Image reading device and image forming device

Abstract

To provide an image reading device and an image forming apparatus that can reduce a device cost.SOLUTION: An image reading device comprises a detection unit that detects the positions of a plurality of images for detection formed by an image forming apparatus at different positions in a main scanning direction of a recording medium, and the detection unit has a detection range equal to or less than the width of the recording medium. The image forming apparatus comprises an image forming unit that forms an image on a recording medium and the image reading device, and the image reading device detects the positions of the images for detection formed by the image forming unit on the recording medium.SELECTED DRAWING: Figure 3B

Description

[Technical field]

[0001] The present invention relates to an image reading device and an image forming device. [Background technology]

[0002] In an image forming apparatus that forms an image on a recording medium, paper, strict standards (conditions) may be set for aligning the image with respect to the paper. In order to align the image, detection marks are formed as images on the edges or four corners of the paper, and the formed detection marks are read by an image reading device such as a CIS (Contact Image Sensor). Then, the image formation conditions (e.g., the timing of image formation, etc.) are changed according to the distance between the detection mark read by the image reading device and the edge of the paper, and the image formation position is corrected, thereby aligning the image (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2000-305324 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned image alignment method, the larger the paper size in the main scanning direction (paper width direction) perpendicular to the paper transport direction, the wider the width of the image reading device in the main scanning direction becomes. In other words, in order to read the detection marks formed on the four corners and ends of a large-sized paper, the width of the image reading device in the main scanning direction needs to be widened. This causes a problem that the image reading device itself becomes large and the device cost becomes high. In addition, in order to prevent the image reading device from becoming large, a method of arranging two relatively small image reading devices on both sides of the paper in the main scanning direction can be considered, but there is a problem that the device cost becomes high due to the increase in the number of image reading devices.

[0005] An object of the present invention is to provide an image reading device and an image forming device that can reduce the cost of the device. [Means for solving the problem]

[0006] The image reading device according to the present invention comprises: The image forming apparatus prints the recording medium Perpendicular to the conveying direction Main scanning direction The recording medium in A detection unit that detects the positions of a plurality of detection images formed at different positions on the substrate; a control unit that determines positions of the plurality of detection images in a main scanning direction based on a detection result by the detection unit; Equipped with the detection unit has a detection range in the main scanning direction that is equal to or smaller than a width of the recording medium, Based on the detection results by the detection unit, the control unit calculates the distance to each detection image using the same end portion in the main scanning direction of the recording medium as a reference, thereby determining the positions of each of the multiple detection images in the main scanning direction.

[0007] The image forming apparatus according to the present invention comprises: an image forming unit that forms an image on a recording medium; The image reading device; Equipped with The image reading device detects the position of the detection image formed on the recording medium by the image forming unit. Effect of the Invention

[0008] According to the present invention, the cost of the device can be reduced. [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention. [Diagram 2] 2 is a block diagram showing a main part of a control system of the image forming apparatus according to the embodiment of the present invention. FIG. [Figure 3A]FIG. 4 is a diagram illustrating the image reading unit, as viewed from the side of the paper. [Figure 3B] FIG. 2 is a diagram illustrating an image reading unit, as viewed from above the paper. [Figure 4] 10 is a flowchart illustrating an image registration method using an image reading unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0011] Fig. 1 is a diagram showing an overall configuration of an image forming apparatus 1 according to the present embodiment, and Fig. 2 is a block diagram showing a main part of a control system of the image forming apparatus 1 according to the present embodiment.

[0012] The image forming apparatus 1 is capable of forming an image on a sheet of paper (recording medium) etc. As shown in Fig. 1, the image forming apparatus 1 includes an image forming apparatus main body 100, a paper feed section 300, a buffer section 400, an image reading section 500, a paper discharge section 600, etc.

[0013] The image forming apparatus main body 100 is an intermediate transfer type color image forming apparatus that utilizes electrophotographic process technology. That is, the image forming apparatus main body 100 primarily transfers the toner images of each color, CMYK, formed on a photoconductor onto an intermediate transfer body, and then superimposes the four color toner images on the intermediate transfer body, and then secondarily transfers them onto paper to form an image. CMYK stands for C (cyan), M (magenta), Y (yellow), and K (black).

[0014] The image forming apparatus main body 100 employs a tandem system in which photoconductors corresponding to the four colors, CMYK, are arranged in series in the running direction of the intermediate transfer body, and toner images of each color are transferred sequentially to the intermediate transfer body in a single step.

