JP2009010705A - Device and method for forming image, and color chart - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an image-forming device enabling image density adjustment, where the influence of density unevenness in images cannot be reflected easily even if the density unevenness in images occurs in the conveyance direction of paper sheets or a direction orthogonally crossing the conveyance direction. <P>SOLUTION: In the image-forming device, a patch image for density adjustment, where at least either of density information and color information is common, is arranged in a position relationship, where coordinates of the conveyance direction (x) of paper sheets differ from those of an orthogonal direction (y) orthogonally crossing the conveyance direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to an image forming apparatus that outputs a plurality of density adjustment patch images having different color information and density information on a sheet, and an image forming method thereof.

  In recent years, an electrophotographic image forming apparatus has been used in the field of light printing such as POD (print on demand). In addition, an image forming apparatus using an inkjet method or a silver salt photosensitive material together with an electrophotographic image forming apparatus is used as an image output apparatus for trial printing at the time of proofreading the printing process. High quality is required.

  In these image forming apparatuses, an image on a sheet changes when a characteristic change such as a developer or a sheet having a different characteristic is used depending on a change with time, an environmental change, or a use situation. An image forming apparatus having a density adjusting function is known in order to output a constant image even in these characteristic changes.

In Patent Document 1, as such a density adjustment function, color patch groups are arranged and output on a sheet, and an output image is read by a scanner unit, thereby reducing errors due to density unevenness and performing high-precision calibration. A color image recording apparatus is disclosed.
JP 2001-88357 A

  When paper conveyance becomes unstable during image output and reading, horizontal stripe-like image density unevenness extending in a direction orthogonal to the paper conveyance direction results. Also, if there is a stain such as a stain on the scanner optical system or a part of the rotating body that rotates in the paper transport direction, such as a stain or a scratch, the vertical stripe-shaped image density unevenness extending in the paper transport direction. It becomes.

  In the color image recording apparatus disclosed in Patent Document 1, density patches of the same color with different gradations and color patch groups composed of density patches of the same density are arranged in a vertical or horizontal row for density adjustment. Has been.

  When the color patch group for density adjustment is arranged in this way, as described above, when image density unevenness occurs in the paper transport direction or in a direction perpendicular to the transport direction, the influence of the density unevenness affects a specific color. Or it will concentrate on a patch of a specific density. When the image density adjustment is performed in a state where such density unevenness occurs, the influence is reflected as it is in the density control, and the density control cannot be performed properly.

  SUMMARY OF THE INVENTION In view of the above problems, the present invention provides an image forming apparatus capable of performing image density adjustment in which even if image density unevenness occurs in the paper conveyance direction or in a direction orthogonal to the conveyance direction, the influence is hardly reflected. It is intended to do.

  The above object is achieved by the invention described below.

(1) arrangement determining means for determining the arrangement of a patch image for density adjustment;
An image forming unit that forms a patch image on a sheet based on the arrangement determined by the arrangement determining unit;
An image forming apparatus comprising: a density control unit that controls a density characteristic of the image forming unit based on a result of reading an image density of a patch image formed on a sheet.
The arrangement determining unit arranges patch images having at least one of density information and color information in a positional relationship in which the coordinates in the paper transport direction x and the coordinates in the orthogonal direction y orthogonal to the transport direction are different from each other. An image forming apparatus.

(2) The image forming apparatus includes a reading unit that reads a sheet,
The image forming apparatus according to (1), wherein the density control unit controls a density characteristic of the image forming unit based on a reading result of an image density of a patch image on a sheet read by the reading unit. .

  (3) The image forming apparatus according to (1) or (2), wherein the arrangement determining unit arranges the density adjustment patch images randomly based on random numbers.

