limit threshold φmin (limit value) and an upper limit threshold φmax (limit value) for phase difference determination are set in one cycle of the reference-IDX signal. This setting is for determining whether or not the phase difference φx of the Y-IDX signal with respect to the reference-IDX signal is within a predetermined range.

  When the phase difference φx between the reference-IDX signal and the Y-IDX signal is less than the lower threshold φmin or the phase difference φx exceeds the upper threshold φmax, the CPU 52 creates an image when the phase difference φx exceeds the upper threshold φmax. After the processing is interrupted and the phase difference φx between the reference-IDX signal and the Y-IDX signal is adjusted to zero, the sub-scan correction amount (hereinafter referred to as phase shift amount) obtained by the color misregistration correction processing (color misregistration correction mode) Based on the data D1, the phase correction unit 62 is controlled so that the phase difference φx between the reference-IDX signal and the Y-IDX signal matches the predetermined target phase difference φy. The same processing is performed for other MCK image forming colors. In the figure, the phase shift amount data D1 is represented by D1 = (D1y, D1m, D1c, D1k).

  The phase correction unit 62 receives phase detection data Dφ = (Dφy, Dφm, Dφc, Dφk), phase shift amount data D1 = (D1y, D1m, D1c, D1k) and a phase control instruction command D2 for each color, A YP-CLK signal, an MP-CLK signal, a CP-CLK signal, and a KP-CLK signal are generated as polygon driving clock signals for each color.

  A Y polygon drive unit 63, an M polygon drive unit 64, a Y polygon drive unit 63, and a K polygon drive unit 66 are connected to the phase correction unit 62. The Y polygon drive unit 63 is supplied with the YP-CLK signal, the M polygon drive unit 64 is supplied with the MP-CLK signal, the C polygon drive unit 65 is supplied with the CP-CLK signal, and the K polygon The driving unit 66 is supplied with a KP-CLK signal.

  A crystal oscillator 67 is connected to the phase correction unit 62 to generate a reference clock signal (hereinafter referred to as a CLK signal) and output it to the above-described CPUs 51 and 52, the phase difference detection unit 61, and the like in addition to the phase correction unit 62. The Y polygon driving unit 63 includes the polygon motor driving substrate 45 and the polygon motor 35 shown in FIG. The polygon drive unit 63 is configured to rotate the polygon motor 35 at a predetermined rotation speed based on the YP-CLK signal. The other M polygon driving unit 64, Y polygon driving unit 63, and K polygon driving unit 66 are also configured in the same manner as the Y polygon driving unit 63, and their functions are also the same, and the description thereof is omitted.

  A memory unit 53 is connected to the CPUs 51 and 52. The memory unit 53 includes a ROM (Read Only Memory), a RAM (Information Write / Read Memory as needed), a hard disk and the like. In the memory unit 53, for example, a step of comparing the phase difference φx detected by the phase difference detection unit 61 with the lower threshold value φmin and the upper threshold value φmax for phase difference determination, and an image forming process based on the comparison result. A program describing a step of interrupting and a step of executing polygon phase control for adjusting the phase difference φx to predetermined target phase differences φy, φm, φc, φk is stored.

  The operation unit 16 is connected to the CPU 51, and the operation data D16 is input when the user designates image forming conditions such as selection of paper P and setting of a paper feed tray in the image forming mode. The operation is performed by the user. In addition to the operation unit 16, the display unit 18 is connected to the CPU 51. A liquid crystal display is used for the display unit 18, and the liquid crystal display is used in combination with a touch panel (not shown) constituting the operation unit 16.

  4A and 4B are waveform diagrams showing a variation example (No. 1) of the Y-IDX signal with respect to the reference-IDX signal.

  Tr shown in FIG. 4A is one reference period of the reference-IDX signal, and is a main scanning reference fixed value corresponding to one surface of the polygon mirror. φy is the target phase difference between the reference-IDX signal and the Y-IDX signal. In order to maintain the target phase difference φy, first, after adjusting the phase difference between the reference-IDX signal and the Y-IDX signal to 0 °, the phase shift amount obtained by the color misregistration correction process is set. Based on this, the target phase difference φy is set between the reference-IDX signal and the Y-IDX signal.

