JP2012035478A - Inkjet recording apparatus and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet recording apparatus and an inkjet recording method which complements the missing part of an image occurring due to a defective nozzle in a recording head by processing whose number of execution steps and required time are suppressed.SOLUTION: Multi-value image data is converted into binary image data showing the image having resolution higher than that of the image shown by the multi-value image data and ink is ejected from a plurality of nozzles arranged in the recording head, and recording is performed based on the binary image data. At this time, when the defective nozzle is present in the nozzles of the recording head, multi-value pixel data corresponding to the defective nozzle is specified and the density value of the specified multi-value pixel data is increased. Thus, the density of the image recorded by the nozzle located near the defective nozzle is increased and the bleeding of the image is enlarged to compensate the missing of the image caused by the defective nozzle.

Description

  The present invention relates to an ink jet recording apparatus and an ink jet recording method for performing recording by discharging ink from a plurality of nozzles arranged in a recording head.

  In an ink jet recording apparatus, an output image is formed by using a recording head in which a plurality of nozzles for discharging ink are arranged and discharging ink from each nozzle to form dots on a recording medium. In this ink jet recording apparatus, if any nozzle malfunctions or becomes clogged, ink is not ejected (non-ejection), or the ink ejection amount is insufficient or the ink ejection direction is shifted. Sometimes. When a nozzle in such a discharge failure state (hereinafter referred to as a defective nozzle) is present in the recording head, a dot is not formed at a predetermined position on the recording medium, and a blank portion is formed. This is a major factor that degrades image quality. Therefore, in such a case, it is necessary to perform a complementing process for compensating for the image portion missing due to the defective nozzle. In order to compensate for the missing portion of the image due to the presence of the defective nozzle, it is necessary to accurately detect the position of the defective nozzle in the recording head. Conventionally, many methods have been proposed for detecting defective nozzles. For example, Patent Document 1 discloses a method for optically detecting the ejection state of a nozzle.

  By the way, there is a serial type inkjet recording apparatus that forms an image by moving a recording head in a direction orthogonal to the conveyance direction of the recording medium. As one of recording methods performed by this serial type ink jet recording apparatus, a so-called multi-pass recording method is known in which the same portion on a recording medium is scanned a plurality of times with a recording head to complete an image. In the multi-pass recording method, it is possible to supplement by recording an image portion to be recorded by a nozzle having an ejection failure with another nozzle. However, since this multi-pass recording method requires a lot of time to complete an image, it is not suitable for a large amount of recording.

  On the other hand, there is a full-line type ink jet recording apparatus as an ink jet recording apparatus capable of high speed recording. However, since this full-line type ink jet recording apparatus ejects only once by a recording head to a predetermined location on a recording medium, it is difficult to supplement an image to be recorded by a nozzle that has failed ejection with another nozzle. It is. Therefore, conventionally, the following processing is performed in a full-line type ink jet recording apparatus.

  First, as the first process, as shown in Patent Document 2, a method is known in which image data recorded by a nozzle recognized as non-ejection is distributed to other nozzles adjacent in the vertical direction according to a predetermined algorithm. . According to this, it becomes possible to record an image that is not recorded due to non-ejection using other nozzles, and it is possible to compensate for image loss.

  As a second process, as shown in Patent Document 3, there is a method of increasing the density value of image data for other nozzles adjacent to the top and bottom of a nozzle recognized as non-ejection. According to this process, it is possible to compensate for image loss by increasing the density of an image formed by other nozzles adjacent to the upper and lower sides of the non-ejection nozzle and causing ink to bleed larger than usual.

Japanese Patent Laid-Open No. 10-119307 JP 2004-058284 A JP 2004-050430 A

  However, in the process disclosed in Patent Document 1, since the arrangement of the binarized recording data is changed when performing the complementing process, the number of execution steps for the process increases and a lot of processing time is required. There is a problem of becoming. That is, when the nozzle has a resolution of 1200 ppi, it is determined whether or not all of the binary raster data converted to the resolution of 1200 ppi corresponds to the non-ejection nozzle. The image data of the nozzles adjacent to is rearranged. For this reason, there are problems that the number of execution steps for performing the complementing process becomes large and a long processing time is required.

