JP2012166346A - Image processor, image recorder and image processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: an image processor which is achieved in preferable image recording while being suppressed in influences of the irregularity of density resulting from a non-discharge abnormality (defect) and irregularity resulting from the other factor; an image recorder; and an image processing method.SOLUTION: At least one drawing performance evaluation factor (F) for calculating an evaluation value quantitatively indicating the drawing perform of an image which is recorded by making a nozzle (62) arranged at an inkjet head (60) discharge droplets is acquired, raster image data which indicate a multi-graduation image constituted of a plurality of pigments are acquired, a position on a recording medium (70) of a recorded image is calculated so that the evaluation value acquired by the drawing performance evaluation factor exhibits the best drawing performance with respect to the acquired raster image data, and the raster image data are adjusted so that the image may be recorded at the calculated position above the recording medium.

Description

  The present invention relates to an image processing apparatus, an image recording apparatus, and an image processing method, and more particularly to an image processing technique for correcting a drawing performance of a recorded image.

  An ink jet recording apparatus is known as a general-purpose image recording apparatus. An ink jet recording apparatus records a desired color image on a recording medium by ejecting ink droplets from a number of nozzles provided in an ink jet head.

  In the ink jet type image recording, if nozzle clogging occurs due to thickening of ink or adhesion of foreign matter, it causes ejection failure. When the ejection abnormality occurs, drawing is not performed at a position where a dot should be originally formed, and the image quality is significantly deteriorated.

  In particular, using a full-line type ink jet head provided with nozzles over a length corresponding to the entire width of the recording medium, the recording medium and the ink jet head are operated only once relative to the entire area of the recording medium. In single-pass image recording in which image recording is performed, streaky irregularities occur at positions on the image corresponding to ejection abnormal nozzles.

  Patent Document 1 calculates the number of pixels to which liquid should be ejected for each pixel group assigned to the same nozzle based on image data composed of a plurality of pixels, detects a defective nozzle in which ejection failure occurs, A liquid ejecting method is disclosed in which the position of an image on a medium is adjusted so that the number of pixels carried by a defective nozzle is minimized.

  FIG. 13 is a flowchart illustrating the image processing applied to the liquid ejecting method described in Patent Document 1 in a simplified manner. The flowchart shown in the figure is roughly divided into a process for adjusting the recording position of an image on a medium (steps S200 and S202) and a process for outputting an image (steps S210 to S216).

  In the step of adjusting the recording position of the image on the medium, defective nozzle detection of the inkjet head is executed, and defective nozzle information is acquired (step S200). This defective nozzle information is used for calculating the drawing position adjustment amount (step S202).

  In the step of outputting an image, raster image data is input (step S210), and halftone processing is performed on the input raster image data (step S212). Here, “raster image data” is digital image data having multi-gradation values (for example, 0 to 255) represented in an RGB color space, and halftone processing is multi-gradation image data. Is converted into binary or multi-valued data (gradation value smaller than the original gradation value).

  Based on the halftone image data obtained in the halftone processing step and the defective nozzle information obtained in advance, the position of the image on the medium (drawing position) so that the number of pixels that the defective nozzle takes is minimized. An adjustment amount is calculated (step S202), and the drawing position is adjusted based on the drawing position adjustment amount (step S214).

  Image output (drawing) is executed based on the dot data whose drawing position has been adjusted in this way (step S216), and a drawing image whose drawing position has been adjusted with the influence of defective nozzles suppressed is recorded.

  In addition to the correction method disclosed in Patent Document 1, many methods for correcting droplet ejection by an abnormal ejection nozzle have been proposed. For example, a normal nozzle in the vicinity of the abnormal discharge nozzle is used as a correction nozzle for the abnormal discharge nozzle, and the visibility of streaky irregularities caused by the abnormal discharge nozzle is reduced by increasing the drawing density by the correction nozzle.

  To increase the drawing density, it is conceivable to increase the dot diameter or increase the density gradation value on the image data. Note that the above-mentioned correction method for abnormal discharge nozzles may not be able to correct uneven density due to abnormal discharge nozzles due to the gradation dependence of the correction performance, so this point needs to be considered.

JP 2010-684 A

  The deterioration of the image quality caused by the abnormal ejection nozzle is visually recognized as a stripe-like unevenness on the image. Other non-uniformities recognized as degradation in image quality are due to differences in the solidity of the head modules that make up the inkjet head, non-uniformity in the density of ink that occurs due to non-uniformity in ink ejection (difference in ejection characteristics for each nozzle), Examples include vibration unevenness caused by vibration.

  The liquid ejecting method described in Patent Document 1 adjusts the image position while paying attention only to the density unevenness caused by the defective nozzle, but does not consider the occurrence of other unevenness as described above.

  In addition, the liquid ejection method described in Patent Document 1 uses an integrated value of the number of pixels of a pixel group assigned to a defective nozzle as an evaluation target. To calculate the number of pixels of the pixel group assigned to the defective nozzle, halftone processing (quantization processing) is performed on the original image data (data representing the density value of each pixel in multiple gradations) such as a raster image format. ), Etc., to obtain dot position information.

  However, when the defective nozzle correction process is performed based on the dot position information, the density information of each pixel cannot be used, and the influence of unevenness other than the uneven density due to the defective nozzle cannot be considered.

  The present invention has been made in view of such circumstances, and an image processing apparatus that realizes preferable image recording in which the influence of uneven density due to abnormal discharge (defective) nozzles and unevenness due to other factors is suppressed. It is another object of the present invention to provide an image recording apparatus and an image processing method.

  In order to achieve the above object, an image processing apparatus according to the present invention provides a drawing performance evaluation for obtaining an evaluation value that quantitatively represents a drawing performance of an image recorded by operating a recording element provided in a recording head. A drawing performance evaluation function acquisition unit that acquires at least one function, a raster image data acquisition unit that acquires raster image data representing a multi-tone image composed of a plurality of pixels, and the acquired raster image data On the other hand, the drawing position calculating means for calculating the position of the recorded image on the recording medium so that the evaluation value obtained by the stored drawing performance evaluation function shows the best drawing performance, and the calculated And a drawing position adjusting means for adjusting the raster image data so that an image is recorded at a position on the recording medium.

  According to the present invention, a rendering performance function for calculating an evaluation value that quantitatively represents rendering performance is applied to raster image data to obtain the evaluation value, and the evaluation value has the best rendering performance. As shown, the position of the recorded image on the recording medium is calculated, and the raster image data is adjusted so that the recorded image is recorded at the calculated position, so that preferable image recording in which various irregularities are suppressed is performed. Is possible.

