JP2007279164A - Image processing device, image processing method and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing device, an image processing method and a program to achieve printing stable in colors by performing measurement in such a state that the density characteristic of a low-density area where the reading accuracy of a sensor is low is made higher to such density that the reading accuracy of the sensor is high, and obtaining the accurate density characteristic of the low-density area. <P>SOLUTION: In a printer 102, the image processing device forms patch patterns at a plurality of gradation levels, measures the density of each patch pattern by using the sensor, and interpolates the measured density to calculate the density characteristic. As for a plurality of gradation levels in the density area where it is difficult to measure the density of the patch pattern by the sensor, the patch pattern is formed by mixing two kinds of toners having the same color but different in density. Then, a difference value between the density of the formed patch pattern and the density of a patch pattern formed by using the first toner that is either of the two kinds of toners is calculated. Thereafter, the density characteristic of the density area of the second toner that is the other of the two kinds of toners is calculated based on the calculated difference value. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image processing apparatus, an image processing method, and a program for adjusting the density of an image printed by a printing apparatus.

  In general, the printing apparatus changes the density and the color of printed matter due to many factors such as environmental conditions such as air temperature, humidity, and body temperature, the number of printed sheets, and deterioration of consumable parts. Therefore, in order to perform printing with a stable color even when density fluctuations occur, it is necessary to perform density adjustment so that the same density can always be output.

Conventionally, the density of a printing apparatus is adjusted by measuring the density of a patch pattern of a predetermined gradation level using a sensor in the printing apparatus, obtaining the density characteristic from the measured density value, and the density characteristic being the target density characteristic. A density correction table is created so that By correcting the input gradation level using the density correction table, it becomes possible to always obtain a target density value. Then, in order to obtain density characteristics for all input gradation levels, for example, gradation levels 00H to FFH, patch patterns of a plurality of gradation levels are created in density adjustment, and the density is measured.
Japanese Patent Laid-Open No. 10-16304

  In the density correction method described above, density measurements are performed at a plurality of gradation levels in order to obtain density characteristics for the entire input gradation level. However, for tone levels that are lower than the readable density value of the sensor, the density characteristics are obtained by predicting from the measured density value of the readable density level. There is a problem that an error may occur in the correction.

  Therefore, in printing devices that require high image quality that expresses colors by mixing light toner with low density of the same color and dark toner with high density, high-precision density correction is required, and low-density correction errors Must be small enough.

  The present invention has been made in view of such circumstances, and an object thereof is to provide the following image processing apparatus, image processing method, and program. In other words, the density characteristics in the low density area where the sensor reading accuracy is low are increased to a density where the sensor reading precision is high, and measurement is performed to obtain accurate density characteristics in the low density area, and printing with stable color is performed. Can do.

In order to solve the above problems, the present invention generates a patch pattern having a plurality of gradation levels, measures the density of each patch pattern using a sensor, and calculates density characteristics by interpolating the measured densities. An image processing apparatus,
For a plurality of gradation levels in a density range where it is difficult to measure the density of the patch pattern by the sensor, the density of the patch pattern generated by mixing two types of toner of the same color and different densities, and the two types First calculating means for calculating a difference value between the density of a patch pattern generated using one of the first toners;
And second calculating means for calculating a density characteristic of the density region of the second toner of the other of the two types of toner based on the difference value.

In order to solve the above problems, the present invention generates a patch pattern of multiple gradation levels, measures the density of each patch pattern using a sensor, and interpolates the measured density to obtain density characteristics. An image processing method to calculate,
For a plurality of gradation levels in a density range where it is difficult to measure the density of the patch pattern by the sensor, the density of the patch pattern generated by mixing two types of toner of the same color and different densities, and the two types A first calculation step of calculating a difference value between the density of a patch pattern generated using one of the first toners;
And a second calculation step of calculating a density characteristic of the density range of the other second toner of the two types of toner based on the difference value.

Furthermore, in order to solve the above-described problem, a program according to the present invention provides:
A computer that generates patch patterns of multiple gradation levels, measures the density of each patch pattern using a sensor, and calculates density characteristics by interpolating the measured densities.
For a plurality of gradation levels in a density range where it is difficult to measure the density of the patch pattern by the sensor, the density of the patch pattern generated by mixing two types of toner of the same color and different densities, and the two types A first calculation procedure for calculating a difference value between the density of a patch pattern generated using one of the first toners;
And executing a second calculation procedure for calculating a density characteristic of the density region of the other second toner of the two types of toner based on the difference value.