  Similarly, for other image forming colors, the target phase difference φm is set between the reference-IDX signal and the M-IDX signal, and the target phase difference φc is set between the reference-IDX signal and the C-IDX signal. Is set, and the target phase difference φk is set between the reference-IDX signal and the K-IDX signal.

  Ty shown in FIG. 4B is one detection cycle of the Y-IDX signal. The ideal relationship between the two is Tr = Ty. Actually, Tr <Ty, Tr> Ty, or the like may occur due to a change in the temperature of the polygon motor 35 or a change in the in-machine temperature. In the figure, an arrow between A and B indicates a range in which the Y-IDX signal varies with reference to the target phase difference φy. For example, even if Tr = Ty is maintained, this fluctuation range appears as a drift fluctuation in the Y-IDX signal due to a slight change in the rotational speed of the polygon mirror 34 accompanying the temperature change of the polygon motor 35. Arise. This phenomenon may occur due to Tr <Ty or Tr> Ty.

  5A and 5B are waveform diagrams showing a variation example (No. 2) of the Y-IDX signal with respect to the reference-IDX signal.

  According to the variation example of the Y-IDX signal shown in FIG. 5B, the phase of the Y-IDX signal II advances due to the temperature change of the polygon motor 35, etc., and jumps over the reference-IDX signal I shown in FIG. 5A. 4B, the phase difference φy ′ between the reference-IDX signal I and the Y-IDX signal III detected next to the Y-IDX signal II is moved to the point A of the fluctuation range shown in FIG. 4B. Is detected as a control target. For this reason, in the writing unit 3Y, the image writing position for one surface (one scanning line) is displaced by the polygon mirror 34 with respect to the reference-IDX signal I (sub-scanning displacement for one surface).

  As for the above-described jumping phenomenon with respect to the reference-IDX signal I, the phase advance is such that the rotational speed of the polygon motor 35 is faster than the reference rotational speed (reference speed), and the Y-IDX signal II advances from the reference-IDX signal I. In this case, and the case where the rotational speed is slower than the reference speed and the Y-IDX signal II is behind the reference-IDX signal IV, the phase lag is a target. In the copying machine 100, a function for preventing a jump phenomenon with respect to the reference-IDX signal I in advance is added.

  6A to 6D are operation time charts showing a phase control example (No. 1) such as a YP-CLK signal.

  In this example, an allowable range for phase difference determination is set within one reference period of the reference-IDX signal, the phase difference between the reference-IDX signal and the Y-IDX signal is constantly monitored, and the phase difference is allowed. When the upper limit and the lower limit of the range are exceeded, the image forming process is interrupted, polygon phase control is executed, and the phase difference φx at the time of phase detection is adjusted to the target phase difference φy.

  Φy shown in FIG. 6A is a target phase difference between the reference-IDX signal I and the Y-IDX signal II shown in FIG. 6B. In this example, the lower limit threshold φmim (limit value) is a value that is equal to or smaller than a predetermined amount with respect to the minimum adjustment amount of phase control, that is, the phase difference φy / 2 that makes the target phase difference φy shown in FIG. Is set. Further, the upper limit threshold φmax (limit value) is a value that is not more than a predetermined amount with respect to the maximum adjustment amount of phase control, that is, a phase difference (2π−φy / 2) in which the target phase difference φy is −1/2. It is set.

  In FIG. 6C, when the phase difference φx at the time of phase detection is set, the lower limit threshold value is φmim, and the upper limit threshold value is φmax, the allowable range of the phase difference is φmim ≦ φx ≦ φmax. In this example, the CPU 52 compares the Y color phase difference φx detected by the phase difference detector 61 with the phase difference determination thresholds φmim and φmax, and interrupts the Y color image forming process based on the comparison result. To do. In this example, when φx <φmin shown in FIG. 6D, the phase control (minimum adjustment amount) is shifted, and when φx> φmax, the phase control (maximum adjustment amount) is shifted.

