WO2018142708A1

WO2018142708A1 - Method for setting reference value, information processing device, and image recording device

Info

Publication number: WO2018142708A1
Application number: PCT/JP2017/040179
Authority: WO
Inventors: 健一郎平本
Original assignee: コニカミノルタ株式会社
Priority date: 2017-01-31
Filing date: 2017-11-08
Publication date: 2018-08-09
Also published as: JP6908057B2; JPWO2018142708A1

Abstract

Provided are a method for setting a reference value, an information processing device, and an image recording device with which it is possible to set a reference value that enables more reliable suppression of reductions in the picture quality of a recorded image while suppressing an increase in data volume. The method for setting reference values includes: a step for acquiring an output color value that represents a pixel color outputted by a recording element included in each of a plurality of recording element sections; and a step for carrying out a bit count reduction process for generating, from color value data based on the output color value, low-bit-count color value data the bit count of which is less than that of the color value data, in the order in which the plurality of recording element sections are arrayed, and in the bit count reduction process where the beginning in the array order is excluded, acquiring the cumulative value of error values generated in correspondence with a difference in the color values of the color value data and the low-bit-count color value data in the bit count reduction process up to the preceding stage, generating low-bit-count color value data that has undergone a color value adjustment based on the cumulative value, and setting a reference value on the basis of the generated low-bit-count output color value data.

Description

Reference value setting method, information processing apparatus, and image recording apparatus

The present invention relates to a reference value setting method, an information processing apparatus, and an image recording apparatus.

Conventionally, each of a plurality of recording elements provided at different positions in a predetermined direction performs an output operation according to an input value of image data, and outputs pixels to a recording medium with a predetermined number of recording gradations. There is an image recording apparatus for recording an image on the recording medium. As a method of outputting colored pixels in an image recording apparatus, there is a method of discharging color ink from a nozzle provided in a recording element to a recording medium with a liquid amount corresponding to an input value per unit area.

In such an image recording apparatus, reference data (correction) in which reference values for correcting an error between the color value of the color indicated by the input value and the color value of the pixel color output by the recording element are arranged. Table) and using the reference data to correct the input value of the image data to the corrected input value, the color value of the color indicated by the input value and the color value of the color of the pixel output by the printing element are obtained. There is a technique of matching (for example, Patent Document 1).

JP 2006-270771 A

However, a deviation caused by a quantum error included in the correction input value occurs between the color value of the color indicated by the input value and the color value of the pixel color output according to the correction input value by the printing element. obtain. For this reason, the above-described conventional technique has a problem in that it is impossible to reliably suppress deterioration in image quality due to color unevenness caused by the color value deviation in the recorded image.
On the other hand, by increasing the number of gradations of the reference value used for determining the correction input value in the reference data, an attempt is made to acquire a more accurate correction input value and suppress the color value shift caused by the quantum error. Then, there exists a subject that the data amount of reference data will increase.

An object of the present invention is to provide a reference value setting method, an information processing apparatus, and an image recording capable of setting a reference value capable of more reliably suppressing a decrease in image quality of a recorded image while suppressing an increase in data amount. To provide an apparatus.

In order to achieve the above object, the invention of the reference value setting method according to claim 1 comprises:
A plurality of recording elements that are provided at different positions in a predetermined direction and that each perform an output operation for outputting colored pixels to a recording medium, and the plurality of recording elements based on a corrected input value obtained by correcting an input value The input value in the image recording apparatus, comprising: a recording control unit configured to record the image by outputting the pixels to the recording medium with a color having a predetermined recording gradation number by causing the recording element to perform the output operation. A reference value setting method referred to for correction of
For each of the plurality of recording element sections obtained by dividing the plurality of recording elements for each predetermined number of recording elements in the predetermined direction, the pixels output based on a predetermined input value by the recording elements included in the recording element section An output color value acquisition step of acquiring an output color value representing a color with a gradation number larger than the recording gradation number;
A reference value setting step for setting the reference value from which a correction input value corresponding to the predetermined input value can be acquired based on the output color value for each of the plurality of printing element sections;
Including
In the reference value setting step,
Based on the color value data of the color value acquired based on the output color value and corresponding to the corrected input value, a bit number reduction process for generating low bit number color value data having a smaller number of bits than the color value data. Performing each of the plurality of recording element sections in an order according to the arrangement order of the predetermined direction of the plurality of recording element sections,
In the bit number reduction process for the printing element classification except the head in the arrangement order, the color value of the color value data and the color value of the generated low bit number color value data in the bit number reduction process up to the previous stage Acquire the accumulated value of the error value caused by the difference, and generate low-bit number color value data in which the color value is adjusted based on the accumulated value,
The reference value is set based on the generated low bit number color value data.

According to a second aspect of the present invention, in the reference value setting method according to the first aspect,
The predetermined number is one.

According to a third aspect of the present invention, in the reference value setting method according to the first aspect,
The predetermined number is two or more.

According to a fourth aspect of the present invention, in the reference value setting method according to the third aspect,
The color value corresponding to the correction input value corresponds to a value obtained by averaging the color values corresponding to the correction input values for each of two or more recording elements included in each of the plurality of recording element sections.

According to a fifth aspect of the present invention, in the reference value setting method according to any one of the first to fourth aspects,
In the output color value acquisition step, for each of the plurality of recording element sections, the output color value of the recording gradation number is acquired based on the input value of the recording gradation number,
In the reference value setting step, low bit number color value data of the recording gradation number is generated based on the color value data of the recording gradation number corresponding to each of the plurality of recording element sections, and the plurality of recording gradation values is generated. For each of the element classifications, the reference value capable of acquiring a correction input value corresponding to the input value of the recording gradation number is set.

According to a sixth aspect of the present invention, in the method for setting a reference value according to any one of the first to fourth aspects,
In the output color value obtaining step, for each of the plurality of recording element sections, the predetermined number of gradations is determined based on an input value of a predetermined number of gradations corresponding to a part of the gradations of the recording gradation number. Obtaining the output color value;
In the reference value setting step, low bit number color value data of the predetermined gradation number is generated based on the color value data of the predetermined gradation number corresponding to each of the plurality of recording element sections, and the plurality of recording elements For each element section, the reference value that can obtain a corrected input value corresponding to the input value of the predetermined number of gradations is set.

In order to achieve the above object, an information processing apparatus according to claim 7
A plurality of recording elements that are provided at different positions in a predetermined direction and that each perform an output operation for outputting colored pixels to a recording medium, and the plurality of recording elements based on a corrected input value obtained by correcting an input value The input value in the image recording apparatus, comprising: a recording control unit configured to record the image by outputting the pixels to the recording medium with a color having a predetermined recording gradation number by causing the recording element to perform the output operation. An information processing apparatus for setting a reference value referred to for correction of
For each of the plurality of recording element sections obtained by dividing the plurality of recording elements for each predetermined number of recording elements in the predetermined direction, the pixels output based on a predetermined input value by the recording elements included in the recording element section Output color value acquisition means for acquiring an output color value representing a color with a gradation number larger than the recording gradation number;
Reference value setting means for setting the reference value capable of acquiring a corrected input value corresponding to the predetermined input value based on the output color value for each of the plurality of printing element sections;
With
The reference value setting means includes
Based on the color value data of the color value acquired based on the output color value and corresponding to the corrected input value, a bit number reduction process for generating low bit number color value data having a smaller number of bits than the color value data. Performing each of the plurality of recording element sections in an order according to the arrangement order of the predetermined direction of the plurality of recording element sections,
In the bit number reduction process for the printing element classification except the head in the arrangement order, the color value of the color value data and the color value of the generated low bit number color value data in the bit number reduction process up to the previous stage Acquire the accumulated value of the error value caused by the difference, and generate low-bit number color value data in which the color value is adjusted based on the accumulated value,
The reference value is set based on the generated low bit number color value data.

In order to achieve the above object, the invention of the image recording apparatus according to claim 8 provides:
An information processing apparatus according to claim 7;
A plurality of recording elements that are provided at different positions in a predetermined direction and each perform an output operation for outputting colored pixels to a recording medium;
A storage unit for storing reference data in which reference values set by the information processing apparatus are arranged;
Based on the reference data stored in the storage unit, an input value is corrected to a corrected input value, and the output operation is performed by each of the plurality of recording elements based on the corrected input value, whereby predetermined recording is performed. Recording control means for recording an image by outputting pixels to a recording medium with colors of the number of gradations;
Is provided.

According to the present invention, there is an effect that it is possible to set a reference value that can more reliably suppress a decrease in the image quality of a recorded image while suppressing an increase in data amount.

It is a figure which shows schematic structure of an inkjet recording device. It is a schematic diagram which shows the structure of a head unit. It is a block diagram which shows the main function structures of an inkjet recording device. It is a figure which shows the example of an output color value table. It is a figure explaining the example of the content of a correction table. It is a figure explaining the example of the content of a correction table. It is a figure which shows the test chart used for the production | generation of a correction table. It is a figure which expands and shows a part of test chart. It is a figure explaining the color nonuniformity reduction effect by a correction table. It is a figure explaining the color nonuniformity reduction effect by a correction table. It is a flowchart which shows the control procedure of a correction table production | generation process. It is a flowchart which shows the control procedure of a reference value setting process. It is a flowchart which shows the control procedure of an image recording process. It is a figure which shows the example of the content of the correction table which concerns on the modification 1. FIG. 10 is a flowchart illustrating a control procedure of reference value setting processing according to Modification 1. It is a figure which shows the example of the content of the correction table which concerns on the modification 2. FIG. 10 is a flowchart showing a control procedure of reference value setting processing according to Modification 2. It is a figure which shows the other example of content of a correction table.

