JP2017167205A - Image processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discriminate the presence of peculiar winding of a recording medium and recognize the amount of peculiar winding.SOLUTION: A lattice-shaped discrimination area Ad is provided as a read unit of an image Dp of printed matter. The density of the image Dp of printed matter deriving by reading an image printed on paper P is determined in read units of the discrimination area Ad. There is a tendency that the density near the center of conveyance direction of the paper P is dark and the density of the tip and rear end portions in the conveyance direction is light, so the occurrence of convex curl on the paper P is predicted. The amount of curl is set on the basis a density difference-curl amount conversion table obtained experimentally or by calculation in advance. There is a tendency that the density near the center of conveyance direction of the paper P is light and the density of the tip and rear end portions in the conveyance direction is dark, so the occurrence of concave curl on the paper P is predicted. The amount of curl is set on the basis of a density difference-curl amount conversion table obtained experimentally or by calculation in advance.SELECTED DRAWING: Figure 7

Description

  The present invention relates to an image processing apparatus.

  In the image forming process, when heat and pressure are applied to the paper, curling (so-called curl) may occur on the paper.

  Patent Document 1 describes that the degree and direction of curling are determined and corrected by the pressing force of the sheet.

  In Patent Document 2, printing is performed during setup, the curl shape is measured by the curl shape assumption unit, the curl shape stored in the job, the image area ratio of the developed image, double-sided, single-sided, discharge method It describes that the curl correction is performed.

  Patent Document 3 describes that the amount of curl is estimated and corrected based on the image density of the developed image.

  For reference, the image forming apparatus may be provided with an image reading function for reading an image after image formation, and may be fed back to the color conversion process control during image formation.

JP 2000-229758 A JP 2002-348023 A JP 2013-033156 A

  An object of the present invention is to obtain an image processing apparatus capable of determining the presence or absence of curling of a recording medium and recognizing the amount of curling.

  The invention according to claim 1 is an image forming unit that forms an image on a recording medium, an image inspection unit that reads an image formed on the recording medium and inspects the image, and an image that is read by the image inspection unit. Analyzing and discriminating means for discriminating the flatness of the recording medium, and recovery means for recovering the flatness during conveyance when the recording medium deviates from the predetermined flatness based on the discrimination result of the discriminating means And an image processing apparatus.

  According to a second aspect of the present invention, in the first aspect of the present invention, the gap of the guide path of the image reading position of the image inspection unit can be changed in the thickness direction of the recording medium, and the image is inspected. The recording medium does not move in the thickness direction and is a gap that does not hinder movement along the guide path. When the discrimination means discriminates the flatness of the recording medium, the recording medium hinders movement in the thickness direction. Not enlarged in the gap.

  According to a third aspect of the invention, in the invention of the first or second aspect, the discrimination means divides the image into predetermined discrimination areas, monitors the density distribution of each area, and performs biasing. When there is a change in the density of the discriminating area, the presence / absence of deviation of the flatness of the recording medium and the degree of deviation are discriminated.

  According to a fourth aspect of the present invention, in the invention according to the third aspect, when there is an area where the density of the discrimination area is concentrated and changes with respect to the reference density, the deviation of the flatness of the recording medium is discriminated. In addition, the direction of deviation of the flatness of the recording medium and the degree of deviation of the flatness of the recording medium are obtained based on the position of the concentrated area on the recording medium and the density difference from the reference density.

  According to a fifth aspect of the invention, in the first or second aspect of the invention, the discriminating means displaces an image in a direction intersecting the conveyance direction according to the deviation direction of the flatness of the recording medium. Is used to determine whether or not there is a deviation in flatness of the recording medium and the degree of deviation based on the displacement direction and displacement amount of the reference line set in parallel with the conveyance direction on the recording medium.

  According to a sixth aspect of the invention, in the fifth aspect of the invention, when the reference line of the recording medium is displaced outward in the width direction of the recording medium, the entire recording medium is convex along the conveying direction. If the reference line of the recording medium is displaced inward in the width direction of the recording medium, the entire recording medium deviates from the flatness in the conveying direction. And the degree of deviation of the flatness of the recording medium is determined based on the amount of distortion.

  The invention according to claim 7 is the correction device according to any one of claims 1 to 6, wherein the recovery means intentionally curves and corrects the recording medium.

  According to the first aspect of the present invention, it is possible to determine the presence or absence of curling of the recording medium and to recognize the amount of curling.

  According to the second aspect of the present invention, the guide surface that interferes with the deformation direction of the recording medium can be retracted.

  According to the third aspect of the present invention, the flatness of the recording medium can be determined using the density distribution.

  According to the fourth aspect of the invention, by analyzing the density distribution, it is possible to determine the presence or absence of the flatness of the recording medium and the degree of the deviation.

  According to the fifth aspect of the present invention, it is possible to determine the flatness of the recording medium using the distortion of the image.

  According to the sixth aspect of the present invention, by analyzing the distortion of the image, it is possible to determine the presence or absence of the flatness of the recording medium and the degree of the deviation.

  The recording medium can be corrected by intentionally curving.

1 is a schematic configuration diagram illustrating an example of a configuration of an image forming apparatus according to a first embodiment. 1 is a schematic configuration diagram illustrating an example of a configuration of a built-in image sensor provided in an image forming apparatus according to a first embodiment. The correction apparatus which concerns on 1st Embodiment is an enlarged view. FIG. 4 is an enlarged view showing a movable structure of a paper guide portion of the built-in image sensor according to the first embodiment. It is a block diagram of a control system concerning a 1st embodiment. FIG. 2 is a schematic diagram showing functions of the image forming apparatus in FIG. 1 in a block form according to the first embodiment. FIG. 4 is a development view of a printed image Dp when an m × n grid-like discrimination region Ad for discriminating a density distribution in a two-dimensional (x, y) direction is provided, (A) is a normal image, (B) A convex curl image, (C) shows a concave curl image. 4 is a flowchart illustrating a main routine of image processing control executed by the control device according to the first embodiment. FIG. 9 is a flowchart showing a flow of curl determination control executed in step 354 of FIG. 8 according to the first embodiment. 3A and 3B are three side views (a front view, a plan view, and a right side view) of a sheet P according to the second embodiment. According to the second embodiment, (A) is a developed view of the print image Di, (B) is a developed view of the contour image Dr, and is a developed view showing setting of a reference line, (C) and (D ) Is a development view of the printed image Dp, and is a development view showing that the inclination angle is discriminated by the discrimination line. FIG. 9 is a flowchart showing a curl determination control flow executed in step 354 of FIG. 8 according to the second embodiment. FIG. 10 is a schematic diagram illustrating functions of an image forming apparatus in a block form according to a third embodiment. FIG. 10 is a schematic diagram illustrating functions of an image forming apparatus in a block form according to a fourth embodiment.

