JP2016118674A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus which can form a pattern image for calibration capable of suppressing an influence of flare on read data.SOLUTION: An image forming apparatus G comprises an image forming part 8 which forms an image on a sheet, and a control part which controls the image forming part 8 to form a pattern image for calibration on a sheet. The pattern image is formed by arranging a plurality of patches having different gradations adjacent to each other, and the plurality of patches each has a first area part including an effective area for acquiring read data for calibration inside thereof. Patches positioned on the outer periphery of the pattern image (outer peripheral patches) each has a second area part widened outward in the same gradation as the gradation of the first area part.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image forming apparatus.

  2. Description of the Related Art Conventionally, an electrophotographic image forming apparatus is known as a multi-function peripheral (MFP) having a composite function of a printer, a copier, and the like. In this image forming apparatus, calibration for adjusting the characteristics of the image forming apparatus is executed in order to realize optimum color reproducibility. Calibration is a process of updating the gradation characteristics (γ correction curve (LUT)) of each color of C (cyan), M (magenta), Y (yellow), and K (black) used for image formation.

  When this calibration is performed, a pattern image in which a plurality of patches having different gradations are arranged adjacent to each other is formed on a sheet, and the sheet on which the pattern image is formed is optically read. Then, the tone characteristics (γ correction curve (LUT)) are updated based on the read data regarding each patch.

  In general, optical reading of a pattern image is performed by a line sensor having optical elements arranged in a line, and the pattern image is read two-dimensionally. The patch positioned on the outer periphery of the pattern image is greatly affected by flare, and there is a problem that the value of the read data deviates from the true value. There are various causes of flare, but one reason is that the reflected light around the patch becomes stray light. The influence of such flare appears more prominently in a sensor using a highly directional LED.

  For example, Patent Document 1 discloses an image forming apparatus that forms a pattern image including a plurality of patches having different gradations. According to this image forming apparatus, it is disclosed that a pattern image is formed on a sheet and a background pattern is formed on the outer periphery of the pattern image. The background pattern is formed with uniform gradation, and the gradation is 8% when the maximum value of the gradation of the pattern image is 100%. Thereby, the influence of flare can be suppressed.

JP 2010-85744 A

  By the way, the influence of flare is considered to have a large correlation with the gradation of the patch. Therefore, when uniform gradation is used for the background pattern, there is a problem in that the influence of flare cannot be sufficiently suppressed for patches of various gradations positioned on the outer periphery.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an image forming apparatus capable of forming a pattern image for calibration capable of suppressing the influence of flare.

  In order to solve this problem, the first invention includes an image forming unit that forms an image on a sheet, and a control unit that controls the image forming unit to form a pattern image for calibration on the sheet. An image forming apparatus is provided. Here, the pattern image is configured by arranging a plurality of patches having different gradations so as to be adjacent to each other, and the plurality of patches includes a first effective area for acquiring read data for calibration. Each area part is provided. In this case, at least one of the patches positioned on the outer periphery of the pattern image further includes a second area portion that is widened outwardly with the same gradation as the gradation of the first area portion.

  Here, in the first invention, it is preferable that the second region portion is set to a size that is n times (n is an integer of 1 or more) times the first region portion.

  In the first invention, the control unit patterns a plurality of matrix-like patch groups of l (l is an integer of 1 or more) × m (m is an integer of 1 or more) adjacent to each other in one sheet. An image is formed. In this case, in each of the patch groups, each of the patches positioned on the outer periphery of the patch group preferably includes the second region portion.

  According to a second aspect of the invention, an image forming unit that forms an image on a sheet, a reading unit that optically reads a sheet on which a pattern image in which a plurality of patches having different gradations are arranged adjacent to each other is formed, There is provided an image forming apparatus including a control unit that specifies positions of a plurality of patches in a read image obtained by reading a pattern image by a reading unit and performs calibration based on each read data related to the plurality of patches. Here, each of the plurality of patches includes a first area portion having a predetermined size, and at least one of the patches positioned on the outer periphery of the pattern image has the same gradation as the gradation of the first area portion. And a second region widened outwardly. In this case, the control unit does not use the read data in the second region for calibration.