Hereinafter, embodiments of a reference value setting method, an information processing apparatus, and an image recording apparatus according to the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a schematic configuration of the ink jet recording apparatus 100.
The ink jet recording apparatus 100 (image recording apparatus) includes a recording apparatus 1 that records an image on a recording medium P, and a process for generating various setting data used for setting operation control in the recording apparatus 1 according to an input operation by a user. And an information processing device 2 for performing

The recording apparatus 1 includes a paper feeding unit 10, an image forming unit 20, a paper discharge unit 30, and a control unit 40. Under the control of the control unit 40, the recording apparatus 1 conveys the recording medium P stored in the paper feeding unit 10 to the image forming unit 20, and the image forming unit 20 ejects ink onto the recording medium P to form an image. The recording medium P on which recording is performed and an image is recorded is conveyed to the paper discharge unit 30. Specifically, the recording apparatus 1 records the recording medium P with a predetermined number of recording gradations (256 in this embodiment) for each of the four colors of yellow (Y), magenta (M), cyan (C), and black (K). A color image is recorded on the recording medium P by overlapping and outputting the color on the recording medium P. As the recording medium P, in addition to paper such as plain paper and coated paper, various media capable of fixing ink landed on the surface, such as cloth or sheet-like resin, can be used.

The paper feed unit 10 includes a paper feed tray 11 that stores the recording medium P, and a medium supply unit 12 that conveys and supplies the recording medium P from the paper feed tray 11 to the image forming unit 20. The medium supply unit 12 includes a ring-shaped belt supported on the inside by two rollers, and the recording medium P is removed from the paper feed tray 11 by rotating the roller while the recording medium P is placed on the belt. It is conveyed to the image forming unit 20.

The image forming unit 20 includes a transport unit 21, a delivery unit 22, a heating unit 23, a head unit 24, a fixing unit 25, an image reading unit 26, a delivery unit 27, and the like.

The transport unit 21 holds the recording medium P placed on the transport surface of the cylindrical transport drum 211, and the transport drum 211 has a rotating shaft (cylindrical shaft) extending in the X direction perpendicular to the drawing in FIG. The recording medium P on the transport drum 211 is transported in the transport direction along the transport surface by rotating around and rotating around the center. The transport drum 211 includes a claw portion and a suction portion (not shown) for holding the recording medium P on the transport surface. The recording medium P is held on the conveyance surface by the end being pressed by the claw portion and sucked to the conveyance surface by the intake portion.

The delivery unit 22 is provided at a position between the medium supply unit 12 and the conveyance unit 21 of the paper supply unit 10, and picks up one end of the recording medium P conveyed from the medium supply unit 12 by the swing arm unit 221. Then, it is delivered to the transport unit 21 via the delivery drum 222.

The heating unit 23 is provided between the arrangement position of the delivery drum 222 and the arrangement position of the head unit 24, and the recording medium P conveyed by the conveyance unit 21 has a temperature within a predetermined temperature range. Heat P. The heating unit 23 includes, for example, an infrared heater, and energizes the infrared heater based on a control signal supplied from the control unit 40 (FIG. 3) to cause the infrared heater to generate heat.

The head unit 24 is disposed on the recording medium P from a nozzle opening provided on an ink discharge surface facing the conveyance surface of the conveyance drum 211 at an appropriate timing according to the rotation of the conveyance drum 211 on which the recording medium P is held. The image is recorded by ejecting ink. The head unit 24 is disposed such that the ink discharge surface and the transport surface are separated by a predetermined distance. In the ink jet recording apparatus 100 according to the present embodiment, four head units 24 respectively corresponding to four color inks Y, M, C, and K have colors Y, M, C, and K from the upstream side in the conveyance direction of the recording medium P. Are arranged at predetermined intervals in this order.

FIG. 2 is a schematic diagram showing the configuration of the head unit 24. FIG. 2 is a plan view of the entire head unit 24 as viewed from the side facing the conveyance surface of the conveyance drum 211.
In the present embodiment, the head unit 24 includes 16 recording heads 242 in which a plurality of recording elements 243 that perform ink discharging operation (output operation) for discharging ink are arranged in the X direction (predetermined direction). Each of the recording elements 243 includes a pressure chamber for storing ink, a piezoelectric element provided on a wall surface of the pressure chamber, an electrode for applying a voltage to the piezoelectric element to generate an electric field, and a pressure communicating with the pressure chamber. And a nozzle for ejecting ink in the room. When a drive signal for deforming the piezoelectric element is input to the recording element 243, the pressure chamber is deformed by the deformation of the piezoelectric element and the pressure in the pressure chamber is changed, and ink is ejected from the nozzle communicating with the pressure chamber. . The amount of ink ejected from the nozzle can be adjusted by changing the amplitude of the voltage of the drive signal. FIG. 2 shows the positions of the ink discharge ports of the nozzles that are the constituent elements of the recording element 243. The arrangement direction of the recording elements 243 in each recording head 242 is not limited to the X direction, and may be a direction that intersects the conveyance direction (Y direction) of the recording medium P at an angle other than a right angle.

In the head unit 24, two 16 recording heads 242 are combined, and eight head modules 242M each configured by the combination of the recording heads 242 are provided. In each head module 242M, the two recording heads 242 are arranged in such a positional relationship that the nozzles of the two recording heads 242 are alternately arranged in the X direction. By arranging the recording elements 243 in this manner, each head module 242M can perform recording at a resolution of 1200 dpi (dot per inch) in the width direction.
Further, the eight head modules 242M have a positional relationship in which the recording elements 243 are arranged over the recording width of the image on the recording medium P in the X direction so that the arrangement ranges in the width direction partially overlap each other. It is arranged in a staggered pattern to constitute a line head. In a portion where the arrangement ranges of the recording elements 243 in the X direction overlap between adjacent head modules, ink is ejected by the recording elements 243 of one of the head modules 242M at each position in the X direction.

Each recording element 243 used for recording an image provided in the head unit 24 is specified by an array number (nozzle number: 0 to n _end ) according to the array order of the nozzles in the X direction of the recording element 243. In this embodiment, the number N (= n _end +1) (number of nozzles) of the recording elements 243 used for image recording is about 28000.

The head unit 24 is used at a fixed position during image recording, and sequentially ejects ink at different intervals (conveyance direction intervals) to different positions in the conveyance direction according to the conveyance of the recording medium P. Record an image using the single pass method.
The configuration of the head unit 24 is not limited to the above configuration as long as the plurality of recording elements 243 are provided at different positions in the X direction. For example, instead of the head module 242M, the recording heads 242 may be arranged in a staggered pattern. Further, the head unit 24 may be configured by a single recording head 242.

As the ink ejected from the nozzles of the recording element 243, ink having a property of changing in phase to a gel or sol depending on the temperature and being cured by irradiating energy rays such as ultraviolet rays is used. In the present embodiment, ink that is gel-like at room temperature and becomes sol-like when heated is used. The head unit 24 includes an ink heating unit (not shown) that heats the ink stored in the head unit 24. The ink heating unit operates under the control of the control unit 40, and supplies the ink to a sol-like temperature. Heat. The recording head 242 discharges ink that has been heated to form a sol.

The fixing unit 25 has an energy beam irradiation unit arranged over the width of the conveyance unit 21 in the X direction, and the recording medium P placed on the conveyance unit 21 receives ultraviolet rays or the like from the energy beam irradiation unit. The ink ejected on the recording medium P is cured and fixed by irradiating energy rays. The energy ray irradiating unit of the fixing unit 25 is arranged to face the conveying surface between the arrangement position of the head unit 24 and the arrangement position of the delivery drum 271 of the delivery unit 27 in the conveying direction.

The image reading unit 26 is arranged so as to be able to read the surface of the recording medium P on the conveyance surface at a position between the ink fixing position by the fixing unit 25 and the arrangement position of the transfer drum 271 in the conveyance direction. The image recorded on the recording medium P conveyed by the above is read in a predetermined reading range, and imaging data of the image is output.
In the present embodiment, the image reading unit 26 includes a light source that emits light to the recording medium P conveyed by the conveying drum 211 and an image sensor that detects the intensity of reflected light of the light incident on the recording medium P. Line sensors arranged in a direction. Specifically, in the line sensor, three rows of image pickup devices each including image pickup devices arranged in the width direction are provided, and R (red), G (green), and B of the incident light are provided by the image pickup devices of each image pickup device row. A signal corresponding to the intensity of the wavelength component of (blue) is output. Imaging elements corresponding to R, G, and B are, for example, R, G, or B in a light receiving portion of a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor that includes a photodiode as a photoelectric conversion element. A filter in which a color filter that transmits light having a wavelength component of is arranged can be used. The reading resolution of each image sensor of the line sensor is, for example, 600 dpi in the width direction. That is, this image sensor may acquire an image with a resolution lower than the resolution corresponding to the nozzle arrangement interval.
The signal output from the line sensor is subjected to current-voltage conversion, amplification, noise removal, analog-digital conversion, and the like in an analog front end (not shown), and is output to the control unit 40 as imaging data indicating the luminance value of the read image.
Note that the configuration of the image reading unit 26 is not limited to this, and for example, an area sensor may be used instead of the line sensor.

The delivery unit 27 includes a belt loop 272 having an annular belt supported on the inside by two rollers, and a cylindrical delivery drum 271 that delivers the recording medium P from the transport unit 21 to the belt loop 272. The recording medium P transferred from the transport unit 21 onto the belt loop 272 by the transfer drum 271 is transported by the belt loop 272 and sent to the paper discharge unit 30.

