JP2006276428A - Image forming method and apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method for dividing an image area in one page into a plurality of small areas and with which distortion of images in each of the plurality of small areas can be corrected even when desired images are formed in each small area, respectively, and to provide an apparatus using the same. <P>SOLUTION: In the image forming method for dividing the image area in one page into the plurality of small areas and forming the desired images in each small area, respectively, the problem is dissolved by constituting the image formation method by providing a position error detection step for detecting position errors at a plurality of positions of images for detecting displacement formed in each small area by the image forming apparatus and an image correction step for correcting the images to be formed in each small area based on a detection result of the position error detection step. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method applied to an image forming apparatus such as a printer, a facsimile, or a copying machine that employs an electrophotographic method, and an apparatus using the image forming method. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method and apparatus for dividing and forming a desired image in each small area, and an image forming method capable of accurately forming a desired image in each small area and an apparatus using the same. .

JP 2003-274142 A

  Conventionally, as an image forming apparatus capable of forming an image such as this type of printer, facsimile, or copying machine, for example, yellow (Y), magenta (M), cyan (C), black (K), etc. A plurality of corresponding image forming units form images of each color such as yellow (Y), magenta (M), cyan (C), black (K), etc., and these yellow (Y), magenta (M), cyan ( C) After the primary transfer of images of each color such as black (K) on the intermediate transfer belt in a state of being superposed on each other, secondary transfer is performed collectively on the recording paper from the intermediate transfer belt, or There is a so-called tandem type which is configured to form a color image by transferring images in a superposed state onto recording paper conveyed by a paper conveying belt.

  In such an image forming apparatus, as shown in FIG. 12, when a plurality of small images having a horizontal size A and a vertical size B are formed on a general sheet such as A3 size or A4 size, FIG. As shown in FIG. 4, it is possible to divide an image area of one page into a plurality of small areas, and form a plurality of images by forming a desired image in each small area and creating a plurality of images, such as business cards and postcards. Well done in creation.

  By the way, in the case of the tandem type image forming apparatus as described above, the image is distorted within one sheet due to the influence of the exposure apparatus, the image forming unit composed of a photosensitive member, an intermediate transfer member, or the like, or the fixing unit. Is known to occur.

  When the image formed by the image forming apparatus is distorted, a plurality of sheets of the same size on which a small image having a horizontal size A and a vertical size B is originally formed as shown in FIG. 14 and 15, the horizontal size is originally A1, A2, A3, and the vertical size is B1, B2, B3, B4. When the image of the area is cut, the sizes of the small-size papers are different, and there is a problem that a plurality of small-size papers of the same size cannot be obtained. The above-mentioned variation in the size of each small-size paper, for example, even if it is small, the subtle variation in the size of each small-size paper is significant compared to printed business cards, postcards, etc. It will stand out.

  The image distortion in the one sheet is caused by distortions A1, A2, and A3 in the main scanning direction due to optical characteristics of the exposure apparatus, deformation of the mirror, lens characteristics, and the like. Further, in the image forming unit, periodic image distortion occurs mainly due to eccentricity of a rotating body such as a photosensitive drum, a transfer driving roll, and a transfer belt, accuracy of a driving gear, and the like.

  In the case of the tandem type color image forming apparatus, such image distortion appears as color misregistration and is a factor that greatly deteriorates the image quality. In order to prevent the variation of the rotating body from appearing as color misregistration, the variation of each color is synchronized, but the image distortion itself remains.

  Furthermore, the above-described image distortion further increases when the paper on which the image is formed is heated and pressed by the fixing device, and the image distortion as shown in FIG. 14 is about 0.5 to several mm. appear.

  Thus, when an image as shown in FIG. 15 is created and divided and used with image distortion, the position of the divided image is shifted from the center of the paper as shown in FIGS. In the worst case, the image may protrude from the divided paper.

  Also, as shown in FIG. 16, by providing a mark such as a registration mark on the image and dividing it based on this mark, the image can be placed at the center of the paper. In this case, the registration mark is used as a mark. There is a problem that it is necessary to cut the sheet by adjusting it every time, a special post-processing device capable of adjusting the cutting position is required, and the sizes of the divided sheets are scattered.

  Therefore, a technique disclosed in Japanese Patent Laid-Open No. 2003-274142 has already been proposed for such a problem.

  An image forming apparatus according to JP-A-2003-274142 includes an image forming unit that forms an image from image data, an image reading unit that reads an image formed from the image data, the read image, A detection unit that detects deformation of the formed image based on the image indicated by the image data, and an image correction unit that corrects the image data based on the detection result of the deformation. is there.

  However, the conventional technique has the following problems. That is, in the case of the image forming apparatus according to Japanese Patent Application Laid-Open No. 2003-274142, the image distortion can be corrected. However, the image forming apparatus corrects the inside of one sheet to be constant. This is a technology, and has a problem that it cannot cope with the periodic fluctuation of the image position in the paper.