(4) The arrangement determining means assigns a predetermined order to the patch image to be arranged based on the density information and the color information, and assigns the k−1th patch image to the coordinates p (x _k−1 , y _k on the paper. _-1 ), the following k-th patch image is arranged at the coordinates p (x _k , y _k ), and satisfies the following relational expression (1) or (2) Image forming apparatus.
x _k = (x _k-1 + C _i ) mod i
y _k = (y _k−1 + C _j ) mod j
Where i is the number of patch images that can be arranged in the transport direction x, j is the number of patch images that can be arranged in the orthogonal direction y, C _i is the smallest integer less than or equal to 2 and less than i that does not have a prime factor of i, and C _j Is a minimum integer less than or equal to 2 and less than j that does not have a prime factor of j. (5) An arrangement determining step for determining the arrangement of patch images for density adjustment;
An image forming process for forming a patch image on paper based on the layout determined in the layout determination process;
A density control step of controlling density characteristics of the image forming unit based on a measurement result of an image density of a patch image formed on a sheet, and an image forming method of an image forming apparatus comprising:
In the arrangement determining step, the patch images having at least one of density information and color information are arranged in a positional relationship in which the coordinates in the paper transport direction x and the coordinates in the orthogonal direction y orthogonal to the transport direction are different from each other. An image forming method for an image forming apparatus.

(6) The image forming apparatus includes a reading unit that reads a sheet,
The image forming apparatus according to (5), wherein in the density control step, density characteristics of the image forming unit are controlled based on a reading result of an image density of a patch image on a sheet read by the reading unit. Image forming method.

  (7) The image forming method for an image forming apparatus according to (5) or (6), wherein in the arrangement determining step, the density adjustment patch images are randomly arranged based on random numbers.

(8) In the arrangement determining process, the patch image density information to be placed, based on the color information assigned to a predetermined order, the coordinates p (x on the paper the k-1 th patch image _k-1, y _{k -1} ), the following k-th patch image is arranged at the coordinates p (x _k , y _k ), and satisfies the following relational expression (5) or (6) An image forming method of an image forming apparatus.
x _k = (x _k-1 + C _i ) mod i
y _k = (y _k−1 + C _j ) mod j
Where i is the number of patch images that can be arranged in the transport direction x, j is the number of patch images that can be arranged in the orthogonal direction y, C _i is the smallest integer less than or equal to 2 and less than i that does not have a prime factor of i, and C _j Is a minimum integer less than 2 and less than j that does not have a prime factor of j. (9) A color chart in which patch images for density adjustment are arranged.
A color chart in which patch images having at least one of density information and color information are arranged in a positional relationship in which the coordinate in the horizontal direction x of the paper and the coordinate in the vertical direction y of the paper are different from each other.

  According to the present invention, it is possible to obtain an image forming apparatus capable of performing image density adjustment in which even if image density unevenness occurs in the paper conveyance direction or in a direction orthogonal to the conveyance direction, the influence is hardly reflected. it can.

  Although the present invention will be described based on an embodiment, the present invention is not limited to the embodiment.

  FIG. 1 is a central cross-sectional view of the image forming apparatus according to the present embodiment. The image forming apparatus A is called a tandem type color copying apparatus, and includes an image forming unit A4, a document reading unit 1, an operation display unit 2, and an automatic document feeder D.

  The image forming unit A4 includes an image writing unit 40, a plurality of sets of image creating units 4Y (yellow), 4M (magenta), 4C (cyan), 4Bk (black), a belt-like intermediate transfer member 42, and a paper feed cassette 5. A sheet feeding unit 6, a sheet discharge unit 7, an automatic double-sided copy sheet feeding unit 9, and a fixing device 10.

  The image creating unit (4Y, 4M, 4C, 4Bk) has a developing unit, and each has a small particle size toner of each color of yellow (Y), magenta (M), cyan (C), and black (Bk). Includes a two-component developer made of a carrier.

  An automatic document feeder D is mounted on the upper part of the image forming apparatus A. The document placed on the document table of the automatic document feeder D is conveyed in the direction of the arrow. The document image irradiated with the lamp 1B is scanned on one or both sides of the document by the optical system, and the image of the CCD is read. It is read by the sensor 1A.

