Image forming device

Abstract

To guide a placement position of a sheet, the sheet in which an image is formed only on a first surface.SOLUTION: An image forming apparatus comprises an image reading unit that, in a state in which a sheet having an image 601 for detection formed on a first surface is arranged in an attitude in which the first surface is directed to transparent glass 250 and at a position at which the ends of the sheet are separated from the ends of the transparent glass 520, and the sheet is covered by covering paper 500 placed at a predetermined position on the transparent glass 520, reads the ends of the sheet placed in a state in which part in a longitudinal direction of the sheet protrudes from the transparent glass 520 and a first edge 504 of the covering paper 500 and the image 601 for detection. An image 503 for alignment is formed on the covering paper 500. An image 603 for alignment on the sheet is arranged at a position protruding from the covering paper 500 on the first surface of the sheet. The image forming apparatus aligns the image 603 for alignment with the image 503 for alignment on the covering paper 500 before reading the image 601 for detection.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] When measuring the position of an image formed on a sheet of paper relative to that sheet of paper, it is necessary to measure the position using the edge of the sheet of paper as a reference.

[0003] To read an image on a sheet of paper, a table (e.g., the glass table of a flatbed scanner) is used, and the image formed on the surface of the sheet of paper placed on the table, facing the table, is read. If the sheet is abutted against the edge of the table to read the image, the edge of the sheet cannot be measured properly. Therefore, to measure the position of the image relative to the sheet of paper, it is necessary to read the image while the sheet is placed away from the edge of the table, i.e., at a position where there is a gap between the edge of the table and the sheet of paper.

[0004] On the other hand, if the paper is moved too far away from the edge of the placement table, a problem occurs in that part of the paper falls outside the reading area on the placement table.

[0005] Patent document 1 proposes covering the paper placed on a loading platform with cover paper, and adjusting the position of the paper relative to the loading platform using an alignment image formed on the cover paper and an alignment image formed on the second side of the paper, which is the reverse side of the first side facing the loading platform. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5974699 Summary of the Invention [Problem to be solved by the invention]

[0007] By adopting the proposal in the above-mentioned Patent Document 1, the paper can be placed at a predetermined position on the placement table, which prevents the problem of part of the paper falling outside the reading area on the placement table.

[0008] However, this proposal involves forming images on both sides of a sheet of paper, and using an image on the second side for alignment when reading the image on the first side, which means that it is necessary to form images on both sides of a sheet of paper.

[0009] However, when forming images on both sides of a sheet of paper, for example, there is a limit to the longitudinal length of the sheet, and there are image forming devices that can only form an image on one side of long sheets of paper that exceed this limit. Measurement of the image position needs to be performed for each type of paper, and measurement is also required for sheets of paper that can only form an image on one side. Alternatively, there are also image forming devices that originally form an image on only one side of a sheet of paper.

[0010] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide an image forming apparatus capable of guiding the placement position of a sheet of paper relative to a placement table, even if the sheet of paper has an image formed on only one side thereof. [Means for solving the problem]

[0011] First aspectthe image forming apparatus includes a placing table for placing an object whose image is to be read, an image forming unit for forming an image on a first side of a sheet of paper, including a first image for measuring the relative position with respect to an end of the sheet of paper, an image reading unit for reading the image placed on the placing table, and a position correction unit for correcting the relative position of the image formed on the sheet of paper with respect to the sheet of paper based on the reading result by the image reading unit, wherein when the first side of the sheet of paper on which the first image has been formed is placed on the placing table with the end of the sheet of paper facing the placing table and away from the end of the placing table, and the sheet of paper is further covered with a cover paper, when the end of the sheet of paper and the image formed on the first side of the sheet of paper are read by the image reading unit, a part of the sheet of paper is placed in a state where it protrudes from the placing table and the first edge of the cover paper, and the image forming unit forms a third image on the first side of the sheet of paper as an object for alignment, the third image being the object for alignment, the second image for alignment formed on the surface of the cover paper opposite to the surface where the cover paper contacts the sheet of paper.

[0012] Second aspect the image forming unit forms, as the third image, both a first third image for alignment when an image formed in an area including a first end of the paper is read by the image reading unit, and a second third image for alignment when an image formed in an area including a second end of the paper is read by the image reading unit, on the first surface of the paper. First aspect The image forming apparatus according to claim 1,

[0013] Third aspect The image forming unit forms the first third image and the second third image, which are visually different from each other, on the first surface of the paper. In the second aspect The image forming apparatus is as described above.

[0014] Fourth aspect the first third image is an image consisting of one shape arranged in a position facing the second image across the first edge, and the second third image is an image consisting of two shapes arranged in a direction intersecting the first edge and arranged in a position facing the second image across the first edge. In the third aspectThe image forming apparatus is as described above.

[0015] Fifth aspect the image forming unit forms, on the first surface of the paper, in addition to the first image and the third image, a fourth image for position adjustment in a direction intersecting with the first edge, which is required to be overlapped with the first edge. Any one of the first to fourth aspects The image forming apparatus according to claim 1,

[0016] Sixth aspect the image forming unit forms, as the fourth image, both a first fourth image for alignment in a direction intersecting with the first edge when an image formed in an area including a first end of the paper is read by the image reading unit, and a second fourth image for alignment when an image formed in an area including a second end of the paper is read by the image reading unit, on the first surface of the paper. Fifth aspect The image forming apparatus according to claim 1,

[0017] Seventh aspect The image forming unit forms an image on a second sheet of paper different from a first sheet of paper on which an image including the first image is formed, so that the second sheet of paper is used as the cover sheet. Any one of the first to sixth aspects The image forming apparatus according to claim 1,

[0018] Eighth aspect the image forming unit forms an image in a color that is differentiated from the color of the first sheet on a portion of a first surface of the second sheet that overlaps with an edge of the first sheet when the first sheet is covered, and forms the second image on a second surface of the second sheet. Seventh aspect The image forming apparatus according to claim 1,

[0019] Ninth aspect The image forming unit forms the second image on a second sheet of paper having a color that is distinct from the color of the first sheet of paper, the second image being formed in a color that is distinct from the color of the second sheet of paper. Seventh aspect The image forming apparatus according to claim 1, Effect of the Invention

[0020] First aspectAccording to the image forming apparatus, it is possible to guide the placement position of the paper with respect to the placement table even when the paper has an image formed on only one side.