  In the second invention, it is preferable that the control unit calibrates using read data in an effective area set in the first area.

  According to the present invention, for the outer peripheral patch in which the influence of flare becomes significant, the second region portion having the same gradation is set outside the first region portion including the effective region inside. Yes. The existence of the second region portion allows the effective region to be separated from the outer edge of the patch, so that flare affecting the effective region can be suppressed. In addition, since the second area portion is set to the same gradation as the first area portion, the second area portion does not cause the flare of the effective area itself, thereby suppressing the influence of flare. can do.

Explanatory drawing which shows typically the structure of the image forming apparatus which concerns on this embodiment. Block diagram showing the configuration of the main unit Explanatory drawing which shows the structure of a reading part typically Explanatory drawing which shows an example of the pattern image formed on paper Explanatory diagram conceptually showing the mode of each patch Flow chart showing the calibration execution procedure Explanatory drawing of the outer periphery patch provided with the 2nd area | region part of the same magnitude | size of the 1st area | region part Explanatory drawing showing a pattern image comprising a plurality of l × m patch groups

  FIG. 1 is a block diagram schematically illustrating the configuration of an image forming apparatus G according to the present embodiment. The image forming apparatus G includes a print controller g1, a paper feed unit g2, a main body unit g3, and a post-processing device g4.

  The print controller g1 receives PDL (Page Description Language) data from a computer terminal on the network, and rasterizes the PDL data to generate bitmap format image data. The print controller g1 generates image data for each color of C (cyan), M (magenta), Y (yellow), and K (black), and outputs the image data to the main unit g3.

  The sheet feeding unit g2 includes a plurality of large capacity sheet feeding trays. The paper feeding unit g2 conveys paper from the paper feeding tray designated by the main body unit g3 to the main body unit g3.

  The main body unit g3 forms an image on a sheet by the image forming unit 8 based on the image data obtained by reading the document D or the image data generated by the print controller g1. The main unit g3 conveys the sheet on which the image has been formed to the post-processing device g4.

  The post-processing device g4 performs post-processing on the paper conveyed from the main body unit g3 and discharges it. Examples of post-processing include stapling, punching, folding, and bookbinding. Post-processing is not essential, and the post-processing device g4 executes only when instructed by the main unit g3. When there is no post-processing, the post-processing device g4 discharges the conveyed paper as it is.

  FIG. 2 is a block diagram showing the configuration of the main unit g3. The main body unit g3 includes a control unit 1, a storage unit 2, an operation unit 3, a display unit 4, a communication unit 5, an automatic document conveyance unit 61, a scanner unit 6, an image processing device 7, an image forming unit 8, and a reading unit 9. Configured.

  The control unit 1 includes a CPU, a RAM, and the like. The control unit 1 reads a program stored in the storage unit 2 and controls each unit of the image forming apparatus G according to the program.

  For example, the control unit 1 feeds paper by the paper feed unit g2 or the paper feed tray g31 in accordance with job settings. Further, the control unit 1 corrects and processes the image data by the image processing device 7 and causes the image forming unit 8 to form an image on a sheet based on the image data. When the job setting includes post-processing settings, the control unit 1 instructs the post-processing device g4 to perform post-processing.

  The storage unit 2 stores programs, files, and the like that can be read by the control unit 1. As the storage unit 2, for example, a storage medium such as a hard disk or a ROM (Read Only Memory) can be used. Further, the storage unit 2 stores pattern image data for calibration.

  The operation unit 3 includes operation keys, a touch panel configured integrally with the display unit 4, and the like, and outputs operation signals corresponding to these operations to the control unit 1. The user can input an instruction to set a job, change processing contents, or the like through the operation unit 3.

  The display unit 4 displays information such as an operation screen in accordance with an instruction from the control unit 1 and is composed of an LCD (Liquid Crystal Display) or the like.

  The communication unit 5 communicates with a computer on the network, for example, a server or another image forming apparatus, according to an instruction from the control unit 1.