  According to the present invention, the density characteristics in the low density region where the reading accuracy of the sensor is low are increased to a density where the reading accuracy of the sensor is high, and the measurement is performed to obtain the accurate density characteristics in the low density region. Printing can be performed.

  Details of image processing in a printing apparatus (printer) according to an embodiment of the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram for explaining a control configuration in a printer 102 according to an embodiment of the present invention. In FIG. 1, reference numeral 101 denotes a host computer which sends print information for performing print processing such as color information, characters, graphics, images, and the number of copies to the printer 102. The printer 102 includes a data processing unit 103 and a printer engine 111 that actually forms an image based on an image signal transmitted from the data processing unit 103.

  Hereinafter, a main configuration and operation for image processing by the data processing unit 103 will be described.

  In the data processing unit 103, reference numeral 104 denotes an interface unit (I / F) that controls transmission / reception of print information with the host computer 101, and reference numeral 105 denotes a reception buffer that holds input print information. The image processing unit 106 also generates a bit image from information such as color, characters, graphics, and image images that are print information input from the host computer 101. Further, density correction using the density conversion table generated by the density correction processing unit 107 is also performed by the image processing unit 106. The image processing unit 106 and the density correction processing unit 107 will be described in detail later. The bit image generated by the image processing unit 106 is sent to the printer engine 111 and formed on a recording medium.

  Reference numeral 109 denotes a central processing unit (CPU) that determines and controls various processes in accordance with a control program 108a stored in the ROM 108. Reference numeral 110 denotes a ROM (Read Only Memory), which stores various control programs 108a including the processing programs shown in the flowcharts of FIGS. 3, 4, 10, and 16.

  Furthermore, 110 is a RAM (Random Access Memory) that stores data, status information, and a density correction table 110b for the CPU 109 to perform determination control of each process in accordance with a program stored in the ROM 108, and is used as a work area 110a. is there.

  FIG. 2 is a block diagram illustrating a detailed configuration of the image processing unit 106 of the printer 102 illustrated in FIG. 1. First, the rendering processing unit 201 generates a bitmap image of the color signal RGB from the input print information and stores it in the RGB data storage unit 202. The stored RGB data is converted from the RGB data into six color signals which are the color signals of the printer in the color conversion processing unit 203. That is, it is converted into six colors of Cyan (C), Magenta (M), Yellow (Y), Black (K), LightCyan (LC), and Light Magenta (LM). The data converted into the six color signals is subjected to density correction using the density correction table generated by the density correction processing unit 107 in the density conversion unit 204. Then, halftone processing is performed in the halftone processing unit 205 so as to match the output gradation of the printer, and is sent to the printer engine 111.

  Next, density correction processing in the present embodiment will be described. FIG. 3 is a flowchart for explaining the procedure of density correction processing in the density correction processing unit 107. In the density correction process, first, the density characteristic of the medium / high density region is calculated by the medium / high density region process (step S301). Next, the density characteristics of the low density region are calculated by the low density region processing (step S302). Then, the density correction table creation process calculates the overall density characteristics from the calculated density characteristics in the middle and high density areas and the density characteristics in the low density area, and converts the density so that the density characteristics become the specified density characteristics. A correction table is created (step S303).

  FIG. 4 is a flowchart for explaining a detailed procedure of the middle / high density region processing (step S301) in FIG.

  First, a plurality of gradation level patch patterns are generated (step S401). Then, the density of the patch pattern generated in step S401 is measured in the printing apparatus (step S402), and the density characteristic in the middle and high density region is calculated from the measured value (step S403).

  FIG. 5 shows an example of a patch pattern generated by the process of step S401 of FIG. In the present embodiment, as shown in FIG. 5, a plurality of patch patterns having gradation levels of 20%, 40%, 60%, and 80% covering the medium density range to the high density range are generated.

  FIG. 6 is a diagram for explaining a specific apparatus example for performing density measurement in the printer 102 for performing the process of step S402 in FIG. That is, the patch pattern generated in step S 401 is drawn on the intermediate transfer member 602 in the printer 102, and the density thereof is measured using the sensor 601.

  FIG. 7 is a diagram illustrating an example of density characteristics in the middle and high density range. By interpolating the density values of the plurality of gradation levels measured in step S402, the density characteristics in the middle and high density range are calculated.

  Next, details of the low density region processing in step S302 will be described. The low density region processing is performed for colors having the same color and having dark and light toners having different densities. In the printer using the six-color toner (ink) of this embodiment, a combination of dark toner Cyan and light toner Light Cyan, and a combination of dark toner Magenta and light toner Light Magenta are applicable.