The paper discharge unit 30 includes a plate-shaped paper discharge tray 31 on which the recording medium P sent out from the image forming unit 20 by the delivery unit 27 is placed.

FIG. 3 is a block diagram showing the main functional configuration of the inkjet recording apparatus 100.
The recording apparatus 1 of the inkjet recording apparatus 100 includes a heating unit 23, a head unit 24 having a recording head driving unit 241 and a recording head 242, a fixing unit 25, an image reading unit 26, and a control unit 40 (recording control unit). A transport driving unit 51, an image processing unit 52, an input / output interface 53, a bus 54, and the like.

The recording head driving unit 241 supplies pixel signals of image data from the nozzles of the recording head 242 by supplying a driving signal for deforming the piezoelectric element according to the image data to the recording element 243 of the recording head 242 at an appropriate timing. An amount of ink corresponding to the value is ejected.

The control unit 40 includes a CPU 41 (Central Processing Unit), a RAM 42 (Random Access Memory), a ROM 43 (Read Only Memory), and a storage unit 44, and performs overall control of the entire operation of the recording apparatus 1.

The CPU 41 reads various control programs and setting data stored in the ROM 43, stores them in the RAM 42, and executes the programs to perform various arithmetic processes.

The RAM 42 provides a working memory space to the CPU 41 and stores temporary data. The RAM 42 may include a nonvolatile memory.

The ROM 43 stores various control programs executed by the CPU 41, setting data, and the like. Instead of the ROM 43, a rewritable nonvolatile memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory) or a flash memory may be used.

In the storage unit 44, a print job input from the information processing apparatus 2 via the input / output interface 53, image data of an image recorded by the print job, imaging data output from the image reading unit 26, and a description will be given later. Test chart image data and the like are stored. In addition, the storage unit 44 stores a correction table 44a as reference data that is referred to in correction of image data to be described later. As the storage unit 44, for example, an HDD (Hard Disk Drive) is used, and a DRAM (Dynamic Random Access Memory) or the like may be used in combination.

The transport drive unit 51 supplies a drive signal to a transport drum motor provided on the transport drum 211 based on a control signal supplied from the control unit 40 to rotate the transport drum 211 at a predetermined speed and timing. Further, the transport drive unit 51 supplies a drive signal to a motor for operating the medium supply unit 12, the delivery unit 22, and the delivery unit 27 based on the control signal supplied from the control unit 40, and the recording medium P Is supplied to the transport unit 21 and discharged from the transport unit 21.

The image processing unit 52 performs predetermined image processing on the image data stored in the storage unit 44 and causes the storage unit 44 to store the obtained image data. This image processing includes color conversion processing, gradation correction processing, halftone processing, and the like in addition to correction processing for correcting image data by applying the correction table 44a to the image data.

The input / output interface 53 is connected to the input / output interface 72 of the information processing apparatus 2 and mediates transmission / reception of data between the control unit 40 and the control unit 60 of the information processing apparatus 2. The input / output interface 53 is configured by any one of various serial interfaces, various parallel interfaces, or a combination thereof.

The bus 54 is a path for transmitting and receiving signals between the control unit 40 and other components.

The information processing apparatus 2 of the inkjet recording apparatus 100 includes a control unit 60 (output color value acquisition unit, reference value setting unit), an operation display unit 71, an input / output interface 72, a bus 73, and the like. The information processing apparatus 2 is configured by a personal computer such as a desktop type or a notebook type.

The control unit 60 includes a CPU 61, a RAM 62, a ROM 63, and a storage unit 64.

The CPU 61 reads various control programs and setting data stored in the ROM 63, stores them in the RAM 62, and executes the programs to perform various arithmetic processes.

The RAM 62 provides a working memory space to the CPU 61 and stores temporary data. The RAM 62 may include a nonvolatile memory.

The ROM 63 stores various control programs executed by the CPU 61, setting data, and the like. Instead of the ROM 63, a rewritable nonvolatile memory such as an EEPROM or a flash memory may be used.

The storage unit 64 stores PDL (Page Description Language) data relating to an image to be recorded input from the external device 200 via the input / output interface 72, imaging data of a test chart generated in the recording device 1, and the like. Is done. As the storage unit 64, for example, an HDD is used, and a DRAM or the like may be used in combination.

The control unit 60 having such a configuration controls the overall operation of the information processing apparatus 2. For example, the control unit 60 converts the PDL data input from the external device 200 into a raster format and outputs it to the control unit 40 of the recording apparatus 1. Further, the control unit 60 generates a correction table 44 a based on the imaging data of a predetermined test chart input from the recording device 1 and outputs the correction table 44 a to the control unit 40 of the recording device 1. A method for generating the correction table 44a will be described in detail later.

The operation display unit 71 includes a display device such as a liquid crystal display or an organic EL display, and an input device such as a keyboard, a mouse, and a touch panel arranged on the screen of the display device. The operation display unit 71 displays various information on the display device, converts a user input operation to the input device into an operation signal, and outputs the operation signal to the control unit 60.

The input / output interface 72 mediates data transmission / reception between the control unit 60 and the control unit 40 of the recording apparatus 1 and between the control unit 60 and the external device 200. The input / output interface 72 is configured by any one of various serial interfaces, various parallel interfaces, or a combination thereof, for example.

The bus 73 is a path for transmitting and receiving signals between the control unit 60 and other components.

The external device 200 is a personal computer, for example, and supplies PDL data or the like to the control unit 60 via the input / output interface 72.

Next, an image recording operation in the inkjet recording apparatus 100 and image data correction using the correction table 44a performed in the recording operation will be described.
In the inkjet recording apparatus 100, when a print job and raster image data of an image recorded by the print job are stored in the storage unit 44 of the recording apparatus 1, an image recording operation according to the print job is performed in the recording apparatus 1. Is started. Here, the image data related to the print job of the present embodiment is data in which 8-bit (that is, 256 gradations from 0 to 255) input values (color values) are set in each pixel data. In the image recording operation by the ink jet recording apparatus 100, pixels of a color corresponding to the input value of the pixel data are output on the recording medium P by the ink ejection operation of the recording element 243 according to each pixel data included in the image data. An image in which a large number of pixels are combined is recorded on the recording medium P. In the ink jet recording apparatus 100 of the present embodiment, as will be described later, ink is ejected from the recording elements 243 with a distribution corresponding to pseudo halftone image data obtained by halftone processing 256-tone image data. As a result, pixels of a color corresponding to the pixel data of the original image data are formed on the recording medium P by the pseudo halftone method. For this reason, the pixels described above do not necessarily correspond to individual ink droplets ejected from the recording element 243 and landed on the recording medium P.

In the recording apparatus 1, based on the same input value of image data due to a shift in applied voltage of the recording head driving unit 241, variation in characteristics of a load (piezoelectric element) driven by the recording head driving unit 241, and the like. Therefore, even if each recording element 243 tries to output pixels with the same color value, the color values of the output pixel colors (hereinafter also simply referred to as output colors) vary.
FIG. 4A is an output color value table in which the color value (output value) of the pixel color actually output by ink ejection of the recording element 243 of each nozzle number according to the input value of 256 gradations is represented by 16 bits. It is a figure which shows an example. In order to make it easy to understand the correspondence between the color values in FIG. 4A and the input values, a lightness formula using the target lightness value L * of each color (b * for yellow or XYZ-Z value instead of XYZ-Y value). It is normalized by the formula that substitutes The notation is a floating point notation obtained by dividing 0 to 65535 by 257. In this example, the density is almost stable in the vicinity of the target brightness. If the target brightness is reduced depending on the position, adjustment or driving can be performed by gradation correction processing described below so that the target brightness value (darkness) is satisfied even in a thin nozzle region in the input range of 8-bit input value 0 to 255. If the voltage is adjusted or applied, the following can be handled similarly. In FIG. 4A, for example, it can be seen that the color value of the color output when the input value is the thirteenth gradation does not necessarily become the thirteenth gradation accurately. Such variations in color values cause streak-like color unevenness in the recorded image, which causes a reduction in image quality. Therefore, in the image recording operation in the recording apparatus 1, in order to output the pixel of the color of the input value given by the image data in an accurate color, the image data is first corrected by applying a correction table to the image data. Corrected image data is generated, and an image is recorded based on the corrected image data.

FIG. 4B is a diagram showing an example of the contents of a correction table generated based on the output color value table of FIG. 4A.
In this correction table, for each of the N recording elements provided in the

head unit

24, 256 gradations from the minimum color value (0) to the maximum color value (255) of the color corresponding to the head unit 24 are obtained. Reference values corresponding to each of the color values (image data input values) are individually set. This reference value is a value that represents a correction value (correction input value) of the input value for matching the color value of the color output from each recording element 243 with the color value of the color of the input value in 16 bits. As described above, the notation is a floating-point notation obtained by dividing 0 to 65535 by 257, and the actual 16-bit reference value is a value obtained by multiplying the value in the table by 257.
For example, the reference value corresponding to the input value of the thirteenth gradation for the printing element 243 with the nozzle number 1 is 12.1. This reference value is obtained by calculating an input value at which the 13th gradation output is actually performed by the recording element 243 having the nozzle number 1 based on the output color value table of FIG. 4A.