“First Embodiment”
(Overall configuration of image forming apparatus)
As shown in FIG. 1, the image forming apparatus 10 according to the first embodiment selectively forms a full-color image and a black-and-white image, and includes a first housing 10A serving as image forming means, A second housing 10B connected to the housing 10A. An image processing unit 13 that performs image processing on image data supplied from an external device such as a computer is provided on the upper portion of the second housing 10B.

  In this specification, “image formation” and “printing” are treated as synonymous. That is, for example, an apparatus for developing an electrostatic latent image using a charged toner is commonly referred to as an “image forming apparatus”, and forms of image formation on paper include “single-sided printing”, “double-sided printing”, “Printed matter” or the like is applied as a common name. The first embodiment is not limited to image formation using an electrostatic latent image, but also includes image formation (printing) using general ink. Therefore, “image formation” and “printing” are performed as necessary. "".

  In the upper part of the first housing 10A, yellow (Y), magenta (M), cyan (C), and black (K) as normal colors, and gold (G) and first as the first special colors are displayed. There are provided toner cartridges 14Y, 14M, 14C, 14K, 14G, and 14S for accommodating respective silver (S) toners as two special colors. In addition, although gold (G) and silver (S) were selected as special colors, colors other than YMCK colors, for example, special colors such as white (W), clear (CL), and custom red (CR) may be selected. .

  In the first embodiment, gold and silver are exemplified as the first special color and the second special color. However, the reflectance is higher than that of at least yellow, magenta, cyan, and black, and image inspection described later. Gold having a high reflectance that deviates from the dynamic range of the detection signal (density value) at the time of image reading by the built-in image sensor 200 as an example of the means can be selected, and is applied in the first embodiment. In addition to silver, white (W), clear (CL), and the like are applicable.

  Hereinafter, each color of YMCK is referred to as a normal color, the other colors are referred to as special colors, and a special color belonging to a high reflectance color among the special colors is referred to as a rate special color.

  In the following description, the first special color (G), the second special color (S), yellow (Y), magenta (M), cyan (C), and black (K) are distinguished for each component. Will be described by adding a letter of G, S, Y, M, C, or K after a number as a symbol. When the first special color (G), the second special color (S), yellow (Y), magenta (M), cyan (C), and black (K) are not distinguished, G, S, Y, M , C and K are omitted.

  Below the toner cartridge 14, there are six image forming units 16G, 16S, 16Y, 16M, 16C and 16K which are examples of image forming units corresponding to the toners of the respective colors (collectively referred to as “image forming unit 16”). Is provided to correspond to each toner cartridge 14.

  The exposure devices 40G, 40S, 40Y, 40M, 40C, and 40K (collectively referred to as “exposure device 40”) provided for each image forming unit 16 are prints that have been subjected to image processing by the image processing unit 13 described above. Image data is received from the image processing unit 13. Then, a light beam modulated in accordance with the image data is irradiated to image holders 18G, 18S, 18Y, 18M, 18C, and 18K (hereinafter collectively referred to as “image holder 18”). .

  In each image forming unit 16, an electrostatic latent image is formed on each image carrier 18 by irradiating each image carrier 18 with the light beam L from each exposure device 40.

  Around each image carrier 18, a corona discharge (non-contact charging) scorotron charger that charges the image carrier 18 and an electrostatic latent image formed on the image carrier 18 by the exposure device 40 are developed. A developing device that develops with toner, which is an example of an agent, a blade that removes the developer remaining on the image carrier 18 after transfer, and a static eliminator that performs static elimination by irradiating the image carrier 18 after transfer with light. Is provided. The scorotron charger, the developing device, the blade, and the static eliminator are arranged in this order from the upstream side to the downstream side in the rotation direction of the image carrier 18 so as to face the surface of the image carrier 18.

  A transfer unit 32 is provided below each image forming unit 16. The transfer unit 32 includes an annular intermediate transfer belt 34 that is in contact with each image carrier 18, and primary transfer rolls 36 </ b> G, 36 </ b> S, 36 </ b> Y that multiplex-transfer the toner image formed on each image carrier 18 onto the intermediate transfer belt 34. 36M, 36C, 36K (collectively referred to as “primary transfer roll 36”).

  The intermediate transfer belt 34 includes a drive roll 38 that is driven by a motor (not shown), a tension applying roll 41 that applies tension to the intermediate transfer belt 34, an opposing roll 42 that faces a secondary transfer roll 62 described below, It is wound around a plurality of winding rolls 44. And it is circularly moved in one direction (counterclockwise direction in FIG. 1) by the drive roll 38.

  Each primary transfer roll 36 is disposed opposite to the image carrier 18 of each image forming unit 16 with the intermediate transfer belt 34 interposed therebetween. The primary transfer roll 36 is applied with a transfer bias voltage having a polarity opposite to the toner polarity by a power supply unit (not shown). With this configuration, the toner image formed on the image carrier 18 is transferred to the intermediate transfer belt 34.

  On the opposite side of the drive roll 38 across the intermediate transfer belt 34, there is provided a removing device 46 that removes residual toner, paper dust and the like on the intermediate transfer belt 34 by bringing the blade into contact with the intermediate transfer belt 34. .

  Below the transfer unit 32, a plurality of paper storage units 48 that store recording media P as an example of a medium such as paper are provided. Each of the sheet storage portions 48 can be pulled out from the first housing 10A. A delivery roll 52 that feeds the paper P from each paper storage section 48 to the transport path 60 is provided above one end side of each paper storage section 48 (right side in front view in FIG. 1).

  In each paper storage portion 48, a bottom plate 50 on which the paper P is placed is provided. The bottom plate 50 is lowered by an instruction from a control means (not shown) when the paper storage portion 48 is pulled out from the first housing 10A. When the bottom plate 50 is lowered, a space for the user to replenish the paper P is formed in the paper storage portion 48.

  When the paper storage portion 48 pulled out from the first housing 10A is attached to the first housing 10A, the bottom plate 50 is raised by an instruction from the control means. By raising the bottom plate 50, the uppermost sheet P placed on the bottom plate 50 and the delivery roll 52 come into contact with each other.

