JP2011025517A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of reducing a circuit scale, and also, obtaining good image quality, in digital registration correction to digitally correct an inclination upon image formation, caused by attachment accuracy of lenses and mirrors of an exposure device. <P>SOLUTION: Through the use of a means for selecting whether image data are moved or not in the sub scanning direction in accordance with discontinuous points of the image data in image data transition points arranged at equal intervals in a main scanning direction, the image data for canceling the inclination upon image formation caused by the attachment accuracy of the lenses or the mirrors of the exposure device are generated. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus having a function of digitally correcting an inclination at the time of image formation caused by the accuracy of attaching a lens or a mirror of an exposure apparatus.

  In recent years, digitization and colorization are common in image forming apparatuses such as laser printers and copying machines. In these image forming apparatuses, when a color image is formed, images of a plurality of colors such as black (K), yellow (Y), magenta (M), and cyan (C) are superimposed and exposed. There may be a deviation between the color images due to mechanical factors of the apparatus. Therefore, it is a problem how to accurately superimpose the colors so that the image quality does not deteriorate. Therefore, conventionally, the inclination at the time of image formation due to the mounting accuracy of the lens or mirror of the exposure apparatus has been dealt with by adjusting the mounting angle when mounting the lens or mirror.

  However, since a high-accuracy mounting adjustment is costly, a technique has been proposed in which correction is performed by digitally processing image data. For example, image data transfer points are arbitrarily arranged in the main scanning direction, and image data is moved in the sub-scanning direction, thereby correcting image deterioration due to optical tilt.

JP 2005-304011 A

  However, in the conventionally proposed method, since the image data transfer point is arbitrarily arranged in the main scanning direction, it is necessary to have a counter for one main scanning, and there is a problem that the circuit scale increases. .

  In order to solve the above-described problem, the image data transfer points in the main scanning direction are equally spaced so as not to have a counter for one main scan but to have a counter for the interval of image data transfer points. Reduced the scale. The solution is shown below.

  First, the image data transfer points arranged at equal intervals in the main scanning direction can be selected not to move the image data in the sub-scanning direction according to the discontinuous points of the image data.

  The image data transfer points arranged at equal intervals can be set at arbitrary intervals by the transfer point interval storage means.

  The image data transfer points arranged at equal intervals can be started at an arbitrary position by the transfer point start storage means.

  The discontinuous points of the image data are determined from software based on sampling information stored in a storage medium by measuring optical characteristics of the exposure apparatus in advance.

  When moving image data at the image data transfer point, the left image data transfer point is selected at the left and right image data transfer points closest to the discontinuous point of the image data.

  When moving image data at the image data transfer point, the right image data transfer point is selected at the left and right image data transfer points closest to the discontinuous point of the image data.

  When moving image data at the image data transfer point, at the left and right image data transfer points closest to the discontinuous point of the image data, the shorter one of the images at the left and right distance from the discontinuous point of the image data A data transfer point is selected.

  When moving image data at the image data transfer point, the left and right image data transfer points are randomly selected at the left and right image data transfer points closest to the discontinuous point of the image data. .

  According to the present invention, the circuit scale can be made smaller than that of the conventional configuration in digital registration correction for digitally correcting the tilt at the time of image formation caused by the accuracy of attaching the lens and mirror of the exposure apparatus.

1 is a diagram illustrating a main body configuration of an image forming apparatus. It is a figure which shows the structure of the exposure control part of an image forming apparatus. It is a block diagram of the internal circuit of the exposure control part in the Example of this invention. It is the figure which showed the correction method of the image data in the Example of this invention. It is the figure which showed the selection method of the transfer point in Example 1 of this invention. It is the figure which showed the selection method of the transfer point in Example 2 of this invention. It is the figure which showed the selection method of the transfer point in Example 3 of this invention. It is the figure which showed the selection method of the transfer point in Example 4 of this invention. It is the figure which showed the smoothing process at the time of the transfer point in Example 5 of this invention.