1 is a block diagram showing a schematic configuration of an image processing apparatus according to an embodiment of the present invention. 6 is a flowchart showing a control flow of an image processing method according to an embodiment of the present invention. Flowchart of the drawing position adjustment process shown in FIG. Explanatory drawing of adjustment for density unevenness caused by solid difference of recording head Explanatory drawing of adjustment for unevenness caused by abnormal discharge nozzle Illustration of adjustment for unevenness caused by vibration Explanatory drawing of the application example which concerns on embodiment of this invention 1 is an overall configuration diagram of an ink jet recording apparatus to which an image processing apparatus (method) according to the present invention is applied. The top view which shows schematic structure of the printing part shown in FIG. Plane perspective view showing an example of the structure of the inkjet head shown in FIG. Explanatory drawing which shows the example of nozzle arrangement | positioning of the inkjet head shown in FIG. The block diagram which shows the structure of the control system of the inkjet recording device shown in FIG. A flowchart showing an image processing method according to the prior art

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

[Description of Image Processing Apparatus (Method)]
FIG. 1 is a block diagram showing a schematic configuration of an image processing apparatus according to an embodiment of the present invention. The image processing apparatus 10 shown in FIG. 1 converts raster image data (multi-tone digital image data) into binary or multi-value halftone image data (data representing dot information) in image recording by an inkjet method. According to the drawing performance evaluation function, the raster image data is subjected to image position adjustment processing on the recording medium, and halftone image data is output.

  That is, the image processing apparatus 10 includes a raster image data input unit 12 to which raster image data (for example, digital serial data represented by gradation values from 0 to 255 expressed in an RGB color space) is input; Based on the drawing position adjustment amount obtained using the drawing performance evaluation function, the drawing position adjustment processing unit 14 that performs the drawing position adjustment process on the raster image data, and the raster image data with the drawing position adjusted. On the other hand, a density unevenness correction processing unit 16 that is subjected to density unevenness correction processing due to individual differences of the recording heads, and a discharge abnormal nozzle correction processing unit 18 that is subjected to correction processing of abnormal discharge nozzles (abnormal recording elements), The halftone processing unit 20 that performs halftone processing on the raster image data after correction processing, and halftone image data after halftone processing And it is configured to include a half-tone image data output section 22 to be output, the.

  The image processing apparatus 10 also includes an evaluation function acquisition unit 30 that acquires a drawing performance evaluation function or a drawing performance evaluation function (unevenness evaluation function) for each factor that constitutes the drawing performance evaluation function, and the acquired drawing performance evaluation. The evaluation value of the drawing performance evaluation function calculated based on the drawing performance evaluation function for each function or factor is calculated, and the adjustment amount of the drawing position of the recorded image is calculated so that the evaluation value shows the best drawing performance. A drawing position adjustment amount calculation unit 32. In addition, the form provided with the nonuniformity evaluation function memory | storage part in which the acquired nonuniformity evaluation function is memorize | stored is also possible.

  As will be described in detail later, the “drawing performance evaluation function” is applied to derivation of an evaluation value for quantitatively evaluating the drawing performance (drawing unevenness) generated in the recorded image recorded on the recording medium. In order to consider the influence of the type of unevenness of drawing and the dependency of the correction performance of the unevenness of drawing on the image gradation, the raster image distribution (raster image data) I is processed and derived.

  That is, it is possible to grasp whether the drawing performance is good or bad by comparing the evaluation values obtained by the drawing performance evaluation function.

  The drawing performance evaluation function F (X, Y) is expressed by the following equation (1).

  Here, (X, Y) is a position on the recorded image represented by the orthogonal coordinate system, and (x, y) is a coordinate in the image represented by the orthogonal coordinate system. For example, there is a form in which X (x) is the nozzle arrangement direction orthogonal to the relative conveyance direction of the recording medium and the recording head, and Y (y) is the relative conveyance direction of the recording medium and the recording head.

Drawing performance evaluation function for each factor (hereinafter sometimes referred to as unevenness evaluation function) M _n (X, Y, I) is unevenness of drawing when the position of the recorded image is moved to (X, Y). This is a function for evaluating the degree of occurrence and correction performance. n is a subscript representing the type of unevenness (attribute, generation factor). The subscript n of the unevenness evaluation function _Mn may be represented by a positive integer attached in order from 1, or may be represented by a symbol, character, or character string indicating the type of unevenness.

As shown in the above equation (1), the drawing performance evaluation function F (X, Y) matches the unevenness evaluation function M corresponding to the unevenness when the kind of unevenness in drawing is one, and the type of unevenness in drawing is as follows. In the case of multiple, the unevenness evaluation function M _n (X, Y, I) for each type of drawing unevenness is expressed as a combined function.

  The position (X, Y) of the recorded image on the recording medium is optimized by minimizing the evaluation value obtained from the drawing performance evaluation function F (X, Y) shown in the above equation (1). . That is, the drawing position adjustment amount calculation unit 32 calculates the position (X, Y) of the recorded image on the recording medium that minimizes the evaluation value calculated based on the drawing performance evaluation function F (X, Y). Based on the position (X, Y) of the recorded image, the position of the recorded image on the raster image data is adjusted.

  The form for adjusting the position of the recording image in the raster image data may be a form for changing the writing position of the recording image, or a form for changing the distribution of data corresponding to the recording image in the raster image data.

  There may be a form in which the image is rotated by a minute angle. For example, when a straight line is drawn, if the conveyance direction of the recording medium and the direction of stripe-like density unevenness (white stripes) due to ejection abnormality are completely parallel, the stripe-like density unevenness becomes conspicuous. When the straight line is rotated by a minute angle and shifted with respect to the recording medium conveyance direction, the influence is reduced, and the visibility of streaky density unevenness can be reduced.

  The drawing performance evaluation function F (X, Y) is derived for each type of drawing unevenness corresponding to the type of drawing unevenness for each device (for each recording head), and corresponds to the type of device (recording head) and drawing unevenness. Attached.

  FIG. 2 is a flowchart showing a flow of an image processing method applied to the image processing apparatus 10 shown in FIG.

  When the raster image data is input (step S12), the input raster image data 40 is subjected to color conversion processing (RGB → CMY) and gamma correction processing, and then the drawing position adjustment processing unit of FIG. 14, the position of the recorded image on the recording medium is adjusted so that the occurrence of uneven drawing is suppressed to the maximum and the drawing performance is optimized (step S14 in FIG. 2).

  Next, the density unevenness correction processing unit 16 in FIG. 1 corrects the density unevenness caused by the printing characteristics (solid difference of the printhead) for each nozzle (printing element) for the raster image data whose drawing position is adjusted. Processing is performed (step S16 in FIG. 2).

  Further, the ejection abnormal nozzle correction processing unit 18 in FIG. 1 performs a process of correcting the unevenness of drawing (streaky unevenness) due to the abnormal ejection nozzle for the raster image data whose drawing position is adjusted (FIG. 2). Step S18).

  The term “discharge abnormal nozzle” as used herein refers to a non-discharge nozzle that cannot discharge liquid droplets, and a nozzle that can discharge liquid droplets but generates abnormal discharge amounts or abnormal discharge directions. This is a concept that includes

  As described above, the raster image data that has undergone the drawing position adjustment step (step S14), the density unevenness correction processing step (step S16), and the ejection abnormal nozzle correction processing step (step S18) is the halftone processing unit 20 in FIG. , Halftone processing is performed (step S20), and halftone image data 42 is generated.