  The automatic document feeder 61 includes a placement tray for placing the document D, a transport roller for transporting the document D, and the like, and transports the document D to a predetermined transport path.

  The scanner unit 6 includes an optical system such as a light source and a reflecting mirror. The scanner unit 6 reads an image of the document D transported by the automatic document transport unit 61 or the document D placed on the platen glass, and determines each color of R (red), G (green), and B (blue). Generate image data. The generated image data is output to the image processing device 7.

  The image processing device 7 corrects the image data input from the scanner unit 6 or the print controller g 1, performs image processing, and outputs the image data to the image forming unit 8. The image processing apparatus 7 includes a color conversion unit 71, a gradation correction unit 72, and a halftone processing unit 73.

  The color conversion unit 71 performs color conversion processing on the R, G, and B color image data output from the scanner unit 6 and outputs C, M, Y, and K color image data. The color conversion unit 71 performs color conversion processing on the C, M, Y, and K color image data output from the print controller g1 for color correction, and performs color correction on the C, M, Y, and K colors. Image data can also be output. At the time of color conversion processing, the color conversion unit 71 uses an LUT in which gradation values of C, M, Y, and K colors after color conversion are determined for gradation values of R, G, and B colors. . At the time of color correction, the color conversion unit 71 uses an LUT in which C, M, Y, and K gradation values after color correction are determined for the gradation values of C, M, Y, and K colors.

  The gradation correction unit 72 corrects the gradation of the image data output from the color conversion unit 71 or the print controller g1. The gradation correction unit 72 performs a gradation correction LUT (γ) in which a correction value corresponding to each gradation value is determined so that the gradation characteristic of the image matches the target gradation characteristic at the time of gradation correction. Correction curve). The gradation correction unit 72 obtains a correction value corresponding to the gradation value of each pixel of the image data from the gradation correction LUT, and outputs the image data updated with the correction value.

  The halftone processing unit 73 performs halftone processing on the image data output from the gradation correction unit 72. The halftone processing is, for example, screen processing using a dither matrix, error diffusion processing, or the like. The halftone processing unit 73 outputs the image data after the halftone processing to the image forming unit 8.

  The image forming unit 8 forms an image on a sheet based on the image data output from the image processing device 7. As shown in FIG. 1, the image forming unit 8 includes an exposure unit 81, a photoreceptor 82, and a development unit 83 for each of C, M, Y, and K colors. The image forming unit 8 includes an intermediate transfer belt 84, a secondary transfer roller 85, a fixing device 86, and a reversing mechanism 87.

  The exposure unit 81 includes an LD (Laser Diode) as a light emitting element. The exposure unit 81 drives the LD based on the image data, and exposes the photosensitive member 82 to be charged by irradiating it with laser light. The developing unit 83 supplies toner onto the photoconductor 82 by a developing roller that is charged, and develops the electrostatic latent image formed on the photoconductor 82 by exposure.

  Each image (toner image) formed on the four photoconductors 82 is sequentially transferred from each photoconductor 82 to the intermediate transfer belt 84. As a result, a color image is formed on the intermediate transfer belt 84. The intermediate transfer belt 84 is an endless belt wound around a plurality of rollers, and rotates according to the rotation of each roller.

  The secondary transfer roller 85 transfers the color image on the intermediate transfer belt 84 onto the paper fed from the paper feed unit g2 or the paper feed tray g31.

  The fixing device 86 performs a fixing process for fixing the image on the paper by heating and pressurizing the paper after the transfer.

  When forming images on both sides of the paper, the image forming unit 8 reverses the front and back of the paper with the reversing mechanism 87 and forms an image on the other side. The reversing mechanism 87 has a transport path for reversing the front and back of the passing paper and transporting the paper again to the transfer position by the secondary transfer roller 85.

  FIG. 3 is an explanatory diagram schematically showing the configuration of the reading unit 9. The reading unit 9 reads an image formed on the sheet conveyed from the upstream conveyance path R1 on the upstream side in the conveyance direction. The sheet on which the image is read by the reading unit 9 is transported from the downstream transport path R2 on the downstream side in the transport direction to the post-processing device g4. While the image is read by the reading unit 9, the paper passes the reading position L at a predetermined speed by a plurality of conveying rollers (upstream conveying roller 88a, downstream conveying roller 88b, etc.) provided on the conveying path. Thus, the sheet is conveyed.

