JP2012242467A - Image forming apparatus, image forming method, program, and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately grasp density in the state of being output to a given medium to accurately generate a density correction parameter preventing excessive variation.SOLUTION: An internal image data generation part 102 forms a density pattern if no reflectance-density conversion table exists or is effective, to output the formed pattern to a sheet output part 104; a density measurement part 105 measures a density; a reflectance measurement part 106 measures a reflectance; a table generation part 107 generates a table showing a relationship between the reflectance and the density; and a density correction parameter generation part 108 generates a density correction parameter so that a relationship between a gradation value and the density achieves a predetermined density characteristic. If the reflectance-density conversion table exists and is effective, an internal image forming part 103 outputs a density pattern; the reflectance measurement part 106 measures the reflectance; and the density correction parameter generation part 108 generates the density correction parameter based on the measurement result of the reflectance and the table.

Description

  The present invention relates to an image forming apparatus, an image forming method, a program, and a recording medium that form an image on a predetermined medium.

  Even if the image forming apparatus outputs the same image data, the density may vary with time. Therefore, in order to suppress the density fluctuation with time, a technique has been proposed in which a predetermined pattern is formed in the image forming apparatus and a parameter for changing the density is determined based on the result of measuring the density of the formed pattern. .

  For example, in Patent Literatures 1 and 2, the density of a pattern formed in a printer is created while a density correction table for correcting a density value to a predetermined characteristic by measuring a pattern density of a plurality of gradations previously formed by a printer with a scanner. The reference value is set by measuring the sensor, and then the density of the pattern formed inside the printer is measured by the sensor at a predetermined timing, and the density fluctuation amount obtained by comparing the measured value with the reference value. Based on the above, by correcting the density correction table, density correction is performed in consideration of changes with time in the printer.

  However, in the above-described technique, the density correction parameter is calculated by measuring the density of the pattern on a member of the image forming apparatus such as a transfer drum before being transferred to a predetermined medium such as output paper in the image forming apparatus. As a result, there is a problem that the density in the state of being output to a predetermined medium cannot be accurately grasped due to a change in transfer rate or the like, and the density correction parameter is excessively changed and set inappropriately.

The present invention has been made in view of the above-described problems.
An object of the present invention is to provide an image forming apparatus, an image forming method, a program, and a recording medium that accurately grasp the density in a state of being output to a predetermined medium and accurately create a density correction parameter that does not vary excessively. is there.

  The present invention is an image forming apparatus that corrects an input tone value of image data to an output tone value based on a density correction parameter, and forms an image on a predetermined medium based on the corrected output tone value. And measuring the reflectance of the density pattern formed on a predetermined member in the image forming apparatus with respect to each of the tone values. A first measuring means; an output means for outputting the density pattern on a predetermined medium; a second measuring means for measuring the density of the density pattern output on the predetermined medium for each gradation value; A table creating means for creating a table indicating a relationship between reflectance and density based on a measurement result of reflectance and density for each gradation value at a timing of 1, and at the first timing; Based on the measured density for each gradation value, a density correction parameter for correcting the input gradation value to the output gradation value is created so that the relationship between the gradation value and the density has a predetermined density characteristic. , At the second timing, based on the first measurement result of the reflectance of the density pattern and the table, the input tone value is set so that the relationship between the tone value and the density becomes a predetermined density characteristic. A parameter creating unit that creates a density correction parameter to be corrected to an output gradation value, wherein the parameter creating unit uses the reflectance measurement result when the table is created as a reference at the second timing; To correct the first measurement result of the reflectance so as to be close to, and to create a density correction parameter based on the measurement result of the corrected reflectance and the table And features.

  According to the present invention, with the reflectance measurement result when the reflectance density conversion table is created as a reference, the reflectance measurement result is corrected so as to approach the reference, the corrected reflectance measurement result and Since the density correction parameter is created based on the table, excessive fluctuation of the density correction parameter is suppressed.

