JP2015205478A - image forming apparatus, image forming method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of performing defective (non-discharge) nozzle complementary processing while suppressing brightness deterioration caused by changes in recording time difference.SOLUTION: An image forming apparatus 2 in which a recording head 201 having a plurality of recording elements forms an image on a recording medium according to a recording pattern for each main scanning comprises: detection means 209 for detecting a defective recording element among the plurality of recording elements, and acquiring information of the defective recording element; and scanning data change means 211 for changing the recording pattern for each main scanning, and complementing the defective recording element with another normal recording element when the detection means detects the defective recording element. Before and after the change of the recording pattern for each main scanning, a recording time difference between pixels formed adjacently on the recording medium is not changed.

Description

  The present invention relates to an image forming apparatus that performs recording using a recording agent, an image forming method, and a program.

  In an ink jet recording apparatus using pigment ink as a recording agent, it is known that when the recording time difference between adjacent dots changes, the image quality of the formed image changes. For example, the uneven shape of the image formed on the recording medium affects the gloss, but the uneven shape varies depending on the recording time difference. In addition, since the sticking and bleeding of dots differ depending on the recording time difference, the change in the recording time difference also affects the color development and the graininess (roughness).

  As a technique that considers the recording time difference between adjacent dots, a technique has been proposed in which adjacent dots are recorded by the same scanning in a multi-pass recording method in order to form a highly glossy image (Patent Document 1). According to such a technique, the difference in recording time between adjacent dots is reduced and the shape of the image becomes smooth, so that a highly glossy image can be formed. However, when this technique is applied to high-concentration ink, it may be accompanied by adverse effects such as deterioration in graininess. For this reason, this technique is preferably applied only to light ink and colorless and transparent clear ink.

  Incidentally, a recording head of an ink jet recording apparatus is generally provided with a plurality of ejection nozzles for each ink, but a malfunction may occur in a part of the ejection nozzles. One of the malfunctions is non-ejection. A recent inkjet recording apparatus is provided with means for detecting such a discharge failure, and the discharge failure can be individually detected for each of a plurality of discharge nozzles provided in the recording head.

  When the non-ejection of ink occurs, the ink is not ejected to the position where it should be recorded on the recording medium, and thus visually unpleasant stripe unevenness occurs in the formed image.

  In view of this, a technique has been proposed in which a non-ejection nozzle is complemented by another normal nozzle by changing a printing pattern for each main scan in the multi-pass printing method (Patent Document 2). According to such a technique, even if the recording head includes a non-ejection nozzle, it is possible to eject ink to a position that should be originally recorded on the recording medium.

JP 2010-120291 A JP 2000-94662 A

  However, when the non-ejection nozzle complementing technique described above is used, the recording time difference between adjacent dots may change before and after the non-ejection nozzle complementation process in order to change the scan data (recording pattern for each main scan). is there. For this reason, the shape of the formed image may be partially broken, and the glossiness of the image may be deteriorated.

  Accordingly, an object of the present invention is to perform defective (non-ejection) nozzle complementation processing while suppressing deterioration in gloss caused by a change in recording time difference.

  The present invention relates to an image forming apparatus in which a recording head having a plurality of recording elements forms an image on a recording medium in accordance with a recording pattern for each main scan. A detection unit that detects and acquires information on the defective recording element; and when the detection unit detects the defective recording element, the recording pattern for each main scan is changed and another normal recording is performed. Scanning data changing means for complementing the defective printing element by an element, and the recording time difference between adjacent pixels formed on the printing medium does not change before and after the change of the printing pattern for each main scanning. It is characterized by that.

  According to the present invention, it is possible to perform defective (non-ejection) nozzle complementation processing while suppressing deterioration in gloss caused by a change in recording time difference.

1 is a block diagram illustrating a configuration of an image forming system in Embodiment 1. FIG. FIG. 2 is a diagram illustrating a configuration of a recording head in Example 1. 3 is a flowchart of image formation processing in Embodiment 1. 6 is a diagram illustrating color separation processing in Embodiment 1. FIG. FIG. 6 is a diagram illustrating an initial pass mask in the first embodiment. It is a figure which shows the path mask after the path mask change process in Example 1. FIG. It is a figure which shows the discharge failure complement setting table in Example 1. 6 is a block diagram illustrating a configuration of an image forming system in Embodiment 2. FIG. FIG. 10 is a diagram illustrating an initial pass mask in the second embodiment. It is a figure which shows the path mask after the path mask change process in Example 2. FIG. FIG. 10 is a diagram illustrating a conveyance amount setting process in the second embodiment. FIG. 10 is a block diagram illustrating a configuration of an image forming system in Embodiment 3. 10 is a diagram illustrating a part of binary image data in Embodiment 3. FIG. FIG. 10 is a diagram illustrating a part of scan data in Embodiment 3. FIG. 10 is a diagram illustrating a part of scan data after a scan data change process in Embodiment 3. 10 is a flowchart of a scan data change process in Embodiment 3. 6 is a diagram illustrating a configuration of a recording head in Embodiment 4. FIG. It is a figure which shows the initial pass mask in Example 4. FIG. It is a figure which shows the path mask after the path mask change process in Example 4. FIG.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with reference to the accompanying drawings. In addition, the structure shown in the following Examples is only an illustration, and this invention is not limited to the structure shown in figure.

