JP2013026786A - Image forming device, control method therefor, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a user to easily confirm whether a change amount is allowable when output image quality largely changes due to execution of automatic gradation correction.SOLUTION: Output density in making an output using a generated correction LUT with respect to a predetermined input density value and output density in making an output using a set LUT currently set with respect to the same are displayed on a user interface. Then, an LUT to be used is determined in accordance with a user input via the user interface.

Description

  The present invention relates to an image forming apparatus such as a copying machine, and more particularly to an image forming apparatus that performs gradation correction processing, an image forming method, a control method thereof, and a program.

  Conventionally, in an image forming apparatus that records a monochrome image or a color image, the density of an output image may become unstable over time due to various factors.

  For example, in an electrophotographic image forming apparatus, a process such as laser exposure in an electrophotographic process, formation of a latent image on a photosensitive member, toner development, toner transfer to a paper medium, and fixing by heat, the temperature and humidity around the apparatus, Or it is easy to be influenced by the change of components over time. Therefore, the output density becomes unstable because the amount of toner finally fixed on the paper changes each time. Such a symptom of unstable density is not unique to the electrophotographic system, and it is known that the same phenomenon occurs in the ink jet recording system, the thermal transfer system, and other various systems.

  As a technique for improving density fluctuations due to the above environment (temperature, humidity) and the like, a technique for creating a tone correction LUT unique to a printer has been conventionally performed. As a method for creating a gradation correction table, first, a test chart on which a gradation pattern is printed is output, and a luminance signal of the gradation pattern of the test chart is read by a reader. Next, the luminance signal is converted by LOG conversion. Since the density signal obtained here is the density characteristic of the printer, the gradation correction LUT is created so that the density characteristic is linear. When actually performing this work, the system user (user and serviceman) outputs a test chart according to the instruction of the operation unit and places it on the document table, and then automatic gradation correction is performed.

  When the density variation factor as described above changes greatly, the gradation correction LUT is largely corrected after automatic gradation correction, and the density and color of the output image may change excessively.

  When operating to maintain stable output gradation by performing automatic gradation correction, the color of the output image will be too different before and after automatic gradation correction. There is a user request to be able to restore the gradation characteristics.

On the other hand, when a satisfactory result is not obtained by the adjustment, a technique that can easily return the gradation correction LUT to the original state has been proposed (for example, see Patent Document 1).
However, the technique of Patent Document 1 has a disadvantage that if the user does not obtain a satisfactory result for the adjustment, the adjustment must be abandoned or the adjustment must be repeated until a satisfactory result is obtained. is there.

  For this reason, Patent Document 2 proposes a technique that allows a user to set a printer correction value, although it is a technique in a digital camera. In the technique of Patent Document 2, not only the validity / invalidity of the correction function of the printer is selected, but also the histogram is displayed on the camera UI to set the optimum output correction by the user and the printer correction value is transmitted from the camera to the printer It has been proposed to output an image in a printer.

JP-A-10-020603 JP 2007-212450 A

  However, in the technique proposed in Patent Document 2, it is necessary to set the correction value from the camera to the printer every time the correction value is set, and the output result from the printer is repeatedly generated by trial and error. It is necessary to check and find the optimum adjustment value. Also in the technique described in Patent Document 1, it is necessary to perform a test print after gradation correction to confirm the actual degree of gradation correction.

  An image forming apparatus according to the present invention includes a correction LUT generation unit that generates a correction LUT that corrects gradation characteristics by reading a gradation pattern, and a correction LUT generation unit that generates a predetermined input density value. The output density when output using the generated correction LUT and the output density when output using the currently set LUT that is not the correction LUT for the input density value are displayed on the user interface. A display means for displaying; and a determining means for determining an LUT to be used in response to a user input via the user interface displayed by the display means.

  By comparing and displaying the output density value when output using the correction LUT for the input image density and the density value calculated by the setting LUT that is not the correction LUT, it is easy to determine whether or not this change in density value is acceptable to the user. Can be confirmed.