  A separation roll 56 is provided on the downstream side in the paper conveyance direction of the delivery roll 52 (hereinafter sometimes simply referred to as “downstream side”), and separates the paper P that has been delivered from the paper storage portion 48 one by one. ing. A plurality of transport rolls 54 that transport the paper P downstream in the transport direction are provided on the downstream side of the separation roll 56.

  The conveyance path 60 provided between the paper storage unit 48 and the transfer unit 32 reverses the paper P sent out from the paper storage unit 48 to the left side when viewed from the front in FIG. Further, the second direction changing portion 60B extends to the transfer position T between the secondary transfer roll 62 and the opposing roll 42 so as to be reversed to the right in the front view in FIG.

  The secondary transfer roll 62 is applied with a transfer bias voltage having a polarity opposite to the toner polarity by a power feeding unit (not shown). With this configuration, each color toner image transferred onto the intermediate transfer belt 34 is secondarily transferred onto the paper P conveyed along the conveyance path 60 by the secondary transfer roll 62.

  A preliminary path 66 extending from the side surface of the first housing 10 </ b> A is provided so as to join the second direction changing portion 60 </ b> B of the transport path 60. The paper P sent out from another paper storage unit (not shown) arranged adjacent to the first housing 10 </ b> A can enter the transport path 60 through the spare path 66.

  On the downstream side of the transfer position T, a plurality of conveyance belts 70 that convey the paper P on which the toner image has been transferred toward the second casing 10B are provided in the first casing 10A, and are conveyed to the conveyance belt 70. A transport belt 80 that transports the paper P downstream is provided in the second housing 10B.

  Each of the plurality of conveyor belts 70 and the conveyor belt 80 is formed in an annular shape, and is wound around a pair of winding rolls 72. The pair of winding rolls 72 are respectively arranged on the upstream side and the downstream side in the transport direction of the paper P, and when one of them is rotationally driven, the transport belt 70 (transport belt 80) is moved in one direction (the timepiece in FIG. 1). Cycle in the direction of rotation).

  A fixing unit 82 for fixing the toner image transferred onto the surface of the paper P to the paper P with heat and pressure is provided on the downstream side of the conveyance belt 80.

  The fixing unit 82 includes a fixing belt 84 and a pressure roll 88 disposed so as to contact the fixing belt 84 from below. A fixing unit N is formed between the fixing belt 84 and the pressure roll 88 to fix the toner image by pressurizing and heating the paper P.

The fixing belt 84 is formed in an annular shape and is wound around the drive roll 89 and the driven roll 90. The drive roll 89 faces the pressure roll 88 from above,
The driven roll 90 is disposed above the drive roll 89.

  Each of the driving roll 89 and the driven roll 90 includes a heating unit such as a halogen heater. As a result, the fixing belt 84 is heated.

  As shown in FIG. 1, a conveyance belt 108 is provided on the downstream side of the fixing unit 82 to convey the paper P sent out from the fixing unit 82 to the downstream side.

  A cooling unit 110 that cools the paper P heated by the fixing unit 82 is provided on the downstream side of the conveyance belt 108.

  The cooling unit 110 includes an absorption device 112 that absorbs the heat of the paper P, and a pressing device 114 that presses the paper P against the absorption device 112. The absorption device 112 is disposed on one side (upper side in FIG. 1) with respect to the conveyance path 60, and the pressing device 114 is disposed on the other side (lower side in FIG. 1).

  The absorption device 112 includes an annular absorption belt 116 that contacts the paper P and absorbs the heat of the paper P. The absorption belt 116 is wound around a driving roll 120 that transmits a driving force to the absorption belt 116 and a plurality of winding rolls 118.

  A heat sink 122 made of, for example, an aluminum material is provided on the inner peripheral side of the absorption belt 116 to dissipate the heat absorbed by the absorption belt 116 in contact with the absorption belt 116 in a planar shape.

  Further, a fan 128 for removing heat from the heat sink 122 and discharging hot air to the outside is disposed on the back side of the second housing 10B (the back side of the paper surface shown in FIG. 1).

  The pressing device 114 that presses the paper P against the absorbing device 112 includes an annular pressing belt 130 that conveys the paper P while pressing the paper P against the absorbing belt 116. The pressing belt 130 is wound around a plurality of winding rolls 132.

  On the downstream side of the cooling unit 110, a correction device 140 is provided as an example of a recovery unit that conveys the paper P and corrects the curl of the paper P.

  On the downstream side of the correction device 140, an image reading device (built-in image sensor 200), which is an example of an image forming device that detects a toner density defect, an image defect, an image position defect, and the like of the toner image fixed on the paper P, is provided. It has been. Details of the correction device 140 and the built-in image sensor 200 will be described later.

  A post-processing device 199 attached to the side surface of the second housing 10B is disposed on the downstream side of the built-in image sensor 200, and the image-formed (printed) paper P is discharged by a discharge roll 198 to the post-processing device 199. To be sent to.

  The post-processing device 199 performs post-processing such as folding the paper P, punching holes, and binding (binding). The paper P that has been post-processed by the post-processing device 199 (including the paper P that does not undergo post-processing and passes through) is discharged to the discharge unit 196.

  On the other hand, when images are formed on both sides, the paper P sent from the built-in image sensor 200 is conveyed to a front / back reversing path 194 provided on the downstream side of the built-in image sensor 200.

  The front / back reversing path 194 includes a branch path 194A branched from the transport path 60, a paper transport path for transporting the paper P transported along the branch path 194A toward the first housing 10A, and a paper transport path 194B. A front / back reversing path 194 </ b> C is provided that reverses the paper P conveyed along the reverse direction and reverses the paper P so as to reverse the front and back.

  With this configuration, the paper P that has been switched back by the front / back reversing path 194C is transported toward the first housing 10A, and further enters the transport path 60 provided above the paper storage portion 48, so that the transfer position T Will be sent again.

(Forced device 140)
As shown in FIG. 3, the correction device 140 includes a convex curl correction unit 142 and a concave curl correction unit 144.

  The convex curl correction unit 142 is disposed on the upper side of the paper conveyance path and the surface thereof is covered with an elastic member 146A and has an elastic force. The pressure roller 148A is disposed on the lower side of the paper conveyance path and the pressure roller 148A. And a guide roller 150 </ b> A whose surface is made of metal and hard.