  The reading unit 9 mainly includes a CCD (Charge Coupled Device) 91, an optical system 92, and an LED (Light Emitting Diode) light source 93 that illuminates the reading position L.

  The CCD 91 is an optical sensor that reads an image on a sheet at a reading position L, and is a color line sensor that can read a full width range in the sheet width direction.

  The optical system 92 is for guiding the image at the reading position L to the CCD 91, and includes a plurality of mirrors and a plurality of lenses.

  With this configuration, the reading unit 9 sequentially reads an image formed on the sheet over the entire width of the sheet that passes the reading position L, and thereby a two-dimensional image corresponding to the sheet (hereinafter referred to as “read image”). Is generated.

  A calibration unit 94 is provided below the conveyance path R3 of the reading unit 9. The calibration unit 94 includes a white reference plate for determining a correction value for shading correction performed when reading an image. The white reference plate is provided at the reading position L, and reading is performed by the CCD 91 with a gap when the sheet is not passing (for example, between sheets).

  The upstream conveyance path R1, the conveyance path R3 of the reading unit 9, and the downstream conveyance path R2 are provided to have different conveyance angles. Specifically, the upstream transport path R1 is provided to be inclined downward with respect to the transport direction so that a downward pressing force can be applied to the paper transported to the transport path R3 of the reading unit 9. It has become. The conveyance path R3 of the reading unit 9 is provided in the horizontal direction. The downstream transport path R2 is provided to be inclined upward with respect to the transport direction so that an upward pressing force can be applied to the paper transported from the transport path R3 of the reading unit 9.

  In the image forming apparatus G having such a configuration, the control unit 1 performs calibration for adjusting the characteristics of the image forming apparatus G. Specifically, the control unit 1 forms a pattern image for calibration on a sheet, and calculates a γ correction curve from the read image corresponding to the pattern image output from the reading unit 9. The control unit 1 creates an LUT for the calculated γ correction curve and updates the tone correction LUT in the tone correction unit 72 to the created LUT. The storage unit 2 stores data for generating a pattern image for calibration.

  Here, FIG. 4 is an explanatory diagram showing an example of the pattern image 100 formed on the paper. The pattern image 100 is configured by arranging a plurality of patches P having different gradations so as to be adjacent to each other, and the plurality of patches P are prepared for each of C, M, Y, and K colors. In the figure, the dots drawn on each patch P indicate the level of gradation, and in the actual patch P, the area is uniformly drawn with the same gradation. Also, in the figure, the symbols “(C)”, “(M)”, “(Y)”, and “(K)” indicate the color of each patch P, and are shown in the actual pattern image 100. There is no need to be drawn. Further, the solid line drawn so as to divide each patch P is for indicating the outer edge of the patch P, and in the actual patch P, it is not necessary to draw a frame-like line that borders the outer edge.

  In the example shown in the figure, the patches P of each gradation corresponding to K are arranged along the longitudinal direction of the paper and are positioned in the leftmost column in the figure. The patches P of each gradation corresponding to C are arranged along the longitudinal direction of the paper and are positioned in the second column from the left in the drawing. Further, the patches P of each gradation corresponding to M are arranged along the longitudinal direction of the sheet, and are positioned in the third column from the left in the drawing. The patches P of each gradation corresponding to Y are arranged along the longitudinal direction of the paper, and are positioned in the rightmost column in the drawing. In each color, each patch P is set so that the density decreases from the upper side to the lower side, and in this embodiment, five levels of density are reproduced.

