JP2013056468A - Apparatus and method for processing image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable execution of highly accurate calibration even for a recording medium that is not registered in a composition to perform calibration by setting color stable time after patch recording corresponding to a recording medium.SOLUTION: Standby time (color stable time) necessary to stabilize the color change of the image recorded after the end of the recording is detected (S201). Next, the target value that becomes the target density value of the recording medium that becomes an object is set. (S202). Then, the color stable time information and the target value information associated with the recording medium are stored as the calibration corresponding media information (S203).

Description

  The present invention relates to an image processing apparatus and an image processing method, and more particularly to a technique for setting a waiting time for color stabilization of a recorded patch when calibration is performed on the density or color of an image to be recorded.

  In many recording apparatuses such as printers, the density and color of an output image may change due to factors such as individual differences between apparatuses, environmental changes, and changes over time due to long-term use. Calibration is performed as a countermeasure against such a phenomenon. In general, calibration is performed by recording a patch with a printer, measuring the color using a measuring device such as a spectrocolorimeter, a scanner, and the like, and depending on the difference from the target color or density that should be output from that. Thus, image processing parameters such as a table are created or updated. By such calibration, an image to be recorded can be brought close to the target color and density regardless of a change with time of the target printer. Alternatively, by executing such calibration between a plurality of recording apparatuses, it is possible to record the same density or color between the apparatuses.

  By the way, in this calibration, when a patch is recorded, a certain long time may be required until the density or color is stabilized. For this reason, if color measurement is performed immediately after recording a patch, the color measurement result does not represent the actual recording characteristics of the recording apparatus at that time, and as a result, the image processing parameters updated by calibration are not appropriate. It can be a thing. It is also known that the time until the density or color is stabilized varies relatively greatly depending on the type of recording medium. For this reason, according to the type of recording medium for recording patches (hereinafter also referred to as recording media), a certain waiting time is set until color measurement is performed after the patches are recorded.

  In Patent Document 1, information in which a type of a recording medium and a waiting time are associated with each other is stored in advance in a memory, and when executing calibration, a patch is recorded according to the type of recording medium used for patch recording. It describes that the standby time from the end of recording to the color measurement is set.

JP 2006-255910 A

  However, with the method disclosed in Patent Document 1, for a recording medium that is not registered in advance, an appropriate standby time cannot be set for the recording medium, and as a result, highly accurate calibration cannot be performed. There is.

  The present invention relates to an image processing apparatus and an image processing method capable of executing high-precision calibration for a recording medium that is not registered in calibration for providing a color stabilization time after patch recording corresponding to the recording medium. The purpose is to provide.

  To this end, the present invention provides an image processing apparatus for performing calibration, in which a recording apparatus records a patch on a recording medium, and creates or updates an image processing parameter based on a measured value of the recorded patch. To record a measurement image on a recording medium of the same type as the recording medium used for recording, and to record a time when the density change measured for the recorded measurement image is a predetermined value or less It is characterized by comprising color stabilization time detecting means for determining a waiting time from when a patch is recorded on a recording medium to be used until the patch is measured.

  According to the above configuration, in the calibration for providing the color stabilization time after patch recording in correspondence with the recording medium, it is possible to execute highly accurate calibration even for the recording medium that is not registered.

1 is a block diagram illustrating a configuration of a recording system according to an embodiment of the present invention. It is a perspective view which shows the outline of the mechanical structure of the printer 200 shown in FIG. FIG. 2 is a block diagram illustrating a control configuration of the printer 200 illustrated in FIG. 1. FIG. 4 is a block diagram showing a configuration of image processing for generating recording data in the recording system of the present embodiment described above with reference to FIGS. (A) is a flowchart showing a procedure of image processing by the configuration shown in FIG. 4, (b) is a flowchart showing a procedure of calibration processing, and (c) is a second embodiment of the present invention. It is a flowchart which shows the calibration implementation process which considered the environmental change in a form. (A) is a flowchart which shows the process for making the recording medium which is not registered correspond to a calibration based on the 1st Embodiment of this invention, (b) is the color shown to Fig.6 (a). It is a flowchart which shows the detail of a stable time detection process, (c) is a flowchart which shows the detail of the target setting process shown to Fig.6 (a). (A) And (b) is a figure explaining the patch used in 1st Embodiment. It is a figure explaining the density | concentration change by progress of time.