  The analog signal photoelectrically converted by the image sensor 1A is subjected to analog processing, A / D conversion, shading correction, image compression processing, and the like in the control unit A1, which will be described later, and then stored in the storage unit as image data. Alternatively, a signal is sent to the image writing unit 40.

  In the image writing unit 40, the output light from the semiconductor laser is irradiated onto the photosensitive drum 41 (reference numerals are omitted for M, C, and Bk) to form a latent image. In the image forming unit A4, processes such as charging, exposure, development, transfer, separation, and cleaning are performed. The toner images of the respective colors formed by the image creating unit 4 are sequentially transferred by the primary transfer unit onto the rotating intermediate transfer body 42 to form a combined color image. The output light of the semiconductor laser of the image writing unit 40 can be corrected by a signal from the control unit A1 described later.

  The toner image on the intermediate transfer body 42 is transferred by the transfer means 43 from the paper feed cassette 5 to the paper S conveyed by the paper feed means 6. The sheet S carrying the toner image is fixed by the fixing device 10, discharged out of the apparatus from the sheet discharge port 71 of the sheet discharge unit 7, and placed on the sheet discharge tray 8. Alternatively, the single-sided image-processed paper S sent to the double-sided conveyance path 9 by a conveyance path switching gate (not shown) is again discharged from the paper discharge port 71 of the paper discharge unit 7 after double-sided image processing in the image forming unit A4. It is placed on a paper plate 8.

  FIG. 2 is a control block diagram of the image forming apparatus. In the figure, parts necessary for explaining the operation of the present embodiment are mainly described, and other parts known as image forming apparatuses are omitted. Further, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

  A1 is a control unit comprising a CPU (A11), a system memory A12, and a density control unit A13. The CPU (A11) executes various controls by executing various programs stored in the system memory A12. The image output on the sheet by the image forming unit A4 is read by an external scanner or the document reading unit 1 of the image forming apparatus A. Based on the read result of the image, the density control unit controls the density characteristics of the C, M, Y, and Bk colors of the image forming unit A4 so that the density and γ curve of each color become preset target values. . In this embodiment, the density characteristic is controlled by controlling the output light of the writing unit 40 to change the halftone dot size of the toner image formed by toner or the interval between the halftone dots. Is changed so that the image density with respect to the density information falls within a predetermined range.

  In the present embodiment, the control unit A1 functions as an “arrangement determining unit” that determines the arrangement of the density adjustment patch image and a “density control unit” that controls the density characteristics of the image forming unit. The “color information” is, for example, information related to C, M, Y, and Bk output, and the “density information” is any gradation of each color (for example, 200 out of 256 gradation numbers of 8 bits). Information indicating whether to output in (gradation).

  A2 is an HDD (Hard Disk Drive) memory, which stores image data read from the document reading unit 1, arrangement information determined by the arrangement determining means, and the like.

  A3 is a communication unit which is connected to an external network and can be connected to an external scanner or the like. In the image forming apparatus A, the density of the image forming hand A4 is controlled by reading the image density of the patch image formed on the paper formed by the image forming hand 4 with an external scanner and acquiring information of the read result. It is possible.

  The operation display unit 2 includes a touch panel in which a touch screen is arranged on a display unit configured by a liquid crystal panel. The user can input various settings by operating the operation display unit 2 or a keyboard and mouse (not shown).

[Condition settings as preparation before arranging patch images]
FIG. 3 is a diagram illustrating a control flow of the image forming apparatus according to the embodiment. Before arranging the patch image, various conditions are set as advance preparations. First, in step S11, an arrangement area in which a patch image is arranged is defined. The arrangement area can be determined by setting conditions such as the size of the image area of the paper, the size of the patch image, the interval between the patch images, and the number of patch arrangements. Next, setting of each condition will be described with reference to a detailed view of the display screen.

