JP2008122566A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent picture quality defect from occurring in a structure of magnification correction through corrective processing of an image data. <P>SOLUTION: The image forming apparatus detects a position of a toner image formed on an intermediate transcript belt, calculating the magnification of the image size relative to a reference image (S102), and performing magnification correction by the corrective processing of the image data (S104). Then, if a temperature change from the temperature during the preceding registration control operation is 3°C or above (S110), the registration control is performed again, with the magnification of the detected image size calculated(S114), with magnification correction performed (S116), and with the beam gap of a light beam from each light emitting element arithmetically processed (S118). Thereafter, if deviation of the beam gap is larger than 0.5 dot with respect to the eighth light beam through the second in the rear end, the delay time of the scanning start timing is changed for the light beam so that the scanning starts from the reference position (S120-S126). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that forms an image by scanning light beams from a plurality of light emitting elements on a surface to be scanned.

  Conventionally, a scanning mechanism that scans a light beam using a polygon mirror or the like has been widely used in image forming apparatuses such as laser printers. In this image forming apparatus, since the magnification of the main scanning of the light beam changes according to the temperature change in the apparatus, a change in the magnification of the main scanning is detected and light is generated so as not to cause an image defect (image quality defect). The main scanning of the beam is corrected.

  As a specific method for detecting a change in magnification, in a configuration in which scanning is performed with a plurality of beams, a magnification is determined based on a passing time interval between a preceding beam and a succeeding beam using a sensor for setting scanning start timing (hereinafter referred to as an SOS sensor). There is known an image forming apparatus that uses a method for calculating the substitute characteristics of the SOS sensor and a method for measuring and detecting a time interval from the SOS sensor through the EOS sensor (Patent Document 1). In this image forming apparatus, the scan start timing is corrected so as to suppress the deviation of the scan start timings of a plurality of beams according to the change in magnification.

As a correction method for a change in magnification, a method is known in which pixel insertion or thinning is performed on an image indicated by image data based on the change in magnification, and the magnification is corrected by image data correction processing.
JP 2002-122799 A

  However, in the configuration in which the above magnification correction is performed by image processing, even when the beam gap is fluctuating, the pixel size does not change due to the magnification correction. Along with the variation, there is a variation in the beam gap in the main scanning direction, and in particular, there is a problem that the beam gap of the subsequent light beam greatly varies and an image quality defect occurs.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of preventing the occurrence of image quality defects in a configuration in which magnification correction is performed by image data correction processing. To do.

  In order to achieve the above object, an image forming apparatus according to a first aspect of the present invention includes a light source in which a plurality of light emitting elements that emit light beams according to image data are arranged, and a plurality of light emitting elements on a surface to be scanned. A ratio or difference with respect to a reference value of the size of an image formed on the surface to be scanned by the light scanning unit that scans the light beam emitted from each of the light beams in the main scanning direction and the light beam scanned by the light scanning unit. Based on the calculation means for calculating, the ratio or difference calculated by the calculation means, the image correction means for correcting the image data so that the size of the image becomes the reference value, and the calculation means Based on the ratio or difference, the scanning start timing by the light beams from the plurality of light emitting elements is set so that each of the scanning start positions by the light beams from the plurality of light emitting elements becomes a reference position. It is configured to include a timing changing means for changing each of the grayed.

  According to the image forming apparatus of the first aspect of the invention, the light beam is emitted from the plurality of light emitting elements of the light source according to the image data, and is irradiated from each of the plurality of light emitting elements on the surface to be scanned by the optical scanning unit. The light beam is scanned in the main scanning direction, and the calculation means calculates the ratio or difference of the size of the image formed on the surface to be scanned by the light beam scanned by the light scanning means with respect to the reference value.

  Then, the image correction unit corrects the image data based on the ratio or difference calculated by the calculation unit so that the image size becomes the reference value, and the timing change unit calculates the ratio calculated by the calculation unit. Alternatively, based on the difference, each of the scanning start timings by the light beams from the plurality of light emitting elements is changed so that each of the scanning start positions by the light beams from the plurality of light emitting elements becomes the reference position.