[0015] As shown in FIG. 2, the image forming apparatus 1 includes an image processing unit 10, an image forming unit 20, a fixing unit 30, a paper transport unit 40, a communication unit 71, a memory unit 72, a control unit 200, a paper feed unit 300, a buffer unit 400, an image reading unit 500, a paper discharge unit 600, and the like.

[0016] The control unit 200 includes a CPU (Central Processing Unit) 201, a ROM (Read Only Memory) 202, and a RAM (Random Access Memory) 203. The CPU 201 reads out a program corresponding to the processing contents from the ROM 202, loads it in the RAM 203, and centrally controls the operation of each block of the image forming apparatus 1 in cooperation with the loaded program. At this time, various data such as a LUT (Look Up Table) stored in the storage unit 72 is referenced. The storage unit 72 is configured, for example, with a non-volatile semiconductor memory (so-called flash memory) or a hard disk drive.

[0017] The control unit 200 transmits and receives various data to and from an external device (e.g., a personal computer) connected to a communication network such as a LAN (Local Area Network) or a WAN (Wide Area Network) via the communication unit 71. The control unit 200 receives, for example, image data transmitted from an external device, and forms an image on a sheet based on this image data (input image data). The communication unit 71 is formed, for example, of a communication control card such as a LAN card.

[0018] The control unit 200 is connected to an operation display unit (not shown), an image processing unit 10, an image forming unit 20, a fixing unit 30, a paper transport unit 40, a communication unit 71, a storage unit 72, a paper feed unit 300, a buffer unit 400, an image reading unit 500, and a paper discharge unit 600. These units execute predetermined processes based on instructions from the control unit 200.

[0019] The operation display unit is composed of, for example, a liquid crystal display (LCD) with a touch panel, and functions as a display unit and an operation unit. The display unit displays various operation screens, image status display, operation status of each function, etc., according to a display control signal input from the control unit 200. The operation unit has various operation keys such as a numeric keypad and a start key, accepts various input operations by the user, and outputs operation signals to the control unit 200.

[0020] The image processing unit 10 includes a circuit for performing image processing on input image data according to initial settings or user settings, etc. The image forming unit 20 is controlled based on the image data that has been subjected to image processing.

[0021] The image forming section 20 includes image forming units 21 (21Y, 21M, 21C, 21K), an intermediate transfer unit 22, a secondary transfer unit 23, etc. Based on image data from the image processing section 10, the image forming unit 21Y forms an image with Y component color toner. Similarly, the image forming unit 21M forms an image with M component color toner, the image forming unit 21C forms an image with C component color toner, and the image forming unit 21K forms an image with K component color toner.

[0022] The image forming units 21Y, 21M, 21C, and 21K have the same configuration. Specifically, the image forming units 21Y, 21M, 21C, and 21K each have an exposure device, a developing device, a photosensitive drum, a charging device, a drum cleaning device, etc. Since known techniques can be adopted for the exposure device, the developing device, the photosensitive drum, the charging device, and the drum cleaning device, detailed description thereof will be omitted here.

[0023] The intermediate transfer unit 22 includes an intermediate transfer belt and the like. The intermediate transfer belt is stretched in a loop shape around a number of support rollers and travels in the direction of arrow A. The support rollers include a backup roller, a primary transfer roller, a drive roller, and other rollers, but these are not shown here. The intermediate transfer belt is pressed against a photosensitive drum, thereby transferring a toner image from the photosensitive drum to the intermediate transfer belt.

[0024] The intermediate transfer unit 22 may be configured to include a belt cleaning device having a plate-shaped belt cleaning blade that is in sliding contact with the surface of the intermediate transfer belt. The belt cleaning device removes residual toner and the like that remains on the surface of the intermediate transfer belt after the secondary transfer.

[0025] The secondary transfer unit 23 includes a secondary transfer roller, etc. The secondary transfer roller is in pressure contact with the intermediate transfer belt, so that a secondary transfer nip is formed between the intermediate transfer belt and the secondary transfer roller.

[0026] In the secondary transfer unit 23, when the paper is transported to the secondary transfer nip, the toner images of each color carried on the intermediate transfer belt are transferred onto the paper at once. The paper onto which the toner images have been transferred is transported toward the fixing unit 30 by the secondary transfer roller.

