JP7016724B2 - Recording device and recording method - Google Patents

Description

The present invention relates to a recording device and a recording method for recording by ejecting ink from an ejection port.

A recording device for recording an image on a recording medium is known by ejecting ink to a recording medium from a recording head having a row of ejection ports in which a plurality of ejection ports are arranged. The ejection characteristics of each of the plurality of ejection ports of the recording head vary, which may cause uneven density in the recorded image.

As a technique for correcting such density unevenness, a technique called head shading described in Patent Document 1 is known. In Patent Document 1, the density represented by the image data corresponding to each ejection port is changed according to the unevenness of the recorded density by each ejection port, and the density unevenness is corrected to make the density of the image uniform.

On the other hand, a part of a plurality of ejection ports of the recording head may not be ejected. In Patent Document 2, in response to the detection that a defective ejection port is present in a plurality of ejection ports, ink is ejected from each ejection port to generate a test chart for density distribution measurement. Then, it is disclosed that a correction value for correcting the density unevenness for each pixel is calculated according to the density distribution calculated by reading this.

Japanese Unexamined Patent Publication No. 2001-310535 Japanese Unexamined Patent Publication No. 2012-147126

However, in the method of Patent Document 2, when a new defective discharge port is generated after the correction value is calculated, if the correction value is used as it is, the concentration of the portion to be recorded by the defective discharge port becomes low. It is expected that it will end up.

The present invention has been made in view of the above, and an object of the present invention is to suppress uneven density of an image by performing correction corresponding to the situation even when the number of defective ejection ports changes after recording a test pattern. And.

A recording head having a plurality of ejection ports arranged in a predetermined direction and ejecting ink onto a recording medium based on image data indicating an image to be formed on the recording medium, and the plurality of ejection ports. Of these, a specific means for identifying a defective ejection port in which ink cannot be ejected normally, and a recording medium for each of a plurality of blocks in which the ejection port row is divided by controlling the recording head to record a test pattern on the recording medium. An acquisition means for acquiring density information based on the test pattern indicating the recorded density above, and based on the density information, the density of the image recorded by each block approaches the target density in units of the block. A recording device having a generation means for generating correction parameters for correcting image data used for recording, and a correction means for correcting each of the image data allocated to the plurality of blocks using the correction parameters. Further, the generation means further sets a preliminary correction parameter used when the number of defective discharge ports in the block changes after recording the test pattern for each of the plurality of blocks based on the concentration information based on the test pattern. Generated and the correction means is allocated to the block using the preliminary correction parameters generated by the generation means in response to changes in the number of defective discharge ports in the block specified by the specific means. It is characterized in that the image data is corrected.

According to the present invention, by generating a preliminary correction parameter based on the test pattern, even if the number of defective ejection ports changes after recording the test pattern, the correction corresponding to the situation is performed to reduce the density unevenness of the image. It becomes possible to suppress it.

It is a figure which shows the internal structure of the recording apparatus of an embodiment. It is a figure which shows the recording head in an embodiment. It is a figure which shows the recording control system in an embodiment. It is a figure explaining the process of image processing in an embodiment. It is a figure explaining the process of the color conversion process in an embodiment. It is a figure explaining the process of image processing in an embodiment. It is a figure which shows the test pattern in an embodiment. It is a figure explaining the HS parameter generation processing in embodiment. It is a figure explaining the HS parameter generation processing in embodiment. It is a figure which shows the HS parameter in an embodiment. It is a figure for demonstrating the HS correction processing in an embodiment. It is a figure explaining the block division in an embodiment. It is a figure explaining the complement process in an embodiment. It is a figure which shows the index pattern in an embodiment. It is a figure which shows the test pattern in an embodiment.

(First Embodiment)
The details of the embodiment will be described below with reference to the drawings. In the following description, configurations having the same function may be given the same reference numerals in the drawings, and the description thereof may be omitted.

FIG. 1 is a perspective view showing an internal configuration of an inkjet recording device (hereinafter, also referred to as a recording device) in the present embodiment.

The recording medium P supplied from the supply unit 101 is conveyed at a predetermined speed in the X direction (conveyance direction, crossing direction) while being sandwiched between the transfer roller pairs 103 and 104, and is discharged from the discharge unit 102. Recording heads 105 to 108 are arranged side by side along the transport direction between the transport roller pair 103 on the upstream side and the transport roller pair 104 on the downstream side, and are arranged in the Z direction according to binary data that determines on / off of dots. Ink is ejected to. The recording heads 105, 106, 107, and 108 are heads that eject cyan, magenta, yellow, and black inks, respectively. The discharge port of each recording head in the Y direction is provided over the entire recording medium. Such a printer is called a full line printer. Further, each ink is supplied to the recording heads 105 to 108 via a tube (not shown).

By controlling the scanner 110, the scanner controller 139 (FIG. 3) can optically read the image recorded on the recording medium P. The scanner 110 is arranged downstream of the recording head 108 in the X direction, and reading elements are arranged at a predetermined pitch in parallel with the recording heads 105 to 108.

In the present embodiment, the recording medium P may be continuous paper held in a roll shape by the supply unit 101, or may be cut paper previously cut to a standard size. In the case of continuous paper, after the recording operation by the recording heads 105 to 108 is completed, the rear end of the image is cut by the cutter 109, and the continuous paper is discharged to the paper ejection tray (not shown) by the ejection unit 102.

