JP2013173324A - Printing apparatus, pattern forming method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a pattern for density correction by which a measurement result of a sensor is stably obtained.SOLUTION: A printing apparatus includes: a head to discharge ink; a sensor; and a controller. In the printing apparatus, the controller makes the head form a plurality of patterns for tolerable quantities different in the ink amounts in a region of a prescribed area, and makes the sensor measure the density of the plurality of patterns for determination of tolerable quantities, and specifies tolerable quantities of the ink to be used for density correction pattern, based on the measurement result of the density.

Description

  The present invention relates to a printing apparatus, a pattern forming method, and a program.

  Conventionally, in a printing apparatus that prints an image on a medium (paper, cloth, etc.), a test pattern is printed on the medium, and density correction processing (so-called color calibration) is performed according to the result of reading the test pattern.

  For example, Patent Document 1 discloses that the density of a calibration patch is reversed in consideration of the influence of cockling. Japanese Patent Application Laid-Open No. H10-228707 describes shifting the density of a so-called bidirectional printing adjustment patch in consideration of the influence of cockling.

JP 2008-302521 A JP 2006-69099 A

  When performing the density correction process, a large number of patches having different gradation values are printed. However, in a patch having a high density, the amount of ink per unit area is large, so the medium that has absorbed the ink may be deformed. When the medium is deformed, the measurement result of the sensor for measuring the density tends to become unstable, and there is a possibility that appropriate density correction processing cannot be performed if such a measurement result is used.

  The present invention has been made in view of such circumstances, and an object of the present invention is to form a density correction pattern capable of stably obtaining a sensor measurement result.

The main invention for achieving the above object is:
A head for ejecting ink;
A sensor,
A controller,
A printing apparatus comprising:
The controller is
The head is formed with a plurality of allowable amount determining patterns having different ink amounts within a predetermined area.
Let the sensor measure the density of the plurality of tolerance determination patterns;
Based on the measurement result of the density, an allowable amount of ink used for forming the density correction pattern is specified.
It is a printing device.

  Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

1 is a block diagram of the overall configuration of a printer. FIG. 2A is a schematic diagram of the overall configuration of the printer 1, and FIG. 2B is a cross-sectional view of the overall configuration of the printer 1. FIG. 4 is an explanatory diagram showing the arrangement of nozzles on the lower surface of a head 41. 4A and 4B are explanatory diagrams of operations during printing and measurement of density correction processing. FIG. 5A is an external view of a strip-shaped gradation pattern for specifying the amount of unstable ink, FIG. 5B is an explanatory diagram of the configuration of the strip-shaped gradation pattern, and FIG. FIG. 5D is an explanatory diagram for measuring an intermediate gradation value pattern, and FIG. 5E is another explanatory diagram for measuring an intermediate gradation value pattern. It is explanatory drawing of correction | amendment of a certain gradation value X. FIG. 7A and 7B are explanatory diagrams showing a state in which the medium is deformed so as to wave, and FIGS. 7C and 7D are explanatory diagrams of light reception by the optical sensor 54. It is a flowchart in this embodiment. FIG. 9A is an explanatory diagram of a determination pattern for specifying the ink amount at which the sensor measurement value becomes unstable, and FIG. 9B is an explanatory diagram of the determination pattern with different chart areas. It is explanatory drawing of the 1st method of reconstructing the density correction pattern. It is explanatory drawing of the 2nd method of reconstructing the density correction pattern. It is explanatory drawing of the 3rd method which reconstructs the pattern for density correction. It is explanatory drawing of the 4th method which reconstructs the pattern for density correction.

At least the following matters will become clear from the description of the present specification and the accompanying drawings. That is,
A head for ejecting ink;
A sensor,
A controller,
A printing apparatus comprising:
The controller is
The head is formed with a plurality of allowable amount determining patterns having different ink amounts within a predetermined area.
Let the sensor measure the density of the plurality of tolerance determination patterns;
Based on the measurement result of the density, an allowable amount of ink used for forming the density correction pattern is specified.
It is a printing device.
By doing so, it is possible to form a density correction pattern with an allowable amount of ink that can stably obtain the measurement result of the sensor. Then, density correction can be appropriately performed using the density correction pattern.