  As described above, the plurality of patches P constituting the pattern image 100 are different from each other in terms of color and density. In the present embodiment, in addition to such a difference in the mode, a patch P (hereinafter referred to as “outer peripheral patch P”) positioned on the outer periphery of the pattern image 100 and a patch P (hereinafter referred to as “inner peripheral patch P”) positioned inside thereof. The size is set differently. Specifically, the outer peripheral patch P is set to a size larger than the inner peripheral patch P. In the present embodiment, the outer peripheral patch P corresponds to five patches P corresponding to K, five patches P corresponding to Y, and the first and fifth four patches P from the top of C and M. On the other hand, the inner peripheral patch P corresponds to the second, third, and fourth six patches P from the top of C and M.

  FIG. 5 is an explanatory diagram conceptually showing an aspect of each patch P. In the figure, elements such as color and density are omitted. 4A shows a fourth patch P (PC4) from the top of C shown in FIG. 4 as an example of the inner peripheral patch P. FIG. The patch P (PC4) is formed from a first area RA having a quadrangular shape, and the read data for calibration (colorimetric values corresponding to pixels) are included in the first area RA. ) Is set.

  When calibration is performed, a read image is obtained by two-dimensionally reading the pattern image 100 through the reading unit 9. For each patch P, read data in the patch P is acquired from the read image, and a representative colorimetric value (patch data) associated with the patch is obtained. In order to obtain the patch data, not all the read data in the entire area of the patch P (first area RA) is used, but only the read data in the effective area RS is used. This is because, by using only the data in the effective area RS, the read data located at the boundary between the adjacent patches P is eliminated, so that the patch data is not easily affected by the adjacent patches P and the patch data is reliable. This is because it can be calculated.

  On the other hand, FIG. 4B shows the uppermost patch P (PK1) of the K color shown in FIG. Like the inner patch P, the patch P (PK1) includes the first area RA including the effective area RS, and has a constant width outward, that is, to the side where no other patch P is adjacent. The second region portion RB widened by (2) is further provided. Since the patch P (PK1) is located at the upper left, the second area RB is set to an area surrounding the left side and the upper side of the first area RA. The same gradation (same color and same density) as that of the first area RA is set in the second area RB.

  Further, FIG. 4C shows the M-colored top patch P (PM1) shown in FIG. The patch P (PM1) further includes a second region portion RB, like the above-described K-color patch P (PK1). Since the patch P (PM1) is sandwiched between C and Y and is located at the uppermost stage, the second region portion RB is set only on the upper side of the first region portion RA. ing. The same gradation (same color and same density) as that of the first area RA is set in the second area RB.

  Further, FIG. 10C shows the fourth patch P (PY4) from the top of the Y color shown in FIG. The patch P (PY4) further includes a second region portion RB, like the above-described patch P (PK1, PM1). Since the patch P (PY4) is located on the rightmost side and is sandwiched between patches P of the same color and different gradations, the second region portion RB is only on the right side of the first region portion RA. Is set to The same gradation (same color and same density) as that of the first area RA is set in the second area RB.

  As shown in FIG. 4, in addition to these outer peripheral patches P, other outer peripheral patches P are widened outward together with the first region RA with the same gradation as the first region RA. The second region portion RB is provided.

  In FIG. 4, four reference marks 101 formed at the four corners of the sheet are for specifying the position of each patch P from the read image of the pattern image 100.

  Hereinafter, a calibration method using such a pattern image 100 will be described. Here, FIG. 6 is a flowchart showing a calibration execution procedure. The process shown in this flowchart is executed by the control unit 1 of the main body unit g3.

  First, in step 1 (S1), the control unit 1 generates a pattern image 100. As described above, the pattern image 100 generated in step 1 is generated so that the size of the outer peripheral patch P is larger than the size of the inner peripheral patch P.

  In step 2 (S2), the control unit 1 controls the image forming unit 8 based on the generated pattern image 100 to print the pattern image 100 on a sheet.

  In step 3 (S3), the control unit 1 performs a reading operation. Specifically, the control unit 1 operates the reading unit 9 in synchronization with the timing when the paper on which the pattern image 100 is formed passes through the reading unit 9, and the pattern image 100 formed on the paper by the reading unit 9. Read. The reading unit 9 generates a read image by reading the pattern image 100, and the generated read image is output to the control unit 1.