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

[Overview of recording system configuration]
FIG. 1 is a block diagram showing a configuration of a recording system according to an embodiment of the present invention. In FIG. 1, a host apparatus 100 as an information processing apparatus is an apparatus connected to a printer (recording apparatus) 200 such as a personal computer. The host device 100 includes a CPU 10, a memory 11, a storage unit 13, an input unit 12 such as a keyboard and a mouse, and an interface 14 for communication with the printer 200. The CPU 10 executes various processes such as the processes described below in accordance with a program stored in the memory 11.

  The host 100 and the printer 200 are connected via an interface, and exchange of image data represented by R ′, G ′, and B ′, parameter information related to calibration, and the like in image processing described later is performed. Is called.

[Outline of recording device]
Based on the transmitted image processing information, the printer (recording apparatus) 200 performs image processing such as color processing and binarization processing described later, and recording characteristic correction processing according to the embodiment of the present invention. Also, recording is performed based on recording data obtained by image processing.

  FIG. 2 is a perspective view showing an outline of the mechanical configuration of the printer 200 described above. Each of the ink tanks 205 to 208 contains four inks (black, cyan, magenta, yellow: K, C, M, and Y), and these four types of ink are respectively stored in the corresponding recording heads 201 to 204. To supply.

  The conveyance rollers 209 and 210, together with the auxiliary rollers 211 and 212, rotate and convey (sub-scan) while sandwiching a recording medium (recording medium) 214, and also have a role of holding. The carriage 213 is mounted with ink tanks 205 to 208, recording heads 201 to 204, and a density sensor 215, and is configured to be able to reciprocate (main scan) along the X direction in the figure. During the reciprocating movement of the carriage 213, ink is ejected from the recording head, whereby an image is recorded on the recording medium. After the recording scan in the main scanning direction, the transport rollers 209 and 210 rotate to transport the recording medium (sub scanning) in the sub scanning direction (Y direction) intersecting the main scanning direction. The recording of the image on the recording medium 214 is completed by repeating the recording scanning of the recording head and the conveyance of the recording medium.

  In addition, during the reciprocating movement of the carriage 213, the density sensor 215 can be used to measure the density of a patch or the like recorded on the recording medium. The density measurement of the patches recorded on the recording medium can be performed by the density measurement scanning by the main scanning and the conveyance of the recording medium by the conveying roller.

[Outline of control system]
FIG. 3 is a block diagram showing a control configuration of the printer 200 described above. The control unit 20 of the control system includes a CPU 20a such as a microprocessor, a ROM 20c, a RAM 20b, and the like as memories. The ROM 20c stores various data such as a control program for the CPU 20a and parameters necessary for the recording operation. The RAM 20b is used as a work area for the CPU 20a, and temporarily stores various data such as image data received from the host device and generated recording data. The RAM 20b stores processing programs related to image processing and calibration described later in FIGS. 5 and 6, parameters such as target values used for calibration, and patch data for recording patches. Yes.

  The control unit 20 inputs / outputs data and parameters used for recording image data and the like to / from the host apparatus 100 via the interface 21 and various information (for example, character pitch, character type, etc.) from the operation panel 22. Process to input. Further, the control unit 20 outputs an ON / OFF signal for driving the motors 23 to 26 via the interface 21. Further, an ejection signal or the like is output to the driver 28 to control driving for ejecting ink in the recording head.

