JP2006103054A - Recording method and recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording method and a recording apparatus capable of performing an appropriate compensation to a defective nozzle in considering mixed colors, and performing a good compensating recording over the whole color region. <P>SOLUTION: In performing correction by detecting the defective nozzle, values of image data of other color components corresponding to the image data of a color component to be used for recording by the defective nozzle detected are investigated. The amount of the compensation used for specified different color compensation is corrected according to the values, and using the amount of the compensation corrected, the values of the color image data are corrected for the different color compensation. Using the corrected color image data, recording is performed by an inkjet recording head. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a recording method and a recording apparatus, and more particularly, to a correction method for complementary recording performed on an ink ejection failure nozzle of an ink jet recording head that ejects ink to form an image with ink on a recording medium.

  With the spread of information processing equipment such as copying machines, word processors, computers, and communication equipment, digital image registration using one of the inkjet recording heads as one of the image forming (recording) equipment of these equipment. Things that do are spreading rapidly. In addition, with the increase in quality and color of visual information in the above information equipment and communication equipment, there is an increasing demand for higher image quality and color in recording apparatuses.

  In such a recording apparatus, an ink discharge port and a liquid path are used as a recording head (hereinafter, also referred to as a multi-head) in which a plurality of recording elements are integrated and arranged for miniaturization of recording pixels and high-speed recording. In general, for example, a plurality of multi-heads corresponding to each ink of cyan, magenta, yellow, and black are provided for colorization. One way of technological progress from the past is to perform high-speed, high-quality, and inexpensive recording using such a configuration. Furthermore, in order to increase the speed, a recording medium using a recording head (hereinafter referred to as a full-line recording head) in which the length of the multi-head is about the width of the recording medium used for recording is used without scanning the multi-head. A method of outputting at a high speed just by transporting the image is also being realized.

  However, for example, in the case of a recording apparatus in which the vertical width of A4 size is the recording width, the recording width of the full line recording head is about 30 cm, and when the recording resolution is 600 dpi, 7000 or more ink ejection nozzles (hereinafter, referred to as the recording width). Nozzle). It is very difficult to manufacture such a full-line recording head having many nozzles without defects from the viewpoint of yield.

  Also, because of the large number of nozzles, not all nozzles have the same performance. Furthermore, there is a high possibility that nozzles (hereinafter, defective nozzles) that do not eject ink during use will appear. Therefore, head shading technology that corrects unevenness in ink discharge from the nozzles and unevenness in ink discharge position (correction), and complement processing for defective nozzles, not a defect-free full-line recording head. Attention has been focused on non-discharge complementation technology that makes it possible to use both.

  As a head shading method, a method is generally used in which the density of dots recorded by each nozzle is measured and the result is fed back to input image data. For example, if a certain nozzle has a small ink discharge amount for some reason and the density of that part is low, the gradation value of the input image data of the part corresponding to that nozzle is corrected and output. The image density is made uniform in the image. A technique relating to head shading that corrects density unevenness caused by the variation of each nozzle of the recording head is disclosed in, for example, Japanese Patent Application Laid-Open No. 2004-151867.

  Moreover, as a method of non-discharge complementation, the following methods have been conventionally proposed.

  That is, when a nozzle that discharges cyan ink is defective in discharge, a method of replacing ink to be discharged using the nozzle with discharge from nozzles on both sides (this is called complementary color), and recording with cyan ink are performed. A portion to be recorded, which is recorded with ink of another color such as black in a portion corresponding to the defective nozzle, a method of supplementing recording of the portion (this is called different color complementation), and recording using the defective nozzle There is a method of distributing the data to be performed to the nozzles on both sides thereof (see, for example, Patent Document 2).

  Further, in the case of performing different color complementation, conventionally, the amount of different color ink to be complemented has been determined using the continuous number of defective nozzles and image density data (tone values) of pixels corresponding to the defective nozzles as arguments. In the future, in this specification, the amount to be complemented will be referred to as a reference different color complement amount, and a function indicating the ratio of the reference different color complement amount to the input gradation value will be referred to as a reference different color complement table.

  In parallel with this different color complement, data that should have been used for recording with a defective nozzle may be complemented with the same color using nozzles on both sides of the defective nozzle.

  The same color interpolation is performed by distributing data so that data corresponding to a defective nozzle is recorded by adjacent nozzles, and a distribution coefficient indicating the distribution ratio indicates the content of the same color interpolation. This distribution coefficient can be expressed as F_s [c] [r] [tone].