According to the correction table in which 16-bit correction input values as shown in FIG. 4B are arranged as reference values, an accurate correction input value can be obtained. However, since the number of bits is large and the amount of data is large, storage is performed. There is a problem that the storage capacity of the unit 44 is compressed and the circuit configuration necessary for the correction processing using the correction table becomes complicated.
Therefore, in the present embodiment, by reducing the number of bits of each correction input value in the correction table of FIG. 4B, a correction table 44a in which 8-bit correction input values as shown in FIG. Generate. The correction table 44a after the bit reduction is stored in the storage unit 44 and is used for image data correction processing. In the example of FIG. 5, for example, when the color value related to the input value of the image data for the printing element 243 having the nozzle number 1 is the 13th gradation, the input value of the image data corresponds in the correction table 44a. Based on the reference value to be corrected to the 12th gradation. The correction table 44a is provided corresponding to each of the four head units 24 (that is, corresponding to each color of Y, M, C, and K), and in FIG. A correction table 44a is shown. A method of generating the correction table 44a of FIG. 5 by reducing the bit of the correction table of FIG. 4B will be described in detail later.

In this manner, the input value of the image data is corrected to a correction input value set in advance based on the actual color output result by each recording element 243, and ink is ejected by the recording element 243 based on this correction input value. By doing so, the color value indicated by the input value of the image data and the color value of the color of the pixel output by the ink ejection from the recording element 243 can be matched.
By correcting the input value of the image data for each of the recording elements 243 from the nozzle numbers 0 to n _end to the corrected input value corresponding to the input value, the input value of the entire image data is corrected, and corrected image data is generated. The Also, corrected image data is generated for each color image data of Y, M, C, and K, respectively.

When the corrected image data is generated, the corrected image data is subjected to image processing such as gradation correction processing (gamma correction or the like) as necessary, and then the 8-bit image data for each pixel is converted to 1 bit for each pixel ( Halftone processing is performed for conversion to pseudo-halftone image data of (2 gradations). The method of halftone processing is not particularly limited, but a random dither method that binarizes gradation values according to a random threshold value in each pixel, each pixel according to each of the threshold values arranged in a matrix For example, a systematic dither method for binarizing the tone values of the pixels, an error diffusion method for allocating an error generated in the binarization processing of the tone values of each pixel to surrounding pixels, or the like can be used.
Then, based on the Y, M, C, and K image data after the halftone process, ink is ejected onto the recording medium P by the recording elements 243 of the four head units 24 to record an image.

Next, a method for generating the correction table 44a will be described. In the present embodiment, the correction table 44a is generated in the information processing apparatus 2.
The correction table 44 a is generated when the inkjet recording apparatus 100 (or recording apparatus 1) is produced or shipped, and when the head unit 24 is replaced. Further, when a predetermined period has passed since the most recent generation of the correction table 44a (for example, when image recording is performed on a predetermined number of recording media P), the correction table 44a is generated and the existing correction table 44a is overwritten. Also good.

In the generation of the correction table 44a, first, an output color value table (FIG. 4A) indicating the color values of the colors actually output according to the input values of 256 gradations is generated by each recording element 243, and the output color value Based on the table, the reference value (FIG. 5) of the correction table 44a is set.
Among these, in the generation of the output color value table, first, a predetermined test chart is recorded on the recording medium P by the head unit 24 of the recording apparatus 1, the test chart is read by the image reading unit 26, and imaging data of the test chart is obtained. Generated.

FIG. 6A is a diagram illustrating an example of the test chart G. FIG. 6B is an enlarged view of a part of the test chart G in FIG. 6A.
As shown in FIG. 6A, the test chart G shows the range from the minimum color value (0) to the maximum color value (255) among the color values of 256 tones that can be recorded by the head unit 24. It consists of color bands G0 to G16 having 17 color values divided equally. Among these, in the color band G0, ink is not ejected and white is represented by the ground color of the recording medium P. Each of the color bands G1 to G16 is recorded by ejecting ink based on image data of the same input value by the recording elements 243 of the nozzle numbers 0 to n _end of the head unit 24. Accordingly, the color bands G1 to G16 are recorded in a state where the variation in the color value of the output color by the recording element 243 described above is reflected. The width in the X direction of each of the color bands G0 to G16 corresponds to the arrangement range of the recording elements 243 of the head unit 24. The width r (FIG. 6B) in the Y direction of each of the color bands G0 to G16 is not particularly limited, but is set to a size that allows the image reading unit 26 to acquire imaging data of 256 pixels or 512 pixels.

When the imaging data of the test chart G is acquired, the luminance value at each pixel of the imaging data is converted into a colorimetric value gradation value (hereinafter referred to as a colorimetric gradation value). The magnitude of the luminance value acquired by the image sensor of the image reading unit 26 is not necessarily proportional to the color density (density gradation) perceived by human vision. Therefore, a conversion table that converts the luminance value acquired by the image sensor into colorimetric gradation values that are equivalent to human visual sensitivity is prepared in advance, and the luminance value is measured by applying this conversion table to the imaging data. Convert to color gradation value.
Specifically, with respect to the imaging data of the test chart G of M, C, and K, the luminance value by the G imaging element is associated with the L * component of the colorimetric value in the L * a * b * color system. By applying the conversion table thus obtained, the luminance value is converted into a colorimetric gradation value of 8 bits (256 gradations). For the image data of the Y test chart G, an index (for example, b) that changes in correspondence with the luminance value of B in the luminance value of the B image sensor and the colorimetric value in the L * a * b * color system. By applying a conversion table associated with * component), the luminance value is converted into an 8-bit colorimetric gradation value.

Subsequently, a 16-bit colorimetric gradation value distribution in the X direction in each of the color bands G1 to G16 of the test chart G is acquired based on the 8-bit imaging data converted into the colorimetric gradation values. Here, for each of the color bands G1 to G16, 256 different 8-bit colorimetric gradation values are added to each other across the width r in the Y direction shown in FIG. Get the colorimetric gradation value of the bit. Instead of this, the number of bits of colorimetric gradation values and the number of additions may be adjusted so that the number of bits after addition is 16 bits. For example, a colorimetric gradation value is acquired in 10 bits, and a 16-bit colorimetric gradation value is acquired by adding 64 10-bit colorimetric gradation values over the width r of the color band G0 to G16. May be.

For each of the color bands G1 to G16, when a data array in the X direction of 16-bit colorimetric gradation values is acquired, a predetermined filtering process is performed on the data array. Specifically, a median filter is applied to remove streak components in units of recording elements. Further, by applying a low-pass filter, the frequency components higher than the frequency band are removed while leaving the color unevenness of the desired frequency band to be corrected by the correction table 44a. In this embodiment, as will be described later, since the correction table 44a is generated so that the average chromaticity in the range of about 10 to 100 nozzles is adjusted, high-frequency component noise of less than 10 nozzles is removed by a low-pass filter. To do.

Note that the process of converting the luminance value of the imaging data into the colorimetric gradation value may be performed at a timing different from the above. For example, for each of the color bands G1 to G16, by first adding the luminance value of the imaging data at each position in the X direction with respect to the Y direction to acquire the 16-bit luminance value distribution in the X direction, The value may be converted into a colorimetric gradation value. Alternatively, the luminance value may be converted into a colorimetric gradation value after the above filtering process is further performed on the data array of the 16-bit luminance value distribution in the X direction.

Subsequently, for each of the color bands G1 to G16, the number of pixels in the data array of colorimetric gradation values (in the X direction) is converted from the number of image sensors in the image reading unit 26 to the number of nozzles (N) in the head unit 24. To do. That is, the distribution of the colorimetric gradation values in the data array based on the correspondence between the arrangement position of the image sensor in the X direction of the image reading unit 26 and the arrangement position of the nozzle of each recording element 243 in the head unit 24. From this, a data array composed of 16-bit colorimetric gradation value data corresponding to the recording elements 243 of the respective nozzle numbers 0 to n _end is generated. This conversion process may be performed at an earlier stage such as before the conversion process from the luminance value to the colorimetric gradation value described above.

Subsequently, the 16 colorimetric gradation values corresponding to the color bands G1 to G16 are converted into gradations of the recording gradation number by the recording apparatus 1, that is, 256 gradations. This conversion can be performed by linearly interpolating colorimetric gradation values between adjacent gradations.

Through such a series of processing, an output color value (that is, an input value) represented by a 16-bit colorimetric gradation value corresponding to an input value of 256 gradations for each of the N recording elements 243. (Color value output by the recording element 243) is acquired in response to the output color value data. The N × 256 16-bit output color value data forms the output color value table of FIG. 4A. In each output color value data of the output color value table, the colorimetric gradation value is represented by 65536 gradations, and the number of gradations is larger than the recording gradation number (256 gradations) of the inkjet recording apparatus 100. Yes.

Next, on the basis of the output color value data in the output color value table, 16-bit corrected input values (refer to reference values) corresponding to the 256 gradation input values for each of the N printing elements 243 by the above-described method. Value) and a 16-bit correction table (FIG. 4B) is generated.

Next, a bit number reduction process for reducing the number of bits from 16 bits to 8 bits is performed on each of the corrected input value data in the obtained 16-bit correction table. Hereinafter, 16-bit correction input value data before the bit number reduction process is referred to as high bit number correction input value data (color value data), and the correction input value data converted into 8 bits by the bit number reduction process is represented by a low bit number. This is referred to as corrected input value data (low bit number color value data). The data table in which the low bit number correction input value data is arranged is the correction table 44a shown in FIG. Hereinafter, the correction table of FIG. 4B is referred to as a high bit number correction table, and is distinguished from the correction table 44a of FIG.