  On the other hand, the concave curl correction unit 144 is disposed below the paper transport path and has a pressure roller 148B having an elastic force with the surface covered with an elastic member 146B, and a pressure roller disposed above the paper transport path. 148B and a guide roller 150B whose surface is made of metal and hard.

  As shown in FIG. 3, the pressure rollers 148A and 148B of the convex curl correction unit 142 and the concave curl correction unit 144 are in contact with and separated from the guide rollers 150A and 150B (directions intersecting the paper conveyance direction), respectively. , And can be moved by the driving force of a driving source (not shown) (motor or solenoid).

  When the pressure rollers 148A and 148B are positioned at the dotted line positions in FIG. 3, it is the position farthest from the paper conveyance path, and no curl correction is performed at this position.

  Here, the pressure rollers 148A and 148B can move to the solid line position in FIG. 3, and in this case, a part in the thickness direction from the surface is located on the opposite side of the conveyance path.

  When the paper P is conveyed in this state, the convex curl correcting unit 142 deforms the sandwiched paper P into a concave shape, and thus corrects the convex curl according to the position of the pressure roller 150A.

  Further, in the concave curl correction unit 144, since the sandwiched paper P is deformed into a convex shape, the concave curl is corrected according to the position of the pressure roller 150B.

  Position control of the pressure rollers 148A and 148B of the convex curl correction unit 142 and the concave curl correction unit 144 is executed based on curl correction information managed by the control device 20 described later.

(Built-in image sensor 200)
The image forming apparatus 10 according to the first embodiment includes the built-in image sensor 200 on the downstream side of the correction device 140 as described above. The built-in image sensor 200 is used for detecting whether or not an image formed on the paper P by the image forming unit 16 is abnormal.

  The built-in image sensor 200 in this case has a function as a means for measuring gradation reproducibility and color reproducibility of the image forming unit 16. In addition, in order to maintain the function as the measurement unit normally, the built-in image sensor 200 may be calibrated regularly or irregularly.

  In the following description, the length direction of the image forming apparatus 10 (sub-scanning direction that is the conveyance direction of the paper P) is the X direction, the height direction of the apparatus is the Y direction, and the depth direction of the apparatus (main scanning direction) is the Z direction. (See FIGS. 1 and 2).

  As shown in FIG. 2, the built-in image sensor 200, which is an example of an image reading apparatus, includes an illumination unit 202 that emits light toward the paper P on which an image is recorded, and a paper P that is emitted from the illumination unit 202. An image forming unit 208 having an image forming optical system 206 that forms an image of the reflected light on the CCD sensor 204, and a setting unit 210 provided with various standards and the like when the built-in image sensor 200 is used or calibrated. I have.

  The CCD sensor 204 according to the first embodiment includes a plurality of light receiving elements (for example, photodiodes) arranged along a direction corresponding to the main scanning direction, A green image sensor and a blue image sensor are provided. Each color image sensor is provided with a filter that transmits light of each color component on the light receiving surface of the light receiving element.

Due to the structure of the CCD sensor 204, the built-in image sensor 200 may be referred to as an inline sensor (ILS) or the like. ).
Each color image sensor outputs, as a signal, the electric charge accumulated according to the amount of each color component of the light received by the light receiving element.

  The illumination unit 202 is disposed on the upper side of the conveyance path 60 of the paper P, and a pair of first lamp 212A and second lamp 212B (hereinafter collectively referred to as “long” in the Z direction (main scanning direction). It may be referred to as “lamp 212”).

  As the lamp 212, for example, a fluorescent lamp, a xenon lamp, or a plurality of white LEDs (not shown) arranged along the main scanning direction is used.

  The length of the irradiation range of the lamp 212 is set larger than the width of the maximum sheet P to be conveyed. The lamp 212 is arranged symmetrically with respect to the optical axis OA (designed optical axis) that is reflected by the paper P and travels toward the image forming unit 208.

  The light irradiated from the lamp 212 is configured to irradiate the irradiation position D of the transparent window glass 286 on the transport path 60 between the first lamp 212A and the second lamp 212B.

  The window crow 286 is held by the bracket 287, and the sheet P that normally conveys the conveyance path does not move in the thickness direction between the sheet P and the setting unit 210, and the movement along the conveyance path is not hindered. Arranged with a moderate gap. Note that “normal” refers to the time when the image of the paper P that has undergone image formation processing is read and inspected.

  In the window glass 286, the irradiation area irradiated with light from the lamp 212 is an area that overlaps the area through which the image forming area of the paper P passes on the setting unit 210, and is formed on the paper P on the transport path 60. An area where an image is read by the CCD sensor 204 is configured to include a predetermined area (image reading area).

  In addition, the imaging optical system 206 includes a first mirror 214 that reflects the light guided along the optical axis OA in the X direction (downstream in the transport direction of the paper P in the first embodiment), and a first mirror. The second mirror 216 that reflects the light reflected by 214 upward, the third mirror 218 that reflects the light reflected by the second mirror 216 upstream in the transport direction of the paper P, and the light reflected by the third mirror 218 A lens 220 that focuses (images) on the CCD sensor 204 and a light amount diaphragm unit 224 (224L, 224S, 224U)) are mainly configured.

  The length of the first mirror 214 in the Z direction is larger than the maximum width of the paper P. Then, the first mirror 214, the second mirror 216, and the third mirror 218 are respectively condensing (condensing) the reflected light of the paper P incident on the imaging optical system 206 in the Z direction (main scanning direction). It is designed to reflect. Thus, the reflected light from each part in the width direction of the paper P is made incident on the substantially cylindrical lens 220.

  The built-in image sensor 200 is configured such that the CCD sensor 204 outputs (feeds back) the imaged light, that is, a signal corresponding to the image density, to the control device 20 (see FIG. 1) of the image forming apparatus 10. .

  The control device 20 performs processing for correcting an image formed in the image forming unit 16 based on a signal input from the built-in image sensor 200. As an example of processing for correcting an image, correction of a tone adjustment LUT (lookup table) of the image forming apparatus 10 can be given.

  Other examples of correction include correction of the intensity of irradiation light by the exposure apparatus 40 based on a signal input from the built-in image sensor 200, the image formation position, and the like, and correction of the development potential and transfer current value.

  The setting unit 210 includes a reference roll 226 that is long in the Z direction. The reference roll 226 is formed in a polygonal cylindrical shape in which a predetermined number of surfaces are formed in the circumferential direction. In the reference roll 226 according to the first embodiment, a polygonal cylindrical shape having 10 surfaces is used. Has been.