Example 1
An embodiment in which the embodiment of the present invention is applied to a four-drum color copying machine in which four photoconductors are arranged in tandem will be described. FIG. 1 is a schematic configuration diagram of the entire color copying apparatus according to the embodiment. First, an outline of a color image reading apparatus (hereinafter referred to as “color scanner”) 1 and a color image recording apparatus (hereinafter referred to as “color printer”) 2 constituting the color copying apparatus will be described with reference to FIG.

  The color scanner 1 forms an image of the document 13 on the color sensor 17 via the illumination lamp 14, the mirror groups 15A, B, C, and the lens 16, and converts the color image information of the document into, for example, blue (Blue, This is read for each color separation light of B (hereinafter referred to as B), green (hereinafter referred to as G), and red (hereinafter referred to as R), and converted into an electrical image signal. Then, based on the color separation image signal intensity levels of B, G, and R obtained by the color scanner 1, color conversion processing is performed by an image processing unit (not shown), and black (hereinafter referred to as Bk), cyan (Cyan, hereinafter referred to as C), magenta (Magenta, hereinafter referred to as M), and yellow (Yellow, hereinafter referred to as Y) color image data are obtained.

  Next, an outline of the color image recording apparatus 2 of FIG. 1 will be described. In the color printer 2, the writing optical units 28M (for magenta), 28Y (for yellow), 28C (for cyan), 28K (for black) provided for each color toner are provided from the color scanner 1. The color image data is converted into an optical signal, and optical writing corresponding to the original image is performed. The photosensitive members 21M (for magenta), 21Y (for yellow), 21C (for cyan), 21K (for black) provided for each color ) To form an electrostatic latent image. These photoconductors 21M, 21Y, 21C, and 21K rotate counterclockwise as indicated by arrows, and around the chargers 27M (for magenta), 27Y (for yellow), and 27C (for cyan) provided for each color, respectively. ), 27K (for black), and around the photosensitive members 21M, 21Y, 21C, and 21K of the respective colors, the M developing unit 213M, the C developing unit 213C, the Y developing unit 213Y, and the Bk developing unit 213K are the photosensitive member 21M, The developing devices are arranged so as to contact 21Y, 21C, and 21K. Also, an intermediate transfer belt 22 as an intermediate transfer member and a first transfer bias blade 217M (for magenta), 217Y (for yellow), 217C (for cyan), 217K (for black) as a first transfer means for each color, It is stretched between a drive roller 220 that drives the intermediate transfer belt 22 by a drive motor (not shown) and driven roller groups 219 and 237.

  Each developing device in each of the image forming systems rotates a developing sleeve that rotates by bringing the ears of the developer into contact with the surface of the photosensitive member to develop the electrostatic latent image, and a developer sleeve that pumps and stirs the developer. It consists of developing paddles.

  The second transfer bias roller 221 is disposed at a position facing the driven roller 219 of the intermediate transfer belt 22, and is provided with a separation / contact mechanism that drives the intermediate transfer belt 22 to be detachable.

  A belt cleaning unit 222 is provided at a predetermined position facing the driven roller 237 on the surface of the intermediate transfer belt 22. The contact / separation operation timing of the belt cleaning unit 222 is separated from the belt surface from the start of printing until the belt transfer of the rear end portion of the final color image is completed, and at the predetermined timing thereafter, the contact / separation mechanism Cleaning is performed by contacting the belt surface (not shown).

  In the color printer unit, first, image formation is started from magenta. Thereafter, cyan image formation is started at a timing delayed from the rotational speed of the intermediate transfer belt 22 by the misalignment between the positions of the photoconductor 21M and the photoconductor 21C. The yellow image formation is started at the timing delayed by the positional deviation between the photosensitive member 21C and the photosensitive member 21CY, and then delayed by the positional deviation between the photosensitive member 21Y and the photosensitive member 21K with respect to the rotational speed of the intermediate transfer belt 22. Black image formation is started at the same timing.