[0021] Second aspect According to the image forming apparatus, accurate measurements are taken of two areas on the paper, including each edge.

[0022] Third and fourth aspects According to the image forming apparatus, it is possible to easily know which area of ​​the image on the paper is currently being measured.

[0023] Fifth and Sixth Aspects According to this image forming apparatus, the paper can be placed in the correct position more easily than in a case where the fourth image is not formed.

[0024] Seventh, eighth and ninth aspects According to the imaging apparatus, a cover sheet can be generated by the imaging apparatus when necessary. [Brief description of the drawings]

[0025] [Figure 1] 1 is a diagram showing the overall configuration of an image forming apparatus according to an embodiment of the present invention; [Diagram 2] FIG. 13 is a diagram showing a screen displayed on a touch panel display screen. [Diagram 3] FIG. 13 is a diagram showing a screen displayed on a touch panel display screen. [Figure 4] FIG. [Diagram 5] 10A and 10B are diagrams illustrating a state of paper registration when a chart image is read. [Figure 6] FIG. 13 is a diagram showing a long sheet of paper on which a chart image of a second example is formed. [Figure 7] FIG. 13 is a diagram showing a large-sized sheet on which a chart image is formed. [Figure 8] FIG. 11 shows a cover paper of a second example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] FIG. 1 is a diagram showing the overall configuration of an image forming apparatus according to an embodiment of the present invention.

[0027] This image forming apparatus is a copier that has a double-sided output function in addition to a single-sided output function.

[0028] This image forming apparatus 10 is equipped with an image reading unit 200 that reads an image on paper and generates image data representing the image, an image forming unit 100 that forms the image read based on the image data on another sheet of paper, and an operation unit 270 that receives various image formation information input from the user, such as the number of sheets to be output, selection of double-sided / single-sided output, and specification of a tray for storing paper before image output.

[0029] The operation unit 270 is provided with a touch panel display screen 2701, and a button group 2702 including various buttons such as a start button for instructing the start of image reading and image formation, numeric buttons for inputting numeric values ​​when specifying the number of sheets to be output, and buttons for controlling the image forming apparatus. The button group 2702 also includes a correction amount calculation mode button 2702a for setting the image forming apparatus 10 to a correction amount calculation mode for calculating various correction amounts, such as the amount of correction for the image formation position on the paper and the amount of correction for the magnification of the image on the paper, when forming an image on the paper. This correction amount calculation will be described in detail later.

[0030] The image reading unit 200 includes an upper cover 260 that is opened and closed by the user, and a transparent glass 250 that is disposed directly below the upper cover 260. The image reading unit 200 further includes an element below the transparent glass 250 for reading an image on a sheet of paper.

[0031] The image reading unit 200 has a first carriage 210, a second carriage 220, a lens unit 230, and a CCD line sensor 240 as elements for reading an image. The first carriage 210 has a first mirror 212 and a lamp 211, and is an element that can move in the left-right direction in FIG. 1. The first carriage 210 has a role of irradiating light onto an image to be read by the lamp 211 and receiving the reflected light. The second carriage 220 has a second mirror 221 and a third mirror 222, and is an element that can move in the left-right direction in the figure like the first carriage 210. The second carriage 220 and the lens unit 230 have a role of guiding the reflected light received by the first carriage 210 to the CCD line sensor 240. The CCD line sensor 240 also has a role of receiving the reflected light and generating image data representing the image.

[0032] Here, the image reading unit 200 has a transport reading mode and a stationary reading mode as reading modes for reading an image on a sheet of paper. In the transport reading mode, the sheets of paper 300' placed on the document tray 261 are drawn one by one from the paper feed port 260a, and are transported by a mechanism (not shown) to the discharge port 260b through a transport path indicated by a dashed line arrow. In this transport reading mode, the image on the sheet of paper being transported is read using the stationary first carriage 210, and the sheet is sent onto the sheet discharge tray 262. In the stationary reading mode, the sheet of paper is stopped on the transparent glass 250, and is read using the first carriage 210 that moves in the direction of the solid line arrow in the figure. In this stationary reading mode, the surface of the transparent glass 250 facing the upper cover 260 serves as a placement tray on which the sheet of paper 300 having an image to be read is placed. Here, the top cover 260 is opened, the side of the paper 300 bearing the image to be read is placed on the transparent glass 250 with the side facing downward in Fig. 1, and the top cover 260 is closed to press the paper 300 from above. In stationary reading mode, the first carriage 210 moves in this state while irradiating the paper 300 on the transparent glass 250, and the image on the paper 300 is read. When the first carriage 210 moves, the second carriage 220 also moves in the same direction at half the speed of the first carriage 210 so that the optical path length of the light reflected from the paper until it reaches the CCD sensor 240 is always kept constant.

[0033] The image forming section 100 includes image forming units 1K, 1C, 1M, and 1Y for forming images for each color of black (K), cyan (C), magenta (M), and yellow (Y), and an exposure section 5 for irradiating laser light. These image forming units 1K, 1C, 1M, and 1Y include stacked image carriers 11K, 11C, 11M, and 11Y for electrophotography, which rotate in the directions of arrows Bk, Bc, Bm, and By in FIG. 1, respectively. Here, in addition to the image carriers described above, each image forming unit is provided with a charger and a developer (not shown). The developer carrier in each image forming unit is charged by a charger (not shown) so that the surface potential reaches a predetermined potential, and the exposure section 5 performs raster scanning of the charged image carrier in the direction along the rotation axis of the rotating image carriers 11K, 11C, 11M, and 11Y with a laser beam, forming an electrostatic latent image on the image carrier due to the potential distribution. The electrostatic latent image is developed by electrostatically attaching toner in a developer containing charged toner to the electrostatic latent image by a developing device (not shown), and thus a developed image made of toner is formed on the image carrier.