  FIG. 4 is a detailed view of a display screen in the operation display unit 2. In FIG. 4, the condition of the arrangement area where the patch image is arranged is selected. By setting the image area of the paper in the D1 column, the size of one patch image in the D2 column, the number of patch images that can be arranged, and the condition of the arrangement reference position in the D3 column, the arrangement area in which the patch image is arranged is set. Can be set. For example, in the D3 column, the number of patch images that can be placed in the placement area is set by operating the triangle buttons that can be placed (D15). In this selection, if a condition that causes inconsistency between the setting conditions, for example, if the total area of the patch image exceeds the area of the image area of the paper, error processing is performed by the control unit A1. Prompt the user to re-enter. After the selection of the condition is completed, it is confirmed by pressing the decision button D4.

  FIG. 5 is a diagram illustrating an arrangement region. In the figure, based on the setting example shown in FIG. 4, four (i) in the conveyance direction x (hereinafter also simply referred to as “x direction”) and an orthogonal direction y orthogonal to the conveyance direction x in the image area of the paper. A state in which eight (j) empty arrays in which patch images can be arranged and coordinates p (0, 0) to p (3, 7) are provided (hereinafter simply referred to as an orthogonal direction y or y direction). (Hereinafter also referred to as sequence p). Note that i is the number of patch images that can be arranged in the conveyance direction x, and j is the number of patch images that can be arranged in the orthogonal direction y.

  Subsequently, in step S12 in FIG. 3, the conditions of the patch image to be arranged are set. This setting is input on the display screen of the operation display unit 2 shown in FIG. The D5 column in the figure is a column for setting conditions for the patch image to be arranged. By setting the number of colors L (D21), the number of gradations M (D22), and the number of repetitions N (D24), the number of patch images to be arranged is determined. In addition, in the color number L (D21), the color type can be set together with the number of colors. The color types are Y (yellow), M (magenta), C (cyan), and Bk (black). The output of each gradation can be set by gradation allocation (D23), and the example shown in the figure is a setting for equally allocating 4 gradations. For example, if the 8-bit gradation of 0 to 255 is used, It shows that four gradations 63, 127, 191, and 255 are output.

  In this embodiment, an example of an image forming apparatus using four color toners is shown. However, the present invention is not limited to this, and an ink jet method or the like adds C and M colors in addition to the above four colors. An image forming apparatus that outputs a color image with colored ink may be used. Also, an image forming apparatus that outputs a color image by performing laser exposure corresponding to B, G, and R on the photosensitive material using a silver salt color photosensitive material may be used.

  Next, in step S13 of FIG. 3, setting of patch image arrangement conditions is performed. A column D6 in FIG. 6 is a column for setting the arrangement condition of the patch image. The prohibition condition (D31) is set as the arrangement condition. Forbidden condition (D31), by selecting any button B, any one of three types of combinations of “density information and color information”, “density information”, and “color information” can be selected.

  In step S14, it is determined whether the arrangement area and the number of arrangements are sufficiently secured. This determination is performed by the control unit A1 functioning as an arrangement determining unit, and it is determined whether or not the arrangement is possible under the conditions set in steps S11 to S13. Table 1 shows the size condition of the arrangement area necessary for the set prohibition condition.

  Whether or not the arrangement is possible is determined by whether the conditions (1) the number that can be arranged at the x-coordinate and the y-coordinate, and (2) the surface size of the arrangement area are met for the set prohibition condition. Judging. For example, in the case of density information (a2) as a prohibition condition, condition (1) number i of patch images that can be arranged at the x-coordinate and y-coordinate, j ≧ color information L × repetition N, and condition (2) arrangement area It is determined whether the surface size (i × j) of both satisfies the total number of patch images (L × M × N) or more.

  If it is determined that the condition is not satisfied (No in S14), the flow after Step S11 is repeated once more. If the condition is satisfied (Yes in S14), a subroutine process for determining the arrangement of the patch image is performed in the subsequent step S20 (arrangement determining step). This subroutine processing will be described later. Step S21 is a step of forming an image on a sheet by the image forming unit A4 based on the determined arrangement condition of the patch image. Note that the arrangement information (position, color information, density information) of the patch image determined in step S20 is stored in the HDD memory A2.