  The control system has an operation panel 22 and drivers 27, 28, and 29. The driver 27 drives the carriage driving motor 23 and the conveyance roller driving motor 25 in accordance with instructions from the CPU 20 a, and the driver 28 drives the recording head 5. The driver 29 drives the density sensor 215.

  FIG. 4 is a block diagram showing a configuration of image processing for generating recording data in the recording system of the present embodiment described above with reference to FIGS. In the image processing of this embodiment, red (R), green (G), and blue (B) color 8-bit (256 gradations) image data (luminance data) is input. Finally, a process of outputting 1-bit bit image data (recording data) discharged from the C, M, Y, and K recording heads is performed. Of course, the type of color and the gradation of the color are not limited to these values.

  First, in the host apparatus 100, image data represented by a luminance signal of 8 bits for each color of R, G, and B using a three-dimensional LUT 401 is converted into data of R ′, G ′, and B ′ of 8 bits or 10 bits for each color. Convert to This color space conversion processing (also referred to as pre-stage color processing) is performed to correct the difference between the color space represented by the R, G, and B image data on the recording target and the color space that can be reproduced by the printer 200. It is.

  Data of each color R ′, G ′, and B ′ that has been subjected to the pre-stage color processing is transmitted to the printer 200. The printer 200 uses the three-dimensional LUT 402 to convert the R ′, G ′, and B ′ color data that has been subjected to the preceding color processing into data of 10 bits for each of the C, M, Y, and K colors. In this color conversion process (also referred to as a subsequent process), input RGB image data represented by a luminance signal is color-converted into C, M, Y, and K image data used in the printer 200.

  Next, output γ correction is performed using the one-dimensional LUT 403 for each color on the 10-bit data for each of the C, M, Y, and K colors that has been subjected to the subsequent color processing. Usually, the number of dots recorded per unit area of the recording medium and the recording characteristics such as reflection density obtained by measuring the recorded image do not have a linear relationship. Therefore, 10-bit input gradation levels for C, M, Y, and K so that the input gradation levels for 10-bit each of C, M, Y, and K and the density levels of the image recorded thereby have a linear relationship. An output γ correction process is performed to correct.

  Next, in this embodiment, output of color misregistration correction is performed on the 10-bit data of each color of C, M, Y, and K for which output γ correction has been performed using the one-dimensional LUT 404 for color misregistration correction of each color. Perform gamma correction. For example, there are individual differences in the ejection amount from each nozzle in the recording head that ejects ink used in the recording apparatus, that is, the size of the dots to be recorded. For this reason, even if the number of dots to be recorded is adjusted by output γ correction using the one-dimensional LUT 403, color misregistration may occur due to the difference in the obtained optical density. For this reason, in this embodiment, the color misregistration correction output γ correction is performed by the color misregistration correction one-dimensional LUT 404 for each color of C, M, Y, and K. The one-dimensional LUT for color misregistration correction is an image processing parameter to be created or updated by calibration described in each embodiment described later.

  FIG. 5A is a flowchart showing a procedure of image processing according to the configuration described above with reference to FIG. The input image data undergoes color space conversion processing in the host device 100 (S501). Thereafter, color conversion processing is performed on the image data subjected to color space conversion transferred to the printer 200 (S502), and thereafter output γ processing (S503) and color misregistration correction processing are sequentially performed (S504). ). Thereafter, data of 10 bits for each color of C, M, Y, and K is converted into binary data of 1 bit for each color of C, M, Y, and K by binarization processing (quantization processing) (S505).

  Next, calibration in the present embodiment will be described. Calibration is executed by inputting a calibration start command as part of user input via the input unit 12 of the host device 100 or processing by the CPU 10. Alternatively, calibration is executed by inputting a calibration start command as part of user input via the operation panel 22 of the printer 200 or processing by the CPU 20a.

  FIG. 5B is a flowchart showing the procedure of the calibration process. First, a calibration patch is recorded on a recording medium (S401).

