JP2006113306A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of performing color matching adjustment with stable accuracy, and an image forming method. <P>SOLUTION: In the case of performing the color matching adjustment that positions where respective color images are formed are adjusted so as not to cause color slurring on a multicolor image, the image forming apparatus forms a yellow base image on an intermediate transfer belt (medium) 4, and respective KCM color test images LK1, LK2,..., LC1, LC2,..., LM1, LM2,... are formed superimposed on the foundation image. Furthermore, Y color test images LY1, LY2,... are formed directly on the intermediate transfer belt 4. When the respective color test images are optically detected, reflected light from a part where the color test image is not formed becomes reflected light from the base image and its intensity gets stable, so that the color test image is accurately detected and the color matching adjustment is performed with the stable accuracy. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus and an image forming method for forming a multicolor image by superimposing color images of respective colors and performing color matching adjustment for correcting a color shift of the multicolor image.

  An image forming apparatus that forms a multicolor image decomposes input data into color components of black (K), cyan (C), magenta (M), and yellow (Y) and performs image processing. Image data for each component is created, and a color image of each color based on the respective image data is superimposed to form a multicolor image. When forming the multicolor image, if the positions where the color images are superimposed are shifted, the image quality deteriorates due to the color shift occurring in the formed multicolor image. In particular, in an image forming apparatus called a tandem type in which an image forming unit is provided for each color component in order to improve the formation speed of a multicolor image, each color image is formed separately in each image forming unit, and is recorded on a recording medium or A multicolor image is formed by sequentially superimposing each color image on a transfer medium for transferring a multicolor image to a recording medium. This is a big problem.

  Therefore, an image forming apparatus that forms a multicolor image performs color matching adjustment for correcting a color shift of the multicolor image so that the color images can be accurately superimposed. In the conventional color matching adjustment, a deviation of the formation position of another color image from the formation position of a reference color image is detected using an optical detector, and a correction amount is determined based on the detection result, and each color image is determined. The timing for forming each color image is adjusted in accordance with the determined correction amount so that the formation positions of the images match. In such a conventional technique, in order to detect a shift in the formation position of each color image, each color image is formed at a predetermined timing, and a distance between each formed color image is detected, or each color image is superimposed. The overlap state or density of the multi-colored images is measured.

  For example, in Patent Document 1, a position shift of each color image is detected by measuring a distance between each position where each color image is formed, and each color image is formed based on the detected position shift. A technique for correcting the position is disclosed. In this technique, the distance between a reference color image and another color image is detected by a detector, the amount of positional deviation of each color image is determined based on the detected distance, and the position where each color image is formed The deviation is corrected.

In Patent Document 2, the density of a multicolor image in which each color image is superimposed is measured, and the position at which each color image is formed so that the density of the multicolor image becomes a density in a state where each color image is accurately superimposed. A technique for correcting the shift is disclosed. In this technique, in order to improve the correction accuracy, a plurality of line-shaped images having the same shape are formed, and the density of the line-shaped images formed in multiple colors is detected by a detector, thereby overlapping each color image. Seeking. Then, the state where the density of the detected line falls within a predetermined density range is a state where each color image accurately overlaps, and the position where each color image is formed is controlled so that each color image accurately overlaps. .
JP-A-10-213940 JP 2000-81744 A JP 2001-312116 A JP 4-110866 A

  In the techniques disclosed in Patent Document 1 and Patent Document 2, an image for color matching adjustment is formed on a belt such as a conveyance belt or an intermediate transfer belt, and the image formed on the belt is irradiated with light. The position or density of the image is detected based on the intensity of the reflected light from the image. Therefore, in order to detect the position or density of an image with high accuracy, it is desirable that the intensity of reflected light is stable at a portion on the belt where no image is formed. However, in general, the surface of the belt is not in a smooth state, and dirt, unevenness, or scratches are irregularly generated, and the intensity of reflected light from the surface of the belt varies depending on the surface state. Therefore, the conventional technique cannot detect the position or density of the image formed on the belt with a certain degree of accuracy, and therefore cannot accurately adjust the color matching of each color image. Further, since the surface state of the belt changes as the image forming apparatus is used, there is a problem that the accuracy of color matching adjustment varies as the image forming apparatus is used.

  The present invention has been made in view of such circumstances, and the object of the present invention is to stabilize the intensity of reflected light from a portion where an image on the belt is not formed, with a stable accuracy. An object of the present invention is to provide an image forming apparatus and an image forming method capable of performing color matching adjustment.

  Another object of the present invention is to provide an image forming apparatus and an image forming method capable of suppressing deterioration in image quality of a multicolor image due to occurrence of color misregistration.

  Another object of the present invention is to provide an image forming apparatus and an image forming method capable of performing color matching adjustment in a short time.

  Another object of the present invention is to provide an image forming apparatus and an image forming method capable of suppressing the influence of operation unevenness or disturbance of the image forming apparatus in color matching adjustment.

  An image forming apparatus according to the present invention includes a plurality of image forming units that form color images of different colors on a moving medium, and a test image that causes each of the plurality of image forming units to form a color test image on the medium. Forming means, means for irradiating each color test image with light, means for detecting reflected light of the light irradiated to each color test image by the means, and the distance between the color test images based on the detection result by the means An image forming apparatus comprising: a determining unit; and a unit that adjusts a position of a color image based on a distance between the color test images calculated by the unit. The test image forming unit includes a medium on the image forming unit. It is characterized by having means for forming a base image in which the predetermined area is colored with one color, and means for forming a color test image on the base image on another image forming means.

  An image forming apparatus according to the present invention includes a plurality of image forming units that form color images of different colors on a moving medium, and a test image that causes each of the plurality of image forming units to form a color test image on the medium. Forming means, irradiating means for irradiating each color test image with light, means for detecting reflected light of the light irradiated to each color test image by the irradiating means, and based on the detection result by each means, between each color test image In the image forming apparatus, comprising: a distance measuring unit that measures the distance; and a unit that adjusts the position of the color image based on the distance between the color test images measured by the distance measuring unit. Means for forming a background image in which a predetermined area on the medium is colored with one color, and a plurality of other image forming means for forming each color test image on the background image; Serial to an image forming means, characterized by having a means for forming a color test image on a portion other than the predetermined region on the medium.

