Image forming device, image forming method, and program

Abstract

To provide an image forming device, an image forming method, and a program capable of performing more accurate pattern measurement even on a recording medium having irregular patterns.SOLUTION: An image forming device 1 comprises: an image forming unit 40 that forms an image on a sheet S having irregular patterns on the surface; a main scanner 55 functioning as a reading unit that reads a pattern image formed on the sheet S by the image forming unit 40; an acquisition unit that acquires irregular pattern information containing the amount and the position of an irregular pattern on the image forming surface of the sheet S before formation of the pattern image on the sheet S; and an adjustment unit that sets a pattern image forming place satisfying a predetermined condition on the basis of the irregular pattern information and adjusts a pattern image forming operation.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to an image forming apparatus, an image forming method, and a program.

Background Art

[0002] Conventionally, an image forming apparatus using an electrophotographic process technology is known. In the image forming apparatus, an electrostatic latent image is formed by irradiating a charged photoreceptor with laser light based on image data. Then, toner is supplied from a developing device to the photoreceptor drum on which the electrostatic latent image is formed, so that the electrostatic latent image is visualized to form a toner image. Then, after transferring the formed toner image onto a sheet of paper, the toner image is heated and pressed to be fixed on a recording medium to form an image.

[0003] In such an image forming apparatus, a pattern image for image quality stabilization is formed on a recording medium, and the state of the apparatus is acquired by reading the pattern image with a sensor, and the image forming conditions are adjusted. However, for example, when the recording medium is embossed paper, if the recording medium has unevenness and its height is non-uniform, due to the influence of the unevenness, the state of the apparatus may not be accurately acquired.

[0004] Specific examples are shown in FIGS. 9A and 9C. FIG. 9A is a graph showing the reading result by a sensor when a pattern image is formed on smooth paper. FIG. 9C is a graph showing the reading result by a sensor when a pattern image similar to that in FIG. 9A is formed at the position of the embossed paper shown in FIG. 9B. In FIGS. 9A and 9C, the horizontal axis represents the conveyance time, and the vertical axis represents the output value of the sensor that reads the pattern image (i.e., the image density). In FIG. 9B, the horizontal axis represents the length in the conveyance direction of the recording medium, and the vertical axis represents the height of the recording medium (i.e., the embossing amount). From the comparison between FIG. 9A and FIG. 9C, it can be seen that when a pattern image is formed over portions with different heights such as embosses, variations occur in the reading results of the sensor.

[0005] Therefore, for example, Patent Document 1 describes an image forming apparatus that specifies a region where image distortion occurs and its occurrence level based on the thickness of a recording medium having embosses and the depth of the embosses, and corrects the distortion.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, the invention of Patent Document 1 is an invention that calculates an estimated value by simply multiplying the measurement result by the value of a prescribed correction table, and does not guarantee highly accurate measurement results.

[0008] The present invention has been made in view of such circumstances. Its object is to provide an image forming apparatus, an image forming method, and a program that enable more accurate pattern measurement even for a recording medium having irregularities.

Means for Solving the Problems

[0009] To solve the above problems, the invention according to claim 1 is an image forming apparatus, comprising: an image forming unit that forms an image on a recording medium having irregularities on its surface; a reading unit that reads a pattern image formed on the recording medium by the image forming unit; an acquisition unit that acquires irregularity information regarding the amount of irregularities on the image forming surface of the recording medium before forming a pattern image on the recording medium; an adjustment unit that sets a pattern image formation location that meets predetermined conditions based on the irregularity information, and adjusts the pattern image formation operation by the image forming unit.

[0010] The invention according to claim 2 is the image forming apparatus according to claim 1, comprising a control unit that controls image forming conditions according to a reading result of the pattern image by the reading unit.

[0011] The invention according to claim 3 is the image forming apparatus according to claim 1, comprising a measurement unit that measures the unevenness, wherein the acquisition unit acquires the unevenness information from the measurement unit.

[0012] The invention according to claim 4 is the image forming apparatus according to claim 1, comprising a communication unit capable of communicating with another device and / or a storage unit in which the unevenness information is stored, wherein the acquisition unit acquires the unevenness information from the communication unit or the storage unit.

[0013] The invention according to claim 5 is the image forming apparatus according to any one of claims 1 to 4, wherein the adjustment unit determines whether a predetermined portion of the recording medium meets the predetermined conditions.

[0014] The invention according to claim 6 is the image forming apparatus according to claim 1, wherein the adjustment unit adjusts the forming operation of the pattern image by the image forming unit according to the size of the pattern image.