  FIG. 7B is a schematic diagram showing the calibration patch. Patches C1 to C8 are recorded with C ink, patches M1 to M8 are recorded with M ink, patches Y1 to Y8 are recorded with Y ink, and patches K1 to K8 are recorded with K ink. In the figure, the numbers 1 to 8 for identifying patches correspond to the density gradation (the amount of ink recorded per unit area) of the patch to be recorded, with 1 being the lowest gradation patch, and a large numerical value. As a result, the gradation becomes higher, and 8 is the highest gradation patch. In this embodiment, each color has 8 gradations, but the present invention is not limited to this. In the present embodiment, the patches are arranged in the order of density gradation, but it is needless to say that the present invention is not limited to this.

  Immediately after the recording of the recorded patch, as described above, the color changes with time according to the progress of the fixing of the coloring material to the recording medium and the evaporation of moisture in the ink. Therefore, it is not suitable for calibration. Therefore, after waiting for the color change to stabilize after finishing the patch recording (S402), the patch is measured by the density sensor 215, and the measured density value is stored in the memory. Then, the measured density value of each patch is compared with a predetermined target density value, which is a predetermined target value called a target value, so that the color density correction 1 is used so that the density of the patch when recorded approaches the target value. The dimension LUT is calibrated (S404). This target value is determined for each color and for each patch (specific gradation value). For example, as described above, the reference of the ejection amount (dot size) of each nozzle of the recording head Are defined as gradation values (density values) that can realize the density corresponding to the above. The one-dimensional LUT for color misregistration correction calibrated as described above is created for each recording medium type, and the one-dimensional LUT for color misregistration correction is stored in the memory of the recording apparatus main body.

  In the following, some embodiments of the color stabilization time setting process in calibration in the case of using an unregistered recording medium according to the image processing configuration according to the embodiment described above will be described.

(First embodiment)
As described above, immediately after recording a calibration patch, the color change over time is large due to the fixing behavior of the color material and the effect of moisture evaporation, and the concentration measurement is performed after a waiting time is provided until the color change is stabilized. There is a need to. FIG. 8 is a graph showing changes in the density value of the patch according to the elapsed time after recording. When the recording medium A and the recording medium B are compared, the recording medium B takes a longer time after the recording until the measured optical density is stabilized (substantially does not change). Therefore, when the calibration is performed on the recording medium B, it is necessary to provide a longer standby time than when the calibration is performed on the recording medium A.

  In the present embodiment, when calibration is performed with an unregistered recording medium, a necessary waiting time is detected and set.

  FIG. 6A is a flowchart showing a process for making a recording medium not registered correspond to calibration. This process is executed by instructing a calibration-compatible medium addition process by the host device 100 or the printer 200 in the same manner as the start of calibration described above. Note that this calibration-compatible medium addition processing can be, for example, processing that is performed in combination with processing for setting a recording medium used for recording, which is selected by a printer user. That is, it can be a process that is performed together when setting the type of recording medium to be newly used.

  First, a standby time (color stabilization time) required from the end of recording until the color change of the recorded image is stabilized is detected (S201). Next, a target value that is a target density value of the target recording medium is set. (S202). Then, the color stabilization time information and target value information associated with the recording medium are stored as calibration-compatible media information (S203).

  The calibration-compatible media information can be transmitted from the printer to the host device 100 via the interface. It is also possible to update the information recorded in the memory of the printer by transmitting calibration compatible media information from the host device 100 to the printer. Therefore, in this case, the calibration-compatible media information created by one specific printer can be associated with a plurality of printers of the same type. As a result, it is possible to perform highly accurate calibration using a recording medium that is not registered, and it is possible to prevent color changes due to individual differences among printers.

  FIG. 6B is a flowchart showing details of the above-described color stabilization time detection process (S201).

