JP2013173290A - Printing apparatus, pattern forming method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a density correction pattern to stably obtain a measurement result of a sensor.SOLUTION: A printing apparatus includes: a head for discharging ink; a sensor; and a controller. The controller causes the head to form a density correction pattern that causes the sensor to read the density and has a slit.

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
It is a printing apparatus that causes the head to form a density correction pattern for causing the sensor to read the density and having a slit.

  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 printing apparatus 1. FIG. FIG. 2A is a schematic diagram of the overall configuration of the printing apparatus 1, and FIG. 2B is a cross-sectional view of the overall configuration of the printing apparatus 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 at the time of printing and measurement of the density correction processing of the reference example. It is explanatory drawing of correction | amendment of a certain gradation value X. FIG. 6A and 6B are explanatory diagrams of a state in which the medium is deformed so as to wave, and FIGS. 6C and 6D are explanatory diagrams of light reception by the optical sensor 54. FIG. FIG. 7A is a diagram of a density correction pattern in the present embodiment, and FIG. 7B is an explanatory diagram of the relationship between the slit and the spot diameter of the optical sensor 54. It is a measured value of a strip-shaped fill pattern.

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
It is a printing apparatus that causes the head to form a density correction pattern for causing the sensor to read the density and having a slit.
When ink is ejected to the medium, the medium may be deformed by the liquid component, and as a result, the measurement value from the sensor may become unstable. Since it is divided, it is possible to make it difficult for the ink to be deformed. Then, it is possible to form a density correction pattern that can stably obtain the measurement result of the sensor.

In this printing apparatus, it is preferable that the slit provided in the density correction pattern has a width smaller than a spot diameter when the sensor reads the density correction pattern.
By doing so, it is possible to form a density correction pattern that makes it possible to stably obtain the measurement result of the sensor while making it difficult to cause measurement errors due to the sensor.

When the movement speed of the sensor when reading the density correction pattern is the first movement speed, a slit having a first width is formed, and the movement speed of the sensor when reading the density correction pattern. In the case of a second movement speed that is faster than the first movement speed, it is desirable that a slit having a second width wider than the first width is formed.
When the moving speed of the sensor is fast, the influence of the error caused by the slit generated on the measured value of the sensor is small. Thus, the slit width corresponding to the moving speed of the sensor can be provided.

Further, the width of the slit is such that the difference between the measured value when the slit is provided and the measured value when the slit is not provided is within an error range of the sensor output. Is desirable.
By doing so, it is possible to form a density correction pattern that can stably obtain the measurement result of the sensor while the error due to the slit is within the error range of the sensor.

The slit is preferably provided when the measurement result of the sensor is not stable.
Thus, when the sensor measurement result is stable, a density correction pattern without a slit is used, and when the sensor measurement result becomes unstable, a density correction pattern with a slit is used. be able to.

The slit is preferably provided in a patch having the highest density among the density correction patterns.
In this way, since the slit can be provided in the highest density patch having the most liquid component of the ink, it is possible to form a density correction pattern in which deformation of the medium is less likely to occur in the portion of the highest density patch. it can.

In addition, at least the following matters will become clear from the description of the present specification and the accompanying drawings. That is,
A pattern forming method in which a density correction pattern for causing a sensor to read a density is formed on a head,
In the pattern forming method, a slit is provided in the density correction pattern.
When ink is ejected to the medium, the medium may be deformed by the liquid component, and as a result, the measurement value from the sensor may become unstable. Since it is divided, it is possible to make it difficult for the ink to be deformed. Then, it is possible to form a density correction pattern that can stably obtain the measurement result of the sensor.

In addition, at least the following matters will become clear from the description of the present specification and the accompanying drawings. That is,
A program for causing the head to form a density correction pattern for causing the sensor to read the density,
The density correction pattern is provided with a slit.
When ink is ejected to the medium, the medium may be deformed by the liquid component, and as a result, the measurement value from the sensor may become unstable. Since it is divided, it is possible to make it difficult for the ink to be deformed. Then, it is possible to form a density correction pattern that can stably obtain the measurement result of the sensor.