  In step S22, a sheet is set in the document reading unit 1, and a patch image formed on the sheet is read (scanned). Step S23 is a density control step in which the control unit A1 (density control unit A13) that functions as a density control unit based on the measurement result of the read patch image controls the density characteristics of the image forming unit A4. In the density control step, the image density is set to be within a predetermined range, and the process ends (END).

  The HDD memory A2 also stores management information such as numbers when storing the arrangement information. The management information is printed on the sheet together with the patch image for density adjustment. The management information printed on the paper can be read out from the operation display unit 2 by key input or automatic reading by OCR, etc., and the arrangement information of the patch image corresponding to the acquired management information can be read out. In the density control step (S23), density control is performed by comparing the stored arrangement information with the position, density information, and color information of the patch image read from the scanner.

  The above is the overall flow. Next, the subroutine processing in step S20 will be described.

[Subroutine processing to determine the arrangement of patch images]
FIG. 7 is a diagram showing a subroutine process (S20) for determining the arrangement. In the figure, the arrangement determining means determines the arrangement of the patch image based on the conditions set in the control flow of FIG. First, in step S201, a predetermined order is assigned to the patch images to be output based on the patch image output conditions set in step S12 (column D5 in FIG. 6).

  Table 2 gives a predetermined order to each patch image based on density information and color information when output conditions as shown in the D5 column of FIG. 6 are set. In the present embodiment, the predetermined order is assigned in order from the first to the k-th color information in the order of C, M, Y, and Bk, from the lightest to the darkest, and this is repeated. Repeat for minutes. In the example shown in the figure, the first array G (1) indicates that a patch image to be output under the condition of C (cyan) color and density 1 (for example, 63/256 gradations) is set. Yes. Note that the last order k is the total number of patch images to be arranged, and is the product of the number of colors L, the number of density gradations M, and the number of repetitions N.

In step S202, 1 is set to the order variable k as an initial setting. In step S210, candidates for coordinates pk (x _k , y _k ) for arranging the patch image are randomly determined using random numbers. The random number is generated by a random number generation function of the control unit A1. As a method for determining the coordinates pk (x _k , y _k ), an empty array (coordinates) in which the patch images are not yet arranged among the coordinates p (0, 0) to p (i−1, j−1) is used. A number is assigned to p), and a coordinate p assigned a number corresponding to the random number is extracted. As an example of the correspondence relationship, there is a method of extracting an array having a number that matches a remainder obtained by dividing an integerized random number by the total number of empty arrays.

In the next step S221, when the patch image G (k) is placed on the candidate for the coordinates pk (x _k , y _k ) determined in step S210, the setting is made in step S13 (column D6 in FIG. 6). It is determined whether or not the arrangement condition is satisfied. For example, if the prohibition condition is "density information and color information", the patch image density and color information of the patch image G (k) matches both the coordinates p (x _k of the x coordinate (x _k) match, 0) to p (x _k , j−1) or the coordinates of the coordinates p (0, y _k ) to p (i−1, y _k ) where the y coordinates (y _k ) match, Determine if you are satisfied or not. An example in which patch images are arranged based on the arrangement conditions will be described later.

If it does not satisfy the placement condition (No in S221), the coordinates pk (x _k, y _k) of the current candidate because it is impossible to place the G (k) to repeat the control of S210. At this time, in the control S210, the coordinates of the current candidate may be excluded from the candidate targets, and the coordinates p of other candidates may be determined. If there are no more candidate target coordinates, After returning to the previous order, G (k) may be re-arranged and arranged at another candidate coordinate p.

On the other hand, when the arrangement condition is satisfied (Yes in S221), the arrangement of the patch image G (k) at the coordinates pk (x _k , y _k ) is determined (step S222). If all the arrangements have not been completed (No in S223), the flow from step S210 is repeated until the arrangement is completed.