  Accordingly, the present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to divide an image area of one page into a plurality of small areas, and to each desired small area. An object of the present invention is to provide an image forming method and an apparatus using the image forming method capable of correcting image distortion in a plurality of small regions even when images are formed.

That is, the invention described in claim 1 is an image forming method in which an image area of one page is divided into a plurality of small areas, and a desired image is formed in each small area.
A position error detection step of detecting position errors at a plurality of positions of the position shift detection image formed in each small region by the image forming apparatus;
An image forming method comprising: an image correcting step for correcting an image formed in each of the small regions based on a detection result of the position error detecting step.

The invention described in claim 2 is an image forming apparatus that divides an image area of one page into a plurality of small areas and forms a desired image in each of the small areas.
Position error detection means for detecting position errors at a plurality of positions of the position shift detection image formed in each small region by the image forming apparatus;
An image forming apparatus comprising: an image correcting unit that corrects an image formed in each of the small regions based on a detection result of the position error detecting unit.

  Further, in the invention described in claim 3, the misregistration detection image is a grid-like image in which a plurality of straight lines intersect each other in the vertical direction and the horizontal direction, and the position error detection means includes: The image forming apparatus according to claim 2, wherein the positions of a plurality of intersections of the grid image are detected.

According to a fourth aspect of the present invention, in the image forming apparatus according to the second or third aspect, the image correcting unit corrects the position of the image for each of the plurality of small areas. It is.

  Furthermore, the invention described in claim 5 is characterized in that the image correction means corrects the image position of each small region at a position along the main scanning direction and the sub-scanning direction. The image forming apparatus according to any one of the above.

  The invention described in claim 6 is characterized in that the image correction means corrects the image position of each small region with inclination in the main scanning direction and the sub-scanning direction. An image forming apparatus as described above.

  Furthermore, the invention described in claim 7 is characterized in that the image correction means corrects the image position of each small region at a magnification in the main scanning direction and the sub-scanning direction. An image forming apparatus as described above.

  According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the second to seventh aspects, the image correcting unit corrects an image based on image data.

  Furthermore, the invention described in claim 9 is characterized in that the image forming apparatus includes information on an image formed in each small area, division information for dividing an image area of one page into a plurality of small areas, and the image correcting unit. 9. The image forming apparatus according to claim 2, wherein the image is formed based on the correction information of the image obtained by the method.

The invention described in claim 10 is characterized in that the image forming apparatus has an intermediate transfer belt for transferring a plurality of images of different colors formed by a plurality of image forming units,
10. The position error detection by the position error detection unit and the image correction by the image correction unit are performed in synchronization with a drive roll that drives the intermediate transfer belt. This is an image forming apparatus.

Furthermore, in the invention described in claim 11, the image forming apparatus includes an image carrier on which an image is formed,
The image formation according to any one of claims 2 to 9, wherein the position error detection by the position error detection unit and the image correction by the image correction unit are performed in synchronization with rotation of the image carrier. Device.

  According to the present invention, even when the image area of one page is divided into a plurality of small areas and a desired image is formed in each of the small areas, the image distortion in each of the plurality of small areas is corrected. Can be provided, and an image forming method using the image forming method can be provided.

  Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1
FIG. 2 is a schematic configuration diagram showing a tandem type color electrophotographic copying machine as an image forming apparatus to which the image forming method according to Embodiment 1 of the present invention is applied. Although this tandem type color electrophotographic copying machine is provided with an image reading device, the image forming device is not provided with an image reading device, and is based on image data output from a personal computer (not shown). Of course, a color printer, a facsimile, or the like that forms an image may be used.

  In FIG. 2, reference numeral 1 denotes a main body of a tandem type color electrophotographic copying machine. The color electrophotographic copying machine main body 1 has an image reading device (IIT) for reading an image of a document 2 at an upper portion on one end side thereof. : ImageInputTerminal) 4, and the image data output from the image reading device 4 or a personal computer (not shown), or the like is sent to the inside of the color electrophotographic copying machine main body 1 via a telephone line or a LAN. An image processing apparatus (IPS: Image Processing System) 12 that performs predetermined image processing on the received image data, and an image output apparatus that outputs an image based on the image data that has been subjected to predetermined image processing by the image processing apparatus 12 (IOT: ImageOutputTerminal) 100 There.

  In the image reading device 4, an image of the original 2 pressed on the platen glass 5 by the platen cover 3 or an original conveyed automatically by an ADF (not shown) is read. The image reading device 4 illuminates a document 2 placed on a platen glass 5 with a light source 6, and reflects a reflected light image from the document 2 from a full-rate mirror 7, half-rate mirrors 8 and 9, and an imaging lens 10. The image reading element 11 composed of a CCD or the like is scanned and exposed through a reduction optical system, and the color material reflected light image of the document 2 is formed at a predetermined dot density (for example, 16 dots / mm) by the image reading element 11. It is configured to read.