  Similarly, in Patent Document 2, it is determined whether or not all binarized image raster data correspond to non-ejection nozzles, and if so, the nozzles adjacent to the upper and lower sides are determined. A process of increasing the output density value of the corresponding image data is performed. Therefore, even in this Patent Document 2, in order to perform the complementary processing, a large number of execution steps are required, and a lot of processing time is required.

  In the processes disclosed in Patent Documents 2 and 3, the number of execution steps is simply doubled as the resolution of the recording head is improved, so that the processing time is greatly increased.

  An object of the present invention is to provide an ink jet recording apparatus and an ink jet recording method capable of complementing a missing portion of an image caused by a defective nozzle in a recording head while suppressing the number of execution steps and processing time.

  In order to solve the above problem, the present invention has the following configuration.

  That is, according to the first aspect of the present invention, binary image data representing multi-valued image data representing an image of a plurality of gradations is represented by an image having a resolution higher than that of the image represented by the multi-valued image data. And an ink jet recording apparatus that forms a recorded image by ejecting ink from a plurality of nozzles arranged in a recording head based on the binary image data, the ink ejecting of the plurality of nozzles A specifying unit that specifies pixel data corresponding to a defective nozzle among a plurality of pieces of pixel data constituting the multi-valued image data based on arrangement position information of a defective nozzle in which a defect has occurred; Density value correcting means for correcting so as to increase the density value of the multivalued pixel data.

  According to the present invention, even when a defective nozzle is generated in the recording head, it is possible to complement the missing portion of the image by the complementing process that suppresses the number of execution steps and the processing time. For this reason, it is possible to improve the recording speed and reduce resources required for processing.

It is a conceptual diagram which shows the schematic structural example of the inkjet recording system in this embodiment. 1 shows a schematic configuration of hardware of a control system in a recording system of the present embodiment. It is a figure which shows the structure of the software module of the recording system which consists of a recording device and a host device in this embodiment. It is a flowchart which shows the conventional image processing process. It is a flowchart which shows the image processing process of this embodiment. It is a flowchart which shows the procedure of the discharge defect complementation process performed in the density | concentration conversion process part of this embodiment. FIG. 4 is a diagram illustrating an example of a positional relationship between input image data and a nozzle of a recording head and a recording image recorded on a recording medium. FIG. 6 is a diagram illustrating another example of a positional relationship between input image data and a nozzle of a recording head and a recorded image recorded on a recording medium.

  Hereinafter, an embodiment of an ink jet recording apparatus of the present invention will be described with reference to the drawings.

  FIG. 1 is a conceptual diagram illustrating a schematic configuration example of an ink jet recording system according to the present embodiment. The system shown here is a full-line type ink jet recording apparatus (hereinafter also simply referred to as a recording apparatus) 101 that performs a recording operation on a recording medium, and a host that exchanges various data between the ink jet recording apparatus 101. A device (host computer) 102. The host computer 102 and the inkjet recording apparatus 101 are connected via a communication cable or the like. Then, the image data processed by the host computer 102 and various data such as cleaning commands are transmitted to the ink jet recording apparatus 101, whereby recording and other necessary operations are performed in the ink jet recording apparatus 101. Further, the inkjet recording apparatus 101 is configured so that the host computer 102 can recognize the state of the inkjet recording apparatus by transmitting a printer status such as error information of the inkjet recording apparatus 101 to the host computer 102.

  In the ink jet recording apparatus according to this embodiment, four long recording heads (line heads) 11 to 14 in which nozzles are arranged in the X direction in the drawing over a width equal to or larger than the maximum width of the recording medium to be applied. Are juxtaposed in the recording medium conveyance direction. In the present embodiment, the four line heads eject inks of different colors. In the illustrated example, 11 is a line head that ejects yellow (Y) ink, 12 is a line head that ejects magenta (M) ink, 13 is a line head that ejects cyan (C) ink, and 14 is black (K). It is a line head that ejects ink. An energy generating element for generating energy for ejecting ink is provided in each nozzle of the line heads 11 to 14. As this energy generating element, it is also possible to use an electrothermal conversion element (discharge heater) that generates thermal energy that causes film boiling in ink when energized, or an electromechanical conversion element such as a piezo.