  As shown in FIG. 2, the reference roll 226 detects the image of the paper P by the built-in image sensor 200 and the detection reference surface 228 (basic color is black) directed toward the conveyance path 60 when the image of the paper P is detected. And a retreating surface 230 directed toward the conveyance path when not performing, and each of the other surfaces functions as a reference surface (color reference surface) for each color used in color gamut correction processing or the like.

  The reference roll 226 is configured to switch the surface to be directed to the conveyance path 60 side by rotating around the rotation shaft 226A. The surface of the reference roll 226 is switched by the control circuit 100 provided on the circuit board 262.

  The retracting surface 230 has a circumferential width larger than that of other surfaces. The retreat surface 230 is a guide surface that guides the paper P when the built-in image sensor 200 does not detect the image of the paper P.

(Guide evacuation structure)
Here, in the built-in image sensor 200 according to the first embodiment, the bracket 287 that holds the window glass 286 described above can be moved so as to contact or separate from the setting unit 210 as shown in FIG. It has become.

  The bracket 287 is positioned at the dotted line in FIG. 4 when the image of the paper P is read after the image forming process by the driving force of a driving source (such as a motor or a solenoid) (not shown), and the paper P passing through the conveyance path is thick. It is arranged with an appropriate gap that does not move in the direction and does not hinder movement along the conveyance path.

  Here, at the time of execution of curl determination control, which is executed by the control unit 20 described later, the window glass 286 and the bracket 287 are in the solid line positions in FIG. 4, and the paper P is in the thickness direction between the setting unit 210 and the window P. It is arranged with a gap that can move freely.

  In the curl determination control, if there is a curl or curl in the paper P, the direction (convex curl or concave curl) and the amount of curl are analyzed and curl correction information is generated. (Details will be described later).

(Control system)
As shown in FIG. 5, the control device 20 that controls the image forming apparatus 10 according to the first embodiment is formed in the image forming unit 16 based on a signal from the built-in image sensor 200 as described above. It has a function to correct images. The control device 20 also has a function of controlling calibration of the built-in image sensor 200 (for example, calibration of the CCD sensor 204 described above).

  The control device 20 includes a CPU (Central Processing Unit) 20A, a ROM (Read Only Memory) 20B, a RAM (Random Access Memory) 20C, and an input / output port 20D. Each is connected to each other via a bus 20E such as an address bus, a data bus, and a control bus.

  Various programs are stored in the ROM 20B, and various controls are performed by the CPU 20A reading the programs from the ROM 20B, developing them in the RAM 20C, and executing them.

  Note that a non-volatile storage medium (NVM) that stores various types of information that must be retained even when the power switch of the apparatus is turned off may be provided.

  A user interface device (UI device) 30, an image formation control unit 102, a control circuit 100 of the built-in image sensor 200, and an image formation control unit 102 are connected to the input / output port 20D.

  An image forming unit 304, a fixing unit 82, and a correction device 140 are connected to the image forming control unit 102.

  The UI device 30 includes, for example, a touch panel display in which a transmissive touch panel is superimposed on a display. Various types of information are displayed on the display surface of the display, and information and instructions are received when the user touches the touch panel. In the first embodiment, an example in which the UI device 30 is applied has been described. However, the present invention is not limited to this, and an operation unit provided with a display unit such as a liquid crystal display and a numeric keypad or operation buttons. And may be provided separately.

  FIG. 6 is a schematic diagram showing the image forming apparatus 10 (see FIG. 1) having the above-described configuration in blocks. Some of the functions already described with reference to FIG. 1 show correspondences, and a description thereof is omitted here.

  An image generation unit 302 is connected to the control device 20. The image generation unit 302 is typically a PC (personal computer) connected via a communication line network (not shown), but may be a recording medium including SD and DVD.

  The image processing unit 300 receives the document image data Dg from the image forming unit 302 and converts it (mainly color conversion) into print image data Di. The print image data Di is sent to the printing unit 304.

  The printing unit 304 is an example of an image forming unit, and corresponds to the image forming unit 16 and the fixing unit 82 in FIG.

  The paper feed unit 306 corresponds to the paper storage unit 48, the delivery roll 52, and the separation roll 56 of FIG.

  The paper transport unit 308 corresponds to a roll and belt-type transport member along the transport path 60 in FIG.

  The paper discharge unit 310 corresponds to the discharge unit 196 in FIG.

  Further, the final printed matter Ps is the paper P on which all the processes are completed.

  The print image data Di generated by the image processing unit 300 is sent to the defect determination unit 312.

  On the other hand, the built-in image sensor 200 reads the printed image Dp read from the image printed on the paper P and sends it to the defect determination unit 312.

  The defect determination unit 312 collates the print image data Di and the printed image data Dp to determine whether there is an image defect, feeds back to the image processing unit 300, and corrects the color to be appropriate.

(Curl state judgment)
Here, the control device 20 according to the first embodiment functions as an example of a determination unit, and in addition to the normal image forming process control, the curl state of the paper P (whether or not the curl is generated, the curl direction, and the curl amount). Curl determination control is executed.

  The execution timing of the curl determination control is not particularly limited, but normal image forming process control such as before starting each job, daily power-on, regular maintenance, and execution instruction by the UI device 30 It is preferable to execute in a period different from the period.

  In the case of a process that does not require an image inspection by the built-in image sensor 200 during a normal image formation process control period, it is also possible to execute the curl determination control while executing the image formation process control.

  In the first embodiment, the density of the paper P passing through the built-in image sensor 200 is detected using the image reading function of the built-in image sensor 200, and the curl state is determined based on the density distribution state of the entire surface of the paper P. doing.

  Further, based on the curl state determination result, the correction device 140 executes the curl correction process from the sheet P on which an image is formed in the next image formation process.

  When the curled state is determined, as shown in FIG. 4, the bracket 287 of the built-in image sensor 200 is retracted from the conveyance path (solid line position in FIG. 4), and the paper is placed between the setting unit 210 and the paper. A gap is provided so that P can move freely in the thickness direction.

(Basic principle of curl judgment)
As shown in FIG. 7A, for example, as a reading unit of the printed product image Dp, an m × n grid-like discrimination region Ad (partial index) is provided in the two-dimensional (x, y) direction.

  FIGS. 7B and 7C are examples of a printed product image Dp obtained by reading an image printed on the paper P in the reading unit of the discrimination area Ad.

