Abstract: An image forming apparatus includes a light emission source, a polygon mirror, a plurality of image carrying members, an optical detection mechanism, and an instruction mechanism. The light emission source outputs a plurality of optical beams in accordance with image data. The polygon mirror receives the optical beams at different mirror points, and deflects the beams into a first plurality of scanning optical beams in given directions to scan on predetermined scanning lines in a main scanning direction. The plurality of image carrying members rotating in a sub-scanning direction receive the first plurality of scanning optical beams to form primary separate color images. The optical detection mechanism detects a second plurality of scanning optical beams included in the first plurality of scanning optical beams. The instruction mechanism instructs the light emission source to light on and off at timings based on a plurality of detection signals from the optical detection mechanism.

Abstract: A lateral position of a photoreceptor belt is detected by at least a first sensor and a second sensor, respectively located near a first imager and a second imager. The detected lateral positions of the photoreceptor belt by the first sensor is compared to the detected lateral position of the photoreceptor belt by the second sensor. Based on this compared difference, a correction is applied to the position of the second imager relative to the photoreceptor belt. To apply the correction, the location of the start of scan (SOS) of the respective imagers is moved.

Abstract: A timing detection circuit including a first timing detection circuit, a second detection circuit, and an output circuit is disclosed. The first detection circuit detects, among multiphase clocks having n mutually different phases and a frequency of k times the frequency of a reference clock, a closest clock having a clock edge closest to a valid edge of the synchronizing signal and generates first detect signal DET_A indicating the detected clock. The second timing detection circuit detects within which of k successive cycles of the representative clock selected from the multiphase clocks the valid edge of the synchronizing signal is positioned and generates second detect signal DET_B indicating the detected cycle. The output circuit receives the first detect signal and the second detect signal and outputs first output signal OUT_A and second output signal OUT_B.

Abstract: A disclosed device for generating a pulse-width modulated signal according to image data and based on a pixel clock signal includes a pixel clock generating unit configured to generate the pixel clock signal and a modulated data generating unit configured to generate the pulse-width modulated signal. The pixel clock generating unit includes a multi-phase clock signal generating unit, a comparing unit, a frequency calculation unit, a counting unit, and a pixel clock signal output unit. The modulated data generating unit includes a data converting unit, an edge time calculation unit, and a pulse-width modulated signal output unit.

Abstract: In an image forming apparatus that outputs a reference clock, divides the outputted reference clock based on a set multiple, and generates an image clock based on the division, a width of a synchronization signal that indicates dynamic deviation characteristics is detected, and the multiple is set in accordance with the detected width of the synchronization signal.

Abstract: An image forming apparatus which has a plurality of image forming stations arranged in parallel, each of the image forming stations having a photosensitive drum, and which forms a desired image by combining toner images formed on the photosensitive drums. A laser scanning optical system deflects and scans a plurality of laser beams concurrently with a single polygon mirror to irradiate the photosensitive drums. In a monochromatic mode, the rotation speed of the photosensitive drum for forming a black image is changed higher, and synchronization of writing in a main scanning direction is performed by using one of the laser beams irradiating the other photosensitive drums of which rotation speeds are not changed.

Abstract: An optical scanning device includes a synchronism detecting element for detecting a light beam scanningly deflected by a deflecting surface of an optical deflector, to determine an image-writing start position of the light beam on a scan surface in a main-scan direction, and a synchronism detecting optical element for directing the light beam scanningly deflected by the optical deflector to the synchronism detecting element, wherein the synchronism detecting optical element is comprised of a prism having a plurality of reflecting surfaces being unified and having a power in a sub-scan direction, and wherein, in a sub-scan section, the prism is configured to place the deflecting surface of the optical deflector and a light-receiving surface of the synchronism detecting element in an optically conjugate relationship with each other.

Abstract: An optical scanner device, comprising a scanning unit, which casts irradiation light emitted from a light source in an arbitrary direction to scan an observation object, an objective lens system, which converges the irradiation light on the observation object, and a photo-detector unit, which is disposed on an optical axis of the objective lens system to have the irradiation light transmit therethrough, is provided. A position of the irradiation light converged on the observation object is detected based on a position of a light spot of the irradiation light transmitting through the photo-detector unit.