  In the image forming apparatus according to the present invention, the distance measuring unit is configured to measure a distance from a specific color test image to each of a plurality of other color test images, and the color of the base image is The color is different from that of the specific color test image.

  The image forming apparatus according to the present invention is characterized in that the color of the base image is a color having the lowest visibility among the colors of the color images formed by the plurality of image forming units.

  In the image forming apparatus according to the present invention, the color of the base image is the color having the highest reflectance of the light irradiated by the irradiation unit among the colors of the color images formed by the plurality of image forming units. It is characterized by that.

  The image forming apparatus according to the present invention is characterized in that the color of the base image is yellow.

  In the image forming apparatus according to the aspect of the invention, the light emitted from the irradiation unit is reflected from the color of the base image among the wavelength components reflected from the colors of the color images formed by the plurality of image forming units. It is characterized by including the largest number of wavelength components.

  In the image forming apparatus according to the present invention, the plurality of image forming units are arranged side by side along a moving direction of a moving medium, and the one image forming unit is the one among the plurality of image forming units. , And is arranged at a position on the most upstream side along the moving direction of the moving medium.

  In the image forming apparatus according to the present invention, the color test image is an image in which a plurality of line images having a predetermined length are arranged in a moving direction of the medium at a predetermined interval.

  An image forming method according to the present invention includes a plurality of image forming units that form color images of different colors on a moving medium, and a test image in which a color test image is formed on the medium by each of the plurality of image forming units. Forming means, means for irradiating each color test image with light, means for detecting reflected light of the light irradiated to each color test image by the means, and the distance between the color test images based on the detection result by the means In the method for forming a color test image by an image forming apparatus comprising means for obtaining and means for adjusting the position of the color image based on the distance between the color test images obtained by the means, the test image forming means comprises: One image forming unit forms a base image in which a predetermined area on the medium is colored with one color, and another image forming unit forms a color test image on the base image.

  An image forming method according to the present invention includes a plurality of image forming units that form color images of different colors on a moving medium, and a test image in which a color test image is formed on the medium by each of the plurality of image forming units. Forming means, means for irradiating each color test image with light, means for detecting reflected light of the light irradiated to each color test image by the means, and the distance between the color test images based on the detection result by the means In the method for forming a color test image by an image forming apparatus comprising means for obtaining and means for adjusting the position of the color image based on the distance between the color test images obtained by the means, the test image forming means comprises: One image forming unit forms a base image in which a predetermined area on the medium is colored with one color, and another image forming unit forms each color test image on the base image, thereby forming the one image. The stage, characterized in that to form a color test image on the portion other than the predetermined area on the medium.

  In the present invention, an image forming apparatus including a plurality of image forming units that form color images of different colors on a moving medium such as recording paper or a belt forms a color test image of each color on the medium. When adjusting the position of the color image formed on the medium by each image forming unit so that the color images overlap each other based on the distance between the color test images on the medium, A color test image is formed on the base image.

  In the present invention, an image forming apparatus including a plurality of image forming units that form color images of different colors on a moving medium such as recording paper or a belt forms a color test image of each color on the medium. Based on the distance between the color test images on the medium, when adjusting the position of the color image formed on the medium by each image forming unit so that the color images overlap each other, a predetermined area on the medium is colored with one color. The background image thus formed is formed on the medium, a color test image of another color is formed on the background image, and the color test image of the color of the background image is formed in a portion other than the predetermined area on the medium.

  In the present invention, the color of the background image is a color different from the color of the color test image that serves as a reference position when the distance between the color test images is measured.

  In the present invention, the color of the base image is the color with the lowest visibility among the colors of the color images formed by the plurality of image forming units.

  Further, in the present invention, the color of the background image is the color having the highest reflectance of the light irradiated when the color test image is optically detected among the colors of the color image formed by the plurality of image forming units. is there.

  In the present invention, the color of the background image is yellow among cyan, magenta, yellow, and black used by the image forming apparatus.

  In the present invention, the light emitted when optically detecting the color test image contains the largest number of wavelength components reflected from the color of the background image among the wavelength components reflected from the respective colors.

  In the present invention, the plurality of image forming means are arranged side by side along the moving direction of the medium, and the image forming means for forming the base image is arranged at the most upstream position.

  In the present invention, the color test image is an image in which a plurality of line images are arranged at a predetermined interval.

  In the present invention, the color test image on the medium is not formed by forming a color test image of a color different from the background image on the background image formed on the medium such as a belt. Since the reflected light from the light becomes reflected light from the base image and the intensity is stabilized, the color test image can be detected with high accuracy.

  In the present invention, a color test image of another color is formed on a background image of one color formed on a medium such as a belt, so that reflection from a portion on the medium where the color test image is not formed is performed. Since the light is reflected from the base image and the intensity is stable, the color test image can be detected with high accuracy. Accordingly, it is possible to accurately adjust the color matching of each color image in which a color test image is formed on the base image. In addition, since the background image is formed every time color adjustment is performed, the surface state does not change with the use of the image forming apparatus, and color adjustment of each color image can be performed with stable accuracy at all times.

  In the present invention, the distance between the color test images is measured by forming a ground image in a color different from the color of the color test image that is a reference for measuring the distance between the color test images. Therefore, the distance between the color test images can be measured with high accuracy.

  In the present invention, since the color test image of the color of the background image is formed directly on the medium, the accuracy of the color matching adjustment of this color is worse than that of other colors. By making the color with the lowest visibility among the colors handled by the image forming device, it is possible to minimize deterioration in image quality even if the color shift of one color is larger than other colors in a multicolor image. it can.

  In the present invention, the color of the ground image is set to the color having the highest reflectance of the light irradiated when the color test image is optically detected, so that the color test of the ground image and other colors is performed. Since the difference in detection intensity of reflected light from the image becomes large, the color test image can be detected with high accuracy.

  In the present invention, the background image is yellow, and has the lowest visibility and the highest reflectance of white light among cyan, magenta, yellow, and black usually used in image forming apparatuses. Further, it is possible to minimize the deterioration of the image quality due to the color shift and to detect the color test image with high accuracy.