  The recording medium P is moved along a direction (Y direction) orthogonal to the nozzle arrangement direction (X direction) by a transport unit 20 including an endless transport belt or a transport roller driven by a motor (not shown). It is conveyed so as to pass under the line heads 11 to 14. In this transport operation, when the front end portion of the recording medium P is detected by the recording medium sensor 21 disposed on the upstream side in the transport direction from the line head 11, recording on the recording medium P is performed at a predetermined timing with reference to the detection time. Operation starts.

  A light emitting unit 22 and a light receiving unit 23 are provided on one side and the other side of the line heads 11 to 14, respectively, and constitute a defective nozzle detection unit 116. The light emitting unit 22 and the light receiving unit 23 have light emitting elements and light receiving elements arranged corresponding to the line heads 11 to 14. The light emitting elements are arranged on the lower surface of the head so as to project light in the direction along the nozzle ejection opening array (X direction), and the corresponding light receiving elements can receive this light. In the defective nozzle detection operation, an optical path from the light emitting element to the light receiving element is formed, and for example, the ink ejection operation is sequentially performed from the nozzle located on one side of the head to the nozzle located on the other side. The light receiving unit 113 detects whether or not a light shielding state has occurred. Here, it is possible to determine whether or not each nozzle has normally performed a discharge operation from the drive (discharge) timing of each nozzle and the detection timing of whether or not light shielding has occurred. If a defective nozzle is detected, a cleaning operation is performed to improve the ink ejection performance.If the defective nozzle is not detected even after performing a cleaning operation after detecting a defective nozzle. It is also possible to determine that the nozzle is a defective nozzle.

  As the cleaning operation, for example, a cap capable of capping the nozzle forming surface of the recording head is provided, and ink is forcibly discharged from the nozzle by applying an appropriate pressure to the ink supply system to the head in the capped state. It can be.

  Moreover, as a mode of defective nozzle detection, it may not be automatically performed using the above-described defective nozzle detection unit. For example, a predetermined test pattern may be recorded, and the user may visually check the recording result to identify a defective nozzle and set this in the recording system.

  The recording apparatus of FIG. 1 can be selected as a recording target regardless of whether the recording medium is in the form of continuous paper or cut sheet. Further, the recording medium may be a medium comprising a mount and a label or tag sheet carried thereon.

  FIG. 2 shows a schematic configuration of control system hardware in the recording system having the above configuration.

  In FIG. 2, the recording apparatus 101 and the host computer 102 are each connected to a common network 103. The recording apparatus 101 receives recording data transmitted from the host computer 102 through the network 103, analyzes it, and performs recording processing. The recording apparatus 101 includes a printer controller 104, a printer engine 105, and an operation unit 106. The printer controller 104 performs processing related to interface with peripheral devices, control of the operation unit 106 and print data. The printer engine 105 performs control processing related to the recording operation by the recording heads 11 to 14 and the conveyance operation of the recording medium P. The printer controller 104 includes a network interface (I / F) 107, a CPU 108, an image processing ASIC 109, a nonvolatile storage device (NVRAM) 110, and a volatile storage device (RAM) 111. These devices are connected to the CPU 108, the image processing ASIC 109, and the like through dedicated controllers 106a, 110a, and 111a as necessary. The printer controller 104 is connected to the operation unit 106 through a dedicated interface. Further, the printer controller 104 is connected to the printer engine 105 via interfaces 112 and 113. The printer engine 105 includes a recording head 114, a print buffer 115, and a discharge failure detection unit 116. The control of the printer engine 105 and data exchange between the printer controller 104 and the printer engine 105 are controlled by the CPU 108.