  FIG. 7B shows that the density in the vicinity of the central portion in the transport direction of the paper P tends to be high, and the density at the front and rear end portions in the transport direction tends to be low. Is done. The curl amount is set based on a density difference-curl amount conversion table obtained experimentally or in advance by calculation.

  FIG. 7C shows that the density in the vicinity of the central portion in the conveyance direction of the paper P tends to be low, and the density at the front and rear end portions in the conveyance direction tends to be high. Is done. The curl amount is set based on a density difference-curl amount conversion table obtained experimentally or in advance by calculation.

  In the control unit 20, the pressure roller 148A and the concave portion of the convex curl correction unit 142 of the correction device 140 are determined based on the determined curl correction information based on the density distribution of the printed image Dp with respect to the print image Di (for example, white paper) of the paper P. The position of the pressure roller 148B of the curl correction unit 142 is adjusted, and the curl correction process for the conveyed paper P is executed in the next image forming process.

  The operation of the first embodiment will be described below.

  FIG. 8 is a flowchart showing a main routine of image processing control executed by the control device 20.

  In step 350, it is determined whether or not an image formation instruction has been issued. If a negative determination is made, the process proceeds to step 352 to determine whether or not it is a curl determination time. If a negative determination is made in step 352, this routine ends.

  Further, when an affirmative determination is made at step 352, the routine proceeds to step 354, where curl determination control is executed. Details of the curl determination control will be described later according to the flowchart of FIG.

  On the other hand, if an affirmative determination is made in step 350 of FIG. 8, the process proceeds to step 356 to read the original image Dg, and then proceeds to step 358 to generate the print image Di. That is, color conversion processing is executed.

  In the next step 360, the curl correction information is read out, and the process proceeds to step 362 to adjust the correction device 140 based on the curl correction information.

  In the convex curl correction unit 142, the sandwiched paper P is deformed into a concave shape, so that the convex curl is corrected. Further, in the concave curl correcting unit 144, the sandwiched paper P is deformed into a convex shape, so that the concave curl is corrected. The correction amount can be adjusted depending on the movement positions of the pressure rolls 148A and 148B.

  In the next step 364, an image forming process is executed. The detailed procedure of the image forming process is shown below.

(Details of image forming process)
Image data that has been subjected to image processing by the image processing unit 13 is sent to each exposure device 40.
In each exposure device 40, each light beam L is emitted according to image data, and is exposed to each image carrier 18 charged by a scorotron charger, thereby forming an electrostatic latent image.

  The electrostatic latent image formed on the image carrier 18 is developed by the developing device, and the first special color (G), the second special color (S), yellow (Y), magenta (M), and cyan (C). A toner image of each color of black (K) is formed.

As shown in FIG. 1, each color toner image formed on the image carrier 18 of each of the image forming units 16G, 16S, 16Y, 16M, 16C, and 16K has six primary transfer rolls 36G,
Multiple transfer is sequentially performed on the intermediate transfer belt 34 by 36S, 36Y, 36M, 36C, and 36K.

  The color toner images transferred onto the intermediate transfer belt 34 are secondarily transferred onto the paper P conveyed from the paper storage unit 48 by the secondary transfer roll 62. The sheet P on which the toner image has been transferred is conveyed toward the fixing unit 82 provided inside the second housing 10B by the conveyance belt 70.

  Each color toner image on the paper P is fixed on the paper P by being heated and pressurized by the fixing unit 82. Further, the sheet P on which the toner image is fixed is cooled by passing through the cooling unit 110 and then sent to the correction device 140 to correct the curvature generated on the sheet P.

  The paper P whose curvature is corrected is discharged to the discharge unit 196 by the discharge roll 198 after an image defect or the like is detected by the built-in image sensor 200.

  On the other hand, when an image is formed on a non-image surface where no image is formed (in the case of duplex printing), after passing through the built-in image sensor 200, the paper P is reversed by the front / back reversing path 194. Then, the toner image is fed into a conveyance path 60 provided above the sheet storage portion 48, and a toner image is formed on the back surface in the above-described procedure.

  In the image forming apparatus 10 according to the first embodiment, components for forming images of the first special color and the second special color (image forming units 16G and 16S, exposure devices 40G and 40S, toner cartridge 14G). 14S and primary transfer rolls 36G and 36S) are configured to be attachable to the first housing 10A as additional components according to the user's selection. Accordingly, the image forming apparatus 10 has a configuration that does not include parts for forming images of the first special color and the second special color, and any one of the first special color and the second special color. It is good also as a structure which has only the components for forming the image of this.

  Next, the built-in image sensor 200 detects a toner density defect, an image defect, an image position defect, and the like of the toner image fixed on the paper P.

  The toner density defect is corrected by reading the toner image with the built-in image sensor 200 and feeding back to the image forming unit with respect to environmental changes and machine differences, part deterioration over time, and part machine differences (factor 1 to factor 3). To do.

  Further, the toner density defect is caused by, for example, converting the image data (RGB) received at the time of image formation into an L * a * b * color space or the like in response to the color conversion error (factor 4). The image is converted into cmyk, which is an image, and there may be a color if it is reproduced during the color conversion process. Therefore, the toner image is read by the built-in image sensor 200, fed back to the image forming unit, and corrected so as to achieve proper color conversion.

  Further, the image defect performs feedback correction for interpolating with surrounding image data, and the image position defect performs feedback correction for changing the image position.

(Curl judgment control)
FIG. 9 is a flowchart showing the flow of curl determination control according to the first embodiment, which is executed in step 354 of FIG.

  In step 400, the window glass 286 and the bracket 287 of the built-in image sensor 200 are retracted, and then the process proceeds to step 402 to divide the printed image Dp into the lattice-shaped determination area Ad, and the process proceeds to step 404.

  In step 404, density information d1 (x, y) of each discrimination area Ad is extracted. That is, since x is 1 to m and y is 1 to n, m × n density information d1 is extracted.

  In the next step 406, the density information d2 (x, y) of the print image Di corresponding to each extracted discrimination region Ad is read, and then in step 408, the difference Δd () between the density information d1 and the density information d2 x, y) is calculated, and the process proceeds to step 410. In step 410, the difference Δd (x, y) that is the calculation result is stored in association with the coordinates of each discrimination region Ad, and the process proceeds to step 412.

  In step 412, it is determined whether or not the calculation of the difference Δd between the coordinates (m, n) of the determination area Ad is completed.

  If a negative determination is made in step 412, the process returns to step 404 and the above process is repeated.