  This coefficient is a function of the color (c) of ink ejected by the defective nozzle, the distribution position (r), and the input tone value (tone) at the defective nozzle. In addition, when defective nozzles continue, this distribution coefficient (F_s [c] [s] [r] [tone]) may be changed.

That is, if the input image data (tone value) at nozzle number (n) is D [c] [n] and the corrected data is D '[c] [n],
D '[c] [nr] = D [c] [nr] + D [c] [n] x F_s [c] [r] [D [c] [n]]
There is a relationship.

On the other hand, in the case of a different color complement, when a certain nozzle is a defective nozzle, in order to make the non-ejection of ink from that nozzle inconspicuous, the non-ejection portion is made of ink of a different color from the ink ejected from that defective nozzle. This is done by compensating, and the amount to be supplemented is the reference different color complement amount. The reference different color complement amount (F_d [c] [cc] [s] [tone]) is the ink color (c) ejected by the defective nozzle, the complementary ink color (cc), the continuous number of defective nozzles (s), And the input tone value (tone) of the pixel corresponding to the defective nozzle. That is,
D '[cc] [n] = D [cc] [n] + F_d [c] [cc] [s] [D [c] [n]]
There is a relationship.
JP-A-4-18361 Japanese Patent Laid-Open No. 2002-19101

  However, since the standard different color complementation amount in the above-mentioned conventional example is set on the premise of the color of each density component, when these colors are mixed, particularly in the combination of yellow and cyan or the combination of yellow and magenta. In some cases, the complementary processing is not sufficient.

  There are two possible causes for this.

  One is the influence of the phenomenon that the blur of dots formed on the recording medium increases due to an increase in the ink discharge amount (that is, the dot diameter increases), and the other is the nonlinearity of lightness in the mixed color. There is an increase effect.

  The influence of the former changes so that the area is not noticeable as a result of the large amount of dot bleeding into the area that should have been recorded by the defective nozzle. The effect of the latter is somewhat complicated. For example, when yellow ink is added to magenta ink, the amount of change in lightness is smaller than the lightness component of the added yellow ink. Depending on the type, it may become brighter. On the other hand, the lightness of the mixed color of cyan ink and magenta ink is often quite low, and since the chroma range in that region is small, the color difference is small and is not noticeable, so this is not a big problem. Therefore, when uniform complementation is performed, the complementation may be excessive or conversely insufficient.

  The present invention has been made in view of the above-described conventional example, and provides a recording method and a recording apparatus capable of appropriately complementing defective nozzles in consideration of mixed colors and performing good complementary recording over the entire color gamut. For the purpose.

  In order to achieve the above object, the recording method of the present invention comprises the following steps.

  That is, a recording method with complementary recording for a recording failure by an ink jet recording head that performs color recording using a plurality of colors of ink, using an input step of inputting a predetermined amount of color image data, and the color image data A detecting step for detecting a defective recording element of the ink jet recording head for recording, and another color corresponding to the image data of the color component to be used for recording with the defective recording element detected in the detecting step A correction step of checking the value of the component image data and correcting a complementary amount used for predetermined different color complementation according to the value; and a value of the color image data for different color complementation using the correction amount corrected in the correction step Using the correction process for correcting the color image data and the color image data corrected in the correction process. Ri and having a recording step for recording.

  It is desirable that the correction step further corrects the value of the color image data for a predetermined same color complement to the defective recording element.

  Further, it is desirable that the correction amount of the complement amount used for the different color complement follows the sum of the values of the image data of all the other color components.

  Furthermore, it is desirable to compare the correction amount of the complement amount used for the different color complementation with the supplement amount used for the predetermined different color complementation, and select either the different color complement or the same color complement according to the comparison result.

  Here, the supplement amount used for the different color complement is related to an ink ejection amount for performing complementary recording using the different color ink from another recording element that ejects different color ink to the recording position of the defective recording element. The supplement amount used for the same color complement is the value when distributing the value of multi-value recording data that was to be recorded by the defective recording element to a plurality of recording elements in the vicinity of the defective recording element Distribution coefficient.

  Furthermore, the ink jet recording head desirably includes an electrothermal transducer for generating thermal energy to be applied to the ink in order to eject the ink using thermal energy.

  According to another aspect of the invention, there is provided a recording apparatus that performs complementary recording using the recording method configured as described above.

  As described above, according to the present invention, when a defective nozzle is detected and corrected, the other color component data used for discharging ink of other colors at the position corresponding to the defective nozzle is referred to. Since the amount of different color correction is corrected, it is possible to perform more appropriate complementary recording considering a mixed color of multiple ink colors, reducing image defects that could not be corrected by conventional methods, and recording high-quality images There is an effect that can be done.