=== Embodiment ===
<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 outputs 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 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, by intermittently ejecting ink while the head 41 is moving in the moving direction, dot lines (raster lines) along the moving direction are formed on the paper.

  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 illustrated in FIG. 4A, the printer 1 that has received an instruction from the computer 110 discharges black ink from the black ink nozzle group K of the head 41 to perform density correction including a plurality of (here, nine) square patches. The pattern for use is formed on the medium. Each patch is formed by applying a different amount of ink per unit area according to a specific gradation value. However, an ideal ink amount (ink amount per unit area) is not applied to each patch due to the influence of manufacturing errors and the like. For example, when the ink droplets ejected from the head 41 are small, the amount of ink per unit area is small, and a light patch 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 patch using the optical sensor 54, and transmits the measured value (output 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 a patch having a specific gradation value X1 is measured.
Praw (255) is a measured value of the optical sensor when a patch (so-called solid paint pattern) having a specific gradation value of 255 is measured.
Praw (0) is a measured value of the optical sensor of the patch whose specific gradation value is 0.
P (X1) is a normalized measurement value.

  In this embodiment, the optical sensor outputs a low value when the density is high (dark). A high value is output 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. 5 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. The black circles in the figure indicate the measured values (normalized measured values) of nine patches. P (X) in the figure shows a graph of actual density obtained from the measured value of the patch. P (X) is obtained, for example, by linearly 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 A, it is printed with a density P (A) that is lighter than the target density T (A). Therefore, for example, when printing an image having a gradation value A, the gradation value A is corrected to the gradation value A ′ (= A + α) by the correction value α, and the image is displayed according to the corrected gradation value A ′. If printing is performed, an image having an initial target density T (A) can be obtained. Thus, the computer 110 calculates a correction value for each gradation value based on the measured value. The calculated correction value is stored in the storage device of the computer 110.

  When the image is printed after obtaining the correction value, the computer 110 corrects the gradation value (for example, gradation value A) of each pixel constituting the image with the correction value (for example, correction value α), and after the correction. The image is printed based on the tone value (for example, tone value A ′). 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 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.

6A and 6B are explanatory diagrams showing a state in which the medium is deformed so as to wave. FIG. 6A is a top view of the medium. 6B is a cross-sectional view taken along the line AA in FIG. 6A.
As shown in FIG. 6A, 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. 6B.

  6C and 6D are explanatory diagrams of light reception by the optical sensor 54. The optical sensor 54 irradiates a medium with light from a light source, receives light reflected by the medium with a light receiving sensor, and detects a signal corresponding to the amount of received light. As shown in FIG. 6C, if the distance between the optical sensor 54 and the medium is close, the optical path is shortened and the intensity of reflected light increases. Conversely, if 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 FIG. 6B and FIG. 6C, the distance between the optical sensor 54 and the medium fluctuates.

  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 purpose of the optical sensor 54 is 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 in FIG. 6D). 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 has a local inclination, 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. 6D). 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. Therefore, it is desirable to form a density correction pattern that can stably obtain the measurement value of the optical sensor 54. Here, a density correction pattern that provides a stable output value of the optical sensor 54 is provided by the method described below.

  FIG. 7A is a diagram of a density correction pattern in the present embodiment. Here, for ease of explanation, a density correction pattern of only the black ink K is shown. Therefore, it is also possible to form density correction patterns for the cyan ink C, magenta ink M, and yellow ink Y described above.

  In the density correction pattern shown in FIG. 7A, patches printed at a plurality of densities are arranged in the moving direction of the optical sensor 54. As described above, each of these patches can be sequentially read by the optical sensor 54.

  Among the density correction patterns in this embodiment, slits are formed in patches with high density. Specifically, among the patches printed with the black ink K, slits are formed for those with gradation values of “224” and “255”.

  As described above, the measured value of the optical sensor 54 may become unstable in a region where the amount of ink per unit area is large. However, since the amount of ink per unit area can be reduced by forming a region where ink is not ejected for a patch having a high gradation value, that is, a high density, an optical sensor that measures this patch. The 54 measured values can be made stable.

