JP2012179830A - Image forming apparatus, method for correcting main scanning magnification therefor, program for correcting main scanning magnification, and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly correct main scanning magnification without deteriorating printing quality.SOLUTION: An image processing circuit 2107 converts an input image signal into pixel data for forming an electrostatic latent image corresponding to one pixel. The pixel data are data of a plurality of bits, and include at least either first bit data for turning on a light source or second bit data for turning off the light source. When inserting or deleting the bit data, if the number of bits of the first bit data included in the pixel data is larger than the number of bits of the second bit data, the image processing circuit inserts or deletes the same bit data as the first bit data in/from the pixel data, and, if the number of bits of the first bit data included in the pixel data is smaller than the number of bits of the second bit data, the image processing circuit inserts or deletes the same bit data as the second bit data in/from the pixel data adjacent to the pixel data, thereby making the input image signal into a corrected image signal. A laser driving circuit 2106 drives the light source on the basis of the corrected image signal.

Description

  The present invention relates to an image forming apparatus, a main scanning magnification correction method thereof, a main scanning magnification correction program, and a recording medium, and more particularly to an image signal obtained by subjecting an image signal to pixel division modulation and a laser based on the pixel division modulated image signal. An image forming apparatus that forms a latent image on the latent image carrier by scanning the image carrier such as a photosensitive drum with laser light emitted from the laser light source by modulating the light source, a main scanning magnification correction method thereof, And a main scanning magnification correction program and a recording medium.

  In general, in an image forming apparatus such as a laser beam printer or a digital copying machine, a light source (for example, a semiconductor laser) is driven by a beam driving circuit when an image is formed. Then, a laser beam (light beam) emitted from the semiconductor laser is modulated by an image signal (also referred to as image data). The modulated laser beam is raster-scanned on an image carrier such as a photosensitive drum by a rotating polygon mirror (polygon mirror) to form a latent image on the photosensitive drum.

  In an image forming apparatus having a plurality of semiconductor lasers, the magnification of the latent image varies depending on the irradiation position on the photosensitive drum irradiated by the laser beam emitted from each semiconductor laser. Further, in the polygon mirror, the surface accuracy of the reflection surface varies from surface to surface, and therefore the latent image writing position on the photosensitive drum varies from reflection surface to reflection surface. In addition, in an image forming apparatus capable of double-sided printing, even if the ratio of latent images on both sides (front and back) is the same due to the shrinkage of the paper size due to heating during fixing, The image size is different after fixing.

  To remedy these inconveniences, when writing the pixel data stream at the laser writing frequency and converting it to a laser beam scanned along the scan line, a slight delay is inserted or removed from the pixel data stream. In some cases, the laser writing frequency is adjusted (see Patent Document 1).

  However, in Patent Document 1, since the laser writing frequency and the image clock for transferring the image data are adjusted, a space is generated when the image clock is made minute, and the print quality is impaired. .

  In order to prevent such deterioration in print quality, a pixel-division-modulated pixel located before the correction point is provided for each of one or more correction points on one scanning line scanned with a laser beam on the photosensitive drum. There is one in which the last bit of data is added as the first bit of pixel data subjected to pixel division modulation positioned at a correction point (see Patent Document 2). In Patent Document 2, for each pixel located after the correction point, pixel data that has been subjected to pixel division modulation is sequentially transferred to the next pixel in bit units, and new pixel data to be added on one scan line is obtained. Generate. This new pixel data is output in synchronization with a fixed-frequency image clock.

  Furthermore, there is one in which the initial insertion position of the pixel piece (bit data) is made random to prevent deterioration in print quality (see Patent Document 3). Here, the initial insertion position is set at random, and thereafter, pixel pieces are inserted at regular intervals from the initial insertion position. This prevents the pixel pieces from continuing in the sub-scanning direction and prevents the quality of the entire image from deteriorating.

JP 2000-238342 A JP 2004-351908 A JP 2000-253215 A

  However, in the method described in Patent Document 2, whether the inserted bit data (hereinafter also simply referred to as a bit) is “0” or “1” depends on the pixel data. For this reason, as described below, depending on the position of the correction point and the image, a density difference may occur and print quality may be impaired.

  FIG. 17 is a conceptual diagram for explaining an example of an image processed by a conventional main scanning magnification correction process and an image after the process. FIG. 17A shows an example of the pre-processing image, and FIG. 17B shows an example of the post-processing image.

  Now, assume that the pre-correction image data shown in FIG. Here, it is assumed that a position indicated by a circle in FIG. 17A is an insertion correction point. When the method described in Patent Document 2 is used, the first bit of the pixel data positioned at the correction point is the same between the last bit of the pixel data positioned before the correction point and the first bit of the pixel data positioned at the correction point. Therefore, in the corrected (after processing) image data, the density of the first half portion becomes high and the density of the second half portion becomes light (FIG. 17B), resulting in a density difference. End up.

  On the other hand, in the method described in Patent Document 3, when the number of insertion points (that is, insertion correction points) increases (for example, when one pixel piece is inserted into two pixels), the density change due to correction is not taken into consideration, and the image quality deteriorates. There are things to do.

  FIG. 18 is a conceptual diagram for explaining another example of an image processed by a conventional main scanning magnification correction process and an image after the process. FIG. 18A is a diagram illustrating another example of the pre-processing image, and FIG. 18B is a diagram illustrating another example of the post-processing image.

  Assume that the initial phase is determined so that the pixel pieces do not continue in the sub-scanning direction when there are many pixel piece insertion locations. For example, it is assumed that the insertion correction point is determined as indicated by a circle in FIG. When the main scanning magnification correction is performed, as shown in FIG. 18B, in the corrected image data, the density of the first half portion becomes high and the density of the second half portion becomes light, resulting in a density difference. End up.

  As described above, when image data whose image cycle is changed in the middle is input, if the auxiliary pixel is inserted by the conventional method, a problem as shown in FIG. 17 occurs. That is, as shown in FIG. 17, image data that forms an image of the same density in the first half and the second half across ▼ is input, and the image data is such that the cycle of the image changes in the ▼ portion. In this case, when auxiliary pixels are inserted in the conventional method, a density difference occurs in an image that should originally be formed with the same density in the first half and the second half.

  Accordingly, an object of the present invention is to provide an image forming apparatus, a main scanning magnification correcting method, a main scanning magnification correcting program, and a recording medium that can appropriately correct the main scanning magnification without deteriorating the print quality. There is to do.

  In order to achieve the above object, an image forming apparatus according to the present invention forms an electrostatic latent image on a photosensitive member by controlling lighting of a light source and scanning a light beam emitted from the light source in a predetermined direction. In an image forming apparatus that forms an image by developing the electrostatic latent image, an input image signal includes first bit data for turning on the light source and second bit data for turning off the light source. Conversion means for converting into pixel data of a plurality of bits including at least one of them, a window part for observing a predetermined number of image data for the input image signal, and a moving means for moving the window part one pixel at a time, In order to correct the length of the image in the predetermined direction, when bit data is inserted or deleted from the pixel data, the pixel data When the pixel data is scheduled to be entered or deleted, the number of bits of the first and second bit data is counted for the pixel data located in the window portion, and the pixel data is located in the window portion. When the number of bits of the first bit data included in the pixel data is larger than the number of bits of the second bit data, the same bit data as the first bit data is inserted into the scheduled pixel data Or, if the number of bits of the first bit data included in the pixel data is smaller than the number of bits of the second bit data, the same bit data as the second bit data is changed to the scheduled pixel data. Correction means for correcting the input image signal by inserting or deleting the pixel data adjacent to the pixel data to obtain a corrected image signal, and the correction And having a drive means for driving the light source based on the image signal.

  Further, the image forming apparatus according to the present invention forms an electrostatic latent image on a photosensitive member by controlling lighting of a light source and scanning a light beam emitted from the light source in a predetermined direction. In an image forming apparatus that forms an image by developing, an input image signal includes at least one of first bit data for turning on the light source and second bit data for turning off the light source. Conversion means for converting into pixel data for forming an electrostatic latent image corresponding to one pixel, and when the pixel data composed of at least one bit data is inserted into or extracted from the input image signal, the pixel data is Number of bits of the first and second bit data included in a predetermined number of the pixel data when the pixel data is planned pixel data to be inserted / extracted It is determined whether or not to insert / remove the pixel piece with respect to the scheduled pixel data according to the number of inserted / extracted pixel pieces to be inserted / extracted with respect to the predetermined number of the pixel data, and according to the determination result Data correction means for correcting the input image signal to obtain a corrected image signal, and drive means for driving the light source based on the corrected image signal.