  In the present invention, the light emitted when optically detecting the color test image contains the largest amount of wavelength component reflected from the color of the background image, as compared to other colors. The difference in detection intensity of reflected light between the image and the color test image of another color becomes large, and the color test image can be detected with high accuracy.

  In the present invention, among the plurality of image forming units arranged side by side in the moving direction of the medium, the image forming unit for forming the base image is arranged at the most upstream position. A test image for the present invention can be formed in the shortest time by forming another color test image on the base image formed in accordance with the movement of.

  Further, in the present invention, a color test image in which a plurality of line images of a predetermined length are arranged at predetermined intervals is formed, a plurality of distances between corresponding line images between the respective colors are measured, and a plurality of measured distances are measured. By obtaining the distance between the color test images, it is possible to prevent the measurement accuracy of the distance between the color test images from being deteriorated due to the influence of disturbances such as uneven operation of the image forming apparatus such as slack of the medium or vibration. The present invention has an excellent effect.

Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof.
FIG. 1 is a cross-sectional view showing an internal configuration example of an image forming apparatus of the present invention. The image forming apparatus 1 forms an image on an intermediate transfer belt 4 that is a moving medium according to the present invention, and forms an image by transferring the image on the intermediate transfer belt 4 to a recording sheet. This is an image forming apparatus. The image forming apparatus 1 is configured to form a multicolor image using toner of each color of black (K), cyan (C), magenta (M), and yellow (Y).

  The image forming apparatus 1 includes photosensitive drums 11a, 11b, 11c, and 11d, developing units 12a, 12b, 12c, and 12d, chargers 13a, 13b, 13c, and 13d, and cleaner units 14a, 14b, 14c, and 14d. . Symbols a, b, c, and d attached to the respective symbols correspond to K, C, M, and Y, respectively. The photosensitive drum, the developing unit, the charger, and the cleaner unit are configured as one set for each color, and four sets corresponding to K, C, M, and Y are arranged in a straight line. A set of photosensitive drums, developing units, chargers, and cleaner units for each color corresponds to the image forming means according to the present invention. Hereinafter, the members provided for each color are collectively referred to as the photosensitive drum 11, the developing unit 12, the charger 13, and the cleaner unit 14 unless a member corresponding to a specific color is designated.

  The image forming apparatus 1 includes an exposure unit 3 that emits laser light below the photosensitive drum 11 to generate an electrostatic latent image on the photosensitive drum 11. The exposure unit 3 includes a polygon mirror 31, and includes a reflection mirror 32a that reflects a laser beam emitted from a laser irradiation unit (not shown) and scanned by the rotation of the polygon mirror 31 to irradiate the photosensitive drum 11a. . Similarly, the exposure unit 3 includes reflection mirrors 32b and 33b, 32c and 33c, 32d and 33d corresponding to the photosensitive drums 11b, 11c and 11d.

  The charger 13 is configured to uniformly charge the surface of the photosensitive drum 11 to a predetermined potential. As the charger 13, a charger type that does not contact the photosensitive drum 11 is used in addition to a roller type or a brush type that contacts the photosensitive drum 11. The developing unit 12 stores toner of each color, and supplies the toner of each color to the electrostatic latent image formed on the surface of the photosensitive drum 11 by the exposure unit 3 to visualize the toner image. The cleaner unit 14 collects and removes toner remaining on the surface of the photosensitive drum 11 after the image is transferred.

  The image forming apparatus 1 further includes an intermediate transfer belt 4 that transfers the toner image on the photosensitive drum 11 above the photosensitive drum 11. The intermediate transfer belt 4 is formed in an endless shape using a film having a thickness of about 100 μm to 150 μm. The intermediate transfer belt 4 is stretched between a belt driving roller 41 and a driven roller 42, and is configured to rotate in the direction of the arrow shown in the drawing by the driving force of the belt driving roller 41. The intermediate transfer belt 4 is arranged so that the surface of the photosensitive drum 11 is in contact with the surface of the intermediate transfer belt 4, and primary transfer rollers 15a, 15b, 15c, and 15d that face the photosensitive drum 11 with the intermediate transfer belt 4 interposed therebetween are provided. Yes. Hereinafter, the primary transfer rollers 15a, 15b, 15c, and 15d corresponding to the respective colors are collectively referred to as a primary transfer roller 15. The primary transfer roller 15 is in contact with the back side of the intermediate transfer belt 4, and a voltage for transferring the toner image on the photosensitive drum 11 to the intermediate transfer belt 4, that is, a high voltage having a polarity opposite to the charging polarity of the toner. Is applied. The primary transfer roller 15 applies a high voltage uniformly to the intermediate transfer belt 4 to transfer the toner image on the photosensitive drum 11 to the intermediate transfer roller 11.

  The image forming apparatus 1 also includes a paper feed tray 7 that stores recording paper. Further, the image forming apparatus 1 includes a secondary transfer roller 43 that faces the belt driving roller 41 with the intermediate transfer belt 4 interposed therebetween. The recording paper stored in the paper feed tray 7 is conveyed between the intermediate transfer belt 4 and the secondary transfer roller 43 through a conveyance path indicated by a one-dot chain line in the drawing. As described above, each color toner image formed on the photosensitive drum 11 is sequentially transferred onto the intermediate transfer belt 4, and an image expressed by the multicolor toner image is formed on the intermediate transfer belt 4. The multi-color toner image on the intermediate transfer belt 4 moves according to the rotation of the intermediate transfer belt 4 and is transferred onto the recording paper conveyed between the intermediate transfer belt 4 and the secondary transfer roller 43. At this time, the intermediate transfer belt 4 and the secondary transfer roller 43 are pressed against each other with the recording paper interposed therebetween, and the secondary transfer roller 43 has a voltage for transferring the multicolor toner image on the intermediate transfer belt 4 onto the recording paper. That is, a high voltage having a polarity opposite to the charging polarity of the toner is applied. Thus, an image is formed on the recording paper by transferring the multicolor toner image onto the recording paper. The recording paper on which the image is formed is discharged to the outside of the image forming apparatus 1 through the subsequent conveyance path. The image forming apparatus 1 also includes a cleaning unit 44 that removes toner remaining on the intermediate transfer belt 4.