  This contributes to an improvement in the yield of manufacturing a usable recording head.

  Hereinafter, preferred embodiments of the present invention will be described more specifically and in detail with reference to the accompanying drawings.

  In this specification, “recording” (sometimes referred to as “printing”) is not only for forming significant information such as characters and figures, but also for human beings visually perceived regardless of significance. Regardless of whether or not it has been manifested, it also represents a case where an image, a pattern, a pattern, or the like is widely formed on a recording medium or the medium is processed.

  “Recording medium” refers not only to paper used in general recording apparatuses but also widely to cloth, plastic film, metal plate, glass, ceramics, wood, leather, and the like that can accept ink. Shall.

  Furthermore, “ink” (sometimes referred to as “liquid”) is to be interpreted broadly in the same way as the definition of “recording (printing)” above. It represents a liquid that can be used for forming a pattern or the like, processing a recording medium, or processing an ink (for example, solidification or insolubilization of a colorant in ink applied to the recording medium).

  Furthermore, unless otherwise specified, the “nozzle” collectively refers to an ejection port or a liquid channel communicating with the ejection port and an element that generates energy used for ink ejection.

  First, a complementary recording method applied when the present invention performs recording using a recording head employing an ink jet recording method will be conceptually described.

  As described above, there are two methods for complementing defective nozzles, namely, same color complementation and different color complementation.

  The complement processing in the present invention includes at least one of different color complement and same color complement, and preferably performs the different color complement and the same color complement in parallel.

  As described above, the same color interpolation is performed by distributing data so that the data corresponding to the defective nozzle is recorded by the adjacent nozzle, and the distribution ratio is the distribution coefficient (F_s [c] [s] [r] [tone]).

  On the other hand, the different color complement amount (reference different color complement amount (F_d [c] [cc] [s] [tone])) in the different color complement is the color (c) of the ink ejected by the defective nozzle, as described above. It is determined by the ink color to be complemented (cc), the number of consecutive defective nozzles (s), and the input tone value (tone) of the pixel corresponding to the defective nozzle. In practice, the reference different color complement amount (F_d [c] [ cc] [s] [tone]) are tabulated and the amount of different colors to be complemented is determined.

  The present invention is characterized by referring to the other color components of the pixel to be complemented and modifying the distribution coefficient and the standard different color complementation table. This other color component is, for example, a printer that performs recording using four colors of ink of cyan (C), magenta (M), yellow (Y), and black (K) when cyan ink is poorly ejected. Indicates magenta, yellow, and black components, and when the value of this component is large, the distribution coefficient and the reference color complementation amount are corrected.

  As described above, this correction is performed in consideration of the influence of enlargement of the dot diameter and the like, and it is preferable to reduce them with respect to the distribution coefficient in the same color interpolation and the reference different color interpolation amount in the different color interpolation. Also, in general, different color complementation for yellow is not performed, and for the mixed color of cyan and magenta, the complement processing of defective nozzles is at a level that can be satisfied to some extent, so other color components are cyan and magenta. On the other hand, it is sufficient to treat the yellow component as another color component. In addition, when the same color complementation and different color complementation are performed in parallel, first, the standard different color complement amount in the different color complementation is corrected, and when the correction of the reference different color complement amount is insufficient, the distribution coefficient is set. It is effective to correct.

  Because the same color complementation is literally the complement using the same color ink, naturally the effect of the complementation is larger than the complementation with the different color, and it is necessary to prioritize the different color complementation until the contribution of the same color complementation with large effect is reduced Because there is no.

  It should be noted that the reference different color complementation table and the distribution coefficient naturally vary depending on the recording medium to be used, the relationship between the recording density and the ink dot size, and the combination of inks. It goes without saying that a complementary table is selected and used.

  In complementary recording, the first thing to be done is to detect a nozzle (defective nozzle) that causes ink ejection failure in a recording head having a plurality of ink ejection nozzles (hereinafter referred to as nozzles). It is not limited. Here, an example of the detection method will be described.

  FIG. 1 is a diagram illustrating a stair chart used for confirming the state of ink ejection from each nozzle. This step chart is one of the test patterns, and a step-like pattern is formed by recording a pattern of a predetermined length by the selected nozzle while sequentially selecting nozzles.

  For example, a stair chart as shown in FIG. 1 is output for each color of a plurality of inks ejected from the recording head, and this is read by a scanner or the like to detect defective nozzles. The nozzle number is input to a host computer connected to a recording apparatus equipped with a recording head. In addition, although ink is ejected, a nozzle whose ejection position is greatly deviated from a normal position expected in the nozzle row direction (for example, equivalent to one pixel or more) is also regarded as a defective nozzle. The nozzle number may be input.

