JP2016025446A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to adjust a position at which an image forming part forms an image on a sheet on the basis of an image of a document fed by feeding means and read, even when an edge of the document is not detected.SOLUTION: An image forming apparatus of the present invention includes an image forming part, a sheet conveying part that feeds a document formed by the image forming part, a first image sensor that reads an image of a test chart fed by the sheet conveying part, and an edge chipping determination part that detects an edge of the test chart included in the image read by the first image sensor. The edge chipping determination part switches a correction amount calculation expression to correct a position at which the image forming part forms an image on a sheet depending on the presence or absence of an edge of the test chart detected by the first image sensor.SELECTED DRAWING: Figure 11

Description

  The present invention relates to an image forming apparatus.

  The image forming apparatus disclosed in Patent Document 1 can read the entire original regardless of the original width, and can obtain an output result similar to the central reference output even in the image forming apparatus having the specification of the end face reference output. Therefore, a document width detection unit that detects a document width, a scanner unit that sets a reading width in the main scanning direction around the center reference position, and reads image data while conveying the document in the sub-scanning direction, and a reading unit A plotter unit that forms an image based on the edge of the recording sheet based on the image data, an operation display unit for input and display, and reading with the maximum width reading that can be read from the operation display unit When an instruction is input, the document width detected by the document width detection unit is ignored, and reading is performed with the maximum readable width.

JP 2007-194938 A

When an image of an original is read while the original is being fed by the feeding unit, for example, when the paper size of the original is large, the end of the original may not fit within the read image.
An object of the present invention is to form an image on a sheet on the basis of an image of an original, even if the edge of the original is not detected in the original image sent and read by the feeding means. Position adjustment can be executed.

According to a first aspect of the present invention, there is provided an image forming unit, a feeding unit that feeds a document formed by the image forming unit, a reading unit that reads an image of the fed document, and the reading unit that reads the image. A calculation unit that calculates an adjustment amount of a position where the image forming unit forms an image on a sheet according to presence / absence of an end of the original detected by the detection unit and a detection unit that detects an end of the document included in the image An image forming apparatus comprising: a switching unit that switches formulas.
The invention according to claim 2 is characterized in that the switching unit switches the calculation formula depending on which end portion of the document is detected by the detection unit or which end portion of the document is not detected. The image forming apparatus according to claim 1.
According to a third aspect of the present invention, there is provided another switching for switching a position calculation formula for calculating a position of the specific image formed on the original in the original in accordance with the presence or absence of the edge portion of the original detected by the detecting means. The image forming apparatus according to claim 1, further comprising a unit.
According to a fourth aspect of the present invention, when the end portion of the document serving as a reference for measuring the position of the specific image formed on the document is not detected by the detection means, the document facing the end serving as the reference 4. The image forming apparatus according to claim 1, further comprising a measuring unit that measures a position of the specific image with reference to an end of the image forming apparatus. 5.
According to a fifth aspect of the present invention, when the reading unit reads a position adjustment document which is the document for adjusting the position where the image forming unit forms the image on the sheet, 5. The reading range for reading a predetermined document is shifted by a predetermined distance in one direction, and the end of the position adjusting document is included in the shifted reading range. The image forming apparatus according to claim 1.
The invention according to claim 6 is characterized in that the reading means shifts the reading range in a direction opposite to the one direction when the reading range cannot be shifted in the one direction by the predetermined distance. The image forming apparatus according to claim 5.
The invention according to claim 7 is capable of being read by the image forming unit, a feeding unit that feeds a document formed by the image forming unit, a reading unit that reads the document fed by the feeding unit, and the reading unit. A detecting means for detecting a specific image formed at a predetermined position in the original having the maximum width in an image obtained by reading the original having a maximum width by the reading means; and the specific image detected by the detecting means An image forming apparatus comprising: an adjusting unit that adjusts a position at which the image forming unit forms an image on a sheet based on the position of the maximum width document.

According to the first, second, and seventh aspects of the present invention, an image is formed on the basis of the original image even when the edge of the original is not detected in the original image that is sent and read by the feeding means. It is possible to adjust the position at which the image forming unit forms an image on a sheet.
According to the third aspect of the present invention, the position of the image can be calculated even when the edge of the document cannot be detected.
According to the fourth aspect of the present invention, the position of the specific image can be measured even when the end portion of the document serving as a reference for measuring the position of the specific image cannot be detected.
According to the invention described in claim 5, the position adjustment document is compared with a case where the reading range is shifted by a predetermined distance in one direction and the end of the position adjustment document is not included in the shifted reading range. It is possible to improve the detection accuracy of the end of the.
According to the sixth aspect of the present invention, it is possible to secure a region serving as the background of the end portion of the position adjustment document.

1 illustrates an exemplary configuration of an image forming apparatus to which the exemplary embodiment is applied. 2 shows an exemplary configuration of a paper guide to which the present embodiment is applied. 2 shows an example of a functional configuration of a general control unit to which the present embodiment is applied. (A) thru | or (f) is a figure explaining the element of a misalignment, and the correction method. It is a figure explaining the test chart to which this Embodiment is applied. (A) thru | or (d) is a figure explaining the edge detection mark with which this Embodiment is applied. (A) thru | or (c) is a figure explaining the relationship between a detected image and a reading image. (A) And (b) is a figure explaining adjustment of the trimming position in initial setting. (A) thru | or (c) is a figure explaining the adjustment of the trimming position in normal mode and adjustment mode. (A) And (b) is a figure explaining the positional relationship of the read image and 1st edge part-4th edge part in adjustment mode. It is a figure explaining switching of the adjustment mode of the alignment according to the change of the 1st edge part-the 4th edge part of the test chart settled in a read image. It is a figure explaining the switching aspect of a deviation | shift amount calculation formula. (A) And (b) is a figure explaining the switching aspect of a lead registration reference | standard edge part and a side registration reference | standard edge part. (A) thru | or (c) is a figure for demonstrating the change of the measurement point according to an edge part crack. (A) And (b) is a figure for demonstrating the change of the measurement point according to an edge part crack. (A) thru | or (c) is a figure explaining the switching aspect of a registration shift | offset | difference correction amount calculation formula. (A) thru | or (c) is a figure explaining the switching aspect of a registration shift | offset | difference correction amount calculation formula. It is the flowchart which showed the operation example of the alignment adjustment process in this Embodiment. It is the flowchart which showed the operation example of the analysis process of the test chart image in this Embodiment.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
<Image forming apparatus 1>
FIG. 1 shows a configuration example of an image forming apparatus 1 to which the exemplary embodiment is applied.
As shown in FIG. 1, the image forming apparatus 1 is a multi-function machine having a copy function, a printer function, a scanner function, a copy function, and the like. The illustrated image forming apparatus 1 includes a paper supply unit 3, an image forming unit 5, a user interface (UI) 7, an image reading unit 9, and a general control unit 10.

  The paper supply unit 3 mounts the paper S on which an image is formed by the image forming unit 5, and conveys the paper S one by one toward the image forming unit 5. In the illustrated example, the sheet supply unit 3 includes a first tray (stacking unit) 31, a second tray 32, and a third tray 33 on which sheets S are stacked (mounted). More specifically, the first tray 31, the second tray 32, and the third tray 33 can be loaded with sheets S having different sheet sizes, thicknesses, or sheet types.

The image forming unit 5 acquires image data, and forms an image on a recording medium such as a sheet S using an image forming material such as toner or ink based on the acquired image data. In this embodiment mode, an image formation method is not particularly limited, and can be applied to various methods such as an electrophotographic method, an inkjet method, and an electrostatic induction method. The image data may be received from an external device via a communication means (such as a network interface) (not shown), or an image read by the image reading unit 9 may be used. Further, the image forming unit 5 conveys the sheet S on which the image is formed on the first side while inverting the sheet S so as to form an image on each of both sides (first side and second side) of the sheet S. A reverse conveyance path (not shown) for forming an image on the second surface is provided.
The UI 7 is configured by a display panel, accepts an instruction from the user, and displays a message or the like to the user.