The reduction of the number of bits of the high bit number correction input value data is performed in units of a data array composed of N high bit number correction input value data arranged in the recording element arrangement direction in the high bit number correction table. The number-of-bits reduction processing for each of the N high-bit number correction input value data in each data array is performed in the order according to the arrangement order of the N recording elements 243 in the X direction, that is, in the order of the nozzle numbers of the recording elements 243. Is called.
In the bit number reduction process, the bit number is reduced by expressing the quotient obtained by dividing the high bit number corrected input value data by 257 with 8 bits. This process corresponds to a process of extracting the upper 8 bits of the high bit number corrected input value data.

Also, in each bit number reduction process performed in the order according to the arrangement order, it is obtained by subtracting the color value of the generated 8-bit low bit number corrected input value data from the color value of the high bit number corrected input value data. The calculated difference is calculated as an error value, and in the bit number reduction process for the recording element 243 excluding the head, the color value is adjusted based on the accumulated error value generated in the previous bit number reduction process. Low bit number corrected input value data is generated.
Specifically, in each bit number reduction process, the calculated error value is carried over (carried over) to the next bit number reduction process. In the bit number reduction process at the next stage, the accumulated value of the inherited error value is changed from the color value of the high bit number correction input value data in the bit number reduction process at the stage to the low bit number correction input value before adjustment. When the value obtained by adding the difference value obtained by subtracting the data exceeds a predetermined reference range (in this case, the above value when the color value is expressed in 16 bits is 128 or more), the generated low 1 is added to the bit number correction input value data (in 8-bit notation). In this way, in the bit number reduction process at the stage where 1 is added to the low bit number correction input value data, the adjusted low bit number correction input value data has a higher value than the color value of the high bit number correction input value data. Since the color value is larger, the final error value at the stage is a negative value. Specifically, the error value at this stage is further increased to 257 (low) from the difference value obtained by subtracting the color value of the low bit number corrected input value data before adjustment from the color value of the high bit number corrected input value data. This is a value obtained by subtracting the equivalent value in the adjustment of the bit number correction input value data. Then, the added value of this error value and the accumulated error value up to the previous stage is taken over by the bit number reduction process in the next stage.
In the following, the accumulated error value taken over to the next stage is also referred to as a gradation expression error.

Such bit number reduction processing is performed for each data array corresponding to each of 256 gradation input values in the high bit number correction table. As a result, a correction table 44a in which 8-bit low bit number correction input value data respectively corresponding to 256 gradation input values is arranged for each of the N recording elements 243 is generated. The generated correction table 44a is stored in the storage unit 44 of the recording apparatus 1.

FIG. 7A shows the color value distribution of the high bit number correction input value data D16 in the high bit number correction table and the color value distribution of the low bit number correction input value data D8 generated by the bit number reduction processing of this embodiment. FIG. 7B shows the same color value distribution of the high bit number corrected input value data D16 as in FIG. 7A and the color value distribution of the low bit number corrected input value data D8a obtained by the conventional bit number reduction processing. FIG. In the conventional example of FIG. 7B, a simple process is used in which the color value of the high bit number correction input value data D <b> 16 is rounded off to the next decimal point and the error value due to the bit number reduction is not transferred to the next stage. The high bit number correction input value data D16 in FIGS. 7A and 7B indicates the color value of the correction input value data for the input value of the 13th gradation among the input values of 256 gradations. The high bit number correction input value data D16 is depicted in a simplified manner so that it changes in four steps between the gradations of the color value related to the input value, but in actuality, in 256 steps between the gradations. Change.

In the conventional bit number reduction process shown in FIG. 7B, the color value of the low bit number corrected input value data D8a is changed only in the section where the color value of the high bit number corrected input value data D16 is larger than 13.5. The transition to 14 gradations is constant at the 13th gradation in other sections. In such a conventional bit number reduction process, there is a problem that the chromaticity of the high bit number corrected input value data D16 and the chromaticity of the low bit number corrected input value data D8a are different in a wide range in the nozzle arrangement direction. Further, since the color value transition frequency of the low bit number correction input value data D8a in the nozzle arrangement direction is small, in the correction of the input value using the correction table using the low bit number correction input value data D8a as a reference value, There is a problem that the portion where the correction input value transitions is easily visually recognized as uneven color.

On the other hand, according to the bit number reduction process in the present embodiment in which the color value difference before and after the bit number reduction process is taken over to the next stage, as shown in FIG. 7A, the high bit number correction input value data D16 Depending on the accumulated value of the difference between the color value and the color value of the input value (13th gradation), the color value of the low bit number corrected input value data D8 is between the 13th gradation and the 14th gradation. Transition frequently. As a result, the average chromaticity of the low bit number correction input value data D8 in the range of about 10 to 100 nozzles substantially matches the average chromaticity of the high bit number correction input value data D16 in the range. Moreover, in the correction table 44a using the low bit number correction input value data D8 as a reference value, the correction input value transition frequency is high, and therefore, the effect that the portion where the correction input value transitions is difficult to be visually recognized as color unevenness. Played.

Subsequently, a control procedure by the control unit 40 and the control unit 60 of the correction table generation process executed in the inkjet recording apparatus 100 will be described.

FIG. 8 is a flowchart showing the control procedure of the correction table generation process.
When the correction table generation process is started, the control unit 40 of the recording apparatus 1 causes the head unit 24 to record the test chart G on the recording medium P based on the image data of the test chart G (step S101). That is, the control unit 40 outputs a control signal to the conveyance driving unit 51 to operate the paper feeding unit 10, the delivery unit 22, and the conveyance unit 21 to place the recording medium P on the conveyance surface of the conveyance drum 211. Then, the conveyance drum 211 is rotated to convey the recording medium P. In addition, the control unit 40 causes the recording head driving unit 241 to supply the image data of the test chart G stored in the storage unit 44 to the recording head 242 at an appropriate timing according to the rotation of the transport drum 211, thereby the head unit. 24, ink is ejected onto the recording medium P to record the test chart G on the recording medium P.

The control unit 40 causes the image reading unit 26 to image the recorded test chart G (step S102). That is, the control unit 40 starts imaging by the image reading unit 26 at a timing when the test chart G on the recording medium P moves to an imaging position by the image reading unit 26 according to the rotation of the transport drum 211. The control unit 40 repeatedly acquires signals from the image sensor of the image reading unit 26 at predetermined time intervals, generates imaging data of the test chart G, and stores the data in the storage unit 44 and the storage unit 64 of the information processing device 2.

The control unit 60 of the information processing apparatus 2 applies a predetermined conversion table to the luminance value in each pixel of the imaging data of the test chart G to convert it into an 8-bit colorimetric gradation value (step S103). Further, the control unit 60 adds 256 8-bit colorimetric gradation values at 256 positions different from each other in the Y direction at each position in the X direction of the color bands G1 to G16 of the test chart G, thereby obtaining 16 in the X direction. A bit colorimetric gradation value distribution is acquired (step S104).

The control unit 60 performs predetermined smoothing processing such as a median filter and a low-pass filter on the data array in the X direction of the 16-bit colorimetric gradation values (step S105), and the 16-bit colorimetric gradation value data The number of pixels in the array is converted from the number of image sensors in the image reading unit 26 to the number of nozzles (N) in the head unit 24 (step S106). Then, the control unit 60 performs linear interpolation processing on the 16 gradation colorimetric gradation values corresponding to the color bands G1 to G16, thereby obtaining the 16 gradation colorimetric gradation values. The number of recorded gradations is converted to 256 gradations, that is, 256 gradations (step S107).
The control unit 60 performs colorimetric gradation values (output color values) respectively corresponding to the 256 gradation input values for each of the N recording elements 243 through the processing from step S101 to step S107. The output color value data is generated by the acquisition, and the output color value table in which N × 256 output color value data is arranged is stored in the storage unit 64 (output color value acquisition step).
When the process of step S107 ends, the control unit 60 executes a reference value setting process (step S108).

FIG. 9 is a flowchart showing the control procedure of the reference value setting process called in the correction table generation process.
When the reference value setting process is called and executed, the control unit 60 sets the variable “in” related to the color value of the input value, the variable “n” related to the nozzle number, and the variable “Error” related to the gradation expression error. ”, A two-dimensional 16-bit data array LUTin [in] [n] and an 8-bit data array LUTout [in] [n] with the input value in and the nozzle number n as variables are set.

When the reference value setting process is started, the control unit 60, based on the output color value data of the output color value table, for each of the

N recording elements

243, 16 bits corresponding to the input value of 256 gradations. Are calculated and stored in the data array LUTin [in] [n] (step S201).

The control unit 60 substitutes 0 for the input value in (step S202). Further, the control unit 60 determines whether or not the input value in is less than 256 (step S203), and if it is determined that the input value in is less than 256 (“YES” in step S203), the gradation expression error 0 is substituted into Error and nozzle number n (step S204).

The controller 60 determines whether the nozzle number n is equal to or less than the maximum nozzle number (n _end ) (step S205). When it is determined that the nozzle number n is equal to or less than n _end (“YES” in step S205), the control unit 60 adds the input value in and the predetermined 16-bit data (hereinafter referred to as “data16”). 16-bit correction input value data (LUTin [in] [n]) corresponding to the nozzle number n is substituted (step S206), and data 16 is set to 257 in predetermined 8-bit data (hereinafter referred to as “data8”). The divided quotient is substituted (step S207). The processing in step S207 corresponds to processing for extracting the lower 8 bits of data16 and lowering the bits.

The control unit 60 substitutes a value obtained by subtracting data8 × 257 from the sum of the current gradation expression error Error and data16 to the gradation expression error Error (step S208).