  Further, the image forming apparatus according to the present invention forms an electrostatic latent image on a photosensitive member by controlling lighting of a light source and scanning a light beam emitted from the light source in a predetermined direction, and forms the electrostatic latent image on the photosensitive member. In an image forming apparatus that forms an image by developing, an input image signal includes at least one of first bit data for turning on the light source and second bit data for turning off the light source. Conversion means for converting into pixel data for forming an electrostatic latent image corresponding to one pixel, and when the pixel data composed of at least one bit data is inserted into or extracted from the input image signal, the pixel data is In the case where the pixel data is planned to be inserted / extracted, the color of the pixel piece to be inserted / extracted according to an average density of a predetermined number of the pixel data is determined. In accordance with the color of the determined pixel piece and the color of the predetermined pixel data, it is determined whether or not to insert the determined pixel piece into the predetermined pixel data, and the input image is determined according to the determination result Data correction means for correcting the signal to obtain a corrected image signal and drive means for driving the light source based on the corrected image signal are provided.

  In the main scanning magnification correction method according to the present invention, an electrostatic latent image is formed on a photosensitive member by controlling lighting of a light source and scanning a light beam emitted from the light source in a predetermined direction. In a main scanning magnification correction method that is used in an image forming apparatus that forms an image by developing and corrects the magnification in the main scanning direction of the photoconductor, an input image signal is defined in advance in the image forming apparatus. A window portion for observing a plurality of image data, and the input image signal is at least one of first bit data for turning on the light source and second bit data for turning off the light source. A conversion step of converting the pixel data into a plurality of bits of pixel data, a movement step of moving the window portion by one pixel, and correcting the length of the image in the predetermined direction Therefore, when bit data is inserted or deleted from the pixel data, if the pixel data is planned pixel data to be inserted or deleted, the pixel located in the window portion The number of bits of the first and second bit data is counted for data, and the number of bits of the first bit data included in the pixel data located in the window portion is the number of bits of the second bit data. If larger than the number, the same bit data as the first bit data is inserted or deleted from the scheduled pixel data, and the number of bits of the first bit data included in the pixel data is the second bit data. If the number of bit data is smaller than the number of bits, the same bit data as the second bit data is converted to pixel data adjacent to the scheduled pixel data. A data correction step of correcting the input image signal by inserting or deleting the input image signal to obtain a corrected image signal, and a driving step of driving the light source based on the corrected image signal. .

  The main scanning magnification correction program according to the present invention forms an electrostatic latent image on a photosensitive member by controlling lighting of a light source and scanning a light beam emitted from the light source in a predetermined direction, and In a main scanning magnification correction program that is used in an image forming apparatus that forms an image by developing and corrects the magnification in the main scanning direction of the photoconductor, the image forming apparatus defines an input image signal in advance. A window section for observing a plurality of image data, and a computer provided in the image forming apparatus for inputting the input image signal to the first bit data for turning on the light source and for turning off the light source. A conversion step of converting the pixel data into a plurality of bit data including at least one of the second bit data, and moving the window portion pixel by pixel When the bit data is inserted or deleted from the pixel data in order to correct the moving step and the length of the image in the predetermined direction, the pixel data will be inserted or deleted. When the pixel data is scheduled pixel data, the number of bits of the first and second bit data is counted for the pixel data located in the window portion, and the first data included in the pixel data located in the window portion is counted. If the number of bits of one bit data is larger than the number of bits of the second bit data, the same bit data as the first bit data is inserted or deleted from the scheduled pixel data, and the pixel data Same as the second bit data if the number of bits of the first bit data included is smaller than the number of bits of the second bit data A data correction step of correcting or correcting the input image signal by inserting or deleting bit data with respect to pixel data adjacent to the scheduled pixel data, and making the light source based on the corrected image signal The driving step of driving is executed.

  A recording medium according to the present invention is a computer-readable recording medium in which the main scanning magnification correction program is recorded.

  According to the present invention, there is an effect that the main scanning magnification can be appropriately corrected without deteriorating the print quality even for an image whose period of the image changes midway.

1 is a longitudinal sectional view schematically showing an example of an image forming apparatus according to an embodiment of the present invention. It is a block diagram which shows an example of the laser beam production | generation apparatus which produces | generates the laser beam (laser beam) which injects into the exposure apparatus shown in FIG. It is a conceptual diagram for explaining insertion correction of a pixel piece according to an embodiment of the present invention, (a) is a diagram showing image data of a vertical line of 1 dot 1 space in which the phase of the image is shifted in the center of the image data, (B) is a figure which shows the image data which corrected the correction scheduled point shown by (a), (c) is a figure which shows the result of having inserted the pixel piece according to the insertion correction point determined by (b). is there. 3 is a flowchart for explaining an example of insertion processing executed by the image processing circuit shown in FIG. 2. It is a figure for demonstrating a mode that the image processing apparatus shown in FIG. 2 performs an insertion process using a window. FIG. 5 is a conceptual diagram for explaining a result when the processing described in FIG. 4 is performed on a 1-dot checker pattern, and (a) is a diagram illustrating an example of image data that is a 1-dot checker pattern; (b) is a diagram showing image data obtained by correcting the scheduled correction point shown in (a), and (c) is a diagram showing a result of pixel piece insertion according to the insertion correction point determined in (b). . BRIEF DESCRIPTION OF THE DRAWINGS It is a conceptual diagram for demonstrating the deletion correction | amendment of the pixel piece by embodiment of this invention, (a) is a figure which shows the image data of the vertical line of 1 dot 1 space where the phase of an image shifts | deviates in the center of image data, (B) is a figure which shows the image data which corrected the deletion correction scheduled point shown by (a). Moreover, (c) is a figure which shows the result of having performed the deletion of a pixel piece according to the deletion correction point determined by (b). 3 is a flowchart for explaining an example of a deletion process executed by the image processing circuit shown in FIG. 2. BRIEF DESCRIPTION OF THE DRAWINGS It is a conceptual diagram for demonstrating the insertion / extraction process of the pixel piece by embodiment of this invention, (a) is a figure which shows the image data of the vertical line of 1 dot 1 space where the phase of an image shifts | deviates in the center of image data, (B) is a diagram showing a case where there are insertion correction points and deletion correction points in the window portion 5A shown in FIG. 5, and (c) is a diagram showing image data obtained by correcting the planned insertion / deletion correction points shown in (a). (D) is a figure which shows the result of having performed insertion / deletion of the pixel piece according to the insertion / deletion correction point determined by (c). 3 is a flowchart for explaining an example of insertion / extraction processing executed by the image processing circuit shown in FIG. 2. FIG. 3 is a block diagram showing a first example of the configuration of the image processing circuit shown in FIG. 2. It is a figure which shows an example of the pulse data stored in the pulse data LUT shown in FIG. 6 is a flowchart for explaining another example of the insertion / extraction process executed by the image processing circuit shown in FIG. 2. FIG. 3 is a block diagram showing a second example of the configuration of the image processing circuit shown in FIG. 2. FIG. 4 is a block diagram illustrating a third example of the configuration of the image processing circuit illustrated in FIG. 2. FIG. 6 is a block diagram illustrating a fourth example of the configuration of the image processing circuit illustrated in FIG. 2. It is a conceptual diagram for demonstrating an example of the image processed by the conventional main scanning magnification correction process, and an image after a process, (a) is a figure which shows an example of an image before a process, (b) is an image of an image after a process It is a figure which shows an example. It is a conceptual diagram for demonstrating the other example of the image processed by the conventional main scanning magnification correction process, and the image after a process, (a) is a figure which shows the other example of the image before a process, (b) is. It is a figure which shows the other example of the image after a process.

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

(First embodiment)
FIG. 1 is a longitudinal sectional view schematically showing an example of an image forming apparatus according to an embodiment of the present invention.

  Referring to FIG. 1, the illustrated image forming apparatus is a so-called color laser beam printer, and includes a transfer material cassette 53. The transfer material (recording paper) set in the transfer material cassette 53 is taken out one by one by the paper feed roller 54, transported by the transport roller pair 55-a and 55-b, and supplied to the image forming unit by the registration roller 56. Sent.