[Embodiment 1] (Dots adjacent in the same pass are made adjacent in the same pass even after non-discharge complementation)
(System configuration)
FIG. 1 is a block diagram illustrating a configuration of an image forming system according to the present exemplary embodiment. As shown in FIG. 1, the image forming system includes an image processing apparatus 1 and an image forming apparatus 2. The image processing apparatus 1 can be realized by a printer driver installed in a general personal computer, for example. In this case, each component of the image processing apparatus 1 described below is realized by a computer reading a predetermined program and executing the read program. The image forming apparatus 2 is, for example, a printer, a copier, a FAX, or the like. As another system configuration, for example, the image forming apparatus 2 may include the image processing apparatus 1.

  The image processing apparatus 1 and the image forming apparatus 2 are connected by a printer interface or a circuit. The image processing apparatus 1 inputs image data to be printed from the image data input terminal 101 and stores the input image data in the input image buffer 102. The color separation processing unit 103 executes color separation processing for separating the input image data into ink colors included in the image forming apparatus 2. When this color separation processing is executed, a color separation lookup table (abbreviated as “LUT” in this specification) 104 is referred to.

  The halftone processing unit 105 generates binary image data by converting the multi-gradation values of each color obtained by the color separation processing unit 103 into binary values. However, the image data to be generated is not limited to binary image data, and may be image data having a number of gradations of two or more and less than the number of input gradations. The halftone image storage buffer 106 stores binary image data of each color obtained by the halftone processing unit 105. The binary image data stored in the halftone image storage buffer 106 is output from the image data output terminal 107 to the image forming apparatus 2.

  The image forming apparatus 2 forms an image on the recording medium 202 based on the binary image data generated by the image processing apparatus 1 by moving the recording head 201 vertically and horizontally relative to the recording medium 202. . In this embodiment, an ink jet type is used as the recording head 201. The recording head 201 includes a plurality of recording elements (nozzles). The moving unit 203 moves the recording head 201 under the control of the head control unit 204. The transport unit 205 transports the recording medium under the control of the head control unit 204. In this embodiment, a multi-pass printing method is used in which an image is completed by performing scanning a plurality of times on the printing medium with the printing head 201.

  The path separation processing unit 206 generates scanning data for each color based on the binary image data for each color generated by the image processing apparatus 1 and the path mask acquired from the path mask storage unit 208. The ink color / discharge amount selection unit 207 selects a corresponding ink color from the ink colors mounted on the recording head 201 based on the generated scanning data.

  The non-ejection nozzle detection unit 209 detects a nozzle that is in a non-ejection state among a plurality of nozzles constituting the recording head 201. Information on the detected non-ejection nozzle is stored in the non-ejection nozzle information storage unit 210. The pass mask changing unit 211 changes the pass mask based on the non-ejection nozzle information stored in the non-ejection nozzle information storage unit 210, the initial pass mask table 212, and the non-ejection complement setting table 213. The changed path mask is stored in the path mask storage unit 208.

  FIG. 2A is a diagram illustrating a configuration example of the recording head 201. In this embodiment, ink of five colors of cyan (C), magenta (M), yellow (Y), black (K), and colorless and transparent (Cl) is mounted on the recording head 201.

  FIG. 2A shows a configuration in which a plurality of nozzles are arranged in a line in the paper conveyance direction for the sake of simplicity, but the number and arrangement of nozzles are not limited to this example. For example, nozzle rows having the same color but different discharge amounts may be provided, nozzles having the same color and the same discharge amount may be provided, or a plurality of nozzles may be arranged in a zigzag manner. May be. Further, the positions of the nozzle rows may be shifted as shown in FIG. In FIG. 2, the ink color changes according to the head movement direction, but the ink color may change according to the paper transport direction.

(Image formation processing flow)
Next, image forming processing executed by the image forming system including the above-described components will be described with reference to the flowchart of FIG.

  First, the non-ejection nozzle detection unit 209 detects a nozzle in a non-ejection state among a plurality of nozzles constituting the recording head 201 (S301). Information on the detected non-ejection nozzle is stored in the non-ejection nozzle information storage unit 210.

  Next, the pass mask changing unit 211 changes the pass mask based on the non-ejection nozzle information stored in the non-ejection nozzle information storage unit 210, the initial pass mask table 212, and the non-ejection complement setting table 213, and actually A path mask to be used is generated (S302). The generated path mask is stored in the path mask storage unit 208. Details of the path mask changing process will be described later.

  Next, multi-tone color input image data is input from the image data input terminal 101 and stored in the input image buffer 102 (S303). In this embodiment, the case where the input image data is color image data constructed by three color components of red (R), green (G), and blue (B) will be described as an example.

  Next, the color separation processing unit 103 performs color separation from multi-tone color input image data stored in the input image buffer 102 to RGB to CMYKCl ink color planes using the color separation processing LUT 104. Processing is performed (S304). FIG. 4 is a schematic diagram of color separation processing in this embodiment. In this embodiment, the pixel value constituting the image data for each color after color separation processing is treated as one that can take any value from 0 to 255, but conversion to a higher number of gradations is performed. It doesn't matter.

  As described above, the recording head 201 in this embodiment has five types of ink colors (recording agents). For this reason, RGB color input image data is converted into image data of a total of 5 planes of CMYKCl planes. That is, five types of plane image data corresponding to five types of ink colors (coloring materials) are generated. As the color separation processing, a known method of conversion using an LUT is used.