The recording device to which the present invention can be applied is not limited to the full-line type device described above. For example, the present invention can be applied to a so-called serial type recording device that scans a recording head or a scanner in a direction intersecting the transport direction of a recording medium to perform recording. Further, although the present embodiment uses an example in which a recording head is provided for each ink color, a form in which a plurality of colors of ink are ejected from one recording head may be used. Further, a row of ejection ports corresponding to inks of a plurality of colors may be arranged on one ejection substrate.

FIG. 2A is a schematic diagram for explaining the recording head in the present embodiment. Although only the cyan ink recording head 105 is shown here among the recording heads 105 to 108, the other recording heads 106 to 108 have the same configuration as the recording head 105. Further, an electric heat conversion element (not shown) is provided as a recording element for forming dots corresponding to each discharge port 1051 arranged in the recording head, and heat energy is generated by driving this electric heat conversion element. It is generated and ink is ejected from the ejection port. Further, a piezoelectric element, an electrostatic element, or a MEMS element can be used instead of the electric heat conversion element.

In the recording head 105, 32 ejection ports for ejecting ink are arranged in a predetermined direction. In the example shown in FIG. 2A, a discharge port row is formed by a plurality of discharge ports arranged in the Y direction (arrangement direction) intersecting the X direction. Specifically, each discharge port is arranged at a position displaced by 1/1200 inch from each other in the Y direction to form one discharge port row. The recording head 105 will be described assuming that the discharge port row is composed of only 32 discharge ports for the sake of explanation and simplification of the illustration. However, the actual recording head 105 is provided with respect to the entire width of the recording medium in the Y direction. A discharge port is provided in a recordable range. Further, although the form in which one discharge port row is composed of one row is shown here, a configuration in which one discharge port row is composed of two small rows may be used as shown in FIG. 2 (b). Further, as shown in FIG. 2C, a configuration having four discharge port rows may be used. The following description will be given on the premise that the X direction and the Y direction intersect at an angle close to a right angle to the extent that they are orthogonal to each other or can be regarded as substantially right angles.

FIG. 3 is a block diagram showing a recording control system according to the present embodiment.

The recording control system 13 in the recording device is communicably connected to the host device (DFE) HC2. Further, the host device HC2 is communicably connected to the host device HC1.

In the host device HC1, the original data that is the source of the recorded image is generated or stored. The manuscript data is generated in the form of an electronic file such as a document file or an image file. This manuscript data is transmitted to the host device HC2. The host device HC2 converts the received original data into image data that expresses an image in a data format that can be used by the recording control system 13, for example, RGB. The converted data is transmitted from the host device HC2 to the recording control system 13 in the recording device. The host device HC1 may perform conversion to a data format (for example, RGB) that can be used by the recording control system 13 and transmit the data to the main controller 13A.

The recording control system 13 is roughly classified into a main controller 13A and an engine controller 13B. The main controller 13A includes a processing unit 131, a storage unit 132, an operation unit 133, an image processing unit 134, a communication I / F (interface) 135, a buffer 136, and a communication I / F 137.

The processing unit 131 is a processor such as a CPU, executes a program stored in the storage unit 132, and controls the entire main controller 13A. The storage unit 132 is a storage device such as a RAM, ROM, hard disk, SSD, etc., stores programs and data executed by the processing unit 131, and provides a work area to the processing unit 131. In the following description, the storage unit 132 will be described as including RAM and ROM.

The operation unit 133 is, for example, an input device such as a touch panel, a keyboard, and a mouse, and receives a user's instruction.

The scanner controller 139 controls the individual reading elements of the scanner 110 shown in FIG. 1 and outputs RGB data obtained from these elements to the processing unit 131.

The image processing unit 134 is, for example, an electronic circuit having an image processing processor. The buffer 136 is, for example, a RAM, a hard disk or an SSD. The communication I / F 135 communicates with the host device HC2, and the communication I / F 137 communicates with the engine controller 13B. In FIG. 3, the broken line arrow illustrates the flow of processing of the data input to the recording control system 13. The image data received from the host device HC2 via the communication I / F 135 is stored in the buffer 136. The image processing unit 134 reads data from the buffer 136, performs predetermined image processing on the read data to generate binary data used by the print engine, and stores the read data in the buffer 136 again.

Then, the binary data after image processing stored in the buffer 136 is transmitted from the communication I / F 137 to the engine controller 13B. After that, the recording elements provided in the recording heads 105 to 108 are driven from the engine controller 13B based on the binary data, and the recording operation is performed.

Although the mode in which the processing unit 131, the storage unit 132, the image processing unit 134, and the buffer 136 are each provided is described here, the processing unit 131, the storage unit 132, the image processing unit 134, and the buffer 136 are described. It may have a plurality of forms.

FIG. 4 is a flowchart of data processing executed by the image processing unit 134 in the present embodiment.

Taking the case where the resolution (image processing resolution) of the acquired image data and the recording resolution are the same as an example, the description will be given with reference to FIG. 4 (a).

When the image processing is started, first, in step S401, the image processing unit 134 acquires the image data (RGB data) read from the buffer 136. Here, in the present embodiment, the image data is composed of information of each RGB value of 8 bits. Further, in the present embodiment, the image data has a data resolution of 1200 dpi × 1200 dpi. The image data shows any of 256 values from 0 to 255 for each pixel with a data resolution of 1200 dpi × 1200 dpi.