[0034] Further, below each image forming unit 1 in Fig. 1, there is provided an intermediate transfer belt 2 which moves in the direction of arrow A in Fig. 1 in contact with each image carrier, and primary transfer rolls 110K, 110C, 110M, and 110Y are provided at positions facing each image carrier 11K, 11C, 11M, and 11Y across the intermediate transfer belt 2. This intermediate transfer belt 2 receives the transfer (primary transfer) of the developed image formed on each image carrier and carries the primary transfer image.

[0035] In addition to the image forming units 1K, 1C, 1M, and 1Y, the intermediate transfer belt 2, and the exposure unit 5, the image forming section 100 further includes a secondary transfer roll 3a that performs secondary transfer of the primary transfer image on the intermediate transfer belt 2 to paper, and a fixing device 4 that fixes the unfixed secondary transfer image transferred to the paper to the paper. In addition, a sensor 2a is provided near the intermediate transfer belt 2 to detect the test images of each color formed by each image forming unit and transferred to the intermediate transfer belt 2 when adjusting the relative positions and magnifications between the primary transfer images from each image carrier. In adjusting the relative positions and magnifications, the sensor 2a detects the test images of each color transferred to the intermediate transfer belt 2, and based on the detection results, the image forming units 1K, 1C, 1M, and 1Y are adjusted so that the relative positions and magnifications between the test images of each color are appropriate.

[0036] The image forming unit 100 also includes three trays, a first tray 70A, a second tray 70B, and a third tray 70C, each of which accommodates paper, and a drive roll 30 that drives the intermediate transfer belt 2. The intermediate transfer belt 2 is stretched around the drive roll 30 and multiple other rolls and moves in a circular manner in the direction of arrow A in FIG. 1 while receiving a driving force from the drive roll 30. The intermediate transfer belt 2 is pressed against the secondary transfer roll 3a by the backup roll 3b. The primary transfer image on the intermediate transfer belt 2 is secondarily transferred onto a sheet of paper that has been taken out of the first tray 70A, the second tray 70B, or the third tray 70C and transported to the secondary transfer roll 3a by the action of the secondary transfer roll 3a. The sheet of paper that has received the secondary transfer is further transported, and the secondary transfer image on the sheet is fixed onto the sheet by the fixing device 4, and then discharged onto the paper output tray 10. Here, a cleaning device 2b is provided near the intermediate transfer belt 2, and the toner remaining on the intermediate transfer belt 2 after the secondary transfer to paper is removed by this cleaning device 2b. Also, the test images of each color on the intermediate transfer belt 2, which are formed when adjusting the relative positions and magnifications between the primary transfer images from each image carrier as described above, are removed by this cleaning device 2b without being secondary transferred by the secondary transfer roll 3a.

[0037] The image forming apparatus 10 is provided with a controller 6 that controls each part in the image forming section 100. The controller 6 is provided with a read image memory 64 that stores image data generated by the CCD line sensor 240 of the image reading section 200 described above. In addition, in the image forming apparatus 10, deviations in the image forming position on the paper and changes in the magnification of the image occur due to differences in the timing of paper transport, the type of paper, and the route of paper transport. In this regard, as will be described later in detail, in the image forming apparatus 10, a chart image is formed on the paper, and the chart image (a detection image constituting the chart image) on the paper is read by the image reading section 200 to calculate various correction amounts such as the correction amount of the image forming position on the paper and the correction amount of the magnification of the image on the paper. For this reason, in addition to the read image memory 64 described above, the controller 6 is provided with a chart image memory 65 that stores chart image data representing a chart image used in the calculation of the correction amount described later. The chart image memory 65 stores chart image data for each paper size. The controller 6 also includes a cover sheet memory 66 that stores data for forming a cover sheet used when reading a chart image output on a sheet. The cover sheet memory 66 stores image data for the cover sheet according to the size of the sheet on which the chart image is formed. The cover sheet will be described later. The controller 6 also includes a first tray memory 61, a second tray memory 62, and a third tray memory 63 that store calculated correction amounts. These memories correspond to the first tray 70A, the second tray 70B, and the third tray 70C described above, respectively. The reason that memories for storing correction amounts are provided according to the trays is that the degree of deviation of the image formation position on the sheet and the change in the magnification of the image differ depending on the path through which the sheet is taken out of the tray. Here, each of the trays 70A, 70B, and 70C is configured to previously set what size or type of sheet is to be stored. Even if the power is turned on / off, the previous setting is valid unless the setting is changed. The present invention may also include a configuration for automatically detecting the size.

[0038] When forming an image based on image data stored in the read image memory 64 on a sheet of paper, the controller 6 reads out the correction amount from the memory corresponding to the tray designated by the user's operation via the operation unit 270, and performs various correction processes, such as correction of the image formation position and correction of the image magnification, on the image data stored in the read image memory 64 based on the read correction amount, and causes the exposure unit 5 to form an electrostatic latent image based on the image data that has been subjected to the correction process. Here, in the case of this embodiment, the correction amount for the first tray memory 61 and the second tray memory 62 consists of two types of correction amounts: a correction amount for the front side when forming an image on the front side in double-sided output, and a correction amount for the back side when forming an image on the back side in double-sided output. In image formation when double-sided output is specified, correction processing is performed on image data representing an image on the front side, which is the side on which an image is output first of both sides of the paper, based on the correction amount for the front side, and correction processing is performed on image data representing an image on the back side, which is the side on which an image is output second, based on the correction amount for the back side. On the other hand, in image formation when single-sided output is specified, correction processing is performed on image data based on the correction amount for the front side. However, in this embodiment, the third tray 70C contains paper that is too long to form images on both sides (herein referred to as long paper). Therefore, only the correction amount for the front side is stored in the third tray memory 63.

[0039] Next, a series of operations from reading an image to forming an image on a sheet will be described in the image forming apparatus 10. Here, the still reading mode will be described as an example.