[0027] Incidentally, the secondary transfer unit 23 may be a belt-type secondary transfer unit having a secondary transfer belt stretched around a plurality of support rollers, instead of a roller-type secondary transfer unit having a secondary transfer roller or the like.

[0028] The fixing unit 30 includes a fixing roller, a pressure roller, etc. The fixing roller is heated to a predetermined fixing temperature, and the pressure roller forms a fixing nip between the fixing roller and the pressure roller to sandwich and transport the paper. In the fixing unit 30, the toner image is fixed to the paper by heating and pressurizing the paper, which has been secondarily transferred and transported, in the fixing nip.

[0029] The paper transport section 40 includes a paper feed transport section 41, a transport path section 42, and a paper discharge transport section 43. The paper feed transport section 41, the transport path section 42, and the paper discharge transport section 43 are each composed of, for example, a plurality of transport rollers and a drive motor that rotates and drives these. The paper feed transport section 41 transports the paper sent out from the paper feed section 300 to the transport path section 42. The transport path section 42 transports the paper to the image forming section 20, where an image is formed. Thereafter, the paper discharge transport section 43 transports the paper that has been subjected to a fixing process in the fixing section 30 to the buffer section 400.

[0030] The paper feed unit 300 is disposed upstream of the image forming apparatus main body 100 in the paper transport direction D, which is the direction in which paper is transported, and is connected to the image forming apparatus main body 100. The paper feed unit 300 has a plurality of paper feed trays, and each paper feed tray stores paper sheets (standard paper, special paper) identified based on basis weight, size, etc., by preset type. The paper feed unit 300 feeds and supplies the specified paper to the paper feed transport unit 41 of the image forming apparatus main body 100 based on an instruction from the image forming apparatus main body 100.

[0031] The buffer unit 400 is disposed downstream of the image forming apparatus main body 100 in the paper conveying direction D, and is connected to the image forming apparatus main body 100. The buffer unit 400 is provided between the image forming apparatus main body 100 and the image reading unit 500, and is an adjustment device for absorbing a speed difference between the paper conveying speed in the image forming apparatus main body 100 and the paper conveying speed in the image reading unit 500. A similar adjustment device may be provided between the paper feeding unit 300 and the image forming apparatus main body 100. The buffer unit 400 is not an essential component, and the image reading unit 500 may be connected to the image forming apparatus main body 100 without the buffer unit 400.

[0032] The image reading unit 500 is disposed downstream of the buffer unit 400 in the paper conveying direction D, and is connected to the buffer unit 400. The image reading unit 500 has detection units 501 and 502 that detect the positions of a plurality of detection images (see FIG. 3A and FIG. 3B) formed on the paper by the image forming apparatus main body 100. The detection unit 501 (first detection unit) is disposed to read the detection image on the front side of the paper being conveyed, and the detection unit 502 (second detection unit) is disposed to read the detection image on the back side of the paper. Details of the detection units 501 and 502 will be described later with reference to FIG. 3A and FIG. 3B. The image reading unit 500 is used for image alignment using the detection images, but is also used for inspection of defects in the formed image and various calibrations.

[0033] The paper discharge unit 600 is disposed downstream of the image reading unit 500 in the paper transport direction D, and is connected to the image reading unit 500. The paper discharge unit 600 discharges the paper transported from the image reading unit 500 to the outside of the machine, and places the paper on a paper discharge tray 601.

[0034] In the image forming apparatus 1, the image forming apparatus main body 100 changes the image formation conditions and corrects the position of the image formation depending on the distance between the position of the detection image read by the detection units 501 and 502 and the edge of the paper, thereby aligning the image.

[0035] Incidentally, in conventional image reading devices, the larger the paper size in the main scanning direction, the wider the width of the image reading device in the main scanning direction had to be. In other words, in order to read the detection image formed on the four corners and ends of a large-sized paper, the width of the image reading device in the main scanning direction had to be wider. This resulted in a problem that the image reading device itself became larger, leading to higher device costs. In order to prevent the image reading device from becoming larger, a method of placing two relatively small image reading devices on both sides of the paper in the main scanning direction could be considered, but there was a problem that the increased number of image reading devices would result in higher device costs.

[0036] Therefore, in this embodiment, the image reading unit 500 of the image forming apparatus 1 includes detection units 501 and 502 that detect the positions of a plurality of detection images formed at different positions in the main scanning direction of the paper by the image forming apparatus main body 100. The detection units 501 and 502 each have a detection range in the main scanning direction that is equal to or smaller than the width of the paper.

