JP2010048895A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform line shift of image data in the sub-scanning direction as registration shift correction, if line shift is performed at the same main scanning pixel position in each line, the position where the line is shifted is noticeable and the image quality is lowered. In addition, in order to make the line shift portion inconspicuous, there is a case where correction is performed to add pixels before and after the shift portion. At this time, if the line shift is always performed at the same main scanning pixel position, the toner concentrates on the shifted position due to the additional pixels, and the dirt and partial deterioration of the drum tend to concentrate.
The line shift pixel position is not fixed but is moved for each line or page, thereby preventing image quality improvement when no additional pixels are performed and toner concentration when performing additional pixels.

Description

  The present invention relates to an image forming apparatus that forms an image by correcting bending of a scanning line during image formation using image data, and a corrected image generation method in the apparatus.

  In recent years, a tandem method has been widely employed in order to increase the image forming speed in an electrophotographic color image forming apparatus (laser printer). In this system, as many developing devices and photosensitive drums as the number of types of color materials (toners) are arranged, and images of different colors are sequentially transferred onto a conveyance belt or a recording sheet to form a color image. In such a tandem color image forming apparatus, since images of different colors are formed by the image forming units corresponding to the respective colors, there are a plurality of factors that cause registration deviation between the images of the respective colors. Various countermeasures for correcting are proposed.

  As one of those factors, there may be a non-uniformity of the lens of the deflection scanning device that performs the deflection scanning of the laser light, a mounting position shift of the lens, a mounting position shift of the deflection scanning device to the image forming apparatus body, and the like. When such a situation occurs, the laser light scanning line is tilted or bent. Further, since the inclination and the degree of bending of the scanning line are different for each color, a registration error appears as a result.

  As a method for coping with such a registration deviation, in Patent Document 1, in the assembling process of the deflection scanning apparatus, an optical sensor is used to measure the magnitude of the bending of the scanning line in the deflection scanning apparatus. Based on the measurement, the lens is mechanically rotated to adjust the bending of the scanning line, and then the lens or the like is fixed with an adhesive.

  In Patent Document 2, when the deflection scanning device is assembled to the color image forming apparatus main body, the inclination of the scanning line is measured using an optical sensor, and the deflection scanning device is mechanically tilted according to the inclination. The inclination of the scanning line is adjusted. After making the adjustment in this way, the deflection scanning device is incorporated and fixed in the color image forming apparatus main body.

Further, in Patent Document 3, an optical sensor is used to measure the inclination and bending of the scanning line in the deflection scanning device, and the bitmap image data is corrected so as to cancel them, and the corrected image data is converted into the corrected image data. It is described that an image is formed on the basis thereof. Since the method of Patent Document 3 electrically corrects a registration error by processing image data, mechanical adjustment and an adjustment process at the time of assembly become unnecessary. Therefore, there is an advantage that registration deviation can be dealt with at a lower cost than the methods described in Patent Document 1 and Patent Document 2 described above.
JP 2002-116394 A JP 2003-241131 A JP 2004-170755 A

  In the method described in Patent Document 3, a change is made to the adjacent upper or lower line at the bent portion of the scanning line. This line transfer position is fixed depending on the device and does not change within a page or every print job. Therefore, line transfer is always performed at the same main scanning pixel position, and the transfer line position is conspicuous and the image quality is lowered.

  Further, in order to make the transfer stripes at the line transfer position inconspicuous, pixels are added as image quality correction to the pixels before and after the transfer position. However, the addition of pixels concentrates the toner at the transfer position, and the dirt and partial deterioration of the drum are easily concentrated.

  An object of the present invention is to solve the above-mentioned problems of the prior art.

  It is an object of the present invention to provide an image forming apparatus and an image generation method in the apparatus that can solve the above problems by changing the line transfer position that has been fixed in the past.

  For a problem in which the transfer line position is conspicuous by always changing lines at the same main scanning pixel position, a jitter is added such that the transfer position moves by Δ (delta) pixels every n lines.

  In addition, there is a problem that the toner is concentrated at the transfer position by adding pixels, and the dirt and partial deterioration of the drum are easily concentrated. With respect to this, it is characterized in that jitter is added such that the transfer position moves by Δ (delta) pixels for each predetermined condition such as every n pages, every number of copies, every job, every predetermined number of sheets, etc.

  According to the present invention, the transfer position is diffused by adding jitter for moving the original transfer position for each line, and it is possible to improve the visual image quality. In addition, by adding jitter that moves the transfer position for each fixed condition such as page, number of copies, print job, and every predetermined number of sheets, it is possible to suppress toner concentration and to suppress concentration of dirt and partial deterioration. .

  Next, details of the present invention will be described in accordance with the description of the embodiments.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments do not limit the present invention according to the claims, and all combinations of features described in the present embodiments are essential to the solution means of the present invention. Not exclusively.

[Principle of registration deviation correction]
The principle of registration deviation correction will be described with reference to FIG.

  7A and 7B are diagrams for explaining the principle of registration deviation correction according to the embodiment of the present invention.