[0015] The invention according to claim 7 is the image forming apparatus according to claim 1, wherein the adjustment unit adjusts to change the size of the pattern image formed by the image forming unit according to the unevenness information.

[0016] The invention according to claim 8 is the image forming apparatus according to claim 3, wherein the measurement unit is provided at a position where the adjustment unit can reflect the unevenness information in an operation of the image forming unit to form the pattern image.

[0017] The invention according to claim 9 is an image forming apparatus according to claim 1, wherein the recording medium is continuous paper having an embossed surface, the unevenness information includes an embossing period in the conveyance direction of the recording medium.

[0018] The invention according to claim 10 is an image forming apparatus according to claim 9, wherein when the acquisition unit has acquired the embossing period, the acquisition of the unevenness information is terminated.

[0019] The invention according to claim 11 is an image forming method by an image forming apparatus including an image forming unit that forms an image on a recording medium having unevenness on its surface, and a reading unit that reads a pattern image formed on the recording medium by the image forming unit, the method comprising: an acquisition step of acquiring unevenness information including the amount and position of unevenness on the image forming surface of the recording medium before forming the pattern image on the recording medium; and an adjustment step of setting a pattern image formation location that meets predetermined conditions based on the unevenness information and adjusting the pattern image formation operation by the image forming unit.

[0020] The invention according to claim 12 is a program for causing a computer of an image forming apparatus including an image forming unit that forms an image on a recording medium having unevenness on its surface, and a reading unit that reads a pattern image formed on the recording medium by the image forming unit, to function as an acquisition unit that acquires unevenness information including the amount and position of unevenness on the image forming surface of the recording medium before forming the pattern image on the recording medium, and an adjustment unit that sets a pattern image formation location that meets predetermined conditions based on the unevenness information and adjusts the pattern image formation operation by the image forming unit.

Advantages of the Invention

[0021] According to the present invention, even for a recording medium having unevenness, more accurate pattern measurement becomes possible.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 4

Figure 5A

Figure 5B

Figure 6

Figure 7

Figure 8

Figure 9A

Figure 9B

Figure 9C

Embodiments for Carrying Out the Invention

[0023] Hereinafter, the image forming apparatus according to the embodiment of the present invention will be described in detail with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples. In the following description, components having the same function and configuration are denoted by the same reference numerals, and the description thereof will be omitted.

[0024] [Overall Configuration of Image Forming Apparatus] FIG. 1 is a schematic diagram showing the overall configuration of the image forming apparatus 1. FIG. 2 is a block diagram showing the main functional configuration of the image forming apparatus 1. The image forming apparatus 1 includes an image reading unit 10, an operation display unit 20, an image processing unit 30, an image forming unit 40, a paper conveyance unit 50, a fixing unit 60, a storage unit 70, a communication unit 80, and a control unit 100.

[0025] In the following, the X direction, Y direction, and Z direction refer to the directions shown in FIG. 1. Also, in the following, the X direction, Y direction, and Z direction will be described as the width direction, conveyance direction, and height direction, respectively.

[0026] The image forming apparatus 1 is a color image forming apparatus that uses electrophotographic process technology. That is, the image forming apparatus 1 primarily transfers the Y (yellow), M (magenta), C (cyan), and K (black) toner images formed on the photosensitive drum 413 to the intermediate transfer belt 421. Then, the image forming apparatus 1 forms an image by superposing the four-color toner images on the intermediate transfer belt 421 and then secondarily transferring them to the paper S.

[0027] Also, the tandem method is adopted in the image forming apparatus 1. Specifically, in the image forming apparatus 1, the photosensitive drums 413 corresponding to the four colors of YMCK are arranged in series in the running direction of the intermediate transfer belt 421. Then, the image forming apparatus 1 sequentially transfers the respective color toner images to the intermediate transfer belt 421.

[0028] (Control Unit) The control unit 100 includes a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, etc. The CPU 101 reads out a program according to the processing content from the ROM 102 and expands it in the RAM 103. Then, the CPU 101 centrally controls the operations of each part of the image forming apparatus 1 in cooperation with the expanded program.

[0029] (Image reading unit) The image reading unit 10 is configured to include an automatic document feeder 11, a document image scanning device 12, etc.

[0030] {Automatic document feeder} The automatic document feeder 11 is called an ADF (Auto Document Feeder). The automatic document feeder 11 conveys the document D placed on the document tray by a conveyance mechanism and sends it out to the document image scanning device 12. The automatic document feeder 11 can continuously read the images on both sides of a large number of documents D placed on the document tray all at once.