Next, in step S402, information for identifying an element that cannot normally form dots on the recording medium is acquired. The inability of an element to form dots normally means that the element cannot be used to form desired dots at design-appropriate positions. As an example, for example, the corresponding ejection port is clogged and the ink is not ejected, the ink droplet is twisted even if it is ejected and the ink does not adhere to the original position, or the recording element itself becomes defective and the dot recording is performed. This applies when the required function is not fulfilled. Here, taking the case of poor ink ejection as an example, a mode of acquiring defective ejection port information for specifying a defective ejection port (hereinafter referred to as a defective ejection port) will be described.

The following methods can be used to identify the defective discharge port. For example, ink is ejected from all the ejection ports of one recording head to a sheet to record a test patch, and an optical sensor or a user visually recognizes an image omission on the test patch and the omission is recognized. The discharge port corresponding to a certain location can be specified as a defective discharge port. When the user visually recognizes the image, the user inputs information about the recognized missing part of the image to the recording device 13 from the UI of the host device or the recording device 13, and the storage unit 132 stores the information.

Further, for example, while ejecting ink from all the ejection ports of one recording head, the ejection defect is detected by using a method of optically scanning the flying ink immediately after ejection with a device that optically detects the ejected ink. You can also. In this method, an optical scan unit having a light emitting unit and a light receiving unit is used. The optical scan unit is scanned so that the optical axis formed between the light emitting portion and the light receiving portion passes through the flight path of the ejected ink, and when the ink is ejected, the light from the light emitting portion is blocked. The ejection failure is detected on the principle that the amount of light received by the light receiving unit is reduced.

The defective discharge port information indicating the defective discharge port identified in this way is stored in the storage unit 132, and the information is read out in step S402. The defective discharge port information is 1-bit information indicating a discharge defect with respect to the discharge port number of the discharge port. The addresses of the information of "0" and "1" correspond to the discharge port numbers. The defective ejection port information is retained for the number of ink colors, and since it is CMYK 4 colors in this embodiment, the defective ejection port information for 4 colors is obtained.

On the other hand, when a plurality of ejection ports are assigned to one pixel as shown in FIG. 2C, the value of the defective ejection port information of one pixel is a combination of the ejection state and the position, or one. It is information of 2 bits or more indicating the state of a plurality of ejection ports assigned to the pixels.

Next, in step S403, a color conversion process for converting image data into ink color data (CMYK data) corresponding to each amount of ink used for recording on the recording medium is executed. In this embodiment, the data of CMYK 4 colors will be described, but the data of the number of ink colors other than that may be used. By the color conversion process, ink color data composed of information of each CMYK value 8 bits is generated from the original image data composed of the input information of each RGB value 8 bits. The ink color data indicates any of 256 values from 0 to 255 for each pixel having a data resolution of 1200 dpi × 1200 dpi. A three-dimensional look-up table or a method using an arithmetic expression is used for the color conversion process, and the process is performed using the one stored in the ROM of the storage unit 132 in advance.

Next, step S404 will be described. In step S404, the amount of each ink applied to the recording medium is adjusted by performing HS (head shading) correction processing on the ink color data generated in step S403. HS (head shading) is a technique for correcting density unevenness in a recorded image caused by variations in ejection characteristics of each of a plurality of ejection ports of a recording head. In the HS of the present embodiment, the ejection port row is divided into blocks of one or a plurality of continuous nozzle units, and multi-valued image data applied to the nozzles in the block is corrected using different correction parameters for each block. do. And as a preliminary step, it includes generating parameters for correction.

Specifically, first, a test pattern is recorded using a nozzle row, the test pattern is read, and the image density in the arrangement direction (Y direction) of the discharge ports is acquired for each region. Next, the correction value for each region is determined so that the entire region has a uniform density, parameters are generated, and the parameters are set for each block of the plurality of discharge ports. Then, based on the set parameter, the multi-valued image data is corrected and the density represented by the image data is changed. In the present embodiment, the process of generating the parameter is the HS parameter generation process, and the process of changing the density represented by the image data based on the correction value is the HS correction process. The HS parameter generation process will be described later.

For each color in the one-dimensional density conversion process of the HS correction process, the data converted for the input data is output. Here, the parameters used in the HS correction process are switched based on the defective discharge port information. This parameter defines the value of the output data with respect to the value of the input data, and the switching method will be described later. Here, a one-dimensional look-up table as shown in FIG. 5 is used as a parameter of the HS correction process. This point will be described in detail later.

The data (lattice point data) of this lookup table is generated by the recording device 13 performing the HS parameter generation process by instructing the recording device 13 by, for example, the user operating the UI of the recording device 13. Can be done. This HS parameter generation process is performed in the preparatory stage before recording, in addition to the image processing for data generation used for recording described with reference to FIG. FIG. 6 shows a flowchart of the HS parameter generation process. The test pattern as shown in FIG. 7 is recorded on a recording medium or a dedicated sheet for recording the test pattern, the density difference of the test pattern is read by the scanner 110, and each density in the Y direction is recognized. Based on this, the correction value is calculated so as to approach the target density so that the density becomes uniform, and the lookup data as the correction parameter is generated. Details will be described later. The generated look-up table is stored in the ROM of the storage unit 132, and the image processing unit 134 reads this data and performs HS correction processing on the data of each pixel. Specifically, a table of each ink color for each media (recording medium) type is prepared for each settable resolution.