  FIG. 3 is a diagram illustrating a configuration of software modules in a recording system including the recording apparatus and the host computer 102 according to the present embodiment. In FIG. 3, the recording apparatus 101 and the host computer 102 are each connected to a common network 103. The recording apparatus 101 includes a data reception unit 204 that controls communication processing with the network 103, an image data analysis unit 205 that decodes the received recording data and extracts multi-valued image data that represents a plurality of gradations, Is provided. In the present embodiment, the processing of the recording data receiving unit 204 and the image data analyzing unit 205 is executed by the CPU 108 shown in FIG. The recording apparatus 101 also converts the extracted multi-value image data into data for each ink color used in the recording apparatus, and the multi-value of each ink color converted by the color conversion processing section 206. A density conversion processing unit 207 for converting the density value of each image data. The density conversion processing unit 207 (density conversion unit) in the present embodiment corrects input image data so that the density value of the recorded image has a predetermined relationship with the density value represented by the input image data. It is. As a generally known density conversion process, gamma correction is performed to correct the density value of the input image data so that the density value represented by the input image data and the density value of the recorded image have a linear relationship. Yes. In contrast, in the present embodiment, in addition to the general gamma correction described above, ejection defects occur in the nozzles of the recording head for the input image data of each ink color converted by the color conversion processing unit 206. Correction processing is performed depending on whether or not Among the processes executed by the density conversion processing unit 207, some processes are performed by the image processing ASIC 109, and other processes are performed by the CPU. In this embodiment, general gamma correction processing is performed by the image processing ASIC 109, and other processing, for example, correction processing according to whether or not ejection failure has occurred in the nozzles of the recording head, is executed by the CPU 108. Is done. This correction process will be described later.

  Further, the recording apparatus 101 performs recording by the printer engine 105 based on the resolution conversion processing unit 208 that converts the resolution of the image data to a resolution equivalent to the resolution of the recording head, and the output binary image data (recording data). A recording processing unit 209 that performs the operation is provided. Furthermore, the recording apparatus 101 includes a defective nozzle detection processing unit 210 that performs a defective nozzle detection process of the recording apparatus nozzles, and a storage unit 211 that stores the defective nozzle positions detected above.

  Next, an image conversion process performed in the above configuration will be described.

  Here, in order to clarify the difference between the image conversion processing process performed in the present embodiment and the conventional image processing process, first, the conventional image processing process will be described based on the flowchart shown in FIG.

  Here, 300 ppi multi-value (8-bit) image data corresponding to each of RGB is input as an input image signal, and KCMY ink is input from the recording head 114 based on 1200 ppi binary (1-bit) image data. A description will be given assuming an example of ejection. Note that these parameters can be freely changed on the precondition that the input resolution is smaller than the output resolution, and the present invention is not limited to the above example.

  First, the recording data receiving unit 204 receives input image data transmitted from the host computer 102 (step S301). As described above, this input image data is RGB, 8-bit, 300 ppi data, is described in a predetermined PDL (page-description language) format, and is compressed in some cases.

  Next, the image data analysis unit 205 compresses / decompresses the image data and analyzes the PDL command, and extracts the bitmap data stored in the recording data (step S302). Thereafter, the bitmap data is transferred to the color conversion processing unit 206 in raster units from the top. In this embodiment, the color conversion processing unit 206 performs format conversion that converts image data represented by RGB into image data represented by KCMY, which is an ink color used in the recording apparatus (step S303). Next, the bitmap data is transferred to the density conversion processing unit 207. The density conversion processing unit 207 performs density conversion processing for making each output result look equivalent in accordance with the output level difference generated between the display device and the recording device attached to the host computer 102 (step S304). ).

  Next, the bitmap data is transferred to the resolution conversion processing unit 208. The resolution conversion processing unit 208 converts all the pixels on the transferred bitmap into 1-bit (binary) image data having a resolution of 1200 ppi in accordance with a predetermined table (step) S305). When it is confirmed that this conversion processing has been performed for all the bitmap data input to the density conversion processing unit 207 (step S306), the developed data is transferred to the recording processing unit 209. The recording processing unit 209 starts recording processing based on the binary data (hereinafter also referred to as recording data) (step S307).