  FIG. 7A is a diagram for explaining the bending of a scanning line that causes a registration shift. In the figure, the horizontal axis indicates the main scanning direction of the scanning line, and the vertical axis indicates the sub-scanning direction. FIG. 7B shows a state in which bitmap data is sent to the printing unit while switching to line data corresponding to each scanning line in accordance with the bending of the scanning line. Here, the n line indicates the scanning line to be printed that should be printed. In FIG. 7B, the black portion shows line data sent to the printing unit when printing n lines. In this way, by switching the data line output to the printer engine in accordance with the bending of the scanning line, the electrostatic latent image generated on the image carrier such as the photosensitive drum can be obtained even if the exposure scanning is bent. Can be distorted.

[Principle of corrected image generation method in the present invention]
In the corrected image generation method according to the present embodiment, with respect to an image that is corrected before and after the transfer position, jitter is added such that the transfer position moves by Δ (delta) pixels every N lines around the original transfer position. In addition, with respect to what is corrected before and after the transfer position, a jitter is added so that the original transfer position moves by Δ pixels for each fixed condition such as every N pages, every number of copies, every job, every predetermined number of sheets, and the like.

  As a preferred example in Embodiment 1 of the present invention, a method for changing the transfer position by ± 1 pixel every four lines will be described.

  FIG. 1 is a diagram for explaining a method for changing the transfer position in this embodiment.

  Reference numeral 100 denotes a correction line for correcting the bending of the scanning line. When the scanning line scans from left to right, the image data becomes the same line data while the correction line 100 is traced from left to right and the upward movement due to the inclination is less than 1 dot. From the pixel next to the pixel 101 whose upward movement reaches one dot, the image data is the line one line before. Furthermore, the image data becomes a line one line before from the pixel next to the pixel 102 that has moved further to the right and moved upward due to the inclination to one dot. The first transfer pixel 101 obtained in this way is the Nth pixel. Therefore, the first transfer pixel of 8n + 0 [line], 8n + 1 [line], 8n + 2 [line], and 8n + 3 [line] in FIG. 2 is stored as the Nth pixel. Further, the 1st transfer pixel of 8n + 4 [line], 8n + 5 [line], 8n + 6 [line], and 8n + 7 [line] is stored as the (N + 1) th pixel added to the Nth transfer position N pixel obtained from the correction line of FIG. Similarly, the second pixel position is set to 8n + 0 [line], 8n + 1 [line], 8n + 2 [line], and 8n + 3 [line] at the transfer position M pixel obtained from the correction line of FIG. Further, 8n + 4 [line], 8n + 5 [line], 8n + 6 [line], and 8n + 7 [line] are recorded as the (M + 1) th pixel.

  FIG. 2 is a diagram showing a state in which line transfer is performed at the transfer pixel position in accordance with a correction line for correcting the curve of the scanning line in an image in which a line is drawn for each line. Reference numeral 200 denotes the first transfer pixel in the first line, and 204 denotes the second transfer pixel in the first line. Similarly, 201 indicates the first transfer pixel on the fifth line, and 205 indicates the second transfer pixel. Reference numeral 202 denotes a first transfer pixel on the ninth line, and 206 denotes a second transfer pixel. Reference numeral 203 denotes the first transfer pixel on the 13th line, and 207 denotes the second transfer pixel.

  FIG. 3 is a diagram showing a processing flow in creating a transfer image according to this embodiment. The process starts from the first pixel of the first line and proceeds with the N pixel, the M pixel, and the last pixel of the line. When the processing for the first line is completed, the process starts from the first pixel of the second line, and proceeds with N pixels, M pixels, and the last pixel of the line. In this way, the process proceeds to the last pixel of the last line. First, in the first line, the transfer line count value is set to 1 in S100. Next, since the transfer line count value is 1 in S101, the process proceeds to S102. Since it is still the first pixel in S102, the process proceeds to S104. Since it is not the last pixel of the line in S104, the process returns to S102 again. In this way, S102 and S104 are repeated up to the Nth pixel. When the process proceeds to the first transfer pixel 200 in FIG. 2, that is, the Nth pixel in the first line, the process proceeds to S103 because it is the Nth pixel in S102. In S103, line transfer is performed as shown in FIG. In the (N + 1) th pixel, the process proceeds to S104 in S102, and S102 and S104 are repeated until the Mth pixel is reached again. Similarly, in the Mth pixel, the process proceeds from S102 to S103, and the line is changed. Thereafter, S102 and S104 are repeated, and the process proceeds to the final pixel of the line. In the last pixel of the line, the process proceeds from S104 to S108. Since the transfer line count is 1, the process proceeds to S110 in S108, the transfer line count is incremented in S110, and the transfer line count value becomes 2. The process proceeds from S110 to S111, and since it is not the last line, the process returns from S111 to S101, and the process for the second line is started. The second line is omitted because there are no display pixels. Similarly, in the third line, the transfer line count is 3, and the process proceeds from S101 to S102 and the same processing as the first line is performed. The fourth line is also omitted because there are no display pixels. When the fifth line is reached, the transfer line count becomes 5, and therefore, from the first line to the fourth line, the process moves from S101 to S105. From line 1 to line 4, line transfer S103 is performed for N pixels and M pixels, but for line 5, line change S106 is performed for N + 1 pixels and M + 1 pixels as in S105. In the final pixel of the fifth line, the process proceeds from S107 to S108, and since the transfer line count is 5, the process proceeds from S108 to S110. Similarly, from the sixth line to the eighth line, the process proceeds from S101 to S105, and line transfer S106 is performed with N + 1 pixels and M + 1 pixels. In the eighth line, since the transfer line count is 8, the process proceeds from S108 to S109, and the transfer line count is returned to 1.