  If the determination in step 412 is affirmative, it is determined that the density extraction and difference calculation for all the determination areas Ad have been completed, and the process proceeds to step 414 to read the stored difference Δd (x, y).

  In the next step 416, a difference Δd (x, y) value greater than or equal to a certain value is extracted from the read difference Δd (x, y), and the process proceeds to step 418.

  In step 418, it is determined whether or not the extracted difference Δd (x, y) equal to or greater than a certain value is continuous.

  If an affirmative determination is made in step 418, the process proceeds to step 420, the curl direction and the curl amount are acquired with reference to the density distribution charts of FIGS. 7B and 7C, and the process proceeds to step 424.

  If a negative determination is made in step 418, the process proceeds to step 422, where it is determined that there is no curl (including indistinguishability), and the process proceeds to step 424.

  In step 424, the curl correction information (direction and correction amount) is notified to the correction device 140 (including “no correction”), and then the process proceeds to step 426 and the window glass 186 and the bracket 187 of the built-in image sensor 200 are restored to the original. Return to position and the routine ends.

  Based on the curl correction information, the correction device 140 controls the positions of the pressure rollers 148A and 148B of the convex curl correction unit 142 and the concave curl correction unit to prepare for the curl correction of the next sheet P.

“Second Embodiment”
The second embodiment will be described below. The second embodiment is characterized by curl determination means different from that of the first embodiment, and the apparatus configuration (FIGS. 1 to 6) described in the first embodiment is applied and is the same. Description of the configuration is omitted by using the reference numerals.

  10A and 10B are three views (a front view, a plan view, and a right side view) of the paper P. FIG.

  FIG. 10A shows a state of the paper P in which the leading end in the transport direction is curled upward. That is, the entire paper P is a concave curled paper P.

  In such a tip upward curl (concave curl), as can be seen from the right side view of FIG. 10A, the curvature at both ends in the width direction is larger than the curvature at the center in the width direction.

  That is, with the tip upward curl (concave curl), the image tends to approach the center in the width direction in a plan view, and this tendency is remarkable at both ends in the width direction.

  FIG. 10B shows a state of the paper P in which the leading end in the transport direction is curled downward. In other words, the paper P as a whole is a convex curled paper P.

  In such a tip downward curl (convex curl), as can be seen from the right side view of FIG. 10A, the curvature at both ends in the width direction is larger than the curvature at the center in the width direction.

  That is, in the downward curl at the front end (convex curl), the image tends to approach both ends in the width direction in a plan view, and this tendency becomes remarkable at both ends in the width direction.

  Therefore, in the second embodiment, the contour of the print image Di shown in FIG. 11A is extracted to generate the contour image Dr (see FIG. 11B), and the contour of the contour image Dr is A reference line Lk is set by determining a plurality of reference points 1 parallel to the transport direction and connecting them with straight lines. In FIG. 11B, two reference lines Lk are set in the vicinity of both ends of the paper P in the width direction.

  Here, when the image forming process is completed and the image is read by the built-in image sensor 200, the reference point 2 corresponding to the reference point 1 is searched from the outline of the read printed image Dp, and is linearly arranged in the order of the paper conveyance direction. By connecting, the discrimination line Lh is set.

  Since the determination line Lh corresponds to the reference line Lk, two determination lines Lh are set in the vicinity of both ends in the width direction of the paper P as shown in FIG. 11C or 11D. Become.

  Here, according to the tendency shown in FIG. 10, when the discrimination line Lh and the reference line Lk are compared, if a curl is generated, an angle difference is generated.

  As shown in FIG. 11C, when the discrimination line Lh is inclined to the outside of the paper P, the image is on the outside, and therefore downward curl (convex curl for the entire paper P) is generated. It can be determined. Note that the inclination angle correlates with the curl amount.

  Further, as shown in FIG. 11D, when the discrimination line Lh is inclined inward of the paper P, the image is inward so that upward curling (concave curl in the whole paper P) occurs. It can be determined that it is present. Note that the inclination angle correlates with the curl amount.

  FIG. 12 is a flowchart showing a flow of curl determination control according to the second embodiment.

  In step 450, the window glass 286 and the bracket 287 of the built-in image sensor 200 are retracted, and then the process proceeds to step 452, where the contour is extracted from the print image Di, and the process proceeds to step 454.

  In step 454, a plurality of reference points 1 to be changed in the transport direction are determined from the extracted contours, and then the process proceeds to step 456 to connect the reference points 1 with straight lines in the order of the transport direction. In the second embodiment, as shown in FIG. 11B, a total of four reference lines Lk are set, two in the sheet width direction.

  In the next step 458, the contour is extracted from the printed product image Dp obtained by reading the image on the paper P formed on the basis of the print image Di by the built-in image sensor 200, and the process proceeds to step 460.

  In step 460, a plurality of reference points 2 at positions corresponding to the reference point 1 are determined from the extracted contours, and then the process proceeds to step 462, where the reference points 2 are connected in a straight line in the order of conveyance. In the second embodiment, as shown in FIG. 11B, a total of four discrimination lines Lh are set, two in the paper width direction.

  In the next step 464, the reference line Lk and the discrimination line Lh are compared. As a result of the comparison, it is determined in the next step 466 whether or not there is an angle difference.

  If an affirmative determination is made in step 466, it is determined that the determination line Lh is displaced with respect to the reference line Lk due to the occurrence of curling in the paper P, and the process proceeds to step 468 to be displaced. The curl state (convex curl or concave curl) is determined from the angle direction.

  That is, as shown in FIG. 11C, when the determination line Lh is inclined to the outside of the paper P, the image is on the outside, and thus downward curling (convex curling of the entire paper P) occurs. It is determined that

  Further, as shown in FIG. 11D, when the discrimination line Lh is inclined inward of the paper P, the image is inward so that upward curling (concave curl in the whole paper P) occurs. It is determined that

  In the next step 470, the curl correction amount is calculated from the angle (inclination amount), and the process proceeds to step 472. If the result in Step 466 is negative, the process proceeds to Step 472.

  That is, since the tilt angle correlates with the curl amount, for example, a pre-stored arithmetic expression is read to calculate the curl amount. A tilt angle-curl amount correlation table may be stored in advance, and the curl amount may be read from the table.

  In step 472, the curl correction information (that is, the curl direction and the curl amount) is notified to the correction device 140 (including no correction), and then the process proceeds to step 474 where the window glass 186 and the bracket 187 of the built-in image sensor 200 are displayed. Returning to the original position, this routine ends.