  The color material reflected light image of the document 2 read by the image reading device 4 is subjected to image processing as, for example, document reflectance data of three colors of red (R), green (G), and blue (B) (8 bits each). The image processing apparatus 12 sends a predetermined correction such as shading correction, position shift correction, brightness / color space conversion, gamma correction, frame erasing, color / moving editing, etc., to the reflectance data of the document 2. Image processing is performed.

  The image data that has been subjected to the predetermined image processing by the image processing apparatus 12 as described above is a four-color document of yellow (Y), magenta (M), cyan (C), and black (K) (each 8 bits). Converted to color material gradation data (raster data), as will be described below, yellow (Y), magenta (M), cyan (C), and black (K) image forming units 13Y, 13M, 13C, 13K laser writing devices (ROS) 14Y, 14M, 14C, and 14K are sent to these laser writing devices 14Y, 14M, 14C, and 14K according to the original color material gradation data of a predetermined color. Image exposure with the laser beam LB is performed.

  By the way, inside the tandem type color electrophotographic copying machine main body 1, as described above, four image forming units 13Y of yellow (Y), magenta (M), cyan (C), and black (K), 13M, 13C, and 13K are arranged in parallel at regular intervals in the horizontal direction.

  These four image forming units 13Y, 13M, 13C, and 13K are all configured in the same manner, and roughly divided, a photosensitive drum as a latent image carrier that is rotationally driven at a predetermined speed along the arrow A direction. 15, a scorotron 16 for primary charging as charging means for uniformly charging the surface of the photosensitive drum 15, and a laser beam corresponding to the image information of each color on the surface of the photosensitive drum 15 by scanning exposure. The image forming apparatus (image forming means) includes a laser writing device 14 that forms an electrostatic latent image, a developing device 17 that develops the electrostatic latent image formed on the photosensitive drum 15, a cleaning device 18, and the like. ing.

  As shown in FIG. 2, the laser writing device 14 modulates the semiconductor laser 19 according to the original color material gradation data, and emits a laser beam LB from the semiconductor laser 19 according to the gradation data. The laser beam LB emitted from the semiconductor laser 19 is deflected and scanned by the rotary polygon mirror 22 via the reflection mirrors 20 and 21, and again carries an image via the reflection mirrors 20 and 21 and the plurality of reflection mirrors 23 and 24. Scanning exposure is performed on the photosensitive drum 15 as a body.

  From the image processing device 12, the laser writing devices 14Y, 14M, 14C of the image forming units 13Y, 13M, 13C, and 13K for each color of yellow (Y), magenta (M), cyan (C), and black (K) are provided. Image data (raster data) of each color is sequentially output to 14K, and laser beams LB emitted according to the image data from these laser writing devices 14Y, 14M, 14C, and 14K are supplied to the respective photosensitive drums 15Y, 15M, The surfaces of 15C and 15K are scanned and exposed to form an electrostatic latent image. The electrostatic latent images formed on the photosensitive drums 15Y, 15M, 15C, and 15K are respectively yellow (Y), magenta (M), and cyan (C) by the corresponding developing devices 17Y, 17M, 17C, and 17K. , And developed as a toner image of each color of black (K).

  Yellow (Y), magenta (M), cyan (C), and black (K) sequentially formed on the photosensitive drums 15Y, 15M, 15C, and 15K of the image forming units 13Y, 13M, 13C, and 13K. The unfixed toner images of the respective colors are superimposed on the surface of the intermediate transfer belt 25 at a primary transfer position where the photosensitive drums 15Y, 15M, 15C, and 15K are in contact with the intermediate transfer belt 25 as an intermediate transfer member. Sequentially transferred. Semiconductive bias rolls 26Y, 26M, 26C, and 26K are disposed on the back surface side of the intermediate transfer belt 25 at the primary transfer position, and the intermediate transfer belt is provided by these bias rolls 26Y, 26M, 26C, and 26K. 25 abuts on the surfaces of the photosensitive drums 15Y, 15M, 15C, and 15K. The primary transfer bias rolls 26Y, 26M, 26C, and 26K are applied with a voltage having a polarity opposite to the charging polarity of the toner, and the respective colors formed on the photosensitive drums 15Y, 15M, 15C, and 15K are undetermined. The contact toner images are sequentially electrostatically attracted onto the intermediate transfer belt 25 to form a full-color image.

  The intermediate transfer belt 25 is stretched between a driving roll 27, a driven roll 28, a steering roll 29, an opposing roll (backup roll) 30 for secondary transfer, and a driven roll 32 with a constant tension. The drive roller 27 is rotationally driven by a dedicated drive motor with excellent constant speed (not shown) and is driven to circulate at a predetermined speed in the arrow B direction.