1 shows a configuration of an image forming apparatus common to Embodiments 1 to 4 of the present invention. The process flowchart common to Examples 1-4 is shown. It is a figure explaining preparation of a reflectance density conversion table. An example of a density target is shown. The reflectance of a sensor and the correction | amendment reflectance of Example 1, 2 are shown. The reflectance used as the reference of Examples 1 and 2, the reflectance obtained by the sensor, and the modified reflectance are shown. Reference density correction parameters and density correction parameters of Examples 1, 3, and 4 are shown.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the present invention, the density of the density pattern formed in the image forming apparatus is measured by a sensor, and the state in which the density pattern is output on a predetermined medium such as output paper is measured by a colorimeter, thereby obtaining a sensor value (reflection). Rate) and density value correspondence table is created and a sensor value density value conversion table is created. Thereafter, the density or reflectance of the density pattern formed inside the image forming apparatus is measured by the sensor at a predetermined timing. A value is obtained, and a density correction parameter is created using the sensor value density value conversion table. At that time, the sensor value or density value for each density pattern is assigned to the same pattern when the sensor value density value conversion table is created. After correction so that the difference from the sensor value or the density value is small, a density correction parameter is created.

  In the present invention, the density of the density pattern formed in the image forming apparatus is measured by a sensor, and the state in which the density pattern is output on a predetermined medium such as output paper is measured by a colorimeter to obtain a sensor value. By grasping the correspondence between (reflectance) and density value, a sensor value density value conversion table and density correction parameters are created. Thereafter, at a predetermined timing, a density correction parameter is created using a sensor value obtained by measuring the density or reflectance of the density pattern formed in the image forming apparatus with a sensor and a sensor value density value conversion table. The density correction table is modified so that the difference from the density correction parameter at the time of creating the sensor value density value conversion table becomes small.

  FIG. 1 shows the configuration of an image forming apparatus common to the first to fourth embodiments of the present invention. Hereinafter, the gradation value, that is, the image data is represented by an integer value of 0 or more and 255 or less, and the larger the value, the higher the density.

  A print data input unit 101 receives print data from a scanner or a computer, and creates print data converted into a data format that can be easily processed by the image forming apparatus if necessary. The internal image data creation unit 102 creates image data based on the print data created by the print data input unit 101 and image data for creating a density pattern image for grasping density characteristics. Here, the internal image data creation unit 102 includes a process of changing the density of the image data based on a parameter created by a density correction parameter creation unit 108 described later.

  The internal image forming unit 103 irradiates the photosensitive drum in the image forming apparatus with a laser based on the image generated by the internal image data generating unit 102, and further transfers a toner image in which toner is attached to the photosensitive drum to the intermediate transfer belt. To form an image. The paper output unit 104 transfers and fixes the image on the intermediate transfer belt formed by the internal image forming unit 103 to the output paper, and forms an image on the output paper.

  The density measuring unit 105 measures the density of the density pattern image for grasping the density characteristics formed on the output paper by using a colorimeter. If the density measurement unit 105 is configured so that the result of measuring the density of the density pattern image for grasping the density characteristic formed on the output paper can be input to the reflectance density conversion table creation unit 107, the density measurement unit 105 can be connected to the image forming apparatus. It does not need to be included.

  The reflectance measuring unit 106 measures the reflectance of the density pattern image for grasping the density characteristics formed on the intermediate transfer belt by the internal image forming unit 103 with a sensor inside the image forming apparatus. The reflectance density conversion table creation unit 107 is used to determine the density of the density pattern image formed on the output paper for density characteristic grasping, and the density characteristic grasping result formed on the intermediate transfer belt. The reflectance measured by the reflectance measuring unit 106 is input to the reflectance of the density pattern image, and the reflectance indicated by the sensor with respect to the density pattern image on the intermediate transfer belt and the same density pattern on the output paper Then, a correspondence relationship with the density indicated by the colorimeter is obtained, and a reflectance density conversion table is created.