Abstract: As a scanning light beam which is scanning and traveling away from an effective image region moves passed the location of a sensor, a horizontal synchronizing signal Hsync is obtained as a first detection signal. A deflection mirror surface turns around, thereby reversing the direction in which the scanning light beam scans. This scanning light beam therefore scans an effective image region IR, and a latent image forming operation using this scanning light beam is controlled based on the horizontal synchronizing signal Hsync. Hence, there is a relatively long period of time (T4+T5) since the horizontal synchronizing signal Hsync is obtained until formation of a latent image starts in accordance with the signal Hsync. This secures sufficient time for control of the latent image forming operation based on the horizontal synchronizing signal Hsync, and hence, realizes the latent image forming operation as desired during the time T6.

Abstract: A deflecting unit deflects a light beam emitted by each of a plurality of light-beam emitting units independently to scan surfaces of different bodies to be scanned. Each of a plurality of light-receiving units receives the deflected light beam at a predetermined position in a direction of the deflection. An incident angle of the deflected light beam with respect to a scanning line extending in a direction of scanning on a light-receiving surface of the light-receiving unit is set to be identical for all of the light-receiving units.

Abstract: An image forming apparatus includes a light source that emits a light beam in a main scanning direction according to image data to be used for image formation, a control unit that controls the light source, and detectors that detect the light beam. The main scanning direction is divided into areas and a cycle of a pixel clock is corrected in each area independently based on detection results of the detectors so as to correct an image position and image magnification.

Abstract: A beam detecting unit detects at least one of a position of an optical beam in a sub scanning direction and a position of the optical beam in a main scanning direction. A color-misalignment correcting unit changes an optical-beam irradiating position on a photosensitive element based on a result of detection by the beam detecting unit. The beam detecting unit is arranged between an optical element that is closest to a corresponding photosensitive element and the corresponding photosensitive element.

Abstract: A method for forming a pixel (20) having a predetermined density onto a sensitized recording medium moving in a length direction energizes a pixel exposure source (14) to begin exposure at the leading edge (34) of a pixel (20) and for a first predetermined time interval. The pixel exposure source (14) is de-energized for a period depending on the predetermined density and on media transport speed, then re-energized at the termination of the period. The pixel exposure source (14) is then de-energized at the end of a second predetermined time interval to terminate exposure at the trailing edge (36) of the pixel (20), whereby spatial dimensions of each pixel (20) are maintained at variable transport speed or density of pixel (20).

Abstract: A method for imaging a printing form is particularly suited for a printing form exposer or a printing unit of a press. A plurality of light sources produce image points in a row on the printing form whose spacing is greater than the minimum image point spacing. A first partial row of image points is produced with a first subset of the light sources and a second partial row is produced with a second subset. During a number of imaging steps, at least some of the image points of in each case one of the subsets is placed along the row in positions between image points of the respective partial row, produced in a previous imaging step, and in which, after the number of imaging steps, in a further imaging step, image points of the first subset are placed along the row at positions between image points of the second partial row from the preceding imaging step.

Abstract: A device and method for controlling timing for starting image formation, and image forming apparatus using such device and method are described. A detector outputs a synchronization detection signal when a light beam enters the detector. The timing for starting image formation is determined based on timing when a counter value, which is counted from timing when the synchronization detection signal is detected, reaches a reference counter value. The reference counter value may be determined according to an operation mode.

Abstract: The positioning of image data written along a laser beam scan path in the scan direction, e.g., the margin and/or line length is adjusted in a manner that compensates for changes in the laser beam scan path as a result of one or more operating conditions, such as changes in temperature. Further, the positioning of image data in the process direction may be adjusted in a manner that compensates for changes in the laser beam scan path as a result of the one or more operating conditions.

Abstract: A light-emission control unit controls an emission of a light beam from a light-beam generating unit based on an input image signal. A light-beam scanning unit deflects the light beam in a main scanning direction and irradiates the deflected light beam on an image carrier. An anomalous-light emission detecting unit detects an anomalous light emission of the light-beam generating unit when there is no image signal input to the light-emission control unit. A control unit performs an error processing based on the detected anomalous light emission.

Abstract: An image forming apparatus includes an optical scanning device that scans a scan area on an image carrier with light flux containing image information and writes the image information onto an image area in the scan area. In the optical scanning device, a first light receiving unit receives light flux emitted from a light source and reflected by a reflecting optical unit; a second light receiving unit receives light flux that passes through an aperture of the reflecting optical unit, is deflected by a deflecting unit, and heads for outside the image area within the scan area; and a control unit controls a drive signal of the light source based on signals output from the first and second light receiving units.