  When a single color image is formed, only the desired color image forming units 13Y, 13M, 13C, and 13K are operated, and a desired single color unfixed toner image is formed on the intermediate transfer belt.

  In this way, the unfixed toner images of the respective colors of yellow (Y), magenta (M), cyan (C), and black (K) that have been primary-transferred multiple times on the intermediate transfer belt 25 are intermediate transfer belt 25. Is rotated to the secondary transfer position facing the conveyance path of the recording paper 33 (sheet), and an unfixed toner image is transferred from the intermediate transfer belt 25 to the recording paper 33 at the secondary transfer position. Transcribed. The recording paper 33 is fed from the print paper tray 34 by the feed roller 35, transported to the registration roller 38 by a paper transport path 37 having a plurality of transport rollers 36, and temporarily stopped. Next, the recording paper 33 is conveyed by the registration roller 38 at a predetermined timing, and is sandwiched between the secondary transfer bias roll 39 and the intermediate transfer belt 25. Further, on the back side of the intermediate transfer belt 25 at the secondary transfer position, a backup roll 30 that is opposed to the bias roll 39 and a metal roll 41 that contacts the backup roll 30 are disposed. At the secondary transfer position, by applying a voltage (normal transfer bias) having the same polarity as the toner charging polarity to the metal roll 41, the bias roll 39 forms a transfer electric field as a counter electrode, and an intermediate transfer belt. The unfixed toner image carried on 25 is electrostatically transferred to the recording paper 33 at the secondary transfer position. The secondary transfer bias roll 39 is cleaned by a brush roll 42.

  The recording sheet 33 on which the unfixed toner image is transferred is discharged from the intermediate transfer belt 25 while being discharged by a flat plate discharging device 43, and then is used as a double transfer material transporting unit via the chute 44. Are fed to the fixing device 47 by the paper transport belts 45 and 46, and the fixing process of the unfixed toner image is performed. The paper transport belts 45 and 46 are composed of an endless rubber belt 45c stretched between a driving roller 45a and a driven roller 45b, and five rubber belts are stretched in parallel by one paper transport belt. ing.

  The fixing device 47 includes a pair of fixing rolls (fixing members) including a heating roll 48 having a heater (not shown) therein and a pressure roll 49 disposed in pressure contact with the heating roll 48. is doing. When the recording paper 33 on which the unfixed toner image is formed passes through the fixing area between the heating roll 48 and the pressure roll 49, the fixing device 47 generates a toner image on the recording paper 33 by heat and pressure. It has become established.

  During the fixing process, the unfixed toner surface of the recording paper 33 is usually in direct contact with the outer peripheral surface of the heating roll 48, so that a part of the unfixed toner on the recording paper 33 is transferred to the heating roll 48 side. A phenomenon (toner offset phenomenon) in which the toner re-transfers to the recording paper 33 after one rotation of the heating roll 48 occurs. Therefore, in this embodiment, in order to prevent the toner offset phenomenon, a release agent coating device 50 that applies a release agent to the surface of the heating roll 48 is provided.

  On the other hand, residual toner is removed from the intermediate transfer belt 25 after the secondary transfer of the unfixed toner image is completed, as shown in FIG. 1, by a belt cleaner 55 positioned downstream of the secondary transfer portion.

  When creating a double-sided print, as shown in FIG. 2, the recording paper 33 does not pass through the fixing device 47 and the first side is fixed, and then is not discharged outside the image forming apparatus. Then, a switching gate 56 disposed on the downstream side of the fixing device 47 switches to the direction of the sheet reversing unit 57 and the double-sided sheet conveying unit 58. In the paper reversing unit 57, the recording paper 33 is reversed by switchback, passes through the paper conveying unit 58, and is conveyed again to the registration roller 38. While the recording paper 33 is conveyed to the registration roller 38, an image for the second surface is formed on the intermediate transfer belt 25 in the same manner as the image forming process for the first surface. The first recording sheet 33 on which the first surface is imaged at the timing is conveyed to the secondary transfer unit, and the image is transferred to the second surface in the same manner as the first surface. Thereafter, the recording paper 33 having the toner image transferred onto the second surface is conveyed to the fixing device 47 by the paper conveying belts 45 and 46, and after fixing processing, is provided outside the image forming apparatus. The sheet is discharged onto the discharge tray 59, and the image forming process for a series of double-sided printing is completed.

As the intermediate transfer belt 25, a synthetic resin such as polyimide or polyamide containing an appropriate amount of an antistatic agent such as carbon black and formed into an endless belt shape is used, and its volume resistivity is 10 ⁶ to 10 ^14. For example, the thickness is set to 0.1 mm.