  When the phase difference φx detected by the phase difference detector 61 does not deviate from the allowable range (φmin ≦ φx ′ ≦ φmax), the detection of the phase difference φx is continued. In the polygon phase control, the phase difference φx for Y color is adjusted to the target phase difference φy. The comparison determination process is similarly performed for other image forming colors, and polygon phase control is executed for each image forming color.

  7A to 7E are operation time charts showing a phase control example (No. 2) such as a YP-CLK signal.

  In this example, in phase control of the YP-CLK signal or the like, first, the phase difference between the reference-IDX signal and the Y-IDX signal shown in FIG. For this purpose, the phase difference is set to 0 ° by synchronizing the phase of the reference-IDX signal with the phase of the YP-CLK signal or the like. Thereby, the laser index sensor 49 for Y color detects a Y-IDX signal as shown in FIG. 7C that is substantially in phase with the YP-CLK signal (φx = 0).

  Next, the YP-CLK signal having the phase φ = 0 shown in FIG. 7C is shifted to the target phase difference φy as shown in FIG. 7E. The target phase difference φy is set between the reference-IDX signal and the Y-IDX signal based on the phase shift amount obtained by the color misregistration correction process.

  In this example, phase detection data Dφ = Dφy for Y color is output from the phase difference detection unit 51 to the phase correction unit 62, and phase shift amount data D1 = D1y for Y color and phase control are output from the CPU 52 to the phase correction unit 62. When the instruction command D2 is output, the phase correction unit 62 sets the target phase difference φy between the reference-IDX signal and the Y-IDX signal, so that the polygon drive clock signal for Y color as shown in FIG. YP'-CLK signal is generated. As a result, the laser index sensor 49 for Y color has a phase difference φx = φy with respect to the YP-CLK signal that is in phase with the reference-IDX signal (φx = 0) in FIG. 7A, as shown in FIG. 7E. A Y'-IDX signal is detected.

  Similarly, for the other image forming colors, the phase correction unit 62 sets a target phase difference φm between the reference-IDX signal and the M-IDX signal, and determines the difference between the reference-IDX signal and the C-IDX signal. A target phase difference φc is set between them, and MP-CLK signal, CP-CLK signal, and KP-CLK signal are generated to set the target phase difference φk between the reference-IDX signal and the K-IDX signal. .

  In this way, the image forming color before each phase of the Y-IDX signal, the M-IDX signal, the C-IDX signal, and the K-IDX signal jumps over the phase of the reference-IDX signal (φ = 0 ° or 360 °). The polygon phase control can be executed every time, and the image forming process can be resumed after the phase alignment of the YP-CLK signal, the MP-CLK signal, the CP-CLK signal, and the KP-CLK signal.

  Next, an operation example of the color copying machine 100 will be described. FIG. 8 is a flowchart showing an operation example of the CPU 51 for image processing control of the color copying machine 100 as the first embodiment, and FIG. 9 is a flowchart showing an operation example of the CPU 52 for polygon drive control.

  In this example, the CPU 51 of the color copying machine 100 is responsible for image processing control and the CPU 52 is responsible for polygon drive control, and the drift of the YMCK-IDX signal due to the speed fluctuation due to the temperature change of the polygon motor 35 is caused. In response to the phenomenon, the phase difference φx is always detected, and when the phase difference φx falls below a certain amount, the image operation is interrupted and the polygon phase control is executed. It is made to resume.

  With this as an operating condition, the CPU 51 waits for a request for an image forming job in step ST1 of the flowchart shown in FIG. At this time, the user operates the operation unit 16 to instruct the CPU 51 of image forming conditions such as selection of the paper P and setting of the paper feed tray. The CPU 51 sets an image forming job in the image processing & LD driving block 70, the CPU 52, and the like by the operation data D16 based on the image forming conditions.

  When there is a request for the above-described image forming job, the process proceeds to step ST2, and the CPU 51 executes image forming processing such as image writing related to the image forming job. The CPU 52 detects the phase difference φx of the YMCK-IDX signal with respect to the reference-IDX signal (see FIG. 9).