  Based on the curl correction information, the correction device 140 controls the positions of the pressure rollers 148A and 148B of the convex curl correction unit 142 and the concave curl correction unit to prepare for the curl correction of the next sheet P.

“Third Embodiment”
In the first embodiment and the second embodiment, the correction device 140 on the upstream side of the built-in image sensor 200 is disposed and the curl correction is performed from the next sheet P. However, as shown in FIG. As described above, the correction device 140 may be arranged adjacent to the downstream side of the built-in image sensor 200.

  For example, when an image forming process that does not require an image inspection is executed, an image can be formed while the window glass 186 and the bracket 187 of the built-in image sensor 200 are positioned at the retracted position. In other words, since the curl state can be determined after the image forming process, it is possible to establish a process of image forming process → curl state determination → curl correction.

“Fourth Embodiment”
In the first embodiment and the second embodiment, the correction device 140 on the upstream side of the built-in image sensor 200 is arranged to correct the curl from the next sheet P, and the third embodiment. The correction device 140 is arranged adjacent to the downstream side of the built-in image sensor 200, but may be provided in the post-processing device 199 as shown in FIG.

  In the existing image forming apparatus 10, when it is difficult to secure a space for arranging the correction device 140, the post-processing apparatus 199 itself is a post-installation apparatus, so that the image forming apparatus 10 has It is possible to easily incorporate the correction device 140 rather than incorporating it.

  In the first to fourth embodiments, the correction device 140 is applied to restore the flatness of the paper P, and the paper P is intentionally bent in a direction opposite to the curl direction. However, the flatness may be restored without applying a load to the paper P by heating or humidifying one side or spraying a special liquid agent.

L Light beam P Paper OA Optical axis 10 Image forming apparatus 10A First housing 10B Second housing 13 Image signal processing unit 14 (14G, 14S, 14Y, 14M, 14C, 14K) Toner cartridge 16 (16G, 16S, 16Y , 16M, 16C, 16K) Image forming unit 18 (18G, 18S, 18Y, 18M, 18C, 18K) Image carrier 20 Controller 20A CPU
20B ROM
20C RAM
20D I / O port 20E Bus 30 User interface (UI) panel 32 Transfer section 34 Intermediate transfer belt 36 (36G, 36S, 36Y, 36M, 36C, 36K) Primary transfer roll 38 Drive roll 40 (40G, 40S, 40Y, 40M) , 40C, 40K) Exposure device 41 Tension applying roll 42 Opposing roll 44 Winding roll 46 Removal device 48 Paper storage section 52 Delivery roll 50 Bottom plate 54 Transport roll 56 Separation roll 60 Transport path 60A First direction change section 60B Second direction change Unit 62 Secondary transfer roll 66 Preliminary path 70 Conveying belt 72 Rolling roll 80 Conveying belt 82 Fixing unit 84 Fixing belt 88 Pressing roll 89 Driving roll 90 Drive roll 100 Control circuit 108 Conveying belt 110 Cooling unit 112 Absorber DESCRIPTION OF SYMBOLS 14 Pressing device 116 Absorption belt 118 Winding roll 120 Drive roll 122 Heat sink 128 Fan 130 Pressing belt 140 Correction device 142 Convex curl correction unit 144 Concave curl correction unit 146A, 146B Elastic member 148A, 148B Pressure roller 150A, 150B Guide roller 194 Front / back reverse path 194A Branch path 194B Paper transport path 194C Front / back reverse path 196 Discharge unit 198 Discharge roll 200 Built-in image sensor 202 Illumination unit 204 CCD sensor 206 Imaging optical system 208 Imaging unit 212 Lamp 212A First lamp 212B Second lamp 214 First mirror 216 Second mirror 218 Third mirror 220 Lens 224 (224L, 224S, 224U) Light amount diaphragm unit 226 Reference roll 210 Installation 226 Reference roll 228 Detection reference surface 230 Retraction surface 286 Window glass 287 Bracket 300 Image processing unit 302 Image forming unit 304 Printing unit 306 Paper feeding unit 308 Paper transport unit 310 Paper discharge unit 312 Defective judgment unit Dg Original image data Di Print image Data Ps Final printed matter Ad Discrimination area Dr Contour image Lk Reference line Lh Discrimination line

Claims (7)

Image forming means for forming an image on a recording medium;
Image inspection means for inspecting an image by reading an image formed on the recording medium;
Analyzing the image read by the image inspection means, and determining means for determining the flatness of the recording medium;
Based on the determination result of the determination means, when the recording medium deviates from the predetermined flatness, recovery means for recovering the flatness during conveyance;
An image processing apparatus. The gap of the guide path of the image reading position of the image inspection means can be changed in the thickness direction of the recording medium,
When inspecting an image, the recording medium does not move in the thickness direction, and the gap does not hinder movement along the guide path.
The image processing apparatus according to claim 1, wherein when the determination unit determines the flatness of the recording medium, the recording medium is enlarged to a gap that does not hinder movement in the thickness direction.   The discrimination means divides the image into predetermined discrimination areas, monitors the density distribution of each area, and if there is a change in the density of the biased discrimination area, the presence or absence of deviation in flatness of the recording medium, The image processing apparatus according to claim 1, wherein the degree of deviation is determined.   When there is an area where the density of the determination area changes with concentration relative to the reference density, the deviation of the flatness of the recording medium is determined, and the position of the concentrated area on the recording medium and the reference density The image processing apparatus according to claim 3, wherein the direction of deviation of the flatness of the recording medium and the degree of deviation of the flatness of the recording medium are acquired based on the density difference.   Using the fact that the discriminating means displaces the image in the direction intersecting the transport direction according to the deviation direction of the flatness of the recording medium, the displacement direction and displacement of the reference line set parallel to the transport direction on the recording medium The image processing apparatus according to claim 1, wherein the presence or absence of a deviation in flatness of the recording medium and the degree of deviation are determined based on the amount. When the reference line of the recording medium is displaced outward in the width direction of the recording medium, it is determined that the entire recording medium deviates from planarity in a convex shape along the transport direction,
When the reference line of the recording medium is displaced inward in the width direction of the recording medium, it is determined that the entire recording medium deviates from planarity in a concave shape along the transport direction;
The image processing apparatus according to claim 5, wherein the degree of deviation of flatness of the recording medium is determined based on a distortion amount.   The image processing apparatus according to claim 1, wherein the recovery unit is a correction device that intentionally curves and corrects the recording medium.