[0037] The detection units 501 and 502 will be specifically described with reference to Fig. 3A and Fig. 3B. The detection unit 501 is disposed above the sheet S so as to read the detection images M11 to M14 on the front side of the sheet S transported in the sheet transport direction D (sub-scanning direction). The detection unit 502 is disposed below the sheet S so as to read the detection images M21 to M24 on the back side of the sheet S. Here, the detection unit 501 is disposed downstream of the detection unit 502 in the sheet transport direction D. The detection units 501 and 502 are disposed so as to straddle one end E of the sheet S in the main scanning direction.

[0038] In the main scanning direction, the width of the detection units 501 and 502 is equal to or less than the width of the paper S, but may be less than the width of the paper S. Furthermore, if the image forming apparatus 1 is capable of transporting paper of multiple sizes, the width of the detection units 501 and 502 in the main scanning direction is equal to or less than the width of the largest paper S that can be used by the image forming apparatus 1, but may be less than the width of the paper S.

[0039] The detection units 501 and 502 cannot read the entire width of, for example, the maximum size of paper S that can be used in the image forming apparatus 1. Therefore, the detection images M11 to M14 and M21 to M24 detected by the detection units 501 and 502 are formed within the detection range R of the paper S, rather than being formed at the four corners of the paper S.

[0040] For example, on the front side of the sheet S, the detection images M11 and M13 are formed on one end E1 side of the sheet S, while the detection images M12 and M14 are formed at a position away from the other end E2 of the sheet S, within the detection range R of the sheet S. This is similar to the detection images M21-M24 formed on the back side of the sheet S. Note that, although the detection images M11-M14 and M21-M24 are cross-shaped images here, they may be images of other shapes as long as their positions can be detected.

[0041] Further, here, in order to align the images, four detection images M11-M14 are formed on the front side of the paper S and four detection images M21-M24 are formed on the back side, but it is sufficient that the detection images are formed on either the front side or the back side of the paper S. Also, it is sufficient that the detection images are formed in three or more locations on either the front side or the back side of the paper S that differ in position in at least one of the main scanning direction and the sub-scanning direction. As an example, two of the three detection images are arranged on the same line in the main scanning direction, and two of the three detection images are arranged on the same line in the paper transport direction D.

[0042] In this manner, in the present embodiment, the width of the detection units 501, 502 in the main scanning direction is set to be equal to or less than the width of the paper S, and detection images M11-M14, M21-M24 are formed within the detection range R of the paper S in the main scanning direction. Therefore, compared to the conventional device shown in Patent Document 1, the width of the detection units 501, 502 can be made smaller, which allows the size of the detection units 501, 502 to be reduced, and the cost of the device to be reduced.

[0043] As such detection units 501 and 502, a CIS or a CCD (Charge-Coupled Device) using an optical system, a camera, or the like can be used.

[0044] Next, an image alignment method using the image reading unit 500 having the above-mentioned detection units 501 and 502 will be described with reference to Fig. 4 together with Fig. 3B. Fig. 4 is a flowchart illustrating the image alignment method using the image reading unit 500.

[0045] (Step S11) The control unit 200 controls the paper feed unit 300 to feed the paper S to the image forming unit 20 of the image forming apparatus main body 100 .

[0046] (Step S12) The control unit 200 controls the image forming unit 20 to form the detection images M11 to M14 and M21 to M24 on the fed paper S. At this time, the image forming unit 20 forms the detection images M11 to M14 and M21 to M24 within the detection range R of the paper S, as described above.

[0047] (Step S13) The control unit 200 controls the image reading unit 500 to detect the positions of the ends E1 and E3 and the detection images M11-M14 and M21-M24 of the sheet S transported to the image reading unit 500 via the fixing unit 30 and the buffer unit 400. Here, the end E3 is the end on the downstream side in the sheet transport direction D.

[0048] The detection units 501 and 502 of the image reading unit 500 detect the positions of the ends E1 and E3 and the detection images M11 to M14 and M21 to M24, for example, by detecting a change in the amount of light reflected by the paper S. For the ends E1 and E3, the amount of reflected light changes depending on whether the paper S is present, and for the detection images M11 to M14 and M21 to M24, the amount of reflected light changes depending on whether or not those image portions exist. Therefore, by detecting such a change in the amount of reflected light with the detection units 501 and 502, it is possible to detect the positions of the ends E1 and E3 and the detection images M11 to M14 and M21 to M24.