  First, a patch for detecting the color stabilization time is recorded on the recording medium (S101). FIG. 7A is a schematic diagram illustrating a chart of a patch for detecting a color stabilization time. In FIG. 7A, the measurement images, patches Ct1 and Ct2, are recorded with C ink, patches Mt1 and Mt2 with M ink, patches Yt1 and Yt2 with Y ink, and patches Kt1 and Kt2 with K ink, respectively. . The numbers 1 and 2 correspond to the density gradation (the amount of ink recorded per unit area) of the patch. Here, the patch Ct1 has the same tone value as the patch C6 and the patch Ct2 of the calibration patch shown in FIG. 7B, respectively. The same applies to M, Y, and K. Since the color change with the passage of time is greatly affected by the progress of ink drying and fixing, the high density part (high gradation part) is often larger than the low density part. However, when the amount of ink to be recorded per unit area is excessively large, the variation in density value may be small. Therefore, the color stabilization time detection chart includes the patch Ct2 (same gradation as the patch C8) that is the maximum gradation value and the patch Ct1 (same gradation as the patch C6) that is slightly lower than the patch Ct2. 2 gradations. The same applies to M, Y, and K. As described above, the color stabilization time detection patch can be a patch having only a high gradation part and the number of gradations can be reduced as compared with the calibration patch. That is, the recording amount is reduced. Therefore, the amount of ink used and the amount of recording media can be reduced, and the time required for measurement can be shortened. In the present embodiment, each color has two gradations, but the present invention is not limited to this. The number of gradations and the density gradation value are preferably optimized in accordance with the type of recording medium and ink characteristics. For example, when plain paper is used, the amount of ink recorded per unit area is relatively small for image design, so the maximum gradation value is small and the number of gradations can be reduced. On the other hand, when glossy paper is used, the amount of ink recorded per unit area is relatively large for image design, so it is desirable to increase the maximum gradation value and the number of patches.

  Referring to FIG. 6B again, after patch recording (S101), timer recording for color stabilization time detection is started from the point when recording of this patch is completed (S102), and the patch is detected by the density sensor 215. Measure (S103). It takes 1 second to measure the density of all patches. The measured value D (T, P) is stored for each count time (T) of the timer and each patch type (P). Thereafter, after waiting for 9 seconds (S104), the patch is again measured by the density sensor (S105). The time interval from the previous concentration measurement is 10 seconds, which is a sum of 9 seconds standby and 1 second measurement time by the concentration sensor 215.

  Next, it is determined whether or not the color change is stable (S106). For each type of recording medium on which the patch is recorded, the difference between the measured density value D (T, P) and the density value D (T-10, P) related to the previous measurement is calculated to calculate the density change amount. When the calculated density change amount of all patches is less than the set threshold value 0.005 (less than a predetermined value), it is determined that the color change is stable, and the timer count value T at that time is determined as the color stabilization time. Ta is determined. If there is a patch whose density change amount is greater than or equal to the threshold value 0.005, it is determined that the color change is not stable, and after waiting for 9 seconds again (S104), the patch is measured (S105), It is determined whether or not the difference from the measured value is less than the threshold value 0.005 (S106). Thereafter, the same processing is repeated until the difference from the previous measurement value is less than the threshold value 0.005, and the color stabilization time is calculated. The calculated color stabilization time is stored in the memory in association with the type of recording medium.

  Note that the threshold value used for determination and the time interval between measurements are not limited to the numerical values described in the present embodiment. For example, when it is desired to detect color stability with higher accuracy, it can be realized by setting the threshold value to a smaller value and widening the time interval between measurements.

  FIG. 6C is a flowchart showing details of the target setting process (S202) described above with reference to FIG.

  First, a target setting patch is recorded on a recording medium (S301). Since the target setting patch is a target value at the time of calibration execution, the calibration patch described in FIG. 7B has the same number of patches and gradation values.

  Next, after the recording is completed, the system waits for the color stabilization time Ta obtained in the above-described color stabilization time detection (S201) (S302). Thereafter, the patch is measured by the density sensor 215 (S303), and based on the measurement result, the measured value is stored as a target value in the memory in association with the recording medium type (S304).