  In this way, an image as shown in FIG. 2 is obtained by alternately displaying lines for changing lines by N pixels and M pixels and lines for changing by N + 1 pixels and M + 1 pixels every four lines.

  As a preferred example in Embodiment 2 of the present invention, a method for changing the transfer position by ± 1 pixel for each page will be described.

  1 is the same as the first embodiment in that the Nth pixel and the Mth pixel are changed from the correction line for correcting the bending of the scanning line in FIG.

  FIG. 5 is a diagram illustrating a flow of the second embodiment. First, since the first page of printing is an odd page, the process proceeds from S201 to S202. Since it is the first pixel in S202, the process proceeds to S204. Since it is not the last pixel of the line in S204, the process returns to S202. In this way, S202 and S204 are repeated up to the Nth pixel. In the Nth pixel, the process proceeds from S202 to S203, and the line is changed in S203. Similarly, S202 and S204 are repeated from the (N + 1) th pixel to the Mth pixel, and from S202 to S203 up to the Mth pixel, line transfer is performed in S203. Further, S202 and S204 are repeated from the (M + 1) th pixel to the last pixel of the line, and the process proceeds from S204 to S211 at the last pixel of the line. Since the first line is not the final line, the process returns from S211 to S201 and the processing of the second line is started. Similarly to the first line, the second and subsequent lines perform line transfer processing in S203 only for the Nth and Mth pixels. In this way, processing is performed up to the final line.

  Next, the processing for the second page proceeds from S201 to S205, and S205 to S207 are repeated up to the (N + 1) th pixel. In the (N + 1) th pixel, the process proceeds from S205 to S206, and the line is changed in S206. Similarly, the process from S205 to S207 is repeated up to the M + 1 pixel, and the process proceeds from S205 to S206 at the M + 1 pixel, and the line is changed at S206. In this way, line transfer is performed only for the N + 1 pixel and the M + 1 pixel from the second line to the final line.

  Since the third page is an odd page, the processing is the same as the first page. In this way, line switching is performed at the Nth and Mth pixels for odd pages, and line switching is performed at the (N + 1) th pixel and M + 1th pixel for even pages, thereby switching between odd and even pages as shown in FIG. Images with different line positions can be obtained. FIG. 6 shows an odd page and an even page to which correction pixels are added. Reference numeral 501 denotes the first line transfer position of the odd page, which designates the center of the correction pixel. Reference numeral 502 denotes the first line transfer position on the even page, which indicates the center of the correction pixel. When the corrected pixel center line 501 of the odd page and the corrected pixel center line 502 of the even page are extended, it can be seen that there is a shift 503 between them. In this way, the concentration of correction pixels is dispersed to reduce toner concentration, drum contamination, and partial deterioration.

It is a figure which shows the transfer position in Example 1 and Example 2. FIG. It is a figure which shows the transfer position for every line in Example 1. FIG. It is a flowchart explaining the change of the transfer position in Example 1. FIG. It is a figure which shows the transfer position for every page in Example 2. FIG. It is a flowchart explaining the change of the transfer position in Example 2. FIG. It is a figure explaining after correction pixel addition in Example 2. FIG. It is a figure for demonstrating the registration shift which concerns on embodiment of this invention, and its correction | amendment.

Claims (6)

An image forming apparatus that forms a printed image by correcting the bending of a scanning line at the time of image formation with image data,
A plurality of main scanning pixel position information indicating a main scanning pixel position for switching a line of image data in accordance with the bending of the scanning line;
Storage means for storing a plurality of sets of main scanning pixel position information for switching the lines;
Switching means for switching a plurality of main scanning pixel position information for switching lines stored for each condition;
The image data line switching means for switching the line of the image data according to the switched line switching main scanning pixel position information,
An image forming apparatus for forming an image in which a curve of a scanning line is corrected.   2. The image forming apparatus according to claim 1, wherein a condition for switching the plurality of pieces of main scanning pixel position information is one or more lines.   The image forming apparatus according to claim 1, wherein a condition for switching the plurality of pieces of main scanning pixel position information is one or more pages.   The image forming apparatus according to claim 1, wherein a condition for switching the plurality of pieces of main scanning pixel position information is every one or more print copies.   The image forming apparatus according to claim 1, wherein a condition for switching the plurality of pieces of main scanning pixel position information is one or more print jobs.   The image forming apparatus according to claim 1, wherein a condition for switching the plurality of pieces of main scanning pixel position information is one or more printed sheets.

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