In this printing apparatus, it is preferable that the density correction pattern formed based on the allowable amount is switched in the density change direction of the density correction pattern for each color of the ink.
In this way, in the case of forming a density correction pattern in which the density increases stepwise or the density decreases stepwise, there is a density correction pattern of an adjacent different ink color. A patch having a low ink color density can be formed next to a patch having a high ink color density. Then, it is possible to form a density correction pattern so that the sensor measurement result is an ink amount that can be stably obtained.

Further, it is preferable that the density correction pattern formed based on the allowable amount can be separated from the density correction pattern for each color of the ink.
By doing in this way, the area | region where an ink does not land can be formed between different ink colors. Then, a density correction pattern having patches smaller than a predetermined area can be formed.

The density correction pattern formed based on the allowable amount may be provided with a slit in the density correction pattern.
By doing so, for example, since the slit can be formed in the pattern having the highest density, the area where the ink lands can be divided into substantially smaller areas. Then, a density correction pattern having patches smaller than a predetermined area can be formed.

Further, in the density correction pattern formed based on the allowable amount, the angle at which the density correction patterns for some ink colors are arranged may be different from the angle at which the density correction patterns for other ink colors are arranged. .
By doing so, it is possible to arrange patches having different densities without adjoining each other in different ink colors.

Furthermore, when the allowable amount determining pattern is formed, an allowable amount determining pattern having a different predetermined area may be formed.
By doing in this way, the area which can obtain the measurement result of a sensor stably can be specified further.

In addition, at least the following matters will become clear from the description of the present specification and the accompanying drawings. That is,
Forming a plurality of allowable amount determining patterns with different amounts of ink in a predetermined area in the head; and
Causing the sensor to measure the density of the plurality of tolerance determination patterns;
Identifying an allowable amount of ink used for forming a density correction pattern based on the density measurement result;
Is a pattern forming method.
By doing so, it is possible to form a density correction pattern with an allowable amount of ink that can stably obtain the measurement result of the sensor. The density correction can be appropriately performed using the density correction pattern.

In addition, at least the following matters will become clear from the description of the present specification and the accompanying drawings. That is,
In a printing control device that controls a printing device that includes a head that ejects ink and a sensor that measures density,
A function of causing the head to form a plurality of allowable amount determining patterns with different ink amounts within a predetermined area;
A function of causing the sensor to measure the density of the plurality of tolerance determination patterns;
A function of specifying an allowable amount of ink used for forming a density correction pattern based on the density measurement result;
It is a program characterized by realizing.
By doing so, it is possible to form a density correction pattern with an allowable amount of ink that can stably obtain the measurement result of the sensor. The density correction can be appropriately performed using the density correction pattern.

=== Explanation of basic contents ===
<Overall configuration>
FIG. 1 is a block diagram of the overall configuration of the printer 1. FIG. 2A is a schematic diagram of the overall configuration of the printer 1. FIG. 2B is a cross-sectional view of the overall configuration of the printer 1. Hereinafter, a basic configuration of the printer will be described.

  The printer 1 includes a transport unit 20, a carriage unit 30, a head unit 40, a detector group 50, and a controller 60. The printer 1 that has received print data from the computer 110 (printing control device), which is an external device, controls each unit (conveyance unit 20, carriage unit 30, and head unit 40) by the controller 60. The situation in the printer 1 is monitored by the detector group 50, and the detector group 50 sends the detection result to the controller 60.

  The transport unit 20 is for transporting a medium (for example, paper S) in a first direction (hereinafter referred to as a transport direction). The transport unit 20 includes a paper feed roller 21, a transport motor 22 (also referred to as a PF motor), a transport roller 23, a platen 24, and a paper discharge roller 25. The paper feed roller 21 is a roller for feeding the paper S inserted into the paper insertion slot into the printer. The transport roller 23 is a roller that transports the paper S fed by the paper feed roller 21 to a printable area, and is driven by the transport motor 22. The platen 24 supports the paper S being printed. The paper discharge roller 25 is a roller for discharging the paper S to the outside of the printer, and is provided on the downstream side in the transport direction with respect to the printable area.

  The carriage unit 30 is for moving (also referred to as “scanning”) the head in a second direction (hereinafter referred to as a moving direction). The carriage unit 30 includes a carriage 31 and a carriage motor 32 (also referred to as a CR motor). The carriage 31 can reciprocate in the moving direction and is driven by a carriage motor 32. Further, the carriage 31 detachably holds an ink cartridge that stores ink.