Next, in step S405, the ink color data is quantized to generate gradation data composed of information of 1 bit of each CMYK value. This quantization process is a process for reducing the number of gradation levels, and as a method used, a dither method, an error diffusion method, or the like can be executed. In the present embodiment, the quantization process generates gradation data having a print resolution of 1200 dpi × 1200 dpi. The gradation data indicates one of two values (two-step gradation value) of levels 0 to 1 for each pixel having a print resolution of 1200 dpi × 1200 dpi. The binary data has a print resolution of 1200 dpi × 1200 dpi. In particular, the binary data indicates the formation or non-formation of dots, i.e., ink ejection or non-ejection, for each pixel recorded at a resolution of 1200 dpi × 1200 dpi on the recording medium.

On the other hand, the case where the image processing resolution and the recording resolution are different will be described below. FIG. 4C shows the processing when the resolution (image processing resolution) of the acquired image data and the recording resolution are different.

In this embodiment, the case where the image processing resolution is 600 dpi and the recording resolution is 1200 dpi will be described. The processes from steps S411 to S416 are the same as the processes of steps S401 to S405 described with reference to FIG. 4 (a).

As in the case where the image processing resolution and the recording resolution are the same, when the image processing is started, the image processing unit 134 first acquires the image data (RGB data) read from the buffer 136 in step S411. Here, in the present embodiment, the image data is composed of information of each RGB value of 8 bits. Further, in the present embodiment, the image data has a data resolution of 600 dpi × 600 dpi. The image data shows any of 256 values from 0 to 255 for each pixel with a data resolution of 600 dpi × 600 dpi.

Next, in step S412, the information indicating the defective discharge port is read out from the storage unit 132.

Then, in step S413, a color conversion process for converting the image data into ink color data (CMYK data) corresponding to each ink amount used for recording on the recording medium is executed. The ink color data indicates any of 256 values from 0 to 255 for each pixel having a data resolution of 600 dpi × 600 dpi. The color conversion process is performed using a three-dimensional look-up table or an arithmetic expression previously stored in the ROM of the storage unit 132.

Next, in step S414, HS correction processing is performed in order to adjust the amount of ink applied to the recording medium of the ink color data generated in step S413. For each color in the one-dimensional density conversion process, the data converted for the input data is output.

Next, in step S415, the ink color data is quantized to generate gradation data composed of information of 1 bit of each CMYK value. In the present embodiment, the quantization process generates gradation data having a recording resolution of 600 dpi × 600 dpi. The gradation data indicates one of five values (five levels of gradation values) of levels 0 to 4 for each pixel having a recording resolution of 600 dpi × 600 dpi.

Next, in step S416, index expansion processing is performed on the gradation data to generate binary data composed of information of 1 bit each of CMYK.

In this embodiment, index patterns A to D (bottom of the figure) as shown in FIG. 14 are used. Specifically, it has four index patterns, and these index patterns are selected and applied according to the position of the pixel group.

The numbers in each pixel of FIGS. 14A to 14D indicate a threshold value for determining ink ejection or non-ejection in comparison with the gradation value of the gradation data. Specifically, if the gradation value level is equal to or higher than the threshold value in each pixel, ink ejection is determined for that pixel, and if it is less than the threshold value, ink non-ejection is determined for that pixel.

For example, in the index pattern shown in FIG. 14A (hereinafter referred to as index pattern A), the lower right pixel is "1", the upper left pixel is "2", the lower left pixel is "3", and the upper right pixel. The threshold value of "4" is set in.

Therefore, when the gradation data indicating that the gradation value of the pixel group is level 0 is input, the gradation value of each pixel is set to 0 and compared with the threshold value. Then, the non-ejection of ink is determined for any of the 2 pixels × 2 pixels in the pixel group (FIG. 14 (A0)). Further, when gradation data having a gradation value of level 1 is input, ink ejection is determined only in the lower right pixel in which the threshold value “1” is determined (FIG. 14 (A1)). When gradation data with a gradation value of level 2 is input, ink ejection is determined in the upper left pixel in which the threshold value "2" is determined, in addition to the lower right pixel in which the threshold value "1" is determined. (FIG. 14 (A2)). Further, when gradation data having a gradation value of level 3 is input, in addition to the lower right and upper left pixels in which the threshold values "1" and "2" are defined, the lower left pixel in which the threshold value "3" is defined. Ink ejection is defined in (FIG. 14 (A3)). Then, when gradation data having a gradation value of level 4 is input, ink ejection is determined for any of the 2 pixels × 2 pixels in the pixel group (FIG. 14 (A4)).

The same applies to the index patterns shown in FIGS. 14 (B), (C), and (D).

The binary data generated by the index expansion process has a recording resolution of 1200 dpi × 1200 dpi. In detail, the binary data indicates either ink ejection or non-ejection for each pixel with a recording resolution of 1200 dpi × 1200 dpi.

(HS parameter generation process)
The HS parameter generation process will be described with reference to FIGS. 6, 8 and 9.

8 (a) to 8 (c) are diagrams for explaining each ejection port on the ejection substrate and a dot arrangement pattern represented by the ink ejected from each ejection port. 105 in FIG. 8A shows a recording head that ejects cyan ink. In the figure, for simplification of description and illustration, only 32 discharge ports 1051 are shown in the discharge port row in the recording head. Hereinafter, the recording head for ejecting 105 cyan inks will be described as a recording head having 32 ejection ports. The discharge port of FIG. 8A is divided into eight blocks each. Let each block be 21-1, 201-2, 201-3, 201-4. Here, it is assumed that, of the 32 discharge ports of the recording head 105, the blocks 21-1 and 201-2 have a standard discharge amount, and the blocks 201-3 and 201-4 have a larger discharge amount than the standard. ..