  The density correction parameter creation unit 108 suppresses density fluctuation with time based on the reflectance of the density patch measured by the reflectance measurement unit 106 and the reflectance density conversion table created by the reflectance density conversion table creation unit 107. A density correction parameter is created.

  FIG. 2 shows a processing flowchart common to the first to fourth embodiments (processing procedure for creating density correction parameters at different timings). The internal image data creation unit 102 first determines whether or not a reflectance density conversion table exists (step S201). If it exists, the internal image data creation unit 102 determines whether or not the reflectance density conversion table is valid (step S202). Valid is that the correspondence between reflectance and density can be expected to have not changed significantly since the time when the reflectance density conversion table was created. The determination is made in advance based on conditions such that the time is a predetermined time or less, or the number of output sheets after the reflectance density conversion table is generated is a predetermined number or less. Here, instead of determining whether or not it is valid, it may be configured such that a user who uses the image forming apparatus determines whether or not to use the reflectance density conversion table existing at that time.

  If the result of determination in step S201 or step S202 is No (first timing), the internal image forming unit 103 forms a density pattern and outputs the density pattern to the paper output unit 104. The reflectance of the density pattern is measured by the reflectance measuring unit (sensor) 106 (step S205).

  FIG. 3A shows an example of a density pattern. FIG. 3A shows a patch row having only a black component among the single color components of the image forming apparatus constituted by the patches K00, K01,..., K16. As shown in FIG. 3B, the gradation values for the black component of each patch are given so that K00 is 0, K16 is 255, and K01 to K15 are increased almost uniformly. The gradation value indicates that 0 is the lightest and 255 is the darkest output. Here, the gradation values from K00 to K16 may not be equal.

  This density pattern is formed on the intermediate transfer belt, the reflectance of each patch is read by the sensor of the reflectance measuring unit 106, and the density of each patch output to the output paper by the paper output unit 104 is read by the density measuring unit 105. . The reflectance density conversion table creation unit 107 creates a correspondence relationship between the reflectance read by the sensor and the density read by the measuring device as a table.

  As shown in FIG. 3B, for example, when the reflectance of a patch K00 having a gradation value of 0 is 0.865 and the density is 0.070, the density corresponding to the reflectance 0.865 is 0.00. It can be seen that it is 070. Similarly, by obtaining the corresponding relationship in the other gradation values shown in FIG. 3B, the reflectance density conversion table creation unit 107 creates the reflectance density conversion table as shown in FIG. (Step S206).

  Next, the density correction parameter creating unit 108 creates a density correction parameter so as to realize the relationship between the gradation value and density shown in the predetermined density target (step S207). FIG. 4A shows an example of the density target. For the gradation value 80, the density target is 0.503. This means that image data having a gradation value of 80 is requested to be output at a density of 0.503.

From the relationship between the gradation value and the density shown in FIG. 3B, it can be seen that the density 0.503 is located between the density 0.496 at the gradation value 96 and the density 0.633 at the gradation value 112. . Therefore, the gradation value corresponding to the density of 0.503 is calculated from these by linear interpolation (FIG. 4B). That is, the corresponding tone value is
(0.503−0.496) ÷ (0.633−0.496) × (112−96) + 96≈96.8
It is.

  Therefore, when image data having a gradation value 80 (input gradation value) for obtaining a density of 0.503 is input, a density correction parameter for converting 96.8 to an output gradation value 97 rounded to an integer value. It is expected that desired density characteristics can be obtained by applying

  The discrete density correction parameters shown in FIG. 7A can be obtained by obtaining the corresponding gradation values for the other gradation values shown in FIG. The output tone value of the density correction parameter is corrected so that it falls within the range from 0 to 255, with 0 being less than 0 and 255 being greater than 255. By performing interpolation processing using linear interpolation, spline interpolation, or the like, it is possible to create density correction parameters in increments of gradation values 0 to 255.

  Returning to FIG. 2, if it is determined that the reflectance density conversion table exists and is valid (Yes in steps S201 and 202) (second timing), the internal image forming unit 103 displays the density pattern. Then, only the reflectance of the density pattern is measured by the reflectance measuring unit (sensor) 106 (step S203). Thereafter, the density correction parameter creating unit 108 creates a density correction parameter using the reflectance measurement result and the reflectance density conversion table (step S204).