  In step 4 (S4), the control unit 1 acquires patch data relating to each patch based on the read image. Specifically, the control unit 1 acquires the patch data by using the read data (colorimetric values) in the effective area RS of each patch P and averaging the read data. Here, as a method for specifying the position of each patch P (effective region RS) on the read image, a method such as projective transformation can be used. Specifically, the control unit 1 is based on the design coordinates of the four reference marks 101, the design coordinates of the effective area RS of each patch P, and the actual coordinates of the reference marks 101 in the read image obtained by reading the pattern image 100. The effective area RS of each patch P on the read image is specified.

  In step 5 (S5), the control unit 1 converts the patch data relating to each patch P into a color value (for example, reflectance). In this conversion process, a one-dimensional LUT indicating the correspondence between the patch data (colorimetric values) of the pattern image 100 and the color values is used. The one-dimensional LUT is preferably prepared in advance.

  In step 6 (S6), the control unit 1 calculates a γ correction curve based on the color value obtained for each patch P. When the γ correction curve is calculated, the control unit 1 creates an LUT for the γ correction curve, and updates the tone correction LUT in the tone correction unit 72 with the created LUT. Calibration is completed by such a series of processes.

  As described above, in the present embodiment, the image forming apparatus G includes the image forming unit 8 that forms an image on a sheet, and the control unit 1 that controls the image forming unit 8 to form a calibration pattern image 100 on a sheet. ,have. Here, the pattern image 100 is configured by arranging a plurality of patches P having different gradations so as to be adjacent to each other, and the plurality of patches P includes an effective region RS for acquiring read data for calibration. The first region RA included in each is provided. Each patch (outer peripheral patch) P positioned on the outer periphery of the pattern image 100 further includes a second region portion RB widened outwardly with the same gradation as that of the first region portion RA. Yes.

  According to this configuration, for the outer peripheral patch P in which the influence of flare becomes significant, the second region portion RB having the same gradation as the outer region of the first region RA including the effective region RS. Is set. Since the effective region RS is separated from the periphery of the patch P by the presence of the second region portion RB, flare that affects the effective region RS can be suppressed. In the present embodiment, since the second region portion RB is set to the same gradation as the first region portion RA, the second region portion RB does not become a flare factor of the effective region RS. Therefore, the influence of flare on the effective area RS can be suppressed. For this reason, the influence of the flare on the patch data can be suppressed.

  From the viewpoint of suppressing flare, it is preferable to increase the size of the entire area of the patch P compared to the effective area RS. However, in such a form, the number of patches P that can be formed per sheet decreases, and when performing calibration, the pattern image 100 must be formed in a distributed manner on a large number of sheets. . In this regard, in the present embodiment, by arranging the second region portion RB in the outer peripheral patch P where the influence of flare is large, both the suppression of flare and the number of patches that can be formed per sheet are achieved. It can be planned.

  The image forming apparatus G of the present embodiment optically prints a sheet on which an image forming unit 8 that forms an image on a sheet and a pattern image 100 in which a plurality of patches P having different gradations are arranged adjacent to each other are formed. Reading unit 9 and control for specifying the positions of the plurality of patches P in the read image obtained by reading the pattern image 100 by the reading unit 9 and performing calibration based on the read data relating to the plurality of patches P Part 1. Here, each of the plurality of patches P includes a first region RA of a predetermined size, and each patch (outer periphery patch) P positioned on the outer periphery of the pattern image has the gradation of the first region RA. A second region RB that is widened outward at the same gradation is further provided. In this case, the control unit 1 does not use the read data in the second region RB in the calibration.

  According to this configuration, for the outer peripheral patch P in which the influence of flare becomes significant, the second region portion RB having the same gradation as this is set outside the first region portion RA. For this reason, by not using the read data in the second region portion RB in the calibration, the read data affected by the flare can be eliminated and the patch data can be obtained. Thereby, the influence of flare on the patch data can be suppressed.

  In the present embodiment, the control unit 1 performs calibration using the read data in the effective area RS set inside the first area RA.