<Image reading unit 9>
The image reading unit (automatic document feeder) 9 reads the image formed on the sheet S while sequentially feeding the sheet S (document) on which the image is formed.
In the illustrated example, the image reading unit 9 includes a first document tray (stacking unit) 90 on which the sheets S are stacked, and a sheet having a transport roll that feeds the sheets S stacked on the first document tray 90 one by one. A conveying unit (feeding unit) 91; a first image sensor (reading unit) 92 that reads an image formed on the first surface while receiving light from the first surface of the sheet S conveyed by the sheet conveying unit 91; The mirror 93 for guiding the light from the second surface, which is the surface opposite to the first surface of the paper S conveyed by the paper conveying section 91, and the light from the second surface guided by the mirror 93 are received. And a second image sensor 94 for reading an image formed on the second surface.

  The image reading unit 9 also includes a first support member 95 that supports the sheet S that is provided and conveyed in the area where the first image sensor 92 reads an image, and a sheet that is provided and conveyed in the area of the second image sensor 94. A second support member 96 that supports S and a second document tray 97 on which sheets S on which images have been read are stacked. Further, the image reading unit 9 includes a paper guide 98 (described later) that defines the position of the paper S that is provided on the first document tray 90 and is conveyed.

  The first image sensor 92 is exemplified by using a line sensor, and the second image sensor 94 is exemplified by using a CCD (Charge Coupled Device) sensor. In the illustrated example, when the first image sensor 92 reads the image on the first side of the paper S, the second image sensor 94 reads the image on the second side of the paper S. As a result, the paper S is transported once in one direction by the paper transport unit 91, whereby the images on both sides (first surface and second surface) of the paper S are read.

<Paper guide 98>
FIG. 2 shows a configuration example of a paper guide 98 to which the present embodiment is applied.
Next, the configuration of the paper guide 98 will be described with reference to FIG.
As shown in FIG. 2, the paper guide 98 may be a direction (hereinafter referred to as a crossing direction) that intersects the transport direction of the paper S (feed direction; see arrow A in the figure; hereinafter, sometimes referred to as the transport direction). A pair of plate-like members 981 and 982 provided at positions sandwiching the sheets S stacked on the first document tray 90. Each surface of the plate-like members 981 and 982 is provided along the transport direction, and the end portions along the transport direction of the paper S are aligned. Further, the plate-like members 981 and 982 are movable in the intersecting direction while maintaining the respective surfaces along the transport direction (see arrow B in the figure).

Now, the plate-like members 981 and 982 are arranged so that the paper S is conveyed at the center, that is, by center registration.
Specifically, the plate-like members 981 and 982 are respectively disposed at equal distances from the middle line CL across the middle line CL in the intersecting direction of the area through which the sheet S to be conveyed passes. Further, as described above, when the plate-like members 981 and 982 move in the intersecting direction (see arrow B in the figure), the plate-like members 981 and 982 move while maintaining the same distance from the center line CL. As a result, the sheets S stacked on the first document tray 90 and sandwiched between the plate-like members 981 and 982 are conveyed with the center of the sheet S in the cross direction as a reference position. More specifically, even when the paper sizes of the paper S are different, the positions where the centers of the paper S pass are the same.

<General control unit 10>
FIG. 3 shows an example of a functional configuration of the integrated control unit 10 to which the present exemplary embodiment is applied.
Next, the general control unit 10 provided in the image forming apparatus 1 will be described with reference to FIG.
The comprehensive control unit 10 controls functional components (for example, the paper supply unit 3, the image forming unit 5, the UI 7, and the image reading unit 9) that constitute the image forming apparatus 1. The general control unit 10 includes a sheet supply control unit 13, an image formation control unit 15, a UI control unit 17, an image reading control unit 19, and an alignment adjustment unit 21 as functions thereof.

The paper supply control unit 13 controls the operation of the paper supply unit 3. Specifically, the paper supply control unit 13 controls the paper supply unit 3 to supply the paper S from one of the first tray 31 to the third tray 33 toward the image forming unit 5 in accordance with the print instruction.
The image formation control unit 15 controls the operation of the image formation unit 5. Specifically, the image formation control unit 15 controls the image forming unit 5 to form an image on the paper S supplied from the paper supply unit 3 in accordance with a print instruction.
The UI control unit 17 controls the operation of the UI 7. The UI control unit 17 displays screens for displaying predetermined messages to the user and controls the UI 7 to accept user instructions based on these screens.
The image reading control unit 19 controls the operation of the image reading unit 9. Specifically, in accordance with the reading instruction, the image reading unit 9 is controlled to read the image of the paper S mounted on the image reading unit 9.

The alignment adjustment unit (adjustment unit) 21 controls operations of the sheet supply unit 3, the image forming unit 5, the UI 7, and the image reading unit 9 when adjusting the position (alignment) of the image formed on the sheet S. Control is performed via the unit 13, the image formation control unit 15, the UI control unit 17, and the image reading control unit 19.
The alignment adjustment unit 21 functions as a test chart output unit 22, a test chart reading unit 23, a trim position determination unit 24, an image analysis unit 25, a mark image storage unit 26, and a read image storage unit 27. And a correction amount storage unit 28.

The test chart output unit 22 causes the paper supply unit 3 to supply the paper S in accordance with an instruction (test chart output instruction) to output a test chart TC (described later) from the user, and information stored in the mark image storage unit 26 Accordingly, the image forming unit 5 is caused to perform image formation.
The test chart reading unit 23 causes the image reading unit 9 to read an image of the test chart TC in accordance with an instruction (test chart reading instruction) for reading the test chart TC from the user.
The trim position determination unit 24 detects a read image R (see FIG. 7B described later) from a detected image Q (see FIG. 7A described later) that is an image detected by the first image sensor 92 and the second image sensor 94. ) To define the range to be cut and execute the cut.

The image analysis unit 25 analyzes the read image of the test chart TC, and based on the edge detection mark G (described later), the first end S1, the second end S2, the third end S3 of the test chart TC, The fourth end S4 (described later) is detected, and the amount of misalignment of the image formed on the sheet S by the image forming unit 5 is calculated based on the lattice mark H (described later) and the like.
The image analysis unit 25 includes, as its function, a measurement point detection unit 251, an end lack determination unit 252, a deviation amount calculation unit 253, and a correction amount calculation unit 254.

The measurement point detector 251 detects an edge detection mark G, a lattice mark H, and the like in the read image of the test chart TC.
Which of the first end S1 to the fourth end S4 of the test chart TC is included in the read image R is the end chipping determination unit (detection unit, switching unit, other switching unit, measurement unit) 252 ( Which is not included). Further, depending on which of the first end S1 to the fourth end S4 of the test chart TC is included in the read image R, an alignment deviation amount calculation formula (described later), the registration reference end of the test chart TC (Described later) and a correction amount calculation formula (described later) are determined (switched).

The deviation amount calculation unit 253 calculates the alignment deviation amount in accordance with the alignment deviation amount calculation formula determined by the edge missing determination unit 252 and the registration reference end of the test chart TC.
The correction amount calculation unit 254 calculates the alignment correction amount in accordance with the alignment correction amount calculation formula determined by the edge missing determination unit 252.

  The mark image storage unit 26 determines in advance a mark image formed on the test chart TC, that is, an edge detection mark G, a lattice mark H, a two-dimensional barcode J, an auxiliary image K, and an auxiliary line M (described later). Remember the image.

  The read image storage unit 27 stores an image of the test chart TC read and trimmed by the image reading unit 9. Here, the read image storage unit 27 includes information (tray identification information) indicating which image of the test chart TC is supplied from the first tray 31 to the third tray 33. ) And memorize it. Further, the read image storage unit 27 stores the image of the test chart TC in association with information (front and back identification information) indicating which image is the first surface or the second surface in the test chart TC. The read image storage unit 27 can store a plurality of test chart TC images.

  The correction amount storage unit 28 stores the alignment correction amount calculated by the correction amount calculation unit 254. Here, the correction amount storage unit 28 stores the alignment correction amount in association with the tray identification information and the front / back identification information for the test chart TC for which the alignment correction amount has been calculated.