1 is a configuration block diagram illustrating an example of a system including an image forming apparatus according to an embodiment of the present invention. It is a flowchart which shows an example of the LUT update procedure after the automatic gradation correction scan which concerns on embodiment of this invention. It is a figure which shows an example of the data flow of the gradation correction | amendment LUT used by embodiment of this invention. It is a figure which shows an example of the density | concentration determination method of the present condition LUT which concerns on embodiment of this invention. It is a flowchart which shows an example of the density | concentration determination method of the present condition LUT which concerns on embodiment of this invention. It is a figure which shows an example of the image of UI which displays the density value which concerns on embodiment of this invention. It is a figure which shows an example of the image of UI which displays the density pattern which concerns on embodiment of this invention. It is a figure which shows an example of the image of UI which displays multiple density | concentration which concerns on embodiment of this invention. It is a figure which shows an example of the intermediate | middle LUT calculation method which concerns on embodiment of this invention. It is a figure which shows an example of the image of UI which displays the intermediate | middle LUT density | concentration which concerns on embodiment of this invention. It is a flowchart which shows an example of the process which selects and sets the use LUT according to user operation which concerns on embodiment of this invention.

  Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a configuration block diagram illustrating an example of a system including an image forming apparatus according to the present embodiment. The overall configuration and operation will be described with reference to this figure.

  The system includes an image forming apparatus 107 that forms an image on a recording material 101, and a user interface (UI) 112 as an operation unit that receives input and output with a user.

  When the automatic gradation correction is performed, the pattern forming unit 103 creates the gradation pattern 102 in the storage area 108 such as SDRAM. The gradation pattern 102 is printed on a recording material 101 such as copy paper through image processing such as halftone processing, development, transfer, and fixing processes. When the recording material 101 on which the gradation pattern 102 is printed is placed on the document table and a scan instruction is input by a user input, the gradation pattern reading unit 104 scans the paper on the document table and sets the pattern density. taking measurement. The correction LUT generation unit 106 generates a correction LUT 105 subjected to tone correction from the measured density, and stores the correction LUT 105 in the correction LUT holding unit 110. The correction LUT holding unit 110 may be a storage unit such as an SDRAM or HDD. The setting LUT 129 is an LUT used in the image forming apparatus 107 before reflecting the result of automatic gradation correction. The setting LUT holding unit 109 uses a storage unit such as SDRAM or HDD, and holds the currently set LUT 129. The set LUT density calculation unit 111 compares the correction LUT 105 obtained by correcting the current tone correction LUT with the set LUT 129 used so far. Then, for the input value to the correction LUT that expects an arbitrary output density, the density that will be obtained when the image is formed using the set LUT is calculated. The set LUT density display means 113 scans the sheet on which the gradation pattern is printed by automatic gradation correction, and when the correction LUT is created, the output density at each of the correction LUT and the set LUT is displayed on the user interface 112. Compare and display. The image forming apparatus 107 selects and determines either the correction LUT or the setting LUT by the user, and selects the LUT 123 to be used for tone correction in the future from among the correction LUT and the setting LUT. At this time, an implementation method in which the set LUT is always used and the set LUT is replaced with the correction LUT only when the correction LUT is selected and determined can be considered.

  Here, the density displayed on the user interface 112 is an arbitrary value determined in advance, or is determined by the display density automatic selection unit 114. The display density automatic selection means 114 can continue to use the set LUT, detect the density that is most different from the case of using the automatic gradation correction result, or looks visually different, and can select the density to be displayed. .

  Instead of the display density on the user interface, the pattern image display means 117 can also preview a rectangular pattern density sample image. The pattern image display unit 117 passes the density value to be created to the display pattern image generation unit 116, creates the display pattern image 115 in the storage area 108, and displays it on the user interface 112.

  As long as only one of the setting LUT and the correction LUT can be selected, the image forming apparatus 107 may be in a state where the setting LUT can only be applied forever. The fine adjustment means 118 displays a button indicating the density of the setting LUT and the correction LUT, and one or more intermediate buttons therebetween, so that the user can reflect the gradation correction result with an intermediate adjustment value. To do. When the selected button is an intermediate button, the fine adjustment unit 118 generates an intermediate LUT 119 from the setting LUT and the correction LUT using an adjustment value corresponding to the position of the selected intermediate button. The fine adjustment unit 118 adds an intermediate LUT 119 to the intermediate LUT creation unit 120 so that the degree of change by correction increases as the position of the intermediate button is closer to the correction LUT, and the degree of change decreases as the position of the intermediate button is closer to the set LUT. Generate (intermediate LUT generation process).