  Returning to the description of FIG. The halftone processing unit 105 performs halftone processing for converting the image data after color separation into binary data (S305). In the halftone process in the present embodiment, a known error diffusion method is used as a process for converting multi-valued input image data into binary image (or an image having two or more values and less than the number of input tones). Use. Note that the halftone processing in this embodiment is not limited to the error diffusion method, and binarization may be performed by threshold processing using a dither matrix, for example.

  The binary image data after the halftone process described above is stored in the halftone image storage buffer 106. In this embodiment, the corresponding pixels of each plane are sequentially input to generate binary image data corresponding to each color. Therefore, it is not necessary to prepare a memory space that holds all the planes of the multi-valued image.

  The image data after the halftone process is output from the image data output terminal 107 in an arbitrary size such as the entire image or the bandwidth for each unit recording area.

  The image forming apparatus 2 receives the halftone image data from the image data input terminal 214, and the pass decomposition processing unit 206 performs a pass decomposition process for converting the received image data into scanning data (S306).

  Hereinafter, details of the path decomposition processing in this embodiment will be described with reference to FIG. FIG. 5 is a diagram illustrating an example of an initial path mask before change stored in the path mask storage unit 208.

  The pass decomposition processing unit 206 controls a printing element and a printing order for printing each dot by applying a multi-pass printing mask pattern M (i, j) to the binary image data B (x, y). . Here, (x, y) is a coordinate indicating the pixel position of the image, and the binary image data B (x, y) indicates the pixel value at the pixel position (x, y). That is, in a binary ink jet printer, if B (x, y) = 1, ink is ejected at pixel position (x, y), and if B (x, y) = 0, ink is ejected at pixel position (x, y). It means non-ejection.

  In this embodiment, the number of scans for multipass printing is six. The recording head 201 has 24 nozzles (there are nozzles 0 to 23 as shown in FIG. 5). The nozzles are divided into first to sixth groups, and each group includes four nozzles (ie, nozzles 0 to 3, 4 to 7, 8 to 11, as shown in FIG. 5). There are 6 groups: 12-15, 16-19, 20-23). Each group corresponds to image formation of one main scan. In FIG. 5, each mask pattern is indicated by 1 for a print permission pixel and 0 for a print non-permission pixel.

At this time, the scan data S (x, y) is obtained by the following equation (1).
S (x, y) = B (x, y) & M (x% w, y% h) (1)
Here, w and h are the width and height of the mask pattern, respectively,% represents a modulo (remainder) operation, and & represents a logical product operation.

  The scan data S (x, y) for each of the first to sixth groups is the scan data in each scan.

  Next, an ink color and a discharge amount suitable for the scan data are selected by the ink color / discharge amount selection unit 207, and image formation is started (S307). In image formation, an image is recorded on the recording medium 202 by driving each nozzle at a constant driving interval while the recording head 201 moves relative to the recording medium 202. The recording medium 202 is transported by a predetermined transport amount in the paper transport direction for each scan.

  This completes a series of image forming processes for multi-tone color input image data.

(Processing of the path mask changing unit 211)
Hereinafter, details of the path mask changing process in the present embodiment will be described with reference to FIGS. First, the path mask changing unit 211 acquires an initial path mask from the initial path mask table 212. FIG. 5 is a diagram illustrating an example of an initial path mask in the present embodiment. A feature of this initial pass mask is that a CMYK image is recorded in the first to fifth scans out of all six scans, and only clear (Cl) ink is recorded in the sixth scan. At this time, since clear (Cl) ink is recorded together in the final scan, the time difference recorded between adjacent dots is reduced. That is, this pass mask is designed to smooth the surface shape of the image.

  Next, the pass mask changing unit 211 acquires the non-ejection nozzle information stored in the non-ejection nozzle information storage unit 210. Here, it is assumed that the pass mask changing unit 211 acquires information indicating that the clear (Cl) first nozzle is not ejecting.

  Next, the pass mask changing unit 211 changes the initial pass mask based on the non-ejection nozzle information and the non-ejection complement setting table 213. FIG. 7 is a diagram illustrating an example of the discharge failure complement setting table according to the present embodiment. Each row of the table corresponds to position information indicating in which pass the nozzle that has failed to eject exists, and each column corresponds to a nozzle row of each color. This table stores a complementary rule for each pass in which a non-ejection nozzle occurs.

  As described above, in this embodiment, the case where the clear (Cl) No. 1 nozzle does not discharge is described as an example. Since the clear (Cl) No. 1 nozzle corresponds to the sixth clear (Cl) pass, the line of “Cl — 6 pass” in the table is referred to. At this time, the complement rule “0 → 4, 1 → 5, 2 → 6, 3 → 7” is stored in the Cl column of the table. This means that “the printing allowable pixels of the 0th to 3rd nozzles are moved to the 4th to 7th nozzles”. In accordance with this rule, the clear (Cl) 0-3 nozzles of the initial pass mask are moved to the clear (Cl) 4-7 nozzles (see FIGS. 5 and 6).

