JP2020152030A - Image processing system, image processing method and image processing program - Google Patents

Abstract

To enable highly accurate calculation of an appropriate amount of gradation correction on each screen.SOLUTION: A forming/holding unit forms or holds, as a binarized image, a dither pattern of other gradation processing system. An image formation unit forms a plurality of detection patterns onto an image carrier, and a detection unit detects the plurality of formed detection patterns. A holding unit holds a plurality of detection units corresponding to the plurality of detected detection patterns. An acquisition unit acquires, as a correction target value, a fixed set value or a previous detection value and acquires a correction coefficient. A temporary calculation unit calculates, from the acquired target value and detection values, a temporary correction characteristic corresponding to the detection patterns. From the temporary characteristic and the acquired correction coefficient, a correction characteristic calculation unit calculates a correction characteristic corresponding to the detection patterns. A density correction characteristic formation unit combines the density correction characteristic for each of gradation characteristics and the correction characteristic corresponding to the detection patterns, and newly forms a density correction characteristic for each gradation characteristic.SELECTED DRAWING: Figure 3

Description

The present invention relates to an image processing apparatus, an image processing method, and an image processing program.

In Patent Document 1 (Japanese Unexamined Patent Publication No. 2014-099831), a monochromatic patch image is measured using an image processing means that realizes a plurality of image processing methods expressing a plurality of types of pseudo gradations, and reproduction characteristics are determined. It is disclosed to perform a monochromatic calibration to correct. Further, in Patent Document 1, a color mixing calibration for correcting a color mixing reproduction characteristic is executed from a pattern image including a color mixing patch image formed by using a plurality of color recording agents by one kind of image processing method. Is disclosed.

However, the method of calibrating other dithers using the correction chart output by applying any dither so far is less accurate than the method of outputting the correction chart for each dither, especially highlighting. There is a problem that the gradation correction amount tends to fluctuate on each screen on the side or shadow side.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an image processing apparatus, an image processing method, and an image processing program capable of calculating an appropriate gradation correction amount on each screen with high accuracy. ..

In order to solve the above-mentioned problems and achieve the object, the present invention is an image processing apparatus having a mode for simultaneously calibrating at least two or more gradation processing methods among a plurality of gradation processing methods. Therefore, a creation / holding unit that creates or holds a dither pattern of another gradation processing method as a binarized image, and an image forming unit that sequentially images a plurality of detection patterns on an image carrier in the sub-scanning direction. A detection unit that detects a plurality of imaged detection patterns, a holding unit that holds a plurality of detection values corresponding to the plurality of detected detection patterns, and a fixed set value or a previously detected value as a correction target value. An acquisition unit that acquires one of the above and also acquires a correction coefficient, a provisional calculation unit that calculates a provisional correction characteristic for a detection pattern from the acquired target value and the detected value, a provisional correction characteristic, and an acquired correction coefficient. To the correction characteristic calculation unit that calculates the correction characteristics for the detection pattern, and the density correction characteristics for each gradation characteristic and the correction characteristics for the detection pattern are combined to form a new density correction characteristic for each gradation characteristic. It has a characteristic forming part.

According to the present invention, there is an effect that an appropriate gradation correction amount can be calculated with high accuracy on each screen.

FIG. 1 is a block diagram showing a hardware configuration of the image processing apparatus of the embodiment. FIG. 2 is a functional block diagram showing a functional configuration of the image processing apparatus of the embodiment. FIG. 3 is a flowchart showing the flow of the calculation operation of the γ correction value in the image processing apparatus of the embodiment. FIG. 4 is a diagram for explaining a gradation correction operation in the image processing apparatus of the embodiment. FIG. 5 is a diagram for explaining the effect of the simple calibration method. FIG. 6 is a diagram for explaining a correction method when performing simple calibration. FIG. 7 is a diagram for explaining a method of drawing a pseudo screen from the reference screen. FIG. 8 is a flowchart showing a flow at the time of executing detailed calibration in the image processing apparatus of the embodiment. FIG. 9 is a flowchart showing a flow at the time of executing simple calibration in the image processing apparatus of the embodiment.

Hereinafter, the image processing apparatus of the embodiment will be described with reference to the attached drawings.

(Hardware configuration)
FIG. 1 is a block diagram showing a hardware configuration of the image processing apparatus of the embodiment. As shown in FIG. 1, as the image processing apparatus of the embodiment, a printer, a copying machine, a digital multifunction device, or the like capable of reproducing halftones can be used.