[0040] When a user places a sheet of paper between the transparent glass 250 and the upper cover 260 with the side having the image to be read facing downward in Fig. 1, and further designates a tray for storing the sheets to be used for image formation, selects double-sided / single-sided output, designates the number of sheets to be output, etc., via the operation unit 270, and presses a start button (not shown) in the button group 2702 to instruct the start of image reading and image formation, light is emitted from the lamp 211 in the first carriage 210, and the light emitted by the lamp is reflected on the sheet of paper 300 via the transparent glass 250, and the reflected light passes through the first mirror 212 of the first carriage 210, the second mirror 221 and the third mirror 222 of the second carriage 220, and is imaged on the CCD line sensor 240 by the lens unit 230. In Fig. 1, the path of this light is indicated by a dotted arrow in the image reading unit 200. The first carriage 210 moves in the direction of the solid arrow (sub-scanning direction) in the image reading unit 200 while irradiating light from the lamp, and the second carriage 220 also moves in the same direction at half the moving speed of the first carriage 210. As a result, the entire image on the paper 300 is irradiated, and the reflected light reflected at any point of the image is imaged on the CCD line sensor 240 while keeping its optical path length constant. In this way, image data based on the reflected light of the entire image is generated by the CCD line sensor 240. Each generated image data undergoes various signal processing such as analog / digital conversion by a processing circuit (not shown), and is then sent to the controller 6 and stored in the read image memory 64 in the controller 6. Each time the user places the opposite side of the paper 300 or the side of a new paper with a new image on the transparent glass 250 and presses the start button, the generation of such image data and storage in the read image memory 64 are repeated.

[0041] The controller 6 reads out the correction amount from the memory corresponding to the specified tray among the first tray memory 61, the second tray memory 62, and the third tray memory 63 for the image data stored in the read image memory 64, and performs various correction processes such as correction process of the image formation position and correction process of the image magnification on the image data stored in the read image memory 64 based on the read correction amount. Then, the controller 6 controls the exposure section 5 to form an electrostatic latent image based on the image data subjected to the correction process on the charged image carriers 11K, 11C, 11M, and 11Y. The formed electrostatic latent image is developed by the developer in each image forming unit with toner in a developer containing toner of a color corresponding to each image forming unit, and a developed image of each color is formed. The developed images of each color thus formed in each image forming unit are sequentially transferred (primary transfer) onto the intermediate transfer belt 2 by the action of the primary transfer rolls 110K, 110C, 110M, and 110Y corresponding to each image carrier, and are superimposed to form a multi-color primary transfer image. Then, this multi-color primary transfer image is transported to the secondary transfer roll 3a by the intermediate transfer belt 2. Meanwhile, a sheet in a designated tray among the first tray 70A, the second tray 70B, and the third tray 70C is taken out in response to the formation of the multi-color primary transfer image, transported by the first transport roll pair 41a and the second transport roll pair 41b, and further aligned by the alignment roll pair 40. Furthermore, the alignment roll pair 40 sends out the paper so that it is sent to the position of the secondary transfer roll 3a in time with the arrival of the primary transfer image on the intermediate transfer belt 2, and the secondary transfer roll 3a transfers (secondarily transfers) the multi-color primary transfer image onto the sent out paper. The paper that has received the secondary transfer is further transported by the transport belt 31, and the fixing device 4 fixes the secondary transfer image on the paper. In FIG. 1, the paper transport path at this time is shown by the path indicated by the right-facing dotted arrow in the image forming unit 100. Note that any toner remaining on the intermediate transfer belt 2 after the secondary transfer onto the paper is removed by the cleaning device 2b.

[0042] When single-sided output is selected, the paper passes through this paper transport path only once, and the secondary transfer image is fixed in the fixing device 4, after which the paper passes through the delivery roll pair 40a and is discharged directly onto the paper output tray 10a.

[0043] On the other hand, when double-sided output is selected, the paper passes through the above-mentioned paper transport path indicated by the right-pointing arrow, whereby the secondary transfer image is transferred and fixed on one side of the paper, and then passes between the first double-sided transport roll pair 40b without heading toward the delivery roll pair 40a, and is transported downward through the path indicated by the downward dotted arrow. After that, the rotation direction of the second double-sided transport roll pair 40c is reversed, and the paper transport direction turns upward, and then passes through the third double-sided transport roll pair 40d and the fourth double-sided transport roll pair 40e through the path indicated by the left-pointing dotted arrow, and then passes through the first transport roll pair 41a, the second transport roll pair 41b, and the alignment roll pair 40, and heads again toward the secondary transfer roll 3a. Here, a new multi-color primary transfer image is formed on the intermediate transfer belt 2 in the above-mentioned manner from when the paper is first transferred by the secondary transfer roll 3a until it reaches the position of the secondary transfer roll 3a again. Then, when the paper reaches the secondary transfer roll 3a for the second time, the new multi-color primary transfer image is secondarily transferred to the second side of the paper, which is the reverse side of the first side that received the secondary transfer in the first time. The new secondary transfer image on the second side is then fixed by the fixing device 4, and the paper with fixed images formed on both sides is discharged onto the paper discharge tray 10a. Here, the toner remaining on the intermediate transfer belt 2 after the secondary transfer to the second side of the paper is removed by the cleaning device 2b.

[0044] When the third tray 70C is specified for image output, double-sided output cannot be specified due to limitations on the length of the paper transport path for double-sided output, and only single-sided output to the first side is possible on the paper stored in the third tray 70C.

[0045] The above is a description of the operation of the image forming apparatus 10, and the image thus read is formed on paper by the image forming apparatus 10.

[0046] The above explanation has been given using the example of the stationary reading mode, but when the transporting reading mode is adopted, the image reading and image formation are the same as those described above, except that the image on the paper being transported is read using the first carriage 210 in a stationary state.

[0047] In the above description, the image formation position on the paper is corrected by correcting the image formation position with respect to the image data, but the present invention may correct the image formation position on the paper instead of correcting the image by data processing on the image data. For example, the position correction of the entire image in the paper transport direction may be performed by controlling the alignment roll pair 40 to change the timing of sending the paper toward the secondary transfer roll 3a. In addition, the position correction of the entire image in the paper in a direction perpendicular to the paper transport direction may be performed by controlling the exposure unit 3 to change the writing position of the electrostatic latent image on each image carrier in the direction perpendicular to the paper transport direction (the direction of the rotation axis of each image carrier).