  FIG. 8 is a diagram showing an example of ideal toner density characteristics. 8A shows ideal density characteristics of light toner, and FIG. 8B shows ideal density characteristics of dark toner. Note that the light toner has a density at the maximum gradation level and is almost half that of the dark toner.

  FIG. 9 is a diagram illustrating an example of density reading characteristics of the sensor in the printer 102. Since the sensor has a lower reading accuracy in the low density range (0.2 or less) than in the middle and high density range, it is difficult to obtain an accurate density value even if the low density patch pattern is directly measured. Therefore, in the low concentration region processing, an accurate concentration value is measured by performing measurement in the medium and high concentration regions where the sensor reading accuracy is good.

  FIG. 10 is a flowchart for explaining a detailed procedure of the low density region processing (step S302) of FIG. First, one light toner patch pattern of light toner solid coating is generated (step S1001), and dark toner patch patterns of a plurality of gradation levels in a low density region of dark toner are generated (step S1002). Next, each dark toner patch pattern generated in step S1002 is synthesized on the light toner patch pattern to generate a dark / light mixed color patch pattern (step S1003). Then, the light toner patch pattern and each of the light and dark color mixture patch patterns are drawn on the intermediate transfer body 602 in the density measuring device in the printer 102 shown in FIG. 6 (step S1004).

  Thereafter, the density of the light toner patch pattern and each of the light and dark color mixture patch patterns is measured by the sensor 601 (step S1005). Then, the density value of each dark toner patch pattern before synthesis is calculated by subtracting the measured density value of the light toner patch pattern from the measured density value of each dark and light mixed color patch pattern (step S1006). Further, by interpolating the calculated density value of each dark toner patch pattern, the density characteristics of the dark toner in the low density area are calculated (step S1007).

  FIG. 11 is a diagram illustrating an example of a light toner patch pattern. This is a solid patch pattern (A) with a light toner gradation level of 100%.

  FIG. 12 is a diagram illustrating an example of a patch pattern having a gradation level in a low density region of dark toner. In this embodiment, as shown in FIG. 12, a plurality of gradation levels in the low density region are 2% (B1), 4% (B2), 6% (B3), 8% (B4), and 10% (B5). The five patch patterns are generated.

  FIG. 13 is a diagram illustrating an example of a light and dark mixed color patch pattern. In this embodiment, the light toner patch pattern (A) and the respective dark toner patch patterns (B1, B2, B3, B4, B5) are combined to form a mixed color patch pattern (C1, C2, C3, C4, C5). Generated. Then, the density of the generated light toner patch pattern (A) and the color mixture patch pattern (C1, C2, C3, C4, C5) is measured by a density measuring device in the printing apparatus.

  FIG. 14 is a diagram illustrating an example of density measurement results of the light toner patch pattern (A) and the light / dark mixed color patch patterns (C1, C2, C3, C4, C5). FIG. 15 is a diagram illustrating an example of density characteristics of the dark toner in the low density region. That is, the density of the dark toner patch pattern (B1, B2, B3, B4, B5) is calculated by subtracting the light toner patch pattern (A) from the density of the dark / light mixed color patch pattern (C1, C2, C3, C4, C5). And interpolate. When the density characteristics of the dark toner in the low density area are obtained in this way, the density characteristics shown by the solid line in FIG. 15 are obtained.

  Next, details of the density correction table creation processing (step S303) in FIG. 3 will be described. FIG. 16 is a flowchart for explaining a detailed procedure of the density correction table creation process (step S303) of FIG.

  First, the density characteristics of the medium and high density areas of the dark toner calculated in the middle and high density area processing (step S301) are acquired (step S1601), and the density of the dark toner and low density area calculated in the low density area processing (step S302). A characteristic is acquired (step S1602). Then, the density characteristics of the low density area and the density characteristics of the middle and high density areas are combined to obtain the overall density characteristics of the dark toner (step S1603), and the gradation level is corrected so that the density characteristics become the ideal density characteristics. A density correction table to be created is created (step S1604).

  FIG. 17 is a diagram illustrating an example of the entire density characteristic. That is, when the density characteristics in the low density range shown in FIG. 15 and the density characteristics in the middle and high density range shown in FIG. 7 are combined, the overall density characteristics shown by the solid line in FIG. 17 are obtained. FIG. 18 is a diagram for explaining a density correction table for correcting the gradation level so that the entire density characteristic indicated by the solid line in FIG. 17 becomes the ideal density characteristic indicated by the broken line. The generated density correction table is used by the density conversion unit 204 as a correction table for converting the input gradation level to a gradation level that provides an ideal density.

  As described above, the density of the patch pattern is detected by mixing the dark toner patch pattern having a gradation level lower than the sensor readable density on the light toner patch pattern having a specific density. To a readable density. Then, the density characteristic of the low density gradation level of the dark toner is calculated by using the measurement value of the mixed color patch pattern and the measurement value of the light toner patch pattern, so that the low density gradation level of the dark toner is accurately determined. Density correction is possible.

<Other embodiments>
In the above-described embodiment, the density correction processing for the dark toner having the same color and the light toner and the dark toner has been described with reference to FIGS. 3 to 18. However, the same processing is performed by replacing the light toner and the dark toner. As a result, the light toner density correction processing can be performed.

  Further, for the color of only the dark toner having no light toner, the density correction process can be performed by calculating the entire density characteristic from the middle / high density area process (step S301).

  In this way, the sensor reads the density of the patch pattern by mixing the light toner patch pattern with a gradation level lower than the readable density of the sensor onto the dark toner patch pattern with a specific density. Raised to a possible concentration. Then, the density characteristic of the low density tone level of the light toner is calculated using the measured value of the mixed color patch pattern and the measured value of the patch pattern of the dark toner, so that the density level of the low density tone of the light toner is accurately determined. Density correction is possible.

  As described above, according to the present invention, the density characteristic in the low density region where the sensor reading accuracy is low is increased to a density where the sensor reading accuracy is high, and the measurement is performed accurately. Can be requested. In this way, it is possible to accurately perform density correction from the low density area to the high density area, and always perform printing with stable color.

  Although the embodiment has been described in detail above, the present invention can take an embodiment as a system, apparatus, method, program, storage medium (recording medium), or the like. Specifically, the present invention may be applied to a system composed of a plurality of devices, or may be applied to an apparatus composed of a single device.

  In the present invention, a software program (in the embodiment, a program corresponding to the flowchart shown in the drawing) that realizes the functions of the above-described embodiments is directly or remotely supplied to a system or apparatus. In addition, this includes a case where the system or the computer of the apparatus is also achieved by reading and executing the supplied program code.

  Accordingly, since the functions of the present invention are implemented by computer, the program code installed in the computer also implements the present invention. In other words, the present invention includes a computer program itself for realizing the functional processing of the present invention.

  In that case, as long as it has the function of a program, it may be in the form of object code, a program executed by an interpreter, script data supplied to the OS, or the like.

  Examples of the recording medium for supplying the program include the following. Floppy (registered trademark) disk, hard disk, optical disk, magneto-optical disk, MO, CD-ROM, CD-R, CD-RW, magnetic tape, nonvolatile memory card, ROM, DVD (DVD-ROM, DVD-R) .

  As another program supply method, the program can be supplied by downloading it from a homepage on the Internet to a recording medium such as a hard disk using a browser of a client computer. That is, it connects to a homepage and downloads the computer program itself of the present invention or a compressed file including an automatic installation function from the homepage. It can also be realized by dividing the program code constituting the program of the present invention into a plurality of files and downloading each file from a different homepage. That is, a WWW server that allows a plurality of users to download a program file for realizing the functional processing of the present invention on a computer is also included in the present invention.

  Further, the program of the present invention is encrypted, stored in a storage medium such as a CD-ROM, and distributed to users. Then, the user who has cleared the predetermined condition is allowed to download key information for decryption from the homepage via the Internet. It is also possible to execute the encrypted program by using the key information and install the program on a computer.

  Further, the functions of the above-described embodiments are realized by the computer executing the read program. In addition, the function of the above-described embodiment can be realized by an OS running on the computer based on an instruction of the program and performing part or all of the actual processing.

  Further, the functions of the above-described embodiments are realized even after the program read from the recording medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer. That is, the functions of the above-described embodiments are realized by performing a part or all of the actual processing by the CPU or the like provided in the function expansion board or function expansion unit based on the instructions of the program.

FIG. 3 is a block diagram for explaining a control configuration in a printer 102 according to an embodiment of the present invention. FIG. 2 is a block diagram illustrating a detailed configuration of an image processing unit 106 of the printer 102 illustrated in FIG. 1. 6 is a flowchart for explaining a procedure of density correction processing in a density correction processing unit 107; FIG. 4 is a flowchart for explaining a detailed procedure of middle / high density region processing (step S301) in FIG. 3; FIG. An example of the patch pattern generated by the process of step S401 in FIG. 4 is shown. FIG. 5 is a diagram for explaining a specific example of a device that performs density measurement in the printer 102 for performing the process of step S <b> 402 in FIG. 4. It is a figure which shows an example of the density | concentration characteristic of a medium-high density area. FIG. 4 is a diagram illustrating an example of ideal toner density characteristics. 6 is a diagram illustrating an example of density reading characteristics of a sensor in the printer. FIG. 4 is a flowchart for explaining a detailed procedure of low-density region processing (step S302) in FIG. 3; It is a figure which shows an example of the light toner patch pattern. FIG. 5 is a diagram illustrating an example of a patch pattern having a gradation level in a low density region of dark toner. It is a figure which shows an example of a light / dark mixed color patch pattern. It is a figure which shows an example of the density | concentration measurement result of a light toner patch pattern (A) and a dark and light mixed color patch pattern (C1, C2, C3, C4, C5). FIG. 6 is a diagram illustrating an example of density characteristics of dark toner in a low density region. 4 is a flowchart for explaining a detailed procedure of density correction table creation processing (step S303) in FIG. 3; It is a figure which shows an example of the whole density | concentration characteristic. FIG. 18 is a diagram for explaining a density correction table for correcting a gradation level so that an overall density characteristic indicated by a solid line in FIG. 17 becomes an ideal density characteristic indicated by a broken line.

Explanation of symbols

101 Host Computer 102 Printer 103 Data Processing Unit 104 Interface 105 Reception Buffer 106 Image Processing Unit 107 Density Correction Processing Unit 108 ROM
109 CPU
110 RAM
111 Printer Engine 201 Rendering Unit 202 RGB Data Storage Unit 203 Color Conversion Processing Unit 204 Density Conversion Unit 205 Halftone Processing Unit

Claims (9)

An image processing apparatus that generates patch patterns of multiple gradation levels, measures the density of each patch pattern using a sensor, and calculates density characteristics by interpolating the measured densities,
For a plurality of gradation levels in a density range where it is difficult to measure the density of the patch pattern by the sensor, the density of the patch pattern generated by mixing two types of toner of the same color and different densities, and the two types First calculating means for calculating a difference value between the density of a patch pattern generated using one of the first toners;
Second calculating means for calculating a density characteristic of the density region of the other second toner of the two types of toner based on the difference value;
An image processing apparatus comprising: The first calculating means comprises:
First generation means for generating a first patch pattern having a single gradation level with the first toner;
Second generation means for generating a plurality of second patch patterns of the plurality of gradation levels of the second toner;
Third generation means for generating a plurality of combined patch patterns by combining the plurality of second patch patterns on the first patch pattern, respectively;
Measuring means for measuring the density by drawing the first patch pattern and the plurality of composite patch patterns;
Density calculation means for calculating the difference value obtained by subtracting the density of the first patch pattern from the density of the plurality of composite patch patterns as the density of the plurality of second patch patterns;
The second calculation means calculates the density characteristics of the density range of the second toner by interpolating the density of the plurality of second patch patterns. Image processing apparatus.   The image forming apparatus further includes a creating unit that creates a correction table for correcting an input gradation level of the second toner so that the density characteristic of the density range of the second toner becomes a designated density characteristic. The image processing apparatus according to claim 1 or 2.   The first calculation unit measures the density of the patch pattern drawn on the intermediate transfer body in the printing apparatus by using the sensor. Image processing apparatus.   5. The image processing apparatus according to claim 1, wherein the first toner is a light toner having a density lower than that of the second toner. 6.   The image processing apparatus according to claim 5, wherein the density of the maximum gradation level of the first toner is approximately half of the density of the maximum gradation level of the second toner.   5. The image processing apparatus according to claim 1, wherein the first toner is a dark toner having a density higher than that of the second toner. 6. An image processing method for generating a patch pattern of multiple gradation levels, measuring the density of each patch pattern using a sensor, and calculating a density characteristic by interpolating the measured density,
For a plurality of gradation levels in a density range where it is difficult to measure the density of the patch pattern by the sensor, the density of the patch pattern generated by mixing two types of toner of the same color and different densities, and the two types A first calculation step of calculating a difference value between the density of a patch pattern generated using one of the first toners;
A second calculation step of calculating a density characteristic of the density region of the other second toner of the two types of toner based on the difference value;
An image processing method comprising: A computer that generates patch patterns of multiple gradation levels, measures the density of each patch pattern using a sensor, and calculates density characteristics by interpolating the measured densities.
For a plurality of gradation levels in a density range where it is difficult to measure the density of the patch pattern by the sensor, the density of the patch pattern generated by mixing two types of toner of the same color and different densities, and the two types A first calculation procedure for calculating a difference value between the density of a patch pattern generated using one of the first toners;
A second calculation procedure for calculating a density characteristic of the density region of the other second toner of the two types of toner based on the difference value;
A program for running

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