  According to this configuration, the presence of the second region portion RB outside the first region portion RA including the effective region RS suppresses the influence of flare from the peripheral portion of the pattern image 100 to the effective region RS. can do. In the present embodiment, since the second region portion RB is set to the same gradation as the first region portion RA, the influence of flare is also suppressed for the patches P of various gradations located on the outer periphery. can do. For this reason, the influence of the flare on the patch data can be suppressed.

  In the outer peripheral patch P, the size of the second region RB set outside the first region RA can be arbitrarily set. For example, n (n) of the first region RA Can be set to an integer of 1 or more times. The value of n can be determined according to the degree of flare. For example, the value of n can be increased as the flare increases. Here, FIG. 7 is an explanatory diagram of the outer peripheral patch P including the second region portion RB having the same size (1 ×) as the first region portion RA, and is about twice that of the normal patch P. By securing the size of the flare, the influence of flare can be suppressed. Also, by making n an integral multiple, the second region RB can be formed simply by repeatedly arranging patches of the same size as the normal patch P (inner peripheral patch) on the outside, so software processing is shared can do.

  Further, when forming a pattern image, there is a demand to form as many patches P as possible on one sheet. Therefore, as another example of the pattern image, one in which a plurality of matrix-like patch groups of l (l is an integer of 1 or more) × m (m is an integer of 1 or more) are adjacent to each other in one sheet of paper is conceivable. . FIG. 8 is an explanatory diagram showing a pattern image 102 including two patch groups 100a and 100b. Each patch group 100a and 100b is configured in a 4 × 5 matrix. In the case of such a pattern image 102, in each of the patch groups 100a and 100b in units of l × m, each of the patches P positioned on the outer periphery of the patch group 100a and 100b includes a second region portion. It is preferable.

  The image forming apparatus according to the embodiment of the present invention has been described above, but the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the invention. .

  For example, in the present embodiment, all the outer peripheral patches include the second region portion, but at least one patch among the patches positioned on the outer periphery of the pattern image is the second region from the viewpoint of the influence of flare. A part may be provided.

  In the present embodiment, the one-dimensional calibration is exemplified, but the present invention can also be applied to multi-order color calibration.

G Image forming apparatus
g1 Print controller
g2 Paper feed unit
g3 Main unit
g4 Aftertreatment device
1 Control unit
2 storage unit
3 Operation part
4 display section
5 Communication Department
6 Scanner section
7 Image processing device
8 Image forming part
9 Reading unit

Claims (5)

An image forming unit for forming an image on paper;
A control unit that controls the image forming unit to form a pattern image for calibration on a sheet,
The pattern image is configured by arranging a plurality of patches with different gradations so as to be adjacent to each other,
Each of the plurality of patches includes a first area portion that includes an effective area for acquiring the calibration read data.
At least one patch among the patches positioned on the outer periphery of the pattern image further includes a second region that is widened outwardly with the same gradation as the gradation of the first region. Image forming apparatus.   2. The image forming apparatus according to claim 1, wherein the second area portion is set to have a size n (n is an integer equal to or greater than 1) times as large as the first area portion. The control unit forms the pattern image by adjoining a plurality of patch groups in a matrix of l (l is an integer of 1 or more) × m (m is an integer of 1 or more) in one sheet. ,
3. The image forming apparatus according to claim 1, wherein in each of the patch groups, each of the patches positioned on an outer periphery of the patch group includes the second region portion. An image forming unit for forming an image on paper;
A reading unit that optically reads a sheet on which a pattern image in which a plurality of patches having different gradations are arranged adjacent to each other is formed;
A control unit that specifies the positions of the plurality of patches in the read image obtained by reading the pattern image by the reading unit, and performs calibration based on the read data related to the plurality of patches,
Each of the plurality of patches includes a first area portion having a predetermined size,
At least one patch among the patches positioned on the outer periphery of the pattern image further includes a second region that is widened outwardly with the same gradation as the gradation of the first region.
The image forming apparatus, wherein the control unit does not use the read data in the second area in the calibration.   The image forming apparatus according to claim 4, wherein the control unit performs the calibration by using read data in an effective area set inside the first area unit.

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