The CPU 1 of the image processing apparatus of the embodiment gives instructions or controls to each block via the CPU bus line 12. The CPU 1 may have a multiprocessor configuration composed of a plurality of CPUs 1. The RAM 2 temporarily stores data at the time of processing each block including the CPU 1. Further, the calibration processing program described later is stored in the ROM 6 and executed by the CPU 1.

The ASIC 3 is a dedicated integrated circuit having a function for image processing, and enables high-speed information processing. The program can be stored in the ROM 6 instead of the ASIC 3 and executed by the CPU 1. The scanner engine 4 reads an image. The printer engine 5 outputs a printed image. As the printer engine 5, an electrophotographic type or an inkjet type printer engine can be used. The NVRAM 7 is formed of a non-volatile memory and holds set values and counter information of the image processing apparatus.

The interface control unit (I / F control unit) 8 receives the print data transmitted from the external device 9. The I / F control unit 8 can support a local connection such as IEEE1284 or USB or a network connection such as Ethernet (registered trademark). The operation unit I / F control unit 10 is used for input / output of information with the operation unit 11 which is a man-machine interface unit with the device operator, such as a button for operating the device and an indicator for displaying the device status.

(Function of image processing device)
FIG. 2 is a functional block diagram of each function realized by the CPU 1 executing a calibration processing program stored in the ROM 6. As shown in FIG. 2, the CPU 1 executes a calibration processing program to determine the density detection pattern image creation unit 21, the density detection unit 22, the density difference calculation unit 23, the printer state difference calculation unit 24, and the correction value. It functions as a unit 25, an input processing unit 26, a storage control unit 27, a correction table creation unit 28, and a target detection unit 29.

In the example of FIG. 2, each function of the density detection pattern image creation unit 21 to the target detection unit 29 is realized by software by a calibration processing program, but some or all of them are ICs ( It may be realized by hardware such as Integrated Circuit).

Further, the calibration processing program may be provided by recording a file in an installable format or an executable format on a recording medium readable by a computer device such as a CD-ROM or a flexible disk (FD). Further, the calibration processing program may be provided by recording on a recording medium readable by a computer device such as a CD-R, a DVD (Digital Versatile Disk), a Blu-ray disc (registered trademark), or a semiconductor memory. Further, the calibration processing program may be provided in the form of being installed via a network such as the Internet. Further, the calibration processing program may be provided by incorporating it into a ROM or the like in the device in advance.

(Calculation operation of γ correction value)
The operation of each of the parts 21 to 29 will be described with reference to the flowchart of FIG. FIG. 3 is a flowchart showing the flow of the calculation operation of the γ correction value. In the flowchart of FIG. 3, first, the density detection pattern image creation unit 21 creates a density detection pattern for calibration (step S1). The density detection unit 22 detects the density detection pattern from the image read by the scanner engine 4 and acquires the density (step S2).

Next, the density difference calculation unit 23 calculates the difference between the calibration target density held in the image processing device of this embodiment and the current density obtained from the density detection unit 22 (step S3). Further, the density difference calculation unit 23 calculates the difference in the current density acquired by the density detection unit 22 for the two patches created by the density detection pattern image creation unit 21 in some gradation values of some screens. ..

Next, the printer state difference calculation unit 24 calculates the difference between the states at the time of the previous calibration and the current state of the image processing device (step S4). Then, the correction value determination unit 25 obtains γ correction data from the difference between the target density calculated by the density difference calculation unit 23 and the current density and the difference in the state of the image processing device calculated by the printer state difference calculation unit 24. calculate.

(Gradation correction operation)
FIG. 4 is a diagram for explaining a gradation correction operation in the image processing apparatus of the embodiment. In FIG. 4, the horizontal axis is the input gradation value and the vertical axis is the density. The solid line graph shows the target density 301 of the image processing apparatus, and shows the output characteristics targeted by the image processing apparatus. The dotted line graph is the density detection value and shows the output characteristics of the actual image processing apparatus. As a method of acquiring the density detection value 302, a method of reading the gradation patch printed on the intermediate transfer belt with a density sensor built in the image processing device or a method of reading the gradation patch printed on paper with a scanner can be used. it can. The thin line graph is the correction γ 303, and shows the γ correction table for correcting the density detection value 302 to the target density 301.

The image processing apparatus of the embodiment includes a plurality of screens, and the change in density characteristics depending on the environment differs for each screen. Therefore, it is desirable to acquire the concentration detection value 302 for each screen. However, since it takes time to acquire the density detection value 302 for each screen, a method of acquiring the output characteristics of the image processing apparatus using a reference screen (called a reference screen) may be used. Although the amount of change in gradation characteristics differs depending on the environment of each screen, the tendency of "darkening" or "lightening" does not change, so calibration can be performed using a reference screen.