Abstract: A light scanning device capable of scanning a light beam on a photosensitive surface includes a light receiving system configured to receive the light beam and output a light receiving signal and a synchronizing signal generating system configured to generate a synchronizing signal with which light scanning is synchronized. The synchronizing signal generating system includes a first bias superimposing system configured to superimpose a first bias signal onto the light receiving signals to generate a first light receiving signal, a second bias superimposing system configured to superimpose a second bias signal with a different level from that of the first bias signal onto the light receiving signals to generate a second light receiving signal, a waveform shaping system configured to shape the waveform of the second light receiving signal, and a comparing system configured to compare the first light receiving signal with the second light receiving signal to output the synchronizing signal.

Abstract: A scanning time is divided by the number of sides of a polygon mirror to obtain a value N. Then, it is determined whether an error has occurred. When no error has occurred, the value N is stored in an NVRAM, and a magnification correction value is calculated. Values M and N of a PLL are set based on the correction value. A difference between a clock set by the PLL and an ideal pixel clock frequency is corrected to an optimal magnification by changing a phase. The ideal pixel clock frequency after magnification correction is calculated from V=N0/N×F. The values M and N of the PLL that provide a frequency closest to the ideal frequency V are acquired. A difference between a frequency V? acquired from the values M and N and the ideal pixel clock frequency V is corrected by the clock phase.

Abstract: This invention makes it possible to prevent any uneven density and degradation in resolution in reciprocal laser scanning using a movable mirror. An image forming apparatus forms an image on a photosensitive member by scanning the photosensitive member with a laser beam reflected by a movable mirror with reciprocating the movable mirror whose rotation angle is changeable in accordance with an electrical signal. The apparatus detects the rotation direction of the movable mirror, and weights, on the basis of the rotation direction, image data of two lines along the sub-scanning direction in correspondence with the ratio of the scanning length after the start of laser write for a line of laser scanning to compensate the image to be formed using the movable mirror.

Abstract: An image forming apparatus using a synchronization signal generator can easily generate a pixel clock that enables both a magnification correction in a main scanning direction and a correction of expansion and contraction of pixel width in the main scanning direction. Each of pixel clock generation units generates a clock signal by dividing a frequency of a high-frequency clock so as to generate pulses of a reference period, a long period longer than the reference period and a short period shorter than the reference period, and outputs, as the pixel clock, one of the pulses that is designated by an output selection signal. A pixel clock correction data synthesizing unit synthesizes a first selection signal, which is generated base on a time-series distribution of the pulses of each period defined by a first set of data, and a second selection signal, which is based on a time-series distribution of the pulses of each period defined by a second set of data, so as to generate the output selection signal.

Abstract: A color image forming apparatus in which an engine controller outputs an operation start signal to write controllers at a timing at which a registration sensor detects a position of a sheet of transfer paper. Synchronization detection signals for colors are used to set reference positions for front edges of the colors in a main scanning direction. A write controller for a reference color outputs a write-operation start signal so as not to cut the synchronization detection signals each indicating one line for one color in the main scanning direction and line synchronization signals, into two parts in their longitudinal direction. The write-operation start signal is used to set a reference time point when the write controllers make transfer requests for image signals for the colors to an image processor.

Abstract: An image forming apparatus capable of properly performing an initialization of a control circuit including a laser diode driver circuit, includes a light source, a photoreceptor, a deflector, and a controller. The photoreceptor is built in the light source to detect incident light. The deflector deflects the laser light into a scanning laser beam. The controller controls the light source to light on and off, and obtains a laser light emission amount of the light source relative to a current flowing through the light source based on a detection of incident light by the photoreceptor. The controller determines the laser light emission amount of the light source during a time period when a path of the laser light from the light source is headed to a reflection surface of the deflector at an incident angle of approximately ninety degrees.

Abstract: An image forming apparatus includes an intermediate transfer member, a sensor, and two image forming units. Each of the image forming units includes an image carrier, an image writer, two development rollers, and a switcher. The image writer writes an electrostatic latent image on the image carrier. Each of the development rollers selectively driven by the switcher visualizes the electrostatic latent image to form toner images in four colors. The toner images are transferred and superimposed onto the intermediate transfer member to form a color toner image. The color toner image is transferred onto a transfer sheet. One or more marks are formed on the intermediate transfer member. The sensor detects one of the marks. The image writer starts writing in synchronism with a sync clock signal of the image writer output immediately after the sensor detects the mark or output after a predetermined time period elapses after the sensor detects the mark.