  With the configuration as described above, the image forming apparatus 1 transfers the toner images of the respective colors from the photosensitive drum 11 onto the intermediate transfer belt 4 in order, so that the image forming apparatus 1 has a large number of images on the intermediate transfer belt 4 that is a moving medium according to the present invention. A color image is formed, and the multicolor image on the intermediate transfer belt 4 is further transferred onto the recording paper, thereby forming a multicolor image recorded on the recording paper. The intermediate transfer belt 4 moves in the direction of the arrow in FIG. 1, and the photosensitive drums 11d, 11c, 11b, and 11a contact the intermediate transfer belt 4 in order, so that the toner images of the respective colors are Y, M, C, and K. Are formed in this order.

  In the process of forming a multicolor image on the recording paper as described above, each color image is formed on the intermediate transfer belt 4 at the timing at which each color toner image is transferred from the photosensitive drum 11 onto the intermediate transfer belt 4. The position is determined. When the positions of the respective color images transferred onto the intermediate transfer belt 4 are deviated from each other, a multicolor image in which color misregistration has occurred is formed on the recording paper. The image forming apparatus 1 includes a control unit 5 that controls the timing at which each color toner image is transferred onto the intermediate transfer belt 4. The controller 5 is configured to control the transfer timing so that the color images overlap on the intermediate transfer belt 4. However, each color image formed on the intermediate transfer belt 4 is caused by various causes such as attachment error of the photosensitive drum 11, eccentricity, rotation unevenness, expansion / contraction due to temperature / humidity change of the intermediate transfer belt 4, and movement unevenness. The positions are shifted from each other and color shift occurs.

  The image forming apparatus 1 of the present invention forms on the intermediate transfer belt 4 which is a medium according to the present invention a test image composed of color test images of each color such that the images of the respective colors are separated from each other by a predetermined distance. The actual distance between each color test image included is measured, and color matching adjustment processing is performed to adjust the timing at which each color image is transferred to the recording paper. The image forming apparatus 1 includes a detection sensor 21 for detecting a test image formed on the intermediate transfer belt 4 and a temperature / humidity sensor 22 for detecting temperature and humidity in the image forming apparatus 1.

  The detection sensor 21 is a position where the intermediate transfer belt 4 has passed through the photosensitive drum 11a for the purpose of detecting a test image formed on the intermediate transfer belt 4, and the secondary transfer roller 43. It is provided in the position before reaching. The temperature / humidity sensor 22 is installed in a portion where a sudden temperature or humidity change does not occur, and detects the temperature / humidity in the image forming apparatus.

  FIG. 2 is a schematic diagram illustrating a configuration example of the detection sensor 21. The detection sensor 21 includes an irradiating unit (irradiating unit) 24 that irradiates light onto the test image formed on the intermediate transfer belt 4. A detection unit 25 that detects reflected light is provided at a position where it can be detected. In this invention, the irradiation part 24 becomes a structure which irradiates white light. The test image can be detected based on the intensity change of the reflected light detected by the detection unit 25. Note that the detection sensor 21 may include a detection unit that detects irregular reflection light instead of regular reflection light from the test image, and a detection unit that detects regular reflection light and a detection unit that detects irregular reflection light. May be provided.

  FIG. 3 is a block diagram illustrating an internal configuration example of the control unit 5. The control unit 5 includes a CPU 51 that performs calculation. The CPU 51 is connected to a RAM 52 that stores temporary information associated with the calculation and a ROM 53 that stores a control program for controlling the image forming apparatus. . The CPU 51 performs processing necessary for the image forming apparatus in accordance with a control program stored in the ROM 53. The CPU 51 is connected to a clock unit 55 for measuring time, and the CPU 51 performs various processes based on the time measured by the clock unit 55. The CPU 51 is connected to an operation unit 56 that is configured by a touch panel, a numeric keypad, or the like and that receives instructions from the user.

  Further, the detection sensor 21 and the temperature / humidity sensor 22 are connected to the CPU 51. The CPU 51 receives detection results from the detection sensor 21 and the temperature / humidity sensor 22 and performs processing based on the input detection results. The CPU 51 is connected to a driving unit 50 such as a motor for driving the belt driving roller 41. The CPU 51 moves the intermediate transfer belt 4 by controlling the operation of the drive unit 50. Further, the exposure unit 3 is connected to the CPU 51. The CPU 51 controls the timing at which each color image is formed on the intermediate transfer belt 4 by controlling the timing at which the exposure unit 3 forms an electrostatic latent image on the photosensitive drum 11. Further, the CPU 51 is connected to an adjustment amount storage unit 54 that stores an adjustment amount at the timing when each color image is formed.

  The image forming apparatus 1 according to the present invention having the above-described configuration allows the intermediate transfer belt 4 to be moved by the photosensitive drum 11d positioned on the most upstream side of the moving intermediate transfer belt 4 when a test image for color matching adjustment is formed. A yellow base image is formed in a predetermined area above. Next, the image forming apparatus 1 forms a black, cyan, and magenta color test image on the yellow base image by the photosensitive drums 11a, 11b, and 11c, and intermediately transfers the yellow color test image by the photosensitive drum 11d. It is formed on a portion other than the base image on the belt 4.

  FIG. 4 is a schematic diagram illustrating an example of a test image formed on the intermediate transfer belt 4 by the image forming apparatus 1. The arrows in the figure indicate the moving direction of the intermediate transfer belt 4. Each color test image includes a plurality of line images having a predetermined length substantially orthogonal to the moving direction of the intermediate transfer belt 4 and arranged in the moving direction of the intermediate transfer belt 4 at predetermined intervals. Here, let N be the number of line images included in each color test image. K, C, and M are superimposed on the yellow background image, K color test image composed of black line images LK1, LK2,..., LKN, C color composed of cyan line images LC1, LC2,. An M color test image including a color test image and magenta line images LM1, LM2,. Further, following the M color test image, a Y color test image composed of yellow line images LY1, LY2,..., LYN is formed on the intermediate transfer belt 4. The sub-scanning direction when forming an image on the recording paper is opposite to the moving direction of the intermediate transfer belt 4. The direction orthogonal to the moving direction of the intermediate transfer belt 4 is the main scanning direction when an image is formed on the recording paper.