  Although not shown in the figure, the general control unit 10 includes a CPU (Central Processing Unit) that is a calculation means, a main memory that is a storage means, and a magnetic disk device (HDD: Hard Disk Drive). Here, the CPU executes various types of software such as an OS (Operating System) and applications to realize the above-described functions. The main memory is a storage area for storing various software and data used for executing the software. The magnetic disk device is a storage area for storing input data for various software, output data from various software, and the like.

<Alignment deviation>
Now, when the image forming apparatus 1 repeatedly performs the image forming operation, for example, the functional constituent members constituting the image forming apparatus 1 may be worn or the positions of the functional constituent members may be shifted as time-dependent changes. As a result, the position of the image formed on the paper S may be shifted (varied) with respect to the paper S.
To further explain, for example, when images are formed on both sides of the paper S, the positions (front and back registration) of the images formed on the first surface and the second surface are not aligned and are shifted from each other. There is a case. Further, for reasons such as a change in conveyance resistance when the sheet S is conveyed, the first tray 31 corresponds to the type of the sheet S such as the sheet size, sheet type, or thickness of the sheet S. The position of the image formed on the paper S may be shifted (varied) with respect to the paper S depending on which one of the third trays 33 is supplied.

  In view of this, in the present embodiment, the image forming apparatus 1 has an adjustment mode for adjusting an image position deviation on the sheet S, that is, a so-called alignment deviation. In this adjustment mode, an alignment shift amount is calculated, and alignment correction is performed so as to cancel the shift amount. This adjustment mode can be regarded as a mode for generating image correction information by analyzing image information of a read image.

  Hereinafter, a process for adjusting the misalignment will be described. In the following, an element of misalignment and a correction method thereof will be described first. Next, a test chart TC used for measuring alignment deviation will be described. Thereafter, a relationship between the test chart TC and the read image R will be described, and finally, a process for correcting the alignment deviation will be specifically described.

<Elements of misalignment and correction method>
FIGS. 4A to 4F are diagrams for explaining an element of misalignment and a correction method. 4A to 4F, the relationship between the sheet S, the pre-correction image F that is an image formed before the misalignment correction, and the post-correction image T that is formed after the misalignment correction is completed. Are shown respectively. The position of the corrected image T can be regarded as an ideal position where an image is desired to be formed on the paper S.

  As shown in FIGS. 4A to 4F, the alignment deviation in the present embodiment is exemplified as being classified into the following components (elements). That is, the misalignment in the present embodiment is represented by one or a combination of the following six components, in other words, a combination of six types of geometric image deformation. In addition, the following components are illustrations and may of course include other components.

As shown in FIG. 4A, the lead registration is a scale indicating that the position of the image F before correction is shifted in the transport direction. The lead registration is corrected by moving the pre-correction image F along the conveyance direction as indicated by an arrow in the figure.
As shown in FIG. 4B, the side register is a scale indicating that the position of the image F before correction is shifted in the intersecting direction. The side registration is corrected by moving the pre-correction image F along the crossing direction as indicated by the arrows in the figure.
As shown in FIG. 4C, the sub-scanning magnification is a scale indicating the expansion / contraction of the pre-correction image F in the conveyance direction. The sub-scanning magnification is corrected by expanding / contracting the pre-correction image F in the transport direction with reference to a predetermined portion of the paper S (the upper side of the paper S in the figure).
As shown in FIG. 4D, the main scanning magnification is a scale indicating the expansion / contraction of the pre-correction image F in the intersecting direction. The main scanning magnification is corrected by expanding / contracting the pre-correction image F in the transport direction with reference to a predetermined portion of the paper S (the left side of the paper S in the figure).

As shown in FIG. 4E, the lead skew is a scale indicating the inclination of the pre-correction image F with respect to the intersecting direction. In the illustrated example, the lead skew is calculated by the difference between the distance A and the distance B. Further, the lead skew in the illustrated example is corrected by rotating the pre-correction image F so as to eliminate the difference between the distance A and the distance B, as indicated by arrows in the figure.
As shown in FIG. 4F, the side skew is a scale indicating the inclination of the pre-correction image F with respect to the transport direction. In the example shown in the figure, it is calculated by the difference between the distance A and the distance B. Further, the side skew in the illustrated example is corrected by rotating the pre-correction image F so as to eliminate the difference between the distance A and the distance B as indicated by arrows in the drawing.

<Test chart TC>
FIG. 5 is a diagram illustrating a test chart TC to which the present embodiment is applied.
Next, the test chart TC in the present embodiment will be described with reference to FIGS. 3 and 5.
First, the test chart (original, position-adjusted original) TC is obtained by forming an image stored in the mark image storage unit 26 on the paper S supplied from the paper supply unit 3 by the image forming unit 5. is there. The image of the test chart TC is read and analyzed by the image reading unit 9 to grasp the amount of misalignment.
Note that the image reading unit 9 of the present embodiment is used in common when, for example, the image forming apparatus 1 realizes a copy function and when the amount of misalignment is grasped. This eliminates the need to provide a dedicated image reading device (scanner) for grasping the amount of misalignment.

As shown in FIG. 5, the test chart TC includes an edge detection mark G, a lattice mark H, a two-dimensional barcode J, an auxiliary image K, an auxiliary line M, and an edge as images formed on the paper S. Point N is provided.
Here, although illustration is omitted, the test chart TC also has an image corresponding to the image shown in FIG. 5 formed on the surface (back surface) opposite to the surface shown in FIG. That is, in the test chart TC, images corresponding to FIG. 5 are formed on both surfaces (first surface, second surface). Then, by reading the test chart TC by the image reading unit 9, the amount of misalignment for each of the first surface and the second surface can be grasped. It should be noted that the test chart TC may of course have a configuration in which an image corresponding to FIG. 5 is formed on one surface (one surface) of the first surface and the second surface.

The edge detection mark G is a detection image for detecting (identifying) the first end S1 to the fourth end S4 of the paper S. The edge detection marks G are formed on the first end S1 to the fourth end S4 of the paper S, respectively. Specifically, in the test chart TC, a total of four edge detection marks G1, G2, G3, and G4 are formed. The shapes of the edge detection marks G1 to G4 will be described later.
The edge detection marks G1 to G4 are formed at predetermined positions with respect to the middle lines C1 and C2 of the first end S1 to the fourth end S4 of the paper S. More specifically, the edge detection marks G1 to G4 are arranged on a predetermined side with respect to the middle lines C1 and C2 and at a predetermined distance La from the middle lines C1 and C2. This distance La is constant regardless of the paper size of the paper S. In other words, even if the paper sizes are different, the distances from the middle lines C1 and C2 of the edge detection marks G1 to G4 formed on the test chart TC are the same.

  In the illustrated example, the distance from the middle lines C1 and C2 to the centers of the edge detection marks G1 to G4 in the directions along the first end S1 to the fourth end S4 is the distance La. ing. Each of the edge detection marks G1 to G4 has a first end S1 to a fourth end S4 as viewed from the first end S1 to the fourth end S4 side where the edge detection marks G1 to G4 are formed. Is located on the right side of the middle line C1 or the middle line C2. Further, the edge detection mark G1 and the edge detection mark G2 are provided on opposite sides of the middle lines C1 and C2, respectively, and the edge detection mark G3 and the edge detection mark G4 sandwich the middle lines C1 and C2, respectively. Are provided on opposite sides.

  Further, the edge detection marks G1 to G4 are disposed at a predetermined distance Lb from the first end S1 to the fourth end S4 where the edge detection marks G1 to G4 are formed. This distance Lb is constant regardless of the paper size of the paper S. In other words, even when the paper sizes are different, the distances from the first end S1 to the fourth end S4 of the edge detection marks G1 to G4 formed on the test chart TC are the same.

  More specifically, the edge detection marks G (the combination of the edge detection marks G1 and G2 and the combination of the edge detection marks G3 and G4) between the first end S1 to the fourth end S4 facing each other on the paper S are the middle line. Centered on the intersection C3 of C1 and the middle line C2, it is arranged at a point-symmetrical position. The intersection C3 can be regarded as the center of gravity of the paper S, and the edge detection marks G1 to G4 can be regarded as being arranged at point-symmetrical positions around the center of gravity of the paper S.