[0031] {Document image scanning device} The document image scanning device 12 is, for example, a scanner. The document image scanning device 12 optically scans the document conveyed onto the contact glass from the automatic document feeder 11 or the document placed on the contact glass. Then, the document image scanning device 12 forms an image of the reflected light from the document on the light receiving surface of a CCD (Charge Coupled Device) sensor 12a and reads the document image. The image reading unit 10 generates input image data based on the reading result by the document image scanning device 12. Predetermined image processing is performed on this input image data in the image processing unit 30.

[0032] (Operation display unit) The operation display unit 20 is composed of, for example, a liquid crystal display (LCD) with a touch panel. The operation display unit 20 functions as a display unit 21 and an operation unit 22.

[0033] {Display unit} The display unit 21 displays various operation screens, image status displays, or operation statuses of each function, etc., according to the display control signal input from the control unit 100.

[0034] {Operation unit} The operation unit 22 is provided with various operation keys such as numeric keys and start keys. The operation unit 22 receives various input operations by the user and outputs an operation signal to the control unit 100.

[0035] (Image processing unit) The image processing unit 30 includes a circuit or the like that performs digital image processing on the input image data according to initial settings or user settings. For example, the image processing unit 30 performs gradation correction based on gradation correction data (gradation correction table) under the control of the control unit 100. In addition, the image processing unit 30 performs various correction processes such as color correction and shading correction, and compression processing on the image data. The image data subjected to these processes is input to the image forming unit 40.

[0036] (Image forming unit) The image forming unit 40 includes image forming units 41Y, 41M, 41C, 41K and an intermediate transfer unit 42, etc.

[0037] {Image forming unit} The image forming units 41Y, 41M, 41C, 41K form images with respective colored toners of Y component, M component, C component, and K component based on the input image data. The image forming units 41Y, 41M, 41C, 41K have the same configuration. Therefore, for the sake of convenience of illustration and description, common components are denoted by the same reference numerals, and when distinguishing each of them, Y, M, C, or K is added to the reference numeral. In FIG. 1, only the components of the image forming unit 41Y for the Y component are denoted by reference numerals, and the components of the other image forming units 41M, 41C, 41K are omitted.

[0038] The image forming unit 41 includes an exposure device 411, a developing device 412, a photosensitive drum 413, a charging device 414, a drum cleaning device 415, and the like. Each device constituting the image forming unit 41 has the width direction as the axial direction.

[0039] 〔Exposure Device〕 The exposure device 411 is composed of, for example, a semiconductor laser. The exposure device 411 forms a latent image by scanning and exposing the charged photosensitive drum 413.

[0040] 〔Developing Device〕 The developing device 412 is a developing device using the two-component development method. The developing device 412 visualizes the electrostatic latent image by attaching toner of each color component to the surface of the photosensitive drum 413 to form a toner image. The developing roller 412A of the developing device 412 carries the developer while rotating and supplies the toner contained in the developer to the photosensitive drum 413, thereby forming a toner image on the surface of the photosensitive drum 413.

[0041] 〔Photosensitive Drum〕 The photosensitive drum 413 is, for example, a conductive cylindrical body (aluminum base tube) made of aluminum with a drum diameter of 80 mm. The photosensitive drum 413 is a negatively charged type organic photoreceptor (OPC: Organic Photo-conductor). The photosensitive drum 413 has an undercoat layer (UCL: Under Coat Layer), a charge generation layer (CGL: Charge Generation Layer), and a charge transport layer (CTL: Charge Transport Layer) sequentially laminated on the peripheral surface of the cylindrical body.

[0042] The control unit 100 rotates the photosensitive drum 413 at a constant peripheral speed by controlling the drive current supplied to a drive motor (not shown) that rotates the photosensitive drum 413.

[0043] 〔Charging Device〕 The charging device 414 uniformly charges the surface of the photosensitive drum 413 having photoconductivity to a negative polarity.

[0044] 〔Drum cleaning device〕 The drum cleaning device 415 has a drum cleaning blade, a lubricant application brush 415A, etc. The drum cleaning device 415 removes the transferred residual toner remaining on the surface of the photoreceptor drum 413 after primary transfer. The drum cleaning blade is in sliding contact with the surface of the photoreceptor drum 413. The lubricant application brush 415A applies a lubricant to the photoreceptor drum 413 for the purpose of enhancing the releasability between the photoreceptor drum 413 and the toner and suppressing the wear of the photoreceptor film thickness.

[0045] (Intermediate transfer unit) The intermediate transfer unit 42 includes an intermediate transfer belt 421, a primary transfer roller 422, a plurality of support rollers 423, a secondary transfer roller 424, a belt cleaning device 426, etc.