  In addition, “4 → 12, 5 → 13, 6 → 14, 7 → 15” are stored in the C, M, Y, and K columns for the “Cl_6 path” row of the table. Accordingly, in the C, M, Y, and K pass masks, the print permitting pixels of the 4th to 7th nozzles are similarly set in accordance with the stored rule “4 → 12, 5 → 13, 6 → 14, 7 → 15”. , Move to nozzles 12-15. Note that “-” in the table of FIG. 7 means that there is no change. N represents the nozzle number where non-ejection was detected. For example, the stored rule “n → n−8” means that when the n-th nozzle is not ejected, the printing allowable pixel of the n-th nozzle is moved to the n−8 nozzle.

  The characteristic of this non-discharge complement setting table is that when non-discharge occurs in any of the CMYK nozzles, only the pixel corresponding to the non-discharge nozzle is moved, whereas when non-discharge occurs in the Cl nozzle, That is, the pixel including the pixels corresponding to the other normal nozzles of the non-ejection nozzle is moved. This is because, in the initial pass mask shown in FIG. 5, since all the print-allowed pixels are adjacent in the same pass in the pass mask Cl, when only the non-ejection pixel is moved, the pixel is adjacent to the pixel. This is because the recording time difference from the pixel that has been changed changes.

  FIG. 6 shows a changed pass mask obtained as a result of applying the above change rule to the pass mask of FIG. Referring to FIG. 6, it can be seen that clear (Cl) ink is collectively recorded in the last scan (fifth scan) as in the initial pass mask. Therefore, the recording time difference between adjacent dots in the same pass does not change before and after the pass mask change. The changed path mask is stored in the path mask storage unit 208.

  As described above, according to this embodiment, when performing multi-pass printing, non-ejection nozzle complement processing using nozzles that print the same line in different scans is performed between adjacent dots in the same pass. It can be executed without changing the time difference. Therefore, the reproducibility of desired image quality can be improved as compared with the conventional discharge failure complement technology.

  In the present embodiment, as shown in FIG. 7, a table storing a complement rule for each pass in which ejection failure nozzles are used is used as the ejection failure complement setting table. However, the present invention is not limited to this example. For example, a complementary rule may be set for each nozzle, or a complementary rule may be set according to the scanning position of the recording head. Moreover, it is good also as a form which sets an undischarge complementation rule using methods other than a table, and acquires or calculates this set rule.

[Embodiment 2] (Passes are shifted so as to change the paper feed amount without changing the number of passes.)
In the first embodiment, when there is a nozzle that has failed to eject even one of the nozzles that records clear (Cl) ink in the sixth pass, all of the print-allowed pixels that are recorded in the sixth pass are set to five. Changed to record in pass.

  However, in Example 1, many usable nozzles are not used, and nozzles for one pass are wasted. As a result, the CMYK image originally recorded by five scans is recorded by four scans. As a result, various image quality may be deteriorated.

  Therefore, in this embodiment, an example will be described in which discharge failure complement processing is performed in which the printing time difference between adjacent dots in the same pass does not change without changing the number of scans. In the following description of the present embodiment, the description common to the first embodiment is simplified or omitted.

  FIG. 8 is a block diagram showing the configuration of the image forming system in this embodiment. As illustrated in FIG. 8, the image forming apparatus 2 includes a carry amount setting unit 215. The conveyance amount setting unit 215 acquires non-ejection nozzle information from the non-ejection nozzle information storage unit 210 and sets the conveyance amount of the recording medium 202 in the conveyance unit 205 based on the acquired non-ejection nozzle information. A method for setting the carry amount will be described later.

  In this embodiment, description will be made assuming that the number of nozzles is 768. FIG. 9 shows a schematic diagram of an initial pass mask in the present embodiment. As in the pass mask shown in FIG. 5, a CMYK image is recorded in the first to fifth scans out of all six scans, and only clear (Cl) ink is recorded in the sixth scan.

  The nozzle number for the nozzle at the upper end of the nozzle row is 0, and the nozzle number for the nozzle at the lower end is 767. 128 nozzles from nozzle numbers 640 to 767 correspond to the first pass recording. Similarly, 128 nozzles with nozzle numbers 512 to 639 correspond to the second pass printing, and 128 nozzles with nozzle numbers 384 to 511 correspond to the third pass printing. Thus, 128 nozzles are assigned to each pass. Therefore, when the pass mask shown in FIG. 9 is used, the conveyance amount of the recording medium conveyed every time one scan is completed corresponds to the length of 128 nozzles.

(Processing of the transport amount setting unit 215)
A transport amount setting method in the transport amount setting unit 215 will be described with reference to FIGS. 10 and 11. Here, a case where the clear (Cl) No. 10 nozzle is not ejecting will be described as an example. At this time, the carry amount setting unit 215 sets the carry amount to a length corresponding to 126 nozzles (see FIG. 11). More specifically, the transport amount L can be determined as the largest integer that satisfies the following inequality (2).
L ≦ (N-1-n) / P (2)
Here, N is the number of nozzles, P is the number of passes, and n is the nozzle number of Cl that has failed to eject. In the above case, N = 768, P = 6, n = 10, and L ≦ (768-1-10) / 6, so that L ≦ 126.1 can be derived. Therefore, the carry amount L is determined to be 126 [nozzles].

  Further, the pass mask generated by the pass mask changing unit 211 does not disable all the nozzles in the sixth pass (128 nozzles from nozzle numbers 0 to 127), but from nozzle numbers 0 to 10. The 11 nozzles up to are not used. Then, 126 nozzles from No. 11 to No. 136 are assigned to the sixth pass printing. Similarly, 126 nozzles are assigned to each pass, such as nozzle numbers 137 to 262 for the fifth pass and nozzle numbers 263 to 388 for the fourth pass.