  The halftone image data 42 includes binary or multivalued dot information. For example, if one pixel is expressed by one dot, two gradations can be expressed, and if one pixel is expressed by four dots, four gradations can be expressed. A drive signal (drive voltage) for operating the inkjet head is generated based on dot information represented by the halftone image data (details will be described later).

  The inkjet head is operated using the drive signal generated in this way, and the recording (drawing) image 44 with the drawing position adjusted is output (step S22).

FIG. 3 is a flowchart showing details of the drawing position adjusting step (step S14) shown in FIG. As shown in the figure, based on n pieces (n is a positive integer) drawing unevenness information 1, 2,..., N (shown with reference numerals 50-1, 50-2,..., 50-n). N nonuniformity evaluation functions M (M _{1 to} M _n , _denoted by reference numerals 52-1 to 52-n) are generated (steps S50 to S54), and the n nonuniformity evaluation functions are generated. At least one unevenness evaluation function M is selectively acquired from M _{1 to} M _n .

  When two or more unevenness evaluation functions M are acquired, a drawing performance evaluation function F that is a composite function of the acquired multiple unevenness evaluation functions M is generated (step S30). The drawing position adjustment amount 56 (x−X, y−y) is calculated so that the evaluation value calculated by the drawing performance evaluation function F illustrated with reference numeral 54 is minimized (step S32). Based on the position adjustment amount 56, the drawing position on the raster image data is adjusted (step S34).

Note that the creation process of drawing unevenness information 50-1 to 50-n unevenness evaluation function _M 1 based on _~M n _(52-1~52-n), the form and executed in the image processing apparatus, a plurality of uneven evaluation functions A form in which a drawing performance evaluation function F (54) created in advance based on M is acquired is also possible.

[Specific example of unevenness evaluation function M]
Next, a specific example of the unevenness evaluation function M will be described. In the following description, an orthogonal coordinate system (x, y) is used as a parameter of the unevenness evaluation function. In this example, the x direction is a substantial arrangement direction of nozzles orthogonal to the relative movement direction between the recording medium and the recording head, and the y direction is the relative movement direction between the recording medium and the recording head.

  In an embodiment having a full-line type recording head, the x direction is a substantial nozzle arrangement direction (the width direction of the recording medium), and the y direction is the relative movement direction of the recording medium and the recording head (the conveyance direction of the recording medium). It is. On the other hand, in the embodiment having a serial type recording head, the x direction is the nozzle arrangement direction, and the y direction is the scanning direction of the recording head (the width direction of the recording medium).

(Explanation of _density unevenness evaluation function M _density caused by individual difference of recording head)
FIGS. 4A and 4B are explanatory diagrams of density unevenness caused by individual differences in the recording head. FIG. 4A schematically shows a state in which density unevenness due to the solid difference of the recording head 60 is generated.

  The recording head 60 is a full-line recording head, and has a structure in which a plurality of nozzles 60 are arranged in a line along the x direction. Among the plurality of nozzles 62, the ejection characteristics of the third nozzle 64 and the fourth nozzle 65 from the left in the figure are different from those of the other nozzles 62, and the flight direction tends to be shifted.

  Then, the positions of the dots formed by the nozzles 64 and 65 are shifted, and density unevenness 70 occurs in the recorded image 68 formed at the coordinates (x, y) on the recording medium 66. Note that the coordinates (x, y) of the recorded image 68 on the recording medium 66 are the coordinates of the upper left corner in FIG.

  The individual difference of the recording head includes the individual difference of the head modules (see FIGS. 6 and 7) constituting the recording head, the variation in the mounting of the head module, the difference in the ink ejection characteristics (variation in the machining of the nozzle), and the like. It is done.

  In general, since there are a plurality of nozzles 64 having different ejection characteristics, periodic density unevenness occurs due to the ejection characteristics. If the spatial frequency of the uneven density is in a range that can be visually recognized by the human eye, the quality of the recorded image is significantly deteriorated.

  In order to correct the density unevenness 70 illustrated in FIG. 4A, a test chart for measuring the density unevenness is output, and the test chart for measuring the density unevenness is read by the optical reading device. Information is measured, and density unevenness correction processing is executed based on the measured density unevenness information.

  However, the density unevenness correction performance may deteriorate at the position of the connecting portion (overlap portion) between the head modules, the position where the abnormal discharge nozzles are dense, and the like, and sufficient correction performance may not be exhibited. .

Therefore, in order to avoid the use of a nozzle corresponding to a position where the density unevenness correction performance is likely to be reduced, a density unevenness evaluation function M _density (X, Y, I) representing the density unevenness correction performance is prepared.

The density unevenness evaluation function M _Density (X, Y, I) is expressed by the following equation (2).

C _Density (x, y, liquid, I (x-X, y-Y, liquid)) in the above formula (2) is a certain coordinate (x, y), liquid type (liquid), and gradation (I). The evaluation function represents density unevenness correction performance. The evaluation function C _Density is the design information of the head module (nozzle flying curve information, nozzle diameter variation information, nozzle module (within the head) position information (information about the number of nozzles in the module, Phase information, etc.), occurrence information of abnormal discharge nozzles (position information of abnormal discharge nozzles, spacing information between abnormal discharge nozzles, deviation amount of ink discharge amount (dot diameter) from each nozzle, etc.) Based on the above, a lookup table may be created in advance.

  The above-described expression (2) is given to expression (1) to minimize F (X, Y), so that the recorded image on the recording medium 66 in which the uneven density correction performance due to the individual difference of the recording head is taken into consideration. 68 optimum positions (X, Y) are determined.

  FIG. 4B schematically shows a state in which the recorded image 68 is moved to the optimum position (X, Y) on the recording medium 66. The generation position of density unevenness 70 (illustrated by a one-dot broken line) due to the individual difference of the recording head 60 is avoided, and the optimum position (X, Y) of the recorded image 68 is determined.

  Although it seems that the density unevenness due to the ejection characteristics of the nozzles 65 has not been eliminated even by adjusting the position of the recording image, the unevenness of density due to the ejection characteristics of the nozzles 64 can be suppressed to visually recognize the unevenness. Is deteriorating. Moreover, the visibility of the density unevenness can be further reduced by the effect of the density unevenness correction.

(Explanation of unevenness evaluation function M _nzl caused by ejection abnormal nozzle)
Next, a _{non-uniformity} evaluation function M _nz1 for _{non-uniformity} caused by abnormal ejection nozzles will be described. In the following description, the same or similar components as those described above are denoted by the same reference numerals, and the description thereof is omitted.

  FIGS. 5A and 5B are explanatory diagrams of unevenness caused by abnormal ejection nozzles. FIG. 5A schematically shows a state in which streak-like unevenness 72 caused by the abnormal ejection nozzle 64 ′ is generated.

  Either raster image data or halftone image data is used to increase the density value of pixels corresponding to normal nozzles located around the abnormal discharge nozzles in order to correct streaky irregularities 72 caused by such abnormal discharge nozzles. Is corrected.