  The lattice mark (specific image) H is an image for detecting an image forming position or an image misalignment amount. The lattice mark H is a so-called registration mark in which two straight lines extending along the first end S1 to the fourth end S4 of the paper S are orthogonal to each other. In the illustrated test chart TC, a total of nine lattice marks H1, H2, H3, H4, H5, H6, H7, H8, and H9 are formed. The lattice marks H1 to H4 are formed at the four corners of the sheet S, and the lattice marks H5 to H8 are on the first end S1 to fourth end S4 side of the sheet S and on the middle lines C1 and C2. Is formed. These lattice marks H1 to H8 are formed at predetermined positions with respect to the first end S1 to the fourth end S4 that are close to each other. Specifically, they are arranged at a predetermined distance Lc from the first end S1 to the fourth end S4 that are close to each other. The lattice mark H9 is formed at the intersection C3 of the middle line C1 and the middle line C2.

  The two-dimensional barcode J is an image that holds predetermined information. In the illustrated example, a total of two two-dimensional barcodes J1 and J2 are formed on the third end S3 side and the fourth end S4 side of the paper S. The two-dimensional barcodes J1 and J2 indicate the paper size (A3, B5, etc.) of the paper S, which tray from the first tray 31 to the third tray 33, the plurality of test charts TC. Are continuously formed, information about the number of test charts TC and whether the surface of the paper S is the first surface or the second surface is held.

The auxiliary image K (K1, K2, K3) and the auxiliary line M (M1, M2) are used to detect the density of each color of the formed image, for example, the edge detection mark G, the lattice mark H, and the two-dimensional barcode. It is a detection image for detecting information other than what J holds.
The edge point N is a measurement point on the first end S1 to the fourth end S4 of the paper S. In the illustrated test chart TC, there are a total of eight edge points N including edge points N1, N2, N3, N4, N5, N6, N7, and N8 provided at positions corresponding to the lattice marks H1 to H8, respectively. . More specifically, the edge points N1 to N8 are respectively located at positions separated by a distance Lc from the lattice marks H1 to H8 of the paper S toward the outer edge of the paper S. In the illustrated example, the edge point N is not formed as a specific image (mark) in the test chart TC, but may be formed as an image.

<Edge detection marks G1 to G4>
6A to 6D are diagrams for explaining the edge detection mark G to which the present embodiment is applied.
Next, the edge detection marks G (G1 to G4) in the present embodiment will be described with reference to FIGS. 6 (a) to 6 (d).
The edge detection marks G1 to G4 in the present embodiment are provided on the first end S1 to the fourth end S4 of the paper S as described above, and the shapes thereof are different from each other. Then, by identifying the shape of each of the edge detection marks G1 to G4, the first end S1 to the fourth end S4 where the edge detection marks G1 to G4 are formed can be recognized. Further, detection of the first end S1 to the fourth end S4 is performed while adjusting a region for searching the first end S1 to the fourth end S4 with reference to the positions of the detected edge detection marks G1 to G4. Is executed.

As shown in FIGS. 6A to 6D, the edge detection marks G1 to G4 are configured by a combination of a start line G11, an end line G12, and identification lines G13, G14, and G15. The start line G11, the end line G12, and the identification lines G13 to G15 are substantially rectangular (straight line, line) images extending along the first end S1 to the fourth end S4 of the paper S, respectively.
The start line G11 is disposed on the first end S1 to the fourth end S4 side of the adjacent sheet S, and the end line G12 is disposed on the center side of the sheet S with respect to the start line G11. Furthermore, the identification lines G13 to G15 are provided between the start line G11 and the end line G12.

Here, as will be described later, the start line G11 indicates that the edge detection mark G starts to pass when performing the detection process while scanning the edge detection mark G (see the arrow in the figure). The start line G11 is wider (thicker) than the end line G12 and the identification lines G13 to G15.
The end line G12 indicates that the edge detection mark G is completely passed when the detection process is performed while scanning the edge detection mark G. The end line G12 is narrower than the start line G11 and wider than the identification lines G13 to G15.

The identification lines G13 to G15 are images for identifying each of the first end S1 to the fourth end S4. Each of the identification lines G13 to G15 has the same line width and is narrower (thin) than the start line G11 and the end line G12.
Here, as shown in FIGS. 6A to 6D, the edge detection mark G1 does not have the identification lines G13 to G15 (0 lines), and the edge detection mark G2 has the identification line G13 (one line). ), The edge detection mark G3 has identification lines G13 and G14 (two lines), and the edge detection mark G4 has identification lines G13 to G15 (three lines). In the present embodiment, it is recognized which of the edge detection marks G1 to G4 is by counting the number of identification lines G13 to G15 sandwiched between the start line G11 and the end line G12.

<Test chart TC and scanned image R>
<Trimming>
7A to 7C are diagrams for explaining the relationship between the detected image Q and the read image R. FIG.
Next, with reference to FIG. 1 and FIGS. 7A to 7C, the trimming that is performed when the image reading unit 9 reads the image of the paper S will be described.
Here, the image forming apparatus 1 executes a so-called copy function in which the first image sensor 92 of the image reading unit 9 reads an image on the sheet S and the image forming unit 5 forms an image of the read image. explain.

  As shown in FIG. 7A, the image read (detected) by the first image sensor 92 while the sheet S is conveyed by the sheet conveying unit 91 becomes the detected image Q. Here, in the crossing direction, the length of the detected image Q, in other words, the length of the area detected by the first image sensor 92 is longer than the length of the maximum width sheet S to be conveyed. From this, as shown in FIG. 7A, the image of the detected image Q is an image including an area outside the paper (background) around the paper S.

On the other hand, when the copy function is executed, the background around the paper S is not necessary. Therefore, the read image is cut to the paper size and the area outside the paper is deleted. Specifically, as shown in FIG. 7B, an area corresponding to the paper S in the detected image Q is left, and the other areas are deleted (trimmed). As a result, the read image R coincides with the area corresponding to the sheet S (see FIG. 7C). More specifically, the image data width of the read image R in the intersecting direction matches the width of the paper S.
Thus, by trimming the detected image Q to obtain the read image R, the transfer speed of the image data of the read image R is increased, or the amount of the buffer memory is reduced.

Here, it has been described that the image on the paper S is read by the first image sensor 92, but the same applies to the case where the image on the paper S is read by the second image sensor 94.
Here, the case where the copy function is executed has been described as an example, but the same applies to the case where the scanner function is executed in the image forming apparatus 1, for example. Note that the mode for executing the copy function and the scanner function may be referred to as a normal mode in contrast to the adjustment mode. Further, this normal mode can be regarded as a mode in which image information of the read image is stored in the storage means.
In addition, the detected image Q can be regarded as the maximum sensor readable area, and the read image R can be regarded as the maximum read image area.

<Initial setting of trimming position>
FIGS. 8A and 8B are diagrams for explaining the adjustment of the trimming position in the initial setting.
Next, adjustment of the trimming position in the initial setting will be described with reference to FIGS. 1, 8A and 8B.

First, as shown in FIG. 8A, a deviation occurs between the position of the read image R in the detected image Q and the position of the region corresponding to the paper S due to, for example, variations in the manufacturing process of the image forming apparatus 1. Sometimes. Therefore, for example, when the image forming apparatus 1 is shipped or installed, initial setting for adjusting the position of the read image R in the detected image Q is performed.
Specifically, as shown in FIG. 8B, the position of the read image R in the detected image Q is moved (adjusted), and the position of the read image R is made to coincide with the position of the region corresponding to the paper S. In the illustrated example, the read image R is moved from the position before the initial setting (see FIG. 8A) toward one side (right side in the figure) in the intersecting direction.
Note that the moving distance of the read image R in the illustrated example is the distance d1. In addition, the movement of the read image R at the initial setting may be simply referred to as an initial movement.

<Trimming position in normal mode and adjustment mode>
FIGS. 9A to 9C are diagrams for explaining the adjustment of the trimming position in the normal mode and the adjustment mode.
Next, the trimming positions in the normal mode and the adjustment mode in the present embodiment will be described with reference to FIGS. 5 and 9A to 9C.