  Furthermore, as another detection method, a detection substrate equipped with an electrode is installed facing the recording head, and a defective nozzle is detected from its electrical characteristics. Ink is ejected by scanning a laser beam against a test pattern. Various methods can be used, such as a method of detecting whether or not the

  In any case, correction processing is performed on the defective nozzle detected in this way. At this time, the distribution coefficient and the standard different color complementation table are corrected with reference to other color components in the processing target pixel, and the same color complement and different color complement are performed using these.

  After performing defective nozzle correction and shading correction processing as described above, the recording data is converted into bitmap data by performing binarization or multi-level processing, and actual recording is performed. .

  The method of binarization or multi-level processing is not particularly limited, but an error diffusion method with relatively good frequency response is desirable for the purpose of eliminating the unevenness of the nozzle unit.

  Next, a recording apparatus to which the above-described complementary recording correction method is applied will be described in detail.

  FIG. 2 is a perspective perspective view of a recording apparatus equipped with an ink jet recording head according to a typical embodiment of the present invention.

  The recording apparatus 110 includes a full-line inkjet recording head (hereinafter referred to as a recording head) 201 to 204 and a recovery system unit (not shown) for guaranteeing stable ink ejection at all times. The recording sheet 205 is supplied from the feeder unit 207 to a printing position by these recording heads, and is conveyed by a conveying unit 206 provided in a casing 208 of the recording apparatus.

  The printing of the image on the recording paper 205 is performed by transferring the black ink from the recording head 201 when the reference position of the recording paper 205 reaches below the recording head 201 that ejects black (K) ink while conveying the recording paper 205. Is discharged. Similarly, the recording paper 205 reaches the reference position in the order of the recording head 202 that discharges cyan (C) ink, the recording head 203 that discharges magenta (M) ink, and the recording head 204 that discharges yellow (Y) ink. Then, each color ink is ejected to form a color image. The recording sheet 205 on which the image is printed in this manner is discharged to the stacker tray 211 and accumulated.

  The recording apparatus 110 of this embodiment further includes an ink cartridge (not shown) that can be replaced for each ink for supplying ink to the transport unit 206 and the recording heads 201 to 204, ink supply to the recording heads 201 to 204, A pump unit (not shown) for a recovery operation, a control board (not shown) for controlling the entire recording apparatus 110, and the like are included. The front door 209 is an opening / closing door for replacing the ink cartridge.

  FIG. 3 is a block diagram illustrating the configuration of the control circuit of the recording apparatus 110.

  3, 400 is an MPU that controls the entire recording apparatus, 401 is a program ROM that stores various control programs executed by the MPU 401, 402 is a RAM that is used as a work area when the MPU 401 executes the control program, and 403 CGROM for storing font information for printing, 404 a VRAM used as a print buffer for bit-developing recording data for one page of recording paper, 405 a communication driver serving as an interface with the host, and 406 a roll paper transport A motor driver for controlling the movement of the recording head and the recovery unit, 407 is a motor driven by the motor driver 406, and 408 is a head driving circuit for driving the four recording heads 201 to 204. The VRAM 404 is configured so that the recording data can be stored in a separate buffer frame for each color component of YMCK.

  Reference numeral 409 denotes a sensor for detecting the remaining amount of ink, and reference numeral 410 denotes a gate array (G / A) having an interface between the VRAM 404 and the MPU 400 and a copy function in the VRAM 404. The gate array (G / A) 410 performs various functions according to instructions from the MPU 400, but can operate independently of the MPU 400.

  Reference numeral 102 denotes a host device that gives various recording data and recording instructions to the recording device 110.

  The recording heads 201 to 204 used in the recording apparatus shown in FIGS. 2 to 3 are thermal ink jet recording heads. This recording head discharges ink from the discharge port by driving a heater in the nozzle to generate heat, and can record a gradation image by data for discharging the ink. The resolution (nozzle density) of this recording head is 600 dpi, the amount of ink discharged by one recording operation is about 8 pl, the number of nozzles per recording head is 5120 nozzles, and the recording width is about 212 mm. In this apparatus, since the recording resolution in the conveyance direction of the recording medium is also 600 dpi, the resolution of the output image is 600 × 600 dpi.