The primary transfer bias roll 26 is made of foamed urethane rubber in which carbon black is dispersed, and has a volume resistance of 10 ⁶ to 10 ¹⁰ Ω, a roll diameter of φ28 mm, and a hardness of 35 °, for example. (Asuka C) is set.

Further, the bias roll 39 for secondary transfer is made of urethane rubber tube with carbon black dispersed on the surface, the inside is made of foamed urethane rubber with carbon black dispersed, and the roll surface is coated with fluorine, It is formed so that the resistance is 10 ³ to 10 ¹⁰ Ω and the roll diameter is φ28 mm, and the hardness is set to 30 ° (Asuka C), for example. On the other hand, the backup roll 30 is made of EPDM and NBR blend rubber tube with carbon black dispersed on the surface, EPDM rubber inside, and has a surface resistivity of 10 ⁷ to 10 ¹⁰ Ω / □ and a roll diameter. It is formed to have a diameter of 28 mm, and the hardness is set to 70 ° (Asuka C), for example.

  The rubber belts of the paper conveying belts 45 and 46 are made of rubber made of EPDM and are endless, and the thickness of the belt is set to about 1 mm.

  Further, the heating roll 48 and the pressure roll 49 are formed by coating a silicone rubber on the surface of a cylindrical core made of a metal having high thermal conductivity such as aluminum.

  By the way, in the image forming method according to this embodiment, an image region of one page is divided into a plurality of small regions, and a desired image is formed in each small region. A position error detection step for detecting position errors at a plurality of positions of the position deviation detection image formed in the region, and an image formed in each of the small regions is corrected based on the detection result of the position error detection step. And an image correction step.

  In addition, the image forming apparatus according to this embodiment divides an image area of one page into a plurality of small areas, and forms a desired image in each small area. A position error detecting unit that detects position errors at a plurality of positions of the image for detecting misalignment formed in the region, and an image formed in each of the small regions is corrected based on a detection result of the position error detecting unit. And an image correcting means.

  Further, in this embodiment, the positional deviation detection image is a grid-like image in which a plurality of straight lines intersect each other in the vertical direction and the horizontal direction, and the position error detection means The positions of a plurality of intersections are detected.

  In this embodiment, the image correction means is configured to correct the position of the image for each of the small areas divided into a plurality.

Detection of Image Distortion First, a configuration for detecting image distortion in the color electrophotographic copying machine according to this embodiment will be described.

  In the color electrophotographic copying machine, as shown in FIG. 2, an image of a predetermined test pattern is formed on the recording paper 33, and the recording paper 33 on which the image of the test pattern is formed is fixed by a fixing device 47. Is given. The image of the test pattern fixed on the recording paper 33 is read by the image reading device 4 such as a scanner, and the distortion of each part of the paper is stored in the memory. At that time, as the image reading device 4, as shown in FIG. 2, the one mounted on the color electrophotographic copying machine main body 1 may be used as it is, or provided on the paper conveyance path of the image forming apparatus. It may be configured, or a single scanner provided as a separate device may be used.

  Further, as the test pattern 101, for example, as shown in FIG. 3A, a lattice pattern in which straight images 102 and 103 are formed at regular intervals along the vertical and horizontal directions is used. . In order to detect the image of the test pattern 101, the positions of the intersections 104 of the lattice-shaped test pattern 101 may be detected along the vertical direction and the horizontal direction. The position of the horizontal line 103 is detected, the vertical and horizontal positions of each intersection are obtained, and the coordinates (X (m, n), Y (m, n)) of each intersection are stored in the memory 111. You may do it.

  FIG. 1 is a block diagram illustrating a control circuit of the color electrophotographic copying machine together with an image forming unit.

  In FIG. 1, reference numeral 110 denotes a control means for controlling the operation of the color electrophotographic copying machine and a CPU as an image correction means, and 111 denotes the coordinates of intersections detected by the image reading device 4 which also functions as a position error detection means ( A memory for storing parameters such as X (m, n), Y (m, n)), 112 a user interface for operating the color electrophotographic copying machine, 113 an image data 114 for each image forming unit An image output circuit functioning also as an image correcting means for outputting, a registration detection circuit 115 for detecting a registration error based on a registration mark detected by the registration sensor 116, and 117 for detecting the home of the intermediate transfer belt 25. Reference numeral 118 denotes a belt home sensor; 118, rotation information of a photosensitive drum detected by a photosensitive sensor (not shown); The rotation information of the detected driving roll by shows no drive roll sensor, respectively.

  When the recording paper 33 on which the test pattern 101 is formed undergoes a fixing process by the fixing device 47, the amount of distortion depends on the state of the paper (water content, etc.). Distortion is also relatively uniform within the paper. As described above, when the distortion (fluctuation) in the fixing device 47 is small, image distortion on the intermediate transfer belt 25 as an image forming unit before fixing becomes a problem.