First, as shown in FIG. 9A, in the normal mode, the position of the read image R in the detected image Q coincides with the position of the region corresponding to the paper S. Note that the position of the read image R in the normal mode is a position after being initially moved by the distance d1 in accordance with the initial setting as described above.
On the other hand, as shown in FIG. 9B, in the adjustment mode, the position of the read image R is shifted from the position of the read image R in the normal mode. The movement of the position of the read image R in the adjustment mode is executed by the trim position determination unit 24 (see FIG. 3) of the overall control unit 10.

  As described above, the position of the read image R is shifted in the adjustment mode for the following reason. First, when adjusting the misalignment, the test chart TC is used as described above. Then, the read image R obtained by reading the image of the test chart TC is analyzed, and the coordinates of the characteristic points (grid mark H or the like) for printing position measurement, or the first end S1 to the fourth end S4 of the test chart TC. The coordinates of (edge points N1 to N12) are acquired. Then, the amount of misalignment is calculated by measuring the position of each feature point coordinate with reference to the coordinates of the first end S1 to the fourth end S4.

  At this time, when the position of the read image R is made to coincide with the position of the region corresponding to the test chart TC as in the normal mode, for example, when the paper size of the test chart TC is large, the crossing of the test chart TC will be described further. When the direction length is large, the first end portions S1 to S4 in the read image R are affected by variations in the transport position (travel position) of the first image sensor 92, the second image sensor 94, and the test chart TC. There is a case where the end S4 cannot be accommodated (image missing). As a result, the coordinates of the first end S1 to the fourth end S4 cannot be obtained from the read image R.

  Therefore, in the adjustment mode of the present embodiment, as shown in FIG. 9B, the position of the read image R is shifted from the position of the read image R in the normal mode (the position of the region corresponding to the test chart TC). As a result, it is possible to ensure that the other end portions are accommodated in the read image R while allowing a portion of the first end portion S1 to the fourth end portion S4 to not fit in the read image R. In the illustrated example, the position of the read image R is moved by a distance d2 from the position in the normal mode toward one side (left side in the figure) in the crossing direction.

  Now, in particular, when the paper S of the test chart TC is a thin paper, and under the condition that the contrast of the boundary between the test chart TC and its background is low, the area outside the paper (background) in the read image R is narrow, Detection of the first end S1 to the fourth end S4 may be erroneously detected. Alternatively, the detection of the first end S1 to the fourth end S4 itself may be difficult. This is because, if the background area is narrow, the influence is increased when an image other than the test chart TC that causes an error, such as dirt or dust reflected in the read image R, is detected.

  Therefore, in the present embodiment, by shifting the position of the read image R from the position of the region corresponding to the test chart TC, the first end S1 to the fourth end S4 stored in the read image R are changed. The background around one of the ends (the fourth end S4 in the illustrated example) is widened. By widening the background area, the fourth end S4 can be easily detected. Further, by shifting the position of the read image R, it is not necessary to greatly widen the entire range of the read image R, and the length in the cross direction of the first image sensor 92 (see FIG. 7A) is suppressed.

  More specifically, even when the test chart TC is a sheet having the maximum width that can be conveyed, a part of the first end S1 to the fourth end S4 of the test chart TC is a read image. The other end is surely stored in the read image R while allowing it to not fit in R. In other words, for example, when the paper size is the maximum width of the A4 long edge that can be conveyed, the paper is conveyed with the A4 long edge as the leading edge in the conveyance direction, and the image is read. Is possible. This shortens the reading time as compared with the case where the length of the longitudinal end portion of A4 is conveyed in the direction along the conveyance direction.

  In the example shown in FIG. 9B, it has been described that the position of the read image R is moved by the distance d2 from the position of the normal mode. This distance d2 is set as a predetermined distance within a range equal to or less than the maximum distance in which the read image R can be moved. The distance d2 is stored in advance by, for example, the trim position determination unit 24 (see FIG. 3). When the adjustment mode is selected by the user (described later), the position of the read image R is adjusted according to the distance d2 stored in the trim position determination unit 24.

  Even when the distance d2 is set to be equal to or less than the maximum movable distance of the read image R, depending on the movement distance (distance d1, see FIG. 9A) due to the initial movement, the distance d2 It may not be possible to move. Specifically, when the sum of the distance d1 and the distance d2 exceeds the maximum movable distance of the read image R, the read image R cannot be moved by the distance d2.

Therefore, in the present embodiment, the trim position determination unit 24 (see FIG. 3) calculates the sum of the distance d1 and the distance d2, and determines whether or not the sum exceeds the maximum movable distance of the read image R. Judging.
Then, as shown in FIG. 9C, when the sum of the distance d1 and the distance d2 exceeds the maximum movable distance of the read image R, the direction opposite to the distance d2, and further described in the cross direction. The read image R is moved by a distance d3 toward the other side (right side in the figure). As a result, a part of the first end S1 to the fourth end S4 is accommodated in the read image R, and the size of the background region is secured.

The distance d1, the distance d2, the maximum distance, and the distance d3 may be stored in advance in the trim position determination unit 24. Further, the distance d3 is determined as a distance that can be moved by the maximum amount in a direction opposite to the distance d2, for example.
Further, the above aspect can be regarded as an aspect in which the direction in which the read image R is shifted in the adjustment mode is determined according to the adjustment value (the moving distance of the initial movement, the distance d1) of the image reading unit 9.

Here, in the above description, it has been described that the read image R is moved while maintaining the size (size) of the read image R. However, the present invention is not limited to this.
For example, the read image R in the adjustment mode may be larger than the read image R in the normal mode. Specifically, the read image R in the adjustment mode may be the size of the detected image Q (trimming is not performed), or may be an area that is smaller than the detected image Q and larger than the paper S.

Alternatively, the read image R in the adjustment mode may be an area substantially equal to or smaller than the paper S. Further, the read image R in the adjustment mode may be composed of a plurality of areas. Specifically, the read image R in the adjustment mode may be composed of a plurality of areas smaller than the paper S.
Note that these read images R are preferably at positions where at least one of the first end S1 to the fourth end S4 of the paper S is accommodated.

<Position of first end S1 to fourth end S4 in the adjustment mode>
10A and 10B are diagrams illustrating the positional relationship between the read image R and the first end S1 to the fourth end S4 in the adjustment mode.
Next, the positional relationship between the read image R and the first end S1 to the fourth end S4 of the test chart TC in the adjustment mode will be described with reference to FIGS. 10 (a) and 10 (b).
As described above, in the adjustment mode, the position of the read image R is shifted. As a result, as described above, a part of the first end S1 to the fourth end S4 of the test chart TC may not fit in the read image R. In particular, when the paper size of the test chart TC is large, and further described, when the length of the test chart TC in the crossing direction is long, either of the both ends (the third end S3 and the fourth end S4) in the crossing direction. May not fit in the read image R.

Specifically, as shown in FIG. 10A, when the first end S1 to the fourth end S4 of the test chart TC fit within the read image R, the edge of the test chart TC All of the points N1 to N12 are in the read image R.
On the other hand, as shown in FIG. 10B, when only the first end S1 to the third end S3 of the test chart TC are within the read image R, only the edge points N1 to N9 are included in the read image R. Will be in a state that fits.

Here, as described above, when adjusting the misalignment, the misalignment amount is calculated using the coordinates of the first end S1 to the fourth end S4 (edge points N1 to N12). On the other hand, for example, as illustrated in FIG. 10B, it is desirable that the alignment adjustment be reliably performed even when the fourth end S <b> 4 of the test chart TC does not fit in the read image R. .
Therefore, in the present embodiment, which of the first end S1 to the fourth end S4 of the test chart TC is within the read image R, in other words, the first end S1 of the test chart TC. To determine which of the fourth ends S4 does not fit (is missing) in the read image R, and switches the alignment adjustment mode according to the determination result.
Note that which end of the first end S1 to the fourth end S4 of the test chart TC is missing in the read image R is determined based on the paper size of the test chart TC and the first document tray 90 of the test chart TC. It changes depending on the mounting direction, the moving distance d1 of the initial movement, etc., and it is difficult to grasp in advance the missing end.

<Switching alignment adjustment mode>
FIG. 11 is a diagram for explaining switching of the alignment adjustment mode according to changes in the first end S1 to the fourth end S4 of the test chart TC that fits in the read image R.
Next, referring to FIGS. 3, 10, and 11, the switching of the alignment adjustment mode according to changes in the first end S <b> 1 to the fourth end S <b> 4 of the test chart TC that fits in the read image R is specifically described. I will explain it.