  By executing the control flow as described above, the arrangement determining unit executes a patch image in which at least one of density information or color information is common between all patch images, or coordinates of the conveyance direction x of the paper or the conveyance of the patch image. The coordinates in the orthogonal direction y orthogonal to the direction are arranged in different positional relations.

  8 and 9 show examples in which patch images are arranged by the arrangement determining means.

  FIG. 8 shows an example in which “patch images having common density information and color information” are arranged at “positions having different x and y coordinates”. In the example shown in the figure, the number of colors L is 2, the number of gradations M is 4, the number of repetitions N is 4, and the total number k is 32 (4 (i) × 8 (j) patch images). It is arranged in an area consisting of 32 arrays. The alphabetical characters shown in the figure indicate the type of color, and the numbers indicate the gradation (the same applies hereinafter). For example, four patch images (patch images indicated by thick frames) of Bk1 in which both density information and color information match are arranged so that the x coordinate and the y coordinate are different from each other.

  By arranging the patch images in such an arrangement, even if image density unevenness occurs in the paper conveyance direction or in the direction orthogonal to the conveyance direction, the density information and the color information coincide with each other in the specific patch image. It is possible to avoid concentration of influences. That is, it is possible to obtain an image forming apparatus capable of performing image density adjustment that is difficult to reflect the influence even when image density unevenness occurs.

  FIG. 9 is an example in which “patch images having common density information” are arranged at “positions where x and y coordinates are different”. In the example shown in the figure, the number of colors L is 4, the number of gradations M is 4, the number of repetitions N is 2, and a total number k of 32 patch images is 8 (i) × 8 (j). It is arranged in an area consisting of 64 arrays. For example, C1, M1, Y1, and Bk1 patch images having common density information (patch images indicated by thick frames) are arranged so that the x coordinate and y coordinate are different from each other.

  By arranging the patch images in such an arrangement, even if image density unevenness occurs in the paper conveyance direction or in a direction orthogonal to the conveyance direction, only the patch image of a specific gradation whose density information matches. It is possible to avoid the concentration of the influence.

  FIG. 10 is a diagram showing another subroutine process (S20) for determining the arrangement. This figure is a modification of the control flow of FIG. 7, and common processes are given the same reference numerals and explanations thereof are omitted. An example of arrangement by this subroutine processing will be described later with reference to FIG.

  In step S250, constants Ci and Cj are calculated. Ci is a minimum integer less than or equal to 2 and less than i that does not have a prime factor of i as a factor, and Cj is a minimum integer that is greater than or equal to 2 and less than j that does not have a factor of j as a factor. For example, if i is 9, Ci is 2, and if j is 10, Cj is 3.

In the subsequent step S251, 0 is assigned to x _k and y _k as an initial arrangement, and a patch image of G (1) is arranged at coordinates p (0, 0). If the arrangement is not completed, k is incremented (added by 1) (steps S223 and S224), and the next coordinates are calculated in step S252. The next x coordinate (x _k ) and y coordinate (y _k ) are calculated from the x coordinate (x _k-1 ) and y coordinate (y _k-1 ) of the previous patch image using the following equations. .

Formula 1) _xk = ( _xk-1 + Ci) mod i
Expression 2) y _k = (y _k−1 + Cj) mod j
“Mod” is an arithmetic expression indicating a remainder. For example, if x _k-1 is 8, Ci is 2, and i is 9, x _k is 1 (= 10 mod 9).

When it is determined whether or not the candidate coordinates pk (x _k , y _k ) calculated in step S252 are empty (Yes in step S253), the patch image G (k) is placed at the coordinates Whether or not the arrangement condition set in step S13 (column D6 in FIG. 6) is satisfied is determined.