  Also, in this example, each of the CMYK inks used was adjusted with various additives so that the physical property values thereof were approximately equal to a viscosity of 1.8 cps and a surface tension of 39 dyne / cm. The recording medium is inkjet plain paper (Canon: EW-100). The recording head drive conditions are a frequency of 8 kHz, a voltage of 10 V, and an applied pulse width of 0.8 μs. By this driving, about 8 pl ink droplets are ejected at a speed of about 15 m / sec. When an ink droplet of about 8 pl is ejected on this inkjet plain paper, the dot diameter is about 80 μm. Furthermore, a contact image sensor having a reading resolution of 1200 dpi was used as a scanner used for reading an image of a defective nozzle detection pattern.

  FIG. 4 is a diagram illustrating an ink ejection surface showing the nozzle arrangement of the recording heads 201 to 204.

  As shown in FIG. 4, the recording heads 201 to 204 are recording heads corresponding to four color inks of black (K), cyan (C), magenta (M), and yellow (Y), respectively. The nozzle row of each head is composed of 5120 nozzles.

  As shown as an example in FIG. 4, in this embodiment, in the same color complementation, that is, when complementation is performed using a nozzle that ejects the same color ink as the defective nozzle, it is arranged next to the defective nozzle. Complementary recording operation is performed by using a total of four nozzles as complementary target nozzles for every two nozzles.

  Next, complementary recording correction processing using the recording apparatus and recording head configured as described above will be described. This process is executed particularly with the MPU 400, the program ROM 401, the RAM 402, the VRAM 404, the head drive circuit 408, and the like involved.

  FIG. 5 is a functional block diagram showing the flow of correction processing for complementary recording in this embodiment.

  In FIG. 5, the color conversion unit 1 is a part that performs color conversion of RGB 8-bit input image data to CMYK 4-color 8-bit image data, and performs processing such as γ conversion and enlargement / reduction as necessary. Execute. The correction processing unit 2 includes a correction parameter storage unit 21 and an image correction unit 22. The correction parameter storage unit 21 includes a non-discharge continuous index indicating the position of the defective nozzle and the number of continuous nozzles, a complementary color setting index, a distribution coefficient when performing the same color complement, a reference different color complement table when performing the different color complement, Shading data is retained. With reference to these data, correction processing is performed in the different color complementation processing unit 22a, the same color complementation processing unit 22b, and the shading correction processing unit 22c provided in the image correction unit 22. Reference numeral 3 denotes an image processing unit, which performs processing such as binarization, transfers the bitmap data obtained as a result to the head driver 4, drives the recording head according to the data, and outputs an image.

  On the other hand, the discharge failure continuous index and shading data held in the correction parameter storage unit 21 are set by the nozzle correction evaluation unit 5. Evaluation pattern data read by the pattern reading unit (scanner) 6 is input to the nozzle correction evaluation unit 5. The nozzle correction evaluation unit 5 includes an input image adjustment processing unit 51, a defective nozzle detection unit 52, and a shading data creation unit 53 that associate with each nozzle by appropriate rotation and enlargement / reduction processing.

  In outputting an image, first, a defective nozzle detection pattern as shown in FIG.

  The defective nozzle detection area 100 shown in FIG. 1 has 16 lines of 64 pixels long recorded by one nozzle, and each is shifted by one nozzle. In addition, a marker 101 for taking correspondence with the nozzle is provided. In addition, a 50% duty uniform density pattern (5120 × 400 pixels) 102 is also provided in this pattern, and shading data is created in this portion. The marker 101 is provided for specifying the nozzle number, and 10 markers 101 are provided every 512 nozzles. As can be seen from FIG. 1, since there are 32 recording lines in each stage between the markers, there are 320 nozzle lines in each stage, and the overall pattern is overlapped by 16 stages. Yes. Such a pattern is read by a scanner having an optical resolution of 1200 dpi, and defective nozzles are detected.

  A specific defective nozzle detection method is shown below.

  In the image data read by the scanner, the input image adjustment processing unit 51 reads the marker position and converts it into data associated with the nozzle position, and performs appropriate rotation, enlargement / reduction processing, and a pixel equivalent to 600 dpi. Try to take action. Next, the defective nozzle detection unit 52 cuts out a portion corresponding to 5120 × 50 pixels from each stage of the defective nozzle detection pattern, and further sets a portion corresponding to 1 × 50 pixels where it should be as a determination portion. If the density of this portion is ¼ or less of the density of the recording portion, the corresponding nozzle is defective or has a large twist (shift in the ink discharge position), so it is set as a defective nozzle. Further, it is also determined whether the nozzles before and after that are defective nozzles, and the discharge failure continuity index is held in the correction parameter storage unit 21.

  For the image data read by the scanner, the shading data creation unit 53 averages the density of 400 pixels for each nozzle to obtain a density distribution, and creates shading data from this.