[0049] (Step S14) The control unit 200 (calculation unit) calculates the distances between the ends E1, E3 of the paper S and the detection images M11 to M14, M21 to M24.

[0050] Now, with reference to FIG. 3B, calculation of the distances between the ends E1, E3 of the paper S and the detection images M11 to M14, M21 to M24 will be described.

[0051] The detection unit 501 detects the positions of the end E1 of the paper S and the image for detection M11, and the control unit 200 calculates the distance X1 between the end E1 of the paper S and the image for detection M11 in the main scanning direction of the paper S. The detection unit 501 also detects the positions of the end E1 of the paper S and the image for detection M12, and the control unit 200 calculates the distance X2 between the end E1 of the paper S and the image for detection M12 in the main scanning direction of the paper S. In this way, the control unit 200 calculates the distances X1 and X2 to the images for detection M11 and M12 based on the end E1 in the main scanning direction of the paper S. This is the same for the images for detection M13 and M14, and also for the images for detection M21 to M24 detected by the detection unit 502.

[0052] Furthermore, the detection unit 501 detects the position of the end E3 of the paper S (the end on the downstream side in the paper transport direction D) and the detection image M11, and the control unit 200 calculates the distance Y1 between the end E3 of the paper S and the detection image M11 in the paper transport direction D (sub-scanning direction). Furthermore, the detection unit 501 detects the position of the end E3 of the paper S and the detection image M12, and the control unit 200 calculates the distance Y2 between the end E3 of the paper S and the detection image M12 in the paper transport direction D. In this way, the control unit 200 calculates the distances Y1 and Y2 to the detection images M11 and M12 based on the end E3 in the paper transport direction D. This is the same for the detection images M13 and M14, and also for the detection images M21 to M24 detected by the detection unit 502. In the case of the detection images M13, M14, M23, and M24, the distance to the detection images M13, M14, M23, and M24 may be calculated using the end E4 of the paper S (the end on the upstream side in the paper transport direction D) as a reference.

[0053] (Step S15) The control unit 200 checks whether the calculated distances (e.g., distances X1, X2, Y1, Y2) are within a predetermined range of a predefined reference value, and if they are within the predetermined range (YES), proceeds to step S16, and if they are not within the predetermined range (NO), proceeds to step S17. The reference values ​​are defined for each of the detection images M11 to M14 and M21 to M24. For example, the center position of the detection image M11 is defined in advance (predefined position). Then, in the main scanning direction, the distance from the end E1 to the defined position is defined as the reference value for the distance X1, and in the sub-scanning direction, the distance from the end E3 to the defined position is defined as the reference value for the distance Y1. The same reference values ​​as above are defined for the other detection images M12 to M14 and M21 to M24.

[0054] (Step S16) If the calculated distances (e.g., distances X1, X2, Y1, Y2) are within a predetermined range of the reference value, the control unit 200 notifies the user that the image position is OK and ends the image position alignment method. The control unit 200 notifies the user that the image position is OK by voice or screen display using, for example, a speaker or a display unit provided in the image forming apparatus 1.

[0055] (Step S17) If the calculated distance (for example, distances X1, X2, Y1, Y2) is not within a predetermined range of the reference value, the control unit 200 calculates the difference (amount of positional deviation) between the measured distance and the reference value.

[0056] (Step S18) Based on the calculated difference, the control unit 200 changes the image forming conditions related to the image forming positions in the image forming unit 20, changes the positions at which the detection images M11-M14, M21-M24 are formed, and returns to step S11. That is, the control unit 200 repeats the formation, detection, and position change of the detection images until the calculated distances (e.g., distances X1, X2, Y1, Y2) fall within a predetermined range of the reference value. The image forming conditions related to the image forming positions include, for example, the start timing of image formation in the main scanning direction and the sub-scanning direction, and the image forming positions are changed by changing the start timing of image formation.

[0057] Here, the above steps S15, S17, and S18 will be explained by calling the reference value for distance X1 X01, the reference value for distance X2 X02, the reference value for distance Y1 Y01, and the reference value for distance Y2 Y02.

[0058] For example, for image positioning in the main scanning direction on the detection image M11 side of the paper S (upper left side in FIG. 3B), the distance X1 from the end E1 of the paper S to the detection image M11 is calculated, and it is determined whether the distance X1 is within a predetermined range of the reference value X01. If the distance X1 is outside the predetermined range of the reference value X01, the difference between the distance X1 and the reference value X01 is calculated, and the image formation position is changed by changing the image formation conditions so that the distance X1 falls within the predetermined range of the reference value X01.