  However, when the abnormal discharge nozzles are densely packed, the correction performance is deteriorated, and the sufficient correction performance may not be exhibited.

Therefore, in order to avoid the use of the nozzle corresponding to the position where the correction performance is likely to be reduced as much as possible, the unevenness evaluation function M _nzl (X, Y, I) representing the occurrence degree of the abnormal discharge nozzle and the correction performance of the abnormal discharge nozzle. ) Is prepared. The unevenness evaluation function M _nzl (X, Y, I) is expressed by the following equation (3).

  In the above equation (3), N (x, color) is a weighting value given to each nozzle based on the information of the ejection abnormal nozzle and the coordinates (nozzle position) (x) and color (head) (color) are It becomes a parameter.

Further, C _nzl (x, liquid, I (x−X, y−Y, liquid)) represents ejection abnormal nozzle correction performance at a certain nozzle position (x), liquid type (liquid), and gradation (I). An evaluation function.

The weighting value N (x, color) and the evaluation function C _nzl (x, liquid, I) should be prepared as a lookup table by measuring the ejection abnormal nozzle information and the correction performance of the ejection abnormal nozzle in advance. Good.

  By giving the above equation (3) to equation (1) and minimizing F (X, Y), the optimum position (X, Y) of the print image on the print medium in consideration of the correction performance of the ejection abnormal nozzle is considered. ) Is required.

  FIG. 5B schematically shows a state in which the recorded image 68 is moved to the optimum position (X, Y) on the recording medium 66. The occurrence position of streaky irregularities 72 (illustrated by a one-dot broken line) due to the abnormal ejection nozzle 64 ′ is avoided, and the optimum position (X, Y) of the recorded image 68 is determined.

(Explanation of the vibration unevenness evaluation function M _vibe )
Depending on the design of the image recording process and the apparatus, vibration (resonance phenomenon) inherent to the process (apparatus) may occur during image recording. This vibration may occur both in the recording medium conveyance direction (for example, the y direction) and in a direction orthogonal to the recording medium conveyance direction (for example, the x direction). Due to the occurrence of such vibration, unevenness (vibration unevenness) may occur in the recorded image.

  Since most of the vibration unevenness occurs due to the periodicity of the image recording process and the periodicity of the apparatus operation, the occurrence position of the vibration unevenness on the recording medium is relatively stable (high reproducibility). In addition, since the influence of vibration unevenness generated on the recording medium tends to increase as the end of the recording medium is reached, the occurrence position of vibration unevenness can be specified.

FIG. 6A schematically shows a recorded image 68 on the recording medium 66 in which the vibration unevenness 76 along the x direction occurs. The y-coordinate of the vibrating unevenness 76 and _{y 1.}

The vibration unevenness evaluation function M _vibe representing the degree of occurrence of such vibration unevenness is expressed by the following equation (4).

C _vibe (x, y, liquid, I (x-X, y-Y, liquid)) in the above equation (4) is a parameter of coordinates (x, y), liquid type (liquid), and gradation (I). Is an evaluation function representing the degree of occurrence of vibration unevenness.

  By giving the above equation (4) to equation (1) and minimizing F (X, Y), the optimum position (X, Y) of the recorded image on the recording medium in consideration of the degree of occurrence of vibration unevenness. Is required.

FIG. 6B schematically shows a state in which the recorded image 68 is moved to the optimum position (X, Y) on the recording medium 66. The generation position y ₁ (illustrated by a one-dot broken line) of the vibration unevenness 76 is avoided, and the optimum position (X, Y) of the recorded image 68 is determined.

In addition to the specific example of the unevenness evaluation function M described above, if the unevenness can identify the position (x, y) on the recording medium, an evaluation function (C _density, etc.) representing the degree of occurrence of the unevenness and the correction performance. The unevenness evaluation function M is created based on the above, and the unevenness correction function M is given to the above equation (1) to minimize F (X, Y). It is possible to determine the optimum position (X, Y) of the recorded image on the considered recording medium.

  According to the image processing apparatus and the image processing method configured as described above, the drawing position adjustment amount (X, Y) in which the drawing performance is optimized by the calculation of the drawing performance evaluation function F (unevenness evaluation function M) generated in advance. ) Adjusts the raster image data, so that the image deterioration is further suppressed as compared with the image processing in which the position of the recorded image is adjusted with respect to the halftone image data (halftone image distribution) after the halftone processing. It becomes possible.

  In particular, by targeting raster image data, it is possible to consider density unevenness due to ejection characteristics that cannot be considered when halftone image data is targeted.

[Application example]
Next, an application example of raster image data adjustment processing based on the drawing performance evaluation function F (X, Y) will be described. In this application example, an example applied to imposition (page allocation) will be described.

  FIGS. 7A and 7B are explanatory views schematically showing a position adjustment process of a recorded image according to this application example.

  FIG. 7A shows four recording images 68-1, 68-2, 68-3, 68- corresponding to an A4 cut size (440 mm × 312 mm) on a recording medium 66 having a full size size of Kiku (939 mm × 639 mm). The state in which 4 is formed is shown.

  A streak-like unevenness 74 is generated due to an abnormal discharge nozzle (indicated by reference numeral 64 'in FIG. 5) indicated by a broken line with reference numeral 74 in FIG. The stripe-shaped unevenness 74 significantly deteriorates the quality of the recorded images 68-1 and 68-3.

  In the position adjustment processing of the recorded image according to this application example, the recorded image 68-1 is moved to the position shown in the figure with the reference numeral 68'-1, and the recorded image 68-3 is attached with the reference numeral 68'-3. As shown in FIG.

  When the number of imprinted recording images is i, the drawing performance evaluation function F is expressed by the following equation (5).

By minimizing F (X ₁ Y ₁ ,..., X _i Y _i ) in the above formula (5), the recorded images 68-1, 68-2 on the recording medium 66 in which the degree of unevenness is taken into consideration. The optimal positions (X ₁ Y ₁ ,..., X _i Y _i ) of 68-3 and 68-4 are obtained.

In the above formula (5), the unevenness evaluation function M _n is obtained in advance for each cause of unevenness. For example, the unevenness evaluation function M _density due to the individual difference of the print head, the abnormal discharge nozzle, and the like. The unevenness evaluation function M _nzl caused by, the unevenness evaluation function M _vibe caused by vibration, and the like are appropriately used.

  In FIG. 7B, the recorded image 68-1 is adjusted to the position denoted by reference numeral 68′-1 so as to avoid the use of the abnormal ejection nozzle shown in FIG. Is schematically shown in a state adjusted to a position denoted by reference numeral 68'-3.

  In the example illustrated in FIG. 7B, an example in which only the recorded images 68-1 and 68-3 affected by the unevenness are moved is illustrated, but four recorded images 68-1, 68-2 are illustrated. A mode in which 68-3 and 68-4 are moved collectively (as one image) is also possible.

  According to this application example, when a plurality of recorded images 68 are formed on a single recording medium 66 using the drawing performance evaluation function F, the position of each recorded image is avoided while avoiding uneven positions on the recording medium 66. Therefore, the drawable space of the recording medium 66 can be used effectively.