The control unit 60 determines whether or not the gradation expression error Error is 128 or more (step S209). If it is determined that the gradation expression error Error is 128 or more (“YES” in step S209), data8 is 255 or more. Is determined (step S210). When it is determined that data8 is 255 or more (“YES” in step S210), the controller 60 substitutes 255 for data8 (step S211), and when it is determined that data8 is less than 255. (“NO” in step S210), data8 + 1 is assigned to data8, and a value obtained by subtracting 257 from the current gradation expression error Error is assigned to the gradation expression error Error (step S212).

When the process of step S211 or step S212 ends, or when the gradation expression error Error is determined to be less than 128 in the process of step S209 (“NO” in step S209), the control unit 60 uses the input value. Data8 as low bit number correction input value data is stored in the 8-bit data array LUTout [in] [n] corresponding to in and nozzle number n (step S213). When the process of step S212 ends, the control unit 60 adds 1 to the nozzle number n (step S214), and returns the process to step S205.

If it is determined in step S205 that the nozzle number n is greater than n _end (“NO” in step S205), the control unit 60 adds 1 to the input value in (step S215), and performs the process. Return to step S203. By repeating the processing from step S203 to step S215, low-bit number correction input value data indicating the reference value of the correction table 44a is sequentially stored in the 8-bit data array LUTout [in] [n]. The processing from step S203 to step S215 corresponds to a reference value setting step.

When it is determined in the process of step S203 that the input value in is 256 or more (“NO” in step S203), the control unit 60 stores the low value stored in the 8-bit data array LUTout [in] [n]. A correction table 44a using the bit number correction input value data as a reference value is stored in the storage unit 44 of the recording apparatus 1, and the reference value setting process and the correction table generation process are terminated.

Next, a control procedure by the control unit 40 of the image recording process executed in the recording apparatus 1 will be described. The image recording process is executed when a print job and image data are input from the information processing apparatus 2 to the control unit 40 via the input / output interface 53.

FIG. 10 is a flowchart showing the control procedure of the image recording process.
When the image recording process is started, the control unit 40 generates the corrected image data by applying the correction table 44a to the image data of the image to be recorded (step S301). That is, the control unit 40 corrects the input value (color value) of the pixel corresponding to each recording element 243 in the image data to the reference value associated with the input value and the nozzle number of the recording element 243 in the correction table 44a. As a result, corrected image data is generated.

The control unit 40 performs a halftone process for converting the corrected image data of 8 bits for each pixel into pseudo halftone image data of 1 bit for each pixel (step S302). Prior to the halftone processing, various image processing such as gradation correction processing such as gamma correction may be performed by the image processing unit 52 as necessary.

The control unit 40 causes the head unit 24 to execute an image recording operation related to the print job based on the image data generated in step S303 (step S303). The processing operation of the control unit 40 in step S303 is the same as the processing operation in step S101 of the correction table generation process except for the image data to be used.
When an image is formed on the recording medium P, the control unit 40 sends the recording medium P to the paper discharge unit 30 and ends the image recording process.

(Modification 1)
Next, the modification 1 of the said embodiment is demonstrated. This modification differs from the above embodiment in that the reference values included in the correction table 44a are set only for some of the recording elements 243. Below, it demonstrates centering on difference with the said embodiment.

FIG. 11 is a diagram showing an example of the contents of the correction table 44a according to this modification.
As shown in FIG. 11, in the correction table 44a of this modification, reference values are set only for the representative recording elements corresponding to the nozzle numbers n for every 8 nozzles (every 7 nozzles). Specifically, the reference value is set only for the printing element 243 whose nozzle number n is ns × 8 (ns is a natural number satisfying 0 ≦ ns ≦ n _end / 8). Here, ns represents a representative recording element number (representative nozzle number). The representative recording element may be set for each nozzle number of 7 or less or 9 or more.

In the case where the input value of the image data is corrected by applying the correction table 44a of this modification, the input value and the nozzle number are ns for the printing elements 243 having the nozzle number n of ns × 8 to ns × 8 + 7. Correction is made to the reference value set for the x8 representative recording element. Instead of this, the reference value of the recording element 243 other than the representative recording element is determined by linear interpolation between two reference values set in the two representative recording elements adjacent to the recording element 243. May be.
Hereinafter, the classification of the printing elements 243 corresponding to each ns and having the nozzle number n from ns × 8 to ns × 8 + 7 is also referred to as printing element classification. Accordingly, each recording element section of this modification includes eight recording elements 243. Note that an aspect in which each recording element section includes a single recording element 243 corresponds to the above-described embodiment.

Next, the generation process of the correction table 44a of this modification will be described. The correction table generation process of this modification differs from the correction table generation process of the above-described embodiment shown in FIG. 8 in part of the processing procedure of the reference value setting process (step S108).

FIG. 12 is a flowchart showing the control procedure of the reference value setting process called in the correction table generation process of the present modification.
In the reference value setting process of this modification, steps S204 to S208, step S213, and step S214 in the reference value setting process of the above-described embodiment shown in FIG. 9 are changed to steps S204a to S208a, step S213a, and step S214a, respectively. It is a thing. Hereinafter, differences from the reference value setting process of FIG. 9 will be described.

In the reference value setting process of this modification, when it is determined that the input value in is less than 256 (“YES” in step S203), the control unit 60 relates to the gradation expression error Error and the representative nozzle number. 0 is substituted into the variable ns (step S204a), and it is determined whether or not the representative nozzle number ns is n _end / 8 or less (step S205a).

When it is determined that the representative nozzle number ns is equal to or less than n _end / 8 (“YES” in step S205a), the control unit 60 has 16 bits for each n from n = ns × 8 to ns × 8 + 7. 16-bit average value (hereinafter referred to as data_avg16) of the corrected input value data (LUTin [in] [n]) is calculated (step S206a). Specifically, correction input value data (LUTin [in] [n]) from n = ns × 8 to ns × 8 + 7 is added, and a quotient obtained by dividing the addition result by 8 is acquired as data_avg16.

The control unit 60 substitutes the quotient obtained by dividing data_avg16 by 257 into 8-bit data (data8) (step S207a), and calculates the data8 × from the sum of the current gradation expression error Error and data_avg16 to the gradation expression error Error. A value obtained by subtracting 257 is substituted (step S208a).

When the process of step S211 or step S212 ends, or when the gradation expression error Error is determined to be less than 128 in the process of step S209 (“NO” in step S209), the control unit 60 uses the input value. Data8 as the low-bit number correction input value data is stored in the 8-bit data array LUTout [in] [ns] corresponding to in and the representative nozzle number ns (step S213a). When the process of step S213a ends, the control unit 60 adds 1 to the representative nozzle number ns (step S214a), and returns the process to step S205a.

As described above, in this modification, the bit number reduction process is performed in units of recording element sections. That is, a 16-bit average value of the corrected input value data corresponding to each recording element 243 included in the recording element section is acquired, and a bit number reduction process for reducing the number of bits of the average value to 8 bits is performed for each recording element section. To be done. Then, when the difference between the average color values before and after the bit number reduction processing is succeeded to the next stage and the accumulated value of the inherited differences exceeds 128, data 8 as low bit number correction input value data is used. 1 is added to.
Note that instead of using the average value of the corrected input value data in the printing element classification as described above, the reference value may be determined using the added value before the average of the corrected input value data. In this case, in step S206a, an added value of eight correction input value data in the printing element classification is calculated, and in step S207a, a quotient obtained by dividing the added value by 257 × 8 is substituted for data8, and in step S208a. Then, a value obtained by subtracting data 8 × 257 × 8 from the sum of the current gradation expression error Error and the integrated value is substituted into the gradation expression error Error. In step S209, the gradation expression error Error is 128 × 8 or more. In step S212, 257 × 8 may be subtracted from the gradation expression error Error.

(Modification 2)
Next, Modification 2 of the above embodiment will be described. This modified example is the above-described modified example 1 in that the reference values included in the correction table 44a are set only for some of the recording elements, in addition to being set only for some of the recording elements. And different. That is, the present modification corresponds to an aspect in which the input value for which the reference value is set in the correction table 44a is thinned out in the first modification. Hereinafter, differences from the first modification will be described.

FIG. 13 is a diagram showing an example of the contents of the correction table 44a according to this modification.
As shown in FIG. 13, in the correction table 44a of the present modification, reference values are set only for the representative recording elements whose nozzle number n is ns × 8, and are within the input value range of 0 to 255. Then, input values periodically selected at intervals of predetermined input value thinning-out numbers (here, 5) such as “0”, “5”, “10”,..., “250”, “255” Are selected as representative input values, and reference values corresponding to the representative input values are set. In other words, among the 256 gradation input values in, the reference value is set only for the representative input value whose input value in is ins × 5 (ins is a natural number satisfying 0 ≦ ins <52). Here, ins represents a representative input value number (representative input value number).

When correcting the input value of the image data by applying the correction table 44a of this modification, first, the representative recording element in the recording element unit including the target recording element is specified. Further, two representative input values that approximate the input value of the image data to be corrected are specified as the first input value and the second input value. Then, two reference values set corresponding to the first input value and the second input value with respect to the identified representative recording element are obtained as the first input value, the second input value, and the input value of the image data. A reference value is determined by performing linear interpolation according to the relationship, and an input value of image data is corrected to the reference value. If the input value of the image data is one of the representative input values, a reference value determined for the representative input value may be used.
The input value thinning-out number is not limited to 5, and may be 4 or less or 6 or more. Further, the reference value may be thinned out only in the gradation direction of the input value without thinning out the reference value in the recording element direction.

Next, the generation process of the correction table 44a of this modification will be described. The correction table generation process of the present modification is different from the correction table generation process of the first modification and part of the processing procedure of the reference value setting process.