  The head unit 40 is for ejecting ink onto the paper S. The head unit 40 includes a head 41 having a plurality of nozzles. Since the head 41 is provided on the carriage 31, when the carriage 31 moves in the movement direction, the head 41 also moves in the movement direction. Then, a dot line (raster line) along the moving direction is formed on the paper S by intermittently ejecting ink while the head 41 is moving in the moving direction.

  The detector group 50 includes a linear encoder 51, a rotary encoder 52, a paper detection sensor 53, an optical sensor 54, and the like. The linear encoder 51 detects the position of the carriage 31 in the moving direction. The rotary encoder 52 detects the rotation amount of the transport roller 23. The paper detection sensor 53 detects the position of the leading edge of the paper S being fed. The optical sensor 54 detects a pattern printed on the paper S by a light source and a light receiving sensor attached to the carriage 31.

  The controller 60 is a control unit for controlling the printer. The controller 60 includes an interface unit 61, a CPU 62, a memory 63, and a unit control circuit 64. The interface unit 61 transmits and receives data between the computer 110 that is an external device and the printer 1. The CPU 62 is an arithmetic processing unit for controlling the entire printer. The memory 63 is for securing an area for storing a program of the CPU 62, a work area, and the like, and includes storage elements such as a RAM and an EEPROM. The CPU 62 controls each unit via the unit control circuit 64 in accordance with a program stored in the memory 63.

  FIG. 3 is an explanatory diagram showing the arrangement of nozzles on the lower surface of the head 41. On the lower surface of the head 41, a black ink nozzle group K, a cyan ink nozzle group C, a magenta ink nozzle group M, and a yellow ink nozzle group Y are formed. Each nozzle group includes a plurality (180 in this case) of nozzles that are ejection openings for ejecting ink of each color.

  The plurality of nozzles of each nozzle group are aligned at a constant interval (nozzle pitch: k · D) along the transport direction. Here, D is the minimum dot pitch in the carrying direction (that is, the interval at the highest resolution of dots formed on the paper S). K is an integer of 1 or more. For example, when the nozzle pitch is 180 dpi (1/180 inch) and the dot pitch in the transport direction is 720 dpi (1/720 inch), k = 4.

  The nozzles of each nozzle group are assigned a smaller number as the nozzles on the downstream side (# 1 to # 180). That is, the nozzle # 1 is located downstream of the nozzle # 180 in the transport direction.

  The position of the optical sensor 54 in the transport direction is downstream in the transport direction with respect to the nozzle # 1 located on the most downstream side.

<Density correction processing (color calibration)>
A printer driver (program) for controlling the printer 1 is installed in the computer 110 (see FIG. 1). Then, the computer 110 causes the printer 1 to execute a density correction process described below according to a density correction program incorporated in the printer driver.

  4A and 4B are explanatory diagrams of operations at the time of printing and measurement of the density correction processing of the reference example. Here, the black density correction process will be described.

  As shown in FIG. 4A, the printer 1 that has received an instruction from the computer 110 ejects black ink from the black ink nozzle group K of the head 41 to form a density correction pattern of a belt-like gradation pattern on the medium. The density correction pattern is formed for each ink color. The density correction pattern is formed by ejecting ink according to a specific gradation value. However, the ideal ink amount is not applied to each density correction pattern due to the influence of a manufacturing error or the like. For example, when the ink droplets ejected from the head 41 are small, the amount of ink per unit area is reduced, so that a light correction pattern is formed. That is, at this stage, the ideal density (the target density of the specific gradation value) and the actual density are different.

  Next, as illustrated in FIG. 4B, the printer 1 measures the density of each correction pattern using the optical sensor 54, and transmits the measured value of the optical sensor 54 to the computer 110. The computer 110 normalizes the measurement value of the optical sensor 54 received from the printer 1 as follows.

P (X1) = {Praw (X1) − Praw (255)} / {Praw (0) − Praw (255)}

Praw (X1) in the equation is a measured value (raw data) of the optical sensor 54 when the correction pattern having the specific gradation value X1 is measured.
Praw (255) is a measured value of the optical sensor when a correction pattern (so-called solid pattern) having a specific gradation value of 255 is measured.
Praw (0) is a measurement value of the optical sensor having a correction pattern with a specific gradation value of 0.
P (X1) is a normalized measurement value.