  In step ST3, the CPU 51 determines whether the image writing related to the image forming job is the last page. If the final page has not been reached, the process proceeds to step ST4, where it is determined whether or not an “interruption notice” for the image forming process has been received from the CPU 52. The interruption notification is confirmed by an interruption notification signal S52 transmitted from the CPU 52 to the CPU 51 when the phase difference φx deviates from the allowable range. If the interruption notification signal S52 has not been received, the process returns to step ST2 and the CPU 51 continues the image forming process.

  In step ST4, when the CPU 51 receives the interruption notification signal S52 from the CPU 52, the CPU 51 proceeds to step ST5 and determines whether or not the page currently forming an image has been finished. For example, the EOF (end of) flag of the image data Dy, Dm, Dc, Dk of the page is detected to confirm the end of image formation on the page. Of course, the present invention is not limited to this. The printing process of the page is interrupted halfway, the paper P processed halfway is discharged, and the image data Dy, Dm, Dc, Dk is saved in the memory unit 15. When restarting, the image forming process for the page may be started again from the beginning using the image data Dy, Dm, Dc, Dk.

  In this example, when all the image forming processes for the page have not been completed, the process proceeds to step ST6, where the image forming process for the page is executed to the end and terminated. At the same time, for example, the CPU 51 transmits a response signal S51 indicating the end of the page image formation to the CPU 52. Thereafter, the process proceeds to step ST7, where the CPU 51 determines whether or not there is a “resume notification” from the CPU 52. The restart notification is confirmed by a restart notification signal S53 output from the CPU 52 to the CPU 51.

  When the restart notification signal S53 is received, the process returns to step ST2, and the CPU 51 continues the image forming process for the next page related to the previously interrupted image forming job. If the last page is detected in step ST3, the process proceeds to step ST8 to determine the end of the image forming job. For example, when the CPU 51 detects the power-off information, the image forming control ends. If power-off information is not detected, the process returns to step ST1 to wait for a request for another image forming job.

  According to the operation example of the CPU 52 for polygon drive control described above, the phase difference φx of the YMCK-IDX signal with respect to the reference-IDX signal is detected in step ST11 of the flowchart shown in FIG. In step ST12, it is determined whether or not the phase difference φx has deviated from an allowable range (φmin ≦ φx ≦ φmax). In this example, as shown in FIG. 6C, the phase difference φx is compared with the lower limit threshold φmin, the phase difference φx is compared with the upper limit threshold φmax, and the phase difference φx falls below the lower limit threshold φmin (φx <φmin ), Or when the phase difference φx exceeds the upper limit threshold φmax (φx> φmax), and when the phase difference φx deviates from the allowable range (YES). If the phase difference φx does not deviate from the allowable range (φmin ≦ φx ≦ φmax) (NO), the process returns to step ST11 to detect the phase difference φx of the YMCK-IDX signal with respect to the reference-IDX signal.

  When the phase difference φx falls below the lower limit threshold φmin or exceeds the upper limit threshold φmax (φx> φmax), the process proceeds to step ST13, and the CPU 52 transmits an interruption notification signal S52 to the CPU 51. Thereafter, the CPU 52 receives the response signal S51 from the CPU 51 in step ST14. Thereafter, the process goes to step ST15 to execute polygon phase control. For example, according to the phase control of the YP-CLK signal, the phase difference φx for Y color is adjusted to the target phase difference φy as shown in FIGS. Other image forming colors are processed in the same manner, and polygon phase control is executed for each image forming color.

  Thereafter, in step ST16, the CPU 52 determines whether or not the polygon phase control for each image forming color has been completed. If the polygon phase control has not ended, the process returns to step ST15 to continue the polygon phase control. When the polygon phase control is completed, the process proceeds to step ST16, and the CPU 52 transmits a restart notification signal S53 to the CPU 51. After that, returning to step ST11, the CPU 52 continues the phase difference detection process.

  As described above, according to the copying machine 100 as the first embodiment, when the image forming job is executed, the CPU 52 detects the phase difference φx detected by the phase difference detection unit 61 and the phase difference determination. The lower limit threshold φmin is compared, and the phase difference φx is compared with the upper limit threshold φmax. Based on the comparison result, the image forming process is interrupted, and the polygon phase control is performed to adjust the phase difference φx to a predetermined target phase difference φy. Execute. In the above example, the CPU 52 adjusts the phase difference φx between the reference-IDX signal and the YMCK-IDX signal to zero, and then determines the reference-IDX signal based on the sub-scan correction amount obtained by the color misregistration correction processing. The phase difference φx with respect to the YMCK-IDX signal is adjusted to predetermined target phase differences φy, φm, φc, and φk.