[0059] Similarly, for image positioning in the main scanning direction on the detection image M12 side of the paper S (upper right side in FIG. 3B), the distance X2 from the end E1 of the paper S to the detection image M12 is calculated, and it is determined whether the distance X2 is within a predetermined range of the reference value X02. If the distance X2 is outside the predetermined range of the reference value X02, the difference between the distance X2 and the reference value X02 is calculated, and the image formation position is changed by changing the image formation conditions so that the distance X2 falls within the predetermined range of the reference value X02.

[0060] The main scanning direction image alignment of the detection image M13 side (lower left side in FIG. 3B) and the detection image M14 side (lower right side in FIG. 3B) of the paper S is similar to the detection images M11 and M12. In this manner, the image alignment in the main scanning direction is based on the edge E1 of the paper S.

[0061] For image positioning in the paper transport direction D on the detection image M11 side of the paper S (upper left side in FIG. 3B), the distance Y1 from the end E3 of the paper S to the detection image M11 is calculated, and it is determined whether the distance Y1 is within a predetermined range of the reference value Y01. If the distance Y1 is outside the predetermined range of the reference value Y01, the difference between the distance Y1 and the reference value Y01 is calculated, and the image formation position is changed by changing the image formation conditions so that the distance Y1 falls within the predetermined range of the reference value Y01.

[0062] Similarly, for image registration in the paper transport direction D on the detection image M12 side of the paper S (upper right side in FIG. 3B), the distance Y2 from the end E3 of the paper S to the detection image M12 is calculated, and it is determined whether the distance Y2 is within a predetermined range of the reference value Y02. If the distance Y2 is outside the predetermined range of the reference value Y02, the difference between the distance Y2 and the reference value Y02 is calculated, and the image formation position is changed by changing the image formation conditions so that the distance Y2 falls within the predetermined range of the reference value Y02.

[0063] Image position alignment in the paper conveying direction D on the detection image M13 side (lower left side in FIG. 3B) and the detection image M14 side (lower right side in FIG. 3B) of the paper S is similar to that of the detection images M11 and M12. Note that the position alignment on the detection images M13 and M14 sides may be based on the above-mentioned edge E4 of the paper S.

[0064] Here, the detection images M11 to M14 formed on the front side of the sheet S have been described, but similar image alignment can be performed for the detection images M21 to M24 formed on the back side of the sheet S. This allows image alignment to be performed not only on the front side of the sheet S, but also on the back side.

[0065] In this way, the image formation positions are changed based on the positions (detection results) of the detection images M11-M14 formed on the front side of the paper S. This makes it possible to correct misalignment in the main scanning direction, sub-scanning direction, and rotation direction, and magnification in the main scanning direction and sub-scanning direction, for the image formed on the front side of the paper S. Similarly, the image formation positions are changed based on the positions (detection results) of the detection images M21-M24 formed on the back side of the paper S. This makes it possible to correct misalignment in the main scanning direction, sub-scanning direction, and rotation direction, and magnification in the main scanning direction and sub-scanning direction, for the image formed on the back side of the paper S.

[0066] The above-mentioned image alignment may be performed when adjusting the image forming apparatus 1 (at a time other than when printing), or may be performed for each sheet of paper during printing. In this case, in the above-mentioned step S12, the image for printing is also formed on the sheet S together with the images for detection M11-M14, M21-M24. Then, in the above-mentioned step S18, the image formation position of the image for printing is changed together with the images for detection M11-M14, M21-M24. In this way, since the image formation position is changed for each sheet of paper, the accuracy of correction of the above-mentioned positional deviation in the main scanning direction, sub-scanning direction, and rotational direction and the magnification in the main scanning direction and sub-scanning direction is improved, and real-time correction can be performed.

[0067] As described above, in the image forming apparatus 1 of this embodiment, the image reading unit 500 includes detection units 501 and 502 that detect the positions of a plurality of detection images formed at different positions in the main scanning direction of a sheet of paper by the image forming apparatus main body 100. The detection units 501 and 502 each have a detection range in the main scanning direction that is equal to or smaller than the width of the sheet of paper.