First, switching of the alignment adjustment mode is executed by the edge missing determination unit 242 (see FIG. 3) of the image analysis unit 25.
Specifically, the edge missing determination unit 242 determines which one of the first end S1 to the fourth end S4 of the test chart TC is not included in the read image R (edge missing).
Next, the edge missing determination unit 242 changes the algorithm for calculating the alignment shift correction amount according to the determination result of the edge missing. More specifically, the edge missing determination unit 242 includes an alignment shift amount calculation formula (an example of a position calculation formula such as a main scanning magnification calculation formula and a sub-scanning magnification calculation formula), and a registration reference end (lead registration) of the test chart TC. And at least one of an alignment correction amount calculation formula (such as a lead registration correction amount calculation formula and a side registration correction calculation formula).

  Here, referring to FIG. 11, the determination result of the edge missing, the main scanning magnification calculation formula, the sub-scanning magnification calculation formula, the lead registration reference end, the side registration reference end, the lead registration correction amount calculation formula, and the side registration correction amount calculation. Each combination of formulas will be described, and specific aspects of the main scanning magnification calculation formula, sub-scanning magnification calculation formula, lead registration reference end, side registration reference end, lead registration correction amount calculation formula, and side registration correction amount calculation formula Will be described later.

  First, as shown in FIG. 11, when there is no edge missing, that is, when the first end S <b> 1 to the fourth end S <b> 4 are within the read image R, the main scanning magnification calculation formula and the sub-scanning magnification calculation are performed. The formula is a normal formula. The lead registration reference end is the third end S3, and the side registration reference end is the second end S2. The lead registration correction amount calculation formula and the side registration correction amount calculation formula are normal formulas.

Next, when the edge missing is the first end S1, that is, when the second end S2 to the fourth end S4 are within the read image R, the main scanning magnification calculation formula is an alternative formula, sub-scanning The magnification calculation formula is a normal formula. The lead registration reference end is the third end S3, and the side registration reference end is the second end S2. The lead registration correction amount calculation formula and the side registration correction amount calculation formula are normal formulas.
Next, when the end chip is the second end S2, that is, when the first end S1, the third end S3, and the fourth end S4 are within the read image R, the main scanning magnification calculation formula Is an alternative formula, and the sub-scan magnification calculation formula is a normal formula. The lead registration reference end is the third end S3, and the side registration reference end is the first end S1. The lead registration correction amount calculation formula is a normal formula, and the side registration correction amount calculation formula is an alternative formula.

Next, when the end chipping is the third end S3, that is, when the first end S1, the second end S2, and the fourth end S4 are within the read image R, the main scanning magnification calculation formula Is a normal formula, and the sub-scanning magnification calculation formula is an alternative formula. The lead registration reference end is the fourth end S4, and the side registration reference end is the second end S2. The lead registration correction amount calculation formula is an alternative formula, and the side registration correction amount calculation formula is a normal formula.
Next, when the edge missing portion is the fourth end S4, that is, when the first end S1 to the third end S3 are within the read image R, the main scanning magnification calculation formula is the normal formula and the sub-scanning formula. The magnification calculation formula is an alternative formula. The lead registration reference end is the third end S3, and the side registration reference end is the second end S2. The lead registration correction amount calculation formula and the side registration correction amount calculation formula are normal formulas.

  Note that the switching of the alignment adjustment mode according to the change in the first end S1 to the fourth end S4 of the test chart TC that fits in the read image R is performed by, for example, the table shown in FIG. It is executed by storing in advance and referring to the stored table.

<Switching mode between main scanning magnification calculation formula and sub-scanning magnification calculation formula>
FIG. 12 is a diagram for explaining a switching mode of the deviation amount calculation formula.
Next, a normal expression and an alternative expression in the main scanning magnification calculation formula and the sub-scanning magnification calculation expression will be described with reference to FIG. In FIG. 12, switching of main scanning magnification (magnification in the crossing direction) will be described as an example.

First, in both the normal type and the alternative type, the main scanning magnification is measured based on the length between the lattice marks H. Specifically, the main scanning magnification is measured based on the length between the lattice marks H5 and the lattice marks H6 formed at both ends of the test chart TC in the intersecting direction.
Next, the normal formula will be described. In the normal equation, the length between the lattice mark H5 and the lattice mark H6 is not directly measured, but the length of the paper S, the distance d4 from the edge point N5 to the lattice mark H6, and the lattice mark H5 to the edge point N2 The length between the lattice mark H5 and the lattice mark H6 is calculated from the distance d5 up to. That is, the formula for calculating the length between the lattice mark H5 and the lattice mark H6 is paper length−distance d4−distance d5. The paper length can be obtained by referring to information held in the above-described two-dimensional barcode J, for example.

  As described above, in the normal formula, the length between the lattice mark H5 and the lattice mark H6 is not directly measured, but indirectly measured for the following reason. For example, in general, when measuring the distance between the measurement points on the test chart TC, an error caused by the image reading unit 9 (see FIG. 1) reading the image while transporting the test chart TC is, for example, The longer the distance between the measurement points, the larger. Therefore, in the normal formula, in order to suppress the detection error between the measurement points, a shorter distance between the measurement points, that is, the distance d4 from the edge point N5 to the lattice mark H6 and the distance d5 from the lattice mark H5 to the edge point N2 are used. Thus, the length between the lattice mark H5 and the lattice mark H6 is obtained.

  In this normal expression, the edge point N2 and the edge point N5 are used as described above. That is, in the normal formula, both ends (the first end S1 and the second end S2) of the direction (in the crossing direction in the illustrated example) in which the main scanning magnification is to be measured in the test chart TC are included in the read image R. It is necessary.

Next, an alternative formula will be described. In the alternative formula, unlike the normal formula, the length (distance d6) between the grid mark H5 and the grid mark H6 is directly measured.
In this alternative formula, the detection error can be large as described above when compared with the normal formula. On the other hand, unlike the normal formula, both ends (the first end S1 and the second end S2) of the direction in which the main scanning magnification is measured in the test chart TC (the crossing direction in the illustrated example) are read images R. It is not necessary to fit in.

As described above, in the present embodiment, both ends (first end S1 and second end S2) in the direction (in the crossing direction in the example of FIG. 12) in which the main scanning magnification is to be measured in the test chart TC. Is used in the read image R, the normal formula (paper standard) is adopted, and if either of the two ends does not fit in the read image R, the alternative formula (scanner standard) is adopted (see FIG. 11).
Although the main scanning magnification has been described here, the same applies to the case of switching the sub scanning magnification.

<Switching mode between lead registration reference end and side registration reference end>
FIGS. 13A and 13B are diagrams for explaining a switching mode between the lead registration reference end and the side registration reference end.
Next, switching between the lead registration reference end and the side registration reference end will be described with reference to FIGS.

First, as shown in FIG. 13A, when there is no end chipping, that is, when the first end S1 to the fourth end S4 are within the read image R, it becomes a reference for measuring the lead registration. The lead registration reference end that is the end is the third end S3, and the side registration reference end that is a reference for measuring the side registration is the second end S2. More specifically, in FIG. 13A, the lead registration is measured by the distance d7 from the edge point N8 to the lattice mark H7, and the side registration is measured by the distance d8 from the edge point N5 to the lattice mark H6.
Note that the lead registration reference end (the third end S3 in the example shown) and the side registration reference end (the second end S2 in the example shown) when there is no end chipping are respectively the normal lead registration reference end and Usually, it may be the side registration reference end.

  Next, as shown in FIG. 13 (b), when the end chip is the second end S2, that is, the first end S1, the third end S3, and the fourth end S4 are in the read image R. If they fit, the lead registration reference end, which is a reference end for measuring the lead registration, is the third end S3, and the side registration reference end, which is a reference for measuring the side registration, is the first end S1. . More specifically, in FIG. 13B, the lead registration is measured by the distance d9 from the edge point N8 to the lattice mark H7, and the side registration is measured by the distance d10 from the edge point N2 to the lattice mark H5.