  FIG. 10 is a schematic diagram of the pass mask after the pass mask changing process. As shown in FIG. 10, nozzles Nos. 11 to 136 are used in the sixth pass, and nozzles above the No. 10 nozzle that has failed are not used. Further, since the same number of nozzles are allocated to each pass, the nozzle number 767 is not used. In the first embodiment, nozzles for one pass (corresponding to 128 nozzles) cannot be used, but in the present embodiment, only 12 nozzles cannot be used at most, and the number of scans is six. It has not changed.

  As described above, according to the present embodiment, in addition to the effects obtained in the first embodiment, usable nozzles are used as much as possible, and undischarge complementing processing that does not change the number of scans for CMYK images can be realized.

[Example 3] (Considering the recording time difference between adjacent dots in different passes)
In Example 1, the discharge failure complement process was performed without changing the recording time difference between adjacent dots in the same pass.

  However, the focus of the first embodiment is only the recording time difference between adjacent dots in the same pass, and does not consider the recording time difference between adjacent dots in different passes. For example, when the adjacent dots recorded in the first pass and the second pass when there is no non-ejection nozzle are recorded in the first pass and the sixth pass by the non-discharge complementing process, the recording between these dots is performed. The time difference changes greatly. Thereby, various image quality may change.

  Therefore, in this embodiment, a non-discharge complementing process will be described in consideration of a recording time difference between adjacent dots in different passes. In the following description of the present embodiment, the description common to the first embodiment is simplified or omitted.

  FIG. 12 is a block diagram showing the configuration of the image forming system in this embodiment. As shown in FIG. 12, the image forming apparatus 2 includes a scan data changing unit 216. The scan data changing unit 216 acquires the non-ejection nozzle information from the non-ejection nozzle information storage unit 210 and changes the scan data obtained from the pass decomposition processing unit 206. A method for changing the scan data will be described later.

  FIG. 13 shows an example of binary image data stored in the halftone image storage buffer 106. For the sake of simplicity, FIG. 13 shows only binary image data for black (K) and clear (Cl). In FIG. 13, pixels painted black represent dots on which ink is recorded. Referring to FIG. 13, the binary image K has an arrangement in which the dots are dispersed, and the binary image Cl has an arrangement in which the dots are concentrated. The arrangement shown in FIG. 13 is a design example for the purpose of improving the gloss by concentrating the Cl ink while preventing the granularity from being deteriorated by dispersing the K ink. In FIG. 13, numbers 0 to 23 shown on the right side of the binary image are recorded by nozzles (0 to 23) of which nozzle number among the nozzles shown in FIG. Represents.

  The pass separation processing unit 206 generates scan data for each color based on the binary image data for each color and the pass mask acquired from the pass mask storage unit 208. FIG. 14 shows scan data obtained by pass-decomposing the binary image data shown in FIG. 13 using the pass mask shown in FIG. Here, for simplicity, only the upper four lines of the binary image data shown in FIG. 13 are shown. Scan data from the first pass to the sixth pass is obtained for each color.

(Processing of scanning data changing unit 216)
Below, the process performed by the scanning data change part 216 is demonstrated using the flowchart of FIG.

  First, in S1601, non-ejection nozzle information is acquired from the non-ejection nozzle information storage unit 210, and the presence / absence of non-ejection nozzle information is determined. As a result of the determination, if there is no non-ejection nozzle, the scanning data change process is terminated, and if there is a non-ejection nozzle, the process proceeds to S1602. In the following, a case where the clear (Cl) No. 1 nozzle has acquired information indicating non-ejection will be described as an example.

  In S1602, the scanning data acquired from the pass decomposition processing unit 206 is referred to, and the recording time difference between the pixels that are overlapped or recorded adjacent to each other is acquired. In the example illustrated in FIG. 13, first, the binary image K and the binary image Cl are referred to, and adjacent pixels of the same color, adjacent pixels of different colors, and overlapping pixels of different colors are extracted. Then, with reference to the scan data K and the scan data Cl in FIG. 14, the recording time difference between each pixel and the pixel extracted for each pixel is acquired. Next, the process proceeds to S1603.

  In S1603, in the scan data, the pixel of the scan data recorded by the non-ejection nozzle is moved to another pass so as to be recorded by the normal nozzle. In the example shown in FIG. 14, three pixels (Cl1, Cl2, Cl6) recorded in the second row from the top of the sixth pass of the scan data Cl, corresponding to the non-ejection nozzle (Cl No. 1 nozzle), Move to the fifth pass (see FIG. 15). Next, the process proceeds to S1604.

  In S1604, all the pixels that overlap or are adjacent to the pixel moved in S1603 are extracted, and the recording time difference between the moved pixel and the extracted pixel is acquired. In the example of FIG. 14, three pixels (Cl3, Cl4, Cl5) of scanning data Cl and three pixels (K1, K2, K3) of scanning data K adjacent to the three moved pixels (Cl1, Cl2, Cl6) are extracted. The A recording time difference between these extracted pixels and the moved three pixels (Cl1, Cl2, and Cl6 moved in the fifth pass) is acquired. Next, the process proceeds to S1605.