[Description of Image Recording Device]
As an example of an image recording apparatus to which the above-described image processing apparatus (method) is applied, an ink jet recording apparatus that forms a color image on a recording medium by discharging KCMY color ink from a plurality of nozzles will be described.

(overall structure)
FIG. 8 is an overall configuration diagram of an inkjet recording apparatus 100 which is an embodiment of the image recording apparatus according to the present invention.

  The inkjet recording apparatus 100 shown in FIG. 1 has a recording medium conveyance unit 104 that holds and conveys a recording medium 102, and a recording medium 102 that is held by the recording medium conveyance unit 104. ), A printing unit 106 including inkjet heads 106K, 106C, 106M, and 106Y that discharge color inks corresponding to M (magenta) and Y (yellow).

  The recording medium conveyance unit 104 includes an endless conveyance belt 108 in which a large number of suction holes (not shown) are provided in a recording medium holding area where the recording medium 102 is held, and a conveyance roller (drive) around which the conveyance belt 108 is wound. Rollers and driven rollers) 110 and 112 and the back side of the conveyance belt 108 in the recording medium holding area (the surface opposite to the recording medium holding surface on which the recording medium 102 is held) are provided in the recording medium holding area. A chamber 114 that generates a negative pressure in a suction hole (not shown) and a vacuum pump 116 that generates a negative pressure in the chamber 114 are included.

  The carry-in unit 118 into which the recording medium 102 is carried is provided with a pressing roller 120 for preventing the recording medium 102 from floating, and the discharge roller 122 from which the recording medium 102 is discharged is also provided with a pressing roller 124. It has been.

  The recording medium 102 carried in from the carry-in unit 118 is applied with negative pressure from the suction holes provided in the recording medium holding area, and is held in the recording medium holding area of the conveyance belt 108.

  On the conveyance path of the recording medium 102, a temperature adjusting unit 126 for adjusting the surface temperature of the recording medium 102 to a predetermined range is provided on the upstream side of the printing unit 106 (upstream side in the recording medium conveyance direction), and the printing unit. A reading device (reading sensor) 128 for reading an image recorded on the recording medium 102 is provided on the rear side of the recording medium 106 (on the downstream side in the recording medium conveyance direction).

  The recording medium 102 carried in from the carry-in section 118 is sucked and held in the recording medium holding area of the conveyor belt 108 and is subjected to temperature adjustment processing by the temperature adjustment section 126, and then image recording is performed in the printing section 106.

  The recording medium 102 on which the image is recorded is ejected from the ejecting unit 122 after the recorded image (test pattern) is read by the reading device 128.

(Composition of printing part)
FIG. 9 is a plan view illustrating a schematic configuration of the printing unit 106. Printing section 106 shown in the figure, a plurality of nozzles over the length _{L N} of greater than the entire width _{L M} of the recording medium 102 (shown by a reference numeral 150 in FIG. 11) is arranged a full-line type inkjet head 106K, 106C, 106M, and 106Y are provided.

  The inkjet heads 106K, 106C, 106M, and 106Y are arranged in this order from the upstream side in the recording medium conveyance direction. A recorded image can be recorded over the entire area of the recording medium 102 by a single-pass method in which the full-line inkjet heads 106K, 106C, 106M, and 106Y and the recording medium 102 are relatively moved once.

  The printing unit 106 is not limited to the above-described form. For example, the inkjet head 106 corresponding to LC (light cyan) or LM (light magenta) may be provided. Further, the arrangement order of the inkjet heads 106K, 106C, 106M, and 106Y can be changed as appropriate.

(Inkjet head structure)
Next, an example of the structure of the inkjet heads 106K, 106C, 106M, and 106Y provided in the printing unit 106 will be described. Since the structures of the inkjet heads 106K, 106C, 106M, and 106Y corresponding to the respective colors are common, the inkjet head (hereinafter also simply referred to as “head”) is denoted by reference numeral 140 as a representative thereof. And

  FIG. 10 is a schematic configuration diagram of the inkjet head 140, which is a diagram (a plan perspective view of the head) of the recording surface of the recording medium as viewed from the inkjet head 140. FIG. The head 140 shown in the figure forms a multi-head by connecting n head modules 142-j (j is an integer from 1 to m) in a line along the longitudinal direction of the head 140. Each head module 142-j is supported by head covers 144 and 146 from both sides of the head 140 in the short direction. Although illustration is omitted, a multi-head can be configured by arranging the head modules 142 in a staggered manner.

  The head module 142-j constituting the head 140 has a plane shape of a substantially parallelogram, and an overlap portion is provided between adjacent sub heads. The overlap portion is a connecting portion of the sub heads, and is formed by nozzles in which adjacent dots belong to different sub heads in the arrangement direction of the head modules 142-j.

  FIG. 11 is a perspective plan view showing the nozzle arrangement of the head module 142-j. As shown in the figure, each head module 142-j has a structure in which the nozzles 150 are two-dimensionally arranged, and the head including the head module 142-j is a so-called matrix head. .

  The head module 142-j illustrated in FIG. 11 includes a number of nozzles 150 along a column direction W that forms an angle α with respect to the sub-scanning direction S and a row direction V that forms an angle β with respect to the main scanning direction M. It has an aligned structure, and the substantial nozzle arrangement density in the main scanning direction M is increased.

  In FIG. 11, nozzle groups (nozzle rows) arranged along the row direction V are denoted by reference numeral 152, and nozzle groups (nozzle rows) arranged along the column direction W are denoted by reference numeral 154. ing.

  As another example of the matrix arrangement of the nozzles 150, there is a configuration in which a plurality of nozzles 150 are arranged along a row direction along the main scanning direction M and a column direction oblique to the main scanning direction M.

  In this example, an example in which a full-line type recording head is provided is illustrated. However, a short inkjet head is scanned in the width direction on the recording medium 102 to perform image recording in the same direction, and one time in the same direction. When the image recording is completed, the recording medium 102 is moved by a predetermined amount in a direction orthogonal to the scanning direction of the inkjet head, and the operation of performing the image recording while scanning the inkjet head for the next area is repeated, and the recording medium 102 is repeated. It is also possible to apply a serial system that records images over the entire area.

  The ink jet head ejection method shown in this example may be a piezoelectric method that utilizes the flexural deformation of the piezoelectric element, or a thermal method that utilizes the film boiling phenomenon of ink in the liquid chamber communicating with the nozzle. Also good.

  A recording element in the piezoelectric system has a form including a nozzle, a pressure chamber communicating with the nozzle, and a piezoelectric element formed on a wall constituting the pressure chamber. In addition, the recording element in the thermal method includes a nozzle, a liquid chamber communicating with the nozzle, and a heating element (heater) for heating the liquid in the liquid chamber.

(Control system configuration)
Next, a control system of the ink jet recording apparatus 100 shown in this example will be described. FIG. 12 is a block diagram illustrating a schematic configuration of a control system of the inkjet recording apparatus 100.