FIG. 8B is a diagram showing a recording state of dots recorded by the ink ejected from each ejection port on the recording medium P using the ejection port of FIG. 8A. In this figure, the discharge port of the block 201-1 is small, and the size of the dots recorded by the discharge port of the block 202-1 is shown by dots as small as the size of the discharge port. Further, the block 202-3 is larger than the discharge port of 202-1, and the size of the dots recorded by the discharge port of the block 202-3 is also shown by the same size as the discharge port. This is for the sake of explanation, and the sizes of the dots actually recorded by the discharge port and the discharge port are not the same. Further, the amount of ink ejected from each ejection port differs depending on the cause other than the ejection port diameter. In this explanation, it is assumed that the discharge amount varies due to the variation in the discharge port diameter. Therefore, in FIG. 8A, a discharge port having a large discharge amount is shown by a large circle, and a discharge port having a small discharge amount is shown by a small circle.

A case where a recording head having a variation in the discharge amount is used as shown in FIG. 8A will be described. Even if recording is performed based on image data showing a uniform image over each block 201-1, 201-2, 201-3, 201-4, the size of dots on the recording medium is as shown in FIG. 8 (b). There may be a difference in concentration due to the difference. The concentration may vary depending on the region.

When a recording head having such ejection characteristics is used, the image data is corrected by the HS correction process. In the case of FIG. 8, the image data corresponding to the blocks 201-3 and 201-4 in which the discharge amount becomes large is corrected so that the density is reduced. The image recorded on the recording medium after the HS correction process is shown in FIG. 8 (c).

In the present embodiment, the area of the dots recorded in the blocks 201-3 and 201-4 on the recording medium is the area of the dots recorded in the blocks 21-1 and 201-2 on the recording medium. It is double. In this case, by reducing the number of dots recorded in the blocks 201-3 and 201-4 to about 1/2, the covering area with respect to the recording medium can be made substantially the same. In this way, in the HS correction process, a look-up table that adjusts the amount of ink applied to each area is generated for each block so that the density detected for each area on the recording medium is almost the same. Will be done. This block is not limited to one having eight discharge ports as one unit, and the discharge ports may be divided into predetermined numbers. It may be divided according to the number of discharge ports having 8 or more discharge ports, or it may be divided into units having a smaller number of discharge ports, for example, it may be divided into 1 discharge port.
In the above-described embodiment, the correction is performed by changing the number of dots to the variation in the ejection amount, but for example, if a print head that can change the size of the dots in three stages of large, medium, and small is used, the dots can be corrected. Adjustments can also be made by modulating the size.

In the present embodiment, a look-up table is also generated in case a defective discharge port occurs. A description will be given with reference to FIGS. 6A and 9.

105 in FIG. 9A shows a recording head that ejects cyan ink. The 32 discharge ports are divided into 8 blocks, and the blocks are 202-1, 202-2, 202-3, and 202-4. Here, of the 32 discharge ports of the recording head 105, the block 202-1 has a smaller discharge amount than the standard, and the block 202-2 has a standard discharge amount and one defective discharge port (● in the figure). It is assumed that the blocks of the state, 202-3 and 202-4 are the standard discharge amount. At this time, the defective discharge port is specified by detecting the defective discharge port in advance. The specific method is as described above.

First, in step S501 of FIG. 6A, a test pattern is recorded. In the present embodiment, as shown in FIG. 9, the recording medium P is conveyed in the X direction while ejecting ink from all the ejection ports of the recording head 105.

FIG. 9B is a diagram showing a recording state of dots on a test pattern recorded by ink ejected from each ejection port 1051 on a recording medium P using the recording head of FIG. 9A. .. The discharge port used is displayed above the dots in the figure. Further, the position of the discharge port in FIG. 9 (a) in the Y direction and the position of the dots in FIG. 9 (b) in the Y direction are in a corresponding relationship.

Next, in step S502, the test pattern is read by using the scanner 110, and the recording density on the recording medium of each region in the Y direction is acquired.
Next, in step S503, the defective discharge port information stored in the storage unit 132 is read out.

In FIG. 9B, the block of 202-1 has a low density because the dots are small due to the small discharge amount, and the block of 202-2 has dots due to a defective discharge port (● in the figure) on the recording head 105. Not recorded and the concentration is low. When the density is corrected by the HS correction process, the density of the blocks 202-3 and 202-4 becomes equal to that of the block 202-1 by reducing the number of dots to about 3/4. In addition, the block 202-2 can normally have the number of dots 3/4 to match the density with the block 202-1, but due to the influence of the defective ejection port, the test pattern shown in FIG. 9B has already been used. One dot is not recorded. Therefore, it is only necessary to reduce the number of dots by one. The image recorded on the recording medium after the HS correction process is as shown in FIG. 9 (c). Since the ink ejection amount of the 202-1 block is smaller than the standard, the number of dots is the same, and the dot of the 202-2 block has a defective ejection port, so by reducing the number of dots by one, 3 / of the dots of the standard ejection amount block. It is 4. The blocks of 202-3 and 202-4 reduce the number of dots to 3/4.

Next, in step S504, a look-up table is generated that defines the output value with respect to the input value as a parameter for making corrections so that the density read by the scanner 110 is uniform in each block. The look-up table generated for each block is shown in FIG. 9 (d). Each table is for block 202-1, block 202-2, block 202-3, and block 202-4. As shown in the figure, a look-up table is generated so that the density of each block is uniform. When the table shown in FIG. 9 (d) is applied to the recording head in the state of FIG. 9 (a), the result of FIG. 9 (c) is obtained. Compared with the table for block 202-1, the table for block 202-2 is designed so that the output value with respect to the input value is suppressed. The output value is further suppressed in the table for block 202-3 and the table for 202-4.