As the reference screen, a screen dedicated to calibration may be used, or a screen that can be selected by the user at the time of printing may be used. Hereinafter, the method of calibrating the selected screen is referred to as "detailed calibration method", and the method of calibrating using the reference screen is referred to as "simple calibration method".

It is not necessary to distinguish between the "detailed calibration method" and the "simple calibration method" as separate methods, and when the detailed calibration method is executed, the density of the selected screen is detected for the screen that was not selected. The "detailed calibration method" and the "simple calibration method" may be executed at the same time by correcting from the value.

(Simple calibration method)
FIG. 5 is a diagram for explaining the effect of the simple calibration method. In FIG. 5, the solid straight line graph shows the target density 401 of the image processing apparatus. Further, the graph of the thin line curve shows the density detection value 402 of the screen 1, and the dotted line graph shows the density detection value 403 of the reference screen different from the screen 1. Further, the thin line graph between the target density 401 and the density detection value 403 shows the density 404 of the screen 1 after the simple calibration is executed.

In the case of the simple calibration method, a γ correction table is created so that the reference screen approaches the target density 401. However, there is a difference in the density characteristics between the reference screen and the screen to be calibrated, such as the density detection value 402 of the screen 1 and the density detection value 403 of the reference screen. Therefore, the correction accuracy in the case of the simple calibration method is inferior to that of the detailed calibration method in which the correction is performed directly from the density detection value of the screen to be corrected.

By predicting the density detection value of the screen to be corrected from the density detection value of the reference screen, the correction accuracy of the simple calibration method can be improved, but basically the correction accuracy of the simple calibration method is detailed calibration. It does not exceed the correction accuracy of the screen. Therefore, if the simple calibration is executed immediately after the execution of the detailed calibration, the deviation from the target becomes large due to the execution of the calibration. Since the detailed calibration method is more accurate than the simple calibration method, it is not a problem to execute the detailed calibration on a specific screen immediately after executing the simple calibration.

(Correction operation when executing simple calibration)
FIG. 6 is a diagram for explaining a correction method when performing simple calibration. In FIG. 6, the graph shown by the thin line is the density detection value 501 of the pseudo screen 1 obtained from the patch in which the dither of the screen 1 is simulated on the reference screen when the simple calibration mode is executed. The dotted line graph shows the density detection value 502 of the reference screen when the simple calibration mode is executed. Further, the solid line graph shows the correction density detection value 503. The density detection value 501 of the pseudo screen 1 may be acquired with all input gradation values, or only a part of the input gradation values may be acquired.

In the simple calibration mode, the gradation characteristic peculiar to the screen cannot be corrected. Therefore, when correcting the screen 1, instead of creating the γ correction table directly from the density detection value 502 of the reference screen, the reference screen density detection value 502 and the density detection value 501 of the pseudo screen 1 are combined. It is possible to solve this problem.

Specifically, the correction density detection value 503 is created according to the difference between the reference screen density detection value 502 and the density detection value 501 of the pseudo screen 1. The correction density detection value 503 is calculated by the following equation (1).

Correction density detection value = (pseudo screen 1 density detection value x correction factor 1) + (reference screen density detection value x correction factor 2) ... (Equation 1 formula)

As an example, in this equation, the correction factor is 1 + the correction factor is 2 = 100.

The correction factor 1 of the equation 1 represents the reflection rate of the density detection value of the pseudo screen 1 in the simple calibration mode. Further, the correction factor 2 represents the reflection rate of the density detection value of the reference screen in the simple calibration mode. This correction factor can be switched for each screen.

In the equation 1, the density detection value 502 of the reference screen is used as it is, but the density detection value of the screen to be corrected is predicted in advance from the density detection value 502 of the reference screen, and the reference screen density detection value 502. It may be used instead of.

Further, in the example of FIG. 6, the density detection value for each screen and the density detection value of the reference screen are directly combined, but the density of the reference screen is also acquired when the detailed calibration mode is executed, and the density change of the reference screen is obtained. You may use the amount.

(Operation to obtain the correction factor from the difference in the concentration detection value)
As shown in Table 1 below, the correction factor may be obtained based on the difference in the concentration detection values.

As can be seen from Table 1, when the difference between the concentration detection values is small, it is considered that the amount of change between the reference screen and the screen 1 is small. Therefore, when the difference in the density detection value is small, for example, 0 or more and less than 30, the density variation of the pseudo screen 1 is larger than the density characteristic difference between the reference screen and the screen 1, so the correction factor 1 is 10%. And so on.