  The optical sensor measures a low value when the density is high (dark). Also, a high value is measured when the density is low (bright).

  Here, normalization is performed so that the measured value of the pattern with the lightest gradation value 0 is “1” and the measured value of the pattern with the darkest gradation value 255 is “0”. For this reason, P (X1) is a value between 0 and 1. However, normalization may be performed based on another expression (for example, P (X1) = Praw (X1) / Praw (255)). Further, normalization may be performed with reference to other gradation values instead of using gradation value 0 or gradation value 255 as a reference.

  FIG. 5A is an explanatory diagram of a configuration of a belt-like gradation pattern. The numbers in parentheses in the figure indicate the black tone values.

  The belt-like gradation pattern is formed by arranging 256 rectangular patterns with gradation values 0 to 255 in the moving direction so that the gradation values continuously change. Thereby, a band-like gradation pattern is formed in which the ink amount per unit area gradually changes from the minimum amount to the maximum amount.

  Two rectangular patterns (patterns with gradation values 0 and 255) located at both ends are square. These two square patterns are larger in both the width in the moving direction and the width in the transport direction than the diameter (spot diameter) of the detection region of the optical sensor 54.

  A large number of rectangular patterns (patterns having gradation values of 1 to 254, which are intermediate gradation values) at the center have a width in the transport direction larger than the spot diameter of the optical sensor 54, but the width in the movement direction is that of the optical sensor 54. Smaller than the spot diameter. For this reason, a rectangular pattern corresponding to many gradation values can be formed in a narrow print region.

Next, the density of the belt-like gradation pattern is measured.
FIG. 5B is an explanatory diagram of the operation when measuring the density of the gradation pattern. FIG. 5C is an explanatory diagram when measuring a pattern of intermediate gradation values.

  In the present embodiment, when the optical sensor 54 measures the pattern of the intermediate gradation value t, the detection area of the optical sensor (illustrated by a broken line in FIG. 5D) protrudes from the pattern. However, as shown in FIG. 5D, the pattern of gradation value t-1 is formed adjacent to the left side of the pattern of intermediate gradation value t, and the pattern of gradation value t + 1 is adjacent to the right side. Is formed. That is, a light pattern is formed adjacent to the left side, and a dark pattern is formed adjacent to the right side. For this reason, even if the detection region of the optical sensor protrudes from the pattern of the intermediate gradation value t, the optical sensor 54 can measure a value substantially corresponding to the density of the pattern of the intermediate gradation value t.

  FIG. 5E is another explanatory diagram when measuring a pattern of intermediate gradation values. Here, the center position of the detection region of the optical sensor 54 is located at the boundary between the pattern of the intermediate gradation value t and the pattern of the intermediate gradation value t + 1. At this position, the amount of ink per unit area in the detection area of the optical sensor 54 is larger than the amount of ink per unit area of the pattern of the intermediate gradation value t, and the amount of ink per unit area of the pattern of the intermediate gradation value t + 1. Less than the amount of ink. That is, the ink amount per unit area in the detection region of the optical sensor 54 at this position is an ink amount corresponding to the intermediate gradation value t + 0.5.

  Thus, in the present embodiment, the density with respect to the gradation value is measured more finely than in 256 steps. In other words, in this embodiment, the optical sensor 54 measures the density of the gradation pattern at intervals shorter than the width of the rectangular pattern in the moving direction.

  FIG. 6 is an explanatory diagram of correction of a certain gradation value X. The horizontal axis of the graph indicates the gradation value on the image data. The vertical axis of the graph indicates the density of the image printed on the medium. T (X) in the figure indicates a graph of the target density with respect to the gradation value X. Black circles in the figure indicate measured values (normalized measured values) at respective positions of the gradation density correction pattern. Here, a plurality of black circles are shown, but more measured values are actually measured. P (X) in the figure shows a graph of the actual density obtained from the measured value of the correction pattern. Since the measured value is a discrete value, P (X) is obtained, for example, by interpolating between two black circles.