Next, in S505, based on the look-up table calculated in step S504, a look-up table corresponding to a number different from the number of defective discharge ports at the time of test pattern recording is also calculated. Here, based on the defective discharge port information read out in S503, a look-up table corresponding to a number different from the number of defective discharge ports indicated by the defective discharge port information is calculated. In this way, by calculating the look-up table when there is no defective discharge port, when there is one, when there are two, and when there are three or more defective discharge ports, a look-up table corresponding to the number of possible defective discharge ports is generated. I'll do it. The look-up table corresponding to the number different from the number of defective discharge ports at the time of test pattern recording is a preliminary correction parameter for when the number of defective discharge ports changes after the test pattern is recorded. This process is performed for each block. An example of the generated look-up table is shown in FIG. 9 (e). For convenience, a curve showing data of four types of look-up tables when the defective discharge port is from 0 to 3 is displayed in the same graph area. However, each of these four types of look-up table data is stored in the storage unit 132 as separate data, and is selectively read out when it is used. Further, the output value corresponding to each input value in the lookup table is not a continuous value but a discrete value. For example, the entire input value is evenly divided into 16 and the input values of 17 grid points and the corresponding output values are stored. It is stored in the part 132. In the HS correction process described in detail later, the output value is obtained by interpolation calculation using the grid point data for the input value that is not the grid point.

Taking block 202-1 as an example, look-up for when the number of defective discharge ports is one or more based on F10 in the data of the lookup table when there is no defective discharge port generated in S504. Generate tables F11 to F13. For example, F11 to 13 can be generated by the image processing unit 134 performing a calculation based on the value of the look-up table of F10 according to a predetermined algorithm stored in the storage unit 132 in advance. This predetermined algorithm is determined based on the information obtained by the preliminary test or the like. Compared to the look-up table F10 when there is no defective discharge port, the table (F11 to F13) corresponding to the case where the number of defective discharge ports is one or more is an intermediate value (a value that is half of the maximum input value). A value is set so that the output value increases in the subsequent high gradation part.

Since the blocks 202-3 and 202-4 do not have defective discharge ports, in step S504, look-up tables F30 and F40 are generated when there are no defective discharge ports, respectively, as in block 202-1. Then, in the same manner as the block 202-1, a look-up table (F31-F33, F41-F43) when a defective discharge port is generated is generated based on F30 and F40, respectively.

On the other hand, since the block of 202-2 has one defective discharge port, in step S504, a look-up table F21 in the case of one defective discharge port is generated. Then, based on F21, a look-up table is generated when there is no defective discharge port (F20), when there are two (F22), and when there are three (F23). The method of generation is the same as that of other blocks, and a lookup table corresponding to the number of each defective discharge port is generated according to a preset calculation logic.

The look-up table corresponding to the number of defective discharge ports of each block shown in FIG. 9E described above is stored in the storage unit 132. The stored look-up table is used in the HS correction process S404, which will be described in detail later.

A look-up table is not created when there are four or more defective discharge ports in each block. When the number of defective discharge ports specified in one block exceeds a predetermined number (here, 4), the mode shifts to the maintenance mode and the recording head 105 is recovered. Examples of the recovery process include a process of sucking ink inside the ejection port from the outside and a process of performing preliminary ejection.

Further, when the number of defective discharge ports is changed as a preliminary correction parameter together with a look-up table (FIG. 9 (d)) corresponding to the number of defective discharge ports in each region when the storage unit 132 acquires the concentration information. It may take a form of holding a conversion parameter (FIG. 10) for converting to a look-up table. The conversion parameter is for converting the existing look-up table shown in FIG. 9D when a defective discharge port is newly identified. A description will be given using block 202-1 as an example. First, a look-up table F10 (FIG. 9 (d)) is calculated based on the acquired concentration information. Then, when a new defective discharge port is identified after continuing recording using the look-up table shown in FIG. 9 (d), conversion parameters F1 to F3 for converting the look-up table F10 (FIG. 10). ) To generate a new look-up table from F10. F1 to F3 in FIG. 10 correspond to the case where the number of defective discharge ports is 1 to 3, respectively, and a new lookup is performed by adding the output values of F1 to F3 to the output value of the look-up table F10. You can generate a table. The conversion parameter data is tested in advance and stored in the storage unit 132.

Further, a test pattern corresponding to the number of defective discharge ports may be formed to generate a look-up table. An example of the test pattern is shown in FIG. The pattern of FIG. 15 limits the number of ejection ports used for forming a test pattern of the same image data in the Y direction, so that the number of defective ejection ports in the block is 0, 1, 2, and 3. It is a test pattern that reproduces the time. By reading these patterns, it is possible to generate a look-up table according to the number of each defective discharge port. FIG. 15 shows a test pattern in which a certain discharge port in the block is recorded as a representative defective discharge port, but the position of the defective discharge port is not limited. For example, in order to create a look-up table according to the position of the defective discharge port in the block, the combination of all the defective discharge ports may be recorded.

(Details of HS correction processing)
Returning to FIG. 4A again, the HS correction process in step S404 will be described.

First, the number of defective discharge ports for each block is grasped from the defective discharge port information acquired in step S402. If the defective discharge port information already represents the number of defective discharge ports for each block, it is not necessary to bother to calculate it.