  If the candidate coordinate p is not empty (No in step S253), or if the arrangement condition is not satisfied (No in step S221), all the patches in which the patch image G (k) is not arranged in the next step S254 are displayed. It is determined whether or not the determinations of S253 and S221 have been made for the empty coordinates. If it is determined (Yes in S254), no more patch images can be arranged, and the control flow is terminated.

  On the other hand, if there is an empty coordinate that has not been determined (No in S254), in the next step S255, the control unit A1 functioning as an arrangement determining unit shifts the candidate coordinate to the next candidate coordinate. In this shift process, different shift process conditions are set depending on the reason why the shift process cannot be performed. The conditions are as follows (1) to (3).

  (1) When patches already exist in the arrangement coordinates, in the longitudinal direction of the arrangement area, that is, in a direction larger than the size of i and j (provided that i and j are the same number) The coordinates are shifted by 1 in a predetermined direction (for example, x direction). If an empty arrangement coordinate is not found even after shifting in the entire longitudinal direction, the process of searching for an empty arrangement coordinate with respect to the longitudinal direction is repeated after shifting by one in the short direction.

  (2) If the arrangement condition is not satisfied (in S221), the coordinate axis common to the coordinates of the prohibited patch image and the arrangement candidate coordinates is shifted by one. For example, when the coordinate p (8, 0) of the placement candidate is the prohibited coordinate p (0, 0), the coordinate p (8, 1) obtained by shifting the common coordinate axis y by 1 is set as the next placement candidate. To do.

  (3) If the arrangement area is exceeded as a result of one shift in (1) and (2) above, the excess coordinates are set to 0.

As a result of the shift processing, if the candidate coordinate p is empty and the arrangement condition is satisfied, the arrangement of the patch image G (k) at the coordinate p (x _k , y _k ) is determined. When all the patch images are arranged, the process ends (return to FIG. 3).

  FIG. 11 is an example of arrangement according to the control flow of FIG. 10 under the same conditions as in FIG. The alphabetical characters shown in the figure indicate the type of color, the numbers indicate gradations, and the numbers in parentheses indicate the order of arrangement. In the arrangement area shown in the figure, i indicating the arrangement possible number in the x direction is 8, and j indicating the arrangement possible number in the y direction is 8. Therefore, both Ci and Cj are 3. The first patch image C1 is arranged at the coordinate p (0, 0) of the symbol H1 in the figure, and the patch image is moved by 3 (Ci) in the x direction and 3 (Cj) in the y direction, the symbol H2 Next, the next patch image C2 is arranged at the coordinates p (3, 3). Thereafter, when the region moves beyond the region by 3 in the x direction and 3 in the y direction, the region is arranged on the opposite side (remainder coordinates) of the region.

  In the figure, the arrangement candidate of the patch image Y1 indicated by reference numeral H3 is the coordinate p (0, 0) indicated by reference numeral H1, but the patch image is already arranged and the prohibition target is the coordinate p. By being present at (0, 0), as a result of repeatedly changing the placement candidate, the patch image is placed at the coordinates p (2, 1).

  As described above, by arranging the patch images so as to satisfy the predetermined relational expression, the patch images can always be arranged in the same arrangement under the same conditions, and further, the conveyance direction of the paper or orthogonal to the conveyance direction. Even if image density unevenness occurs in the direction, it is possible to provide an image forming apparatus capable of performing image density adjustment in which the influence is hardly reflected.

1 is a central sectional view of an image forming apparatus according to an embodiment. 2 is a control block diagram of the image forming apparatus. FIG. FIG. 3 is a diagram illustrating a control flow of the image forming apparatus according to the embodiment. 4 is a detailed view of a display screen in the operation display unit 2. FIG. It is a figure which shows an arrangement | positioning area | region. 4 is a detailed view of a display screen in the operation display unit 2. FIG. It is a figure which shows the subroutine process (S20) which determines arrangement | positioning. This is an example in which patch images are arranged by the arrangement determining means. This is an example in which patch images are arranged by the arrangement determining means. It is a figure which shows another subroutine process (S20) which determines arrangement | positioning. This is an example in which patch images are arranged by the arrangement determining means.