  In the case as shown in the figure, if an image is printed as it is according to the gradation value without correcting the gradation value, it is printed relatively lightly. For example, when an image is printed according to the gradation value t, it is printed with a density P (t) that is lighter than the target density T (t). Therefore, for example, when printing an image having a gradation value t, the gradation value t is corrected to the gradation value t ′ (= t + α) by the correction value α, and the image is then displayed according to the corrected gradation value t ′. If printing is performed, an image having an initial target density T (t) can be obtained. As described above, the computer 110 calculates a correction value for each gradation value based on the measurement value of the correction pattern. The calculated correction value is stored in the storage device of the computer 110.

  When printing an image after obtaining the correction value, the computer 110 corrects the gradation value (for example, gradation value t) of each pixel constituting the image with the correction value (for example, the correction value α), and after the correction. The image is printed based on the tone value (for example, tone value t ′). Thereby, the density of the image can be corrected.

  In the above description, the computer 110 performs a process for calculating the correction value and a process for correcting the gradation value of the image based on the correction value. However, the printer may perform a process of calculating a correction value and a process of correcting the gradation value of the image based on the correction value.

<Causes of unstable optical sensor measurement results>
In a region where the amount of ink per unit area is large, the measurement value (measurement result) of the optical sensor 54 may become unstable. One of the causes is a phenomenon (cockling) in which the medium is deformed so as to wave.

FIG. 7A and FIG. 7B are explanatory diagrams showing a state in which the medium is deformed so as to wave. FIG. 7A is a top view of the medium. 7B is a cross-sectional view taken along line BB in FIG. 7A.
As shown in FIG. 7A, a belt-like filling pattern is printed on the medium. The filled pattern is formed by applying ink so that the amount of ink per unit area increases. When the medium absorbs ink and expands and contracts, the medium is deformed so as to wave as shown in FIG. 7B.

  7C and 7D are explanatory diagrams of light reception by the optical sensor 54. FIG. The optical sensor 54 irradiates the medium with light from a light source, receives light reflected by the medium with a light receiving sensor, and measures a signal corresponding to the amount of received light. As shown in FIG. 7C, when the distance between the optical sensor 54 and the medium is close, the optical path is shortened and the intensity of the reflected light increases. Conversely, when the distance between the optical sensor 54 and the medium is increased, the optical path is It becomes longer and the intensity of reflected light decreases. As a result, when the medium is deformed so as to wave as shown in FIGS. 7B and 7C, the distance between the optical sensor 54 and the medium fluctuates, so that the measurement value of the optical sensor 54 is considered to be unstable.

  Further, the measurement value of the optical sensor 54 becomes unstable not only because the distance between the optical sensor 54 and the medium fluctuates, but also due to local inclination of the medium as described below. Conceivable.

  Since the optical sensor 54 is intended to measure the density of the pattern, a light source and a light receiving sensor are arranged so as to detect diffuse reflected light instead of regular reflected light from the medium (left side of FIG. 7D). reference). For example, the light source is disposed so as to irradiate light from an angle of 45 degrees with respect to the surface of the medium, and the light receiving sensor is disposed above the light irradiation spot. However, when the medium is locally tilted, for example, when the medium is deformed so as to wave, the light receiving sensor may receive specularly reflected light (see the right side of FIG. 7D). In such a case, since the amount of light received by the light receiving sensor becomes high, the measurement value of the optical sensor 54 becomes unstable. In particular, when the optical sensor 54 measures a pattern with a high density (a pattern with a large amount of ink per unit area), the amount of diffused light is small, so the change in the amount of light received when regular reflected light is received. Becomes abrupt and the measured value of the optical sensor 54 tends to become unstable.

  As described above, in a region where the amount of ink per unit area is large, the measurement value of the optical sensor 54 becomes unstable due to a synergistic effect.

  When a predetermined amount of ink is ejected over a certain area or when the amount of ink exceeds a certain amount per unit area, it is considered that the measured value of the optical sensor 54 becomes unstable as described above. Further, such an unstable area and ink amount vary depending on the type of medium. Therefore, as described below, when the medium has a possibility that the measurement value of the optical sensor 54 may become unstable, the density correction pattern is reconfigured to make the measurement value of the optical sensor 54 unstable. I try not to be.

  FIG. 8 is a flowchart in the present embodiment. Hereinafter, the present embodiment for reconstructing the density correction pattern will be described with reference to this flowchart. In this embodiment, first, a determination pattern is printed (S102).