It should be noted that the correction factor may be obtained from a plurality of judgment indexes, such as obtaining and averaging the correction factors of each index from the plurality of judgment indexes of the state of the image processing device of the embodiment. Further, the state of the image processing device and the density detection value of the reference screen may be stored, and the calculation formula of the correction factor may be updated from the relationship between the change in the state of the image processing device and the change in the density detection value of the reference screen. ..

(Operation to draw a pseudo screen from the reference screen)
FIG. 7 is a diagram for explaining a method of drawing a pseudo screen from the reference screen. In normal printing, as shown in FIG. 7A, the image processing apparatus holds a threshold value for determining whether to paint a pixel for an input gradation value from 0 to 255 (8 bits) as a dither pattern. ing. On the other hand, when drawing the pseudo screen from the reference screen, as shown in FIG. 7B, the binarized image of the specific dither pattern is used for drawing.

This may be stored in the image processing apparatus as a dither used only at the time of calibration, or may be stored in the image processing apparatus as an image or a chart. Further, it may be prepared on the personal computer device side.

(Detailed calibration operation)
Next, the flow at the time of executing the detailed calibration will be described with reference to the flowchart of FIG. In the flowchart of FIG. 8, in step S11, the input processing unit 26 shown in FIG. 2 detects the screen for performing the selected calibration via the operation unit 11.

In step S12, the density detection pattern image creation unit 21 prints the density detection pattern on the intermediate transfer belt or paper. In step S13, the storage control unit 27 stores the state of the image processing device when the density detection pattern is drawn in step S12 in a storage unit such as NVRAM 7. In step S14, the density detection unit 22 acquires the density of the density detection pattern. The acquired concentration information is stored in the storage unit in the NVRAM 7 or the like by the storage control unit 27. In step S15, the correction table creation unit 28 creates a γ correction table from the concentration data measured in step S14.

(Simple calibration operation)
Next, the flow at the time of executing the simple calibration will be described with reference to the flowchart of FIG. In the flowchart of FIG. 9, in step S21, the density detection pattern to which the reference screen is applied and the density detection pattern imitating the pseudo screen on the reference screen are printed on the intermediate transfer belt or the paper.

In step S22, the density detection unit 22 measures the density of the density detection pattern. In step S23, the target detection unit 29 acquires information on which screen the screen to be calibrated is among the screens held by the image processing device of the embodiment. The screen to be calibrated may be all the screens of the image processing device, or may be selected by the user in advance.

Steps S24 to S27 perform processing on the screen to be calibrated. That is, in step S24, the difference between the density detection value is obtained by using the density data obtained when the density detection pattern of the reference screen is printed in step S21 and the density data obtained from the pattern to which the pseudo screen to be calibrated is applied in step S21. calculate.

In step S25, the correction factor is determined from the difference in the concentration detection values obtained in step S24. In step S26, the density data for calibration is calculated from the correction factor determined in step S25, the density data of the reference screen acquired in step S22, and the density data of the individual screens acquired in step S23.

If there is no calibration result by the corresponding screen, the process proceeds to step S27, and the γ correction table is calculated from the density detection value of the reference screen. In step S28, it is determined whether or not the calibration has been performed on all the screens to be calibrated. If it is determined that all screens have not been calibrated (step S28: No), the processes of steps SS24 to S28 are repeated until it is determined that calibration has been performed on all screens in step S28. Execute. On the other hand, when it is determined that the calibration has been performed on all the screens (step S28: Yes), all the processing of the flowchart of FIG. 9 is completed.

As is clear from the above description, the image processing apparatus of the embodiment calibrates the state of the image processing apparatus when the gradation method to be calibrated and the gradation method of the pattern used for calibration are the same. Compare the state of the image processing device when a pattern of another gradation method is simulated with the gradation method of the target, and change the reflection rate of each calibration data from the difference in that state. create. Then, when the correction chart is output, the screen with a high number of lines is used to simulate the screen with a low number of lines, and the correction result with an arbitrary dither is shared by a plurality of dithers. As a result, it is possible to selectively and pseudo-reproduce the part where the accuracy tends to deteriorate for each screen, and while suppressing the running cost and shortening the calibration time, the appropriate gradation correction amount is applied to each screen at the time of calibration. Can be calculated.

Finally, the above embodiments are presented as an example and are not intended to limit the scope of the invention. This novel embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. Further, the embodiment and the modification of the embodiment are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalent scope thereof.