[0046] 〔Intermediate transfer belt〕 The intermediate transfer belt 421 is formed of an endless belt and is looped around a plurality of support rollers 423. At least one of the plurality of support rollers 423 is a driving roller, and the others are driven rollers. In particular, it is preferable that the roller 423A disposed on the downstream side in the belt running direction from the primary transfer roller 422 for the K component is a driving roller. This makes it easier to keep the running speed of the belt constant in the primary transfer section. When the driving roller 423A rotates, the intermediate transfer belt 421 runs at a constant speed in the direction of arrow A.

[0047] 〔Primary transfer roller〕 The primary transfer roller 422 is disposed on the inner peripheral surface side of the intermediate transfer belt 421 facing the photoreceptor drum 413 for each color component. By pressing the primary transfer roller 422 against the photoreceptor drum 413 with the intermediate transfer belt 421 interposed therebetween, a primary transfer nip for transferring the toner image from the photoreceptor drum 413 to the intermediate transfer belt 421 is formed.

[0048] 〔Secondary transfer roller〕 The secondary transfer roller 424 is disposed on the outer peripheral surface side of the intermediate transfer belt 421 so as to face the backup roller 423B disposed on the downstream side in the belt running direction of the driving roller 423A. With the secondary transfer roller 424 being pressed against the backup roller 423B with the intermediate transfer belt 421 interposed therebetween, a secondary transfer nip for transferring the toner image from the intermediate transfer belt 421 to the sheet S is formed.

[0049] When the intermediate transfer belt 421 passes through the primary transfer nip, the toner image on the photosensitive drum 413 is sequentially superimposed and primarily transferred onto the intermediate transfer belt 421. Specifically, a primary transfer bias is applied to the primary transfer roller 422 to impart a charge of the opposite polarity to the toner to the back surface side of the intermediate transfer belt 421. By this operation, the toner image is electrostatically transferred onto the intermediate transfer belt 421.

[0050] Thereafter, when the sheet S passes through the secondary transfer nip, the toner image on the intermediate transfer belt 421 is secondarily transferred onto the sheet S. Specifically, a secondary transfer bias is applied to the secondary transfer roller 424 to impart a charge of the opposite polarity to the toner to the back surface side of the sheet S, whereby the toner image is electrostatically transferred onto the sheet S. The sheet S onto which the toner image has been transferred is conveyed toward the fixing unit 60.

[0051] 〔Belt cleaning device〕 The belt cleaning device 426 has a belt cleaning blade or the like that slidably contacts the surface of the intermediate transfer belt 421, and removes the residual transfer toner remaining on the surface of the intermediate transfer belt 421 after secondary transfer. Note that instead of the secondary transfer roller 424, a so-called belt type secondary transfer unit in which a secondary transfer belt is looped around a plurality of support rollers including the secondary transfer roller may be employed.

[0052] (Sheet conveying unit) The paper conveyance unit 50 includes a paper feeding unit 51, a paper discharging unit 52, a conveyance path unit 53, a profile sensor 54, etc. The three paper feeding tray units 51a to 51c that make up the paper feeding unit 51 accommodate sheets of paper S (standard paper, special paper, etc.) identified based on basis weight, size, etc. in each preset type. The conveyance path unit 53 has a plurality of conveyance roller pairs such as a resist roller pair 53a.

[0053] The sheets of paper S accommodated in the paper feeding tray units 51a to 51c are sent out one by one from the top and conveyed to the image forming unit 40 by the conveyance path unit 53. At this time, the inclination of the fed sheet of paper S is corrected and the conveyance timing is adjusted by the resist roller unit provided with the resist roller pair 53a. Then, in the image forming unit 40, the toner image on the intermediate transfer belt 421 is collectively secondarily transferred onto one side of the sheet of paper S, and a fixing process is performed in the fixing unit 60. The sheet of paper S on which the image has been formed is discharged outside the machine by the paper discharging unit 52 equipped with a paper discharging roller 52a.

[0054] Note that the sheet of paper S used in this exemplary embodiment is a single-sheet paper having unevenness on its surface and uneven height depending on the position. Specifically, the sheet of paper S is, for example, embossed paper.

[0055] {Profile Sensor} The profile sensor 54 functions as a measuring unit that measures the unevenness on the surface of the sheet of paper S conveyed on the conveyance path unit 53.