  The above is the image processing process performed in the conventional ink jet recording apparatus. In this embodiment, the recording operation based on the recording data is performed in the same manner as in the existing recording apparatus. However, the processing in the density conversion processing unit 207 is conventional. Different from the inkjet recording apparatus.

  Hereinafter, based on the flowchart of FIG. 5, an image conversion processing process including the complement processing performed in the present embodiment will be described. Note that the image format before and after the conversion by the density conversion processing unit 207 and the degree of freedom thereof are the same as in the example of FIG. 4 described above.

  First, the recording data receiving unit 204 receives recording data transmitted from the host device. This recorded data is data expressed in RGB 8 bits and 300 ppi, is described in a predetermined PDL format, and is sometimes compressed (step S401).

  Next, along with the reception of the print data, the defective nozzle detection processing unit 210 detects whether or not each nozzle of each print head that discharges KCMY ink has a discharge failure, and the detection result is stored in the storage unit 211. (Step S402). The ejection failure detection process performed here can be performed using the above-described defective nozzle detection unit 116 having the light emitting unit 22 and the light receiving unit 23. However, the method for detecting the ejection failure is not limited to the method using the above-described unit, and other methods can be adopted. In addition, FIG. 5 illustrates a case where ejection failure detection is performed immediately after reception of print data, but the timing of ejection failure detection processing is not limited to this. For example, the ejection failure detection process can be executed as one process of the startup process sequence, or can be automatically executed when the apparatus is placed in an idle state for a certain period of time.

  Next, the image data analysis unit 205 performs compression / decompression of the image data and analysis of the PDL command, and extracts bitmap data included in the recording processing data (step S403). Thereafter, the bitmap data is transferred from the head to the color conversion processing unit 206 in raster units, and the color conversion processing unit 206 formats the image data expressed in RGB into the image data expressed in KCMY as described above. Conversion is performed (step S404). The KCMY image data (bitmap data) converted here is transferred to the density conversion processing unit 207. Then, the density conversion processing unit 207 performs density conversion processing for making the color output by the display device and the color of the image recorded by the recording device look the same as in step S304 (step S405).

  Further, the density conversion processing unit 207 according to the present embodiment performs a complementing process together with the above-described density conversion process. The procedure of the complementing process performed by the density conversion processing unit 207 is shown in the flowchart of FIG.

  In FIG. 6, first, when the density conversion process is started (step S501), the density conversion processing unit 207 reads out array position information of nozzles (defective nozzles) that are defective in ejection from the storage unit 211 (step S502). Next, the density conversion processing unit 207 determines whether or not there is a defective nozzle among the plurality of nozzles that record the image represented by the raster data to be subjected to density conversion processing among the rasters of the image data. A determination process is performed (step S503). In this determination process, the density conversion processing unit 207 positions the plurality of nozzles (nozzle groups) for recording the raster that is the current density conversion process target, and defective nozzles stored in the storage unit 211 in advance. This is done by collating with position information. Here, in the present embodiment, the density conversion processing unit 207 is described as a specifying unit that specifies pixel data corresponding to a defective nozzle among a plurality of pieces of pixel data constituting multivalued image data. However, the present invention is not limited, and a specific processing unit may be separately provided in the software module of FIG. Further, the processing as the specifying means is performed by the CPU 108 in FIG.

  What should be noted here is that the image data handled by the density conversion processing unit 207 has the same resolution as the input image data, whereas the defective nozzle position information stored in the storage unit 211 is the nozzle arrangement density of the recording head. The resolution is the same, and both are different. An example in which the nozzle array density in the recording head, that is, the resolution of the recording image is different from the resolution of the input image is shown in FIGS.