  In order to accurately detect each line image constituting the color test image by the detection sensor 21, it is desirable that the width and interval of the line image be larger than the diameter of the detection spot of the detection sensor 21. For example, when the diameter of the detection spot is 3 mm and the resolution of the image forming apparatus 1 is 600 dpi, the size of one pixel is about 42.3 μm and the width of 100 pixels is about 4.2 mm. A line image having a pixel width is formed at intervals of 100 pixels. The CPU 51 is configured to form a color test image corresponding to at least one rotation of the photosensitive drum 11 in order to detect a color shift caused by eccentricity or rotation unevenness of the photosensitive drum 11.

  Next, a detection result obtained by detecting the test image with the detection sensor 21 will be described. FIG. 5 is a characteristic diagram showing an example of a detection result by the detection sensor 21 when a test image is directly formed on the surface of the intermediate transfer belt 4. The vertical axis in the figure indicates the detected intensity of the reflected light, and the horizontal axis indicates time. Further, K, C, M, and Y in the figure indicate detection results corresponding to the color test images of K, C, M, and Y, respectively. In FIG. 5, the detected intensity of the reflected light from the surface of the intermediate transfer belt 4 is indicated by a wavy line. Since the surface state of the intermediate transfer belt 4 is unstable due to dirt or the like, the detected intensity from the surface of the intermediate transfer belt 4 fluctuates irregularly. Since each KCM toner has a light reflectance lower than that of the surface of the intermediate transfer belt 4, as shown in FIG. 5A, the detected intensity of the reflected light from each color test image of K, C, M is It is obtained with a value that is less than the detected intensity from the surface of the intermediate transfer belt 4. Since the detection intensity from the surface of the intermediate transfer belt 4 is unstable, the amount of decrease in detection intensity corresponding to each color test image of KCM also becomes unstable.

  On the other hand, since the Y toner has a higher reflectance of white light than the surface of the intermediate transfer belt 4, the detected intensity of reflected light from the Y color test image is intermediate as shown in FIG. It is obtained with a value increased from the detected intensity from the surface of the transfer belt 4. In FIG. 5, the detected intensity from the yellow image is indicated by a one-dot chain line. Since the surface state of an image formed with yellow toner is stable unlike the intermediate transfer belt 4, the detected intensity of yellow is substantially constant and stable.

  FIG. 6 is a characteristic diagram illustrating an example of a test image detection result according to the present invention. Since the KCM color test images are formed on the yellow base image, the detection intensity from the KCM color test images is decreased from the stable yellow detection intensity by a substantially constant reduction amount corresponding to each color. Each color test image is detected. By forming each KCM color test image on the yellow background image formed on the intermediate transfer belt 4 in this way, the reflection of light from the background of the color test image is stabilized, so that the KCM color test image is displayed. It can be detected with high accuracy. Further, the white light emitted from the irradiation unit 24 contains the most wavelength component reflected from yellow in KCMY, and yellow is the color with the highest reflectance of white light, so that the background of the color test image The difference in detection intensity of reflected light between the yellow background image and the KCM color test image is large, and the KCM color test image can be detected with high accuracy. Therefore, it is possible to accurately adjust the color matching of each color image of KCM. Further, since the yellow background image is formed every time color adjustment is performed, the surface state does not change with the use of the image forming apparatus 1, and the color adjustment of each color image of the KCM is always performed with stable accuracy. It can be carried out.

  Further, since the Y color test image is formed directly on the intermediate transfer belt 4, the detection result of the Y color test image is the same as the detection result shown in FIG. Therefore, the detection accuracy of the Y color test image is about the same as the conventional one, and the accuracy of color matching adjustment of the Y color image is worse than the accuracy of color matching adjustment of each color image of KCM. However, since yellow is the color with the lowest visibility among KCMY, even if the color shift of the Y color image is larger than that of the KCM color image in the multicolor image, the deterioration of the image quality is minimized. Can be suppressed.

  The image forming means for forming a Y color image including the photosensitive drum 11d is positioned on the most upstream side with respect to the moving direction of the intermediate transfer belt 4 among the image forming means for forming the KCMY color image. Is arranged. A yellow base image is formed on the intermediate transfer belt 4 by the image forming unit on the most upstream side, and each color test image of KCM can be formed on the base image by a further downstream image forming unit. The test image for the present invention can be formed in the shortest time.

  Next, a procedure of processing performed by the image forming apparatus 1 of the present invention will be described. The image forming apparatus 1 according to the present invention performs color matching adjustment processing when the power is turned on, after a predetermined time has elapsed since the power is turned on, or when a predetermined number of images are formed. Also, when the temperature / humidity sensor 22 detects a predetermined temperature / humidity, or when the temperature / humidity sensor 22 detects a change in temperature / humidity greater than a predetermined value, the image forming apparatus 1 performs the color matching adjustment process. . When a noticeable color misregistration is confirmed by the user or during maintenance, the image forming apparatus performs color matching adjustment processing by accepting an instruction for color matching adjustment by the user or a service person at the operation unit 56.

  FIG. 7 is a flowchart illustrating a procedure of color matching adjustment performed by the image forming apparatus 1 of the present invention. The CPU 51 performs the following color matching adjustment process according to the control program stored in the ROM 53. In this way, the CPU 51 functions as a test image forming unit and an adjusting unit according to the present invention.

  The CPU 51 controls the exposure unit 3 to form, on the intermediate transfer belt 4, KCMY color test images including a plurality of line images substantially orthogonal to the moving direction of the intermediate transfer belt 4 as shown in FIG. 4. (S1). At this time, a yellow base image is formed on the intermediate transfer belt 4 by forming an image alone on the photosensitive drum 11d. At the timing when the edge of the yellow background image passes immediately above the photosensitive drum 11a, the formation of the background image is stopped, and the KCMY color test images are formed on the photosensitive drums 11a, 11b, 11c, and 11d substantially simultaneously. When forming color images on the intermediate transfer belt 4, each color image is formed in the order of YMCK. By simultaneously forming each color test image, the distance between the photosensitive drums 11 from the relative position where each color image is formed. Each color test image is formed at a position on the intermediate transfer belt 4 that is separated by a distance corresponding to each color determined by the distance.