  In the image forming unit, a transfer conveyance belt 10 that conveys a transfer material is stretched flat along a transfer material conveyance direction (right to left in FIG. 1) by a plurality of rotating rollers. The recording sheet is electrostatically attracted to the transfer conveyance belt 10 at the most upstream portion in the conveyance direction of the transfer conveyance belt 10.

  The image forming unit includes developing units 52-C, 52-Y, 52-M, and 52-K. The developing units 52-C, 52-Y, 52-M, and 52-K are photosensitive. Drums 14-C, 14-Y, 14-M, and 14-K are provided. The photosensitive drums 14 -C, 14 -Y, 14 -M, and 14 -K are arranged along the conveyance surface of the transfer conveyance belt 10.

  Furthermore, each of the developing units 52-C, 52-Y, 52-M, and 52-K includes a charger and a developer, and cyan (C), yellow (Y), magenta (M), and Black (K) toners are stored.

  The peripheral surfaces of the photosensitive drums 14-C, 14-Y, 14-M, and 14-K are uniformly charged by a charger, and the exposure devices 51-C, 51-Y, 51-M, and 51-K The photosensitive drums 14-C, 14-Y, 14-M, and 14-K are exposed according to the image data. As a result, electrostatic latent images are formed on the photosensitive drums 14-C, 14-Y, 14-M, and 14-K. These electrostatic latent images are developed by a developing device, and toner images of respective colors are formed on the photosensitive drums 14-C, 14-Y, 14-M, and 14-K.

  The transfer rollers 57-C, 57-Y, 57-M, and 57-K face the photosensitive drums 14-C, 14-Y, 14-M, and 14-K, respectively, with the transfer conveyance belt 10 interposed therebetween. Has been placed. The toner images on the photosensitive drums 14-C, 14-Y, 14-M, and 14-K are transferred by the transfer conveyance belt 10 by transfer rollers 57-C, 57-Y, 57-M, and 57-K, respectively. The images are sequentially superimposed and transferred onto the recording sheet to be conveyed. Thereafter, the recording paper is conveyed to the fixing device 58 where the toner image is fixed. Then, the recording paper is discharged out of the apparatus by a pair of paper discharge rollers 59-a and 59-b.

  The color toner image on the intermediate transfer belt is secondarily transferred to the recording paper using a so-called intermediate transfer belt to which cyan, yellow, magenta, and black toners are directly transferred instead of the transfer conveyance belt 10. You may do it.

  FIG. 2 is a block diagram showing an example of a laser beam generating apparatus that generates laser light (laser beam) incident on the exposure apparatus shown in FIG. In FIG. 2, the suffix of the reference numeral indicating the exposure apparatus shown in FIG. 1 is omitted.

  With reference to FIG. 2, the laser beam generating apparatus includes an image processing circuit 2107. For example, the image processing circuit 2107 is supplied with an image signal (input image signal) obtained as a result of document reading in the image forming apparatus. The image processing circuit 2107 performs pixel division modulation on the image signal, and outputs the image signal subjected to pixel division modulation (hereinafter referred to as a pixel modulation image signal) in synchronization with the image clock. That is, the image processing circuit 2107 converts the image signal into pixel data for forming an electrostatic latent image corresponding to one pixel.

  This pixel data is a plurality of bits of data for driving the semiconductor laser 2101 (light source), the first bit data for turning on the semiconductor laser 2101 and the second bit for turning off the semiconductor laser 2101. Contains at least one of the data.

  The pixel modulation image signal (also referred to as a corrected image signal) is supplied to the laser driving device 2106, and the laser driving circuit 2106 drives (that is, controls lighting) the semiconductor laser (light source) 2101 based on the pixel modulation image signal. .

  Inside the semiconductor laser 2101, a photodiode sensor (PD sensor: not shown) that detects a part of the laser beam is arranged, and the laser driving device 2106 uses the detection signal of the PD sensor to perform APC of the semiconductor laser 2101. (Auto Power Control) control is performed. Laser light (light beam) emitted (emitted) from the semiconductor laser 2101 becomes almost parallel light through an optical system having a collimator lens 2102 and a diaphragm, and is a polygon mirror (rotating polygon mirror) 2103 with a predetermined beam diameter. Is incident on. The polygon mirror 2103 rotates at a constant angular velocity in a predetermined direction, and the laser light incident on the polygon mirror 2103 is reflected as a deflected beam that continuously changes its angle.

  This deflected beam is focused by the f-θ lens 2104. Further, since the f-θ lens 2104 corrects distortion so as to guarantee the temporal linearity of scanning, the deflected beam that has passed through the f-θ lens 2104 is predetermined on the photosensitive drum 14 (suffix omitted). Scanned in the direction at a constant speed. That is, the photosensitive drum 14 is deflected and scanned by the laser beam.

  A beam detect sensor 2105 for detecting a deflected beam is disposed in the vicinity of one end of the photosensitive drum 14, and a detection signal from this sensor is synchronized to synchronize rotation of the polygon mirror 2103 and data writing. Used as a signal.

  In such a laser driving device 2106, in order to keep the light amount of the laser beam during one scan constant, the output of the laser beam is detected in the light detection section during one scan, and the drive current of the semiconductor laser 2101 is scanned one time. A driving method of holding for a while is employed.

  Here, when the image forming apparatus forms an image according to the image data (image signal), the magnification in the main scanning direction (longitudinal direction of the photosensitive drum) (hereinafter referred to as main scanning magnification) is adjusted. Next, an outline of main scanning magnification correction processing in the illustrated image forming apparatus will be described.

  First, a case where the main scanning magnification correction process is performed by inserting and correcting a pixel piece (also referred to as bit data) in the image data will be described.

  FIG. 3 is a conceptual diagram for explaining pixel piece insertion correction according to the embodiment of the present invention. FIG. 3A is a diagram showing the image data of a vertical line of 1 dot 1 space in which the phase of the image is shifted at the center of the image data, and FIG. 3B is the scheduled correction point shown in FIG. It is a figure which shows the image data which corrected this. FIG. 3C is a diagram showing a result of inserting a pixel piece in accordance with the insertion correction point determined in FIG.

  Now, it is assumed that each of the pixels shown in FIG. 3A is composed of 16 pixel pieces (bit data (also simply referred to as bits)). Here, the pixel value is set to 16/16 (FULL) for the black pixel, and the pixel value is set to 0 for the white pixel. A portion (pixel) indicated by a circle in FIG. 3A indicates a preset insertion correction scheduled point. Here, it is assumed that one pixel piece is inserted and corrected for every two pixels.

  In the illustrated example, the insertion correction point is determined for the insertion correction scheduled point indicated by a circle in FIG. 3A as follows. This processing is executed by the image processing circuit 2107 shown in FIG. The configuration of the image processing circuit 2107 will be described later.

  FIG. 4 is a flowchart for explaining an example of insertion processing executed by the image processing circuit 2107 shown in FIG. FIG. 5 is a diagram for explaining a state in which the image processing apparatus 2107 shown in FIG. 2 executes an insertion process using a window portion. The window portion shown in FIG. 5 is virtual and is used when the image processing circuit 2107 performs an insertion process. FIG. 5 shows an example of processing the first line in FIG. The window portion 5A has 1 row and L columns (L is an integer of 2 or more) (L = 4 in the illustrated example). That is, this window portion 5A has four windows. In other words, a predetermined number of pixel data is observed by the window portion 5A.

  With reference to FIG. 2, FIG. 4, and FIG. 5, here, a case where the insertion processing is performed on the image data shown in FIG. FIG. 5A shows the first line of FIG. The image processing circuit 2107 determines an insertion correction point according to the image density in the window as will be described later. First, the image processing apparatus 2107 sets the number of pixels in the line direction (horizontal width) N = 1 and the number of lines M = 1 (step S302). Then, as shown in FIG. 5B, the image processing device 2107 positions the rightmost window of the window 5A as the first pixel (leftmost pixel) as the first pixel in the drawing.

  Subsequently, the image processing circuit 2107 determines whether or not there is a pixel piece insertion scheduled point (insertion correction scheduled point (step S303). In other words, the image processing circuit 2107 determines whether the pixel data is scheduled pixel data. It will be determined whether or not.

  As described above, this insertion correction scheduled point is set in advance. If the pixel is an insertion correction scheduled point (hereinafter also referred to as a target pixel) (YES in step S303), the image processing circuit 2107 counts the number of black pixels and white pixels in the window portion 5A (step S304). .