  As described above, in the present embodiment, the normal lead registration reference end (third end S3 in the illustrated example) or the normal side registration reference end (second end S2 in the illustrated) is included in the read image R. If not, the end portion of the test chart TC facing the normal lead registration reference end portion (the fourth end portion S4 in the illustrated example) or the end portion facing the normal side registration reference end portion (in the illustrated example, the first end portion). Switching is performed so that one end S1) becomes a reference (see FIG. 11).

<Changes in measurement points>
14 (a) to 14 (c), 15 (a) and 15 (b) are diagrams for explaining the change of the measurement point in accordance with the chipped end.
Next, the change of the measurement point according to the edge chip will be described with reference to FIGS. 14 (a) to 14 (c) and FIGS. 15 (a) and 15 (b).
First, as a premise, in the present embodiment, as described above, which of the first end S1 to the fourth end S4 of the test chart TC is missing in the read image R (end missing). Accordingly, the lead registration reference end and the side registration reference end are switched. A specific description will be given of a change in the measurement point on the test chart TC when calculating the amount of misalignment by switching between the lead registration reference end and the side registration reference end.

  First, as shown in FIG. 14A, when there is no end chipping, the lead registration reference end is the third end S3, and the side registration reference end is the second end S2. Therefore, the lead register is calculated by the distance P11 with the third end S3 as a reference, and the side register is calculated by the distance P12 with the second end S2 as a reference. The lead skew is calculated from the distances P13 and P14, and the side skew is calculated from the distances P15 and P16. The main scanning magnification is calculated from the distances P11 and 17 as the paper reference, and the sub-scanning magnification is calculated from the distances P12 and 18 as the paper reference.

  As shown in FIG. 14B, when the end chip is the first end S1, the lead registration reference end is the third end S3, and the side registration reference end is the second end S2. Therefore, the lead register is calculated by the distance P21 with the third end S3 as a reference, and the side register is calculated by the distance P22 with the second end S2 as a reference. The lead skew is calculated from the distances P23 and P24, and the side skew is calculated from the distances P25 and P26. The sub-scanning magnification is calculated from the distances P21 and 27 as the paper reference, and the main scanning magnification is calculated from the distance P28 as the scanner reference.

  As shown in FIG. 14C, when the end chip is the second end S2, the lead registration reference end is the third end S3, and the side registration reference end is the first end S1. Therefore, the lead register is calculated by the distance P31 with the third end S3 as a reference, and the side register is calculated by the distance P32 with the first end S1 as a reference. Further, the lead skew is calculated from the distances P33 and P34, and the side skew is calculated from the distances P35 and P36. The sub-scanning magnification is calculated from the distances P31 and 37 as the paper reference, and the main scanning magnification is calculated from the distance P38 as the scanner reference.

  As shown in FIG. 15A, when the end chip is the third end S3, the lead registration reference end is the fourth end S4, and the side registration reference end is the second end S2. Therefore, the lead registration is calculated by the distance P41 based on the fourth end portion S4, and the side registration is calculated by the distance P42 based on the second end portion S2. The lead skew is calculated from the distances P43 and 44, and the side skew is calculated from the distances P45 and 46. The sub-scanning magnification is calculated from the distance P47 as the scanner reference, and the main scanning magnification is calculated from the distances P42 and P48 as the paper reference.

  As shown in FIG. 15B, when the end chip is the fourth end S4, the lead registration reference end is the third end S3, and the side registration reference end is the second end S2. Accordingly, the lead registration is calculated by the distance P51 based on the third end S3, and the side registration is calculated by the distance P52 based on the second end S2. The lead skew is calculated from the distances P53 and 54, and the side skew is calculated from the distances P55 and P56. The sub-scanning magnification is calculated from the distance P57 as the scanner reference, and the main scanning magnification is calculated from the distances P52 and 58 as the paper reference.

<Switching mode of registration deviation correction amount calculation formula>
FIGS. 16A to 16C and FIGS. 17A to 17C are diagrams for explaining a switching mode of the registration deviation correction amount calculation formula.
Next, switching of the registration deviation correction amount calculation formula will be described with reference to FIGS. 11, 13A and 13B, FIGS. 16A to 16C, and FIGS. 17A to 17C. To do.

  First, as described above with reference to FIGS. 13A and 13B, any one of the first end S1 to the fourth end S4 of the test chart TC is in the read image R. The lead registration reference end and the side registration reference end are switched depending on whether the chip is missing (edge missing). In the present embodiment, as one of the lead registration reference end and the side registration reference end is switched, the registration deviation correction amount calculation formula for the lead registration and the side registration is switched.

  Hereinafter, side registration (in the illustrated example, the shift in the crossing direction) will be described. In FIGS. 16A to 16C and FIGS. 17A to 17C, as an example of the misalignment, a case where a misalignment of the side registration and the main scanning magnification occurs is assumed. 16A to 16C and FIGS. 17A to 17C are not the test chart TC (see FIG. 13), but the sheet S and an image formed before the misalignment correction. A description will be given based on the relationship between the pre-correction image F and the post-correction image T formed after completion of the alignment shift correction. The position of the corrected image T can be regarded as an ideal position where an image is desired to be formed on the paper S.

First, FIGS. 16A to 16C show a case where there is no end chipping (see FIG. 14A). Here, as described above, the side registration reference end in the test chart TC is the second end S2 which is the normal side registration reference end. Here, the first end S5 in the paper S corresponds to the second end S2 of the test chart TC. The second end S6 of the paper S corresponds to the first end S1 of the test chart TC.
As shown in FIG. 16A, the amount measured as the side registration deviation before correction is the distance Da. Here, as described above, in FIG. 16A, the side registration and the main scanning magnification are shifted. In this case, as the main scanning magnification is corrected, the correction amount of the side registration may change due to the correction mutual influence between the components of the misalignment.

More specifically, as shown in FIG. 16B, when the main scanning magnification is adjusted, the pre-correction image F is fixed with the first end S5 (left side) of the paper S fixed. Is extended in the direction along the main scanning direction (crossing direction) and toward the second end S6. The position of the pre-correction image F in which the main scanning magnification is adjusted is in a state of being shifted by a distance Db from the ideal position in the crossing direction. Further, the deviation of the distance Db at this time is measured on the first end S5 side.
Then, as shown in FIG. 16C, when adjusting the side registration, the position of the pre-correction image F in which the main scanning magnification is adjusted is moved (translated) along the intersecting direction (distance). Dc).

At this time, the correction amount of the side registration is calculated by the following equation.
Dc = Db (1)

Further, as shown in FIGS. 16A to 16C, when the side registration deviation is measured with reference to the second end S2 of the test chart TC which is the normal side registration reference end, the side registration deviation amount is the main scanning magnification. Since the influence of the adjustment is small, it is calculated by the following formula.
Db = Da (2)

Therefore, the correction amount of the side registration is calculated by the following formula (normal formula).
Dc = Da (3)

Next, FIGS. 17A to 17C show the case where the end chipping in the test chart TC is the second end S2 (see FIG. 14C). The side registration reference end of the test chart TC in this example is a first end S1 that is an end facing the normal side registration reference end.
As shown in FIG. 17A, the amount measured as the side registration deviation before correction is the distance Da.

Next, as shown in FIG. 17B, when adjusting the main scanning magnification, the uncorrected image F is displayed in the main scanning direction with the first end S5 (left side) of the paper S fixed. It extends in the direction along the (crossing direction) and toward the second end S6. The position of the pre-correction image F in which the main scanning magnification is adjusted is in a state of being shifted by a distance Db from the ideal position in the crossing direction. Further, the shift of the distance Db at this time is measured on the second end portion S6 side.
Then, as shown in FIG. 17C, when adjusting the side registration, the position of the pre-correction image F in which the main scanning magnification is adjusted is moved along the intersecting direction (see the distance Dc).