[0048] Here, in this image forming apparatus 10, it is possible to form an image on paper that is larger than the size that can be read by the image reading unit 200. In general, the reading range of the image reading unit 200 coincides with the size of the transparent glass 250 (i.e., the size of the mounting table). Even when an image is output onto paper that is larger than the size of the transparent glass 250 (i.e., the size of the mounting table), it is desirable that the image be accurately output at a predetermined position on the paper at a predetermined size (magnification), just as in the case of outputting an image onto paper that is smaller than the size of the transparent glass 250.

[0049] The calculation of the correction amount for the position, magnification, etc. of an image formed on a sheet will be described below.

[0050] In this image forming apparatus 10, the image forming unit 1K for black (K) is used to calculate the correction amounts of the image position, magnification, etc., which will be described below. Note that the correction amounts when the image forming units of other colors, cyan (C), magenta (M), and yellow (Y), are used can be obtained from the correction amount calculated using the image forming unit 1K for black (K) through the above-mentioned adjustment of the relative positions and magnifications between the primary transfer images formed by the image forming units of the four colors, including the image forming unit 1K for black (K).

[0051] In this image forming apparatus 10, a correction amount calculation mode button 2702a on the operation unit 270 in Fig. 1 is pressed, and thereby a correction amount calculation mode is set in the image forming apparatus 10. Here, in this image forming apparatus 10, the correction amount calculation is performed for each paper size, and each time the correction amount calculation mode button 2702a is pressed, the correction amount calculation mode for each paper size is switched to. Note that in this image forming apparatus 10, unless the correction amount calculation mode button 2702a is pressed, the normal mode in which image reading and image formation are performed in the above-mentioned manner is set, and this normal mode is the default mode when the image forming apparatus 10 is turned on.

[0052] This image forming apparatus 10 is provided with a mechanism for enabling calculation of correction amounts for image formation position, image magnification, and the like on paper larger than the area of ​​the transparent glass 250 (the area of ​​the mounting table). Here, there are two types of paper larger than the area of ​​the transparent glass 250. One is "long paper" which allows only single-sided output. The other is paper that allows double-sided output but is roughly the same size as the area of ​​the transparent glass 250 or larger (hereinafter, paper of this size will be referred to as "large size paper").

[0053] 1 holds paper smaller than the area of ​​the transparent glass 250 (referred to as "normal size paper"), the second tray 70B holds "large size" paper (e.g., A3 paper) that can be output on both sides, and the third tray 70C holds "long paper" that can only be output on one side. Below, first, a case will be described in which the correction amount is calculated using long paper that can be output on only one side and that is held in the third tray 70C.

[0054] As described above, in this image forming apparatus 10, the correction amount calculation is performed for each paper tray, i.e., for each paper size, and each time the correction amount calculation mode button 2702a is pressed, the correction amount calculation mode for each paper tray (each paper size) is switched to. Here, by pressing the correction amount calculation mode button 2702a on the operation unit 270 in Fig. 1 a predetermined number of times, the image forming apparatus 10 is set to a mode in which the correction amount for the image formation position on long paper stored in the third tray 70C is calculated.

[0055] FIG. 2 is a diagram showing a screen displayed on a touch panel display screen.

[0056] When a mode for calculating a correction amount for the image formation position on paper, image magnification, etc. is set, the screen shown in Fig. 2 is displayed on the touch panel display screen 2701 of Fig. 1. On this screen, three tray designation push buttons, a first tray designation push button 2701e, a second tray designation push button 2701f, and a third tray designation push button 2701g, for designating a tray containing paper on which a chart image is to be output, a chart image output instruction button 2701a for instructing output of a chart image, a read start push button 2701b for informing the image forming apparatus 10 that the user is about to make the image forming apparatus 10 read the chart image, a read completion push button 2701c for informing the image forming apparatus 10 that the user has completed the task of making the image forming apparatus 10 read the chart image, an ESC push button 2701d for returning from the correction amount calculation mode to the normal mode, and a cover paper output instruction button 2701h for instructing output of a cover paper are displayed as push buttons that receive contact with the user's finger. In this mode for calculating the correction amount for long sheets, only the tray designation push button corresponding to the tray storing long sheets can be selected, and the tray designation push button corresponding to the tray not storing long sheets cannot be selected. In the embodiment described here, since long sheets are stored only in the third tray 70C, the first tray designation push button 2701e and the second tray designation push button 2701f corresponding to the first tray 70A and the second tray 70BC not storing long sheets are displayed in dotted lines. This indicates that they cannot be selected even if the user touches them with their finger.

[0057] In order to calculate the correction amount for the long sheet, the third tray designation push button 2701g corresponding to the third tray 70C in FIG. 1 that accommodates the long sheet is pressed, and then the chart image output instruction button 2701a is pressed to execute the output of the chart image. By pressing the third tray designation push button 2701g, it is determined that the correction amount stored in the third tray memory 63 in FIG. 1 is used as the correction amount used when outputting the chart image. When the chart image output instruction button 2701a is pressed, in the image forming unit 100 in FIG. 1, the chart image data representing the chart image corresponding to the long sheet accommodated in the third tray 70C is read from the chart image memory 65 in FIG. 1, and correction processing is performed on the image formation position, image magnification, and the like using the correction amount stored at that time in the third tray memory 63. Then, based on the chart image data after the correction processing, the chart image is output on the first side of the long sheet. The image formation at this time is the same as the image formation when single-sided output is selected as described above.

[0058] When the cover sheet output button 2701d is pressed, the cover sheet used to read the chart image formed on the long sheet is output to a sheet of paper (here, the sheet of paper stored in the second tray 70B) of a size corresponding to the long sheet on which the chart image is output this time.

[0059] 3A and 3B are diagrams showing a long sheet of paper on which a chart image is formed, where Fig. 3A shows a first side of the long sheet of paper, and Fig. 3B shows a second side of the long sheet of paper.