[0056] A schematic diagram of the profile sensor 54 is shown in FIG. 3A. For the profile sensor 54, for example, an optical sensor is used. The profile sensor 54 irradiates the light La emitted from the light emitting unit 541 onto the sheet of paper S being conveyed, and divides the reflected light Lb from the sheet of paper S into P waves and S waves by polarizing plates 544 and 545. Then, the profile sensor 54 receives each light with a light receiving unit 542 for P waves and a light receiving unit 543 for S waves, and outputs a signal corresponding to the amount of received light.

[0057] For example, when the sheet S is smooth paper with a smooth surface and a small amount of unevenness, the specular reflection component increases and the diffuse reflection component decreases. Therefore, in the smooth portion of the sheet S, the generation of P-waves increases and the generation of S-waves decreases. On the other hand, as shown in FIG. 3B, when the sheet S is embossed paper or the like and has unevenness on the surface, the specular reflection component decreases and the diffuse reflection component increases. Therefore, in the portion of the sheet S having unevenness, the generation of P-waves decreases and the generation of S-waves increases.

[0058] Therefore, in advance, the storage unit 70 stores the association between the ratio of the received light amounts of the P-wave and the S-wave and the amount of unevenness of the sheet S based on experiments or the like. Then, the control unit 100 can acquire unevenness information including the amount and position of unevenness on the image forming surface of the sheet S based on the ratio of the received light amounts of the P-wave and the S-wave received from the profile sensor 54 and the above association. In this way, the control unit 100 functions as an acquisition unit that acquires unevenness information.

[0059] Also, the profile sensor 54 is provided upstream of the backup roller 423B and the secondary transfer roller 424 in the sheet conveyance unit 50.

[0060] More specifically, as shown in FIG. 1, the length from the irradiation position on the sheet S by the profile sensor 54 to the secondary transfer nip of the image forming unit 40 is defined as L1. Also, the length from the exposure portion of the photosensitive drum 413 by the exposure device 411 to the secondary transfer nip of the image forming unit 40 is defined as L2. At this time, the profile sensor 54 is provided at a position where at least L1 > L2. By providing the profile sensor 54 at this position, in the image defect detection process described later, the measurement result of the profile sensor 54 can be reflected in the setting of the formation position of the pattern image by the image forming unit 40.

[0061] {Image Scanner} Also, an image scanner 55 is provided downstream of the fixing unit 60 in the paper conveyance unit 50. The image scanner 55 is configured by, for example, a color scanner or the like and is configured to read an image during the conveyance of the paper S. Then, the image scanner 55 outputs the read image data (read image) obtained by reading the image to the control unit 100.

[0062] In particular, in the image defect detection process described later, the image scanner 55 functions as a reading unit that reads the pattern image formed on the paper S. The image scanner 55 transmits the read image obtained by reading the pattern image to the control unit 100. Then, the control unit 100 calculates the read gradation value (output value) from the read image. And the control unit 100 detects the presence or absence of color shift or the like by comparing the calculated read gradation value with the gradation value stored in the storage unit 70 in advance.

[0063] (Fixing unit) The fixing unit 60 heats and presses the paper S on which the toner image has been secondarily transferred and conveyed with a fixing nip. The fixing unit 60 fixes the toner image on the paper S by this process.

[0064] (Storage unit) The storage unit 70 is configured by, for example, a non-volatile semiconductor memory such as a so-called flash memory or a hard disk drive. Various data including various setting information related to the image forming apparatus 1 are stored in the storage unit 70.

[0065] For example, pattern image information is stored in the storage unit 70. The pattern image information is information for forming a pattern image used for specifying the cause of an image defect in the image defect detection process described later. The pattern image information includes the elapsed time from the start of forming the pattern image on the photosensitive drum 413. Further, the pattern image information includes information indicating the correspondence relationship between the position in the width direction of the photosensitive drum 413 where a pattern (the image portion where the toner of the pattern image is placed) is formed at a predetermined elapsed time and the image density of the formed pattern.

[0066] (Communication Unit) The communication unit 80 is composed of a communication control card such as a LAN (Local Area Network) card. The communication unit 80 performs transmission and reception of various data with an external device such as a personal computer connected to a communication network such as a LAN or a WAN (Wide Area Network).

[0067] [Image Defect Detection Process] The control unit 100 of the image forming apparatus 1 executes an image defect detection process at a predetermined timing such as the timing when a predetermined number of images are formed by a job.