  The intermediate density display means 122 causes the intermediate density calculation means 121 to calculate an output density value when output using an intermediate LUT corresponding to the adjustment value corresponding to the position of the intermediate button, and displays it at the corresponding position of the intermediate button. Displays the density value or display pattern. The LUT selection unit 124 allows the user to select the setting LUT, intermediate LUT, or correction LUT as the LUT 123 used at the time of image formation, and sets the LUT 123, the intermediate LUT, and the correction LUT to be used according to the user selection. Is used. As a method of applying the LUT 123 to be used, there may be a case where there is actually an LUT area in the memory and the setting LUT, intermediate LUT, and correction LUT are copied, or a link to each LUT is specified. .

  When forming an image on the recording material 101 such as paper, the image forming apparatus 107 calculates the toner usage amount of the output image data 127 on the storage area 108 to be output through the toner usage amount calculation unit 125. The image data is subjected to gradation correction using the LUT 123 used by the gradation correction means 128 and subjected to halftone processing to form an image. The toner use amount is used as a toner replenishment amount in the developing device and various engine adjustment parameters. Here, the calculation of the toner usage amount by the toner usage amount calculation unit 125 may be performed on the assumption that an image is formed by applying the correction LUT 105 reflecting the machine tone characteristics of the timing. Here, when the setting LUT 129 or the intermediate LUT 119 is selected by the user instead of the correction LUT 105, the actually used toner consumption amount and the calculated toner consumption amount are different from each other, and the toner replenishment in the developing device is excessive. In some cases, such as failure. Therefore, the toner use amount calculation correction unit 126 reflects the difference between the LUT 123 to be used and the correction LUT 105 in the toner use amount calculation, and corrects the toner consumption amount when the LUT 123 to be used is appropriately calculated. . In addition, although the example of calculating the toner usage amount is described in the example of FIG. 1, it is also possible to calculate the usage amount of color material (color material usage amount calculation process) such as ink in other printing methods. It is. Then, the calculated color material usage amount can be corrected in the same manner as the toner usage amount correction (color material usage amount correction process).

  FIG. 2 is a flowchart showing LUT update procedure control after automatic gradation correction scanning. That is, FIG. 2 shows the flow of LUT update processing after the image forming apparatus 107 reads the gradation pattern 102. In the present embodiment, a program related to the processing shown in this flowchart is stored in a storage device (not shown) of the image forming apparatus 107, read out to a RAM (not shown), and executed by a CPU (not shown).

  First, the image forming apparatus 107 scans the gradation pattern for automatic gradation correction, stores the scan image on the memory, samples the density from the pattern, and generates the correction LUT 105 (step S202). Note that a method for generating the correction LUT 105 is a known technique, and thus description thereof is omitted.

  Next, the image forming apparatus 107 calculates a difference between the setting LUT and the correction LUT (step S203).

  Next, the image forming apparatus 107 calculates the output density value of the set LUT for the input density i which is a predetermined input density value (step S204). Here, as described above, the input density i may be an arbitrary value determined in advance, or is most different from the case where the automatic gradation correction result is applied when the set LUT is continuously used. Or, it can be a characteristic density that looks very different in appearance.

  Next, the image forming apparatus 107 displays the density value of the setting LUT and the correction LUT calculated in step S204 or a display pattern image (step S205).

  Next, the image forming apparatus 107 displays a screen for allowing the user to select whether to apply the setting LUT or the correction LUT, and causes the user to input (step S206).

  Next, the image forming apparatus 107 switches the subsequent processing in accordance with the selection in step S206 (step S207).

  When the setting LUT is selected in S206, the image forming apparatus 107 does not update the LUT to be used (Step S208).

  When the correction LUT is selected in S206, the image forming apparatus 107 updates the LUT to be used with the correction LUT (Step S209).

  The image forming apparatus 107 continues the subsequent correction process using the applied LUT to be used, and ends (step S210).