  Here, a method of creating a density correction parameter when the reflectance of the sensor shown in FIG. 5A is obtained and the reflectance density conversion table of FIG. 3C is used will be described.

As described above, the density target for the gradation value 80 is 0.503 as shown in FIG. Further, from the reflectance density conversion table shown in FIG. 3C, the density 0.503 is located between the density 0.496 at the reflectance 0.322 and the density 0.633 at the reflectance 0.235. Therefore, from these, when the reflectance corresponding to the density of 0.503 is obtained by linear interpolation,
(0.503−0.496) ÷ (0.633−0.496) × (0.235−0.322) + 0.322≈0.3175
Thus, it can be seen that it is 0.3175.

Next, the gradation value corresponding to the reflectance of 0.3175 is obtained from the result of measurement using only the sensor of FIG. Since the reflectance 0.3175 is located between the corresponding reflectances of the gradation value 80 and the gradation value 96, when similarly obtained by linear interpolation,
(0.3175-0.318) ÷ (0.247−0.318) × (96−80) + 80≈80.1
Thus, it can be seen that the gradation value 80.1 corresponds.
Therefore, when image data having a gradation value 80 for obtaining a density of 0.503 is input, a desired density conversion parameter is applied by converting 80.1 to a gradation value 80 that is rounded to an integer value. It can be expected to obtain density characteristics.

  By the way, the sensor in the image forming apparatus is generally less accurate than the colorimeter. Therefore, if the reflectance when measured using only a sensor is completely reflected in the density correction parameter as described above, the density correction parameter changes excessively, and an image output using the density correction parameter is output. The concentration of can vary.

  Therefore, when the density correction parameter creation unit 108 creates the density correction parameter using only the sensor, the reflectance of each patch obtained by the sensor is used as the reflection obtained by the sensor when the reflectance density conversion table is created. The rate is used as a reference, and it is corrected so as to approach the reference. Here, description will be made assuming that the application rate of the reflectance change is reduced to 60%, that is, the difference from the reflectance reference is reduced to 60%.

When the reflectance density conversion table is created from FIG. 3B, the reflectance (reference) of the gradation value 80 is 0.403, and when the density pattern is measured using only the sensor from FIG. 5A. The reflectance of the gradation value 80 is 0.318. That is, the change in reflectance when only the sensor is used with respect to the reference is 0.318−0.403 = −0.085.
-0.085, but the application rate of the reflectance change is 60% as described above.
−0.085 × 0.6 = −0.051
Reflecting -0.051
0.403-0.051 = 0.352
Therefore, the reflectance when only the sensor is used is corrected to 0.352 and used for the creation of the density correction parameter.

  FIG. 5B shows the reflectance modified by setting the application rate of the reflectance change to 60% in the same manner for each gradation value. FIG. 6A shows the reference reflectance and the sensor only. The reflectance obtained by the sensor when the density correction parameter is created using, and the reflectance modified by setting the application rate of the reflectance change to 60% are shown.

  Then, the density correction parameter can be created using the corrected reflectance in the same manner as described above. For example, from FIG. 4A, since the density target for the gradation value 80 is 0.503, and the reflectance corresponding to the density target 0.503 is 0.3175 as described above, the reflection is based on FIG. 5B. A gradation value estimated to obtain a rate of 0.3175 may be obtained and used as a density correction parameter corresponding to the gradation value 80 (input gradation value).

From FIG. 5 (b), the corrected reflectance of the gradation value 80 is 0.352, and the modified reflectance of the gradation value 96 is 0.277.
(0.3175−0.352) ÷ (0.277−0.352) × (96−80) + 80≈87.3
Thus, the gradation value 87 (output gradation value) obtained by rounding 87.3 to an integer value is used as the density correction parameter.