  At this time, it is assumed that a blank portion, that is, a window in which no pixel is positioned, is a white pixel. In the state shown in FIG. 5B, three white pixels and one black pixel are positioned in the window portion 5A. Further, in the state shown in FIG. 5B, there is no pixel piece other than the target pixel in the window portion 5A.

  Next, the image processing circuit 2107 determines whether or not the target pixel is a white pixel (step S305), and at the same time, the ratio of the number of white pixels in the window portion 5A and the ratio of white pixel piece insertion (white correction number / Calculate the total number of insertions). If the target pixel is a white pixel (YES in step S305), the image processing circuit 2107 determines whether the ratio of the number of white pixels is larger than the ratio of white pixel piece insertion (step S306).

  If the ratio of the number of white pixels is determined to be larger than the ratio of white pixel piece insertion (YES in step S306), the image processing circuit 2107 determines that the target pixel (white) is white pixel pieces (that is, dot dots) according to the determination result. Data "0") is inserted (step S307).

  On the other hand, when the ratio of the number of white pixels is equal to or less than the ratio of white pixel piece insertion (NO in step S306), the image processing circuit 2107 is a pixel adjacent to the left side of the target pixel is a black pixel, and the pixel piece is scheduled to be inserted. It is checked whether there is any (step S308). If the pixel adjacent to the left side of the target pixel is a black pixel and there is no plan to insert a pixel piece (YES in step S308), the image processing circuit 2107 inserts a black pixel piece into the black pixel adjacent to the left side of the target pixel. (Step S309).

  If the pixel adjacent to the left side of the target pixel is not a black pixel and / or if a pixel piece is scheduled to be inserted (NO in step S308), the image processing circuit 2107 proceeds to step S307.

  If the target pixel is not a white pixel in step S305 (NO in step S305), the image processing circuit 2107 determines whether or not the ratio of the number of white pixels is larger than the ratio of white pixel piece insertion (step S310). .

  When the ratio of the number of white pixels is equal to or less than the ratio of white pixel piece insertion (NO in step S310), the image processing circuit 2107 inserts a black pixel piece into the target pixel (black) (step S311). On the other hand, when the ratio of the number of white pixels is larger than the ratio of white pixel piece insertion (NO in step S310), the image processing circuit 2107 is a pixel adjacent to the left side of the target pixel and is a pixel piece insertion schedule. It is checked whether there is any (step S312). If the pixel adjacent to the left side of the target pixel is a white pixel and there is no plan to insert a pixel piece (YES in step S312), the image processing circuit 2107 inserts a white pixel piece into the white pixel adjacent to the left side of the target pixel. (Step S313). If the pixel adjacent to the left side of the target pixel is not a white pixel and / or a pixel piece is scheduled to be inserted (NO in step S312), the image processing circuit 2107 proceeds to step S311.

  In step S303, if the pixel is not the target pixel (NO in step S303), the image processing circuit 2107 does not insert a new pixel piece (step S314).

  Subsequent to step S307, S309, S311, S313, or S314, the image processing circuit 2107 determines whether or not N = horizontal width (step S315). If N = width is not satisfied (NO in step S315), the image processing circuit 2107 sets N = N + 1 (step S316), returns to step S303, and continues the processing.

  If N = width (YES in step S315), the image processing circuit 2107 determines whether M = number of lines (step S317). If M is not the number of lines (NO in step S317), the image processing circuit 316 sets N = 1, sets M = M + 1 (step S318), returns to step S303, and continues the processing. On the other hand, if M = the number of lines (YES in step S317), the image processing circuit 2107 ends the process.

  In this manner, when the number of bits of the first bit data included in the pixel data is larger than the number of bits of the second bit data, the image processing circuit 2107 converts the same bit data as the first bit data into the pixel data. Will be inserted.

  In addition, when the number of bits of the first bit data included in the pixel data is smaller than the number of bits of the second bit data, the image processing circuit 2107 adjoins the pixel data with the same bit data as the second bit data. An image signal is corrected by being inserted into the pixel data to obtain a corrected image signal.

  In the state shown in FIG. 5B, the white pixel ratio = 3/4 from the result of counting in step S304, and since the target pixel is a black pixel, the white pixel piece ratio white pixel ratio = 0. In step S310, it is determined that the white pixel ratio is larger than the white pixel piece insertion ratio. In step S312, since the pixel adjacent to the left side of the target pixel is a white pixel, the image processing circuit 2107 moves the insertion correction point from the black pixel which is the target pixel to the white pixel adjacent to the left (FIG. 5 ( A white pixel piece is inserted into the white pixel (indicated by an arrow in b) (step S313).

  In this way, as shown in FIG. 5B, the insertion correction point of the pixel piece moves to the left white pixel.

  Subsequently, the window portion 5A is shifted to the right by one pixel, and the state shown in FIG. At this time, since the target pixel is not positioned in the right window 5a, no new pixel piece is inserted. Thereafter, the same processing is performed by sequentially shifting the window portion 5A to the right by one pixel at a time.

  In the state shown in FIG. 5D, the number of white pixels and the number of black primes are 2, respectively, and the correction point is 1 for both white and black. That is, since the ratio of the number of white pixels is equal to or less than the ratio of white pixel piece insertion, the insertion correction point is not moved.

  In the state shown in FIG. 5 (e), since the target pixel is not positioned in the right window 5a, no new pixel piece is inserted. In the state shown in FIG. 5F, the number of white pixels and the number of black primes are 2, and the correction point is 2 for black. Accordingly, as indicated by an arrow in the figure, the insertion correction point is moved to the white pixel adjacent to the left side of the target pixel (black). In this way, the processing shown in FIGS. 5G to 5U is performed, and finally, as shown in FIG. 5V, new pixel piece insertion correction points are obtained for one line. It is determined. Then, the same processing is repeated to perform processing up to the final line, and a new pixel piece insertion correction point is determined for the entire image (that is, image data).

  When the processing described with reference to FIGS. 4 and 5 is performed, the pixel piece insertion correction point is changed as shown in FIG. 3B for the image data shown in FIG. Then, when pixel piece insertion processing is performed according to the pixel piece insertion correction point shown in FIG. 3B, the corrected image data shown in FIG. 3C is obtained. Comparing FIG. 3C and FIG. 17B, it can be seen that there is almost no density difference between the first half and the second half in FIG. 3C.

  FIG. 6 is a conceptual diagram for explaining a result when the processing described in FIG. 4 is performed on a 1-dot checker pattern. FIG. 6A is a view showing an example of image data which is a 1-dot checker pattern, and FIG. 6B is a view showing image data obtained by correcting the scheduled correction points shown in FIG. is there. FIG. 6C is a diagram illustrating a result of inserting a pixel piece in accordance with the insertion correction point determined in FIG. 6B.

  Now, it is assumed that there is a pixel piece insertion correction scheduled point at the position (ie, pixel) shown in FIG. At this time, if the pixel piece insertion correction point is moved so that the change in the density difference between the first half portion and the second half portion is reduced in the 1 × 4 window portion 5A described in FIG. 4 and FIG. An insertion correction point is determined at the position shown in b). When a pixel piece is inserted according to the insertion correction point determined in this way, the result shown in FIG. 6C is obtained. As shown in FIG. 6C, it can be seen that even in the 1-dot checker pattern, the density difference between the first half and the second half is very small.

  In this way, if the preset insertion correction point is moved, it is possible to suppress a change in image density caused by the pixel piece insertion.

  Next, a case where the main scanning magnification correction process is performed by deleting and correcting pixel pieces from the image data will be described.

  FIG. 7 is a conceptual diagram for explaining pixel piece deletion correction according to the embodiment of the present invention. FIG. 7A is a diagram showing image data of a vertical line of 1 dot 1 space in which the phase of the image is shifted at the center of the image data, and FIG. 7B is a deletion correction schedule shown in FIG. 7A. It is a figure which shows the image data which corrected the point. FIG. 7C is a diagram illustrating a result of pixel piece deletion according to the deletion correction point determined in FIG. 7B. Here, a portion (pixel) indicated by a cross in FIG. 7A indicates a preset deletion correction scheduled point. Here, one pixel piece is deleted and corrected for every two pixels.

  In the illustrated example, the deletion correction point is determined as follows for the deletion correction scheduled points indicated by crosses in FIG.

  FIG. 8 is a flowchart for explaining an example of the deletion process executed by the image processing circuit 2107 shown in FIG. Note that the window portion 5A described with reference to FIG. 5 is also used here. In the illustrated example, a window portion 5A of 1 row and 4 columns is used.