  FIG. 9A is an explanatory diagram of a determination pattern. In FIG. 9A, ink is applied in different amounts for each patch of a predetermined area A. The area of each patch is unified to A, but the ink discharge amount of the patch is different. Here, the ink amount at which the measured value of the optical sensor 54 becomes unstable is specified using this determination pattern. In FIG. 9A, the measured value by the optical sensor 54 is also shown. The size of each patch is sufficiently larger than the spot diameter of the optical sensor 54. Since the size of each patch is sufficiently larger than the spot diameter of the optical sensor 54, in FIG. 9A, the measured value at the position including the patch boundary is assumed to change sharply.

  Next, density measurement processing is performed (S104). In the density measurement process, the density of each patch of the aforementioned determination pattern is measured. Then, based on the measured density, an ink amount that becomes an unstable measurement value is specified (S106). In the measured value graph of FIG. 9A, the measured value is almost constant in the same patch for those having a high measured value (that is, having a low concentration). On the other hand, in two patches having low measurement values (high density), the measurement values fluctuate within the same patch. This indicates that the measured value is unstable due to the deformation of the medium.

  Therefore, it is determined here whether or not the measurement value of the optical sensor 54 is unstable based on whether or not the amplitude of the measurement value is within a predetermined range. That is, when the amplitude is larger than the predetermined range, it is determined that the measured value of the optical sensor 54 is unstable. On the other hand, when the amplitude is within a predetermined range, it is determined that the measured value of the optical sensor is stable. Here, for example, it is assumed that the amplitude of the measurement value for two patches having a high density exceeds a predetermined range and it is determined that the measurement value is unstable.

  Next, a density correction pattern is reconstructed based on the ink amount at which the measured value becomes unstable (S108). A method for reconfiguration will be described later.

  Next, the reconstructed density correction pattern is printed on the medium (S110). Then, the density of the printed density correction pattern is measured by the optical sensor 54, and density correction processing is performed based on the obtained measurement value (S112). The density correction process is the same as the density correction process described with reference to FIGS.

  In this way, the density correction pattern is reconstructed so that the measurement value does not become unstable, and the density correction is performed based on the reconstructed pattern. Therefore, it is possible to perform density correction with higher accuracy.

  FIG. 9B is an explanatory diagram of determination patterns with different chart areas. In FIG. 9A described above, the size of one patch is constant and only the amount of ink to be applied is varied. However, as shown in FIG. 9B, the size of one patch is varied. Also good. By doing so, it becomes possible to determine in which patch size the measurement value of the optical sensor 54 becomes unstable. In FIG. 9B, although the patches PA11, PA21, and PA31 have different sizes, the amount of ink applied per unit area is the same. In FIG. 9B, the patches such as PA11, PA12, and PA13 have the same size although the amount of ink applied per unit area is different.

<First Method of Pattern Reconstruction>
FIG. 10 is an explanatory diagram of a first method for reconstructing the density correction pattern. Originally, the density correction pattern is formed so that the density on the right side of the figure is uniformly high and the density on the left side is uniformly low. However, with this configuration, a high density area (that is, an area with a large ink discharge amount) is concentrated on the right side of the drawing. Then, on the right side of the figure, there is a case where the measurement result of the sensor becomes unstable in the above-described region of the predetermined area.

  Therefore, in the first method for reconstructing the density correction pattern, for example, the density correction pattern is reconstructed so that the high density area and the low density area are staggered. Specifically, as shown in FIG. 10, for cyan ink and yellow ink, the right side is a gradation pattern with high density (C and Y patterns in FIG. 10), and for magenta ink and black ink, The density correction pattern is reconfigured so that the right side is a gradation pattern with low density (M and K patterns in FIG. 10).

By doing so, it is possible to flatten the amount of ink used in the density correction pattern and to prevent the occurrence of cockling.
Further, it is possible to reconstruct the density correction pattern for each medium used for the density correction processing. Specifically, when the density correction pattern is formed on a medium whose ink amount per unit area specified by the determination pattern is the first amount, the density correction pattern for each ink color is set to have a high density. The region and the low concentration region are formed so as to alternate. In addition, when the density correction pattern is formed on a medium whose ink amount per unit area specified by the determination pattern is the second amount (first amount <second amount), at least two ink colors are used. The density correction patterns are formed with the light and dark directions aligned.