  Each color is processed by the image processing unit, and the image stored in the recording means is read out. Based on this image data from a predetermined timing, the respective color chargers 27M, 27Y, 27C, 27K of the apparatus sequentially and uniformly Optical writing with laser light is performed on the charged photoreceptors 21M, 21Y, 21C, and 21K by the laser scanner units 28M, 28Y, 28C, and 28K for each color, and latent image formation starts sequentially. Hereinafter, magenta image formation will be described as a representative example of four drums. When the exposure of the laser to the photoconductor 21M is started, the developing sleeve of the M developing device 213M rotates and a developing bias is applied so that development can be performed from the leading end portion of the M latent image. Thereafter, the developing operation of the M latent image is continued, and when the trailing end of the latent image passes the M developing position, the development inoperative state is set. The toner image of the first magenta image formed on the photoreceptor 21 is transferred to the intermediate transfer belt 22 by the first transfer bias blade 217M and held on the intermediate transfer belt.

  A series of these operations is sequentially performed in the other units of yellow, cyan, and black, and a full-color toner image formed by the first image of each color is formed on the intermediate transfer belt 22.

  Here, a configuration diagram of the laser scanner unit 28 in the embodiment will be described with reference to FIG. The light emitting element array 281 has four light emitting elements and irradiates four lines at the same time. (M = N = 4) The light emitting element array 281 irradiates the surface of a rotating six-sided polygon mirror coupled to the polygon motor 283 via the lens 282. The polygon motor 283 is polarized so that the laser light of the light emitting element array 281 is scanned six times per rotation. The polarized laser light is detected by a BeamDetect (hereinafter referred to as BD) detection element 286 at the beginning of scanning, and generates a BD signal that triggers the start of exposure for each main scan. On the other hand, an HP sensor signal (not shown) provided on the intermediate transfer member is received, phase control is performed so that the polygon motor 283 is synchronized with the BD signal at the rising edge or falling edge of the signal, and the rising edge of the HP sensor signal. Alternatively, the exposure start timing in the sub-scanning direction is obtained by the falling edge. Further, the scanning speed of the edge is corrected by the fθ lens 284, and the light is polarized by the flat mirror 285 and irradiated to the photosensitive drum 21 disposed below.

  When a full-color toner image is formed on the intermediate transfer belt 22, the second transfer bias roller 221 moves to a position in contact with the intermediate transfer belt by a separation / contact mechanism. A recording medium to be output before a full-color toner image is formed on the intermediate transfer belt 22 is kept on standby by the registration roller 225 from the cassette 223 via the paper feed roller 224 and the transport rollers 226, 227, and 228. When the second transfer bias roller 221 contacts the intermediate transfer belt 22, the registration roller 225 is turned on so that the toner image on the intermediate transfer belt 22 is transferred to a predetermined position on the recording medium, and the recording medium is moved to the second transfer bias. Feed to roller 221. In the second transfer bias roller, a predetermined transfer bias is applied to transfer the toner image on the intermediate transfer belt to the recording medium, whereby the toner images are collectively transferred to the recording medium.

  The recording medium transferred as described above is conveyed to the fixing device 25, and the toner image is melted and fixed by the upper and lower fixing rollers controlled to a predetermined temperature to obtain a high-resolution full-color copy.

  The surface of the intermediate transfer belt 22 after being transferred to the recording medium is cleaned by the cleaning unit 222, and the copying operation is completed.

  Next, the internal circuit of the exposure control unit according to the embodiment of the present invention will be described with reference to FIG. The internal circuit includes a control circuit, image data storage means, transfer point start storage means, transfer point interval storage means, and transfer direction storage means.

  Here, the control circuit performs processing on the image data according to values stored in the transfer point start storage unit, the transfer point interval storage unit, and the transfer direction storage unit.

  The image data storage means is constituted by a memory, for example, and holds the image data processed by the control circuit.

  The transfer point start storage means is composed of, for example, a register, and the start position of the image data transfer point is set and held.

  The transfer point interval storage means is composed of, for example, a register, and sets and holds an interval between points of image data transfer points.

  The transfer direction storage means is composed of, for example, a register. When moving the image data in the sub-scanning direction at each of the transfer points, whether the image data 1Line is incremented by 1 in the sub-scanning direction or decremented by -1. Is set and retained.