  With reference to FIG. 2 and FIG. 8, here, a case where the deletion process is performed on the image data shown in FIG. 7A will be described. First, the image processing apparatus 2107 sets the number of pixels in the line direction (horizontal width) N = 1 and the number of lines M = 1 (step S702). The image processing circuit 2107 determines whether or not the pixel is a pixel piece deletion scheduled point (deletion correction scheduled point) (step S703). If the pixel is a deletion correction scheduled point (hereinafter also referred to as a target pixel) (YES in step S703), the image processing circuit 2107 counts the number of black pixels and white pixels in the window portion 5A (step S704). . Further, the image processing circuit 2107 counts the number of deleted black pixel pieces and the number of deleted white pixels.

  Next, the image processing circuit 2107 determines whether or not the pixel of interest is a white pixel (step S705), and at the same time, the ratio of the number of white pixels in the window portion 5A and the ratio of white pixel fragment deletion (number of white corrections / Calculate the total number of deletions). If the target pixel is a white pixel (YES in step S705), the image processing circuit 2107 determines whether the ratio of the number of white pixels is larger than the ratio of white pixel piece deletion (step S706).

  If the ratio of the number of white pixels is larger than the ratio of white pixel piece deletion (YES in step S706), the image processing circuit 2107 deletes the white pixel piece from the target pixel (white) (step S707).

  On the other hand, when the ratio of the number of white pixels is equal to or less than the ratio of white pixel piece deletion (NO in step S706), the image processing circuit 2107 is a pixel adjacent to the left side of the target pixel is a black pixel and the pixel piece is scheduled to be deleted. It is checked whether there is any (step S708). If the pixel adjacent to the left side of the target pixel is a black pixel and there is no plan to delete the pixel piece (YES in step S708), the image processing circuit 2107 deletes the black pixel piece from the black pixel adjacent to the left side of the target pixel. (Step S709).

  If the pixel adjacent to the left side of the target pixel is not a black pixel and / or if there is a pixel piece deletion plan (NO in step S708), the image processing circuit 2107 proceeds to step S707.

  If the target pixel is not a white pixel in step S705 (NO in step S305), the image processing circuit 2107 determines whether or not the ratio of the number of white pixels is larger than the ratio of white pixel piece deletion (step S710). .

  When the ratio of the number of white pixels is equal to or less than the ratio of white pixel piece deletion (NO in step S710), the image processing circuit 2107 deletes the black pixel piece from the target pixel (black) (step S711). On the other hand, if the ratio of the number of white pixels is larger than the ratio of white pixel piece deletion (NO in step S710), the image processing circuit 2107 is a pixel adjacent to the left side of the target pixel and is a pixel piece deletion schedule. It is checked whether there is any (step S712). If the pixel adjacent to the left side of the target pixel is a white pixel and there is no plan to delete the pixel piece (YES in step S712), the image processing circuit 2107 deletes the white pixel piece from the white pixel adjacent to the left side of the target pixel. (Step S713). If the pixel adjacent to the left side of the target pixel is not a white pixel and / or is scheduled to be deleted (NO in step S712), the image processing circuit 2107 proceeds to step S711.

  In step S703, if the pixel is not the target pixel (NO in step S703), the image processing circuit 2107 does not delete a new pixel piece (step S714).

  Subsequent to step S707, S709, S711, S713, or S714, the image processing circuit 2107 determines whether N = horizontal width (step S715). If N = width is not satisfied (NO in step S715), the image processing circuit 2107 sets N = N + 1 (step S716), returns to step S703, and continues the processing.

  If N = width (YES in step S715), the image processing circuit 2107 determines whether M = number of lines (step S717). If M is not the number of lines (NO in step S717), the image processing circuit 316 sets N = 1, sets M = M + 1 (step S718), returns to step S703, and continues the processing. On the other hand, if M = the number of lines (YES in step S717), the image processing circuit 2107 ends the process.

  When the deletion correction point is corrected and determined for the image data shown in FIG. 7A as described above, the deletion correction point is as shown in FIG. 7B. When the image data is corrected according to the deletion correction point shown in FIG. 7B, the result shown in FIG. 7C is obtained. As shown in FIG. 7C, it can be seen that the density difference between the first half and the second half of the corrected image data becomes extremely small even when the pixel piece is deleted.

  In this way, by moving the deletion correction point, it is possible to suppress changes in the image density due to pixel piece deletion.

  Next, a case where the main scanning magnification correction processing is performed by performing processing for inserting / deleting pixel pieces (hereinafter referred to as insertion / removal processing) on the image data will be described.

  FIG. 9 is a conceptual diagram for explaining pixel piece insertion / extraction processing according to the embodiment of the present invention. FIG. 9A is a diagram showing vertical dot image data of one dot and one space in which the phase of the image is shifted at the center of the image data, and FIG. 9B is inserted into the window portion 5A shown in FIG. It is a figure which shows the case where there exists a correction point and a deletion correction point. FIG. 9C is a diagram showing image data in which the insertion / deletion correction scheduled points shown in FIG. 9A are corrected. FIG. 9D is a diagram showing a result of inserting / deleting pixel pieces according to the insertion / deletion correction points determined in FIG. 9C. Here, a portion (pixel) indicated by a circle in FIG. 9A indicates a preset insertion correction scheduled point, and a portion (pixel) indicated by a cross indicates a preset deletion correction scheduled point. ing. Here, one pixel piece is inserted / extracted for every two pixels.

  In the illustrated example, insertion / deletion correction points are determined as follows for the insertion / deletion correction scheduled points indicated by circles and crosses in FIG. 9A.

  FIG. 10 is a flowchart for explaining an example of the insertion / extraction process executed by the image processing circuit 2107 shown in FIG.

  With reference to FIG.2 and FIG.10, the case where an insertion / extraction process is performed about the image data shown to Fig.9 (a) here is demonstrated. First, the image processing apparatus 2107 sets the number of pixels in the line direction (horizontal width) N = 1 and the number of lines M = 1 (step S902). The image processing circuit 2107 determines whether or not the pixel is a pixel piece insertion / extraction scheduled point (insertion / extraction correction scheduled point) (step S903). When the pixel is the insertion / extraction correction scheduled point (hereinafter also referred to as a target pixel) (YES in step S903), the image processing circuit 2107 counts the number of black pixels and white pixels in the window portion 5A (step S904). . Further, the image processing circuit 2107 counts the number of black pixel pieces inserted and removed and the number of white pixels inserted and removed.

  In the example shown in the figure, when counting the number of black pixel pieces inserted / extracted and the number of white pixels inserted / extracted, “+1” is set for one insertion correction point (scheduled point) and “−1” is set for one deletion correction point (scheduled point). ", The total in the window portion 5A is counted.

  Next, the image processing circuit 2107 determines whether the black and white pixel ratio and the white pixel piece insertion ratio are closer when the pixel piece is inserted into and extracted from the pixel of interest than when the pixel piece is inserted into and extracted from the adjacent pixel on the left side. Determination is made (step S906). If the black and white pixel ratio and the white pixel piece insertion ratio are closer when the pixel piece is inserted into and extracted from the pixel of interest than when the pixel piece is inserted into the left adjacent pixel (YES in step S906), the image processing circuit 2107 Then, a pixel piece having the same color as the pixel piece is inserted into or extracted from the target pixel (step S907).

  On the other hand, when the pixel piece is inserted into and extracted from the pixel of interest, the black and white pixel ratio and the white pixel piece insertion ratio are not closer than in the pixel adjacent to the left side (NO in step S906). The circuit 2107 determines whether there is a plan to insert or remove a pixel piece for a pixel adjacent to the left side of the target pixel (step S908).

  If there is a plan to insert or remove a pixel piece from the pixel adjacent to the left side of the target pixel (NO in step S908), the image processing circuit 2107 proceeds to step S907. If there is no plan to insert / extract a pixel piece for a pixel adjacent to the left side of the target pixel (YES in step S908), the image processing circuit 2107 inserts / extracts a pixel piece for a pixel adjacent to the left side of the target pixel (step S909). .

  In step S903, if the pixel is not the target pixel (NO in step S903), the image processing circuit 2107 determines that no new pixel piece is inserted or removed (step S914).

  Subsequent to step S907, S909, or S914, the image processing circuit 2107 determines whether or not N = horizontal width (step S915). If N = width is not satisfied (NO in step S915), the image processing circuit 2107 sets N = N + 1 (step S916), returns to step S303, and continues the processing.