[0068] As shown in FIG. 1, the exposure device 411, the developing device 412, and the charging device 414 are arranged around the photosensitive drum 413 in parallel with the photosensitive drum 413. And as described above, the charging device 414, the exposure device 411, and the developing device 412 perform charging, exposure, and development on the photosensitive drum 413 respectively. Therefore, when there is an abnormality in the exposure device 411, the developing device 412, and the charging device 414, image defects such as streaks mainly extending in the conveyance direction of the photosensitive drum 413, so-called vertical streaks, appear in the portion corresponding to the abnormal portion of the toner image formed on the photosensitive drum 413. Note that the abnormality is, for example, dirt on the exposure device 411 or the charging device 414, clogging of the developing device 412, uneven application of lubricant on the photosensitive drum 413, etc. The image defect detection process is a process for detecting such image defects as vertical streaks.

[0069] FIG. 4 is a flowchart showing the flow of the image defect detection process. The image defect detection process is executed by the cooperation of the control unit 100 and a program stored in the storage unit 70.

[0070] First, the control unit 100 acquires unevenness information of the paper S (step S101). As described above, the control unit 100 acquires the unevenness information of the paper S from the measurement result of the paper S by the profile sensor 54 which is a measurement unit.

[0071] The control unit 100 determines whether there is unevenness on the sheet S with an unevenness amount equal to or greater than a predetermined value that affects the reading of the image scanner 55 from the unevenness information of the sheet S (step S102). The predetermined value is, for example, 0.03 mm.

[0072] If there is no unevenness on the sheet S with an unevenness amount equal to or greater than the predetermined value (step S102; No), the control unit 100 forms a pattern image at an arbitrary position on the sheet S (step S103).

[0073] On the other hand, if there is unevenness on the sheet S with an unevenness amount equal to or greater than the predetermined value (step S102; Yes), the control unit 100 sets a formation position of a pattern image that does not affect the reading of the image scanner 55 (step S104).

[0074] FIG. 5A shows an example of a graph related to the unevenness information of the sheet S. In FIG. 5A, the horizontal axis represents the conveyance time of the sheet S, and the vertical axis represents the unevenness amount of the sheet S. Here, assume that the maximum value of the unevenness amount on the sheet S is about 0.1 mm. At this time, as shown in FIG. 5B, the control unit 100 divides the output value of the profile sensor 54 into four in the height direction. Then, the height of each divided region becomes 0.025 mm, and if a pattern image can be formed within each divided region, it will be within the allowable range of reading by the image scanner 55.

[0075] In FIG. 5B, the range of each line type provided so as to sandwich the double-headed arrow indicates the region where a pattern image can be formed in one divided region in each divided region. In FIG. 5B, since the sum is the longest in the region of the two-dot chain line, the control unit 100 sets to form a pattern image at a predetermined position in the region of the two-dot chain line.

[0076] The control unit 100 adjusts the pattern image forming operation of the image forming unit 40 to form a pattern image at the location set in step S104 on the sheet S, thereby forming the pattern image (step S105). In this way, the control unit 100 functions as an adjustment unit that sets a pattern image forming location that meets predetermined conditions based on the unevenness information and adjusts the pattern image forming operation by the image forming unit 40.

[0077] After the pattern image is formed in step S103 or step S105, the image scanner 55 reads the pattern image and transmits the read image to the control unit 100. Then, the control unit 100 determines the presence or absence of image quality disturbance from the output value obtained from the read image and detects the presence or absence of image defects (step S106).

[0078] FIG. 6 shows an example of a graph related to the output value of the image scanner 55 obtained when step S102;Yes. In FIG. 6, the horizontal axis represents the conveyance time, and the vertical axis represents the output value. As can be seen from the comparison between FIG. 6 and FIGS. 9A and 9C, according to this configuration, even if there are unevennesses on the surface of the sheet S that affect the reading by the image scanner 55, high-precision output values substantially the same as those in the case of plain paper can be obtained.

[0079] When an image defect is detected in the image defect detection process, the control unit 100 corrects the image defect, for example, by correcting the read image data based on the image defect. In this way, the control unit 100 controls the image forming conditions of the image forming unit 40 to eliminate the image defect.

[0080] [Effects of the Embodiment] As described above, the image forming apparatus 1 according to the present embodiment includes an image forming unit 40 that forms an image on a sheet S having irregularities on its surface. Further, the image forming apparatus 1 includes an image scanner 55 that functions as a reading unit for reading a pattern image formed on the sheet S. Further, the control unit 100 of the image forming apparatus 1 functions as an acquisition unit that acquires unevenness information regarding the amount of unevenness of the sheet S before forming the pattern image on the sheet S. Further, the control unit 100 of the image forming apparatus 1 functions as an adjustment unit that sets a pattern image formation location that meets a predetermined condition based on the unevenness information and adjusts the formation operation of the pattern image. According to this configuration, even if the sheet S has irregularities, the pattern image can be formed at a location where the reading result by the reading unit is less likely to vary, so that more accurate pattern measurement becomes possible.