  The inkjet recording apparatus 100 includes a communication interface 170, a system control unit 172, a conveyance control unit 174, an image processing unit 176, a head drive unit 178, and an image memory 180 and a ROM 182.

  The communication interface 170 is an interface unit that receives raster image data sent from the host computer 184. As the communication interface 170, a serial interface such as USB (Universal Serial Bus) may be applied, or a parallel interface such as Centronics may be applied. The communication interface 170 may include a buffer memory (not shown) for speeding up communication.

  The system control unit 172 includes a central processing unit (CPU) and its peripheral circuits, and functions as a control device that controls the entire inkjet recording apparatus 100 according to a predetermined program, and also functions as an arithmetic device that performs various calculations. Further, it functions as a memory controller for the image memory 180 and the ROM 182.

  That is, the system control unit 172 controls each unit such as the communication interface 170 and the conveyance control unit 174, performs communication control with the host computer 184, read / write control of the image memory 180 and ROM 182 and the like. A control signal to be controlled is generated.

  Image data sent from the host computer 184 is taken into the ink jet recording apparatus 100 via the communication interface 170, and is subjected to predetermined image processing by the image processing unit 176.

  The image processing unit 176 has a signal (image) processing function for performing various processing and correction processes for generating a print control signal from the image data. The generated print data (dot data) is transferred to the head drive unit. 178 is a control unit to be supplied to

  The recorded image position adjustment process for the raster image data described above is executed by the image processing unit 176 in FIG. That is, the communication interface 170 corresponds to the raster image data input unit 12 and the unevenness evaluation function acquisition unit 30 in FIG. 1, and the image processing unit 176 in FIG. 12 includes the drawing position adjustment processing unit 14 in FIG. This corresponds to the unit 16, the ejection abnormal nozzle correction processing unit 18, the halftone processing unit 20, the halftone image data output unit 22, and the drawing position adjustment amount calculation unit 32.

  When required signal processing is performed in the image processing unit 176, the ejection droplet amount (droplet ejection amount) and ejection of the inkjet head 140 via the head driving unit 178 based on the print data (halftone image data). Timing control is performed.

  Thereby, a desired dot size and dot arrangement are realized. The head driving unit 178 shown in FIG. 12 may include a feedback control system for keeping the driving conditions of the inkjet head 140 constant.

  The conveyance control unit 174 controls the conveyance timing and conveyance speed of the recording medium 102 (see FIGS. 8 and 9) based on the print data generated by the image processing unit 176. 12 includes a motor that drives the drive roller 110 (112) of the recording medium conveyance unit 104 that conveys the recording medium 102, and the conveyance control unit 174 functions as a driver of the motor. Yes.

  An image memory (temporary storage memory) 180 functions as temporary storage means for temporarily storing image data input via the communication interface 170, a development area for various programs stored in the ROM 182 and a calculation work area for the CPU. (For example, a work area of the image processing unit 176). As the image memory 180, a volatile memory (RAM) capable of sequential reading and writing is used.

  The ROM 182 stores programs executed by the CPU of the system control unit 172, various data necessary for control of each unit of the apparatus, control parameters, and the like, and data is read and written through the system control unit 172. The ROM 182 is not limited to a memory made of a semiconductor element, and a magnetic medium such as a hard disk may be used. Alternatively, a removable storage medium that includes an external interface may be used.

  The reading device 128 is an image sensor (CCD line sensor) that reads an image (test chart) on the conveyance path of the recording medium 102, and a predetermined signal such as nozzle removal, amplification, waveform shaping, or the like on the read signal output from the image sensor. And a signal processing unit that performs processing.

  A test chart formed in a margin or the like of the recording medium 102 is read by the reading device 128, and the presence / absence of ejection abnormality of each nozzle is determined based on the reading result. A nozzle in which an abnormal discharge has occurred is registered as an abnormal discharge nozzle. When the number of abnormal ejection nozzles exceeds a predetermined number, maintenance of the inkjet head 140 is performed.

  In the ink jet recording apparatus 100 provided with the reading device 128, the ejection abnormal nozzle can be periodically detected, and the information on the ejection abnormal nozzle can be updated as needed. That is, a test chart for detecting ejection abnormal nozzles is output from the inkjet head 140 at every image formation, between jobs, and every predetermined period, the test chart is read by the reading device 128, and ejection abnormal nozzles are detected based on the reading results. Yes.

  The parameter storage unit 190 stores various control parameters necessary for the operation of the inkjet recording apparatus 100. The system control unit 172 appropriately reads out parameters necessary for control and updates (rewrites) various parameters as necessary.

  The parameter storage unit 190 functions as a storage unit that stores the unevenness evaluation function M (drawing performance evaluation function F) described above and a storage unit that stores ejection abnormal nozzle information. In other words, the unevenness evaluation function M (drawing performance evaluation function F) acquired via the communication interface 170 is stored in the parameter storage unit 190 via the system control unit 172, and is appropriately read according to the image processing in the image processing unit 176. It is.

  The program storage unit 192 is a storage unit that stores a control program for operating the inkjet recording apparatus 100. When the system control unit 172 (or each unit of the device) executes control of each unit of the device, a necessary control program is read from the program storage unit 192, and the control program is appropriately executed.

  The program storage unit 192 can store a program for executing the image processing method for adjusting the position of the recorded image on the recording medium 102 and a program for executing another image processing method. .

  In this example, ink-jet type image recording in which a color image is recorded on a recording medium by ejecting ink droplets from an ink-jet head having a plurality of nozzles is illustrated, but the scope of application of the present invention is not limited thereto. The present invention can also be applied to electrophotographic image recording using a recording head including an LED element as a recording element, and other types of image recording.

  As described above, the image processing apparatus, the image recording apparatus, and the image processing method according to the embodiment of the present invention have been described in detail. However, the above-described configuration can be appropriately changed without departing from the gist of the present invention.

[Appendix]
As will be understood from the description of the embodiments of the invention described in detail above, the present specification includes disclosure of various technical ideas including at least the invention described below.

  (Invention 1): A drawing performance evaluation function for obtaining at least one drawing performance evaluation function for obtaining an evaluation value quantitatively representing the drawing performance of an image recorded by operating a recording element provided in the recording head. An acquisition unit; a raster image data acquisition unit that acquires raster image data representing a multi-tone image composed of a plurality of pixels; and the acquired drawing performance evaluation function for the acquired raster image data. A drawing position calculating means for calculating a position of the recorded image on the recording medium, and an image is recorded at the calculated position on the recording medium so that the evaluation value obtained by An image processing apparatus comprising: a drawing position adjusting unit that adjusts the raster image data.

  According to the present invention, a rendering performance function for calculating an evaluation value that quantitatively represents rendering performance is applied to raster image data so that the evaluation value based on the rendering performance function indicates the best rendering performance. Since the position of the recorded image on the recording medium is calculated and the raster image data is adjusted so that the recorded image is recorded at the calculated position, it is possible to perform preferable image recording with various irregularities suppressed. It is.