  As described above, the image data is corrected so that the size of the image becomes the reference value, and the scanning start positions by the light beams from the plurality of light emitting elements are set as the reference positions. By changing each of the scanning start timings of the light beams, even if the magnification of the main scanning changes due to a temperature change, the image size and the scanning start position can be corrected. Thus, in the configuration in which the image size is corrected, it is possible to prevent image quality defects.

  The timing changing means according to the first invention is based on the ratio or difference calculated by the calculating means, from the scanning start timing by the specific light beam that starts scanning first to the scanning start timing of the light beam other than the specific light beam. Each of the scanning start timings by the light beams from the plurality of light emitting elements can be changed so as to be shifted from the scanning start timing of the specific light beam by the determined delay time.

  The image correction means according to the first aspect of the present invention is based on the ratio or difference calculated by the calculation means, by performing at least one of pixel addition and pixel deletion with respect to the image indicated by the image data. The image data can be corrected so that the value becomes the reference value. This makes it possible to correct the size of the image formed on the scanned surface by adding or deleting pixels.

  According to a second aspect of the present invention, there is provided an image forming apparatus comprising: a light source in which a plurality of light emitting elements that emit light beams according to image data are arranged; and a light beam emitted from each of the plurality of light emitting elements on a scanned surface. An optical scanning unit that scans in the main scanning direction; an arithmetic unit that calculates a ratio or difference of a size of an image formed on a scanned surface by a light beam scanned by the optical scanning unit with respect to a reference value; Based on the ratio or difference calculated by the means, the image correction means for correcting the image data so that the size of the image becomes the reference value, and the correction contents by the image correction means A timing change for changing each of the scanning start timings by the light beams from the plurality of light emitting elements so that each scanning start position by the light beams from the light emitting elements becomes a reference position. It is configured to include a means.

  According to the image forming apparatus of the second invention, a light beam is emitted from a plurality of light emitting elements of a light source according to image data, and is irradiated from each of the plurality of light emitting elements on a scanned surface by an optical scanning unit. The light beam is scanned in the main scanning direction, and the calculation means calculates the ratio or difference of the size of the image formed on the surface to be scanned by the light beam scanned by the light scanning means with respect to the reference value.

  Then, the image correction unit corrects the image data based on the ratio or difference calculated by the calculation unit so that the size of the image becomes the reference value, and the timing change unit corrects the correction content by the image correction unit. Based on the above, each of the scanning start timings by the light beams from the plurality of light emitting elements is changed so that each of the scanning start positions by the light beams from the plurality of light emitting elements becomes the reference position.

  As described above, the image data is corrected so that the size of the image becomes the reference value, and the scanning start positions by the light beams from the plurality of light emitting elements are set as the reference positions. By changing each of the scanning start timings of the light beam, even if the magnification of the main scanning of the light beam changes due to temperature change, the image size and the scanning start position can be corrected. In the configuration in which the size of the image is corrected by this correction processing, it is possible to prevent the occurrence of image quality defects.

  The timing changing means according to the second invention is based on the correction contents of the image correcting means, and delays from the scanning start timing by the specific light beam that starts scanning first to the scanning start timing of the light beams other than the specific light beam Each of the scanning start timings by the light beams from the plurality of light emitting elements can be changed so that the time is determined and the scanning delay timing of the specific light beam is shifted by the determined delay time.

  The image correction means according to the second invention is configured to reduce the size of the image by performing at least one of pixel addition and pixel deletion on the image indicated by the image data based on the magnification calculated by the calculation means. The image data is corrected so as to be the reference value, and the timing changing unit changes the scanning start timing by the light beams from the plurality of light emitting elements based on at least one of the added pixel number and the deleted pixel number. can do. Accordingly, the size of the image formed on the surface to be scanned can be corrected by adding or deleting pixels, and the scanning start timing can be changed according to the added or deleted pixels. Can do.

  The image forming apparatus further includes a transfer unit that transfers the image formed on the surface to be scanned to the intermediate transfer member for transferring the image to the recording medium, and the arithmetic unit is transferred to the intermediate transfer member. A sensor for detecting the position of the image is provided, the size of the image is calculated based on the position of the image detected by the sensor, and the ratio or difference of the calculated image size with respect to a reference value can be calculated. . Accordingly, the position of the image formed on the surface to be scanned can be detected using the sensor, and the ratio or difference of the image size with respect to the reference value can be calculated.