[0081] Further, in a conventional image forming apparatus, due to problems such as fixing caused by embossing, the pattern image may be distorted, which may also cause variations in the reading result by the reading unit. However, according to the image forming apparatus 1 according to the present embodiment, the pattern image can be formed at a location where the height deviation due to embossing is small. Therefore, problems in pattern measurement associated with distortion of the pattern image can also be suppressed.

[0082] [Other configurations] Although the above has been specifically described based on the embodiments according to the present invention, the present invention is not limited to the above-described embodiments. Of course, various modifications including the scope of the invention described in the claims and its equivalent scope are possible.

[0083] For example, in the above, the case of forming a pattern image for detecting image defects was exemplified, but it is not limited to this. During the execution of the image forming process, the state of the image forming unit 40 changes sequentially. Examples of the changing state of the image forming unit 40 include the environment such as temperature and humidity, the charge amount of the developer in the developing device 412, the sensitivity of the photosensitive drum 413, and the like. Then, the density characteristics change according to such changes in the state of the image forming unit 40. Therefore, the control unit 100 performs control to feedback to the density adjustment of the formed image at a predetermined frequency by forming and measuring a pattern image for density measurement on the sheet S. The present invention is applicable also in the case of forming a pattern image in such density measurement.

[0084] Also, in the above, when there is no unevenness with an unevenness amount equal to or greater than a predetermined value on the sheet S, it was assumed that a pattern image is formed at an arbitrary position on the sheet S, but it is not limited to this. That is, based on the measurement result of the profile sensor 54, a pattern image may be formed in a region with less unevenness amount.

[0085] Also, in the above, a configuration in which the output value of the profile sensor 54 is divided into four was exemplified, but it is not limited to this. For example, when the maximum value of the unevenness amount on the sheet S is 0.15 mm, by dividing the output value of the profile sensor 54 into five, the height of each divided region becomes equal to or less than a predetermined value (0.03 mm). In this way, the number of divisions of the output value of the profile sensor 54 may be appropriately set according to the unevenness amount of the sheet S, the allowable range of reading by the image scanner 55, and the like. Note that when the number of divisions is increased, the height of each divided region becomes smaller accordingly, so that the reading result of the image scanner 55 becomes more stable. On the other hand, when the number of divisions is increased, the length of each divided region in the conveyance direction becomes relatively narrower, so that the area where a pattern image can be formed decreases.

[0086] In the above description, the case where the sheet S is a single-sheet paper is exemplified, but it is not limited to this. The sheet S may be a long sheet or a roll paper. In this case, the sheet S is stored, for example, in a paper feeding device connected to the image forming apparatus 1. Then, the sheet S held by the paper feeding device is supplied from the paper feeding device to the image forming apparatus 1 through a predetermined paper feeding port and sent out to the conveyance path portion 53.

[0087] Fig. 7 shows an example of a graph related to the output value of the profile sensor 54 in the roll-shaped sheet S. In Fig. 7, the horizontal axis represents the conveyance time, and the vertical axis represents the amount of unevenness. As shown by the dotted line portion in Fig. 7, in the roll-shaped sheet S, embosses of a predetermined pattern are periodically provided. Therefore, when the sheet S is in a roll shape, if the periodicity can be confirmed, the control unit 100 may obtain the output value by the profile sensor 54 at any position. Accordingly, when the sheet S is in a roll shape, the profile sensor 54 may be provided at a position where L1 < L2, and with such a configuration, the width length in the conveyance direction of the image forming apparatus 1 can be reduced. Further, when the sheet S is in a roll shape, the control unit 100 may reduce the control load by ending the measurement by the profile sensor 54 when the periodicity of the emboss is confirmed.

[0088] Also, when the sheet S is in a roll shape, even if patterns are formed at the same timing of a plurality of cycles, stable reading results can be obtained. However, actually, due to manufacturing errors or the like, there may be variations in the amount of unevenness, shape, etc. even between corresponding embosses. Therefore, also in such a sheet S, it is preferable to form a pattern at a position where the reading of the image scanner 55 is stable, as described above.

[0089] In addition, in FIG. 5B, the case where a pattern image can be formed in one divided area was exemplified. However, as shown in FIG. 8, there may be a case where a pattern image cannot be formed in one divided area. In such a case, the gradation of the pattern image may be reduced, for example, from 64 gradations to 32 gradations, and the width length may be narrowed so that a pattern image can be formed in one divided area. As shown in FIG. 8, it is difficult to form a high-quality image itself on the paper S with a large number of irregularities, and it is not necessary to form a high-gradation pattern image.