FIG. 14 is a flowchart showing the control procedure of the reference value setting process called in the correction table generation process of the present modification.
In the reference value setting process of this modification, step S202, step S203, step S213a, and step S215 in the reference value setting process of modification 1 shown in FIG. 12 are changed to step S202b, step S203b, step S213b, and step S215b, respectively. It is changed and step S216 is added. Hereinafter, differences from the reference value setting process of FIG. 12 will be described.

When the reference value setting process of the present modification is started, the control unit 60 substitutes 0 for the variable ins related to the representative input value (step S202b). Further, the control unit 60 determines whether or not the representative input value ins is less than 52 (step S203b). If it is determined that the representative input value ins is less than 52 (“YES” in step S203b), the input value in Is substituted for ins × 5 (step S216). By the processing from step S204a to step S214a below, a reference value (low bit number corrected input value data) corresponding to each representative recording element is set for each representative input value whose input value in is ins × 5. . Among these, in the process of step S213b, the control unit 60 stores data8 as the low bit number correction input value data in the 8-bit data array LUTout [ins] [ns] corresponding to the representative input value ins and the representative nozzle number ns. Do

If it is determined in step S205a that the representative nozzle number ns is larger than n _end / 8 (“NO” in step S205a), the control unit 60 adds 1 to the representative input value ins (step S215b). ), The process returns to step S203b.
When it is determined in the process of step S203b that the representative input value ins is 52 or more (“NO” in step S203b), the control unit 60 stores the 8-bit data array LUTout [ins] [ns]. The correction table 44a using the low bit number correction input value data as a reference value is stored in the storage unit 44 of the recording apparatus 1, and the reference value setting process and the correction table generation process are terminated.

(Modification 3)
Next, Modification 3 of the above embodiment will be described.
In the above embodiment and each modification, a 16-bit correction table is generated based on the 16-bit output color value table, and the correction table 44a is generated by reducing the correction input value of the correction table to 8 bits. did. In contrast, in this modification, 8-bit low bit number correction input value data is directly generated from the high bit number output color value data of the 16-bit output color value table, and the obtained low bit number correction input value data is obtained. Based on the above, the correction table 44a is generated.

Specifically, in the reference value setting process of this modification, 16 bits of high bit number corrected input value data from high bit number output color value data is obtained for each stage in the data array of high bit number output color value data. And a bit number reduction process for generating 8-bit low bit number correction input value data based on the generated high bit number correction input value data, and the obtained low bit number correction input Value data is stored in an 8-bit data array LUTout [in] [n]. Also in this modification, by passing the error value generated in the bit number reduction process to the next stage, the color value information that is lost due to the reduction in the number of bits is converted into a plurality of low bit number correction input value data in the subsequent stage. Can be distributed and reflected.

As described above, the reference value setting method of the present embodiment includes a plurality of recording elements 243 that are provided at different positions in the X direction and each perform an output operation for outputting colored pixels to the recording medium P. By causing each of the plurality of recording elements 243 to perform an output operation based on the corrected input value obtained by correcting the input value, a pixel is output to the recording medium P with a color having a predetermined number of recording gradations. A reference value setting method that is referred to for correction of an input value in an inkjet recording apparatus 100 (image recording apparatus) that includes a control unit 40 (recording control unit) that records a plurality of recording elements 243. Is output for each of a plurality of recording element sections divided into a predetermined number of recording elements 243 in the X direction by a recording element 243 included in the recording element section based on a predetermined input value. Output color value acquisition step for acquiring an output color value that represents a prime color with a number of gradations larger than the number of recording gradations, corresponding to a predetermined input value based on the output color value for each of a plurality of recording element sections A reference value setting step for setting a reference value from which a corrected input value can be acquired. In the reference value setting step, the color value data (high value) of the color value acquired based on the output color value and corresponding to the corrected input value Bit number reduction processing for generating low bit number color value data (low bit number correction input value data) having a smaller number of bits than the color value data based on the bit number correction input value data). In the bit number reduction process for each of the plurality of recording element sections in the order according to the arrangement order in the X direction, and for the recording element section excluding the head in the arrangement order, the number of bits up to the previous stage A low bit in which the accumulated value of the error value caused by the difference between the color value of the color value data and the color value data of the generated low-bit number color value data is obtained in the reduction process, and the color value is adjusted based on the accumulated value Numerical color value data is generated, and a reference value is set based on the generated low-bit numerical color value data.
According to such a method, after generating color value data having a high number of bits, the number of bits of the color value data is reduced, and an error value corresponding to the color value difference before and after the bit number reduction is passed on to the subsequent stage. Thus, the information on the color value of the color value data that will be lost due to the reduction in the number of bits corresponds to a low number of bits over a plurality of recording elements 243 (recording element classifications in Modifications 1 and 2) such as about 10 to 100 in the subsequent stage. It can be reflected and reflected in the color value data. Therefore, by correcting the input value using the reference value of the correction table 44a set based on the low bit number color value data, in a range covering a plurality of recording elements 243 (recording element divisions) such as about 10 to 100. The distribution of visually recognized output color values can be brought close to the distribution of color values of input values in the range. In this way, by adjusting the distribution of color values output within a certain range on the recording medium P, color unevenness caused by quantum errors included in individual correction input values is visually recognized in the recorded image. The occurrence of defects can be suppressed. Further, since the reference value corresponding to each recording element 243 is set and the correction table 44a is generated based on the low bit number color value data after the bit number reduction processing, the data amount of the correction table 44a is set. The increase can be suppressed. Therefore, according to the above method, it is possible to set the reference value that can more reliably suppress the degradation of the image quality of the recorded image while suppressing the increase in the data amount.

In the above embodiment, the predetermined number is 1, and one recording element 243 is included in each recording element section. Thereby, it is possible to generate the correction table 44a reflecting the characteristic variation of each recording element 243. By correcting the input value using such a correction table 44a, it is possible to acquire a more accurate corrected input value that can more reliably suppress the deterioration of the image quality of the recorded image.

Further, in Modification 1 and Modification 2, the predetermined number is 2 or more, and each recording element section includes two or more recording elements 243. As a result, the number of low-bit number color value data generated for one input value is reduced, so that the number of data in the printing element section direction in the correction table 44a can be thinned out. Therefore, the data amount of the correction table 44a can be further reduced.

In Modification 1 and Modification 2, the color value corresponding to the correction input value is a color value corresponding to the correction input value for each of two or more recording elements 243 included in each of the plurality of recording element sections. Corresponds to the average value of. As a result, the amount of information included in the high bit number correction input value data corresponding to each recording element section is increased more than the amount of information included in the high bit number correction input value data corresponding to a single recording element 243. Can do. Therefore, the color value of the low bit number color value data generated based on the high bit number correction input value data and the reference value in the correction table 44a based on the low bit number color value data are set to more accurate values. can do.

In the output color value acquisition step in the embodiment and the first modification, the output color value of the recording gradation number is acquired based on the input value of the recording gradation number for each of the plurality of recording element sections, and the reference value In the setting step, low bit number color value data having a recording gradation number is generated based on color value data having a recording gradation number corresponding to each of the plurality of recording element sections, and recording is performed for each of the plurality of recording element sections. A reference value capable of acquiring a correction input value corresponding to the input value of the number of gradations is set. As a result, it is possible to generate a correction table 44a that can obtain an appropriate input correction value for each of the input values of the number of recording gradations.

Further, in the output color value acquisition step according to the second modification, for each of the plurality of recording element sections, the predetermined gradation is determined based on the input value of the predetermined gradation number corresponding to a part of the gradations of the recording gradation number. In the reference value setting step, the low-bit-number color value data of the predetermined gradation number is obtained based on the color value data of the predetermined gradation number corresponding to each of the plurality of recording element sections. For each of the plurality of printing element sections, a reference value that can obtain a corrected input value corresponding to the input value of the predetermined number of gradations is set. Thereby, the number of data in the gradation direction in the correction table 44a can be thinned out. Therefore, the data amount of the correction table 44a can be further reduced.

Further, the information processing apparatus 2 of the above embodiment includes a control unit 60, and each of the plurality of recording element sections obtained by dividing the plurality of recording elements 243 for each predetermined number of recording elements 243 in the X direction. Output color value representing the color of the pixel output based on a predetermined input value by the recording element 243 included in the recording element section with a gradation number larger than the recording gradation number (output color value acquisition) And a reference value capable of acquiring a corrected input value corresponding to a predetermined input value based on the output color value for each of the plurality of recording element sections (reference value setting means), and as a reference value setting means The control unit 60 has a bit number smaller than that of the color value data based on the color value data (high bit number correction input value data) of the color value acquired based on the output color value and corresponding to the correction input value. Low bit number color The bit number reduction processing for generating data is performed for each of the plurality of recording element sections in the order according to the arrangement order of the plurality of recording element sections in the X direction, and the recording element section excluding the head in the arrangement order is selected. In the target bit number reduction process, the cumulative value of the error value generated by the difference between the color value of the color value data and the color value of the generated low bit number color value data in the previous bit number reduction process is acquired, Low bit number color value data in which the color value is adjusted based on the accumulated value is generated, and a reference value is set based on the generated low bit number color value data. According to the information processing apparatus 2 having such a configuration, it is possible to set a reference value that can more reliably suppress a decrease in image quality of a recorded image while suppressing an increase in data amount.