Explanation of symbols

A1 control unit (concentration control means, arrangement determination means)
DESCRIPTION OF SYMBOLS 1 Document reading part 2 Operation display part A2 HDD memory A4 Image formation part (image formation means)

Claims (9)

Arrangement determining means for determining the arrangement of the patch image for density adjustment;
An image forming unit that forms a patch image on a sheet based on the arrangement determined by the arrangement determining unit;
An image forming apparatus comprising: a density control unit that controls a density characteristic of the image forming unit based on a result of reading an image density of a patch image formed on a sheet.
The arrangement determining unit arranges patch images having at least one of density information and color information in a positional relationship in which the coordinates in the paper transport direction x and the coordinates in the orthogonal direction y orthogonal to the transport direction are different from each other. An image forming apparatus. The image forming apparatus includes a reading unit that reads a sheet,
The image forming apparatus according to claim 1, wherein the density control unit controls the density characteristic of the image forming unit based on a reading result of an image density of a patch image on a sheet read by the reading unit. . The image forming apparatus according to claim 1, wherein the arrangement determining unit arranges the density adjustment patch images at random based on a random number. The arrangement determining means assigns a predetermined order based on density information and color information to the patch image to be arranged, and sets the k−1th patch image to the coordinates p (x _k−1 , y _k−1 ) on the paper. 3. The image forming apparatus according to claim 1, wherein the following relational expression is satisfied, wherein the following k-th patch image is arranged at coordinates p (x _k , y _k ):
_{x k = (x k-1} + C i) mod i
y _k = (y _k−1 + C _j ) mod j
Where i is the number of patch images that can be arranged in the transport direction x, j is the number of patch images that can be arranged in the orthogonal direction y, C _i is the smallest integer less than or equal to 2 and less than i that does not have a prime factor of i, and C _j Is the smallest integer between 2 and less than j that does not have a prime factor of j An arrangement determining step for determining the arrangement of the patch image for density adjustment;
An image forming process for forming a patch image on paper based on the layout determined in the layout determination process;
A density control step of controlling density characteristics of the image forming unit based on a measurement result of an image density of a patch image formed on a sheet, and an image forming method of an image forming apparatus comprising:
In the arrangement determining step, the patch images having at least one of density information and color information are arranged in a positional relationship in which the coordinates in the paper transport direction x and the coordinates in the orthogonal direction y orthogonal to the transport direction are different from each other. An image forming method for an image forming apparatus. The image forming apparatus includes a reading unit that reads a sheet,
6. The image forming apparatus according to claim 5, wherein in the density control step, density characteristics of the image forming unit are controlled based on a reading result of an image density of a patch image on a sheet read by the reading unit. Image forming method. 7. The image forming method for an image forming apparatus according to claim 5, wherein in the arrangement determining step, the density adjustment patch images are randomly arranged based on random numbers. In the arrangement determining step, the patch image to be arranged is assigned a predetermined order based on density information and color information, and the k−1th patch image is represented by coordinates p (x _k−1 , y _k−1 ) on the paper. 7. The image of the image forming apparatus according to claim 5, wherein the following relational expression is satisfied, wherein the following k-th patch image is arranged at coordinates p (x _k , y _k ): Forming method.
x _k = (x _k-1 + C _i ) mod i
y _k = (y _k−1 + C _j ) mod j
Where i is the number of patch images that can be arranged in the transport direction x, j is the number of patch images that can be arranged in the orthogonal direction y, C _i is the smallest integer less than or equal to 2 and less than i that does not have a prime factor of i, and C _j Is the smallest integer between 2 and less than j that does not have a prime factor of j A color chart in which patch images for density adjustment are arranged,
A color chart in which patch images having at least one of density information and color information are arranged in a positional relationship in which the coordinate in the horizontal direction x of the paper and the coordinate in the vertical direction y of the paper are different from each other.

Images