  In addition, the image forming apparatus further includes a temperature sensor that detects a temperature provided inside or outside the apparatus, and the timing changing unit is based on the temperature detected by the temperature sensor. The scanning start timing can be changed. As a result, when the temperature change becomes large and the scan start timing needs to be changed, the scan start timing can be changed, so that the occurrence of image quality defects can be efficiently prevented.

  As described above, according to the image forming apparatus of the present invention, the image data is corrected so that the size of the image becomes the reference value, and each of the scanning start positions by the light beams from the plurality of light emitting elements is determined. By changing each of the scanning start timings with the light beams from the plurality of light emitting elements so as to become the reference position, even if the magnification of the main scanning of the light beam changes due to environmental changes, the image size and scanning Since the start position can be corrected, it is possible to prevent the occurrence of an image quality defect in the configuration in which the image size is corrected by the image data correction process.

  Embodiments of the present invention will be described below with reference to the drawings. In the present embodiment, a case where the present invention is applied to a color image forming apparatus will be described.

  As shown in FIG. 1, a color image forming apparatus 10 according to an embodiment of the first invention is stretched around a plurality of winding rollers 12 and conveyed in the direction of arrow A by driving a motor (not shown). An endless belt-like intermediate transfer belt 14 is provided. Further, print units 44C, 44M, 44Y, and 44K corresponding to the respective colors of cyan (C), magenta (M), yellow (Y), and black (K) are sequentially tandem along the belt conveyance direction of the intermediate transfer belt 14. It is arranged. In the following description, unless otherwise distinguished, each print unit has the same configuration, and therefore the description corresponding to each color is omitted.

  Each print unit 44 has a photosensitive drum 16 rotatably supported on an apparatus main body frame (not shown), and around each photosensitive drum 16 in the drum rotation direction (the arrow direction in FIG. 1). A charger 20 for uniformly charging the photosensitive drum 16, a developing unit 22 for supplying toner to the electrostatic latent image formed on the peripheral surface of the photosensitive drum 16, and developing, and an intermediate transfer member The toner image formed on the peripheral surface of the photosensitive drum 16 is provided so as to contact the lower surface (back surface) of the belt 14 and sandwich the intermediate transfer belt 14 between the belt 14 and the photosensitive drum 16. A first transfer device 24 for transferring to the surface of the intermediate transfer belt 14, a cleaner (not shown) for removing toner remaining on the photosensitive drum 16 after transfer, and an erase lamp (not shown) are arranged in this order. ing. Further, the color image forming apparatus 10 is provided with an optical scanning device 30 that irradiates a light beam toward each photosensitive drum 16 based on desired image data while performing main scanning.

  That is, after the toner remaining on the photoconductive drum 16 is removed by the cleaner, the charge on the photoconductive drum 16 is discharged by the erase lamp for discharging, and after being charged by the charger 20, the light is scanned by the optical scanning device 30. The surface of the body drum 16 is irradiated with a light beam to form an electrostatic latent image. The electrostatic latent image formed by the optical scanning device 30 is developed by the developing device 22 to form a toner image, and the toner image is transferred to the intermediate transfer belt 14 by the first transfer device 24.

  Further, the toner images on the respective photosensitive drums 16 are transferred onto the intermediate transfer belt 14 by the first transfer units 24 in the order of cyan (C), magenta (M), yellow (Y), and black (K). The toner images are superimposed and transferred as a color toner image, and move as the intermediate transfer belt 14 is conveyed in the direction of arrow A.

  Further, a second transfer unit 26 including two rollers 26A and 26B facing each other is disposed on the downstream side in the transport direction of the intermediate transfer belt 14 with respect to the contact portion with the photosensitive drum 16. The color toner image formed on the intermediate transfer belt 14 is sent between the rollers 26A and 26B. A recording paper 90 taken out from a paper tray (not shown) is conveyed between the rollers 26A and 26B, and a color toner image formed on the intermediate transfer belt 14 is transferred by the second transfer unit 26. It is transferred to the recording paper 90.

  The recording paper 90 onto which the toner image has been transferred is conveyed to a fixing device 28 composed of a pressure roller 28A and a heating roller 28B and subjected to a fixing process. As a result, the toner image on the recording paper 90 is fixed, and a desired image is formed on the recording paper 90. The recording paper 90 on which the image is formed is discharged out of the apparatus.