  By the way, normally, it is desirable that the gradation direction of the gradation is aligned with all ink colors. This is because when the optical sensor 54 reads the gradation pattern, the optical sensor 54 moves in the direction in which the gradation changes, but a measurement value including an error that varies depending on the direction in which the optical sensor 54 moves is obtained. Specifically, the measurement value when the optical sensor 54 is moved from the left side to the right side in FIG. 10 and the measurement value when the optical sensor 54 is moved from the right side to the left side include different errors. Therefore, it is desirable to align the direction of gradation.

However, as described above, when the ink ejection amount increases, the measurement of the optical sensor 54 becomes unstable, and an error exceeding the aforementioned error is included. An error included when the measurement of the optical sensor 54 becomes unstable is larger than an error included when the moving direction of the optical sensor 54 is changed. Therefore, in the present embodiment, the direction of gradation of the gradation is changed to preferentially remove the instability of the measurement value of the optical sensor 54.
When density correction processing is performed using a medium whose measurement value becomes unstable due to deformation of the medium or the like, the medium is less likely to have unstable measurement values by changing the direction of gradation of gradation as described above. When density correction processing is performed using, the gradation direction of gradation may be aligned.

<Second Method of Pattern Reconstruction>
FIG. 11 is an explanatory diagram of a second method for reconstructing the density correction pattern. Originally, the density correction patterns of the respective ink colors are formed so as to be in contact with each other in response to a request for forming as many density correction patterns as possible on a medium as small as possible. However, with this configuration, a high density region (that is, a region with a large ink discharge amount) on the right side of the drawing is concentrated, and as a result, a high density region has a predetermined measurement in which measurement by the optical sensor 54 becomes unstable. There are cases where the area is exceeded.

  Therefore, in the second method for reconstructing the density correction pattern, the density correction pattern is formed apart from the density correction pattern for each ink color so as not to exceed a predetermined area where the measurement of the optical sensor 54 becomes unstable.

  By doing so, it is possible to flatten the amount of ink used in the density correction pattern and to prevent the occurrence of cockling. Specifically, when the measured value of the optical sensor 54 becomes unstable in a certain area A, each ink color so that the total area at a higher density than the measured value that has become unstable does not exceed the area A. The density correction patterns can be divided and separated.

<Third method of pattern reconstruction>
FIG. 12 is an explanatory diagram of a third method for reconstructing the density correction pattern. Here, in order to perform measurement with higher accuracy, one patch is formed for one density in the density correction pattern. When such a density correction pattern is formed, the third method for reconstructing the density correction pattern is, for example, slitting a patch with high density (P253, P254, and P255 in FIG. 12). Form a pattern that contains. Specifically, a slit is provided in a patch having a density corresponding to the amount of ink whose measurement value has become unstable. In FIG. 12, slits are provided for three patches from the right with high density.

  By doing so, the area of the patch having a high density can be reduced. The measurement of the optical sensor 54 becomes unstable when the high density region is larger than a predetermined area. Therefore, the area of the high-density region can be cut by inserting a slit as described above. Then, the measurement of the optical sensor 54 can be prevented from becoming unstable.

<Fourth Method of Pattern Reconstruction>
FIG. 13 is an explanatory diagram of a fourth method for reconstructing the density correction pattern. As shown in FIG. 13, in the fourth method, it is possible to reconfigure a certain ink color so that the density correction pattern is arranged at an angle different from that of the other ink color. By doing so, it is possible to separate a part of the patch having a high density and to form a part of the density correction pattern in a space having a margin in the medium.

  By doing so, since the portion where the ink is applied is dispersed without being concentrated in a certain region, the possibility of cockling can be reduced. A stable measurement value can be obtained.

  The density correction pattern may be reconstructed by combining the first to fourth methods of pattern reconstruction described above.

=== Other Embodiments ===
About said embodiment, it can also carry out for every dot size. For example, it is assumed that the printer 1 can form small dots, medium dots, and large dots. The ink ejection duty (for example, the ratio of the number of dots to the total number of dots per unit area) for each dot can be changed from 0% to 100%. At this time, a determination pattern using only small dots, a determination pattern using only medium dots, and a determination pattern using only large dots are formed.