  By obtaining gradation values corresponding to the other gradation values shown in FIG. 4A, density correction parameters (FIG. 7B) when the application rate is 60% are obtained, and these are obtained. By performing interpolation processing using linear interpolation, spline interpolation, or the like, it is possible to create a density correction parameter in increments of gradation values 0 to 255.

  In the above-described embodiments, the method of creating the density correction parameter for black has been described. However, even when the image forming apparatus has a plurality of single colors such as cyan, magenta, and yellow in addition to black such as a color printer, the above-described black is described. The density correction parameter can be generated in the same manner as the method described above.

  Moreover, although the application rate of the reflectance change is uniformly 60%, a configuration in which the application rate is varied according to the gradation value or the reflectance itself may be employed. Thereby, the followability to the density change of the image forming apparatus can be improved by increasing the application rate in the gradation value and reflectance with high accuracy of the sensor.

  As described above, in the first embodiment, the change in the density correction parameter is suppressed from excessively changing by reducing the change in the sensor value from the reference.

  A difference between the second embodiment of the present invention and the first embodiment will be described with reference to FIG.

  When the density correction parameter creation unit 108 of this embodiment creates the density correction parameter using only the sensor, the reflectance of each patch obtained by the sensor is obtained by the sensor when the reflectance density conversion table is created. With reference to the reflectance, correction is made so as not to exceed a predetermined width from the reference. Here, the description will be made assuming that the maximum width of the reflectance change is 0.05, that is, the absolute value of the difference from the reflectance reference is 0.05 or less.

  When the reflectance density conversion table is created from FIG. 3B, the reflectance (reference) of the gradation value 80 is 0.403, and when the density pattern is measured using only the sensor from FIG. 5A. The reflectance of the gradation value 80 is 0.318.

That is, the change in reflectance when using only the sensor with respect to the reference is
0.318-0.403 = -0.085
-0.085, but since the maximum width of the reflectance change is 0.05 as described above,
-0.05 is assumed. That is,
0.403-0.05 = 0.353
Therefore, 0.353 is corrected to reflectivity when only the sensor is used, and is used to create a density correction parameter.

  FIG. 5C shows the reflectance of Example 2 that was corrected by setting the maximum width of the reflectance change to 0.05 for each gradation value, and FIG. 6B is a reference. The corrected reflectance of Example 2 is shown in which the reflectance, the reflectance obtained by the sensor when the density correction parameter is created using only the sensor, and the maximum width of the reflectance change are set to 0.05.

  As described above, in the second embodiment, by restricting the difference in sensor value from the reference state, the density correction parameter is prevented from excessively changing.

  A difference between the third embodiment of the present invention and the first embodiment will be described with reference to FIG.

  The density correction parameter creation unit 108 according to the present embodiment reduces a change from the reference based on the density correction parameter when the reflectance density conversion table is created when creating the density correction parameter using only the sensor. Modify as follows. Here, description will be made assuming that the application rate of density correction parameter change is reduced to 60%, that is, the difference from the density correction parameter reference is reduced to 60%.

  First, as shown in Example 1, based on the reflectance measurement result and the density measurement result shown in FIG. 3B, FIG. 7A for realizing the density target shown in FIG. The density correction parameter shown in FIG. 6 is created and used as the reference density correction parameter.

  Further, based on the result of measuring the reflectance only with the sensor shown in FIG. 5A and the reflectance density conversion table shown in FIG. 3C, the density target shown in FIG. 4A is realized. FIG. 7C shows the density correction parameters of the third embodiment.

  From FIG. 7A, the reference density correction parameter for the gradation value 160 is 150, and the density correction parameter (FIG. 7C) created from the reflectance measured only by the sensor is 204.

Here, when the density correction parameter is created using only the sensor, the change from the reference is reduced to 60% based on the density correction parameter when the reflectance density conversion table is created.
(204−150) × 0.6 + 150 = 182.4
This is rounded to an integer value of 182, and the density correction parameter 204 for the gradation value 160 is corrected to 182, as shown in FIG.