  The test image formed on the intermediate transfer belt 4 moves as the intermediate transfer belt 4 moves. The irradiation unit 24 of the detection sensor 21 irradiates the test image on the intermediate transfer belt 4 with light, and the detection unit 25 detects reflected light of the irradiated light. CPU51 receives the detection result which detection sensor 21 detected each line picture (S2). Next, the CPU 51 performs an inter-image distance calculation process for calculating the distance between the KCMY color test images formed on the intermediate transfer belt 4 (S3).

  FIG. 8 is a flowchart showing the procedure of the subroutine of the inter-image distance calculation process in step S3. FIG. 9 shows each color test image composed of a plurality of line images substantially orthogonal to the moving direction of the intermediate transfer belt 4. It is the schematic diagram which showed typically the method of calculating the distance between. The subroutine of the inter-image distance calculation process in step S3 will be described below with reference to FIGS.

  The CPU 51 specifies the position of each line image included in each color test image of KCMY based on the detection results as shown in FIGS. 6 and 5B received from the detection sensor 21 (S21). Specifically, the CPU 51 determines whether each line image is based on the time at which a portion such as the center position of the detected intensity falling, rising, or decreasing portion shown in FIG. 6 is detected and the moving speed of the intermediate transfer belt 4. The relative position on the intermediate transfer belt 4 is calculated.

  Next, based on the relative position of each line image, the CPU 51 calculates the distance between the line images corresponding to each other included in each color test image (S22). Specifically, as shown in FIG. 9, the CPU 51 calculates a distance P (KC) 1 between the first line image LK1 of K and the first line image LC1 of C, and similarly between KCs. The distances P (KC) 2,..., P (KC) N between the other line images are calculated. Similarly, the CPU 51 calculates the distance between the K line image and the M line image and the distance between the K line image and the Y line image.

  Next, the CPU 51 averages the distances between the N line images of the K color test image and each of the CMY color test images, so that the color test image of the K color test image and the CMY color test images is obtained. The distance between the images is calculated (S23), the inter-image distance calculation subroutine in step S3 is terminated, and the process returns to the main routine.

  Next, the CPU 51 calculates the amount of deviation in the sub-scanning direction when recording an image on a recording sheet using the intermediate transfer belt 4 based on the distance between the color test images calculated in the subroutine of step S3 described above. (S4). For example, when the distance between the K color test image and the C color test image is longer than the setting distance determined by the design distance between the photosensitive drums 11a and 11b of the respective colors, When each color image is formed on the intermediate transfer belt 4 at a predetermined timing so that the color images overlap based on the set distance, and further transferred onto the recording paper, the K color image is C Is formed on the intermediate transfer belt 4 at a timing earlier than the timing at which the color image overlaps, and color misregistration occurs on the recording paper. In this way, by comparing the setting distance determined by the design distance between the photosensitive drums 11 and the distance between the color test images, the CPU 51 can record the CMY data when recording the image on the recording paper. The amount of deviation of each color image from the K color image in the sub-scanning direction is calculated.

  Next, the CPU 51 controls the exposure unit 3 to form on the intermediate transfer belt 4 each KCMY color test image composed of a plurality of line images obliquely intersecting the moving direction of the intermediate transfer belt 4 (S5). ). FIG. 10 is a schematic diagram schematically illustrating a method for calculating the distance between color test images composed of a plurality of line images obliquely intersecting with the moving direction of the intermediate transfer belt 4. Each color test image is composed of a plurality of line images having a predetermined length obliquely intersecting with the moving direction of the intermediate transfer belt 4 and arranged in the moving direction of the intermediate transfer belt 4 at predetermined intervals. Here, the number of line images included in each color test image is N, but the number may be different from the number of orthogonal line images formed in step S1. Overlapping the yellow background image, K color test image consisting of black line images SK1, SK2,..., SKN, C color test image consisting of cyan line images SC1, SC2,..., SCN, magenta line image M color test images composed of SM1,..., SMN are sequentially formed. Further, a Y color test image composed of yellow line images SY 1,..., LYN is formed on the intermediate transfer belt 4. At this time, for example, the CPU 51 forms a line image inclined by 45 ° with respect to the moving direction of the intermediate transfer belt 4.

  The irradiation unit 24 of the detection sensor 21 irradiates the test image on the intermediate transfer belt 4 with light, and the detection unit 25 detects reflected light of the irradiated light. CPU51 receives the detection result which detection sensor 21 detected each line picture (S6). In FIG. 10, the position of the spot light of the light irradiated from the irradiation part 24 is shown. Each line image on the intermediate transfer belt 4 is detected at a substantially central position of the intermediate transfer belt 4.

  Next, the CPU 51 performs an inter-image distance calculation process for calculating the distance between the KCMY color test images formed on the intermediate transfer belt 4 (S7). The content of the inter-image distance calculation process in step S7 is the same as the inter-image distance calculation process in step S3 which is a subroutine shown in the flowchart of FIG. 8, and the CPU 51 obliquely intersects the moving direction of the intermediate transfer belt 4. Based on the detection result obtained by detecting the image by the detection sensor 21, the distance between the color test images is calculated. Next, based on the distance between the color test images calculated in the subroutine of step S7, the CPU 51 calculates the amount of deviation in the main scanning direction of each color image when the image is recorded on the recording paper using the intermediate transfer belt 4. (S8).

  FIG. 11 is a conceptual diagram showing a method for calculating the amount of deviation in the main scanning direction. In the figure, the detection position of the line image by the detection sensor 21 is indicated by a one-dot chain line. When there is no deviation in the main scanning direction, the distance Q between the color test images shown in FIG. 11 is the distance obtained in step S3 for the color test image consisting of a line image substantially orthogonal to the moving direction of the intermediate transfer belt 4. It becomes the same value. When the C color image is formed at an earlier timing in the main scanning direction than the K color image, the position of the C line image is shifted downward in FIG. In this case, the distance Q- between the color test images between KCs is smaller than the distance between the color test images obtained in step S3.