  Therefore, before the phase shifts from the state in which the phase of the YMCK-IDX signal is delayed with respect to the reference-IDX signal to the state in which the phase advances, or before the phase shifts from the state to a state in which the phase is further delayed (before jumping over the phase). The reference-IDX signal and the YMCK-IDX signal can be adjusted (maintained) to predetermined target phase differences φy, φm, φc, and φk, and the image forming process can be resumed after the phase adjustment.

  Thereby, even when the YMCK-IDX signal drifts due to the temperature change of the polygon motor 35, the phase of the YMCK-IDX signal does not jump over the reference-IDX signal, and the polygon is The sub-scanning deviation for one surface of the mirror 34 can be prevented. Therefore, the image forming process for each color can be performed with high definition by the optimum image forming units 10Y, 10M, 10C, and 10K after the phase alignment.

  FIG. 10 is a flowchart showing an operation example of the CPU 51 of the color copying machine 200 as the second embodiment.

  In this embodiment, the image forming unit 80 shown in FIG. 1 rotates the polygon mirror 34 for each image forming color based on the reference-IDX signal, and the laser beam for each color is applied to the photosensitive drums 1Y, 1M, 1C. , 1K, and image forming processing of color misregistration correction toner images is performed on the photosensitive drums 1Y, 1M, 1C, and 1K.

  In the phase difference detector 61, YMCK-IDX obtained by detecting each laser beam light scanned by the polygon mirror 34 of each image forming color image forming unit 10Y, 10M, 10C, 10K at a predetermined position. The phase difference between the signal and the reference-IDX signal is detected. The CPU 52 compares the phase difference φx detected by the phase difference detector 61 with the lower limit threshold φmin for phase difference determination, compares the phase difference φx with the upper limit threshold φmax, and corrects color misregistration based on the comparison result. The toner image forming process is interrupted, and polygon phase control is performed to adjust the phase difference φx to predetermined target phase differences φy, φm, φc, φk in the same manner as in the first embodiment (color copying machine). 200).

  In this example, one cycle of the reference-IDX signal is divided into a plurality of unit adjustment amounts, for example, 0 to 10, and a lower limit adjustment range and an upper limit adjustment range for phase difference determination are set in the cycle, and the CPU 52 When the phase difference φx between the reference-IDX signal and the YMCK-IDX signal is less than half (0.5) of the minimum adjustment amount (= 1) of the lower limit adjustment range, or the phase difference φx is adjusted to the upper limit. When the maximum adjustment amount of the range (= 10−1 / 2) or more, that is, 9.5 or more, the color misregistration correction process is interrupted, and the phase difference between the reference-IDX signal and the YMCK-IDX signal is determined. The phase adjustment between the reference-IDX signal and the YMCK-IDX signal is performed by adjusting to zero.

  In this example, the CPU 51 of the color copying machine 200 is responsible for color misregistration correction control, and the CPU 52 is responsible for polygon drive control, and the YMCK-IDX signal is caused by speed fluctuations due to temperature changes of the polygon motor 35. Responding to the drift phenomenon, the phase difference φx is always detected, and when the phase difference φx falls below a certain amount, the image operation is interrupted and the polygon phase control is executed. Will be resumed.

  With this as an operating condition, in the color copying machine 200, the CPU 51 waits for an instruction for color misregistration correction processing in step ST31 of the flowchart shown in FIG. At this time, when the fixing temperature of the fixing device 17 changes and the temperature difference becomes, for example, Δ2 ° C., the CPU 51 turns off the main power supply when the image forming units 10Y, 10M, 10C, and 10K are stopped for a certain time. When is turned on, when a correction command (instruction) is compulsorily issued by the user, normal color misregistration correction processing (color registration correction processing and γ correction) is executed.