[0060] In the image forming apparatus exemplified in this embodiment, double-sided output is not possible for the long sheet 400 due to the problem of the transport path for double-sided output, and only single-sided output is possible in which an image is formed only on the first side 401 as shown in FIG. 3. The second side 402 remains blank. The chart image memory 65 provided in the controller 6 shown in FIG. 1 stores chart image data corresponding to each size of sheet. Also, the third tray memory 63 corresponding to the third tray 70C in which the long sheet is accommodated stores a correction amount of the image to be formed on the first side 401 of the long sheet 400. Then, when forming a chart image on the long sheet 400, the chart image data for the long sheet out of the chart image data stored in the chart image memory 65 is read out and printed out by the image forming unit 100. The printed out chart is read out by the image reading unit 200, and the read chart image data is used to generate correction amounts for the image formation position, magnification, and the like stored in the third tray memory 63. The long sheet of paper 400 shown in FIG. 3 is a chart printed out by the image forming unit 100 in such a process.

[0061] The chart image output on the long sheet 400 is made up of detection images 601 and 602 and alignment images 603 and 604 .

[0062] The detection images 601, 602 are images for measuring distances d1, d2 between the ends of the long sheet 400 as shown in Fig. 3, and detecting information such as the image forming position. Image data obtained by reading the detection images 601, 602 is input to the read image memory 64 of the controller 6, and the controller 6 measures the distances d1, d2, etc. to detect information such as the image forming position. Then, based on this detected information, the correction amount stored in the third tray memory 63 is generated. These detection images 601, 602 correspond to an example of the first image according to the present invention.

[0063] Here, of the detection images 601, 602, one of the detection images 601 is formed at a position closer to the first end 400a of the long paper 400, and the other detection image 602 is formed at a position closer to the second end 400b of the long paper 400.

[0064] Moreover, the alignment images 603 and 604 are images for aligning the long sheet 400 when reading the detection images 601 and 602. Of these alignment images 603 and 604, the alignment image 603 formed closer to the first end 400a is for alignment when reading the detection image 601 formed closer to the first end 400a. Moreover, the alignment image 604 formed closer to the second end 400b is for alignment when reading the detection image 602 formed closer to the second end 400b.

[0065] FIG. 4 is a diagram showing a cover sheet. Here, FIG. 4(A) shows the first side of the cover sheet, and FIG. 4(B) shows the second side of the cover sheet. This cover sheet 500 is output by pressing the cover sheet output button 2701h after pressing the chart image output instruction button 2701a shown in FIG. 2 to output a chart image. The cover sheet 500 output by pressing the cover sheet output button 2701h is a cover sheet of a size suitable for reading the chart image output immediately before. That is, in the scene described here, the cover sheet 500 of a size used when reading the detection images 601, 602 constituting the chart image formed on the long sheet 400 shown in FIG. 4 is output. As described above, a large-sized sheet of paper stored in the second tray 70B is used as the cover sheet 500 when reading the detection images 601, 602 on the long sheet 400 shown in FIG. 4. This large-sized sheet of paper can be output on both sides. Here, a uniform black image is formed on the entire first side 501 of the large-sized sheet. This is to increase the density difference between the ground color of long sheet 400 and the background in the data read by image reading unit 200 in order to recognize the paper edge of long sheet 400, which is the chart. Also, an alignment image 503 is formed on second side 502. This alignment image 503 is formed at a position along a first edge 504 extending in the longitudinal direction of cover paper 500 and closer to the inside than a second edge 505 extending in the width direction. This alignment image 503 corresponds to an example of the second image referred to in the present invention.

[0066] The chart image is used to detect the current positional deviation of the image on the paper, and needs to be output each time it is detected. In contrast, the cover paper 500 can be output once and stored so that it can be used repeatedly. Therefore, the cover paper 500 may be output separately without providing the cover paper output button 2701h. Alternatively, it may be prepared separately from the image forming apparatus 10 (see FIG. 1).

[0067] FIG. 5 is a diagram showing how paper is aligned when a chart image is read.

[0068] FIG. 5 is a schematic diagram showing the image reading section 200 of the image forming apparatus 10 shown in FIG.

[0069] FIG. 5(A) shows a state in which the cover paper 500 is placed on the transparent glass 250 of the image reading unit 200. When placing the cover paper 500 on the transparent glass 250, the cover paper 500 is placed on the transparent glass 250 with its first surface 501 (see FIG. 4) facing the transparent glass 250, that is, with the first surface 501, which is entirely black, facing downward. When placing the cover paper 500 on the transparent glass 250, the top left corner is abutted against the frame of the transparent glass 250. This allows the position of the cover paper 500 relative to the transparent glass to be uniquely determined. When placing the cover paper 500 on the transparent glass 250, the cover paper 500 is placed in a position in which the first edge 504 on the side on which the alignment image 503 is formed is the front side (the lower side of the figure).

[0070] Next, as shown in FIG. 5B, the first end 400a side of the long sheet 400 is slipped under the cover sheet 500 with the first end 400a on which the chart image is formed facing downward (toward the transparent glass 250), so that the long sheet 400 protrudes from the first edge 504 of the cover sheet 500. Then, as shown in FIG. 5C, the portion of the long sheet 400 protruding from the first edge 504 of the cover sheet 500 is turned over, and the position of the long sheet 400 is adjusted while checking the alignment image 603. In this embodiment, the alignment image 603 is, for example, an image consisting of one black rectangle. Here, the alignment image 503 drawn on the cover sheet 400 and the alignment image 603 drawn on the long sheet 400 are arranged in the same position in the direction along the first edge 504 of the cover sheet 500. Furthermore, the alignment images 503, 603 sandwich the first edge 504 of the cover paper 500 and are approximately equal distances away from the first edge 504 as measured visually. When the long sheet 400 is placed in this position, the portion of the long sheet 400 covered by the cover paper 500, including the edges of the sheet, is within the reading area.