  As the recording head, an inkjet head having a plurality of nozzles can be applied. The “recording element” in the form including the ink jet head includes a form including a nozzle for ejecting liquid droplets, a pressure chamber communicating with the nozzle, and a pressure element for pressurizing the pressure chamber.

  The raster image data includes digital format data in which the density values of the pixels constituting the recorded image are expressed in multiple gradations. By setting the raster image data as a processing target, it is possible to consider the gradation values (density values and pixel values) included in the raster image data in the evaluation of the drawing performance.

  The drawing performance evaluation function is an evaluation function representing the degree of appearance of a factor that degrades drawing performance and the correction performance of the factor, and the degree to which the drawing performance is reduced according to the evaluation value of the drawing performance evaluation function is grasped. .

  It is preferable that the storage unit stores the acquired drawing performance evaluation function.

  (Invention 2): The image processing apparatus according to Invention 1, wherein halftone processing is performed on the adjusted raster image data.

  The halftone process in this aspect is a process for converting pixel values (density values) expressed in multiple gradations into binary or multivalued dot data.

  (Invention 3): In the image processing apparatus according to Invention 1 or 2, the drawing performance evaluation function acquisition unit acquires the drawing performance evaluation function calculated according to a gradation value of each pixel. To do.

  According to this aspect, the preferable drawing performance is evaluated in consideration of the gradation value of each pixel.

  The “gradation value” here includes values called pixel values and density values.

  (Invention 4): In the image processing apparatus according to any one of Inventions 1 to 3, the drawing performance evaluation function acquisition unit acquires the drawing performance evaluation function using a position on a recording medium as a parameter. Features.

  According to this aspect, it is possible to calculate the evaluation value of the drawing performance evaluation function while changing the position on the recording medium and compare the evaluation value to obtain the position on the recording medium that provides the best drawing performance.

  (Invention 5): In the image processing device according to any one of Inventions 1 to 4, the drawing position calculation means has an evaluation value obtained by a combined drawing performance evaluation function obtained by combining a plurality of the drawing performance evaluation functions. The position of the recorded image on the recording medium is calculated so as to show the best drawing performance.

  According to this aspect, even when there are a plurality of factors that lower the drawing performance, the preferable drawing performance is evaluated in consideration of the correlation between the plurality of factors.

  (Invention 6): In the image processing apparatus according to any one of Inventions 1 to 5, the drawing performance evaluation function acquisition unit is a first unit that is calculated from density unevenness information in a recorded image and the density unevenness correction performance. A drawing performance evaluation function is obtained.

  According to this aspect, it is possible to obtain a preferable recorded image in which a decrease in drawing performance due to density unevenness occurring in the recorded image is suppressed.

  “Density unevenness in a recorded image” includes density unevenness caused by a solid difference of a recording head.

  As a cause of the individual difference of the recording head, there are causes caused by a variation in recording characteristics of the recording element, a variation in assembly of the recording head, and the like.

  (Invention 7): In the image processing apparatus according to any one of Inventions 1 to 6, the drawing performance evaluation function acquisition means is calculated from information on an abnormal recording element in the recording head and correction performance of the abnormal recording element. The second drawing performance evaluation function is obtained.

  According to this aspect, it is possible to obtain a preferable recorded image in which a reduction in drawing performance due to the abnormal recording element is suppressed.

  The “abnormal recording element” includes a recording element that cannot perform recording and a recording element that can perform recording but cannot operate normally.

  (Invention 8): In the image processing apparatus according to any one of Inventions 1 to 7, the drawing performance evaluation function acquisition means is a third value calculated from information on density unevenness in a recorded image generated by vibration during image recording. A drawing performance evaluation function is obtained.

  According to this aspect, it is possible to obtain a preferable recorded image in which a decrease in drawing performance due to vibration during image recording is suppressed.

  (Invention 9): In the image processing apparatus according to Invention 8, the drawing position calculation means includes the first drawing performance evaluation function, the second drawing performance evaluation function, and the third drawing performance evaluation function. The position of the recorded image on the recording medium is calculated so that the evaluation value obtained by the synthesized fourth drawing performance evaluation function shows the best drawing performance.

  According to such an aspect, a decrease in drawing performance due to density unevenness in a recorded image, a decrease in drawing performance due to an abnormal recording element, and a decrease in drawing performance due to vibration during image recording are considered, and the respective correlations are considered. It is possible to evaluate the drawing performance considering the above.

  (Invention 10): In the image processing device according to any one of Inventions 1 to 9, the drawing position calculation means calculates a position for each recording image when recording a plurality of recording images on one recording medium. It is characterized by doing.

  According to this aspect, when a factor that lowers drawing performance is avoided, adjustments can be made for individual recorded images, and it is possible to cope with a variety of complicated factors that reduce drawing performance.

  (Invention 11): In the image processing device according to any one of Inventions 1 to 9, the drawing position calculation unit is configured to record all of the plurality of recorded images when recording the plurality of recorded images on one recording medium. The position is calculated.

  According to this aspect, it is possible to adjust the necessary minimum image when avoiding a factor that deteriorates the drawing performance, which contributes to a reduction in calculation load.

  (Invention 12): The image processing apparatus according to any one of Inventions 1 to 11, further comprising density unevenness correction processing means for performing correction processing for density unevenness on the adjusted raster image data. .

  According to this aspect, preferable image recording in which density unevenness is corrected is realized.

  (Invention 13): The image processing apparatus according to any one of Inventions 1 to 12, further comprising an abnormal recording element correction processing unit that performs correction processing on the abnormal recording element with respect to the adjusted raster image data. Features.

  According to this aspect, preferable image recording in which a decrease in drawing performance due to the abnormal recording element is corrected is realized.

  (Invention 14): Drawing performance evaluation for obtaining at least one drawing performance evaluation function for calculating an evaluation value quantitatively representing the drawing performance of an image recorded by operating a recording element provided in the recording head A function acquisition unit, a raster image data acquisition unit that acquires raster image data representing a multi-gradation image composed of a plurality of pixels, and the acquired drawing performance evaluation for the acquired raster image data Drawing position calculation means for calculating the position of the recorded image on the recording medium so that the evaluation value obtained by the function shows the best drawing performance, and the image is recorded at the calculated position on the recording medium. A drawing position adjusting means for adjusting the raster image data; and the recording head so as to record a recorded image on a recording medium based on the adjusted raster image. The image recording apparatus characterized by comprising a recording control means for operating the printing elements provided in the.

  As one aspect of the image recording according to the present invention, there is an ink jet recording apparatus that records a color image on a recording medium by ejecting ink droplets from an ink jet head.

  (Invention 15): Drawing performance evaluation for obtaining at least one drawing performance evaluation function for calculating an evaluation value that quantitatively represents the drawing performance of an image recorded by operating a recording element provided in the recording head A function acquisition step, a raster image data acquisition step of acquiring raster image data representing a multi-tone image composed of a plurality of pixels, and the acquired drawing performance evaluation for the acquired raster image data A drawing position calculating step for calculating the position of the recorded image on the recording medium so that the evaluation value obtained by the function shows the best drawing performance, and the image is recorded at the calculated position on the recording medium. And a drawing position adjusting step for adjusting the raster image data.