  Further, the color image forming apparatus 10 is provided with a controller 60 for controlling each part in the apparatus, and the controller 60 stores a program for executing a beam gap correction processing routine to be described later. . The controller 60 controls the irradiation of the light beam in the optical scanning device 30 and also controls the scanning start timing of the light beam.

  A temperature sensor 62 for detecting the temperature in the apparatus is provided around the optical scanning device 30 in the color image forming apparatus 10, and a detection signal output from the temperature sensor 62 is input to the controller 60. . Further, on the downstream side of the print unit 44 of the intermediate transfer body belt 14, a MOB (Mark on Belt) sensor 64 composed of a CCD is provided as an image sensor used in the regicon operation. Using the MOB sensor 64, The position of the toner image transferred on the intermediate transfer belt 14 in the main scanning direction is detected.

  Next, the optical scanning device 30 according to the first embodiment will be described. As shown in FIG. 3, the optical scanning device 30 includes a laser array 40 including eight light emitting elements arranged at different positions in the main scanning direction.

  As shown in FIG. 2, a condensing lens 46 is disposed on the optical axis of a plurality of light beams emitted from the laser array 40, and the light beam that has passed through the condensing lens 46 is used as a scanning optical system. To the polygon mirror 42. The polygon mirror 42 rotates in the direction of arrow D in FIG. 2 at a high speed and at a constant speed by a driving force of a polygon motor (not shown).

  For this reason, a plurality of light beams sequentially enter the plurality of reflecting surfaces 42A of the polygon mirror 42, and the reflected light passes through the fθ lens 48 that corrects the scanning speed on the exposure surface, and onto the photosensitive drum 16. Scanned.

  The eight light emitting elements of the LD group are arranged so as to be inclined with a predetermined angle with respect to the main scanning direction. Also, as shown in FIG. 3, on the photosensitive drum 16, the scanning start position by the light beam is sequentially from the light emitting element at the end (first light emitting element) by a predetermined beam gap (78 dots in the example of FIG. 3). The controller 60 controls the scanning start timing by the light beam of each light emitting element of the laser array 40 so as to deviate from the scanning start timing by the light beam of the first light emitting element that starts scanning first. The delay time until the scanning start timing by the light beam is controlled to be shifted for each light emitting element. The delay time is set in the controller 60 for each light emitting element, and the controller 60 shifts the delay time from the scanning start timing of the head light beam based on the set delay time. Scanning with a light beam from the light emitting element is started. The delay time is set as a count value of the write clock by the light beam.

  Next, the operation of the color image forming apparatus 10 according to the present embodiment will be described. When the main power supply of the color image forming apparatus 10 is turned on, the beam gap correction processing routine shown in FIG.

  First, in step 100, each part in the apparatus executes a warm-up process, and in step 102, a registration control (hereinafter, registration control) operation is performed to form a toner image representing a patch image on the intermediate transfer belt 14. The size of the toner image formed on the intermediate transfer belt 14 in the main scanning direction is detected by the MOB sensor 64 disposed on the downstream side of the print unit 44, and the magnification of the detected image size with respect to the reference image is detected. To obtain magnification information indicating the magnification.

  In step 104, magnification correction is performed by image data correction processing based on the acquired magnification information. For example, as shown in FIG. 5, the main image of the image formed on the intermediate transfer belt 14 based on the image data for a predetermined image area (size becomes a reference value) due to temperature change. Since the size in the scanning direction widens (in the example of FIG. 5, the size in the main scanning direction of the image is widened by 0.2%), based on the acquired magnification information, the image data is Perform correction processing.

  In the image data correction processing, the acquired magnification information is compared with a reference magnification, and the magnification is corrected by performing at least one of addition and deletion of pixels in units of one dot within one main scan. For example, a pixel is added within one main scan, and subsequent pixels are shifted in the main scan direction in accordance with the addition of this pixel, thereby correcting the image to be enlarged. Alternatively, the pixel at the predetermined position is deleted, and the subsequent pixel is shifted in the direction opposite to the main scanning direction according to the deletion of the pixel, thereby correcting the image to be reduced.

  By the above image data correction processing, the magnification is corrected so that the size of the image formed on the intermediate transfer belt 14 in the main scanning direction is the size of the image area as the reference value based on the image data. Is done.