  In this way, the undischarge continuous index and shading data of the defective nozzle are set, and preparation for outputting a desired image is completed.

  In this state, the input image data is converted from 8-bit RGB component data into 8-bit CMYK 4-component image data in the color conversion unit 1, and the correction processing unit 2 performs different color complementation, same color complement defective nozzle correction processing, and Shading correction processing is performed.

  The different color complementation in this embodiment is complemented by using black ink for defective nozzles of cyan ink and magenta ink. Further, the nozzle failure of the black ink is complemented by using composite black generated by three colors of cyan ink, magenta ink, and yellow ink. As for the nozzle failure of yellow ink, the difference in brightness between yellow and other colors is large, and the complement position is easily visible when complemented with other colors with low brightness. Do not do it.

  FIG. 6 is a diagram showing an example of a reference different color complementation table in the case of different color complementation with black for cyan.

  Here, the index indicated by s [n] indicates the number of defective nozzles at the nozzles before and after the target defective nozzle, “0” indicates that ink is normally ejected, and “1” indicates isolated. "2" indicates that either the front or back of the target defective nozzle is a defective nozzle, and "3" indicates that the defective nozzle is continuous both before and after the target defective nozzle. It shows that. In addition, when showing the same parameter | index about each color component, it describes with s [c] [n].

  The reference different color complementation table naturally varies depending on the recording medium to be used, the relationship between the recording density and the ink dot size, and the combination of inks. Select and use.

  FIG. 7 is a diagram illustrating a distribution coefficient function indicating a ratio of distributing data to adjacent nozzles, which is an example of a complementary parameter in the same color interpolation. This example is the distribution function of cyan complementary color.

  In FIG. 7, [c] in the distribution function (F_s [c] [r] [tone]) is an index indicating the color, r indicates the relative position of the nozzle to be distributed, and if r = −1. For example, assuming that the nozzle number of the defective nozzle is n, the ratio of distribution to the (n + r) -th nozzle, that is, the previous nozzle indicated by the nozzle number is shown. The range r indicating the relative position of the nozzle is determined by the relative size between the nozzle density and the dot diameter. Further, tone is an input gradation value at a defective nozzle.

  Next, a description will be given of defective nozzle correction processing using the different color complement and the same color complement.

  FIG. 8 is a flowchart showing defective nozzle correction processing.

  Here, one page of image data is taken into the RAM 402, which is a work memory, and each process is performed. First, in step S10, input image data D [c] [n] of all color components for one page of image data, and a discharge failure continuation index s [c] indicating whether or not the nozzle is defective and the number of discharge failures. [n] is read.

  After reading these, the process is sequentially executed for each color component of each pixel. In step S20, it is determined whether the target pixel is a defective nozzle. If it is determined that s [c] [n] = 0, that is, it is not a defective nozzle, the process proceeds to step S50, and only shading correction is performed.

  On the other hand, if s [c] [n] ≠ 0, that is, if it is determined that the nozzle is a defective nozzle, the process proceeds to step S30, and a different color complement process is executed. Here, based on the color (c) of ink ejected by the defective nozzle and its nozzle number (n), a complementary color setting index (cc) indicating a different color to be complemented and a reference different color complement table (F_d [c] [cc ] [s] [tone]) is read from memory. Further, data D [c ′] [n], D [c ″] [n], D [c ′ ″] [n] of other color components in this pixel are referred to.

  Here, c ≠ c ′ ≠ c ″ ≠ c ′ ″.

  The correction of the reference different color complementation table in this embodiment is performed by obtaining the following correction coefficient α and multiplying this by the reference different color complementation table.

  Note that the value of the correction coefficient (α) with respect to the total value of the other color components used in this embodiment is as follows.

α = 1− (Comps / 1020) ² : Comps <510
0.75: Comps ≧ 510
(However, Comps = D '[c'] [n] + D [c ''] [n] + D [c '''] [n])
D '[cc] [n] = D [cc] [n] + (F_d [c] [cc] [s] [D [c] [n]] × α)
FIG. 9 is a diagram showing a change with respect to the total value of the other color components of the correction coefficient α.

  The correction coefficient (α) is set to 0.75 by adding a limit when the total of other color components is twice the value that can be expressed by 8 bits, that is, 510 or more. This is a region of values that are hardly used because the amount of ink to be used is normally limited to about 200% to 300% (the amount of ink in the complementary processing means 2 to 3 times that of normal recording). That is the reason. After correcting the different color complement amount in the different color complement and performing the different color complement process in this way, the process proceeds to step S40, and the same color complement process is performed.