  If there is a command for the above-described color misregistration correction processing, the process proceeds to step ST32, and the CPU 51 executes image writing processing related to the color misregistration correction processing. The CPU 52 detects the phase difference φx of the YMCK-IDX signal related to the color misregistration correction process with respect to the reference-IDX signal (see FIG. 9).

  In step ST33, the CPU 51 determines whether or not the color misregistration correction process has been completed. If the color misregistration correction process has not been completed, the process proceeds to step ST34, where it is determined whether or not a “discontinuation notification” for the color misregistration correction process has been received from the CPU 52. The interruption notification is confirmed by an interruption notification signal S52 transmitted from the CPU 52 to the CPU 51 when the phase difference φx deviates from the allowable range. If the interruption notification signal S52 has not been received, the process returns to step ST32 and the CPU 51 continues the color misregistration correction process.

  If the CPU 51 receives the interruption notification signal S52 from the CPU 52 in step ST34, the color misregistration correction process is interrupted. Thereafter, the process proceeds to step ST35, in which the CPU 51 determines whether or not there is a “resume notification” from the CPU 52. The restart notification is confirmed by a restart notification signal S53 output from the CPU 52 to the CPU 51. When the restart notification signal S53 is received, the process returns to step ST32, and the CPU 51 continues to execute the color misregistration correction process interrupted earlier. If the final flag of the color misregistration correction process is detected in step ST33, the CPU 51 ends the color misregistration correction process.

  As described above, according to the color copying machine 200 according to the second embodiment, when performing the color misregistration correction process, the CPU 52 detects the position detected by the phase difference detection unit 61 in the same manner as in the first embodiment. The phase difference φx and the lower limit threshold φmin for phase difference determination are compared, and the phase difference φx and the upper limit threshold φmax are compared. Based on the comparison result, the color misregistration correction processing (registration mark image forming processing) is interrupted, Polygon phase control for adjusting the phase difference φx to a predetermined target phase difference φy is executed. In the above example as well, as in the first embodiment, the CPU 52 adjusts the phase difference φx between the reference-IDX signal and the YMCK-IDX signal to zero, and then performs sub-scanning obtained by color misregistration correction processing. Based on the correction amount, the phase difference φx between the reference-IDX signal and the YMCK-IDX signal is adjusted to predetermined target phase differences φy, φm, φc, φk.

  Therefore, before the phase shifts from the state in which the phase of the YMCK-IDX signal is delayed with respect to the reference-IDX signal to the state in which the phase advances, or before the phase shifts from the state to a state in which the phase is further delayed (before jumping over the phase). The predetermined target phase differences φy, φm, φc, and φk can be maintained between the reference-IDX signal and the YMCK-IDX signal.

  As a result, even when the YMCK-IDX signal drifts due to the temperature change of the polygon motor 35, the phase of the YMCK-IDX signal does not jump over the reference-IDX signal, and the color misregistration correction process is executed. The sub-scanning deviation for one surface of the polygon mirror 34 can be prevented. Therefore, the image forming process for each color can be performed with high definition by the optimum image forming units 10Y, 10M, 10C, and 10K after the phase alignment related to the color misregistration correction process.

  In the first and second embodiments described above, the case where the image processing control and the polygon drive control are divided and processed by the two CPUs 51 and 52 has been described. However, the present invention is not limited to this. A single CPU may be used. With this configuration, when the image forming process or the color misregistration correction process is performed, the phase of the YMCK-IDX signal deviates from the allowable range with respect to the reference-IDX signal, and the control unit 15 executes the polygon phase control. Communication processing such as the interruption notification signal S52 and the restart notification signal S53 transmitted from the CPU 52 to the CPU 51 and the response signal S51 transmitted from the CPU 51 to the CPU 52 can be omitted.

  The present invention is suitable for application to a tandem type color printer or color copier having a photosensitive drum and an intermediate transfer belt, and having a color misregistration correction mode and a polygon phase control mode, and a color complex machine thereof. is there.