  FIG. 7 is a diagram showing the positional relationship between the input image data 60 and the nozzles of the recording head PH that performs a recording operation according to the input image data 60, and the recorded image 600 recorded on the recording medium. Here, the input image data 60 is composed of a plurality of raster data RA, RB,... RF,..., And each raster data is 600 ppi along the X direction orthogonal to the recording medium conveyance direction (Y direction). Is arranged at a density of. In the figure, p1 indicates input pixel data constituting each raster data.

  PH denotes a recording head (11 to 14), and nozzles n1, n2,..., N12,... Are sequentially arranged along the X direction at a density of 1200 ppi. Thus, one nozzle row is configured. An image 600 recorded by the recording head PH is composed of a plurality of pixels formed at a density of 1200 ppi in the X direction.

  As described above, in this example, the resolution of the input image data is 600 ppi, whereas the resolution of the recorded image is 1200 ppi, and the ratio between the resolutions is 1: 2. Accordingly, each raster data image constituting the input image data is recorded by a nozzle group including two nozzles adjacent in the arrangement order of the nozzles in the recording head, as shown in FIG. For example, the raster data RA image is recorded by the nozzle groups of the nozzles n1 and n2, the raster data RB image is recorded by the nozzle groups of the nozzles n3 and n4, and the raster data RC image is recorded by the nozzle groups of the nozzles n5 and n6. Recorded by. Similarly for the other raster data RD, RE, and RF images, a nozzle group composed of two adjacent nozzles, that is, a nozzle group of nozzles n7 and n8, a nozzle group of n9 and n10, and a nozzle group of n11 and n12. Each is recorded. In this way, each raster data constituting the image data and each nozzle group have a corresponding relationship.

  Here, when the defective nozzle is the nozzle n6 among the nozzles provided in the recording head PH, the raster data corresponding to the nozzle n6 is RC. However, this raster data RC also corresponds to the nozzle n5 that constitutes one nozzle group together with the nozzle n6. Therefore, even when the defective nozzle is n5, the corresponding raster data is RC.

  On the other hand, FIG. 8 shows the corresponding relationship between the input image data, the recording head, and the image data when the resolution of the input data is 300 ppi and the resolution of the image recorded by the recording head (nozzle arrangement density) is 1200 ppi. FIG. In this case, the ratio between the resolution of the input image data and the resolution of the image data is 1: 4. Accordingly, in this case, the image of each raster data constituting the input image data is recorded by a nozzle group composed of four nozzles that are continuous in the nozzle arrangement order in the recording head PH, as shown in FIG. For example, an image of raster data RA is recorded by a nozzle group including nozzles n1, n2, n3, and n4. Furthermore, an image of raster data RB is recorded by a nozzle group including nozzles n5, n6, n7, and n8, and an image of raster data RC is recorded by a nozzle group including nozzles n9, n10, n11, and n12. In this way, each raster data constituting the image data and each nozzle group have a corresponding relationship.

  Accordingly, when the defective nozzle is the nozzle n6 among the nozzles provided in the recording head PH, the raster data corresponding to the nozzle n6 is RB. However, in this case, the nozzles n5, n7, and n8 belonging to the same nozzle group as the nozzle n6 also correspond to the raster data RB. Therefore, even when the defective nozzle is any one of n5, n7, and n8, the corresponding raster data is RB.

  As described above, in the present embodiment, the nozzle arrays of the recording heads are divided into a plurality of groups according to the ratio between the input image data and the nozzle array density (recording image resolution) of the recording heads. A group is recorded in association with each raster data. At this time, in the density conversion processing unit 207, based on the defective nozzle arrangement position information read from the storage unit 211 in step S2, the nozzle group corresponding to the input image data that is the target of density conversion processing is defective. In step S3, it is determined whether or not there is a nozzle. When it is determined that there is a defective nozzle, the density conversion processing unit 207 uses a density correction coefficient N set in advance for performing the above-described general gamma correction as an ejection defect correction coefficient k. For example, it is multiplied by 1.5 (step S504). The discharge failure correction coefficient k is found to have an optimum value near 1.5 by experiment. However, the coefficient value k is not limited to this value and is greater than 1 (k> If it is 1), other values may be set.