  In step 106, it is determined whether or not a start signal has been input, and the user operates an operation panel (not shown) to instruct image forming processing, or a print job can be issued via a network (not shown). When input, the image forming process is started in step 108, and in the next step 110, the detection signal from the temperature sensor 62 is fetched, and the temperature change from the temperature during the previous regicon operation is a predetermined temperature (for example, 3 If the temperature change is less than 3 degrees, the process proceeds to step 112, where print processing is performed based on the image data to be printed, and according to the image data to be printed. Then, each photosensitive drum 16 is irradiated with a light beam from the optical scanning device 30 to form an electrostatic latent image, developed to form a toner image, and a recording sheet via the intermediate transfer belt 14. 0 by transferring the toner image to print an image on a recording sheet 90, the process returns to step 106 determines whether the start signal by the instructions in the next image forming process are input.

  On the other hand, if it is determined in step 110 that the temperature change is 3 degrees or more, in step 114, the regicon operation is performed again to represent the patch image formed on the intermediate transfer belt 14 by the MOB sensor 64. Detects the position of the toner image, calculates the image size based on the detected position, calculates the magnification of the calculated image size with respect to the size of the reference image, and obtains magnification information indicating the magnification To do. In the next step 116, based on the acquired magnification information, pixel insertion or decimation is performed on the image indicated by the image data to be printed, magnification correction is performed, and intermediate transfer is performed based on the image data to be printed. The image data is corrected so that the size of the image formed on the body belt 14 in the main scanning direction becomes the reference value.

In step 118, a beam gap that is the difference between the scanning start position of the first light beam that starts scanning first and the scanning start position of the light beam from each of the other light emitting elements is calculated. As shown in FIG. 6, with respect to the beam gap of the n-th light beam, the deviation ΔLn from the reference beam gap A × n (for example, 78 dots × n) can be expressed by the following equation.
ΔLn = A × (n−1) × (x / 100)
Here, x is a magnification (%) to be calculated. Note that A is the interval between the reference positions of the scanning start of the light beams from the adjacent light emitting elements.

  Next, in step 120, it is determined whether or not the beam gap deviation ΔL8 of the light beam at the rear end that starts scanning last is larger than 0.5 dots. The process proceeds to step 112 without changing the delay time of the scan start timing of the beam (eighth light beam), but if larger than 0.5 dots, the beam gap of the rear end light beam is determined to be greater than 0.5 dots in step 122. The delay time D8 of the scanning start timing of the rear end light beam is changed so that the scanning is started from the reference position with the reference beam gap. For example, by dividing ΔL8 calculated in step 118 by a predetermined scanning speed, a delay time change amount c is calculated, and a value obtained by subtracting the change amount c from a predetermined reference delay time is obtained as follows: The delay time D8 of the scanning start timing of the rear end light beam is set in the controller 60.

  Next, similarly in step 124, it is determined whether or not the deviation Δ7 of the beam gap of the seventh light beam (light beam that starts scanning immediately before the rear end light beam) is greater than 0.5 dots. If it is 0.5 dots or less, the process proceeds to step 112 without changing the delay time of the scan start timing of the seventh light beam. If it is greater than 0.5 dots, the process proceeds to step 126 in step 126. The delay time D7 of the scanning start timing of the seventh light beam is changed so that the beam gap of the light beam becomes the reference beam gap and the seventh light beam starts scanning from the reference position.

  Similarly to the above, when the deviation ΔLn is greater than 0.5 dots, the delay time Dn of the light beam is changed based on the deviation ΔLn of the beam gap for the sixth light beam to the second light beam. The process proceeds to step 112.

  As described above, by executing the beam gap correction processing routine, the magnification correction is performed every time the temperature change becomes large, and the delay time of the scanning start timing of each light beam is changed, based on the image data. The image data is corrected so that the size of the formed image becomes the reference value, and each light beam from the scanning start timing of the head light beam is adjusted so that the scanning start position of the light beam becomes the reference position. The delay time of the scan start timing is corrected.

  The beam gap correction processing routine described above is executed for each LD group corresponding to each print unit 44, and for each print unit 44, the magnification of the toner image formed on the intermediate transfer body bell 14 is corrected. The delay time of the light beam scanning start timing is changed, and scanning of each light beam is started from the reference position.