  If N = width (YES in step S915), the image processing circuit 2107 determines whether M = number of lines (step S917). If M is not the number of lines (NO in step S916), the image processing circuit 2107 sets N = 1, sets M = M + 1 (step S918), returns to step S303, and continues the processing. On the other hand, if M = the number of lines (YES in step S917), the image processing circuit 2107 ends the process.

  Incidentally, in the process of determining the insertion / extraction correction point, there are cases where both insertion and deletion correction points exist in the window portion 5A as shown in FIG. 9B. In the state shown in FIG. 9B, the image processing circuit 2107 counts the pixels and pixel pieces in the window portion 5A in step S904 as described above. In the example shown in FIG. 9B, there are two black pixels and two white pixels, and one white pixel piece is inserted.

  Here, the target pixel is a pixel piece deletion scheduled point as shown in FIG. 9B, but since the color of the target pixel is a black pixel, if the pixel piece is deleted from the target pixel, the window portion 5A The density is shifted by the pixel piece insertion / extraction. In the illustrated example, the pixel adjacent to the left side of the target pixel is a white pixel, and there is no plan to insert or remove a pixel piece. Therefore, the image processing circuit 2107 moves the pixel piece deletion position from the target pixel to the white pixel adjacent to the left side and deletes the white pixel piece from the white pixel adjacent to the left side in order to suppress the density variation. .

  As described above, when the insertion / extraction correction points are corrected and set for the image data shown in FIG. 9A, the insertion / extraction correction points are as shown in FIG. 9C. Then, when the image data is corrected according to the insertion / extraction correction points shown in FIG. 9C, the result shown in FIG. 9D is obtained. As shown in FIG. 9 (d), even when the pixel pieces are inserted and removed, the pixel pieces are inserted or deleted so that the left and right image sizes are equally drawn. The densities of the left and right images are also almost equal.

  In this way, by moving the insertion / extraction correction point, it is possible to suppress changes in image density due to the insertion / extraction of the pixel pieces.

  Next, a control system for executing the above-described main scanning magnification correction process will be described. FIG. 11 is a block diagram showing an example of the configuration of the image processing circuit 2107 shown in FIG.

  2 and 11, the image processing circuit 2107 includes a control signal generation circuit 1201. Although not shown in FIG. 11, the control signal generation circuit 1201 is provided with the number of segments and the segments 0 to m (m is an integer of 1 or more) from the CPU provided in the image forming apparatus shown in FIG. Each of the segments 0 to m has a segment width and the number of correction points (correction points). Here, the main scan is divided into a plurality of segments and processed. For example, an SRAM table corresponding to the number of segments is held in the control signal generation circuit 1201, and the segment width (number of pixels) and the number of correction points in the segment are held in the SRAM table for each segment.

  The control signal generation circuit 1201 has a FIFO (First In-First Out Memory) clock generation circuit 1203 and a parallel-serial (hereinafter referred to as PS) conversion / bit data insertion / extraction circuit 1208 based on the number of segments and the segments 0 to m. A bit data insertion / extraction position signal 1252 is provided. Note that this signal is shown in FIG.

  Further, the control signal generation circuit 1201 provides the SP conversion control signal 1253 to the serial-parallel (hereinafter referred to as SP) clock generation circuit 1204 based on the number of segments and the segments 0 to m. Based on the reference clock 1251 and the bit data insertion / extraction position signal 1252, the FIFO clock generation circuit 1203 reads a read clock from the FIFO 1202, the delay time generation circuit 1205, the pulse data LUT (Look UP Table) 1207, and the LUT address generation circuit 1206. 1254 is given.

  The SP clock generation circuit 1204 provides the SP conversion clock 1255 to the SP conversion circuit 1209 based on the reference clock 1251 and the SP conversion control signal 1253. The SP conversion clock 1255 is output from the SP clock generation circuit 1204 as an image clock.

  The FIFO 1202 is supplied with a FIFO write signal 1256 and a write clock 1259 from a main body control unit (that is, a CPU), and also receives an image signal in units of pixels from an image generation unit (not shown). The upper 2 bits of this image signal are pulse positions, and the lower 4 bits are pixel values that have been subjected to halftone processing. That is, 6-bit write pixel data 1257 is input to the FIFO 1202. The FIFO 1202 outputs 6-bit read pixel data 1261 according to the read clock 2254 and the FIFO read signal 1260 supplied from the delay time generation circuit 1205.

  Read pixel data 1261 is input to a delay time generation circuit 1205. The delay time generation circuit 1205 adjusts the FIFO read signal 1260 according to the delay time 1263 specified by the main body control unit with reference to the BD signal 1262 output from the BD sensor. Then, the delay time generation circuit 1205 inputs the pixel data (pixel value 1265 and pulse position 1266) and the pixel data valid signal 1264 to the LUT address generation circuit 1206 after the delay time 1263 has elapsed with reference to the BD signal 1262. .

  The LUT address generation circuit 1206 reads 16-bit pulse data 1268 from the pulse data LUT 1207 based on the pixel data (pixel value 1265 and pulse position 1266) input from the delay time generation circuit 1205 and the pixel data valid signal 1264. The pulse data LUT 1207 stores 16-bit pulse data for a 4-bit pixel value for each pulse position.

  FIG. 12 is a diagram showing an example of pulse data stored in the pulse data LUT 1207 shown in FIG.

  As shown in FIG. 12, if the pulse position 1266 is 2′b00, the center is 2′b01, the right justification is 2′b01, the left justification is 2′b10, and the split is 2′b11, the pulse position 1266 is the upper 2 bits. The 6-bit signal with the pixel value 1265 as the lower 4 bits may be used as the pulse data LUT address 1267. Note that the pulse data LUT 1207 may be implemented by a ROM (Read Only Memory), or may be implemented by a RAM (Random Access Memory), and pulse data may be written into the RAM from the main body control unit. .

  The LUT address generation circuit 1206 supplies 16-bit LUT output pulse data 1268 as pulse data 1270 to the PS conversion / bit data insertion / extraction circuit 1208 together with the pulse position 1271 in synchronization with the pulse data valid signal 1269.

  The PS conversion / bit data insertion / extraction circuit 1208 converts the pulse data 1270 input from the LUT address generation circuit 1206 into a serial pixel signal based on the PS conversion clock (reference clock) 1251. Further, the PS conversion / bit data insertion / extraction circuit 1208 discriminates an insertion / extraction correction point according to the pulse data 1270 and performs bit data insertion / extraction.

  As shown in the figure, the PS conversion / bit data insertion / extraction circuit 1208 has a window buffer 1208a of one row and L lines. The window buffer 1208a stores pixel values processed before the current pixel and insertion / extraction positions as buffer data. The PS conversion / bit data insertion / extraction circuit 1208 refers to the buffer data and the bit data insertion / extraction position signal 1252 and determines whether or not to move (correct) the insertion / extraction correction point.

  The serial pixel signal 1272 after the bit data insertion / extraction output from the PS conversion / bit data insertion / extraction circuit 1208 is input to the SP conversion circuit 1209. The SP conversion circuit 1209 converts the input serial pixel signal 1272 into a 16-bit parallel pixel signal 1273 by the SP conversion clock 1255 and outputs the converted signal.

(Second Embodiment)
In the first embodiment described above, the case where the pixel values are black (all lighting) and white has been described, but the present invention can be applied even if the pixel values are halftone.

  FIG. 13 is a flowchart for explaining another example of the insertion / extraction process executed by the image processing circuit 2107 shown in FIG.

  With reference to FIG. 2 and FIG. 13, it is assumed here that the pixel value is a halftone. First, the image processing apparatus 2107 sets the number of pixels in the line direction (horizontal width) N = 1 and the number of lines M = 1 (step S1402). The image processing circuit 2107 determines whether or not the pixel is a pixel piece insertion / extraction scheduled point (insertion / extraction correction scheduled point) (step S1403). When the pixel is the insertion / extraction correction scheduled point (hereinafter also referred to as a target pixel) (YES in step S1403), the image processing circuit 2107 determines the average density, the black pixel piece insertion / extraction number, and the white pixel insertion / extraction number in the window portion 5A. Is counted (step S1404).

  In the example shown in the figure, when the number of black pixel pieces inserted / extracted is counted, “+1” is set for one insertion correction point (scheduled point), and “−1” is set for one deletion correction point (scheduled point). The total in the window portion 5A is counted.