Abstract: A method of diagnosing a state of a horizontal synchronizing signal is provided for an optical scanner, which includes a rotary polygon mirror having a rotation sensor, a control clock competing with a signal of the rotation sensor to control the rotary polygon mirror to a constant speed, a laser beam illuminating the rotary polygon mirror to be used in a scanning operation, and a scanning beam detector detecting the laser scanning beam at a prescribed position and outputting a horizontal synchronizing signal to trigger a control of the scanner. The method includes using the optical scanner, and presetting an effective period of outputting the horizontal synchronizing signal by counting the control clock for the rotary polygon mirror, the counting being triggered by a previous horizontal synchronizing signal.

Abstract: A magnification correction controller corrects magnification in a main scanning direction by changing a timing of an image signal based on a time difference between a first detection time in a predetermined position along a main scanning line of the image carrier to which the laser beam is irradiated and a second detection time in a position different from the predetermined position along the main scanning line. The magnification correction controller corrects the magnification in the main scanning direction by changing a timing of the image signal corresponding to a color different from a predetermined color, based on the time difference measured for the predetermined color.

Abstract: An optical scanner device, comprising a scanning unit, which casts irradiation light emitted from a light source in an arbitrary direction to scan an observation object, an objective lens system, which converges the irradiation light on the observation object, and a photo-detector unit, which is disposed on an optical axis of the objective lens system to have the irradiation light transmit therethrough, is provided. A position of the irradiation light converged on the observation object is detected based on a position of a light spot of the irradiation light transmitting through the photo-detector unit.

Abstract: A frequency modulation apparatus capable of reducing a peak level of a radiation noise of a characteristic frequency band due to an image clock. This frequency modulation apparatus is used in an image formation apparatus having an image bearing body to be scanned by a laser beam. An auxiliary clock calculating portion calculates an auxiliary clock period based on a reference clock period and a modulation coefficient, and an image clock generating portion generates the image clock in which a frequency is different at least in one portion and other portions of an image area on a main scan line to be scanned by the laser beam on the image bearing body based on the initial period value set in advance and the auxiliary clock period, and the image clock generating portion performs a frequency modulation so that the frequency of the image clock changes within a predetermined fluctuation.

Abstract: An optical scanning device that includes: a light-emitting unit that emits laser light to a polygon mirror on the basis of a turning-on signal; a sensor unit that detects laser light reflected by the polygon mirror and outputs a sensor signal; and a noise removing unit that outputs a laser light detection signal when the sensor signal is output during an output period of the turning-on signal.

Abstract: The present invention discloses a clock signal generation circuit for generating one or more clock signals for performing a scanning operation by scanning a light beam from a light source to a scan target. The clock signal generation circuit includes a determination circuit for determining authenticity of start information in accordance with at least one of the length of the start information and the timing at which the start information is input, and a generation circuit for generating the clock signals in synchronization with the start information when the determination circuit determines that the start information is authentic.

Abstract: Provided are an optical scanning device and a method for detecting a synchronization signal. In the optical scanning device, a beam incident on a scanning area of an object's surface to be scanned and a beam incident on a synchronization signal detector are emitted by a light source but deflected from different deflecting surfaces of a beam deflector.

Abstract: As a scanning light beam which is scanning and traveling away from an effective image region moves passed the location of a sensor, a horizontal synchronizing signal Hsync is obtained as a first detection signal. A deflection mirror surface turns around, thereby reversing the direction in which the scanning light beam scans. This scanning light beam therefore scans an effective image region IR, and a latent image forming operation using this scanning light beam is controlled based on the horizontal synchronizing signal Hsync. Hence, there is a relatively long period of time (T4+T5) since the horizontal synchronizing signal Hsync is obtained until formation of a latent image starts in accordance with the signal Hsync. This secures sufficient time for control of the latent image forming operation based on the horizontal synchronizing signal Hsync, and hence, realizes the latent image forming operation as desired during the time T6.

Abstract: An image forming apparatus which has a plurality of image forming stations arranged in parallel, each of the image forming stations having a photosensitive drum, and which forms a desired image by combining toner images formed on the photosensitive drums. A laser scanning optical system deflects and scans a plurality of laser beams concurrently with a single polygon mirror to irradiate the photosensitive drums. In a monochromatic mode, the rotation speed of the photosensitive drum for forming a black image is changed higher, and synchronization of writing in a main scanning direction is performed by using one of the laser beams irradiating the other photosensitive drums of which rotation speeds are not changed.