[0090] In addition, in the above, the configuration using the profile sensor 54 as the measurement unit was exemplified, but the present invention is not limited to this. The measurement unit may be any configuration that can measure the irregularities on the surface of the paper S, and is not limited to the profile sensor 54, and other transmissive optical sensors or the like can also be used.

[0091] In addition, in the above, the configuration in which the control unit 100 acquires the unevenness information by measuring the unevenness of the paper S with the profile sensor 54 provided in the image forming apparatus 1 was exemplified, but the present invention is not limited to this. For example, the paper S may be conveyed by a device separate from the image forming apparatus 1, and the unevenness of the paper S may be measured by a measurement unit provided in the device. In this case, the control unit 100 acquires the unevenness information by inputting the unevenness information from the separate device via the communication unit 80.

[0092] In addition, the acquired unevenness information of the roll-shaped paper S may be stored in the storage unit 70. When the paper S having the same unevenness is used again, etc., the unevenness information may be selected by operating the operation display unit 20, and the control unit 100 may acquire it.

[0093] In addition, although examples of using a hard disk, a semiconductor non-volatile memory, etc. as the computer-readable medium of the program according to the present invention were disclosed, the present invention is not limited to this. As other computer-readable media, portable recording media such as CD-ROM can be applied. In addition, a carrier wave is also applied as a medium for providing the data of the program according to the present invention via a communication line.

Explanation of Symbols

[0094] 1 Image forming apparatus 40 Image forming unit 54 Profile sensor (measurement unit) 55 Image scanner (reading unit) 100 Control unit (acquisition unit, adjustment unit) S Paper (recording medium)

Claims

1. An image forming unit that forms an image on a recording medium having unevenness on its surface; A reading unit that reads a pattern image formed on the recording medium by the image forming unit; An acquisition unit that acquires unevenness information regarding the amount of unevenness on the image forming surface of the recording medium before forming a pattern image on the recording medium; An image forming apparatus comprising: an adjustment unit that sets a pattern image forming location that meets predetermined conditions based on the unevenness information and adjusts the pattern image forming operation by the image forming unit.

2. The image forming apparatus according to claim 1, further comprising a control unit that controls image forming conditions according to a reading result of the pattern image by the reading unit.

3. Comprising a measurement unit that measures the unevenness, The image forming apparatus according to claim 1, wherein the acquisition unit acquires the unevenness information from the measurement unit.

4. Comprising a communication unit capable of communicating with another device and / or a storage unit in which the unevenness information is stored, The image forming apparatus according to claim 1, wherein the acquisition unit acquires the unevenness information from the communication unit or the storage unit.

5. The image forming apparatus according to any one of claims 1 to 4, wherein the adjustment unit determines whether a predetermined location on the recording medium meets the predetermined conditions.

6. The image forming apparatus according to claim 1, wherein the adjustment unit adjusts the pattern image forming operation by the image forming unit according to the size of the pattern image.

7. The image forming apparatus according to claim 1, wherein the adjustment unit adjusts so as to change the size of the pattern image formed by the image forming unit according to the unevenness information.

8. The image forming apparatus according to claim 3, wherein the measurement unit is provided at a position where the adjustment unit can reflect the unevenness information in an operation of the image forming unit for forming the pattern image.

9. The recording medium is continuous paper having an embossing process on its surface, The image forming apparatus according to claim 1, wherein the unevenness information includes an embossing cycle in the conveyance direction of the recording medium.

10. The image forming apparatus according to claim 9, wherein the acquisition unit ends the acquisition of the unevenness information when the embossing cycle is acquired.

11. An image forming unit that forms an image on a recording medium having unevenness on its surface; An image forming method by an image forming apparatus comprising: a reading unit that reads a pattern image formed on the recording medium by the image forming unit, Before forming a pattern image on the recording medium, an acquisition step of acquiring unevenness information including the amount and position of unevenness on the image formation surface of the recording medium; An adjustment step of setting a pattern image formation location that meets predetermined conditions based on the unevenness information and adjusting the pattern image formation operation by the image forming unit, the image forming method comprising the adjustment step.

12. An image forming unit that forms an image on a recording medium having unevenness on its surface; A computer of an image forming apparatus including a reading unit that reads a pattern image formed on the recording medium by the image forming unit, An acquisition unit that acquires unevenness information including the amount and position of unevenness on the image formation surface of the recording medium before forming a pattern image on the recording medium; A program that functions as an adjustment unit that sets a pattern image formation location that meets predetermined conditions based on the unevenness information and adjusts the pattern image formation operation by the image forming unit.

Images