  Further, when the C color image is formed at a later timing in the main scanning direction than the K color image, the position of the C line image is shifted upward in FIG. In this case, the distance Q + between the color test images between KCs is larger than the distance between the color test images obtained in step S3. Therefore, the CPU 51 inclines the amount of deviation between the distance between the color test images calculated in step S3 and the distance between the color images calculated in step S7 with respect to the line image that is oblique to the moving direction of the intermediate transfer belt 4. Accordingly, the amount of deviation in the main scanning direction of each color image when an image is recorded on the recording paper can be calculated.

  Note that the image forming apparatus 1 according to the present invention forms a line image inclined in the opposite direction to the line images shown in FIGS. 10 and 11 instead of the above configuration, and shifts in the main scanning direction according to the inclination. The form which performs the process which calculates quantity may be sufficient.

  Next, the CPU 51 controls the exposure unit 3 to correct the color misregistration based on the color misregistration amounts in the sub-scanning direction and the main scanning direction so that the positions of the respective color images on the recording paper overlap each other. The amount of adjustment in the sub-scanning direction and main scanning direction for adjusting the timing for forming the image is calculated (S9). Next, the CPU 51 stores the calculated adjustment amount in the adjustment amount storage unit 54 (S10), and ends the process. When the CPU 51 forms an image on the recording paper, the timing at which the exposure unit 3 forms each color image based on the adjustment amounts in the sub-scanning direction and the main scanning direction stored in the adjustment amount storage unit 54. The image is formed so that the color images overlap each other.

  As described above in detail, in the present invention, when a test image for color matching adjustment is formed, a yellow base image is formed in advance on the intermediate transfer belt 4, and each KCM color test image is superimposed on the base image. Since the intensity of the reflected light from the portion where the image is not formed on the intermediate transfer belt 4 is stabilized, the position of the color test image can be detected with high accuracy. Therefore, accurate color matching adjustment can be performed based on the position of the color test image detected with high accuracy.

  In the present invention, the distance between the color test images is determined by forming a base image with yellow, which is a color other than black, which is a color of the color test image that is a reference for measuring the distance between the color test images. Since the reference for measurement can be detected with high accuracy, the distance between the color test images can be measured with high accuracy. In the present invention, a color test image in which a plurality of line images having a predetermined length are arranged at predetermined intervals is formed. By measuring a plurality of distances between corresponding line images between the respective colors and obtaining a distance between the color test images from the measured distances, the operation unevenness or vibration of the image forming apparatus 1 such as sagging of the intermediate transfer belt 4 is obtained. It can suppress that the measurement precision of the distance between color test images deteriorates under the influence of disturbances, such as.

  In the present embodiment, the yellow background image is formed as the background image as the background of the color test image. However, the present invention is not limited to this, and the background image is formed in other colors. May be. In the present embodiment, the light emitted from the irradiation unit 24 is white light and the background image is yellow with high reflectance. However, the light emitted from the irradiation unit 24 may be yellow light. Further, for example, the background image may be formed in cyan using the light emitted by the irradiation unit 24 as blue light. By using the color with the highest reflectance of the irradiation light as the color of the base image, the color test image can be detected with high accuracy. Further, for example, an M color test image is formed on the yellow background image, a C color test image is formed on the magenta background image, and a K color test image is formed on the cyan background image. For example, the color of the base image serving as the base may be changed according to the color of the color test image. In the case of this form, it is possible to prevent the consumption of only a single color toner for color matching adjustment. Moreover, the form which utilizes the infrared light generally utilized conventionally as light which the irradiation part 24 irradiates may be sufficient. Even in this case, since the base of the test image is in a stable and uniform surface state, the position of the color test image can be detected with higher accuracy than in the past.

  Further, in the present embodiment, a process of calculating a deviation amount in the sub-scanning direction by forming a test image composed of a line image substantially orthogonal to the moving direction of the intermediate transfer belt 4 and the moving direction of the intermediate transfer belt 4 are inclined. In the embodiment, a test image composed of intersecting line images is formed and a process of calculating a deviation amount in the main scanning direction is individually performed. However, the present invention is not limited to this. Alternatively, a test image composed of orthogonal line images and oblique line images may be formed on the intermediate transfer belt 4 to obtain the amount of deviation in the sub-scanning direction and the main scanning direction in a single process. Further, the image forming apparatus 1 of the present invention may be configured to form a test image composed of an image having a shape other than the line image.

  Further, in the present embodiment, the exposure unit 3 shows a form in which each color test image is simultaneously formed on the intermediate transfer belt 4, but other color test images of KCMY are formed at different predetermined timings. Each test image may be formed at a position on the intermediate transfer belt 4 that is separated from the relative position where each color image is formed by a method by a distance corresponding to each color.

  In the present embodiment, the image forming apparatus 1 according to the present invention forms an image on the intermediate transfer belt 4 and forms an image by transferring the image on the intermediate transfer belt 4 to a recording sheet. However, the present invention is not limited to this, and a direct transfer type image forming apparatus that directly transfers an image onto a recording sheet may be used.

  FIG. 12 is a cross-sectional view showing an example of the internal configuration of the image forming apparatus of the present invention using the direct transfer method. The image forming apparatus 1 includes exposure units 61a, 61b, 61c, and 61d, photosensitive drums 11a, 11b, 11c, and 11d, developing units 12a, 12b, 12c, and 12d, chargers 13a, 13b, 13c, and 13d, and a cleaner unit 14a. , 14b, 14c, 14d. The symbols a, b, c, and d correspond to K, C, M, and Y, respectively. The set of the exposure unit 61, the photosensitive drum 11, the developing unit 12, the charger 13, and the cleaner unit 14 corresponds to the image forming unit according to the present invention. The image forming apparatus 1 includes a conveyance belt 8 that attracts and conveys recording paper below the photosensitive drum 11, and the conveyance belt 8 moves in the direction of the arrow in the figure. A color image of each color is transferred from each photosensitive drum in the order of YMCK onto the recording paper conveyed by the conveying belt 8, thereby forming a multicolor image on the recording paper.