  By displaying the density values of the set LUT and the correction LUT or the display pattern image as shown in FIG. 2, it is possible to select the set LUT when the density change is large when using the corrected LUT. Become. Thereby, it is possible to prevent the density and color of the output image from changing too much. In the example of FIG. 2, an example of processing for selecting either the setting LUT or the correction LUT is shown, but an intermediate LUT can be applied as the LUT to be used. Details will be described later.

  FIG. 3 is a data flow diagram of the gradation correction LUT used in the present embodiment. When the output image data 301 (127 in FIG. 1) is printed on the recording material 101 such as paper, the image forming apparatus 107 calculates a toner usage amount from the output image data 301 (302), and performs gradation using the LUT to be used. Correction is performed (303). Thereafter, the image forming apparatus 107 performs image processing such as halftone processing on the image data, and then forms an image on a sheet (304).

  Here, an example of the LUT data flow when automatic gradation correction is performed will be described below. The image forming apparatus 107 copies the currently used LUT 303 to the setting LUT 306 (1). When the correction LUT 305 is used, the image forming apparatus 107 copies to the LUT 303 that uses the correction LUT 305 (2). The image forming apparatus 107 creates the intermediate LUT 307 from the correction LUT and the setting LUT (3), and when the intermediate LUT is applied, copies it to the LUT 303 that uses the intermediate LUT 307 (4). That is, when the setting LUT 306 is used, the LUT 303 to be used is not updated. When the correction LUT 305 is used, the LUT 303 to be used is updated by the correction LUT 305. When the intermediate LUT 307 is used, the LUT 303 to be used is updated by the intermediate LUT 307.

  FIG. 4 is a diagram for explaining how to determine the density of the set LUT. The vertical axis 401 in the figure indicates the output level value from the gradation correction means 128 to the engine. Also, the horizontal axis 402 in the figure indicates the input density to the gradation correction means 128. When the correction LUT 403 is applied, the input density 1.2 (405) is output at the output level 406, so that an image can be formed with the density 1.2. Here, when the set LUT 404 is applied, the output level value at the vertical axis position of 407 is obtained at the input density of density 1.2, and the density 0.8 of the input density 409 at the point 408 at which the same output level value is obtained in the correction LUT 403. Will be output.

  FIG. 5 is a flowchart showing an example of how to determine the density of the set LUT. In the present embodiment, a program related to the processing shown in this flowchart is stored in a storage device (not shown) of the image forming apparatus 107, read out to a RAM (not shown), and executed by a CPU (not shown). The flowchart of FIG. 5 shows an example of calculating the input density that maximizes the difference.

  First, the image forming apparatus 107 substitutes 0 for the input density i, 0 for the difference MAX value d, and 0 for the difference MAX input density k (step S502).

  Next, the image forming apparatus 107 repeats the loop while the input density i is equal to or lower than the maximum density. (Step S503).

  Next, the image forming apparatus 107 acquires the output level v of the input density i of the current LUT (step S504).

  Next, the image forming apparatus 107 acquires an input density j that is an output level v in the correction LUT (step S505).

  Next, if the value obtained by subtracting the input density j that is the output level in the correction LUT from the current input density i of the LUT is equal to or greater than the difference MAXd, the image forming apparatus 107 substitutes the value obtained by subtracting j from i. Then, i is substituted into the differential MAX input density k (step S506).

  Next, the image forming apparatus 107 increments i (step S507).

  Next, when the input density is equal to or lower than the maximum density, the image forming apparatus 107 returns to step S503, and otherwise, exits the loop (step S508).

  When the loop exits in step S508, the image forming apparatus 107 next creates a display pattern with the difference MAX input density k and the output density of the current LUT of k (step S509).

  Next, the image forming apparatus 107 displays the density of the setting LUT and the correction LUT (step S510), and ends (step S511). By performing the processing as shown in FIG. 5, the density having the largest difference can be displayed to the user as a comparison target.

  Next, an image diagram of each UI that can be applied in the present embodiment will be described.

  FIG. 6 is an image diagram of a UI for displaying density values in the present embodiment. On the UI 112, a button 601 for using the correction LUT 105 and a button 603 for using the setting LUT 129 are displayed. Also, the density value 604 when the set LUT is used is displayed with respect to the density value 602 when the correction LUT is applied. When the test print button 605 is pressed with the correction LUT application button 601 selected, a sample print is output by applying the correction LUT. When the cancel button 606 is pressed, the screen is exited with the last applied state. When the apply button 607 is pressed, the LUT of the currently selected button is saved as the LUT 123 used.