  As described above, according to the color image forming apparatus according to the first embodiment, the pixels of the image indicated by the image data are inserted so that the size of the formed image in the main scanning direction becomes the reference value. Or, the image data is corrected by thinning out, and the delay time of the scanning start timing by the light beams from the plurality of light emitting elements is changed so that each of the scanning start positions by the light beams from the plurality of light emitting elements becomes the reference position. Thus, even if the magnification of the main scanning of the light beam changes due to temperature change, the size of the formed image and the scanning start position can be corrected. Therefore, the image size is corrected by the image data correction process. In the configuration for correcting the image quality, it is possible to prevent image quality defects.

  Further, by using the MOB sensor used in the regicon operation, the position of the image formed on the intermediate transfer belt can be detected, the size of the image can be calculated, and the ratio or difference with respect to the reference value can be calculated. Therefore, it is not necessary to provide a new sensor to detect the size of the image, and the magnification information is acquired with high accuracy in order to detect the position of the image from the toner image formed on the intermediate transfer belt. be able to.

  Further, since the change of the scan start timing is performed when the temperature change becomes large and the scan start timing needs to be changed, it is possible to efficiently prevent the occurrence of the image quality defect.

  In the above embodiment, the case where the magnification information is acquired and the image data correction processing is performed based on the magnification information has been described as an example. However, the present invention is not limited to this, and the detected image is not limited to this. Image data correction processing may be performed based on the difference between the size in the main scanning direction and the reference value. In this case, the positional deviation of the scanning start position of each light beam may be calculated based on the difference from the reference value, and the delay time may be changed based on the calculated positional deviation.

  Further, although the case where the position of the toner image formed on the intermediate transfer belt is detected by the MOB sensor and the magnification of the image is calculated has been described as an example, an SOS sensor and an EOS sensor are provided inside the scanning device, The scanning of the beam may be detected to calculate the magnification of the image.

  Moreover, although the case where the light laser that scans the photosensitive drum of each print unit is irradiated from a plurality of light emitting elements of one surface emitting laser array has been described as an example, a surface emitting laser array is provided for each photosensitive drum, You may make it irradiate an optical laser with respect to the corresponding photoreceptor drum from four surface emitting laser arrays, respectively.

  Further, in the magnification correction by the image data correction processing, the case of inserting or thinning pixels has been described as an example, but the present invention is not limited to this, and the image indicated by the image data is linearly expanded and contracted, You may make it perform magnification correction.

  Further, although the case where the temperature sensor is provided in the apparatus has been described as an example, a temperature sensor may be provided outside the apparatus, and the beam gap may be corrected based on the temperature outside the apparatus.

  Next, a color image forming apparatus according to the second embodiment of the present invention will be described. In addition, about the structure and operation | movement fundamentally the same as 1st Embodiment, the same code | symbol as 1st Embodiment is attached | subjected and the description is abbreviate | omitted.

  In the color image forming apparatus according to the second embodiment, the amount of change in the delay time of the scan start timing is not the shift in the scan start position calculated based on the magnification information, but the number of pixels inserted or thinned in the magnification correction The point of calculation based on is mainly different from the first embodiment.

  By comparing the main scanning width considering the number of pixels added or deleted in the magnification correction and the reference main scanning width, the delay time of the scanning start timing is calculated as follows.

  First, a magnification error is calculated based on a correction amount from the total number of pixels in one main scan. For example, when there is no magnification error and the total number of dots for one main scan is 28003, when the magnification is deviated from the initial value and the total number of pixels per line is 28007 dots, pixels for 56 dots. Therefore, a fluctuation of 0.2% has occurred for 28063 dots.

Then, ΔLn = A × (n−1) × (x / 100) shown in the first embodiment.
Based on the above, the delay time of the scanning start timing is calculated.

  The delay time calculated as described above is set as a delay time after change with respect to a predetermined reference delay time.

  Note that the configuration of the color image forming apparatus and the flow of processing of the beam gap correction processing routine are the same as those in the first embodiment, and thus description thereof is omitted.

  As described above, according to the color image forming apparatus according to the second embodiment, the delay time is changed based on the number of pixels added or deleted by the magnification correction, and the scan start timing is set. Therefore, the scanning start timing can be changed in accordance with the change in the magnification of the image due to the magnification correction, and the occurrence of image quality defects can be further prevented.