  The gradation values corresponding to the other gradation values shown in FIG. 4A are obtained, and the density correction parameters shown in FIG. 7D are obtained, and these are subjected to linear interpolation or spline interpolation. By performing the interpolation processing used, it is possible to create density correction parameters in increments of gradation values 0 to 255.

  As described above, in the third embodiment, the change in the density correction parameter from the reference is reduced, thereby suppressing the density correction parameter from changing excessively.

  A difference between the fourth embodiment of the present invention and the third embodiment will be described with reference to FIG.

  The density correction parameter creation unit 108 of the present embodiment uses a density correction parameter when creating the reflectance density conversion table as a reference when creating the density correction parameter using only the sensor, and sets a predetermined width from the reference. Correct so that it does not exceed.

  Here, the description will be made assuming that the maximum width of change in the density correction parameter is 10, that is, the absolute value of the difference from the density correction parameter reference is 10 or less.

  First, as shown in Example 3, FIG. 7 (a) for realizing the concentration target shown in FIG. 4 (a) based on the reflectance measurement result and the concentration measurement result shown in FIG. 3 (b). The density correction parameter shown in FIG. 6 is created and used as the reference density correction parameter.

  Further, based on the result of measuring the reflectance only with the sensor shown in FIG. 5A and the reflectance density conversion table shown in FIG. 3C, the density target shown in FIG. 4A is realized. Then, the density correction parameter shown in FIG.

  From FIG. 7A, the reference density correction parameter for the gradation value 160 is 150, and the density correction parameter (FIG. 7C) created from the reflectance measured only by the sensor is 204.

That is, the change in the density correction parameter when using only the sensor with respect to the reference is
204−105 = 54
However, since the maximum value of the density correction parameter change from the reference is 10, as described above,
10 is assumed. That is,
150 + 10 = 160
Accordingly, the density correction parameter 204 for the gradation value 160 is corrected to 160 as shown in FIG.

  As described above, in the fourth embodiment, by restricting the change in the density correction parameter from the reference, it is possible to suppress the density correction parameter from changing excessively.

  According to the present invention, a storage medium storing software program codes for realizing the functions of the above-described embodiments is supplied to a system or apparatus, and the computer (CPU or MPU) of the system or apparatus is stored in the storage medium. It is also achieved by reading and executing the program code. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiment. As a storage medium for supplying the program code, for example, a hard disk, an optical disk, a magneto-optical disk, a nonvolatile memory card, a ROM, or the like can be used. Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an OS (operating system) operating on the computer based on an instruction of the program code. A case where part or all of the actual processing is performed and the functions of the above-described embodiments are realized by the processing is also included. Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. A case where the CPU or the like provided in the board or the function expansion unit performs part or all of the actual processing and the functions of the above-described embodiments are realized by the processing is included. Further, the program for realizing the functions and the like of the embodiments of the present invention may be provided from a server by communication via a network.

DESCRIPTION OF SYMBOLS 101 Print data input part 102 Internal image data creation part 103 Internal image formation part 104 Paper output part 105 Density measurement part 106 Reflectivity measurement part 107 Reflectance density conversion table creation part 108 Density correction parameter creation part

JP 2001-186350 A JP 2001-251510 A

Claims (9)