  Next, the image processing circuit 2107 determines the color of the insertion / extraction pixel piece so that the change in the average density is minimized (smaller) (step S1405). Then, the image processing circuit 2107 determines whether the target pixel is the same color as the inserted / extracted pixel piece or whether the target pixel is an intermediate color (step S1406).

  If the target pixel is the same color as the inserted / extracted pixel piece or the target pixel is an intermediate color (YES in step S1406), the image processing circuit 2107 inserts / extracts the pixel piece of the color determined in step S1405 described above with respect to the target pixel. (Step S1407).

  If the target pixel is not the same color as the inserted / extracted pixel piece and the target pixel is not an intermediate color (NO in step S1406), the image processing circuit 2107 determines whether there is a plan to insert / extract the pixel piece from the pixel adjacent to the left side of the target pixel. (Step S1408).

  If there is a plan to insert / extract a pixel piece for a pixel adjacent to the left side of the pixel of interest (NO in step S1408), the image processing circuit 2107 inserts / extracts a pixel piece of the same color as the pixel of interest (step S1411). On the other hand, if there is no plan to insert or remove a pixel piece for a pixel adjacent to the left side of the target pixel (YES in step S1408), the image processing circuit 2107 determines whether the pixel adjacent to the left side of the target pixel has the same color as the inserted pixel piece. Alternatively, it is determined whether or not the target pixel is an intermediate color (step S1409).

  If the pixel adjacent to the left side of the target pixel is not the same color as the inserted / extracted pixel piece and the target pixel is not an intermediate color (NO in step S1409), the image processing circuit 2107 proceeds to step S1411. If the pixel adjacent to the left side of the target pixel is the same color as the inserted / extracted pixel piece or the target pixel is an intermediate color (YES in step S1409), the image processing circuit 2107 displays the pixel piece of the color determined in step S1405 described above. Are inserted into and extracted from the pixel adjacent to the left side of the friend pixel (step S1410).

  If it is determined in step S1403 that the pixel is not a pixel of interest (NO in step S1403), the image processing circuit 2107 determines that no new pixel piece is inserted (step S1412).

  Subsequent to step S1407, S1410, S1411, or S1412, the image processing circuit 2107 determines whether or not N = width (step S1413). If N = width is not satisfied (NO in step S1413), the image processing circuit 2107 sets N = N + 1 (step S1414), returns to step S1403, and continues the processing.

  If N = width (YES in step S1413), the image processing circuit 2107 determines whether M = number of lines (step S1415). If M is not the number of lines (NO in step S1415), the image processing circuit 2107 sets N = 1, sets M = M + 1 (step S1416), returns to step S1403, and continues the processing. On the other hand, if M = the number of lines (YES in step S1415), the image processing circuit 2107 ends the process.

  The above-described processing is performed for all lines, and the image processing circuit 2107 newly determines a pixel piece insertion / extraction point of the entire image. Then, the image processing circuit 2107 performs pixel piece insertion / extraction processing according to the determined insertion / extraction correction point. As a result, even when the pixel value is halftone, the pixel piece insertion / extraction processing can be performed without impairing the image density.

  Incidentally, in the process of determining the insertion / extraction correction point, there are cases where both insertion and deletion correction points exist in the window portion 5A as shown in FIG. 9B. In the state shown in FIG. 9B, the image processing circuit 2107 counts the pixels and pixel pieces in the window portion 5A in step S904 as described above. In the example shown in FIG. 9B, there are two black pixels and two white pixels, and one white pixel piece is inserted.

  Here, the target pixel is a pixel piece deletion scheduled point as shown in FIG. 9B, but since the color of the target pixel is a black pixel, if the pixel piece is deleted from the target pixel, the window portion 5A The density is shifted by the pixel piece insertion / extraction. In the illustrated example, the pixel adjacent to the left side of the target pixel is a white pixel, and there is no plan to insert or remove a pixel piece. Therefore, the image processing circuit 2107 moves the pixel piece deletion position from the target pixel to the white pixel adjacent to the left side and deletes the white pixel piece from the white pixel adjacent to the left side in order to suppress the density variation. .

  As described above, when the insertion / extraction correction points are corrected and set for the image data shown in FIG. 9A, the insertion / extraction correction points are as shown in FIG. 9C. Then, when the image data is corrected according to the insertion / extraction correction points shown in FIG. 9C, the result shown in FIG. 9D is obtained. As shown in FIG. 9 (d), even when the pixel pieces are inserted and removed, the pixel pieces are inserted or deleted so that the left and right image sizes are equally drawn. The densities of the left and right images are also almost equal.

  In this way, by moving the insertion / extraction correction point, it is possible to suppress changes in image density due to the insertion / extraction of the pixel pieces.

  FIG. 14 is a block diagram showing a second example of the configuration of the image processing circuit 2107 shown in FIG.

  Referring to FIG. 14, the same components as those of image processing circuit 2107 shown in FIG. In the image processing circuit 2107 shown in FIG. 14, there is no pulse data LUT 1207, and a pulse data generation circuit 1210 is used instead of the LUT address generation circuit 1206 shown in FIG.

  When generating 16-bit pulse data from a 4-bit pixel value, the pulse data generation circuit 1210 generates pulse data 1270 according to the pixel value 1265 and the pulse position 1266. The pulse data generation circuit 1210 supplies the pulse data 1270 to the PS conversion / bit data insertion / extraction circuit 1208 together with the pulse position 1271 in synchronization with the pulse data valid signal 1269.

  FIG. 15 is a block diagram showing a third example of the configuration of the image processing circuit 2107 shown in FIG.

  Referring to FIG. 15, the same components as those of image processing circuit 2107 shown in FIG. In the image processing circuit 2107 shown in FIG. 15, a FIFO having a bit width of 18 bits is used as the FIFO 1202. Further, there is no pulse data LUT 1207 and pulse data generation circuit 1206 shown in FIG. The delay time generation circuit 1205 is connected to the PS conversion / bit data insertion / extraction circuit 1208. Write pixel data 1257 input from an image generator (not shown) is not 6-bit pixel data (2 bits are pulse positions, 4 bits are pixel values) but 18-bit pixel data (2 bits are The pulse position and 16 bits are pulse data). Thus, if 18-bit pixel data is used, hardware (LUT address generation circuit 1206 and pulse data LUT 1207 shown in FIG. 11 or pulse data generation circuit 1210 shown in FIG. 14) for generating pulse data from the pixel value is unnecessary. It becomes.

  FIG. 16 is a block diagram showing a fourth example of the configuration of the image processing circuit 2107 shown in FIG.

  Referring to FIG. 16, the same components as those of image processing circuit 2107 shown in FIG. In the image processing circuit 2107 shown in FIG. 16, the control signal generation circuit 1201 includes a window buffer 1208a. When pixel data is written into the FIFO 1202, the control signal generation circuit 1201 inserts / extracts pixel data and bit data into / from the window buffer 1208a. A position schedule signal (not shown) is written as buffer data. The bit data insertion / extraction position forecast signal is generated by the control signal generation circuit 1201 according to the pixel data, the number of segments, and the segments.

  The control signal generation circuit 1201 generates a bit data insertion / extraction position signal 1273 according to the pixel data and the bit data insertion / extraction position schedule signal held in the window buffer 1208a. Then, the PS conversion / bit data insertion / extraction circuit 1208 determines the insertion / extraction position of the bit data according to the bit data insertion / extraction position signal, and inserts / deletes the bit data.

  In this manner, in the image processing circuit 2107 shown in FIG. 16, the control signal generation circuit 1201 determines the bit data insertion / extraction position in advance, so that the configuration of the PS conversion / bit data insertion / extraction circuit 1208 can be simplified.

  Note that the FIFO clock generation circuit 1203 may delay the read clock 1254 in units of the reference clock 1251 period. As a result, a delay time can be generated in units of the period of the reference clock 1251, and when used in combination with a delay time generation circuit 1205 that generates a delay time in units of the period of the read clock 1254, higher-definition line start position adjustment is possible. Can be done.

  Further, the control signal generator 1201 may change the timing for enabling the bit data insertion / extraction position signal at random for each line. Thereby, the position of the correction pixel can be randomly changed for each line without changing the number of corrections and the correction frequency in the line. Therefore, it is possible to prevent occurrence of a vertical stripe pattern that may occur when the correction pixel arrangement is random and the position of the correction pixel is not changed for each line.