1 is a schematic diagram illustrating a configuration of a color image forming apparatus according to a first embodiment of the present invention. 1 is a schematic diagram illustrating a configuration of an optical scanning device according to a first embodiment of the present invention. It is an image figure which shows the scanning start position on the photoconductive drum by the light beam from a several light emitting element. 3 is a flowchart showing the contents of a beam gap correction processing routine of the color image forming apparatus according to the first embodiment of the present invention. FIG. 6 is an image diagram illustrating a case where the size of an image formed on an intermediate transfer belt is increased in the main scanning direction. It is an image figure which shows the shift | offset | difference of the beam gap of the light beam from a several light emitting element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Color image forming apparatus 14 Intermediate transfer body belt 16 Photosensitive drum 22 Developing device 24 First transfer device 26 Second transfer device 30 Optical scanning device 40 Laser array 42 Polygon mirror 44 Print unit 60 Controller 62 Temperature sensor 64 MOB sensor 90 Recording sheet

Claims (7)

A light source in which a plurality of light emitting elements that irradiate a light beam according to image data are arranged;
An optical scanning unit configured to scan a light beam emitted from each of the plurality of light emitting elements in a main scanning direction on a scanned surface;
A computing means for computing a ratio or difference of a size of an image formed on a scanned surface by a light beam scanned by the light scanning means with respect to a reference value;
Image correcting means for correcting the image data so that the size of the image becomes the reference value based on the ratio or difference calculated by the calculating means;
Based on the ratio or difference calculated by the calculation means, the scanning start timing by the light beams from the plurality of light emitting elements so that each of the scanning start positions by the light beams from the plurality of light emitting elements becomes a reference position. Timing changing means for changing each of
An image forming apparatus.   The timing changing unit is configured to delay from the scanning start timing by the specific light beam that starts scanning first to the scanning start timing of a light beam other than the specific light beam based on the ratio or difference calculated by the calculating unit. 2. The scanning start timing by the light beams from the plurality of light emitting elements is changed so as to determine a time and shift the scanning delay timing from the specific light beam by the determined delay time. Image forming apparatus. A light source in which a plurality of light emitting elements that irradiate a light beam according to image data are arranged;
An optical scanning unit configured to scan a light beam emitted from each of the plurality of light emitting elements in a main scanning direction on a scanned surface;
A computing means for computing a ratio or difference of a size of an image formed on a scanned surface by a light beam scanned by the light scanning means with respect to a reference value;
Image correcting means for correcting the image data so that the size of the image becomes the reference value based on the ratio or difference calculated by the calculating means;
Each of the scanning start timings by the light beams from the plurality of light emitting elements is set so that each of the scanning start positions by the light beams from the plurality of light emitting elements becomes a reference position based on the correction contents by the image correcting unit. A timing changing means for changing
An image forming apparatus.   The timing changing unit calculates a delay time from the scanning start timing by the specific light beam that starts scanning first to the scanning start timing of a light beam other than the specific light beam based on the correction content by the image correcting unit. 4. The image according to claim 3, wherein each of the scanning start timings by the light beams from the plurality of light emitting elements is changed so as to be shifted from the scanning start timing of the specific light beam by the determined delay time. Forming equipment. The image correction means performs at least one of addition of pixels and deletion of pixels on the image indicated by the image data based on the magnification calculated by the calculation means, whereby the size of the image is set to the reference The image data is corrected so as to be a value,
5. The image according to claim 3, wherein the timing changing unit changes the scanning start timing by a light beam from the plurality of light emitting elements based on at least one of the added pixel number and the deleted pixel number. Forming equipment. A transfer means for transferring the image formed on the surface to be scanned to an intermediate transfer member for transferring the image to a recording medium;
The calculation means includes a sensor for detecting the position of the image transferred to the intermediate transfer member, calculates the size of the image based on the position of the image detected by the sensor, and calculates the calculated image size. The image forming apparatus according to claim 1, wherein a ratio or difference with respect to a reference value is calculated. It further includes a temperature sensor for detecting the temperature provided in either the own device or outside the device,
The image forming apparatus according to claim 1, wherein the timing changing unit changes the scanning start timing based on a temperature detected by the temperature sensor.

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