Next, the storage unit 132 stores a look-up table according to the number of defective discharge ports generated in S505 as a look-up table for each block. Select the table to apply to each block from among them. At this time, if the number of defective discharge ports to be acquired changes between step S503 and step S402, the applied look-up table is changed. If the number of defective discharge ports acquired does not change between step S503 and step S402, the applied look-up table may not change.

This will be specifically described with reference to FIG. FIG. 11 shows a state in which a defective discharge port is generated when the recording operation is performed. ○ is a normal discharge port, and ● is a defective discharge port. For example, the number of defective discharge ports is 2 for block 202-1, 0 for block 202-2, 1 for block 202-3, and 0 for block 202-4. Therefore, among the look-up tables shown in FIG. 9 (e), F12 is applied to the block 202-1, and F20 is applied to the block 202-2. F31 is applied to 202-3 and F40 is applied to block 202-4, and gradation correction is performed for the data for the discharge port in each block.

(Second embodiment)
In the present embodiment, in the HS parameter generation process, the block is divided so that the defective discharge port comes to the center of the block. By defining the block so that the defective discharge port is located at the center of the block, it is considered that the effect of increasing the concentration in the block is higher than that of the defective discharge port located at the end of the block. The parts having different configurations from the first embodiment will be mainly described, and the same parts may be omitted. This will be described with reference to the flowchart of FIG. 6 (b). Steps S511, S512, and S513 are the same as steps S501, S502, and S503 described with reference to FIG. 6A, respectively.

In step S514, the block is classified based on the read-out defective discharge port information. Block division is performed for each discharge port according to the recording resolution. That is, block division is performed in units of 4 discharge ports for 300 dpi, 2 discharge ports for 600 dpi, and 1 discharge port for 1200 dpi. This is because, at 300 dpi, 4 ejection ports correspond to data for 1 pixel, at 600 dpi, 2 ejection ports correspond to data for 1 pixel, and at 1200 dpi, 1 ejection port corresponds to data for 1 pixel. The discharge port row is divided so that the defective discharge port is located at the center of the block according to each recording resolution, and the block having the defective discharge port has 8 discharge ports as 1 block.

FIG. 12 shows a diagram in which the discharge port is divided into blocks. FIG. 12A exemplifies the discharge port row and its state. ○ is a normal discharge port, and ● is a defective discharge port. 12 (b) to 12 (d) show the discharge port rows of FIG. 12 (a) divided into blocks when the recording resolutions are 300 dpi, 600 dpi, and 1200 dpi. For example, in the case of 600 dpi, when the discharge ports are viewed with the two discharge ports as a unit, the blocks are divided so that the two discharge ports having the defective discharge ports come to the center of the block.

In the present embodiment, the blocks are divided so that the blocks having defective discharge ports are 8 discharge ports per block, and the blocks having only normal discharge ports may have 8 discharge ports or less per block. .. In addition, even in the block including the defective discharge port, the discharge port having less than 8 discharge ports may be one block, or the discharge port having more than 8 discharge ports may be one block. Further, all the blocks may be divided by the same number of discharge ports, and the defective discharge ports may be allowed to come to the end of the blocks to some extent.

Next, in step S515, the correction parameter for each block defined in step S514 is calculated so that the density read by the scanner 110 becomes uniform in each block.

Next, in step S516, gradation correction when there is no defective discharge port, one, two, or three or more in each block based on the correction value calculated in step S515. The value is calculated and a look-up table for each defective discharge port is generated.

(Third embodiment)
A third embodiment will be described with reference to FIG. 4 (b). In the present embodiment, a mode in which the complement processing is performed in step S406 after the quantization as shown in FIG. 4B will be described with reference to FIG.

In FIG. 13, six discharge ports 1051 are arranged in the Y direction, and ● is a defective discharge port. The pixels to be recorded by each discharge port are shown below the discharge port.

In the complement processing, when the data of the pixel indicating the ejection defect is dot formation ON (hereinafter, also simply referred to as ON) based on the defect ejection port information read out in step S402. , The data is shifted in the Y direction, distributed to nearby pixels in the Y direction, and added.

Shown below the ejection port 1051 in FIG. 13A is binary data indicating in black and white whether or not the ink generated in the quantization process of the previous step S405 is ejected. Black is dot ON (ink ejection), and white is dot OFF (ink non-ejection).

FIG. 13 (b) shows a state of recording on a recording medium according to the data of FIG. 13 (a). Pixels to be recorded by the defective ejection port are not recorded. Therefore, in the complement processing, the data of the pixels corresponding to this defective ejection port is distributed to the data for the adjacent ejection port. In this embodiment, the data is sorted and added to the data of the discharge port marked with ↓. FIG. 13 (c) shows the binary data after distribution, and FIG. 13 (d) shows the state of the recording medium when the binary data after the distribution is recorded on the recording medium according to the binary data of FIG. 13 (c).

There are no particular restrictions on the method of generating data for completion processing. Here, the binary data of the pixels to be recorded by the ejection port, which is defective in ejection, is temporarily copied to the RAM of the storage unit 132 or the register in the image processing unit 134. Then, the copied data is added to the binary data of the pixel of the complement destination (destination to which the dot data is transferred) by or operation or the like, and is used as the data of the pixel of the complement destination. The pixel data that should have been recorded by the ejection port, which is a defective ejection port, may be updated so that the dot formation indicates OFF, or may be left as it is here.