  In the same color complementation, the following processing is performed according to the read distribution coefficient F_s [c] [r] [tone].

D '[c] [n + r] = D [c] [n + r] + D [c] [n] × F_s [c] [r] [D [c] [n]]
However, r = -1, 0, 1.

  After the different color complement and the same color complement processing are performed, the processing proceeds to step S50, and shading correction processing is executed. Further, the process proceeds to step S60 to check whether or not the process for one page of image data has been completed. If the process has not been completed, the process returns to step S20. The process ends.

  The image data corrected in this way is binarized in the image processing unit 3 and converted into bitmap data. In this embodiment, binarization processing is performed by a general error diffusion method. Then, the bitmap data is transferred to the head driver 4 and an image is recorded and output.

  Therefore, according to the embodiment described above, with respect to the image data of a certain color component that should have been handled by the defective nozzle, the different color interpolation amount is corrected by referring to the other color component data of the pixel. Since the image is recorded, appropriate supplementary recording is performed in consideration of the characteristics of the image data to be always recorded. The image obtained in this way is excellent because the non-ejection portion of the ink is not conspicuous.

<Other embodiments>
Here, the yellow component is used as the other color component for cyan data and magenta data, and the correction amount β obtained from the other color component is first reflected in the different color complementation amount in the different color complementation, and the amount that could not be reflected there An example in which the distribution coefficient in the same color complementation is corrected will be described.

  The following description will focus on differences from the above-described embodiment.

  Also in this embodiment, a pattern as shown in FIG. 1 is output for each color in the same manner as in the previous embodiment, and the defective nozzle is obtained. Then, the different color complement and the same color complement correction processing are performed on the defective nozzle. The reference different color complement table when performing different color complement and the distribution coefficient when performing the same color complement are the same as those in the above-described embodiment.

  When the defective nozzle is a nozzle that discharges cyan ink or magenta ink, in this embodiment, the correction amount (β) obtained from other color component data is determined as follows.

β = (D [yellow] [n] / 255) × 0.2 × F_d [cyan] [Bk] [s] [255]
That is, when the density value of the yellow component is maximum (= 255), 20% of the reference different color complement amount is set as the correction amount. After setting the correction amount (β) in this way, a reference different color complement amount is obtained.

  For example, the nth nozzle that discharges cyan ink is a defective nozzle, which is an isolated defective nozzle (s = 1), and the density value of the cyan component discharged from that nozzle and the density value of the yellow component at the same location Are 150 (= D [cyan] [n]) and 130 (= D [yellow] [n]), respectively, and referring to the different color complementation amount shown in FIG. (150/255) × 0.2 × 40.8 ≒ 4. Also, the reference different color complement amount (F_d [cyan] [Bk] [1] [150]) is “5.1”. In this case, since the correction amount is smaller than the complement amount, “1” is added to the yellow component data as the different color complement amount.

  For the same color complementation, no particular correction is made, and the density of the cyan component discharged from the (n−1) th nozzle and the (n + 1) th nozzle is half of the cyan component density value discharged from the defective nozzle (ie, 75). Added to the value.

That is,
D '[cyan] [n-1] = D [cyan] [n-1] + 75,
D '[cyan] [n + 1] = D [cyan] [n + 1] + 75
It is.

  For example, when D [cyan] [n] = 160 and D [yellow] [n] = 220, the correction amount (β) is similarly β = (220/255) × 0.2 × 40.8≈7. Since the reference different color complement amount F_d [cyan] [Bk] [1] [160] is 6.5, the correction amount is larger than the reference different color complement amount.

  In such a case, the different color complement amount is set to “0”, that is, the different color complement is not performed and only the same color complement is corrected. In this modification, the distribution coefficient in the same color complement is as follows.

F'_d [cyan] [1] [tone] = F_d [cyan] [1] [tone]-γ
F'_d [cyan] [-1] [tone] = F_d [cyan] [-1] [tone]-γ
However,
γ = (β- F_d [cyan] [Bk] [s] [D [cyan] [n]]) / (β ₀ × 2)
β ₀ = 0.2 × F_d [cyan] [Bk] [s] [255]
It is.

Therefore, in this case, the distribution coefficient is
F'_d [cyan] [1] [tone] = F'_d [cyan] [-1] [tone] = 0.5−0.01 = 4.99
It is corrected.

  Then, the same color interpolation is performed using the corrected distribution coefficient.

  In this way, the defective nozzle complementing process and the shading correction process are performed for all the pixels, the binarization process is performed in the same manner as in the above-described embodiment, and the bitmap data is generated to perform the complementary recording. Do.