  As described above, it is possible to set a stable color as a target value by measuring the target setting patch after providing a standby time necessary for color stabilization after the end of recording. As described above, this target value is set when, for example, a new type of recording medium is set, and thereafter, when calibration corresponding to the set recording medium is performed, the target value is set. Used as a value.

  As described above, using the calibration-compatible media information (recording media type, color stabilization time, target value) acquired by the above-described processing for associating the recording media not registered in advance with the calibration, the recording media is calibrated. Can be executed. Among the calibration processes described with reference to FIG. 5B, the color stabilization time standby (S402) allows the density value after color stabilization to be measured by setting the color stabilization time detected by the above-described method. . Then, the measured value after the color stabilization and the target value are compared, and an optimal one-dimensional LUT for color misregistration correction is created (S404) and applied at the time of image processing, so that a target color can be output. Highly accurate calibration can be performed.

(Second Embodiment)
In the first embodiment described above, the process for enabling highly accurate calibration using a recording medium that has not been registered has been described. However, the application of the present invention is not limited to this form. The second embodiment of the present invention is applied to a case where a media that can be calibrated in advance is used, and until the color change is stabilized after the end of recording due to environmental changes such as temperature and humidity. The present invention relates to processing for realizing high-precision calibration even when time changes.

  FIG. 5C is a flowchart illustrating a calibration execution process in consideration of environmental changes in the present embodiment. First, before the calibration execution steps S401 to S404 described in FIG. 5A of the first embodiment shown in step S602, the color stabilization time detection step described using FIG. 6B in step S601. To implement. In this way, by detecting the color stabilization time in the environment where the printer is placed before calibration is performed, the waiting time required from the calibration patch recording to the start of measurement can be set with higher accuracy. As a result, highly accurate calibration can be realized.

(Other embodiments)
The above-described embodiment has been particularly described as executing the calibration-compatible medium addition processing in the recording apparatus. In this respect, the recording apparatus of each of the above embodiments constitutes an image processing apparatus. Further, the calibration-compatible medium addition process may be executed in the host device, and in this case, the host device constitutes the image processing device.

In the above embodiment, the patch is measured by the density sensor. However, the application of the present invention is not limited to this, and any patch that can measure a color change may be used. For example, the L ^* a ^* b ^* value may be measured using a spectrocolorimeter, the color change amount may be converted to ΔE, and the color change stability may be determined.

20 Control unit 100 Host device 200 Recording device (printer)
201-204 Recording head 215 Density sensor

Claims (3)

An image processing apparatus for performing calibration, which records a patch on a recording medium in a recording apparatus and creates or updates an image processing parameter based on a measured value of the recorded patch,
A measurement image is recorded on the same type of recording medium as the recording medium used for recording the patch, and the patch is recorded for a time when the change in density measured for the recorded measurement image is less than a predetermined value. A color stabilization time detecting means for determining a waiting time from when a patch is recorded on a recording medium to be measured until the patch is measured;
An image processing apparatus comprising: The patch is recorded on a recording medium used for recording the patch, and after waiting for the waiting time determined by the color stabilization time detection unit, the recorded patch is measured, and the creation is performed based on the measurement result. Or target setting means for setting a target value to be a target value of the image processing parameter to be updated,
The image processing apparatus according to claim 1, further comprising: An image processing method for executing calibration, in which a patch is recorded on a recording medium in a recording apparatus, and an image processing parameter is created or updated based on a measured value of the recorded patch,
A measurement image is recorded on the same type of recording medium as the recording medium used for recording the patch, and the patch is recorded for a time when the change in density measured for the recorded measurement image is less than a predetermined value. A color stabilization time detection step for determining a waiting time from when a patch is recorded on a recording medium to be measured until the patch is measured;
An image processing method characterized by comprising:

Images