  In S1605, pixels having a recording time difference different from the recording time difference acquired in S1602 are extracted from the pixels extracted in S1604, and the number is counted. In the example of FIG. 14, for pixels Cl3, Cl4, and Cl5, the recording time difference changes from 0 to 1 in terms of the number of passes. The recording time difference also changes for the pixels K1, K2, and K3. Therefore, the count number in this case is 6. Next, the process proceeds to S1606.

  In S1606, one pixel is selected from the pixels extracted in S1605. The selection method is arbitrary, but a pixel that has not yet been selected is selected. Here, the description will be made assuming that the pixel Cl3 shown in FIG. 14 is selected. Next, the process proceeds to S1607.

  In S1607, the pixel selected in S1606 is moved to another pass (normal nozzle). Here, it is assumed that the pixel Cl3 is moved from the sixth pass to the fifth pass. Next, the process proceeds to S1608.

  In S1608, as in S1605, pixels with different recording time differences are counted. That is, in the example described here, the number of pixels in which the recording time difference from the moved three pixels (the pixels Cl1, Cl2, and Cl6 in the fifth pass) is different from the recording time difference acquired in S1602 is counted. Here, since the pixel Cl3 is moved to the fifth pass in S1607, the recording time difference with respect to the pixel Cl3 becomes the same as the time difference acquired in S1602. Therefore, the count number in this case is 5. Next, the process proceeds to S1609.

  In S1609, it is determined whether the count number has decreased by comparing the count number acquired in S1608 with the count number acquired in S1605. As a result of the determination, if the count number has decreased, the process proceeds to S1610, and if not, the process proceeds to S1612.

  In S1610, the recording pattern for each main scanning obtained by moving the pixels in S1607 is set as a new recording pattern for each main scanning. Also, the count number is updated to the count number acquired in S1608. Further, the pixel (Cl3) moved in S1607 is added to the pixels (Cl1, Cl2, Cl6) moved in S1603. Next, the process proceeds to S1611.

  In step S1611, it is determined whether movement has been attempted for all the pixels extracted in step S1605. As a result of the determination, if it is not attempted to move all the extracted pixels, the process returns to S1606, a new extracted pixel is selected, and if all the pixels are attempted to move, the process is terminated.

  In S1612, the pixel moved in S1607 is returned to the original pass. Next, the process proceeds to S1613.

  In S1613, it is determined whether or not all the movement destination paths have been tried for the pixel selected in S1607. If all the destination paths have not been tried as a result of the determination, the process advances to step S1614 to newly select and set the destination path, and the process returns to step S1607. Otherwise, the process proceeds to S1611.

  FIG. 15 shows an example of scan data obtained by this embodiment. The pixels Cl1, Cl2, and Cl6 at the non-ejection nozzle position have moved from the sixth pass to the fifth pass. In addition, Cl3, Cl4, and Cl5 that are adjacent to the pixels Cl1, Cl2, and Cl6 in the sixth pass also move from the sixth pass to the fifth pass. Therefore, the recording time difference between these adjacent pixels is not changed. Further, since the pixel Cl3 has moved from the sixth pass to the fifth pass, the pixel K1 that has a different color and overlaps with the pixel Cl3 after the movement has moved from the fifth pass to the fourth pass. Further, for the pixels K2 and K3 that are adjacent to each other in a different color from the pixel Cl2 before the movement, the pixel K2 is changed from the fourth pass to the third pass as the pixel Cl2 moves from the sixth pass to the fifth pass. The pixel K3 has moved from the second pass to the first pass. Therefore, the recording time difference between these pixels is not changed.

  As described above, according to the present embodiment, the discharge failure complement process can be executed without changing not only the printing time difference between adjacent dots in the same pass, but also the printing time difference between adjacent dots in different passes. Become. Therefore, the reproducibility of the desired image quality can be further improved.

(Modification considering the recording time difference in bidirectional printing)
In this embodiment, the description of the recording time difference that occurs in bidirectional printing is omitted. However, an embodiment in which the influence of bidirectional printing is taken into account when acquiring the recording time difference in the flow shown in FIG.

  As an example of the influence of bi-directional printing, recording is performed while moving the recording head from right to left in the odd-numbered pass, and recording is performed while moving the head from left to right in the even-numbered pass. Think. At this time, focusing on the left end of the recording medium, the recording time difference between the first pass recording and the second pass recording is small, but the recording time difference between the second pass recording and the third pass recording is growing. On the other hand, at the right end of the recording medium, the recording time difference between the first pass recording and the second pass recording is large, but the recording time difference between the second pass recording and the third pass recording is small.

  In consideration of this influence, when the recording time difference in the flow shown in FIG. 17 is acquired, the present invention can be bidirectionally printed by using the actual time difference assumed from the bidirectional printing instead of the simple pass number conversion value. It is also possible to apply to.

[Example 4] (When there are two clear nozzle rows)
In the first embodiment, as illustrated in FIG. 2, an example of discharge failure complement processing in the case where the recording head 201 includes one nozzle row for each of the five colors of CMYKCl is shown.

  However, various configurations are possible for the configuration of the recording head 201. In particular, in an application in which gloss reproduction is important, there may be a form in which the recording head 201 includes two colorless and transparent clear (Cl) nozzle rows.

  Therefore, in this embodiment, an example in which discharge failure complement processing is performed without changing the printing time difference between adjacent dots in the same pass in the embodiment in which the print head 201 includes two clear (Cl) nozzle rows will be described. In the following description of the present embodiment, the description common to the first embodiment is simplified or omitted.