Although the above description describes the mode in which the image processing unit 134 in the recording device executes all the processes of S401 to S406 and S411 to S416, other modes can also be used. For example, the host device HC1 may execute all the processes of S401 to S406 and S411 to S416. Further, for example, the host device HC1 may execute the HS correction process (S404) and the recording device side may execute the quantization process (S405) and thereafter. Further, the host device HC2 may execute a part or all of steps S401 to S406. Further, the image data may be information on the number of bits other than each RGB value of 8 bits, and the ink color data (CMYK data) may be information on the number of bits other than each CMYK value 8 bits.

Further, the data resolution of the image data may be a resolution other than 300 dpi × 300 dpi, 600 dpi × 600 dpi, 1200 dpi × 1200 dpi.

105-108 Recording head P Recording medium 134 Image processing unit 132 Storage unit 1051 Discharge port

Claims (12)

A recording head having a row of ejection ports in which a plurality of ejection ports are arranged in a predetermined direction and ejecting ink onto the recording medium based on image data indicating an image to be formed on the recording medium.
Among the plurality of ejection ports, a specific means for identifying a defective ejection port in which ink cannot be ejected normally, and
An acquisition means for controlling the recording head to record a test pattern on a recording medium and acquiring density information based on the test pattern indicating the recording density on the recording medium for each of a plurality of divided blocks of the ejection port row. When,
Based on the density information, a generation means for generating correction parameters for correcting image data used for recording so that the density of the image recorded by each block approaches the target density in units of the block, and a generation means.
A correction means for correcting each of the image data allocated to the plurality of blocks using the correction parameters, and
It is a recording device having
The generation means further generates a preliminary correction parameter used when the number of defective discharge ports in a block changes after recording the test pattern for each of the plurality of blocks based on the concentration information based on the test pattern. ,
The correction means allocates the image data to the block using the preliminary correction parameters generated by the generation means in response to a change in the number of defective discharge ports in the block specified by the specific means. A recording device characterized by correcting. The generation means has a first number of defective discharge ports in the block based on the correction parameter generated based on the concentration information when the number of defective discharge ports in the block is the first number. The recording apparatus according to claim 1, wherein the preliminary correction parameter is generated when the number is different from the number of numbers. For each of the plurality of blocks, a storage means for storing conversion parameters according to the number of defective discharge ports in the block is further provided, and the generation means has changed the number of defective discharge ports specified by the specific means. Correspondingly, when the number of defective discharge ports is the first number, the correction parameter generated based on the concentration information is converted by the conversion parameter, so that the number of defective discharge ports in the block is first. The recording device according to claim 2, wherein the preliminary correction parameter is generated when the number is different from the number of. Each of the plurality of blocks generated by the generation means is provided with a storage means for storing a plurality of the preliminary correction parameters according to the number of defective discharge ports in the block, and the correction means is a block specified by the specific means. One of the plurality of preliminary correction parameters stored in the storage means as a correction parameter for the block in which the defective discharge port is specified according to the change in the number of defective discharge ports. The recording apparatus according to claim 1 or 2, wherein parameters are selected and used. The recording device according to any one of claims 1 to 4, further comprising a reading means for reading the test pattern, wherein the acquisition means acquires the concentration information based on the reading result of the test pattern. The acquisition means records a plurality of test patterns based on the same image data with different numbers of discharge ports used in the block of the discharge port row, and the generation means is based on the reading result of the plurality of test patterns. The recording device according to claim 5, wherein a plurality of the preliminary correction parameters are generated according to the number of defective discharge ports in the block. 1. The first aspect of the present invention is a division means for dividing the discharge port row into a plurality of divided blocks, and the division means divides the discharge port row into a plurality of blocks for each predetermined number of discharge ports. The recording device according to any one of 6 to 6. The seventh aspect of claim 7, wherein the dividing means divides the plurality of blocks of the discharge port row so that the defective discharge port in the block of the discharge port row is located at the center in the block. Recording device. The seventh or eighth aspect of the present invention, wherein the dividing means divides the discharge port row into a plurality of blocks in units of a number of discharge ports according to the data resolution of the image data. Recording device. It has complementary means for complementing the image data for the defective ejection port specified by the specific means by adding the image data for the defective ejection port and the pixels in the vicinity of the defective ejection port in the predetermined direction.
The recording device according to any one of claims 1 to 9, wherein the complementing means adds image data corrected by the correction parameter to image data of pixels in the vicinity. Claims 1 to 10 are characterized in that the plurality of preliminary correction parameters are parameters that increase the image density with respect to the same input value as the correction parameters corresponding to those having a large number of defective discharge ports. The recording device according to any one of the above items. A specific step for identifying a defective ejection port in which ink cannot be ejected normally from a row of ejection ports in which a plurality of ejection ports of a recording head for ejecting ink on a recording medium are arranged in a predetermined direction.
A pattern forming step of controlling the recording head to record a test pattern on a recording medium,
Based on the density information based on the test pattern showing the recording density on the recording medium for each of a plurality of divided blocks of the ejection port row, the density of the image recorded by each block is the target. A generation step that generates correction parameters to correct the image data used for recording to approach the density.
A correction step for correcting each of the image data allocated to the plurality of blocks using the correction parameters, and
A recording method comprising a recording step of recording an image on a recording medium using the recording head based on the corrected image data.
In the generation step, a preliminary correction parameter used when the defective discharge port in the block changes after recording the test pattern is further generated for each of the plurality of blocks based on the concentration information based on the test pattern.
In the correction step, the image data allocated to the block is corrected by using the preliminary correction parameter generated by the generation step according to the change in the number of defective discharge ports to be specified. Characteristic recording method.

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