Abstract: The laser beam output from each of the semiconductor lasers is applied to the same print dot, such as each of the print dots on a thermosensitive recording medium, in such a manner that the laser beams are superimposed on one another sequentially at the same time that each of the semiconductor lasers is moved in the main scanning direction.

Abstract: A measuring unit measures a time difference between detections of the optical beams by an optical beam detector arranged on either side of an image carrier with respect to a horizontal scanning direction. A magnification correcting unit determines whether a beam spot position adjustment amount corresponding to each of a plurality of developing colors preset by the sub position correcting unit exceeds a threshold preset for each of the plurality of developing colors, and depending on the result of the determination, performs magnification correction of the image by changing a beam spot position interval on a scanning line in units of a line or lines, or by changing a beam spot position interval on a scanning line in units of pixel.

Abstract: A beam light scanning device includes an image data processing unit operable to output image-processed data of neighboring pixels in such a way that the data is divided for distribution into first pixel data and second pixel data. The scanner also includes a synchronizer circuit that receives the first and second pixel data as output from the image data processor and outputs these pixel data while letting them be synchronized with clocks as synchronized based on a horizontal synchronous signal. The scanner further includes a couple of pulse width modulators or “PWMs”, a synthetic circuit, and a laser diode module. The PWMs are for adjustment of the pulse widths of the first and second pixel data as output from the synchronizer circuit respectively. The synthetic circuit combines together the pulse width-adjusted first and second pixel data. The LD emits a light beam indicative of the resultant combined pixel data.

Abstract: A technique for achieving a smart start of scan (SOS) detector that is related with line scan timing on raster output scanners by expanding the available functions to include beam size and position. A start of scan detection system adapted to provide beam size and position control. The system includes a CPU, a data source and laser driver managed by the CPU, and a multiple element pre-patterned detector managed by the CPU and enabling a sensor pattern through which laser beams from the laser driver are passed and detected. According to a method for managing beam size and position in a image processing system, a multiple element pre-patterned detector adapted to enable a sensor pattern is provided wherein at least one laser beam is passed through said sensor pattern enabled by the multiple element pre-patterned detector, analyzed and used by the image processing system to adjust beam size and position.

Abstract: A frequency modulation apparatus capable of reducing a peak level of a radiation noise of a characteristic frequency band due to an image clock. This frequency modulation apparatus is used in an image formation apparatus having an image bearing body to be scanned by a laser beam. An auxiliary clock calculating portion calculates an auxiliary clock period based on a reference clock period and a modulation coefficient, and an image clock generating portion generates the image clock in which a frequency is different at least in one portion and other portions of an image area on a main scan line to be scanned by the laser beam on the image bearing body based on the initial period value set in advance and the auxiliary clock period, and the image clock generating portion performs a frequency modulation so that the frequency of the image clock changes within a predetermined fluctuation.

Abstract: A scanning optical apparatus includes a light source capable of being modulated, a deflecting element for deflecting and scanning a beam emitted from the light source, a scanning optical element for imaging the deflected beam into a spot shape on a scanned surface, and an optical element for synchronous detection for directing the deflected beam from the deflecting element to a sensor to take the timing of image writing beginning. The scanning optical apparatus further inclueds a scanning position detecting device for making the optical axis of the optical element for synchronous detection and the principal ray of the beam from the deflecting element for taking the timing of image writing beginning coincident with each other, and detecting the position of the beam at a point having at least one image height separate from the optical axis of the scanning optical element.

Abstract: An image processing apparatus which comprises a RAM acting as a shared memory for storing image data, and an image processing board, connected to the RAM through a PCI bus acting as a general-purpose bus, for performing raster conversion to the image data and performing a necessary image process to the converted data by using a line memory is provided. In this apparatus, in a case where the image processing board can not input or output the data from or to the PCI bus, it is controlled not to generate a sync signal used for a process in the image processing board, whereby a stable operation is possible in an image forming apparatus and an image processing method which include the image processing apparatus.

Abstract: A scanning unit of an image-forming device has a polygon mirror for deflecting a laser beam across the surface of a photosensitive member. A disc that rotates together with the polygon mirror is provided with a reference mark. When the reference mark passes a photointerrupter, the photointerrupter detects the rotating position of the polygon mirror. A counter measures the number of pulses in a reference clock from the moment the photointerrupter detects the reference mark until a sensor provided in a measuring device detects the laser beam deflected by the polygon mirror, and the value of the counter is stored in memory as timing data. When the scanning unit is subsequently mounted in an image-forming device, the count value stored in memory is used to control the exposure timing for irradiating the photosensitive member in the image-forming device with the laser beam.