  Therefore, in order to detect the image distortion on the intermediate transfer belt 25, it is also possible to detect the image distortion by a color misregistration detection regicon sensor 116.

  Even if the image reading device 4 or the like is not equipped with position error detection means, after the test pattern 101 is formed on the recording paper 33, the image of the test pattern 101 is directly measured using a ruler or the like. Then, the measured position error value may be input from the numeric keypad of the user interface 112 or the like.

  On the other hand, when the image forming apparatus includes the image reading apparatus 4 or the like, or when the image reading apparatus 4 is built in the image forming apparatus, the data detected by the image reading apparatus 4 is directly stored in the memory 111. The data can be stored, but even in the case of an external device, data can be input to the memory 111 from the outside.

  Further, when an image is printed from a personal computer (PC) or the like, the test pattern 101 may be detected and input by a printer driver installed in the personal computer (PC). Further, it may be configured to input directly from the user interface (control panel) 112 of the image forming apparatus.

  Since the image distortion generated on the recording paper 33 on which the test pattern 101 is formed differs for each paper, the memory 111 for storing detection data is separately provided according to the paper type, size, tray used, image mode, and the like. You may comprise so that it may be provided. In the case of image distortion that does not depend on the paper, it may be used as a standard value.

  In the color electrophotographic copying machine, among the factors that cause image distortion, the distortion generated in the exposure optical system is an image curvature called a bow as shown in FIG. An inclination of the image called a skew, a magnification shift in the main scanning direction as shown in (G), and the like can be mentioned, and image distortion mainly changes along the main scanning direction. These image distortion data may be stored in the memory 111 corresponding to the main scanning direction. The cause of the image distortion is inclination or distortion of a mirror, a lens, an LED, or the like.

  Further, as distortion generated in the drive system of the photosensitive drum 15 and the drive system of the intermediate transfer belt 25, meandering of an image called a walk as shown in FIG. 4C, and sub-scanning as shown in FIG. A magnification shift along the direction can be cited, and the distortion appears mainly changing in the sub-scanning direction. Since these are determined by the rotational position of the photosensitive drum 15, the rotational position of the intermediate transfer belt 25, and the rotational position of the drive roll 27 of the intermediate transfer belt 25, they change depending on these phases. When the circumferential length of the photosensitive drum 15, the circumferential length of the intermediate transfer belt 25, and the circumferential length of the driving roll 27 are in an integer multiple relationship, for example, the diameter φ of the photosensitive drum 25 is 84 mm, and the driving roll 27 When the diameter φ is 42 mm and the peripheral length of the intermediate transfer belt 25 is 2111 mm, the distortion of one belt rotation is stored in the memory 111 corresponding to the belt position with the longest belt position as a reference. It is desirable to keep it. Synchronization with the belt position can be made to correspond to the belt position by detecting a mark attached to the belt by the belt home sensor 117. At this time, the error can be reduced by measuring and averaging over several belt revolutions.

  As described above, when image distortion is detected on the recording paper 33, it is desirable to detect a plurality of images formed by one rotation of the belt. However, image distortion generated in these image forming elements can also be detected by the registration control sensor 116 of the intermediate transfer belt 25.

  Further, the largest of these fluctuation factors is due to the photosensitive drum 15 and the drive roll 27 of the intermediate transfer belt 25. In the tandem type color image forming apparatus as shown in FIG. 2, since the color misregistration is caused unless the component by the photosensitive drum 15 is also kept small, the component by the photosensitive drum 15 is used in such a tandem type color image forming apparatus. Is kept small. Therefore, it is often sufficient to detect only the intermediate transfer belt 25 by the drive roll 27. In a monochrome or so-called four-cycle color image forming apparatus, the driving roll of the photosensitive drum and the intermediate transfer belt is a major factor of image distortion.

  The image distortion caused by the drive roll 27 (or the photosensitive drum) of the intermediate transfer belt 25 can be detected by detecting the registration control. However, since the period is within the recording paper 33, it can be detected on one sheet. It is also possible to measure. Also in this case, in order to synchronize the photosensitive drum 15 and the drive roll 27 of the intermediate transfer belt 25, a signal 118 (such as the Z phase of the encoder on the rotating shaft) generated once per rotation of the photosensitive drum 15 is used. .

  Further, when the intermediate transfer belt 25, the photosensitive drum 15, and the driving roll 27 are not in an integral multiple relationship (asynchronous), the frequency filter and the information on the state shifted by a half cycle from the respective synchronization signals are used. It is necessary to extract individual components and store them in separate memories 111.