  FIG. 7 is an image diagram of a UI for displaying a density pattern in the present embodiment. On the UI 112, the density values when the correction LUT 105 is used are represented by Y701, M702, C703, and K704 as brightness on the screen display for each color. Further, the density value when the setting LUT 129 is applied is expressed by the luminance on the screen display for each color as Y705, M706, C707, and K708. Here, the luminance of the pattern displayed on the UI 112 can be displayed as a luminance value obtained by converting the density value into the density luminance. Further, as shown in FIG. 7, numerical values of density values (or luminance values) can be displayed together with the pattern image. By visualizing the pattern image as shown in FIG. 7, the user can easily determine whether to apply the correction LUT.

  FIG. 8 is an image diagram of a UI for displaying a plurality of densities in the present embodiment. On the UI 112, a button 801 for using the correction LUT 105 and a button 802 for using the setting LUT 129 are displayed. Here, the density value when the correction LUT is used is displayed for each of a plurality of densities, and the density value and density pattern when the set LUT is used for each density are displayed. By displaying a plurality of densities as shown in FIG. 8, the user can easily determine the degree of change when the correction LUT is applied.

  Next, an intermediate LUT generated by fine correction by the user will be described. FIG. 9 is a diagram illustrating an intermediate LUT calculation method. In order to create a difference LUT 903 between the correction LUT 901 and the setting LUT 902, the horizontal axis is divided into, for example, 1024 gradations, and a value obtained by subtracting the setting LUT 902 from the correction LUT 901 is created as a difference LUT for each gradation. Here, when the intermediate LUT 906 is created as an LUT between the correction LUT and the setting LUT, the differential LUT can be weighted according to a parameter closer to either the correction LUT or the setting LUT. For example, the weight LUT 904, which is the adjustment value closest to the correction LUT, is an LUT for multiplying the output value of the differential LUT 903 by 0.9 by making all 0.9 outputs with respect to the input values of 0 to 1023. is there. By adding the weighted difference LUT to the setting LUT 902, an intermediate LUT 906 that is closest to the correction LUT can be created. Also, the weight LUT 905 that is the second adjustment value closest to the set LUT is 0.2 output for all input values from 0 to 1023, so that the LUT for multiplying the output value of the differential LUT 903 by 0.2 is obtained. It is. By adding the weighted difference LUT to the setting LUT 902, an intermediate LUT 906 that is second closest to the setting LUT can be created.

FIG. 10 is an image diagram of a UI that displays the intermediate LUT density in the present embodiment. A button 1001 for using the correction LUT 105 and a button 1004 for using the setting LUT 129 are displayed on the UI 112. A pointer 1002 indicating an intermediate LUT 119 that divides each of the buttons 1001 and 1004 is displayed, and a slider 1003 is moved left and right by a user input. Under the correction LUT application button 1001, the density and an image pattern 1005 expressing the density are displayed. Under the setting LUT application button 1004, the density and an image pattern 1007 expressing the density are displayed. .
Further, the density output by the corresponding intermediate LUT and its image pattern 1006 are displayed under each pointer 1002.

  FIG. 11 is a flowchart for selecting and setting a use LUT according to a user operation. The process of FIG. 11 describes an example using an intermediate LUT. In the present embodiment, a program related to the processing shown in this flowchart is stored in a storage device (not shown) of the image forming apparatus 107, read out to a RAM (not shown), and executed by a CPU (not shown).

  First, the image forming apparatus 107 stores the currently used LUT as a setting LUT in a temporary area such as an SDRAM (step S1102).

  Next, the image forming apparatus 107 stores the LUT created by the automatic gradation correction as a correction LUT in a temporary area (step S1103).

  Next, the image forming apparatus 107 copies to the LUT that uses the correction LUT (step S1104).

  Next, the image forming apparatus 107 receives user input from the UI 112 (step S1105).

  Next, the image forming apparatus 107 switches processing according to the content of the user input (step S1106). This user input is, for example, when the “cancel”, “test print”, and “apply” buttons shown in FIG. 10 are pressed, or when the set LUT before or after correction is selected as the LUT to be used, This is the case when the slider is adjusted and the intermediate LUT is selected.