1 CPU
2 RAM
3 ASIC
4 Scanner engine 5 Printer engine 6 ROM
7 NVRAM
11 Operation unit 21 Concentration detection pattern image creation unit 22 Concentration detection unit 23 Concentration difference calculation unit 24 Printer state difference calculation unit 25 Correction value determination unit 26 Input processing unit 27 Memory control unit 28 Correction table creation unit 29 Target detection unit

Japanese Unexamined Patent Publication No. 2014-099831

Claims (9)

An image processing apparatus having a mode for simultaneously calibrating at least two or more gradation processing methods among a plurality of gradation processing methods.
A creation / holding unit that creates or holds a dither pattern of another gradation processing method as a binarized image,
An image-forming unit that sequentially images a plurality of detection patterns on the image carrier in the sub-scanning direction,
A detection unit that detects a plurality of imaged detection patterns,
A holding unit that holds a plurality of detected values corresponding to the plurality of detected detection patterns,
As a correction target value, an acquisition unit that acquires either a fixed set value or a previously detected value and also acquires a correction coefficient,
A provisional calculation unit that calculates a provisional correction characteristic for the detection pattern from the acquired target value and the detection value.
A correction characteristic calculation unit that calculates a correction characteristic for the detection pattern from the provisional correction characteristic and the acquired correction coefficient.
A density correction characteristic forming unit that newly forms a density correction characteristic for each gradation characteristic by synthesizing the density correction characteristic for each gradation characteristic and the correction characteristic for the detection pattern.
An image processing device having. A claim characterized in that when calibrating two or more gradation processing methods at the same time, a pattern to which one or more types of gradation processing methods are applied is used among the gradation processing methods to be calibrated. Item 1. The image processing apparatus according to item 1. The first or second aspect of the present invention, wherein the holding unit holds a printer state when calibrated using a pattern to which the corresponding gradation processing method is applied for each gradation processing method. Image processing equipment. The correction characteristic calculation unit changes the ratio of the correction data from the pattern to which the gradation processing method to be calibrated is applied and the correction data from the pattern to which the other gradation processing method is applied according to the difference in the density detection value. The image processing apparatus according to any one of claims 1 to 3, wherein averaging is performed. The image processing apparatus according to claim 4, wherein the correction characteristic calculation unit does not reflect the correction result of the simple mode when the difference between the density detection values is small. The image processing apparatus according to claim 5, wherein the correction characteristic calculation unit increases the correction factor of the simple mode as the difference between the density detection values increases. The image processing apparatus according to claim 6, wherein the correction factor can be switched according to the gradation processing method. It is an image processing method of an image processing apparatus having a mode of simultaneously calibrating at least two or more gradation processing methods among a plurality of gradation processing methods.
A creation / retention step in which the creation / retention unit creates or retains a dither pattern of another gradation processing method as a binarized image.
An image forming step in which the image forming unit images a plurality of detection patterns on the image carrier in order in the sub-scanning direction,
A detection step in which the detection unit detects the plurality of imaged detection patterns, and
A holding step in which the holding unit holds a plurality of detected values corresponding to the plurality of detected detection patterns.
An acquisition step in which the acquisition unit acquires either a fixed set value or a previously detected value as a correction target value and also acquires a correction coefficient.
A provisional calculation step in which the provisional calculation unit calculates a provisional correction characteristic for the detection pattern from the acquired target value and the detection value.
A correction characteristic calculation step in which the correction characteristic calculation unit calculates a correction characteristic for the detection pattern from the provisional correction characteristic and the acquired correction coefficient.
A density correction characteristic forming step in which the density correction characteristic forming unit synthesizes the density correction characteristic for each gradation characteristic and the correction characteristic for the detection pattern to newly form the density correction characteristic for each gradation characteristic.
Image processing method having. An image processing program of an image processing apparatus having a mode for simultaneously calibrating at least two or more gradation processing methods among a plurality of gradation processing methods.
Computer,
A creation / holding unit that creates or holds a dither pattern of another gradation processing method as a binarized image,
An image-forming unit that sequentially images a plurality of detection patterns on the image carrier in the sub-scanning direction,
A detection unit that detects a plurality of imaged detection patterns,
A holding unit that holds a plurality of detected values corresponding to the plurality of detected detection patterns,
As a correction target value, an acquisition unit that acquires either a fixed set value or a previously detected value and also acquires a correction coefficient,
A provisional calculation unit that calculates a provisional correction characteristic for the detection pattern from the acquired target value and the detection value.
A correction characteristic calculation unit that calculates a correction characteristic for the detection pattern from the provisional correction characteristic and the acquired correction coefficient.
Combining the density correction characteristics for each gradation characteristic and the correction characteristics for the detection pattern to function as a density correction characteristic forming unit for newly forming the density correction characteristics for each gradation characteristic.
An image processing program characterized by.

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