  FIG. 17A shows the configuration of the recording head 201 in this embodiment. In this embodiment, the recording head 201 includes one nozzle row for cyan (C), magenta (M), yellow (Y), and black (K), and two nozzles for clear (Cl). Columns Cl1 and Cl2 are provided. In order to reduce the recording time difference between the clear (Cl) nozzle rows in the same pass, it is desirable that the distance between the clear (Cl) nozzle rows is small as shown in FIG. As shown in FIG. 17B, the clear nozzle rows may be separated to some extent.

  FIG. 18 is a diagram illustrating an example of the initial pass mask according to the present embodiment. Since the print head 201 includes two nozzle rows for clear (Cl), in FIG. 18, the respective pass masks are distinguished as pass mask Cl1 and pass mask Cl2. The pass mask shown in FIG. 18 records a CMYK image in the first to fifth scans out of all six scans, similarly to the pass mask shown in FIG. Further, the clear (Cl) ink is collectively recorded in the sixth scan. Since the recording time difference between the sixth pass recording of the pass mask Cl1 and the sixth pass recording of the pass mask Cl2 is minute, the surface shape of the image can be smoothed.

  FIG. 19 is a diagram illustrating an example of a pass mask generated by the pass mask changing unit 211 when the clear (Cl1) nozzle No. 1 does not eject. Referring to FIGS. 18 and 19, the pixel recorded by the clear (Cl1) No. 1 nozzle has moved to the clear (Cl2) No. 1 nozzle. In this way, by moving the print permitting pixel corresponding to the non-ejection nozzle to the clear (Cl2) No. 1 nozzle, it is adjacent in the same pass as compared to the case of moving to the clear (Cl1) No. 5 nozzle. It is possible to reduce the change in the recording time difference between the pixels. In this embodiment, the number of scans does not change as in the first embodiment. Furthermore, in this embodiment, it is not necessary to change the paper feed amount as in the second embodiment.

  As described above, according to the present embodiment, the undischarge complementing process in which the difference in recording time between adjacent pixels in the same pass can be realized by a simple complementing process.

[Other Examples]
(Ink type and input image type are optional)
In the embodiment described above, the inks are five colors, CMYK and Cl, but the present invention is not limited to the color and the number of colors of the ink. Light inks such as light cyan, light magenta, and gray, and special color inks such as red, green, and blue can be used, and metallic inks can also be used.

  In the above-described embodiments, the example in which the ink that is recorded adjacently in the same pass is the Cl ink has been described. However, the ink that is recorded adjacently in the same pass may be an ink other than the Cl ink. However, at this time, in consideration of the roughness of the image, it is preferable that only light (low density) light ink or clear ink be recorded adjacently in the same pass. In addition, since it is considered that the ink recorded on the outermost surface contributes most to the surface shape, it is also preferable that only the ink recorded on the outermost surface is recorded adjacently in the same pass. In the case where there are a plurality of ink types adjacent to each other in the same pass, the present invention may be applied to all of them, or may be applied to some of them.

  In the above-described embodiments, the input image data is an RGB color multi-tone image, but the present invention is not limited to the type of input image data. The input image data may be a monochrome image or a spectral image. Further, as input image data, a CMYKCl plane image after color separation processing may be input, or a binary image after halftone processing may be input.

(Recording head configuration and recording method are arbitrary)
In the embodiment described above, the number of nozzles is set to 24 or 768 and the number of scans during normal operation is set to 6 for the sake of explanation. However, the present invention is not limited to any value, and the number of nozzles and the number of scans are arbitrarily set. May be set.

  In the above-described embodiments, the recording head is moved along a direction orthogonal to the moving direction of the recording medium. However, the relative positional relationship in the movement between the recording head and the recording medium is not limited to the above-described example. For example, even in an embodiment using a long recording head called a full line type, the present invention can be applied as long as it has a plurality of nozzles corresponding to a multi-pass recording method. Also, the present invention can be applied to a recording apparatus (for example, a thermal transfer system or an electrophotographic system) that performs recording according to a system other than the ink jet system, as long as the recording system corresponds to a multipass recording system. In this case, the nozzle for ejecting ink droplets corresponds to a recording element for recording dots or a laser light emitting element.

(A defective nozzle is not limited to a non-ejection nozzle)
In the embodiment described above, the example of the non-ejection nozzle is used as the defective nozzle in which the malfunction occurs. However, the type of malfunction is not limited to non-ejection. For example, the defective nozzle may be a defective discharge nozzle that discharges only a smaller volume than a predetermined ink droplet, or a discharge nozzle that bends the flying direction of the ink droplet. That is, the term “defective nozzle” as used in this specification means a nozzle that cannot be used or a nozzle that is not preferable to use. The present invention relates to a technique for complementing a defective nozzle with another normal nozzle, and the present invention can be applied to any defective nozzle.