[0068] According to the image forming apparatus 1 of the present embodiment configured as described above, the width of the detection units 501 and 502 in the main scanning direction can be reduced, so that the cost of the apparatus can be reduced. Then, the image can be aligned by using the detection units 501 and 502 whose width in the main scanning direction is reduced.

[0069] In the above embodiment, the control unit 200 functions as a calculation unit that calculates the distances between the ends E1, E3 of the paper S and the detection images M11-M14, M21-M24 and the differences between the distances and the reference values, but this calculation unit may be provided in the image reading unit 500. In that case, the control unit 200 may change the image forming position based on the differences calculated by the image reading unit 500.

[0070] Furthermore, in the above embodiment, the detection units 501 and 502 do not need to detect the entire surface of the sheet S, and may detect only the portions on which the detection images M11 to M14 and M21 to M24 are formed.

[0071] In the above embodiment, the image reading unit 500 includes the detection unit 501 and the detection unit 502, but the image reading unit 500 may include only one of the detection unit 501 and the detection unit 502. For example, in the case of a configuration including the detection unit 501, the detection images M11 to M14 are formed on the front side of the sheet S, and in the case of a configuration including the detection unit 502, the detection images M21 to M24 are formed on the back side of the sheet S.

[0072] Also, in the above embodiment, the image reading unit 500 is configured as a separate device independent of the image forming apparatus main body 100, but the image reading unit 500 may be disposed between the fixing unit 30 and the paper discharge conveying unit 43 and incorporated inside the image forming apparatus main body 100.

[0073] In the above embodiment, the image forming apparatus 1 does not have an automatic document feeder called an ADF (Auto Document Feeder) or an original image scanning device called a scanner, but may have these. In this case, the automatic document feeder automatically and continuously transports multiple documents to the original image scanning device, which continuously reads images (including both sides) of the transported documents to generate input image data. This input image data is input to the image processing unit 10.

[0074] It should be noted that the above-mentioned embodiments are merely examples of the implementation of the present invention, and the technical scope of the present invention should not be interpreted as being limited by these embodiments. In other words, the present invention can be implemented in various forms without departing from the gist or main characteristics of the present invention. [Explanation of symbols]

[0075] 1. Image forming device 10 Image processing section 20 Image forming section 30 Fixing section 40 Paper transport section 100 Image forming apparatus body 200 Control section 300 Paper feed section 400 Buffer section 500 Image reading unit 600 Paper output section

Claims

1. a detection unit that detects positions of a plurality of detection images formed at different positions on a recording medium in a main scanning direction perpendicular to a conveying direction of the recording medium by an image forming apparatus; a control unit that determines positions of the plurality of detection images in a main scanning direction based on a detection result by the detection unit; Equipped with the detection unit has a detection range in the main scanning direction that is equal to or smaller than a width of the recording medium, the control unit calculates a distance to each of the detection images based on a same end portion in the main scanning direction of the recording medium, based on a detection result by the detection unit, thereby determining each position of the plurality of detection images in the main scanning direction. Image reading device.

2. the detection range is equal to or smaller than the width of the maximum recording medium that can be used in the image forming apparatus; 2. The image reading device according to claim 1.

3. the detection unit is disposed so as to straddle one end of the recording medium in the main scanning direction; 3. The image reading device according to claim 1 or 2.

4. the control unit calculates a distance between an end of the recording medium and the detection image in a sub-scanning direction which is the transport direction; The image reading device according to claim 1 .

5. The control unit calculates a positional deviation amount between the detection image and a predetermined specified position based on the calculated distance. The image reading device according to claim 1 .

6. the detection image is formed on at least one of the front surface and the back surface of the recording medium at three or more positions that are different in at least one of the main scanning direction and the sub-scanning direction that is the transport direction; The image reading device according to claim 1 .

7. The detection unit is a first detection unit that detects a position of the detection image formed on the surface of the recording medium; a second detection unit that detects the position of the detection image formed on the back surface of the recording medium; having The image reading device according to claim 1 .

8. an image forming unit that forms an image on a recording medium; An image reading device according to any one of claims 1 to 7; Equipped with the image reading device detects a position of the detection image formed on the recording medium by the image forming unit; Image forming device.

9. the image forming unit changes a position where the image is formed on the recording medium in accordance with a detection result of the position of the detection image by the image reading device. The image forming apparatus according to claim 8.

10. the image reading device detects a position of the detection image for each of the recording media; the image forming unit changes a position where the image is formed for each of the recording media in response to the detection result. The image forming apparatus according to claim 9 .

Images