  As is clear from the above description, the image processing apparatus 2107 shown in FIG. 2 functions as a conversion unit and a data correction unit. The laser driving device 2106 functions as a driving unit.

  As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to these embodiment, Various forms of the range which does not deviate from the summary of this invention are also contained in this invention. .

  For example, the function of the above embodiment may be used as the main scanning magnification correction method, and this correction method may be executed by the image processing forming apparatus. In addition, a program having the functions of the above-described embodiments may be used as a main scanning magnification correction program, and this correction program may be executed by a computer provided in the image processing apparatus.

  At this time, the main scanning magnification correction method and the main scanning magnification correction program have at least a conversion step, a data correction step, and a driving step.

  The present invention can also be realized by executing the following processing. That is, software (program) for realizing the functions of the above-described embodiments is supplied to a system or apparatus via a network or various recording media, and a computer (or CPU, MPU, etc.) of the system or apparatus reads the program. It is a process to be executed.

1201 Control signal generation circuit 1202 FIFO
1203 FIFO clock generation circuit 1204 SP clock generation circuit 1205 Delay time generation circuit 1206 LUT address generation circuit 1207 Pulse data LUT
1208 PS conversion / bit data insertion / extraction circuit 1209 SP conversion circuit 2107 Image processing circuit

Claims (9)

Image formation in which an electrostatic latent image is formed on a photosensitive member by controlling the lighting of a light source and scanning a light beam emitted from the light source in a predetermined direction, and image formation is performed by developing the electrostatic latent image In the device
Conversion means for converting an input image signal into a plurality of bit data including at least one of first bit data for turning on the light source and second bit data for turning off the light source;
A window portion for observing a predetermined number of image data for the input image signal;
Moving means for moving the window portion one pixel at a time;
In order to correct the length of the image in the predetermined direction, when inserting or deleting bit data with respect to the pixel data, the pixel data is planned pixel data that is scheduled to insert or delete bit data. In some cases, the first bit data included in the pixel data located in the window portion is obtained by counting the number of bits of the first and second bit data for the pixel data located in the window portion. Is greater than the number of bits of the second bit data, the same bit data as the first bit data is inserted or deleted from the scheduled pixel data, and the first bit data included in the pixel data If the number of bits of one bit data is smaller than the number of bits of the second bit data, the same bit data as the second bit data is forwarded A data correction means to the corrected image signal by correcting the input image signal by inserting or deleting the pixel data adjacent to schedule pixel data,
An image forming apparatus comprising: drive means for driving the light source based on the corrected image signal.   When the number of bits of the first bit data is smaller than the number of bits of the second bit data, the data correction unit is adjacent when the pixel data adjacent to the pixel data is not the scheduled pixel data. The image forming apparatus according to claim 1, wherein the same bit data as the second bit data is inserted into or deleted from the pixel data. Image formation in which an electrostatic latent image is formed on a photosensitive member by controlling the lighting of a light source and scanning a light beam emitted from the light source in a predetermined direction, and image formation is performed by developing the electrostatic latent image In the device
An input image signal includes at least one of first bit data for turning on the light source and second bit data for turning off the light source, and forms an electrostatic latent image corresponding to one pixel. Conversion means for converting into pixel data for
When inserting / extracting a pixel piece composed of at least one bit data from / to the input image signal, when the pixel data is planned pixel data to be inserted / extracted, a predetermined number of pixels Depending on the number of bits of the first and second bit data included in the pixel data and the number of inserted / extracted pixel pieces to be inserted / extracted with respect to the predetermined number of the pixel data, Data correction means for determining whether to insert or remove the pixel piece, and correcting the input image signal according to the determination result to obtain a corrected image signal;
An image forming apparatus comprising: drive means for driving the light source based on the corrected image signal.   The data correction means includes the number of bits of the first and second bit data included in the predetermined number of the pixel data and the insertion / extraction pixel inserted / extracted with respect to the predetermined number of the pixel data. The variation between the ratio of the first bit data included in the predetermined number of pixel data obtained in accordance with the number of pieces and the ratio of the inserted / extracted pixel pieces made of the first bit data is minimized. 4. The image forming apparatus according to claim 3, wherein the pixel data for inserting and removing the pixel piece is changed from the planned pixel data to pixel data adjacent to the planned pixel data. Image formation in which an electrostatic latent image is formed on a photosensitive member by controlling the lighting of a light source and scanning a light beam emitted from the light source in a predetermined direction, and image formation is performed by developing the electrostatic latent image In the device
An input image signal includes at least one of first bit data for turning on the light source and second bit data for turning off the light source, and forms an electrostatic latent image corresponding to one pixel. Conversion means for converting into pixel data for
When inserting / extracting a pixel piece composed of at least one bit data from / to the input image signal, when the pixel data is planned pixel data to be inserted / extracted, a predetermined number of pixels The color of the pixel piece to be inserted / extracted is determined according to the average density of the pixel data, and the determined color for the planned pixel data is determined according to the determined color of the pixel piece and the color of the planned pixel data Data correction means for determining whether or not to insert and remove a pixel piece, and correcting the input image signal according to the determination result to obtain a corrected image signal;
An image forming apparatus comprising: drive means for driving the light source based on the corrected image signal.   The data correction unit is configured to determine the predetermined pixel data when the color of the determined pixel piece and the color of the predetermined pixel data are the same color or when the color of the predetermined pixel data is an intermediate color. If the color of the determined pixel piece and the color of the planned pixel data are not the same color and the color of the planned pixel data is not an intermediate color, the pixel data adjacent to the planned pixel data is 6. The image forming apparatus according to claim 5, wherein the determined pixel piece is inserted and removed. Image formation in which an electrostatic latent image is formed on a photosensitive member by controlling the lighting of a light source and scanning a light beam emitted from the light source in a predetermined direction, and image formation is performed by developing the electrostatic latent image In a main scanning magnification correction method for correcting a magnification in the main scanning direction of the photoconductor used in an apparatus,
The image forming apparatus includes a window unit for observing a predetermined number of image data for an input image signal,
A conversion step of converting the input image signal into pixel data of a plurality of bits including at least one of first bit data for turning on the light source and second bit data for turning off the light source;
A moving step of moving the window portion pixel by pixel;
In order to correct the length of the image in the predetermined direction, when inserting or deleting bit data with respect to the pixel data, the pixel data is planned pixel data that is scheduled to insert or delete bit data. In some cases, the first bit data included in the pixel data located in the window portion is obtained by counting the number of bits of the first and second bit data for the pixel data located in the window portion. Is greater than the number of bits of the second bit data, the same bit data as the first bit data is inserted or deleted from the scheduled pixel data, and the first bit data included in the pixel data If the number of bits of one bit data is smaller than the number of bits of the second bit data, the same bit data as the second bit data is forwarded A data correcting step to corrected image signal by correcting the inserted or deleted to the input image signal to the pixel data adjacent to schedule pixel data,
And a driving step for driving the light source based on the corrected image signal. Image formation in which an electrostatic latent image is formed on a photosensitive member by controlling the lighting of a light source and scanning a light beam emitted from the light source in a predetermined direction, and image formation is performed by developing the electrostatic latent image In the main scanning magnification correction program for correcting the magnification in the main scanning direction of the photoconductor used in the apparatus,
The image forming apparatus includes a window unit for observing a predetermined number of image data for an input image signal,
In the computer provided in the image forming apparatus,
A conversion step of converting the input image signal into pixel data of a plurality of bits including at least one of first bit data for turning on the light source and second bit data for turning off the light source;
A moving step of moving the window portion pixel by pixel;
In order to correct the length of the image in the predetermined direction, when inserting or deleting bit data with respect to the pixel data, the pixel data is planned pixel data that is scheduled to insert or delete bit data. In some cases, the first bit data included in the pixel data located in the window portion is obtained by counting the number of bits of the first and second bit data for the pixel data located in the window portion. Is greater than the number of bits of the second bit data, the same bit data as the first bit data is inserted or deleted from the scheduled pixel data, and the first bit data included in the pixel data If the number of bits of one bit data is smaller than the number of bits of the second bit data, the same bit data as the second bit data is forwarded A data correcting step to corrected image signal by correcting the inserted or deleted to the input image signal to the pixel data adjacent to schedule pixel data,
And a drive step of driving the light source based on the corrected image signal.   A computer-readable recording medium on which the main scanning magnification correction program according to claim 8 is recorded.

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