  In such a direct transfer type image forming apparatus 1, a test image is directly formed on the conveyor belt 8, and the formed test image is detected by the detection sensor 21, thereby performing color matching adjustment processing. Also in the image forming apparatus 1 shown in FIG. 12, the photosensitive drum 11d for forming a yellow image is disposed on the most upstream side with respect to the moving direction of the conveying belt 8 which is a moving medium according to the present invention. Also in this embodiment, a yellow base image is formed on the transport belt 8, a KCM color test image is formed on the base image, and a Y color test image is directly formed on the transport belt 8. It is possible to carry out the invention.

1 is a cross-sectional view illustrating an example of an internal configuration of an image forming apparatus of the present invention. It is a schematic diagram which shows the structural example of a detection sensor. It is a block diagram which shows the example of an internal structure of a control part. FIG. 6 is a schematic diagram illustrating an example of a test image formed on the intermediate transfer belt by the image forming apparatus. FIG. 6 is a characteristic diagram illustrating an example of a detection result by a detection sensor when a test image is directly formed on the surface of an intermediate transfer belt. It is a characteristic view which shows the example of the detection result of the test image in this invention. 4 is a flowchart illustrating a procedure of color matching adjustment processing performed by the image forming apparatus of the present invention. It is a flowchart which shows the procedure of the subroutine of the distance calculation process between images of step S3. FIG. 6 is a schematic diagram schematically illustrating a method for calculating a distance between each color test image including a plurality of line images substantially orthogonal to the moving direction of the intermediate transfer belt. FIG. 6 is a schematic diagram schematically illustrating a method for calculating a distance between color test images including a plurality of line images obliquely intersecting with the moving direction of the intermediate transfer belt. It is a conceptual diagram which shows the method of calculating the deviation | shift amount of a main scanning direction. 1 is a cross-sectional view showing an example of the internal configuration of an image forming apparatus of the present invention using a direct transfer method.

Explanation of symbols

1 Image forming apparatus 11a, 11b, 11c, 11d Photosensitive drum (image forming means)
21. Detection sensor (detection means)
22 Temperature / humidity sensor 24 Irradiation part (irradiation means)
25 Detection unit 3, 61a, 61b, 61c, 61d Exposure unit 4 Intermediate transfer belt (medium)
5 control unit 51 CPU (test image forming means)
53 ROM
8 Conveyor belt (medium)

Claims (11)

A plurality of image forming means for forming color images of different colors on a moving medium; a test image forming means for forming a color test image on the medium by each of the plurality of image forming means; and a light for each color test image. , A means for detecting reflected light of the light irradiated to each color test image by the means, a means for obtaining a distance between the color test images based on a detection result by the means, and the means obtained by the means In an image forming apparatus comprising: means for adjusting the position of the color image based on the distance between the color test images;
The test image forming means includes:
Means for causing a single image forming means to form a base image in which a predetermined area on the medium is colored with one color;
An image forming apparatus comprising: another image forming unit that forms a color test image on the base image. A plurality of image forming means for forming color images of different colors on a moving medium; a test image forming means for forming a color test image on the medium by each of the plurality of image forming means; and a light for each color test image. Irradiating means for irradiating, a means for detecting reflected light of the light irradiated to each color test image by the irradiating means, a distance measuring means for measuring a distance between the color test images based on a detection result by the means, In an image forming apparatus comprising: means for adjusting a position of a color image based on a distance between each color test image measured by the distance measuring means;
The test image forming means includes:
Means for causing a single image forming means to form a base image in which a predetermined area on the medium is colored with one color;
Means for forming each color test image on the ground image on a plurality of other image forming means;
An image forming apparatus comprising: the one image forming unit configured to form a color test image in a portion other than the predetermined region on the medium. The distance measuring means is configured to measure a distance from a specific color test image to each of a plurality of other color test images,
The image forming apparatus according to claim 2, wherein a color of the base image is different from a color of the specific color test image.   The image forming apparatus according to claim 2, wherein the color of the base image is a color having the lowest visibility among the colors of the color images formed by the plurality of image forming units.   The color of the base image is a color having the highest reflectance of light emitted from the irradiation unit among colors of color images formed by the plurality of image forming units, respectively. 5. The image forming apparatus according to any one of 4 above.   The image forming apparatus according to claim 2, wherein a color of the base image is yellow.   The light emitted by the irradiation unit includes the largest number of wavelength components reflected from the color of the base image among the wavelength components reflected from the colors of the color images formed by the plurality of image forming units. The image forming apparatus according to claim 2, wherein the image forming apparatus is an image forming apparatus. The plurality of image forming units are arranged side by side along the moving direction of the moving medium,
The one image forming unit is arranged at a position on the most upstream side in the moving direction of the moving medium among the plurality of image forming units. The image forming apparatus according to one.   9. The image forming apparatus according to claim 1, wherein the color test image is an image in which a plurality of line images having a predetermined length are arranged in a moving direction of the medium at a predetermined interval. A plurality of image forming means for forming color images of different colors on a moving medium; a test image forming means for forming a color test image on the medium by each of the plurality of image forming means; and a light for each color test image. , A means for detecting reflected light of the light irradiated to each color test image by the means, a means for obtaining a distance between the color test images based on a detection result by the means, and the means obtained by the means In an image forming apparatus comprising: a means for adjusting the position of a color image based on a distance between the color test images;
The test image forming means includes:
One image forming unit forms a base image in which a predetermined area on the medium is colored with one color,
An image forming method comprising: causing another image forming unit to form a color test image on the base image. A plurality of image forming means for forming color images of different colors on a moving medium; a test image forming means for forming a color test image on the medium by each of the plurality of image forming means; and a light for each color test image. , A means for detecting reflected light of the light irradiated to each color test image by the means, a means for obtaining a distance between the color test images based on a detection result by the means, and the means obtained by the means In an image forming apparatus comprising: a means for adjusting the position of a color image based on a distance between the color test images;
The test image forming means includes:
One image forming unit forms a base image in which a predetermined area on the medium is colored with one color,
A plurality of other image forming means, each color test image is formed on the background image,
An image forming method comprising: causing the one image forming unit to form a color test image in a portion other than the predetermined area on the medium.

Images