  If it is determined that there is no defective nozzle in the nozzle group corresponding to the raster data to be subjected to the density conversion process, the multiplication process of the coefficient value 1.5 is not performed, and a general gamma is not performed. The multivalued image data subjected to the correction process is transferred to the recording processing unit 209 as it is. That is, multivalued image data subjected to general gamma correction is multiplied by a coefficient value of 1 and transferred to the recording processing unit 209 (step S505). Thereafter, the value of the multi-valued pixel data (pixel density value) constituting the raster data to be subjected to density conversion is multiplied by the final density conversion coefficient value (N × k) determined in step S504 or S505. Then, density conversion is performed (step S506).

  When the density conversion process is completed, the multivalued bitmap data subjected to the density conversion process is transferred to the resolution conversion processing unit 208 (step S507). Thereafter, the resolution conversion processing unit 208 converts all the pixels in the transferred KCMY multi-valued bitmap data into one bit of KCMY and 1200 ppi data as described in step S406 of FIG. (Step S406). When it is confirmed that the above process has been performed for all the multi-valued bitmap data (step S407), the developed data is transferred to the recording processing unit 209, and the recording process is started (step S408).

  As described above, in the present embodiment, when there is a defective nozzle in the nozzle group corresponding to the raster data to be subjected to the density conversion process, the raster data corresponding to the defective nozzle is specified, and all the raster data is configured. The density of multi-value pixel data is increased. For this reason, even when there is a defective nozzle, it is possible to complement the pixel row recorded by the defective nozzle.

  That is, in the example shown in FIG. 7, by increasing the density of the raster data RC of the input image data 60, the density value of the image data corresponding to the pixel rows 605 and 606 to be recorded by the nozzles n5 and n6 is increased. Here, since the pixel row 606 is a pixel row corresponding to the defective nozzle, ink is not applied to the pixel row 606 by the nozzle n6. However, since the value of the raster data RC is increased by 1.5 times compared to the normal state in which the nozzle n6 is not defective in discharge, the density value of the image discharged from the nozzle n5 is also increased. As a result, the density value of the pixel column 605 is also increased. For this reason, the pixel row 605 causes a larger ink bleed than usual, and the ink is also diffused to the pixel row 606 to which no ink is applied by the nozzle n6, so that the pixel row can be complemented.

  Similarly, in the example shown in FIG. 8, the density value of the raster data corresponding to the nozzle group including the defective nozzle n6 is increased. As a result, the density value of the pixel row recorded by all the nozzles n5, n7, n8 in the nozzle group to which the defective nozzle n6 belongs is increased, and the ink is diffused to the pixel row 706 to which no ink is applied by the defective nozzle n6 ( ) Thereby, the pixel row recorded by the nozzle n6 can be complemented. As described above, according to this embodiment, it is possible to greatly reduce the formation of a blank portion due to a defective nozzle, and it is possible to greatly reduce the deterioration of image quality.

  In this embodiment, when a defective nozzle exists, the density value of the multi-value raster data corresponding to the nozzle group including the pixel row recorded by the defective nozzle is corrected. For this reason, when searching for data corresponding to a defective nozzle from binarized image data and correcting the binarized image data based on the search result, as in the past Compared to the above, it is possible to perform the complementing process with an extremely small number of calculations. As a result, it is possible to reduce resources consumed for the complementary processing for defective nozzles, and to perform more efficient recording processing.

  In the above embodiment, when it is determined that a defective nozzle exists in the nozzle group corresponding to the raster data to be subjected to the density conversion process, a constant coefficient value (1.5) is added to the value of the multivalued pixel data. ). However, the present invention is not limited to this, and a coefficient value that changes according to the magnitude of the value of the multivalued image signal may be multiplied. However, also in this case, the coefficient value needs to be larger than 1.0.