  When the user input is selection of the correction LUT or the setting LUT, the image forming apparatus 107 copies the specified LUT to the LUT that uses the specified LUT (step S1111).

  If the user input is slider adjustment, the image forming apparatus 107 creates an intermediate LUT corresponding to the slider position (step S1107). Then, the image forming apparatus 107 copies the created intermediate LUT to the LUT that uses the intermediate LUT (step S1108).

  If the user input is a test print, the image forming apparatus 107 performs a test print of the test pattern with the currently set LUT to be used (step S1109).

  If the user input is pressing the cancel button, the image forming apparatus 107 copies the setting LUT to the LUT that uses the setting LUT, and the process ends (step S1110).

  If the user input is pressing the apply button, the image forming apparatus 107 ends without doing anything (step S1112).

  In the above-described embodiment, an example in which the LUT itself is copied has been described. However, a case in which a pointer indicating the LUT is replaced may be considered. In the example of FIG. 11 described above, in S1104, S1108, S1110, S1111 and the like, the process of copying to the LUT used by each LUT is performed, but when the apply button is selected in S1106, the actual copy is performed. Processing may be performed.

  As described above, when this embodiment is used, by comparing and displaying the output density value when output using the correction LUT for the input image density and the density value calculated by the set LUT, it is possible to determine whether the amount of change is acceptable to the user. It can be easily confirmed. Furthermore, when the user designates and finely adjusts an arbitrary value between the setting LUT and the correction LUT, the automatic gradation correction result can be finely adjusted and applied within the allowable range of the user.

(Other examples)
In the above example, an example of an electrophotographic system has been described. However, the present invention can also be applied to an ink jet recording system, a thermal transfer system, and other various systems.

  The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed.

Claims (9)

Correction LUT generation means for generating a correction LUT for correcting gradation characteristics by reading a gradation pattern;
An output density when output using a correction LUT generated by the correction LUT generation unit with respect to a predetermined input density value, and a current setting that is not the correction LUT for the input density value are set. Display means for displaying on the user interface the output density when output using the setting LUT;
An image forming apparatus comprising: a determination unit that determines an LUT to be used in response to a user input via the user interface displayed by the display unit.   The display means uses each output density when a plurality of input density values are output using the correction LUT generated by the correction LUT generation means, and a currently set LUT that is not the correction LUT. The image forming apparatus according to claim 1, wherein each output density when the image is output is displayed on a user interface. An intermediate LUT generating unit that generates an intermediate LUT that outputs a density value between the set LUT and the correction LUT with respect to a preset input density value by using the set LUT and the correction LUT;
The image forming apparatus according to claim 1, wherein the display unit further displays an output density when the intermediate LUT is applied and output. The display means displays a plurality of output densities from an output density when output using the set LUT to an output density when output using the correction LUT for a preset input density value. And
The image forming apparatus according to claim 3, further comprising an adjusting unit that adjusts the intermediate LUT so that the output density selected by a user input among the plurality of output densities displayed by the display unit. .   5. The image forming apparatus according to claim 1, wherein the display unit displays at least one of an output density value and a luminance pattern image corresponding to the output density value as an output density. .   The image forming apparatus according to claim 1, wherein the display unit displays a characteristic density at which a difference occurs between the output image of the setting LUT and the output image of the correction LUT. Calculation means for calculating a color material usage amount based on the correction LUT generated by the correction LUT generation means;
The color material usage amount correcting means for correcting the color material usage amount calculated by the calculating means using the LUT to be used determined by the determining means and the correction LUT. The image forming apparatus according to any one of 1 to 6. A correction LUT generation step for generating a correction LUT for correcting gradation characteristics by reading a gradation pattern;
An output density when output using a correction LUT generated by the correction LUT generation step with respect to a predetermined input density value, and a current setting that is not the correction LUT for the input density value are set. A display step for displaying on the user interface the output density when output using the setting LUT;
And a determination step of determining an LUT to be used in response to a user input via the user interface displayed in the display step.   A program for causing a computer to function as the image forming apparatus according to claim 1.

Images