1 is a conceptual diagram illustrating a configuration example of a color copying machine 100 as an embodiment according to the present invention. It is a conceptual diagram which shows the structural example of the writing unit 3Y for Y color. 2 is a block diagram illustrating a configuration example of a control system of the copying machine 100. FIG. (A) And (B) is a wave form diagram which shows the example (the 1) of a fluctuation | variation of the Y-IDX signal with respect to a reference- IDX signal. (A) And (B) is a wave form diagram which shows the example of a fluctuation | variation of the Y-IDX signal with respect to a reference | standard-IDX signal (the 2). (A)-(D) are operation | movement time charts which show the phase control examples (the 1), such as a YP-CLK signal. (A)-(E) are the operation | movement time charts which show the phase control examples (the 2), such as a YP-CLK signal. 3 is a flowchart showing an operation example of a CPU 51 for image processing control of the color copying machine 100. It is a flowchart which shows the operation example of CPU52 for the polygon drive control. 6 is a flowchart showing an operation example of a CPU 51 of a color copying machine 200 as a second embodiment.

Explanation of symbols

1Y, 1M, 1C, 1K Photosensitive drum (image carrier)
3Y, 3M, 3C, 3K Writing unit 4Y, 4M, 4C, 4K Development unit 6 Intermediate transfer belt (image carrier)
10Y, 10M, 10C, 10K Image forming unit (image forming means)
12A, 12B Registration sensor 15 Control unit (control means)
16 Operation unit
18 Display 51,52 CPU
61 Phase difference detector (detection means)
62 Phase Correction Unit 63 Y Polygon Drive Unit 64 M Polygon Drive Unit 65 C Polygon Drive Unit 66 K Polygon Drive Unit 70 Image Processing & LD Drive Block 80 Image Forming Unit 100, 200 Color Copier 101 Copier Main Body 102 Image Reading Device 201 Automatic Document feeder 202 Document image scanning exposure apparatus

Claims (4)

An image forming means for rotating the polygon mirror based on the image scanning reference signal, scanning the light with the polygon mirror, and performing image forming processing on the image carrier;
Detecting means for detecting a phase difference between a scanning light detection signal obtained by detecting light scanned by a polygon mirror of the image forming means at a predetermined position and the image forming scanning reference signal;
Based on the result of comparing the phase difference detected by the detection means with a threshold value for phase difference determination, the image forming process is interrupted, and phase control is performed to adjust the phase difference to a predetermined target phase difference. An image forming apparatus comprising: a control unit. A lower limit threshold and an upper limit threshold for determining whether or not a phase difference of the scanning light detection signal with respect to the image forming scanning reference signal exists within a predetermined phase difference range are set,
The control means includes
When the phase difference between the image scanning reference signal and the scanning light detection signal falls below the lower threshold, or when the phase difference exceeds the upper threshold, the imaging process is interrupted,
After adjusting the phase difference between the image scanning reference signal and the scanning light detection signal to zero, the image scanning reference signal and the scanning light detection signal are calculated based on the sub-scan correction amount obtained by the color misregistration correction processing. The image forming apparatus according to claim 1, wherein a phase difference between the two is adjusted to a predetermined target phase difference. An image forming means for rotating the polygon mirror based on the image scanning reference signal, scanning the light with the polygon mirror, and performing image forming processing for color misregistration correction on the image carrier;
Detecting means for detecting a phase difference between a scanning light detection signal obtained by detecting light scanned by a polygon mirror of the image forming means at a predetermined position and the image forming scanning reference signal;
Based on the result of comparing the phase difference detected by the detection means with a threshold value for phase difference determination, the color misregistration correction process is interrupted, and phase control is performed to adjust the phase difference to a predetermined target phase difference. And an image forming apparatus. One cycle of the image scanning reference signal is divided into a plurality of unit adjustment amounts, and a lower limit adjustment range and an upper limit adjustment range for phase difference determination are set in the cycle,
The control means includes
When the phase difference between the image scanning reference signal and the scanning light detection signal is less than half of the unit adjustment amount of the lower limit adjustment range, or the phase difference is half of the unit adjustment amount of the upper limit adjustment range When this is the case, the color misregistration correction process is interrupted,
4. The phase alignment between the image forming scanning reference signal and the scanning light detection signal is executed by adjusting a phase difference between the image forming scanning reference signal and the scanning light detection signal to zero. Image forming apparatus.

Images