  The density is measured for each of the determination patterns formed in this way, and the patch whose measurement value becomes unstable is specified as described above. Further, as described above, a slit can be formed for a patch having a density higher than that of the unstable patch.

  Also, if the measurement value of only the large dot determination pattern becomes unstable, only the large dot determination pattern can be switched for each ink color as described above, or the density correction pattern for each ink color. Can be separated.

  By doing so, in the printer 1 that performs gradation expression using a plurality of dot sizes, it is possible to eliminate the instability of the measurement value of the optical sensor 54 and perform highly accurate density correction.

  In the above-described embodiment, when the density correction pattern is measured without contacting the medium as in the optical sensor 54, the density correction pattern is reconstructed because cockling occurs and the measurement value becomes unstable. May be. Cockling is unlikely to occur when using a sensor that measures in contact.

  In the above-described embodiment, the printer 1 has been described as the liquid ejecting apparatus. However, the present invention is not limited to this, and other fluids other than ink (liquids, liquids in which particles of functional materials are dispersed, gels) Such a fluid can also be embodied in a liquid ejection device that ejects or ejects the fluid. For example, color filter manufacturing apparatus, dyeing apparatus, fine processing apparatus, semiconductor manufacturing apparatus, surface processing apparatus, three-dimensional modeling machine, gas vaporizer, organic EL manufacturing apparatus (especially polymer EL manufacturing apparatus), display manufacturing apparatus, film formation You may apply the technique similar to the above-mentioned embodiment to the various apparatuses which applied inkjet technology, such as an apparatus and a DNA chip manufacturing apparatus. These methods and manufacturing methods are also within the scope of application.

  The above-described embodiments are for facilitating the understanding of the present invention, and are not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof.

<About the head>
In the above-described embodiment, ink is ejected using a piezoelectric element. However, the method for discharging the liquid is not limited to this. For example, other methods such as a method of generating bubbles in the nozzle by heat may be used.

1 printer,
20 transport unit, 21 paper feed roller, 22 transport motor (PF motor),
23 transport roller, 24 platen, 25 discharge roller,
30 Carriage unit, 31 Carriage,
32 Carriage motor (CR motor),
40 head units, 41 heads,
50 detector groups, 51 linear encoder, 52 rotary encoder,
53 Paper detection sensor, 54 Optical sensor,
60 controller, 61 interface, 62 CPU,
63 memory, 64 unit control circuit

Claims (8)

A head for ejecting ink;
A sensor,
A controller,
A printing apparatus comprising:
The controller is
The head is formed with a plurality of allowable amount determining patterns having different ink amounts within a predetermined area.
Let the sensor measure the density of the plurality of tolerance determination patterns;
Based on the measurement result of the density, an allowable amount of ink used for forming the density correction pattern is specified.
Printing device.   2. The printing apparatus according to claim 1, wherein the density correction pattern formed based on the allowable amount can change a density change direction of the density correction pattern for each color of the ink.   The printing apparatus according to claim 1, wherein the density correction pattern formed based on the permissible amount can be separated from the density correction pattern for each color of the ink.   The printing apparatus according to claim 1, wherein the density correction pattern formed based on the allowable amount is provided with a slit in the density correction pattern.   The density correction pattern formed based on the allowable amount is different from an angle in which density correction patterns of some ink colors are arranged different from an angle in which density correction patterns of other ink colors are arranged. 5. The printing apparatus according to any one of 4.   The printing apparatus according to claim 1, wherein when the tolerance determining pattern is formed, a tolerance determining pattern having a different predetermined area is formed. Forming a plurality of allowable amount determining patterns with different amounts of ink in a predetermined area in the head; and
Causing the sensor to measure the density of the plurality of tolerance determination patterns;
Identifying an allowable amount of ink used for forming a density correction pattern based on the density measurement result;
A pattern forming method including: In a printing control device that controls a printing device that includes a head that ejects ink and a sensor that measures density,
A function of causing the head to form a plurality of allowable amount determining patterns with different ink amounts within a predetermined area;
A function of causing the sensor to measure the density of the plurality of tolerance determination patterns;
A function of specifying an allowable amount of ink used for forming a density correction pattern based on the density measurement result;
A program characterized by realizing.