At this time, the correction amount of the side registration is calculated by the following equation.
Dc = Db (4)

Further, as shown in FIGS. 17A to 17C, when the side registration deviation is measured with reference to the first end S1 of the test chart TC which is the end opposed to the normal side registration reference end, the side registration deviation is shifted. Since the amount is affected by the adjustment of the main scanning magnification, it is calculated by the following equation.
Db = Da−magnification correction amount (5)

Therefore, the correction amount of the side registration is calculated by the following equation (alternative equation).
Dc = Da−magnification correction amount (6)

As described above, in the present embodiment, when the side registration reference end is the normal side registration reference end, Expression (3) is used as the normal expression for calculating the side registration correction amount, and the normal side registration reference is used. If it is not the end portion, it is switched to use the formula (6) as an alternative formula of the side register correction amount calculation formula (see FIG. 11).
Here, the correction amount calculation formula for the side registration has been described, but the same applies when switching the correction amount calculation formula for the lead registration.

<Alignment adjustment process>
FIG. 18 is a flowchart showing an operation example of the alignment adjustment processing in the present embodiment.
Next, an operation example of the alignment adjustment process in the present embodiment will be described.
First, the test chart output unit 22 receives selection of an adjustment mode, for example, when the user operates the UI 7 (step 1801). In addition, the test chart output unit 22 receives a test chart output instruction when the user operates the UI 7 (step 1802). Then, the test chart output unit 22 forms an image on the paper S and outputs it as a test chart TC (step 1803).

  Next, the test chart reading unit 23 receives a test chart reading instruction when the user operates the UI 7 (step 1804). Then, after the trim position is adjusted by the trim position determination unit 24 (step 1805), the test chart reading unit 23 reads (detects) the test chart TC (step 1806).

Next, after trimming the image of the test chart TC detected by the trim position determination unit 24 (detected image Q, see FIG. 7A) (step 1807), the read image storage unit 27 reads the trimmed image. The image R is stored (step 1808).
Next, the image analysis unit 25 analyzes the read image R stored in the read image storage unit 27 (step 1809, described later). Then, the correction amount storage unit 28 stores a correction amount for correcting the alignment deviation amount calculated by the image analysis unit 25 (step 1810).

  The alignment adjustment unit 21 corrects the alignment deviation according to the correction amount stored in the correction amount storage unit 28 before the image forming unit 5 forms an image on the paper S in the normal mode, for example. Specifically, the alignment adjustment unit 21 corrects the image side, such as correction processing of the formation position of the image formed by the image forming unit 5 or correction processing of the magnification of the image, or the first tray 31 to the third tray. Various correction processes such as correction of the sheet S side such as correction processing of the sheet loading position 33 and correction processing of the feeding timing of the sheet S supplied from the first tray 31 to the third tray 33 are performed.

<Test chart image analysis processing>
FIG. 19 is a flowchart showing an operation example of the analysis process of the test chart image in the present embodiment.
Next, an example of the operation of the image analysis process of the test chart TC (see step 1809 in FIG. 18) performed by the image analysis unit 25 will be described in detail with reference to FIG.

First, the measurement point detector 251 detects and analyzes the edge detection marks G (G1 to G4) formed at each end (first end S1 to fourth end S4) (step 1901). At this time, the image analysis unit 25 specifies the arrangement of the first end S1 to the fourth end S4, that is, the direction of the test chart TC from the analysis result of the detected edge detection mark G.
Further, the measurement point detector 251 detects and analyzes the two-dimensional barcode J (step 1902). At this time, the image analysis unit 25 analyzes the two-dimensional barcode J, and acquires the sheet size, more specifically, the length of the test chart TC in the transport direction and the crossing direction.

Next, the measurement point detector 251 detects the lattice mark H (step 1903), and detects the edge point N based on the detected position of the lattice mark H (step 1904). Then, the end chipping determination unit 252 determines end chipping based on the detected edge point N (step 1905).
Next, the edge missing determination unit 252 determines a deviation amount calculation formula according to the edge missing determination result (step 1906). Then, the deviation amount calculation unit 253 calculates an alignment deviation amount according to the determined deviation amount calculation formula (step 1907).
Further, the edge missing determination unit 252 determines a correction amount calculation formula according to the edge missing determination result (see step 1905) (step 1908). Then, the correction amount calculation unit 254 calculates an alignment deviation correction amount according to the determined correction amount calculation formula (step 1909).

<Modification>
Although the description is omitted in the above description, the read image storage unit 27 may store images read for each of the first tray 31, the second tray 32, and the third tray 33. Alternatively, the image may be further subdivided and stored for each type of paper S loaded in the first tray 31 to the third tray 33. By analyzing the image stored for each type of the sheet S and adjusting the amount of misalignment, the sheet S is supplied from any of the first tray 31 to the third tray 33 or the type of the sheet S is determined. The adjustment amount of the misalignment amount that can change accordingly can be corrected more accurately.

  In the above description, it has been described that the image reading unit 9 reads the image while the test chart TC is conveyed by the sheet conveying unit 91, but the present invention is not limited to this. That is, without conveying the test chart TC by the sheet conveying unit 91, for example, an image of the test chart TC arranged (fixed) at a predetermined position in the image forming apparatus 1 such as a so-called platen (not shown), A mode in which reading is performed by the second image sensor 94 while scanning by the mirror 93 may be employed. The alignment misalignment adjustment process described above can also be executed on an image read in this mode.

  Further, in the above description, it is described that the alignment deviation adjustment process is switched depending on which end of the first end S1 to the fourth end S4 of the test chart TC is missing in the read image R. However, it is not limited to this. For example, even when the first end S1 to the fourth end S4 of the test chart TC are in the read image R, the above-described misalignment adjustment process can be executed. More specifically, when the first end S1 to the fourth end S4 of the test chart TC are within the read image R, the contrast at any of the first end S1 to the fourth end S4 is low. When the detection of the first end portion S1 to the fourth end portion S4 is difficult, the above-described misalignment adjustment processing may be executed.

Although various embodiments and modifications have been described above, it is of course possible to combine these embodiments and modifications.
Further, the present disclosure is not limited to the above-described embodiment, and can be implemented in various forms without departing from the gist of the present disclosure.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 10 ... Total control part, 21 ... Alignment adjustment part, 22 ... Test chart output part, 23 ... Test chart reading part, 24 ... Trim position determination part, 25 ... Image analysis part, 251 ... Measurement point detection , 252... Missing edge determination unit, 27... Read image storage unit, 28... Correction amount storage unit, TC.

Claims (7)

An image forming unit;
A reading unit that feeds a document formed by the image forming unit and that reads the image of the document that has been sent;
Detecting means for detecting an end portion of a document included in the image read by the reading means;
An image forming system comprising: a switching unit that switches a calculation formula for calculating an adjustment amount of a position at which the image forming unit forms an image on a sheet depending on the presence or absence of an edge of the document detected by the detecting unit. apparatus.   2. The image forming apparatus according to claim 1, wherein the switching unit switches the calculation formula depending on which end portion of the document is detected by the detection unit or which end portion of the document is not detected. apparatus.   According to another aspect of the invention, there is provided another switching unit that switches a position calculation formula for calculating a position of the specific image formed on the document in the document according to the presence or absence of the edge of the document detected by the detection unit. The image forming apparatus according to claim 1.   When the edge of the document serving as a reference for measuring the position of the specific image formed on the document is not detected by the detection means, the specific is performed based on the edge of the document facing the edge serving as the reference. 4. The image forming apparatus according to claim 1, further comprising a measuring unit that measures the position of the image.   The reading unit is configured to read a predetermined document other than the position adjustment document when the image forming unit reads the position adjustment document which is the document for adjusting the position where the image is formed on the sheet. 5. The image formation according to claim 1, wherein the reading range is shifted by a predetermined distance in one direction, and the end of the position adjustment document is included in the shifted reading range. apparatus.   6. The image forming apparatus according to claim 5, wherein the reading unit shifts the reading range in a direction opposite to the one direction when the reading range cannot be shifted in the one direction by the predetermined distance. apparatus. An image forming unit;
Feeding means for feeding a document formed by the image forming unit;
Reading means for reading the document sent by the feeding means;
Detecting means for detecting a specific image formed at a predetermined position in the document having the maximum width in an image in which the document having the maximum width that can be read by the reading unit is read by the reading unit;
An image forming apparatus, comprising: an adjusting unit that adjusts a position at which the image forming unit forms an image on a sheet based on a position of the specific image detected by the detecting unit in the document having the maximum width. .

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