  Further, in the above example, a method of executing binarization processing of image data and complementary processing for non-ejection nozzles on the recording device side is adopted, but the above processing is not limited to the method performed on the recording device. Absent. For example, the entire binarization process is performed by a printer driver on the host device, and the defective nozzle position information detected on the recording device side is transferred to the host device, which is used during the binarization process on the host device. It is also possible to adopt a configuration in which the ejection failure complement process is performed on the host device side.

  In the above embodiment, the processing of the color conversion processing unit 206 and the density conversion processing unit 207 shown in FIG. 3 is performed by the image processing ASIC 109 shown in FIG. 2, and the recording data receiving unit 204, image analysis unit 205, and recording processing unit 209 The processing is performed by the CPU. However, all or part of the processing of the color conversion processing unit 206 and the density conversion processing unit 207 may be performed by the CPU 108, and the processing performed by the CPU 108 in the above embodiment is further performed by the image processing ASIC. It is also possible to do.

  Also, part or all of the processing of each unit shown in FIG. 3 can be performed by a printer driver provided in the host computer.

  Furthermore, in the above embodiment, the case where the present invention is applied to a full-line type ink jet recording apparatus has been described as an example. However, the present invention is a serial type in which recording is performed by moving the recording head in a direction intersecting the recording medium. The present invention can also be applied to 1-pass printing in the printing apparatus.

DESCRIPTION OF SYMBOLS 101 Recording apparatus 102 Host apparatus 116 Defective nozzle detection unit 204 Data receiving part 205 Image data analysis part 206 Color conversion process part 207 Density conversion process part 208 Resolution conversion process part 209 Recording process part 210 Defective nozzle detection process part 211 Storage part

Claims (7)

Multi-valued image data representing a multi-tone image is converted into binary image data representing an image having a resolution higher than that of the image represented by the multi-valued image data, and the binary image data An inkjet recording apparatus that forms a recorded image by ejecting ink from a plurality of nozzles arranged in a recording head based on:
A specifying unit that specifies pixel data corresponding to a defective nozzle among a plurality of pixel data constituting the multi-valued image data based on arrangement position information of defective nozzles in which defective ink ejection has occurred among the plurality of nozzles. When,
Density conversion means for correcting so as to increase the density value of the multivalued pixel data specified by the specifying means;
An ink jet recording apparatus comprising:   The specifying means specifies the pixel data corresponding to the defective nozzle based on a correspondence relationship between each of the multi-valued pixel data and a plurality of nozzles consecutive in the arrangement order in the recording head. The ink jet recording apparatus according to claim 1, wherein the ink jet recording apparatus is an ink jet recording apparatus.   The number of nozzles corresponding to the multi-value pixel data is determined based on a ratio between the resolution of the image represented by the image data and the resolution of the image represented by the binary image data. The ink jet recording apparatus according to claim 2.   4. The ink jet recording apparatus according to claim 1, wherein the density conversion unit multiplies the multi-value image signal by a constant coefficient larger than 1.0.   The inkjet according to any one of claims 1 to 3, wherein the density conversion unit multiplies a coefficient greater than 1.0 that changes in accordance with the value of the multi-value image signal. Recording device. A defective nozzle detecting means for outputting information representing an array position of defective nozzles in which an ink ejection defect has occurred among the plurality of nozzles;
Storage means for storing information representing an array position of the defective nozzles,
The specifying unit specifies pixel data corresponding to a defective nozzle from among a plurality of pixel data constituting the multi-valued image data based on information indicating an array position of the defective nozzle read from the storage unit. An ink jet recording apparatus according to any one of claims 1 to 5. Multi-valued image data representing a multi-tone image is converted into binary image data representing an image having a resolution higher than that of the image represented by the multi-valued image data, and the binary image data An inkjet recording method for forming a recorded image by discharging ink from a plurality of nozzles arranged in a recording head based on
A specifying step of specifying pixel data corresponding to a defective nozzle among a plurality of pixel data constituting the multi-valued image data based on arrangement position information of a defective nozzle in which an ink ejection defect has occurred among the plurality of nozzles When,
A density conversion step of correcting so as to increase the density value of the multi-valued pixel data specified by the step;
An ink jet recording method comprising:

Images