  In the present invention, an aspect including a halftone process for performing halftone processing on the adjusted raster image data is preferable.

  The drawing position calculating step preferably calculates the position of the recorded image on the recording medium so that the evaluation value obtained by the stored drawing performance evaluation function shows a minimum value.

  Further, it is preferable that the drawing performance evaluation function acquisition step acquires at least one drawing performance evaluation function calculated according to the gradation value of each pixel.

  Further, the drawing position calculation step calculates the position of the recorded image on the recording medium so that the evaluation value obtained by the combined drawing performance evaluation function obtained by combining the plurality of drawing performance evaluation functions shows the best drawing performance. Embodiments are preferred.

  Further, the drawing performance evaluation function acquisition unit acquires a first drawing performance evaluation function calculated from density unevenness information in the recorded image and the density unevenness correction performance, or an abnormal recording element in the recording head. And a second drawing performance evaluation function calculated from the correction performance of the abnormal recording element, a third drawing calculated from density unevenness information in a recorded image generated by vibration during image recording The evaluation value obtained by the aspect of acquiring the performance evaluation function, the first drawing performance evaluation function, the second drawing performance evaluation function, and the fourth drawing performance evaluation function obtained by synthesizing the third drawing performance evaluation function is the best. It is preferable to calculate the position of the recorded image on the recording medium so as to show the drawing performance.

  Further, it is preferable that the drawing position calculating unit calculates the position for each recording image when recording a plurality of recording images on one recording medium.

  On the other hand, it is also preferable that the drawing position calculation means calculates the positions of the plurality of recorded images when recording the plurality of recorded images on one recording medium.

  A mode including a density unevenness correction process for performing correction processing for density unevenness on the adjusted raster image data, or an abnormal recording element correction process for performing correction processing for the abnormal recording element on the adjusted raster image data The aspect containing is preferable.

  DESCRIPTION OF SYMBOLS 10 ... Image processing apparatus, 12 ... Raster image data input part, 14 ... Drawing position adjustment process part, 16 ... Density unevenness correction process part, 18 ... Discharge abnormal nozzle correction process part, 20 ... Halftone process part, 22 ... Halftone Image data output unit, 30 ... unevenness evaluation function acquisition unit, 32 ... drawing position adjustment amount calculation unit, 60 ... recording head, 62, 150 ... nozzle, 66, 102 ... recording medium, 68 ... recorded image, 100 ... inkjet recording apparatus , 106 ... printing unit, 106K, 106C, 106M, 106Y, 140 ... inkjet head, 170 ... communication interface, 172 ... system control unit, 176 ... image processing unit, 190 ... parameter storage unit

Claims (15)

A drawing performance evaluation function acquisition means for acquiring at least one drawing performance evaluation function for obtaining an evaluation value that quantitatively represents the drawing performance of an image recorded by operating a recording element provided in the recording head;
A raster image data acquisition unit for acquiring raster image data representing a multi-tone image composed of a plurality of pixels;
A drawing position calculating means for calculating the position of the recorded image on the recording medium so that the evaluation value obtained by the acquired drawing performance evaluation function shows the best drawing performance for the acquired raster image data. When,
A drawing position adjusting means for adjusting the raster image data so that an image is recorded at the calculated position on the recording medium;
An image processing apparatus comprising:   The image processing apparatus according to claim 1, further comprising a halftone processing unit that performs a halftone process on the adjusted raster image data.   The image processing apparatus according to claim 1, wherein the drawing performance evaluation function acquisition unit acquires the drawing performance evaluation function calculated according to a gradation value of each pixel.   The image processing apparatus according to claim 1, wherein the drawing performance evaluation function acquisition unit acquires the drawing performance evaluation function using a position on a recording medium as a parameter.   The drawing position calculation means calculates a position on the recording medium of a recorded image so that an evaluation value obtained by a combined drawing performance evaluation function obtained by combining a plurality of the drawing performance evaluation functions shows the best drawing performance. The image processing apparatus according to claim 1, wherein:   6. The drawing performance evaluation function acquisition unit acquires a first drawing performance evaluation function calculated from density unevenness information in a recorded image and the density unevenness correction performance. The image processing apparatus according to claim 1.   2. The drawing performance evaluation function acquisition unit acquires a second drawing performance evaluation function calculated from information on an abnormal recording element in the recording head and a correction performance of the abnormal recording element. 7. The image processing apparatus according to any one of items 1 to 6.   8. The drawing performance evaluation function acquisition unit acquires a third drawing performance evaluation function calculated from density unevenness information in a recorded image generated by vibration during image recording. The image processing apparatus according to claim 1.   The drawing position calculation means is an evaluation value obtained by a fourth drawing performance evaluation function obtained by synthesizing the first drawing performance evaluation function, the second drawing performance evaluation function, and the third drawing performance evaluation function. The image processing apparatus according to claim 8, wherein the position of the recorded image on the recording medium is calculated so that indicates the best drawing performance.   The image according to any one of claims 1 to 9, wherein the drawing position calculating unit calculates a position for each recording image when recording a plurality of recording images on one recording medium. Processing equipment.   10. The drawing position calculating unit according to claim 1, wherein when the plurality of recorded images are recorded on a single recording medium, the drawing position calculating unit calculates positions of the plurality of recorded images as a whole. The image processing apparatus described.   The image processing apparatus according to claim 1, further comprising a density unevenness correction processing unit configured to perform correction processing for density unevenness on the adjusted raster image data.   The image processing apparatus according to claim 1, further comprising: an abnormal recording element correction processing unit that performs correction processing on the abnormal recording element with respect to the adjusted raster image data. A drawing performance evaluation function acquisition means for acquiring at least one drawing performance evaluation function for obtaining an evaluation value that quantitatively represents the drawing performance of an image recorded by operating a recording element provided in the recording head;
A raster image data acquisition unit for acquiring raster image data representing a multi-tone image composed of a plurality of pixels;
A drawing position calculating means for calculating a position of the recorded image on the recording medium so that the evaluation value obtained by the acquired drawing performance evaluation function indicates the best drawing performance with respect to the acquired raster image data; ,
Drawing position adjusting means for adjusting the raster image data so that an image is recorded at the calculated position on the recording medium;
Recording control means for operating the recording element provided in the recording head to record a recording image on a recording medium based on the adjusted raster image;
An image recording apparatus comprising: A drawing performance evaluation function acquisition step for acquiring at least one drawing performance evaluation function for obtaining an evaluation value that quantitatively represents the drawing performance of an image recorded by operating a recording element provided in the recording head;
A raster image data acquisition step of acquiring raster image data representing a multi-tone image composed of a plurality of pixels;
A drawing position calculating step for calculating a position of the recorded image on the recording medium such that an evaluation value obtained by the acquired drawing performance evaluation function indicates the best drawing performance for the acquired raster image data; ,
A drawing position adjusting step of adjusting the raster image data so that an image is recorded at the calculated position on the recording medium;
An image processing method comprising:

Images