  Further, distortion generated in the paper transport system and the fixing system occurs corresponding to the recording paper 33. In this case, even if distortion is detected on the intermediate transfer belt 25, it cannot be dealt with. Such distortion may occur in all the patterns shown in FIG. 4, but corresponds to the sheet position, and therefore can be grasped by measuring once on the recording sheet 33. In addition, the distortion generated in the paper transport system and the fixing system varies depending on the paper size, type, and the like, so it is desirable to measure each.

  These distortions are synthesized, and it is desirable to use a plurality of the above-described methods.

Correction of Image Distortion Next, correction of image distortion detected as described above will be described.

As described above, when the position information of each point in the recording sheet 33 is stored in the memory 111, when forming an image on the corresponding sheet, from the sheet division information, as shown in FIG. The correction amount of the area ((Xa, Ya), (Xb, Yb)...) Is calculated. As the correction amount, an average value of position information (X (m, n), Y (m, n)) in the corresponding region is used.
Here, as the sheet division information, for example, as shown in FIG. 12, one page image area formed on one recording sheet 33 is divided into three in the vertical direction and three in the horizontal direction. In this case, the information is set to 3 × 3, and when dividing into 4 in the vertical direction and 3 in the horizontal direction, information such as 4 × 3 is used. However, the information is not limited to this.

For example, when an image area of one page is divided into three in the vertical direction and three in the horizontal direction, the correction value (Xa, Ya) of the upper left area a is calculated as follows.
Xa = (1 / k) · ΣX (m, n)
Ya = (1 / k) · ΣY (m, n)
Here, k indicates the number in the region a.

  Using this correction amount (Xa, Ya), position correction in the region a is performed, and image formation is performed after performing position correction in the other regions in the same manner.

  In this method, only the XY position is set, but the magnification of each image is different. Therefore, in addition to the calculation of the position correction amount, by calculating the individual magnification correction amount and applying the correction, position correction with higher accuracy becomes possible.

  Now, a method for calculating individual magnification correction amounts will be described with reference to FIG.

  As shown in FIG. 6, the position error at the upper left of the region a is X (x1, y1), Y (x1, y1), and similarly, the position error at the upper right is X (x2, y1), Y (x2, y1). If the lower left position error is X (x1, y2), Y (x1, y2), and the lower right position error is X (x2, y2), Y (x2, y2), the lateral magnification MX = (= X (x1, y1) -X (x1, y2) + X (x2, y1) -X (x2, y2)) / (2.X0) +1, vertical magnification MY = (Y (x1, y1) -Y (x1) , Y2) + Y (x2, y1) −Y (x2, y2)) / (2 · Y0) +1. X0 and Y0 indicate reference distances in the XY directions of the four corner points.

  By calculating the magnification as described above and correcting the image in accordance with the magnification, it is possible to correct the magnification in each region.

Similarly, the skew in the X and Y directions can be calculated and corrected as follows.
SY = (Y (x1, y1) -Y (x1, y2) + Y (x2, y1) -Y (x2, y2)) / 2
SX = (X (x1, y1) -X (x1, y2) + X (x2, y1) -X (x2, y2)) / 2

  As described above, when the image correction amount is calculated in each region, the image position is corrected accordingly.

  Here, the correction of the image position is performed by the image output circuit 113 having a function as an image correction unit. As shown in FIG. 7, this position correction can be performed by shifting the image data 112 in accordance with the correction amounts in the x direction and the y direction. Further, skew correction can be performed by inclining the image data 112 in a direction opposite to the direction in which the skew is generated. Furthermore, as is well known, the magnification can be changed by adding data to the image data 112 according to the magnification or thinning it out.

  As described above, in the color image forming apparatus according to the above embodiment, even when the image area of one page is divided into a plurality of small areas and a desired image is formed in each small area, It is possible to correct image distortion in a small area.

FIG. 8 shows an embodiment in which the present invention is applied to a copying machine equipped with a scanner.
In the case of the copying machine 201, a test pattern 101 is created in advance, image distortion is detected by the image reading device 202, and position information of each point in the memory is stored. When the present invention is applied when an image of the original B is read by the image reading device 202 and nine sheets of images are formed on one page, the image data of the image reading device 202 is corrected and sent to the image forming unit 201. The image forming unit 201 may correct the position.

  FIG. 9 shows an embodiment in which the present invention is applied to a printer 301 connected to a personal computer (PC) 302, and a scanner 303 is separately connected to the personal computer (PC) 302.

  The printer 301 sends image data and division information from a personal computer (PC) 302, performs position correction in an image forming unit (inside the printer), and outputs an image. In this case, the position information is stored in the memory by any one of the above-described methods, and a position-corrected image is formed.

  As shown in FIG. 10, if the test pattern 101 is created by the printer 301, detected by the scanner 303, and the position information can be input to the personal computer (PC) 302, the test pattern 101 is displayed on the personal computer (PC) 302. The printer driver may convert the image into image data whose position has been corrected in advance and transfer the image data to the printer 301.