  Next, a method for correcting the tilt at the time of image formation caused by the mounting accuracy of the lens and mirror of the exposure apparatus will be described with reference to FIG. Based on the main scanning synchronization signal (Hsync), the transfer point start position is determined according to the register value of the transfer point start means, and the transfer point interval is determined according to the register value of the transfer point interval storage means.

  As shown in FIG. 4, if an optical tilt is generated, it is determined not to move the image data in the sub-operation direction at each transfer point so as to cancel it, and the transfer direction memory is stored when moving. Depending on the means, it is determined whether to +1 or -1 in the sub-scanning direction.

  A method for selecting whether to move the image data in the sub-scanning direction at each transfer point will be described with reference to FIG. Sampling information indicating the optical characteristics of the exposure apparatus is recorded in advance on a recording medium (not shown). The software determines image data discontinuity points according to the sampling information. As shown in FIG. 5, for example, if there is the image data discontinuity point, the transfer point is the left and right image data transfer point closest to the image data discontinuity point, and the left image data transfer point. A point is selected.

(Example 2)
Except for the method for determining the image data transfer point, this is the same as in the first embodiment.

  Now, a method for determining image data transfer points will be described. As shown in FIG. 6, for example, if there is the image data discontinuity point, the transfer point is the right and left image data transfer point closest to the discontinuous point of the image data. A point is selected.

(Example 3)
Except for the method for determining the image data transfer point, this is the same as in the first embodiment.

  Now, a method for determining image data transfer points will be described. As shown in FIG. 7, for example, if there is the image data discontinuity point, the transfer point is the discontinuity of the image data at the left and right image data transfer points closest to the discontinuity point of the image data. The shorter image data transfer point at the left and right distance from the point is selected.

Example 4
Except for the method for determining the image data transfer point, this is the same as in the first embodiment.

  Now, a method for determining image data transfer points will be described. As shown in FIG. 8, for example, if there is the image data discontinuity point, the transfer point is the left and right image data transfer point closest to the discontinuous point of the image data. Points are selected randomly.

(Example 5)
In the same configuration as in the first embodiment, when smoothing processing ON / OFF information is provided in advance in the image data, and the image data is moved in the sub-scanning direction at the image data transfer point, in order to make the image step inconspicuous Smoothing processing is performed.

  As described above, in the first to fifth embodiments, a high-quality image can be provided by generating image data that cancels the inclination at the time of image formation caused by the accuracy of lens and mirror attachment of the exposure apparatus. be able to.

Claims (9)

  An image forming apparatus, wherein image data transfer points arranged at equal intervals in the main scanning direction can be selected not to move image data in the sub-scanning direction according to discontinuous points in the image data.   2. The image forming apparatus according to claim 1, wherein the image data transfer points arranged at equal intervals can be set at arbitrary intervals by a transfer point interval storage unit.   2. The image forming apparatus according to claim 1, wherein the image data transfer points arranged at equal intervals can be started at an arbitrary position by a transfer point start storage unit.   The image forming apparatus according to claim 1, wherein the discontinuous points of the image data are determined from software based on sampling information stored in a storage medium by measuring optical characteristics of an exposure apparatus in advance.   The left image data transfer point is selected at the left and right image data transfer points closest to the discontinuous point of the image data when moving image data at the image data transfer point. The image forming apparatus according to 1.   The image data transfer point on the right side is selected at the left and right image data transfer points closest to the discontinuous point of the image data when moving image data at the image data transfer point. The image forming apparatus according to 1.   When moving image data at the image data transfer point, at the left and right image data transfer points closest to the discontinuous point of the image data, the shorter one of the images at the left and right distance from the discontinuous point of the image data 2. The image forming apparatus according to claim 1, wherein a data transfer point is selected.   When moving image data at the image data transfer point, the left and right image data transfer points are randomly selected at the left and right image data transfer points closest to the discontinuous point of the image data. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 1, wherein ON / OFF information of smoothing processing is added to image data in advance at the image data transfer point.

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