(The recording time difference may change in some pixels)
In the above-described embodiments, the processing for not changing the recording time difference between adjacent pixels in the same pass for all the pixels has been described with some examples. However, in the present invention, it is not always necessary to make the recording time difference between adjacent pixels in the same pass unchanged for all pixels. The essential feature of the present invention is to obtain a desired reproduction by minimizing the recording time difference between adjacent pixels in the same pass when complementing a defective recording element, and the recording time difference in some pixels changes. Such various modifications can be easily implemented. Of course, it is desirable that the ratio of pixels in which the recording time difference changes is small, and in order not to be visually noticeable, the pixels in which the recording time difference changes may be less than half of the total number of pixels in which the recording pattern is changed. desirable. Further, since the ink that is preferably recorded adjacently in the same pass is a light ink or a colorless and transparent clear ink, a modified example in which at least the recording time difference between the light ink and the clear ink does not change is easily implemented. Is possible. In addition, when the change in the recording time difference is sufficiently small, a modification in which the recording time difference is not changed can be easily implemented.

(Programs, recording media, etc.)
The present invention can take the form of, for example, a system, apparatus, method, program, or storage medium (recording medium). Specifically, the present invention may be applied to a system constituted by a plurality of devices (for example, a host computer, an interface device, an imaging device, a web application, etc.), or may be applied to a device (part) constituting one device. It may be applied.

  The present invention also provides a software program that implements the functions of the above-described embodiments directly or remotely to a system or apparatus, and the system or apparatus computer reads and executes the supplied program code. Achieved. Note that the program in this case is a program corresponding to the flowchart illustrated in the above-described embodiment.

  Accordingly, since the functions of the present invention are implemented by computer, the program code installed in the computer also implements the present invention. That is, the computer program itself for realizing the functional processing of the present invention is also included in the scope of the present invention.

  In this case, the computer program only needs to have a program function, and may be in the form of object code, a program executed by an interpreter, script data supplied to the OS, or the like.

  Recording media for supplying the program include the following media. For example, floppy (registered trademark) disk, hard disk, optical disk, magneto-optical disk, MO, CD-ROM, CD-R, CD-RW, magnetic tape, nonvolatile memory card, ROM, DVD (DVD-ROM, DVD- R) etc.

  As a program supply method, the following method is also possible. That is, the browser of the client computer is connected to a homepage on the Internet, and the computer program itself (or a compressed file including an automatic installation function) of the present invention is downloaded to a recording medium such as a hard disk. It can also be realized by dividing the program code constituting the program of the present invention into a plurality of files and downloading each file from a different homepage. That is, a WWW server that allows a plurality of users to download a program file for realizing the functional processing of the present invention on a computer is also included in the scope of the present invention.

  In addition, the program of the present invention is encrypted, stored in a storage medium such as a CD-ROM, distributed to users, and key information for decryption is downloaded from a homepage via the Internet to users who have cleared predetermined conditions. It is also possible to make it. That is, the user can execute the encrypted program by using the key information and install the software on the computer.

  Further, the functions of the above-described embodiments are realized by the computer executing the read program. Furthermore, based on the instructions of the program, the OS running on the computer performs part or all of the actual processing, and the functions of the above-described embodiments can be realized by the processing.

  Further, the program read from the recording medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, and then executed. Function is realized. That is, based on the instructions of the program, the CPU provided in the function expansion board or function expansion unit can perform part or all of the actual processing.

Claims (11)

An image forming apparatus in which a recording head including a plurality of recording elements forms an image on a recording medium according to a recording pattern for each main scan,
Detecting means for detecting a defective recording element of the plurality of recording elements and acquiring information of the defective recording element;
Scanning data changing means for changing the recording pattern for each main scan when the detecting means detects the defective recording element, and supplementing the defective recording element with another normal recording element;
An image forming apparatus, wherein a difference in recording time between adjacent pixels formed on the recording medium does not change before and after the change of the recording pattern for each main scan.   Pixels formed adjacently by the same main scan in the recording pattern for each main scan before the change are formed adjacent by the same main scan in the recording pattern for each main scan after the change. The image forming apparatus according to claim 1, wherein: Further comprising setting means for setting the conveyance amount of the recording medium,
The image forming apparatus according to claim 1, wherein the setting unit sets a conveyance amount based on the acquired information of the defective recording element.   The scan data changing means changes scan data by referring to a table storing rules for changing a print pattern for each main scan, which is associated with information on the defective print element. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The image forming apparatus according to claim 1, wherein the recording agent recorded by the recording element is colorless and transparent or has a low density.   The image forming apparatus according to claim 5, wherein the recording agent is colorless and transparent, and the recording head includes a plurality of nozzle rows of the colorless and transparent recording agent.   The image forming apparatus according to claim 5, wherein the recording agent has a low concentration, and the recording head includes a plurality of nozzle rows of the low concentration recording agent.   The image according to any one of claims 1 to 7, wherein the recording agent recorded by the recording element is a recording agent recorded on the outermost surface of an image formed on the recording medium. Forming equipment.   Of the pixels whose recording pattern for each main scan is changed before and after the change, the number of pixels whose recording time difference has changed is the total number of pixels whose recording pattern for each main scan is changed before and after the change. The image forming apparatus according to claim 1, wherein the image forming apparatus is half or less. An image forming method executed by an image forming apparatus in which a recording head including a plurality of recording elements forms an image on a recording medium according to a recording pattern for each main scan,
A detecting step of detecting a defective recording element of the plurality of recording elements and acquiring information of the defective recording element;
A scanning data changing step of changing the recording pattern for each main scan and supplementing the defective recording element with another normal recording element when the defective recording element is detected in the detecting step. ,
An image forming method, wherein a difference in recording time between adjacent pixels formed on the recording medium does not change before and after the change of the recording pattern for each main scan.   The program which makes a computer perform the method of Claim 10.

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