[0071] The long sheet 400 is then placed in this position, the upper cover 260 is closed, and an image of the portion of the long sheet 400 covered by the cover sheet 500 is read in the stationary reading mode described above. The image data obtained by this reading clearly shows the end of the portion of the long sheet 400 covered by the cover sheet 500 and the detection image 601 on the first end 400a side. The controller 6 shown in Fig. 1 obtains information necessary for detecting the position and magnification of the detection image 601 relative to the end of the long sheet 400, such as the distances d1 and d2 shown in Fig. 3, based on this image data.

[0072] Next, in the same manner as above, the second end 400b side of the long sheet 400 is inserted under the cover sheet 500, and the detection image 602 formed on the second end 400b side is read. The alignment marks at this time are the alignment image 503 on the cover sheet 500 and the alignment image 604 on the long sheet 400, which consists of two black rectangles. In this way, by making the alignment image 604 an image (here, an image of two black rectangles lined up in the longitudinal direction of the long sheet 400) different from the other alignment image 603 (here, an image consisting of one black rectangle), it is possible to easily recognize whether the image to be read this time is the first end 400a side or the second end 400b side. Note that the two alignment images 603, 604 only need to be images that can be distinguished from each other, and do not need to differ in number, and may be characters such as "1" and "2", patterns of different shapes, or images of different colors.

[0073] In addition, the detection images 601, 602 may also be made to have at least a portion different from each other, so that it is possible to distinguish between the detection image 601 on the first end 400a side and the detection image 602 on the second end 400b side from the image data obtained by reading.

[0074] In this way, the detection image 601 on the first end 400a side and the detection image 602 on the second end 400b side are read to detect the distance from the end of the long sheet 400, and the controller 6 calculates how much the position, magnification, etc. of the image formed on the long sheet 400 deviates from the predetermined position, magnification, etc. This "deviation" represents a "deviation" from the correction amount stored in the third tray memory 63 that could not be corrected by the correction amount stored in the third tray memory 63. Therefore, the controller 6 corrects the correction amount stored in the third tray memory 63 based on information representing this "deviation" so that the "deviation" is eliminated, and stores the corrected correction amount in the third tray memory 63 in place of the correction amount stored up until that point. The image newly formed on the long sheet after that adopts the new correction amount, and therefore becomes an image with the correct position and magnification that were previously determined.

[0075] 6 is a diagram showing a long sheet of paper on which a chart image of the second example is formed. Here, only the differences from the chart image shown in FIG.

[0076] The chart image shown in Fig. 6 includes two alignment images 605, 606 in addition to the two alignment images 603, 604. These two alignment images 605, 606 are images consisting of line segments extending in the width direction of the long sheet 400. These alignment images 605, 606 are alignment images that serve as a guide for the appropriate insertion amount when inserting the long sheet 400 under the cover sheet 500. In other words, when inserting the first end 400a of the long sheet 400 under the cover sheet 400, the alignment image 605 is inserted to a position where it overlaps with the first edge 504 (see Fig. 5) of the cover sheet 500. The presence of this alignment image 605 makes it even clearer how far the sheet should be inserted. Alignment in the width direction, i.e., along the first edge 504, is performed using the rectangular alignment image 503 on the cover paper 500 and the alignment image 603 on the long paper 400, as in the case of the chart image shown in FIG.

[0077] Similarly, when inserting the second end 400b of the long paper 400 under the cover paper 400, insert it to a position where the alignment image 606 overlaps with the first edge 504 of the cover paper 500. The presence of this alignment image 606 makes it clearer how far the paper should be inserted. Alignment in the width direction, i.e., along the first edge 504, is performed by the rectangular alignment image 503 on the cover paper 500 and the alignment image 604 on the long paper 400.

[0078] As shown in FIG. 6, instead of forming an alignment image for visually estimating either the position in the insertion direction or the position in the width direction, it is also possible to form both an alignment image for the insertion direction and an alignment image for the width direction.

[0079] Fig. 7 is a diagram showing a large-size sheet of paper on which a chart image is formed, Fig. 7(A) shows a first side of the large-size sheet of paper, and Fig. 7(B) shows a second side of the large-size sheet of paper.

[0080] The chart image formed on the first side 701 of the large size paper 700 shown in Fig. 7 includes a detection image 710 and alignment images 711, 712, 713, and 714. Similarly, a chart image including a detection image 720 and alignment images 721, 722, 723, and 724 is formed on the second side 702. The chart images on the first side and the second side are the same except that, in order to easily distinguish between the first side and the second side, the alignment images 711 and 712 on the first side 701 are black rectangular images, while the alignment images 721 and 722 on the second side 702 are black-bordered rectangular images.

[0081] As described above, large-sized paper is accommodated in the second tray 70B of the image forming apparatus 10 shown in FIG. 1. This large-sized paper can be double-sided output, that is, images can be formed on both sides of the large-sized paper. Therefore, a chart image is formed on both sides of the large-sized paper. To form a chart image on the large-sized paper, first, the correction amount calculation mode button 2702a is pressed a predetermined number of times to set a mode for calculating a correction amount for an image formation position on the large-sized paper accommodated in the second tray 70B. Then, the second tray designation push button 2701f shown in FIG. 2 is placed in a state in which it can be pressed. Then, the second tray designation push button 2701f is pressed. Then, the chart image data for the large-sized paper stored in the chart image memory 65 of the controller 6 (see FIG. 1) is read out, and the chart image data is corrected with the correction amount for the first side in the second tray memory 62, and a chart image based on the corrected chart image data is formed on the first side. Similarly, the chart image data for large size paper stored in the chart image memory 65 is corrected with the correction amount for the second side in the second tray memory 62, the alignment images 721, 722 are changed to rectangular images with black frames, and a chart image based on the corrected and changed chart image data is formed on the second side.