In addition, the inkjet recording apparatus 100 of the above embodiment is provided with a plurality of recording elements 243 that are provided at different positions from the information processing apparatus 2 in the X direction and each perform an output operation for outputting colored pixels to the recording medium P. And a storage unit 44 that stores a correction table 44 a (reference data) in which reference values set by the information processing device 2 are arranged, and a control unit 40. The control unit 40 is stored in the storage unit 44. The input value is corrected to the corrected input value based on the correction table 44a, and the output operation is performed by each of the plurality of recording elements 243 based on the corrected input value. Is output to the recording medium P to record an image (recording control means). According to the ink jet recording apparatus 100 having such a configuration, it is possible to more reliably suppress a decrease in the image quality of a recorded image. In addition, the information processing device 2 generates the correction table 44a in which the increase in the data amount is suppressed and stores the correction table 44a in the storage unit 44. Therefore, it is possible to suppress an increase in the capacity of the storage unit 44, and to increase the capacity. The cost increase accompanying this can be suppressed.

Note that the present invention is not limited to the above-described embodiments and modifications, and various modifications can be made.
For example, in the above-described embodiment and each modified example, the reference value of the correction table 44a has been described using an example in which the input value is a corrected input value. However, the present invention is not limited to this. For example, as shown in FIG. 15, the reference value of the correction table 44a may indicate a correction amount for the input value. In the correction table 44a, the correction input value can be acquired by adding the correction amount indicated in the reference value to the input value.

Further, in the bit number reduction processing in the above embodiment and each modified example, the example in which the lower 8 bits of the color value data (high bit number correction input value data) are rounded down has been described. Instead, rounding up and rounding off are performed. , Rounding to the nearest even number may be applied. For example, in the bit number reduction process that rounds up the lower 8 bits, the negative difference between the color values before and after the bit number reduction is accumulated in the next stage, so when the accumulated value falls below a predetermined value, the low bit number color value data is Adjustment to be reduced may be performed.

Also, in the bit number reduction process, instead of the color value difference itself before and after the bit number reduction, a value corresponding to the color value difference may be taken over. For example, a value obtained by rounding the lower-order bits of the color value difference may be taken over.

Further, in the bit number reduction process in the embodiment and each modified example, the accumulated value of the error value up to the previous stage is changed from the color value data of the color value data in the bit number reduction process of the stage to the low bit number color value data before adjustment. When the value obtained by subtracting the difference value exceeds the specified reference range, the low bit number color value data was adjusted, but this is not the only case, and the value is reduced only according to the accumulated error value up to the previous stage. The bit number color value data may be adjusted.

The input value of the image data is not limited to 8 bits (256 gradations) and may be 7 bits or less or 9 bits or more.
Further, the low bit number color value data after the bit number reduction process does not have to match the bit number of the input value. For example, 16-bit color value data generated for an 8-bit input value may be reduced to 10 bits, and the correction table 44a may be generated based on the 10-bit low bit number color value data.

In the above-described embodiment and each modification, the description has been given using the example in which the control unit 60 of the information processing apparatus 2 performs the color value data generation process, the bit number reduction process, and the correction table 44a generation process. These processes may be executed by the control unit 40 of the recording apparatus 1. Further, these processes may be executed by an information processing apparatus provided outside the ink jet recording apparatus 100.

In each of the above-described embodiments and modifications, the inkjet recording apparatus 100 has been described as an example of the image recording apparatus, but the present invention is not limited to this. For example, the output of colored pixels can be output according to the output operation of the recording element, such as an electrophotographic image recording apparatus that transfers an image of toner particles applied to an electrostatic latent image forming area on a photosensitive drum to a recording medium. The present invention can be applied to various types of image recording apparatuses. For example, in the above-described electrophotographic image recording apparatus, a recording element is constituted by a light emitting element used for forming an electrostatic latent image.

Although several embodiments of the present invention have been described, the scope of the present invention is not limited to the above-described embodiments, and includes the scope of the invention described in the claims and equivalents thereof. .

The present invention can be used for a reference value setting method, an information processing apparatus, and an image recording apparatus.

DESCRIPTION OF SYMBOLS 1 Recording device 2 Information processing apparatus 10 Paper feed part 11 Paper feed tray 12 Medium supply part 20 Image formation part 21 Conveyance part 211 Conveyance drum 22 Delivery unit 23 Heating part 24 Head unit 241 Recording head drive part 242 Recording head 242M Head module 243 Recording element 25 Fixing unit 26 Image reading unit 27 Delivery unit 30 Paper discharge unit 31

Paper discharge tray

40, 60

Control unit

41, 62 CPU
42, 62 RAM
43, 63 ROM
44, 64 Storage unit 44a Correction table 51 Transport drive unit 52

Image processing unit

53, 72 Input /

output interface

54, 73 Bus 71 Operation display unit 100 Inkjet recording device 200 External device G Test chart G0 to G16 Color band P Recording medium

Claims

A plurality of recording elements that are provided at different positions in a predetermined direction and that each perform an output operation for outputting colored pixels to a recording medium, and the plurality of recording elements based on a corrected input value obtained by correcting an input value The input value in the image recording apparatus, comprising: a recording control unit configured to record the image by outputting the pixels to the recording medium with a color having a predetermined recording gradation number by causing the recording element to perform the output operation. A reference value setting method referred to for correction of
For each of the plurality of recording element sections obtained by dividing the plurality of recording elements for each predetermined number of recording elements in the predetermined direction, the pixels output based on a predetermined input value by the recording elements included in the recording element section An output color value acquisition step of acquiring an output color value representing a color with a gradation number larger than the recording gradation number;
A reference value setting step for setting the reference value from which a correction input value corresponding to the predetermined input value can be acquired based on the output color value for each of the plurality of printing element sections;
Including
In the reference value setting step,
Based on the color value data of the color value acquired based on the output color value and corresponding to the corrected input value, a bit number reduction process for generating low bit number color value data having a smaller number of bits than the color value data. Performing each of the plurality of recording element sections in an order according to the arrangement order of the predetermined direction of the plurality of recording element sections,
In the bit number reduction process for the printing element classification except the head in the arrangement order, the color value of the color value data and the color value of the generated low bit number color value data in the bit number reduction process up to the previous stage Acquire the accumulated value of the error value caused by the difference, and generate low-bit number color value data in which the color value is adjusted based on the accumulated value,
A reference value setting method for setting the reference value based on the generated low bit number color value data.
2. The reference value setting method according to claim 1, wherein the predetermined number is one.
2. The reference value setting method according to claim 1, wherein the predetermined number is two or more.
The color value corresponding to the correction input value corresponds to a value obtained by averaging the color values corresponding to the correction input values for each of two or more recording elements included in each of the plurality of recording element sections. How to set the reference value described.
In the output color value acquisition step, for each of the plurality of recording element sections, the output color value of the recording gradation number is acquired based on the input value of the recording gradation number,
In the reference value setting step, low bit number color value data of the recording gradation number is generated based on the color value data of the recording gradation number corresponding to each of the plurality of recording element sections, and the plurality of recording gradation values is generated. The reference value setting method according to any one of claims 1 to 4, wherein, for each element classification, the reference value capable of obtaining a correction input value corresponding to the input value of the recording gradation number is set.
In the output color value obtaining step, for each of the plurality of recording element sections, the predetermined number of gradations is determined based on an input value of a predetermined number of gradations corresponding to a part of the gradations of the recording gradation number. Obtaining the output color value;
In the reference value setting step, low bit number color value data of the predetermined gradation number is generated based on the color value data of the predetermined gradation number corresponding to each of the plurality of recording element sections, and the plurality of recording elements The reference value setting method according to any one of claims 1 to 4, wherein the reference value that can acquire a correction input value corresponding to the input value of the predetermined number of gradations is set for each element classification.
A plurality of recording elements that are provided at different positions in a predetermined direction and that each perform an output operation for outputting colored pixels to a recording medium, and the plurality of recording elements based on a corrected input value obtained by correcting an input value The input value in the image recording apparatus, comprising: a recording control unit configured to record the image by outputting the pixels to the recording medium with a color having a predetermined recording gradation number by causing the recording element to perform the output operation. An information processing apparatus for setting a reference value referred to for correction of
For each of the plurality of recording element sections obtained by dividing the plurality of recording elements for each predetermined number of recording elements in the predetermined direction, the pixels output based on a predetermined input value by the recording elements included in the recording element section Output color value acquisition means for acquiring an output color value representing a color with a gradation number larger than the recording gradation number;
Reference value setting means for setting the reference value capable of acquiring a corrected input value corresponding to the predetermined input value based on the output color value for each of the plurality of printing element sections;
With
The reference value setting means includes
Based on the color value data of the color value acquired based on the output color value and corresponding to the corrected input value, a bit number reduction process for generating low bit number color value data having a smaller number of bits than the color value data. Performing each of the plurality of recording element sections in an order according to the arrangement order of the predetermined direction of the plurality of recording element sections,
In the bit number reduction process for the printing element classification except the head in the arrangement order, the color value of the color value data and the color value of the generated low bit number color value data in the bit number reduction process up to the previous stage Acquire the accumulated value of the error value caused by the difference, and generate low-bit number color value data in which the color value is adjusted based on the accumulated value,
An information processing apparatus that sets the reference value based on the generated low bit number color value data.
An information processing apparatus according to claim 7;
A plurality of recording elements that are provided at different positions in a predetermined direction and each perform an output operation for outputting colored pixels to a recording medium;
A storage unit for storing reference data in which reference values set by the information processing apparatus are arranged;
Based on the reference data stored in the storage unit, an input value is corrected to a corrected input value, and the output operation is performed by each of the plurality of recording elements based on the corrected input value, whereby predetermined recording is performed. Recording control means for recording an image by outputting pixels to a recording medium with colors of the number of gradations;
An image recording apparatus comprising: