JP5087527B2 - Calibration apparatus, calibration method, and calibration program - Google Patents

Description

  The present invention relates to a calibration device, a calibration method, and a calibration program for improving or maintaining input / output characteristics in image input / output processing.

In an image forming apparatus such as a printer, image data is formed based on input print data, and is output after the toner density is automatically adjusted.
In such an image forming apparatus, a so-called gamma characteristic (density gradation characteristic) correction process is conventionally performed in order to match a preset design density with a current density actually printed. .

FIG. 27 is a conceptual diagram for explaining a general concept of gamma correction processing.
As shown in FIG. 27C, the desired gamma characteristic is ideal in that the change amount of the input value and the output value is linear, or that the input / output characteristic changes as the designer intends. However, in practice, there are variations among individual devices, and it is difficult to obtain ideal characteristics.
That is, it usually has input / output characteristics as shown in FIG.
Therefore, in general, by incorporating a so-called gamma correction table having characteristics as shown in FIG. 27B, the gamma characteristics unique to the apparatus (FIG. 27A) are made closer to the desired gamma characteristics.

However, the actual gamma characteristic may deviate from the original gamma characteristic, for example, the output value of the toner density adhering to the photosensitive member may decrease due to aging or environmental changes such as temperature and humidity.
Therefore, in the conventional image forming apparatus, it is necessary to correct the gamma correction table periodically or at a timing such as when an output error exceeds a threshold value.
For example, Patent Document 1 discloses a color image processing apparatus that actually measures the density of an output pattern corresponding to several gradations and corrects a gamma correction table in consideration of the density characteristics and output performance. .

Specifically, according to the color image processing apparatus described in Patent Document 1, when the actual maximum density value that can be output by the apparatus exceeds the specified maximum density value, the density is increased to the actual maximum density value. Calibration is performed so that the value increases smoothly and monotonously.
If the actual maximum density value that can be output by the device is less than the specified maximum density value, the range from the input value that has reached the actual maximum density value to the maximum input value is output by the maximum density value. It is controlled so that.
By performing such calibration control, it is possible to maintain a constant gradation while compensating for a decrease in output performance caused by aging.

Japanese Patent No. 3789662

However, in the color image processing apparatus described in Patent Document 1, in the calibration process, the colors of C (Cyan), M (Magenta), Y (Yellow), and K (blacK) are independently determined. Since correction is performed, the balance of the entire hue (hue ring) is lost, and as a result, an unnatural image lacking gradation may be output.
FIG. 28 is a hue circle diagram showing an ideal hue circle and how the hue circle fluctuates.
As shown in FIG. 28A, an ideal color image has C (Cyan), M (Magenta), Y (Yellow), and an intermediate color R (Red) as shown in FIG. ), G (Green), and B (Blue) are regularly arranged, and each plane (hue surface) is balanced.

However, if calibration is performed independently for each hue or for each hue, the balance with other hues may be lost as shown in FIG.
FIG. 5B shows an example in which the positions of Red and Green shift to the Magnanta side and the Cyan side, respectively, by performing calibration without considering the relationship with other colors regarding Yellow. Is.
For this reason, when performing calibration, it is ideal to perform calibration in a well-balanced manner by linking the hues as shown in FIG. 5C, and to realize such calibration. It has been a problem from the past.

  The present invention has been proposed in order to solve the above-described problems of the prior art, and by performing calibration that correlates for each color, it is possible to prevent inconsistencies in color harmony. It is an object of the present invention to provide a calibration device, a calibration method, and a calibration program that suitably adjust or maintain output characteristics.

  In order to achieve the above object, a calibration apparatus according to the present invention is used to match or approximate an input / output characteristic indicating a relationship between a density setting value and an output density value in image processing to a preset ideal input / output characteristic. A calibration device for acquiring an input / output characteristic of a predetermined color related to an output image for each color; and selecting an input / output characteristic related to one color from the input / output characteristics based on a predetermined condition In addition, a reference characteristic setting unit that sets a correlated reference characteristic for each color based on the input / output characteristics, a correction table generating unit that generates a correction table corresponding to the reference characteristic for each color, and the correction table By correcting the output density value on the basis, the input / output characteristics for each color relating to the output image are set for the color. A configuration equipped with a calibration means for calibrating the level characteristic.

  The calibration method of the present invention is a calibration method for matching or approximating the input / output characteristic indicating the relationship between the density setting value and the output density value in image processing to a preset ideal input / output characteristic. A characteristic acquisition step for acquiring an input / output characteristic of a predetermined color for the output image for each color, and selecting an input / output characteristic for one color from the input / output characteristics based on a predetermined condition; A reference characteristic setting step for setting a correlation characteristic for each color based on the characteristic, a correction table generation step for generating a correction table corresponding to the reference characteristic for each color, and the output density value based on the correction table By correcting the input / output characteristics for each color related to the output image, the reference characteristics set for the color are corrected. There as a method having a calibration step to calibrate the.

  The calibration program of the present invention is a calibration program for matching or approximating an input / output characteristic indicating a relationship between a density setting value and an output density value in image processing to a preset ideal input / output characteristic. A predetermined computer, characteristic acquisition means for acquiring an input / output characteristic of a predetermined color for an output image for each color, and selecting an input / output characteristic for one color from the input / output characteristics based on a predetermined condition; Reference characteristic setting means for setting a correlated reference characteristic for each color based on the input / output characteristics, a correction table generating means for generating a correction table corresponding to the reference characteristic for each color, and the output density based on the correction table By correcting the value, the input / output characteristics for each color relating to the output image are set for that color. Was there a program for causing the calibrating means functions as, for calibrating said reference characteristic.

  According to the calibration device, the calibration method, and the calibration program of the present invention, it is possible to realize excellent input / output characteristics with excellent harmony of the entire color.

First, a basic concept of calibration processing common to each embodiment described later will be described with reference to FIGS. 1 and 2.
FIG. 1 is an input / output characteristic diagram showing input / output characteristics in a general image forming apparatus, and FIG. 2 is a correction table showing general characteristics of a gamma correction table provided in advance in the image forming apparatus. FIG.
In FIG. 1, a solid line indicates an actual input / output characteristic including a measured density value, and a broken line indicates an input / output characteristic including an ideal design density value set in advance.

Here, in general, an image forming apparatus is provided with a gamma correction table (hereinafter referred to as a correction table) having predetermined characteristics as shown in FIG. A desired input / output characteristic can be realized corresponding to the characteristic.
However, it is not realistic to use such a correction table as it is.
This is because the input / output characteristics change as shown by the solid line in FIG. 1 in accordance with changes in output performance due to aging or the like.
In other words, as shown in the figure, a considerable error occurs between the current input / output characteristics (solid line) and the ideal design density value (broken line). As a result, the gradation and reproduction of the output image It will worsen the sex.

For this reason, in the calibration apparatus according to the present invention, in order to reduce the error between the actual input / output characteristics and the ideal input / output characteristics shown in FIG. A reference correction table corresponding to is set.
A desired calibration is realized by outputting via the reference correction table.
In particular, in the present invention, a reference characteristic correlated for each color is set, and a corresponding correction table is generated for each color, thereby realizing harmonized calibration for the entire color. I have to.
Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIGS.

[First embodiment]
FIG. 3 is a block diagram showing the configuration of the image forming apparatus 100 according to the first embodiment of the present invention.
As shown in the figure, an image forming apparatus 100 according to the present embodiment is connected to a host computer 200 such as a personal computer, and forms an image based on input image data received from the host computer 200 and performs a printing process. Is what you do.
Specifically, the image forming apparatus 100 according to the present embodiment includes a print data acquisition unit 10, an image processing unit 20, a storage unit 30, an engine control unit 40, and an engine unit 50. Input / output processing is executed smoothly.

The print data acquisition unit 10 constitutes a so-called communication interface that receives print data from the host computer 200.
The input image data received by the print data acquisition unit 10 is output to the image processing unit 20.
The image processing unit 20 performs predetermined image processing on the input image data from the print data acquisition unit 10 and converts the input image data into a drawing data format that can be processed by the engine unit 50.
However, the image processing unit 20 according to the present embodiment performs the following various processes related to calibration of input / output characteristics in addition to such general image processing.

Next, details of the image processing unit 20 will be described with reference to the drawings.
FIG. 4 is a functional block diagram showing the configuration of the image processing unit 20 according to the present embodiment.
As shown in the figure, the image processing unit 20 according to the present embodiment includes a characteristic acquisition unit 21, a reference characteristic setting unit 22, a correction table generation unit 23, and a calibration unit 24.
Each means is centrally controlled by a CPU (Central Processing Unit) (not shown), and the CPU operates according to a predetermined program stored in advance in a ROM (Read Only Memory) (not shown). A desired calibration process is performed.

The characteristic acquisition means 21 acquires the current input / output characteristics for each color in C (Cyan), M (Magenta), Y (Yellow), and K (blacK). This measures the input / output characteristics.
Specifically, under the control of the characteristic acquisition unit 21, the developing unit 51 develops a sample patch image that can accurately reproduce C, M, Y, and K on the transfer unit 52, and the toner sensor 53. However, by measuring the density value of the image for each color, the current input / output characteristics are obtained for each of C, M, Y, and K.

The reference characteristic setting means 22 sets a reference characteristic correlated for each color by analyzing each input / output characteristic of CMYK.
In this embodiment, in order to perform so-called absolute value calibration that places emphasis on the reproducibility of the output density value, a reference characteristic that matches the ideal input / output characteristic is set for a certain interval. Yes.
Specifically, after extracting the maximum output density value that can be output by analyzing each current input / output characteristic of CMYK for each CMYK, the original density setting value corresponding to each maximum output density value is set for each color. After selecting the lowest density setting value from the calculated density setting values, the minimum density setting value that can be set by the image forming apparatus 100 to the one density setting value is selected. For the section, the reference characteristic is set in common for each CMYK so that the corresponding output density value matches the output density value of the ideal input / output characteristic.

Hereinafter, a detailed description will be given of the reference characteristic setting method according to the present embodiment.
First, as a pre-process, a predetermined normalization process is performed so that an error between the current input / output characteristic and the ideal input / output characteristic can be simply compared numerically (absolute value correction process).
Specifically, this absolute correction process equalizes the measured density value and the desired density value (design density value) corresponding to the measured density value to a certain range based on the range of the desired density value.
For example, in the image forming apparatus 100 of the present embodiment that performs processing of a maximum of 256 gradations by 8-bit processing, values DRi ″ and DCi ″ after normalization with respect to an arbitrary desired density value DRi and an arbitrary measured density value DCi. Can be obtained based on the following equations (1) and (2).
DRi ″ = ((DRi−DRmin) / (DRmax−DRmin)) × 255 (1)
DCi ″ = ((DCi−DRmin) / (DRmax−DRmin)) × 255 (2)
(However, the gradation values i = 0, 1, 2,..., 254, 255)

As a result, for example, each input / output characteristic shown in FIG. 1 can be expressed as a solid line and a broken line in FIG.
FIG. 5 is an input / output characteristic diagram showing the input / output characteristics and the reference characteristics after the input / output characteristics shown in FIG.
From this figure, it can be read that as the current output performance of this image forming apparatus, high density of output density values 0 to 35 cannot be reproduced, but output density values 35 to 255 can be reproduced.

Further, the image forming apparatus 100 according to the present embodiment performs this absolute value correction process for each of C, M, Y, and K.
FIG. 6 is an input / output characteristic diagram showing the input / output characteristics after performing an absolute value correction process for each CMYK in the present embodiment.
As shown in the figure, according to the image forming apparatus 100 according to the present embodiment, the output density value of 0 to 13 cannot be reproduced for Cyan, and the output density value of 0 to 28 cannot be reproduced for Magenta. It can be read that the output density value of 0 to 35 cannot be reproduced for Yellow, and the output density value of 0 to 29 cannot be reproduced for Black.

After performing the absolute value correction process for each color in this way, the reference characteristic setting means 22 sets specific reference characteristics.
For example, FIG. 7 is an input / output characteristic diagram showing how the yellow input / output characteristic fluctuates in this embodiment.
In the figure, the broken line indicates the input / output characteristics composed of the designed density values, and the solid line indicates the current input / output characteristics composed of the measured density values.
As shown in the figure, as the output performance of Yellow, output density values from 35 to 255 can be output, and therefore, for this color, the corresponding output ink amount of 0 to 184 matches the output density value with the design density value. Set the reference characteristics.

However, as described above, since the maximum output density value (S) for each color is different (see FIG. 6), in this embodiment, calibration is not performed independently for each CMYK as in the prior art. In order to perform calibration in consideration of the hue balance, reference characteristics related to CMYK are set.
Basically, the reference characteristic setting means 22 of the present embodiment selects the minimum value from among the maximum density setting values T corresponding to each maximum output density value S as the reference setting value t, and this reference setting A reference characteristic for each color is set based on the value t.
In this embodiment, the maximum density setting value T of Cyan is 225, the maximum density setting value T of Magenta is 210, the maximum density setting value T of Yellow is 184, and the maximum density setting value T of Black is 205. For this reason, the maximum density setting value T of Yellow becomes the reference setting value t (see FIG. 6).

Then, the reference characteristic setting means 22 sets a predetermined reference characteristic for each CMYK based on this reference set value t (= 184).
Specifically, for each of C, M, Y, and K, a reference characteristic that matches the ideal output density value is set for the interval of density setting values 0 to 184.
As a result, the reference characteristics of C, M, Y, and K are as shown in FIG.
FIG. 8 is an input / output characteristic diagram showing the reference characteristics of C, M, Y, and K in the present embodiment.
As shown in the figure, since the setting value at which the density value is saturated differs depending on the color in the section of the density setting values 184 to 255, the output density value is constant for each color. The reference characteristics are set so that the design density value corresponding to 184 is obtained.

The correction table generating unit 23 generates a correction table corresponding to the set reference characteristic for each color.
Specifically, a correction table having characteristics corresponding to the reference characteristics for each of C, M, Y, and K set by the reference characteristic setting means 22 is generated. For example, the correction table is set for Yellow. In order to obtain the reference characteristic (two-dot chain line in FIG. 5), a characteristic correction table shown in FIG. 9 is generated.
Further, the correction table generation means 23 of this embodiment generates a correction table for each of C, M, Y, and K by the same process.
When generating the correction table, the original correction table may be corrected and updated, or a new separate correction table may be generated.

The calibration means 24 calibrates the input / output characteristics of each color to the reference characteristics set for each color by correcting the output value based on the correction table, and embodies so-called calibration processing.
Specifically, as shown in FIG. 10, RGB input data is color-converted into CMYK data by a LUT (Look Up Table), and calibration is realized by correcting the CMYK data via the correction table described above. Is. Note that the gradation reproduction of the corrected CMYK data is stabilized by a predetermined screen process.

As a result, the input / output characteristics of the image forming apparatus 100 according to the present embodiment are as shown in FIG. 11 (two-dot chain line), and an ideal output is obtained for a predetermined section (a section of the output ink amount 0 to 184). A density value (design density value) is obtained, and input / output characteristics with excellent reproducibility can be obtained.
Further, since the calibration means 24 performs such calibration processing for each color of C, M, Y, and K, the color of the entire image is harmonized and an image output with excellent gradation can be achieved (FIG. 28). (See (c)).

As illustrated in FIG. 3, the storage unit 30 stores predetermined data in cooperation with the image processing unit 20.
For example, it is composed of a RAM (Random Access Memory), a hard disk, etc., and functions as a work area for various programs executed by the CPU and other data storage areas.
Regarding the present embodiment, when the characteristic acquisition unit 21 is executed, density value data of a patch image measured by the toner sensor 53, a desired design density value, and the like are temporarily or permanently stored.

  The engine control unit 40 outputs the drawing data image-processed by the image processing unit 20 to the engine unit 50 and issues an instruction to execute the printing process.

When the engine unit 50 receives drawing data from the engine control unit 40, the engine unit 50 executes a printing process based on the data, and further includes a developing unit 51, a transfer unit 52, and a toner sensor 53.
The developing unit 51 visualizes drawing data to be printed. In the present embodiment, the developing unit 51 executes a developing process for a plurality of color patch image data to be measured in advance.
The transfer unit 52 includes a transfer belt and a transfer drum that are rotationally driven by drive control by the engine control unit 40, and carries a toner image of a color patch image visualized by the developing unit 51.
The toner sensor 53 is provided so as to face the vicinity of the transfer portion 52 and reads a toner image formed on the transfer belt or the transfer drum.
The toner sensor 53 is not limited to an image carried on a transfer belt or the like, and may read a patch image printed on a printing medium such as paper.
As described above, the image data read by the toner sensor 53 is sent to the image processing unit 20 via the engine control unit 40, and the input / output characteristics relating to the density are acquired by the characteristic acquisition unit 21.

Next, a calibration method using the image forming apparatus according to the first embodiment of the present invention will be described with reference to FIG.
FIG. 12 is a flowchart showing the procedure of the calibration method according to the present embodiment.
As a premise, ideal input / output characteristics for each of C, M, Y, and K, that is, design density values (output values) and corresponding density setting values (input values) are stored in a memory such as a RAM (A0). .

First, in the image forming apparatus 100 according to the present embodiment, the developing unit 51 draws a sample patch image on paper, a transfer belt, or the like (A1).
Next, the toner sensor 53 measures the density of the patch image transferred to the transfer belt or the like, and the characteristic acquisition unit 21 acquires the current input / output characteristics for each of C, M, Y, and K (A2).
Thereby, typically, the input / output characteristics as shown in FIG. 1 can be acquired.

Here, the reference characteristic setting means 22 performs a predetermined normalization process (absolute value correction process) on the acquired input / output characteristic (A3).
Specifically, the output density value is equalized based on the above formulas (1) and (2).
As a result, the input / output characteristics for CMYK are represented as shown in FIG.
Next, the reference characteristic setting unit 22 extracts the current maximum output density value S for each CMYK by analyzing the normalized input / output characteristics (step A4).
Thereafter, the reference characteristic setting unit 22 calculates an original density setting value (maximum density setting value T) corresponding to the maximum output density value S for each color (step A5).
Subsequently, the reference characteristic setting means 22 selects the minimum value (minimum reference value t) from the maximum density setting values T calculated for each color (step A6).
Then, the reference characteristic setting unit 22 sets the reference characteristic for each color so that the section (IN0 to 184) up to the minimum reference value t has an ideal output density value (step A7).
As a result, as shown in FIG. 8, the reference characteristics with respect to t = 184 are set for C, M, Y, and K, respectively.

Here, the correction table generating means 23 generates a correction table corresponding to the reference characteristic for each color of C, M, Y, and K (step A8).
For example, in order to correspond to the reference characteristic (two-dot chain line) in FIG. 5, a correction table having characteristics as shown in FIG. 9 is generated and developed for each color.
Then, the proofreading unit 24 performs a printing process using the correction table generated in step A8 (step A9).
Thereby, the current input / output characteristics shown by the solid line in FIG. 1 are improved like the input / output characteristics shown by the two-dot chain line in FIG. 11, and the calibration (absolute value calibration) processing according to the present embodiment is performed by CMYK. It is executed every time.

As described above, according to the image forming apparatus 100 of the present embodiment, the characteristic acquisition unit 21 acquires the input / output characteristics of the output image for each CMYK, thereby recognizing the current input / output characteristics. Has an effect.
The reference characteristic setting unit 22 sets a target reference characteristic according to the form and fluctuation of the input / output characteristic.
In particular, in this embodiment, the reference characteristics are set for each color so that the input / output characteristics of CMYK are correlated.
Further, a reference characteristic having a shape that matches the design density value is set in the predetermined section.
Then, after the correction table generation unit 23 generates a correction table for each CMYK so as to correspond to the reference characteristics, the calibration unit 24 outputs an image via the correction table so that desired calibration is performed. Yes.

In other words, the image forming apparatus 100 according to the present embodiment can output a natural color expression image with high gradation by harmonizing CMYK.
Further, by performing absolute value calibration for each CMYK, it is possible to perform density correction with excellent reproducibility.
Further, such a calibration process can be realized only by setting or adding or changing a program without significantly modifying the hardware.

Therefore, according to the image forming apparatus 100 of the present embodiment, it is possible to easily realize a calibration apparatus that is excellent in color harmony, reproducibility, and gradation with respect to output density.
In addition, since a high-quality image can be output over a long period of time, the image forming apparatus 100 having excellent reliability and convenience can be provided.

[Second Embodiment]
Next, an image forming apparatus according to a second embodiment of the present invention will be described with reference to the drawings.
The image forming apparatus 100 according to the present embodiment has basically the same configuration as that of the first embodiment described above.
For this reason, the image forming apparatus according to the second embodiment has the same configuration as that shown in FIGS. 1 and 2.
However, the first embodiment performs absolute value calibration, but the present embodiment is different in that relative value calibration is performed.

That is, in the present embodiment, since calibration is performed with emphasis on gradation, the reference characteristic setting method differs accordingly.
Basically, the reference characteristic setting unit 22 according to the present embodiment is a reference for one color that minimizes an error from an ideal input / output characteristic among the CMYK input / output characteristics acquired by the characteristic acquisition unit 21. The characteristics are set, and the reference characteristics of other colors are set so as to be correlated with the reference characteristics.

Hereinafter, the reference characteristic setting method according to the present embodiment will be described.
First, predetermined normalization processing is performed as preprocessing. However, unlike the first embodiment, the preprocessing in this embodiment equalizes the measured density value (measured output value) to a certain range based on the range that the measured density value can take, and the corresponding desired density value. The (design density value) is equalized to a certain range based on the range of the desired density value (relative value correction process).
For example, an arbitrary desired density value is DRi, a minimum desired density value at output 0 is DRmin, a maximum desired density value at output 255 is DRmax, an arbitrary measured density value is DCi, and a minimum measured density value at output 0 is When the maximum measured concentration value at DCmin and output 255 is DCmax, values DRi ′ and DCi ′ after normalization with respect to DRi and DCi can be obtained based on the following equations (3) and (4).
DRi ′ = ((DRi−DRmin) / (DRmax−DRmin)) × 255 (3)
DCi ′ = ((DCi−DCmin) / (DCmax−DCmin)) × 255 (4)
(However, the gradation values i = 0, 1, 2,..., 254, 255)

As a result, for example, each input / output characteristic shown in FIG. 1 can be expressed as a solid line and a broken line in FIG.
FIG. 13 is an input / output characteristic diagram showing the input / output characteristics and the reference characteristics after the input / output characteristics shown in FIG.
From the figure, the starting point and the ending point of both input / output characteristics are unified, but the inclination, that is, the difference in curvature can be clearly recognized.

Furthermore, the image forming apparatus 100 according to the present embodiment performs this relative value correction process for each of C, M, Y, and K.
FIG. 14 is an input / output characteristic diagram showing the input / output characteristics after performing relative value correction processing for each CMYK in this embodiment.
As shown in the figure, in the present embodiment, for each of Cyan, Magenta, Yellow, and Black, the area indicated by hatching can be obtained as an index of the input / output characteristic error.
Then, after setting the reference characteristics for the color that minimizes the area (error), the reference characteristics are set for the other colors in correlation with the reference characteristics.

In this embodiment, since the area of the yellow is the smallest, first, the reference characteristic of the yellow is set.
The reference characteristic of the yellow is set so as to increase (decrease) smoothly and monotonously while referring to the ideal input / output characteristic (see Yellow in FIG. 15 or FIG. 16).
For example, an attempt is made to set a curvature monotone curve based on the curvature of ideal input / output characteristics.
Further, a reference characteristic capable of realizing the best gradation may be automatically set while actually measuring continuity and regularity from the relationship between the output density value and the density setting value.

Next, a process for setting the reference characteristics of other colors based on the initially set reference characteristics of Yellow will be described.
Here, in order to simplify the explanation and facilitate understanding, a process for setting Cyan's reference characteristics will be described as an example with reference to FIG. For convenience, the set density value (X coordinate) is called IN, and the output density value (Y coordinate) is called OUT.
FIG. 15 is an input / output characteristic diagram for explaining a reference characteristic setting process according to the present embodiment.
First, in FIG. 15B, an arbitrary point on the Yellow design is extracted. Here, it is assumed that the point A (30, 205) is extracted as a sample.
Subsequently, a point B (35, 205) on the reference characteristic corresponding to the point A is obtained.

Moving to FIG. 15A, the corresponding reference characteristic is set.
Here, attention is paid to IN (30) and IN (35) obtained in advance by Yellow.
Specifically, a design point A ′ (30,200) corresponding to Cyan's IN (30) is first obtained, and then a corresponding point B ′ (35,200) is obtained.
That is, Cyan's reference characteristic can be obtained by obtaining a considerable number of points typified by this point B ′ (35, 200) on FIG.
For example, this figure shows a state in which the above association is performed for each of IN 60, 90, 120, 150, 180, 210, and 240 (see FIG. 15 (a) × part).
Then, by performing such processing for Magenta and Black, it is possible to set a reference characteristic that correlates for each of C, M, Y, and K.

As a result, the reference characteristics of C, M, Y, and K are as shown in FIG.
FIG. 16 is an input / output characteristic diagram showing the C, M, Y, and K reference characteristics set by the reference characteristic setting means 22 of the present embodiment.
As shown in the figure, for each of C, M, Y, and K, the reference characteristics are set through the above-described process, thereby maintaining the gradation in each color and maintaining the harmonized reference for the entire color. The characteristic is set.

Note that the correction table generation unit 23 generates a correction table corresponding to the above-described reference characteristic, as in the first embodiment. For example, a correction table having characteristics as shown in FIG. 17 (dashed line) is generated as a correction table corresponding to the reference characteristic (dashed line) indicated by Yellow in FIG.
Further, the correction table generation means 23 of this embodiment generates a correction table for each of C, M, Y, and K by the same process.

Similar to the first embodiment, the calibration unit 24 calibrates the input / output characteristics of each color to the reference characteristics by correcting the output value via the correction table.
As a result, the input / output characteristics of the image forming apparatus 100 according to the present embodiment are as shown in FIG. 18 (one-dot chain line), and input / output characteristics with excellent gradation can be obtained.
Further, since the calibration unit 24 performs such calibration processing for each color of C, M, Y, and K, the hue of the entire image can be harmonized and a more natural gradient can be expressed (see FIG. 28 (c)).

  In addition, about the memory | storage part 30, the engine control part 40, and the engine part 50, since it is the structure substantially the same as 1st embodiment and acts similarly, detailed description is omitted.

Next, a calibration method using the image forming apparatus according to the second embodiment of the present invention will be described with reference to FIG.
FIG. 19 is a flowchart showing the procedure of the calibration method according to the present embodiment.
As a premise, ideal input / output characteristics for each of C, M, Y, and K, that is, an output density value as a design value and a corresponding density setting value are stored in a memory such as a RAM (B0).

First, in the image forming apparatus 100 according to the present embodiment, the developing unit 51 draws a sample patch image showing actual input / output characteristics on paper or a transfer belt (B1).
Next, the toner sensor 53 measures the density of the patch image transferred to the transfer belt or the like, and the characteristic acquisition unit 21 acquires the current input / output characteristics for each of C, M, Y, and K (B2).
Thereby, typically, the input / output characteristics as shown in FIG. 1 can be acquired.

Here, the reference characteristic setting means 22 performs normalization processing (relative value correction processing) on the acquired input / output characteristics (B3).
Specifically, the output density values are equalized based on the above equations (3) and (4).
Next, the reference characteristic setting unit 22 analyzes the normalized input / output characteristic to measure an error in the input / output characteristic for each CMYK (step B4).
Thereafter, the reference characteristic setting unit 22 specifies the color where the measurement error is minimized (step B5). In this embodiment, Yellow is specified by this step.

Then, the reference characteristic setting unit 22 sets the reference characteristic related to the color specified in step B5 (step B6).
Here, as described above, with respect to Yellow, a reference characteristic is set that smoothly increases (decreases) monotonously based on the curvature of the ideal characteristic (see FIG. 15B).
Subsequently, the reference characteristic setting unit 22 sets the reference characteristic for other colors (C, M, K) based on the reference characteristic set in step B6 (step B7).
Specifically, as described above, the reference characteristic is set by associating the correlation between the ideal input / output characteristic in Yellow and the reference characteristic with other colors (see FIG. 15A).

Here, the correction table generation means 23 generates a correction table corresponding to the reference characteristic for each color of C, M, Y, and K (step B8).
For example, in order to correspond to the reference characteristic (two-dot chain line) in FIG. 13, a correction table having characteristics as shown in FIG. 17 is generated and developed for each color.
Then, the calibration unit 24 executes a printing process using the reference correction table generated in step B8 (step B9).
As a result, the current input / output characteristics shown in FIG. 1 are improved like the input / output characteristics shown by the one-dot chain line in FIG. 18, and the calibration processing (relative value calibration) according to the present embodiment is executed. It becomes.

As described above, according to the image forming apparatus 100 of the present embodiment, since the configuration is the same as that of the first embodiment, basically the same operations and effects can be achieved.
However, in the image forming apparatus 100 according to the present embodiment, the reference characteristic setting unit 22 sets the reference characteristics that emphasize continuity for each CMYK.
That is, the image forming apparatus 100 according to the present embodiment realizes input / output characteristics that emphasize gradation.
For this reason, it is possible to realize and maintain an image output with further excellent gradation while harmonizing the whole color.

[Third embodiment]
Next, an image forming apparatus according to a third embodiment of the present invention will be described with reference to the drawings.
The image forming apparatus 100 according to the present embodiment has basically the same configuration as the first embodiment and the second embodiment described above.
For this reason, the image forming apparatus according to the third embodiment has the same configuration as that shown in FIGS. 1 and 2.
However, the image forming apparatus according to the first embodiment performs absolute value calibration, and the image forming apparatus according to the second embodiment performs relative value calibration. This is different in that hybrid calibration is performed by combining these.
First, the basic concept of hybrid calibration performed in this embodiment will be described below.

FIG. 20 illustrates the input / output characteristics of a general image forming apparatus relating to the present embodiment, and FIG. 21 illustrates the input / output characteristics after performing the hybrid calibration.
In these figures, the broken line is the ideal input / output characteristic, the solid line is the current input / output characteristic, the alternate long and short dash line is the relative input / output characteristic, and the two-dot difference line is the current input / output characteristic. Each of the input / output characteristics is subjected to absolute value calibration.
As shown in these drawings, the image forming apparatus 100 according to the present embodiment attempts to realize the characteristics indicated by the dotted line in FIG. 21 by combining or fusing the absolute value calibration and the relative value calibration described above. To do.
In other words, the present embodiment aims to realize both reproducibility and gradation that are the merits of both.

For this reason, the reference characteristic setting method in this embodiment is different from that in the above-described embodiment.
Basically, the reference characteristic setting unit 22 according to the present embodiment inputs an output density value in an ideal input range for a section from the minimum density setting value that can be set by the image forming apparatus 100 to an arbitrary density setting value t ′. A characteristic that is matched with the output characteristic and approximated to an ideal input / output characteristic while maintaining gradation in an interval from an arbitrary density setting value t ′ to the maximum density setting value that can be set by the image forming apparatus 100 Is set as a reference characteristic in units of colors.

Hereinafter, the reference characteristic setting method according to the present embodiment will be described in detail.
First, the reference characteristic setting unit 22 preliminarily classifies an area where absolute value calibration is performed and an area where relative value calibration is performed.
Specifically, as in the first embodiment described above, the maximum density setting value T is obtained from each of the CMYK input / output characteristics, and the minimum (reference setting value t) is extracted from the maximum density setting value T (see FIG. 6).
Thereby, the reference set value t in Yellow is extracted, and this is used as a boundary reference between absolute value calibration and relative value calibration.
For example, the boundary reference is a value t ′ obtained by subtracting a predetermined value from the reference set value t. In the example of the present embodiment, the boundary reference is obtained by subtracting 34 from the reference set value t (= 184) (t ′ = 150).

Reference characteristics for performing absolute value calibration are set for IN0 to 150, and relative value calibration is set for IN150 to 255.
For this reason, the reference characteristic setting means 22 sets the reference characteristic that matches the ideal value for each color from IN0 to 150 as in the first embodiment.
On the other hand, for IN150 to 255, first, the reference characteristic for Yellow is set, and then the reference characteristic is set for other colors based on the same process as in the second embodiment.
That is, the reference characteristics are set for C, M, and K based on the reference characteristics set for Yellow.
The method for setting the reference characteristics is the same as that in the second embodiment described above, and a detailed description thereof is omitted.

As a result, the reference characteristics of C, M, Y, and K are as shown in FIG.
FIG. 22 is an input / output characteristic diagram showing the reference characteristics set by the reference characteristic setting means 22 in this embodiment for each CMYK.
As shown in the figure, in each of C, M, Y, and K, a reference characteristic that matches an ideal output density value is set in a section of density setting values 0 to 150, and density setting values 150 to 255 are also set. In the section, a reference characteristic that smoothly and monotonously increases is set.

The correction table generation unit 23 generates a correction table corresponding to the reference characteristic for each color.
Specifically, a correction table having characteristics corresponding to the C, M, Y, and K reference characteristics set by the reference characteristic setting means 22 is generated. Typically, a correction table having characteristics as shown in FIG. 23 (dotted line) is generated.

The calibration means 24 calibrates the input / output characteristics of each color to the reference characteristics set for each color by correcting the output value based on the correction table.
As a result, the input / output characteristics of the image forming apparatus 100 according to the present embodiment are not only excellent in color harmony as in the above-described embodiments, but also excellent in reproducibility for a predetermined section. For the predetermined section, image output with excellent gradation is realized, and the advantages of the first embodiment and the second embodiment can be enjoyed together.

  In addition, about the memory | storage part 30, the engine control part 40, and the engine part 50, since it is the structure substantially the same as 1st embodiment and acts similarly, detailed description is omitted.

Next, a calibration method using the image forming apparatus according to the third embodiment of the present invention will be described with reference to FIG.
FIG. 24 is a flowchart showing the procedure of the calibration method according to the present embodiment.
As a premise, ideal input / output characteristics for each of C, M, Y, and K, that is, an output density value as a design value and a corresponding density setting value are stored in a memory such as a RAM (C0).

Accordingly, first, in the image forming apparatus 100 according to the present embodiment, the developing unit 51 draws a sample patch image on paper, a transfer belt, or the like (C1).
Next, the toner sensor 53 measures the density of the patch image transferred to the transfer belt or the like, and the characteristic acquisition unit 21 acquires the current input / output characteristics for each of C, M, Y, and K (C2).
Thereby, typically, the input / output characteristics as shown in FIG. 1 can be acquired.

Here, the reference characteristic setting means 22 performs normalization processing (absolute value correction processing) on the acquired input / output characteristics (C3).
Specifically, the output density values are equalized based on the above formulas (1) and (2).
As a result, the input / output characteristics for CMYK are represented as shown in FIG.
Next, the reference characteristic setting unit 22 extracts the current maximum output density value S for each CMYK by analyzing the normalized input / output characteristics (step C4).
Thereafter, the reference characteristic setting unit 22 calculates an original density setting value (maximum density setting value T) corresponding to the maximum output density value S for each color (step C5).

Subsequently, the reference characteristic setting means 22 selects the minimum value (minimum reference value t) from the maximum density setting values T calculated for each color (step C6).
In this embodiment, the yellow maximum density setting value T (= 184) is selected in step C6.
Then, the reference characteristic setting unit 22 first sets the reference characteristic so as to obtain an ideal output density value up to an arbitrary density setting value t ′ less than or equal to the minimum reference value t with respect to Yellow (step C7). In the section between the arbitrary density setting value t ′ and the maximum density setting value, the reference characteristic is set so that the corresponding output density value is drawn in a gentle arch shape up to the maximum output density value S so that the gradation can be maintained ( Step C8).

Step C8 is also performed for each of the other colors (CMK).
In the present embodiment, the value obtained by subtracting 34 from t is set to the above-described arbitrary density setting value t ′, and therefore, the section of the density setting value 0 to 150 matches the desired design density value as shown in FIG. The reference characteristics having excellent gradation characteristics are set for each of C, M, Y, and K in the interval of the density setting values 150 to 255.

Here, the correction table generating means 23 sets a correction table corresponding to the reference characteristic for each color of C, M, Y, and K (step C9).
For example, in order to correspond to the yellow reference characteristic (dotted line) in FIG. 22, a correction table having characteristics as shown in FIG. 23 is generated and developed for each color.
Then, the calibration unit 24 executes the printing process using the correction table generated in step C9 (step C10).

As described above, according to the image forming apparatus 100 of the present embodiment, since it has the same configuration as that of the first embodiment and the second embodiment, the same operations and effects as the above-described embodiments are basically provided. .
However, in the image forming apparatus 100 according to the present embodiment, the reference characteristic setting unit 22 sets the reference characteristics that emphasize both reproducibility and continuity for each CMYK.
In other words, the image forming apparatus 100 according to the present embodiment is configured to match the design density value for a predetermined section, and to realize input / output characteristics with emphasis on gradation in other predetermined sections.
For this reason, it is possible to realize and maintain an image output with further excellent reproducibility and gradation while harmonizing the whole color.
Therefore, it is possible to improve image quality while maximizing the current output performance of the image forming apparatus 100.

[Fourth embodiment]
Next, an image forming apparatus according to a fourth embodiment of the present invention will be described with reference to the drawings.
The image forming apparatus 100 according to the present embodiment has basically the same configuration as that of the first to third embodiments described above, but the configuration of the image processing unit 20a is different.
FIG. 25 is a functional block diagram showing the configuration of the image processing unit 20a of the image forming apparatus 100 according to the fourth embodiment of the present invention.
As shown in the figure, the image processing unit 20a according to the present embodiment includes a single color designation unit 25a, a color mixture designation unit 26a, and a hue determination unit 27a.
That is, according to the image forming apparatus 100 of the present embodiment, it is possible to arbitrarily select whether to perform single color processing or color mixing processing by a predetermined operation of the user.

The monochromatic designating means 25a designates an arbitrary monochromatic color to be monochromatic output in accordance with a predetermined operation.
The reference characteristic setting unit 22a sets the reference characteristic based on the monochrome input / output characteristic regarding the output image acquired by the characteristic acquisition unit 21a.
For example, when a black and white output image is desired, it is not necessary to generate black color by mixing colors, and it is possible to reproduce the image with pure black color.
Of course, not only black and white but also primary colors such as Red, Green, Blue, Cyan, Magenta, and Yellow can be specified and output in a single color.

Further, the color mixture designation unit 26a designates an arbitrary color to be output by two color mixture or three color mixture according to a predetermined operation.
The hue determination unit 27a determines a hue region to which the color designated by the color mixture designation unit 26a belongs, and determines two colors or three colors constituting the hue region.
Then, the characteristic acquisition unit 21a acquires two-color or three-color input / output characteristics for the output image for each color, and the reference characteristic setting unit 22a sets the reference characteristic based on the input / output characteristics. .
For example, when a user desires an output by two-color mixing with respect to a Green color which is an intermediate color between Yellow and Cyan, the reference characteristic is set by analyzing the input / output characteristics of Yellow and Cyan.

As the reference characteristic, any one of the setting processes in the first to third embodiments described above is used for either single color or mixed color.
That is, a reference characteristic is set to execute any one of absolute value calibration, relative value calibration, and hybrid calibration, and a correction table corresponding to this is generated. Then, through this correction table, each calibration is performed at the time of monochromatic output or mixed color output.

Next, a calibration method using the image forming apparatus according to the fourth embodiment of the present invention will be described with reference to FIG.
FIG. 26 is a flowchart showing the procedure of the calibration method according to the present embodiment.
In order to simplify the description and make it easy to understand, in the present embodiment, the following description will be made assuming that absolute value calibration is performed.
First, the image forming apparatus 100 according to the present embodiment determines whether or not single color output is designated (step D1).
Specifically, it is confirmed whether or not the user has set a mode for specifying monochromatic output.

If it is determined in step D1 that a single color output has been designated (step D1: Yes), the reference characteristic setting means 21a analyzes only the input / output characteristics relating to the single color of the designated color and sets a predetermined reference characteristic ( Step D2).
In the case of this embodiment, an absolute value calibration is performed by setting a reference characteristic corresponding to the maximum output density value S.
For example, when the user designates Black monochromatic output, only the Black input / output characteristics (absolute value correction processing) are referred to, and the reference characteristic setting means 22a is based on the maximum output density value S = 29. Set the reference characteristics. That is, the reference characteristic setting unit 22a sets the reference characteristic so that the corresponding set density values 0 to 205 coincide with the desired ideal characteristic (see FIG. 6).

Then, the correction table generation unit 23a generates a correction table corresponding to the reference characteristic set in step D2, and print processing is executed via the calibration unit 24a (step D3).
As a result, absolute value calibration related to a single color is performed.

On the other hand, if it is determined in step D1 that the single color output designation is not set (step D1: NO), the image forming apparatus 100 next determines whether or not there is an output designation based on two-color mixing ( Step D4).
Specifically, it is determined whether or not the two-color mixed output mode is set by a predetermined operation by the user.
In step D4, when it is determined that the two-color mixed color output is specified (step D4: YES), the hue determination unit 27a determines the hue region to which the color specified by the user belongs (step D5).
Specifically, when the user designates a Green color and sets the two-color mixed output mode, the Yellow-Cyan hue plane (hue area) that is the area is specified.

Next, the reference characteristic setting unit 22a sets the reference characteristic based on the maximum output density value S that can be reproduced together in two hues (step D6).
In the case of this embodiment, as a result of analyzing the input / output characteristics of Yellow and the input / output characteristics of Cyan, the maximum output density value S (= 40) of Yellow can be extracted, and therefore, based on the maximum output density value S. To set the reference characteristics.
Then, the correction table generation unit 23a generates a reference correction table corresponding to the set reference characteristic, and print processing is executed via the calibration unit 24a (step D3).
As a result, the absolute value calibration relating to the two colors used for the mixed color output is performed.

If it is determined in step D4 that the two-color output designation is not set (step D4: NO), the image forming apparatus 100 next determines whether or not there is an output designation based on the three-color mixture (step D4). D7).
Specifically, it is determined whether or not an output mode based on three colors (that is, CMY) is set by a predetermined operation by the user.
If it is determined in step D7 that the three-color mixed color output is designated (step D7: YES), the reference characteristic setting unit 22a determines the reference characteristic based on the maximum output density value S that can be reproduced together in each hue of CMY. Is set (step D8).
In the case of this embodiment, as a result of analyzing the input / output characteristics of Yellow, Magenta, and Cyan, the maximum output density value S (= 35) of Yellow can be extracted (see FIG. 6). Set the reference characteristics based on

Then, the correction table generation unit 23a generates a correction table corresponding to the set reference characteristic, and the printing process is executed via the calibration unit 24a (step D3).
As a result, the absolute value calibration relating to the three colors used for the mixed color output, that is, CMY is performed.

If it is determined in step D7 that the three-color output designation is not set (step D7: NO), the reference characteristic setting unit 22a can reproduce the maximum of four colors of CMYK as in the first or second embodiment. A reference characteristic is set based on the output density value S (step D9), and then the correction table generation unit 23a generates a correction table corresponding to the reference characteristic, and a printing process is executed via the calibration unit 24a. (Step D3).
In the present embodiment, absolute value calibration has been described as an example. However, the present invention is not limited to such an embodiment, and relative value calibration or hybrid calibration is performed at the time of monochromatic output or mixed color output. It is also possible to do.

As described above, according to the image forming apparatus 100 of the present embodiment, the configuration is almost the same as that of the first to third embodiments. Play.
However, the image forming apparatus 100 according to the present embodiment includes a single color designation unit 25a and a color mixture designation unit 26a, and can perform a single color output designation or a color mixture output designation according to a user's request.
In addition, when performing mixed color output, the hue determination unit 27a automatically recognizes a predetermined hue plane, and the reference characteristic setting unit 22a tries to harmonize two colors or three colors related to the hue plane. The reference characteristics are set in

Therefore, the function of reproducing the original density of the primary color more accurately is provided as a variation.
In addition, the entire color is harmonized in accordance with a change in color mixture such as two colors, three colors, or four colors.
For this reason, it is possible to realize a calibration apparatus that is more reproducible and convenient.

Note that the calibration apparatus and calibration method of the present invention described above are realized by processing, means, and functions executed by a computer in accordance with instructions of a program (software). The program sends a command to each component of the computer to perform predetermined processing and functions as shown below. That is, each processing / means in the calibration apparatus and the calibration method of the present invention is realized by specific means in which the calibration program of the present invention and the computer cooperate.
Note that all or part of the calibration program is provided by, for example, a magnetic disk, optical disk, semiconductor memory, or any other computer-readable recording medium, and the program read from the recording medium is installed in the computer. Executed. The program can also be loaded and executed directly on a computer through a communication line without using a recording medium.

  As described above, the calibration apparatus, the calibration method, and the calibration program of the present invention have been described with reference to the preferred embodiments. Needless to say, the present invention is not limited thereto, and various modifications can be made within the scope of the present invention.

For example, in the so-called hybrid calibration in the third embodiment, absolute value calibration and relative value calibration are combined according to a section, but by fusing a correction table using the following equation: A desired hybrid correction table may be generated.
Hybrid correction table C = absolute value correction table A * α + relative value correction table B * β

Here, α and β can be set to arbitrary values (where α + β = 1 (α and β are each a real number of 0 to 1)), for example, the hybrid shown in FIG. In order to generate the correction table C, α and β may be set as follows.
(1) Section of gradation value 0 ≦ X ≦ 150: α (i) = 0, β (i) = 1 (where X is an integer indicating a gradation value, and i = X, hereinafter. The same.)
(2) Section of gradation value 150 <X ≦ 184: α (i) = (0.5 / 34) × j (j = 1, 2,... 33,34), β (i) = 1−α ( i) (provided that j = i−150)
(3) Section of gradation value 184 <X ≦ 255: α (i) = β (i) = 0.5

That is, it is possible to generate a desired correction table by such calculation.
Therefore, the present embodiment can be implemented only by a simple program change, and the present invention can be realized more easily.

  The present invention can be suitably used for an image forming apparatus having a gamma correction table.

It is an input / output characteristic diagram showing input / output characteristics in a general image forming apparatus. FIG. 10 is a correction table characteristic diagram showing general characteristics of a gamma correction table provided in advance in the image forming apparatus. 1 is a block diagram illustrating a configuration of an image forming apparatus according to a first embodiment of the present invention. It is a functional block diagram which shows the structure of the image process part concerning this embodiment. FIG. 2 is an input / output characteristic diagram showing input / output characteristics and reference characteristics after the input / output characteristics shown in FIG. 1 are subjected to absolute value correction processing in the first embodiment of the present invention. It is an input / output characteristic diagram showing each input / output characteristic after performing an absolute value correction process for each CMYK in the first embodiment of the present invention. FIG. 6 is an input / output characteristic diagram showing a state in which the yellow input / output characteristic fluctuates in the first embodiment of the present invention. It is an input / output characteristic diagram showing each reference characteristic of C, M, Y, K in the first embodiment of the present invention. It is a gamma table characteristic diagram showing a correction table generated in the image forming apparatus of the first embodiment of the present invention. It is explanatory drawing for demonstrating the calibration means which concerns on 1st embodiment of this invention. It is an input / output characteristic diagram showing the input / output characteristics realized by the calibration processing according to the first embodiment of the present invention. It is the flowchart which showed the procedure of the calibration method which concerns on 1st embodiment of this invention. FIG. 10 is an input / output characteristic diagram showing each input / output characteristic and a reference characteristic after the input / output characteristic shown in FIG. 1 is subjected to relative value correction processing in the second embodiment of the present invention. It is an input / output characteristic diagram showing each input / output characteristic after performing a relative value correction process for each CMYK in the second embodiment of the present invention. It is an input-output characteristic diagram for demonstrating the setting process of the reference | standard characteristic which concerns on 2nd embodiment of this invention. It is an input / output characteristic diagram showing C, M, Y, K reference characteristics set by the reference characteristic setting means of the second embodiment of the present invention. It is a gamma table characteristic figure which shows the correction table produced | generated in the image forming apparatus of 2nd embodiment of this invention. It is the input / output characteristic figure which showed the input / output characteristic implement | achieved by the calibration process which concerns on 2nd embodiment of this invention. It is the flowchart which showed the procedure of the calibration method which concerns on 2nd embodiment of this invention. FIG. 10 is an input / output characteristic diagram illustrating input / output characteristics of a general image forming apparatus according to a third embodiment of the present invention. It is an input-output characteristic figure which shows the input-output characteristic after implementing hybrid calibration regarding 3rd embodiment of this invention. FIG. 10 is an input / output characteristic diagram showing the reference characteristics set by the reference characteristic setting means in each third embodiment of the present invention for each CMYK. It is a gamma table characteristic view showing a correction table generated in the image forming apparatus of the third embodiment of the present invention. It is the flowchart which showed the procedure of the calibration method which concerns on 3rd embodiment of this invention. It is the functional block diagram which showed the structure of the image process part which concerns on 4th embodiment of this invention. It is the flowchart which showed the procedure of the calibration method which concerns on 4th embodiment of this invention. It is a conceptual diagram for demonstrating the general concept of a gamma correction process. It is a hue ring diagram which shows a mode that an ideal hue ring and a hue ring are fluctuate | varied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 20 Image forming apparatus 21 Characteristic acquisition means 22 Reference characteristic setting means 23 Correction table generation means 24 Calibration means

Claims (10)

A calibration device for matching or approximating a preset ideal input / output characteristic with an input / output characteristic indicating a relationship between a density setting value and an output density value in image processing,
Characteristic acquisition means for acquiring input / output characteristics of a predetermined color relating to an output image for each color;
A reference characteristic setting unit that selects an input / output characteristic related to one color from the input / output characteristics based on a predetermined condition, and sets a reference characteristic correlated based on the input / output characteristic for each color,
Correction table generating means for generating a correction table corresponding to the reference characteristic for each color;
Calibration means for calibrating the input / output characteristics for each color related to the output image to the reference characteristics set for the color by correcting the output density value based on the correction table ;
The reference characteristic setting means includes
After extracting the maximum output density value that can be output based on the input / output characteristics of the predetermined color obtained through the characteristic acquisition means for each color, an ideal density setting value corresponding to each maximum output density value is After calculating for each color and selecting the smallest density setting value from the calculated ideal density setting values, for the interval from the minimum density setting value that can be set to the one density setting value, calibration apparatus characterized that you set the reference characteristic to match the corresponding output density value to an output density value of the input and output characteristics of the ideal. A calibration device for matching or approximating a preset ideal input / output characteristic with an input / output characteristic indicating a relationship between a density setting value and an output density value in image processing,
Characteristic acquisition means for acquiring input / output characteristics of a predetermined color relating to an output image for each color;
A reference characteristic setting unit that selects an input / output characteristic related to one color from the input / output characteristics based on a predetermined condition, and sets a reference characteristic correlated based on the input / output characteristic for each color,
Correction table generating means for generating a correction table corresponding to the reference characteristic for each color;
Calibration means for calibrating the input / output characteristics for each color related to the output image to the reference characteristics set for the color by correcting the output density value based on the correction table ;
The reference characteristic setting means includes
An input / output characteristic related to one color that minimizes an error from the ideal input / output characteristic is extracted from the input / output characteristics of the predetermined color obtained through the characteristic acquisition unit, and a predetermined standard regarding the input / output characteristic is extracted. in terms of setting the characteristics calibration apparatus characterized that you set by correlating the reference characteristic for the other colors to the predetermined reference characteristic. The reference characteristic setting means includes
For the section from the minimum density setting value to an arbitrary density setting value equal to or less than the one density setting value, the corresponding output density value is matched with the ideal input / output characteristic and set from the arbitrary density setting value. calibration apparatus according to claim 1, wherein for setting the characteristics is approximated to the input and output characteristics of the ideal while maintaining the gradation as the reference characteristic for section up maximum density setting value that may. Provided with a single color designation means for designating an arbitrary single color to be output in accordance with a predetermined operation,
The characteristic acquisition means acquires the monochrome input / output characteristics related to an output image,
It said reference characteristic setting means, the calibration apparatus according to any one of claims 1 to 3 sets the reference characteristic based on the monochrome input-output characteristic. A color mixture designation means for designating an arbitrary color to be output by two color mixture according to a predetermined operation;
Hue determination means for determining a hue region to which the specified color belongs, and for determining two colors constituting the hue region,
The characteristic acquisition unit, the calibration apparatus according to any one of claims 1 to 4 to obtain the input-output characteristics of the dichroic constituting the hue area per its color. The color mixture designation means designates an arbitrary color to be output by a three color mixture according to a predetermined operation,
The hue determination unit determines a hue region to which the specified color belongs, and determines three colors constituting the hue region,
The characteristic acquisition unit, the calibration apparatus according to any one of claims 1 to 5 to obtain a three-color input-output characteristic constituting the hue area per its color. A calibration method for matching or approximating an input / output characteristic indicating a relationship between a density setting value and an output density value in image processing to a preset ideal input / output characteristic,
A characteristic acquisition step for acquiring, for each color, input / output characteristics of a predetermined color relating to the output image;
A reference characteristic setting step of selecting an input / output characteristic related to one color from the input / output characteristics based on a predetermined condition, and setting a reference characteristic correlated based on the input / output characteristic for each color,
A correction table generating step for generating a correction table corresponding to the reference characteristic for each color;
By correcting the output density value based on the correction table, it has a, a calibration step for calibrating the input-output characteristic of each of the color relates to the output image to said reference characteristics set for that color,
The reference characteristic setting step includes:
After extracting the maximum output density value that can be output based on the input / output characteristics of the predetermined color obtained in the characteristic acquisition step for each color, an ideal density setting value corresponding to each maximum output density value is set for each color. And selecting a minimum density setting value from the calculated ideal density setting values, and then corresponding to a section from the minimum density setting value that can be set to the one density setting value. A calibration method for setting the reference characteristic so that an output density value matches an output density value of the ideal input / output characteristic . A calibration method for matching or approximating an input / output characteristic indicating a relationship between a density setting value and an output density value in image processing to a preset ideal input / output characteristic,
A characteristic acquisition step for acquiring, for each color, input / output characteristics of a predetermined color relating to the output image;
A reference characteristic setting step of selecting an input / output characteristic related to one color from the input / output characteristics based on a predetermined condition, and setting a reference characteristic correlated based on the input / output characteristic for each color,
A correction table generating step for generating a correction table corresponding to the reference characteristic for each color;
By correcting the output density value based on the correction table, it has a, a calibration step for calibrating the input-output characteristic of each of the color relates to the output image to said reference characteristics set for that color,
The reference characteristic setting step includes:
From the input / output characteristics of the predetermined color obtained in the characteristic acquisition step, an input / output characteristic related to one color that minimizes an error from the ideal input / output characteristic is extracted, and a predetermined reference characteristic related to the input / output characteristic is obtained. A calibration method for setting the reference characteristics for other colors in correlation with the predetermined reference characteristics after setting . A calibration program for matching or approximating an input / output characteristic indicating a relationship between a density setting value and an output density value in image processing to a preset ideal input / output characteristic,
A given computer,
Characteristic acquisition means for acquiring input / output characteristics of a predetermined color relating to an output image for each color;
A reference characteristic setting means for selecting an input / output characteristic related to one color from the input / output characteristics based on a predetermined condition, and setting a correlated reference characteristic for each color based on the input / output characteristic,
Correction table generating means for generating a correction table corresponding to the reference characteristic for each color;
By correcting the output density value based on the correction table, the input / output characteristics for each color relating to the output image function as calibration means for calibrating the reference characteristics set for the color , and
The reference characteristic setting means;
After extracting the maximum output density value that can be output based on the input / output characteristics of the predetermined color obtained through the characteristic acquisition means for each color, an ideal density setting value corresponding to each maximum output density value is After calculating for each color and selecting the smallest density setting value from the calculated ideal density setting values, for the interval from the minimum density setting value that can be set to the one density setting value, A calibration program for functioning as a means for setting the reference characteristic so that the corresponding output density value matches the output density value of the ideal input / output characteristic . A calibration program for matching or approximating an input / output characteristic indicating a relationship between a density setting value and an output density value in image processing to a preset ideal input / output characteristic,
A given computer,
Characteristic acquisition means for acquiring input / output characteristics of a predetermined color relating to an output image for each color;
A reference characteristic setting means for selecting an input / output characteristic related to one color from the input / output characteristics based on a predetermined condition, and setting a correlated reference characteristic for each color based on the input / output characteristic,
Correction table generating means for generating a correction table corresponding to the reference characteristic for each color;
By correcting the output density value based on the correction table, the input / output characteristics for each color relating to the output image function as calibration means for calibrating the reference characteristics set for the color , and
The reference characteristic setting means;
An input / output characteristic related to one color that minimizes an error from the ideal input / output characteristic is extracted from the input / output characteristics of the predetermined color obtained through the characteristic acquisition unit, and a predetermined standard regarding the input / output characteristic is extracted. A calibration program for functioning as means for setting the characteristics and correlating the reference characteristics for other colors with the predetermined reference characteristics .

Images