[0082] When reading the chart image formed on this large size paper 700, a part of the paper 700 is inserted under the cover paper in the same manner as when reading the chart image on the long paper 400. Here, the alignment images 711 and 721 on the first side 701 and the second side 702 correspond to the alignment image 603 shown in FIG. 6 on the long paper 400, and the alignment images 712 and 722 on the first side 701 and the second side 702 correspond to the alignment image 604 shown in FIG. 6 on the long paper 400. The alignment images 713 and 723 on the first side 701 and the second side 702 correspond to the alignment image 605 shown in FIG. 6 on the long paper 400, and the alignment images 714 and 724 on the first side 701 and the second side 702 correspond to the alignment image 606 shown in FIG. 6 on the long paper 400. Duplicate explanations will be omitted.

[0083] When aligning this large size paper 700, the paper 700 is not turned over, and alignment images 721-724 on the second side 702 are used for alignment when reading the first side 701, and alignment images 711-714 on the first side 701 are used for alignment when reading the second side 702. In the case of this large size paper 700, four readings are performed, including reading the first end 700a side of the first side 701, reading the second end 700b side of the first side 701, reading the first end 700a side of the second side 702, and reading the second end 700b side of the second side 702.

[0084] FIG. 8 shows a second example of the cover paper.

[0085] The cover sheet 500 shown in FIG. 4 is a sheet on which a uniform black image is formed over the entire surface of its first surface 501 and an alignment image 503 is formed on its second surface. In contrast, in the case of the cover sheet 800 of the second example shown in FIG. 8, only the alignment image 803 is formed on one surface (first surface) of a sheet of paper having a certain degree of density. The density of this cover sheet 800 is such that the edge of the sheet can be detected with sufficient accuracy when it is read as shown in FIG. 5. The alignment image 803 formed on the sheet 800 is an image of a density that can be clearly seen on the sheet. Note that the alignment image 803 is not limited to black, and may have a density that is sufficient to recognize the difference from the background color of the chart sheet. In the case of an image forming apparatus that can use special colors, the alignment image may be formed using a white special color on a black sheet of paper.

[0086] The cover paper 800 of this second example can also be used as a cover paper when reading a chart image formed on one side in an image forming apparatus capable of only single-sided output.

[0087] According to the above embodiment, even if a chart image is formed on only one side of a sheet of paper, The paper can be properly registered. [Explanation of symbols]

[0088] 10 Image forming device 10a Output tray 11K,11C,11M,11Y Image carrier 100 Image forming unit 200 Image reading unit 250 Clear Glass 260 Top cover 2701 Display screen 2702 Buttons 2702a Correction amount calculation mode button 4 Fixing device 5 Exposure section 400 Long Paper 400a First end 400b 2nd end 500,800 Cover paper 503,803 alignment images 504 First Edge 601,602 Detection images 603,604,605,606 Images for alignment

Claims

1. a placement table for placing an object whose image is to be read; an image forming unit that forms an image including a first image for measuring a relative position with respect to an end of the paper only on a first surface of the paper; an image reading unit that reads an image placed on the placement table; a position correction unit that corrects a relative position of an image formed on a sheet of paper based on a result of reading by the image reading unit, When the first side of the paper on which the first image is formed is placed on the placement table with the edge of the paper facing the placement table and the edge of the paper at a position away from the edge of the placement table, and the paper is further covered with a cover paper, and when the edge of the paper and the image formed on the first side of the paper are read by the image reading unit, the paper is placed in a state in which a part of the paper protrudes from the placement table and the first edge of the cover paper, the image forming unit forms a third image, which is to be aligned with a second image for alignment formed on the surface of the cover paper opposite to the surface where the cover paper and the paper contact, only on the first side of the paper, and the image forming unit forms a fourth image for alignment in a direction intersecting with the first edge, which is required to be overlapped with the first edge, in addition to the first image and the third image, only on the first side of the paper. Image forming device.

2. The image forming unit forms, as the third image, both on only the first surface of the paper, a first third image for alignment when the image formed in an area including a first end portion of the longitudinal direction of the paper is read by the image reading unit, and a second third image for alignment when the image formed in an area including a second end portion of the paper is read by the image reading unit. The image forming apparatus according to claim 1 .

3. The image forming unit forms the first third image and the second third image, which are visually different from each other, on the first surface of the paper. The image forming apparatus according to claim 2 .

4. the first third image is an image consisting of one shape arranged in a position facing the second image across the first edge, and the second third image is an image consisting of two of the shapes arranged in a direction intersecting the first edge and arranged in a position facing the second image across the first edge, The image forming apparatus according to claim 3 .

5. The image forming unit forms, as the fourth image, both on only the first surface of the paper, a first fourth image for alignment in a direction intersecting with the first edge when the image formed in the area including the first end of the paper is read by the image reading unit, and a second fourth image for alignment when the image formed in the area including the second end of the paper is read by the image reading unit. The image forming apparatus according to claim 1 .

6. The image forming unit forms an image on a second sheet of paper different from a first sheet of paper on which an image including the first image is formed, so that the second sheet of paper is used as the cover sheet. The image forming apparatus according to claim 1 .

7. the image forming unit forms an image in a color that is distinguished from the color of the first sheet on a portion of a first surface of the second sheet that overlaps with an end of the first sheet when the first sheet is covered, and forms the second image on a second surface of the second sheet. The image forming apparatus according to claim 6.

8. a placement table for placing an object whose image is to be read; an image forming unit that forms an image including a first image for measuring a relative position with respect to an end of the paper only on a first surface of the paper; an image reading unit that reads an image placed on the placement table; a position correction unit that corrects a relative position of an image formed on a sheet of paper based on a result of reading by the image reading unit, When the first side of the paper on which the first image is formed is placed on the placement table with an end of the paper facing the placement table and away from an end of the placement table, and the paper is further covered with a cover paper, and when the end of the paper and the image formed on the first side of the paper are read by the image reading unit, the paper is placed in a state where a part of the paper protrudes from the placement table and the first edge of the cover paper, the image forming unit forms a third image, which is to be aligned with a second image for alignment formed on a surface of the cover paper opposite to a surface where the cover paper and the paper contact, only on the first side of the paper, and the image forming unit forms the second image in a color differentiated from the color of the cover paper on the cover paper in a color differentiated from the color of the first paper on which an image including the first image is formed. Image forming device.

Images