  FIG. 7B is an explanatory diagram of the relationship between the slit and the spot diameter of the optical sensor 54. In FIG. 7B, the slit provided in the patch is narrower than the spot diameter of the optical sensor 54 (the diameter of the detection region). By doing in this way, the measurement error by providing a slit can be made small. The slit is provided to have a width with respect to the moving direction of the optical sensor 54.

  In addition, the width of the formed slit can be varied according to the moving speed when the optical sensor 54 performs density measurement. For example, when the moving speed of the optical sensor 54 is slow, the width of the slit can be narrowed. On the other hand, when the moving speed of the optical sensor 54 is fast, the width of the slit can be widened. This is because when the moving speed of the optical sensor 54 is high, the influence of the error due to the slit in the measurement value is small. By doing in this way, the width | variety of a slit can be varied according to the moving speed of the optical sensor 54. FIG.

  The width of the slit is such that the difference between the measured value when the slit is provided and the measured value when the slit is not provided is within the error range of the measured value of the optical sensor 54. Is desirable. By doing so, it is possible to form a density correction pattern that can stably obtain the result of the optical sensor 54 while keeping the error due to the effect of the slit within the error range of the optical sensor 54.

=== Other Embodiments ===
In the above-described embodiment, slits are formed in advance for a patch having a high density.However, it is determined whether cockling occurs or not, and it is confirmed that the medium causes cockling. It is good also as forming. In this case, when the density correction pattern is printed on a medium in which cockling does not occur, the measurement result is stabilized, and a belt-like paint pattern as shown in FIG. 6A is printed on the medium. Then, the density of the filled pattern is measured. Further, when the density correction pattern is printed on the medium in which cockling occurs, the pattern in which the slit as shown in FIG. 7A is formed is printed on the medium on the assumption that the measurement result is not stable. Then, the density is measured for the pattern in which the slit is formed. In addition, when measuring without contacting the medium as in the optical sensor 54, it is assumed that cockling occurs, and a pattern having slits as shown in FIG. In the case of using a sensor for contact measurement, a band-like paint pattern as shown in FIG. 6A described above may be printed on the medium, assuming that cockling does not occur.

  FIG. 8 shows measured values of the band-shaped fill pattern. In FIG. 8, the measured density has a predetermined amplitude, but when the width of the amplitude exceeds a predetermined amount, it can be determined that the medium is likely to cause cockling.

  And a slit can be formed only about the medium which tends to produce cockling in this way. Moreover, although it is a patch which forms a slit, it is not restricted to the patch with the highest density. In the above-described embodiment, slits are formed for the gradation values “224” and “255”. However, slits can be formed for patches having gradation values lower than this. A plurality of slits may be provided in one patch.

  In the above-described embodiment, the printer 1 has been described as a printing apparatus. However, the present invention is not limited to this, but is not limited to this. It is also possible to embody the present invention in a liquid ejecting apparatus that ejects or ejects a 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
A printing apparatus for causing the head to form a density correction pattern for causing the sensor to read the density and having a slit.   The printing apparatus according to claim 1, wherein the slit provided in the density correction pattern has a width smaller than a spot diameter when the sensor reads the density correction pattern. When the movement speed of the sensor when reading the density correction pattern is the first movement speed, a slit having a first width is formed,
When the movement speed of the sensor when reading the density correction pattern is a second movement speed that is faster than the first movement speed, a slit having a second width wider than the first width is formed. The printing apparatus according to claim 1 or 2.   The width of the slit is a width in which a difference between a measured value when the slit is provided and a measured value when the slit is not provided is within an error range of the sensor output. The printing apparatus in any one of 1-3.   The printing apparatus according to claim 1, wherein the slit is provided when a measurement result of the sensor is not stable.   The printing apparatus according to claim 1, wherein the slit is provided in a patch having the highest density among the density correction patterns. A pattern forming method in which a density correction pattern for causing a sensor to read a density is formed on a head,
A pattern forming method, wherein the density correction pattern is provided with a slit. A program for causing the head to form a density correction pattern for causing the sensor to read the density,
The density correction pattern is provided with a slit.