  Note that the position information may not be read by the scanner 303 but may be input by another method. For example, the test pattern 101 may be measured with a ruler and input directly with a keyboard of a personal computer (PC) 302. If position error information is stored in the memory in advance in the printer 301, the position error information may be called from the printer 301 and the position correction may be performed on the personal computer (PC) 302 side as described above.

  Further, as shown in FIG. 11, the position information read by the scanner 303 may be transferred to the printer 301 together with the image data, the division information, and the position correction information to form an image.

  In the above-described embodiment, correction is performed in an area divided in one page. However, when the test pattern 101 is detected and stored in the memory, the image position can be individually corrected. In this case, since it does not depend on the division method, it is possible to correct all the images. Furthermore, the correct position is obtained at any point in the image, and the image quality is improved.

FIG. 1 is a block diagram showing a main part of a tandem type color electrophotographic copying machine as an image forming apparatus to which an image forming method according to Embodiment 1 of the present invention is applied. FIG. 2 is a block diagram showing a tandem type color electrophotographic copying machine as an image forming apparatus according to Embodiment 1 of the present invention. FIG. 3 is an explanatory diagram showing a test chart. FIG. 4 is an explanatory diagram showing different states of image distortion. FIG. 5 is an explanatory diagram showing the operation of a tandem type color electrophotographic copying machine as an image forming apparatus to which the image forming method according to Embodiment 1 of the present invention is applied. FIG. 6 is an explanatory diagram showing the operation of the present invention. FIG. 7 is an explanatory diagram showing the control operation of the present invention. FIG. 8 is a block diagram showing an embodiment to which the present invention is applied. FIG. 9 is a block diagram showing an embodiment to which the present invention is applied. FIG. 10 is a block diagram showing an embodiment to which the present invention is applied. FIG. 11 is a block diagram showing an embodiment to which the present invention is applied. FIG. 12 is an explanatory view showing an image forming method. FIG. 13 is an explanatory view showing a conventional image forming method. FIG. 14 is an explanatory view showing a conventional image forming method. FIG. 15 is an explanatory view showing a conventional image forming method. FIG. 16 is an explanatory view showing a conventional image forming method. FIG. 17 is an explanatory view showing a conventional image forming method.

Explanation of symbols

  4: Image reading device, 110: CPU, 111: Memory, 112: User interface, 113: Image output circuit, 114: Image data.

Claims (11)

In an image forming method of dividing an image area of one page into a plurality of small areas and forming a desired image in each of the small areas,
A position error detection step of detecting position errors at a plurality of positions of the position shift detection image formed in each small region by the image forming apparatus;
An image forming method comprising: an image correcting step for correcting an image formed in each of the small regions based on a detection result of the position error detecting step. In an image forming apparatus that divides an image area of one page into a plurality of small areas and forms a desired image in each of the small areas.
Position error detection means for detecting position errors at a plurality of positions of the position shift detection image formed in each small region by the image forming apparatus;
An image forming apparatus comprising: an image correcting unit that corrects an image formed in each of the small regions based on a detection result of the position error detecting unit. The misalignment detection image is composed of a grid-like image in which a plurality of straight lines intersect each other along the vertical direction and the horizontal direction, and the position error detection means detects the positions of a plurality of intersections of the grid-like image. The image forming apparatus according to claim 2. The image forming apparatus according to claim 2, wherein the image correction unit corrects the position of the image for each of the small areas divided into a plurality of parts. The image forming apparatus according to claim 2, wherein the image correction unit corrects the image position of each small region at a position along the main scanning direction and the sub-scanning direction. 5. The image forming apparatus according to claim 2, wherein the image correction unit corrects the image position of each small region with inclination in the main scanning direction and the sub-scanning direction. 6. 5. The image forming apparatus according to claim 2, wherein the image correction unit corrects the image position of each small region at a magnification in the main scanning direction and the sub-scanning direction. 6. The image forming apparatus according to claim 2, wherein the image correcting unit corrects an image based on image data. The image forming apparatus generates an image based on information on an image to be formed in each small area, division information for dividing an image area of one page into a plurality of small areas, and image correction information by the image correction unit. The image forming apparatus according to claim 2, wherein the image forming apparatus is formed. The image forming apparatus includes an intermediate transfer belt that transfers a plurality of images of different colors formed by a plurality of image forming units,
10. The position error detection by the position error detection unit and the image correction by the image correction unit are performed in synchronization with a drive roll that drives the intermediate transfer belt. Image forming apparatus. The image forming apparatus has an image carrier on which an image is formed,
The image formation according to any one of claims 2 to 9, wherein the position error detection by the position error detection unit and the image correction by the image correction unit are performed in synchronization with rotation of the image carrier. apparatus.

Images