Abstract: A printing apparatus with a plate-making mechanism with a data modification part for modifying width of an original image in a subscan direction by computation to obtain a modified image and a controller for recording an image with its length in a main scan direction modified by shifting a writing clock in image recording. This allows reduction in the amounts of computation as compared with a case where modification against extension of a paper in the main scan direction and subscan direction is performed only by computation and makes it easy to control modification as compared with a case where the modification in the main scan direction and subscan direction is performed only by shifting the writing clock and a moving clock for a writing head. Thus, it becomes possible to easily correct the influence of extension of paper in printing.

Abstract: A synchronous detector detects timing of scanning by an optical scanner in an image forming apparatus. The optical scanner has a light source that emits a light beam, a deflecting unit that deflects the light beam, a scanning optical element that focuses the light beam deflected by the deflecting unit onto a surface to be scanned. The synchronous detector includes a photoreceiver, and a synchronous optical element that focus the light beam deflected by the deflecting unit onto the photoreceiver. The synchronous optical element satisfies a relationship fm<fd, where fm is a composite focal length of the scanning optical element in a main scanning direction, and fd is a composite focal length of the synchronous optical element in the main scanning direction.

Abstract: A pixel position specifying method in an image forming device, the method measuring positions of exposure beams of the respective exposure heads and specifying pixel positions of junctures of the exposure heads, the method includes: using a beam position detecting mechanism to measure the positions of the exposure beams; detecting a first exposure beam position on an image receiving surface provided at the beam position detecting mechanism, by turning on a first connecting pixel near a juncture of a first exposure head; detecting a second exposure beam position on the image receiving surface, by turning on a second connecting pixel near a juncture of a second exposure head and moving the beam position detecting mechanism in the Y axis direction; and specifying connecting pixel positions from a moving amount of the beam position detecting mechanism in the Y axis direction and positions of exposure beams of the exposure heads.

Abstract: An image recording apparatus includes a scanning part for recording a plurality of unit images individually on a plurality of recording media, the plurality of unit images being to be superimposed on each other to form a single objective image. The scanning part causes the plurality of unit images to be in different positions. Defects appear in different positions of the plurality of unit images, and are prevented from coinciding with each other in the objective image.

Abstract: An image forming apparatus in which the intensity of a light beam used to form a latent image is switched in response to a change in resolution. A laser emits a light beam for forming a latent image on a photosensitive drum. A polygon mirror scans the emitted light beam. BD sensors detect the scanned beam. A timing controller selects the preferable timing from a storage device table according to the intensity of the light beam or the resolution when controlling the light emission timing of the lasers in response to a detection of timing of the detected light beam.

Abstract: In a pixel clock creation method and device, a high frequency clock is created. A scanning time needed to scan a predetermined scanning length is detected in accuracy of half a period of the high frequency clock to output a detection value indicating the detected scanning time. The detection value and a predetermined target value are compared to output a comparison result. A phase data is created based on the comparison result. A pixel clock whose phase is controlled based on both the high frequency clock and the phase data is created.

Abstract: A scanning line alignment compensation apparatus and method for a laser printer. The scanning line alignment compensation apparatus includes a laser scanning unit (LSU) having a first laser diode and a second laser diode and at least one sync signal detection sensor that generates a sync signal based on at least one of the first laser diode and the second laser diode based on selectively driving either of the first laser diode and the second laser diode, and generates at least one offset sync signal having first and second sensor detection periods based on the sync signal generated based on the at least one of the first laser diode and the second laser diode; a compensation unit compensating for first and second video data input in synchronization with a video clock based on the first and second sensor detection periods; and a laser diode control unit outputting control signals to control the first laser diode and the second laser diode based on the compensated first and second video data.

Abstract: An image forming apparatus which is capable of reducing a color misalignment in a color overlapping process, and a color misalignment due to variation of the circumferential length of an intermediate transfer member due to an environmental change over time during a successive copy operation. The image forming apparatus carries out image formation by primarily transferring an image electrophotographically formed on an image carrier onto the rotatably driven intermediate transfer member, and then secondarily transferring the images on the intermediate transfer member onto a recording medium. An image forming operation of primarily transferring the image onto the intermediate transfer member is controlled according to the length of the intermediate transfer member in a circumferentially moving direction thereof and a variation of a predetermined parameter relating to the intermediate transfer member.