  Therefore, according to the embodiment described above, when the correction amount due to the different color complement is larger than the reference different color complement amount, control is performed so that the same color complement is performed using the nozzle adjacent to the defective nozzle, so the correction amount is large. In this case, more appropriate complementary recording can be realized by performing the same color complementation with a large complementation effect. In the image thus obtained, the non-ejection portion (for example, streaks and density unevenness) of the ink is not conspicuous and is good.

  Further, in the above-described embodiments, the droplets ejected from the recording head are usually ink, and the liquid contained in the ink tank is ink, but the accommodation is not limited to ink. For example, a treatment liquid discharged to the recording medium may be accommodated in the ink tank in order to improve the fixability and water resistance of the recorded image or to improve the image quality.

  The above embodiment includes means (for example, an electrothermal converter or a laser beam) that generates thermal energy as energy used to perform ink ejection, particularly in the ink jet recording system, and the ink is generated by the thermal energy. By using a system that causes a change in the state of recording, it is possible to achieve higher recording density and higher definition.

  Further, although the above embodiment is a full line type recording apparatus using a recording head having a length corresponding to the width of the recording medium, it is a serial type recording apparatus that performs recording by scanning the recording head. May be.

  In addition, as a form of the recording apparatus according to the present invention, a copying apparatus combined with a reader or the like, and a transmission / reception function are provided as an image output terminal of an information processing apparatus such as a computer or the like. It may take the form of a facsimile machine.

It is a figure which shows the stair chart used in order to confirm the ink discharge condition from each nozzle. 1 is a perspective perspective view of a recording apparatus equipped with an ink jet recording head that is a typical embodiment of the present invention. 3 is a block diagram illustrating a configuration of a control circuit of the recording apparatus 110. FIG. FIG. 2 is a diagram illustrating an ink ejection surface showing a nozzle arrangement of recording heads 201 to 204. It is a functional block diagram showing the flow of correction processing for complementary recording. It is a figure which shows an example of the reference | standard different color complementation table in the case of different color complementation in black with respect to cyan. It is a figure which shows the function of the distribution coefficient which shows the ratio which distributes the data to the adjacent nozzle which is an example of the complement parameter in the same color complement of cyan. It is a flowchart which shows a defective nozzle correction process. It is a figure which shows the change with respect to the total value of the other color component of the correction coefficient (alpha).

Explanation of symbols

1 color conversion unit 2 correction processing unit 3 image processing unit 4 head driver 5 nozzle correction evaluation unit 6 pattern reading unit 51 input image adjustment processing unit 52 defective nozzle detection unit 53 shading data creation unit 100 defective nozzle detection pattern 101 marker 102 density uniform Pattern 201-204 Recording head

Claims (8)

A recording method with complementary recording for recording failure by an ink jet recording head that performs color recording using a plurality of colors of ink,
An input process for inputting a predetermined amount of color image data;
A detection step of detecting a defective recording element of the inkjet recording head that performs recording using the color image data;
The value of the image data of the other color component corresponding to the image data of the color component that was to be used for recording with the defective recording element detected in the detection step is examined and used for predetermined different color complementation according to the value. A correction process for correcting the supplementary amount;
A correction step of correcting the value of the color image data for different color complementation using the correction amount corrected in the correction step;
And a recording step of performing recording by the ink jet recording head using the color image data corrected in the correction step.   The recording method according to claim 1, wherein the correcting step further corrects the value of the color image data for a predetermined same color complement to the defective recording element.   The recording method according to claim 1, wherein the correction amount of the complement amount used for the different color complement follows a sum of values of image data of all the other color components. A comparison step of comparing the correction amount of the complement amount used for the different color complementation with the complement amount used for the predetermined different color complementation;
The recording method according to claim 1, further comprising a selection step of selecting either different color complementation or same color complementation according to a comparison result in the comparison step.   The complementary amount used for the different color complementation relates to an ink ejection amount for performing complementary recording using the different color ink from another recording element that ejects different color ink to the recording position by the defective recording element. The recording method according to claim 1.   The complement amount used for the same color complement is a distribution coefficient when distributing the value of multi-value recording data that was to be recorded by the defective recording element to a plurality of recording elements in the vicinity of the defective recording element. The recording method according to claim 1, wherein:   7. The inkjet recording head according to claim 1, further comprising an electrothermal transducer for generating thermal energy applied to the ink in order to eject the ink using thermal energy. The recording method described in 1. A recording apparatus that performs complementary recording using the recording method according to claim 1.

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