  An image forming apparatus that corrects an input gradation value of image data to an output gradation value based on a density correction parameter, and forms an image on a predetermined medium based on the corrected output gradation value. Forming means for forming a density pattern of gradation values in the image forming apparatus; and a first measurement for measuring the reflectance of the density pattern formed on a predetermined member in the image forming apparatus for each gradation value. Means, output means for outputting the density pattern on a predetermined medium, second measurement means for measuring the density of the density pattern output on the predetermined medium for each gradation value, and at a first timing A table creating means for creating a table showing a relationship between the reflectance and the density based on the measurement result of the reflectance and the density with respect to each gradation value; and the measurement at the first timing. Based on the density for each gradation value, a density correction parameter for correcting the input gradation value to the output gradation value is created so that the relationship between the gradation value and the density has a predetermined density characteristic, At the timing, the input gradation value is set to the output gradation so that the relationship between the gradation value and the density has a predetermined density characteristic based on the first measurement result of the reflectance of the density pattern and the table. Parameter creating means for creating a density correction parameter to be corrected to a value, and the parameter creating means approaches the reference at the second timing with reference to the reflectance measurement result when the table is created. In addition, the first measurement result of the reflectance is corrected, and a density correction parameter is generated based on the corrected measurement result of the reflectance and the table. Location.   The parameter creation means is a correction in which, for each gradation value of the density pattern, a predetermined ratio of a difference between the reference and the first measurement result of the reflectance is reduced from the reference at the second timing. The image forming apparatus according to claim 1, wherein a reflectance is created.   The parameter creation means sets the absolute value of the difference between the reference and the first measurement result of the reflectance to a predetermined width or less for each gradation value of the density pattern at the second timing, and sets the reference The image forming apparatus according to claim 1, wherein a corrected reflectance in which a width equal to or less than the predetermined width is reduced is created.   An image forming apparatus that corrects an input gradation value of image data to an output gradation value based on a density correction parameter, and forms an image on a predetermined medium based on the corrected output gradation value. Forming means for forming a density pattern of gradation values in the image forming apparatus; and a first measurement for measuring the reflectance of the density pattern formed on a predetermined member in the image forming apparatus for each gradation value. Means, output means for outputting the density pattern on a predetermined medium, second measurement means for measuring the density of the density pattern output on the predetermined medium for each gradation value, and at a first timing A table creating means for creating a table indicating the relationship between the reflectance and the density based on the measurement result of the reflectance and the density, and for each gradation value measured at the first timing. Based on the density, a density correction parameter for correcting the input gradation value to the output gradation value is created so that the relationship between the gradation value and the density has a predetermined density characteristic, and at the second timing, Based on the measurement result of the reflectance of the density pattern and the table, a density correction parameter for correcting the input tone value to the output tone value so that the relationship between the tone value and the density becomes a predetermined density characteristic. Parameter creation means for creating the reflectance, and the parameter creation means at the second timing, based on the density correction parameter at the time of creating the table, the reflectance measurement result so as to approach the reference. An image forming apparatus for correcting a first density correction parameter created based on the image forming apparatus.   The parameter creating means is a corrected density correction in which a predetermined ratio of the difference between the reference and the first density correction parameter is added to the reference for each gradation value of the density pattern at the second timing. The image forming apparatus according to claim 4, wherein a parameter is created.   The parameter creation means sets an absolute value of a difference between the reference and the first density correction parameter to be equal to or less than a predetermined width for each gradation value of the density pattern at the second timing. The image forming apparatus according to claim 4, wherein a correction density correction parameter is created by adding a width equal to or less than a predetermined width.   An image forming method for correcting an input tone value of image data to an output tone value based on a density correction parameter, and forming an image on a predetermined medium based on the corrected output tone value, comprising: A forming step of forming a density pattern composed of gradation values in the image forming apparatus, and a first measurement for measuring the reflectance of the density pattern formed on a predetermined member in the image forming apparatus for each gradation value In a first timing, a step of outputting the density pattern on a predetermined medium, a second measurement step of measuring the density of the density pattern output on the predetermined medium for each gradation value, and A table creation step of creating a table showing the relationship between reflectance and density based on the measurement result of reflectance and density for each gradation value; and the measurement at the first timing. Based on the density for each gradation value, a density correction parameter for correcting the input gradation value to the output gradation value is created so that the relationship between the gradation value and the density has a predetermined density characteristic, At the timing, the input gradation value is set to the output gradation so that the relationship between the gradation value and the density has a predetermined density characteristic based on the first measurement result of the reflectance of the density pattern and the table. A parameter creating step for creating a density correction parameter to be corrected to a value, wherein the parameter creating step is adapted to approach the reference at the second timing with reference to a reflectance measurement result when the table is created. In addition, the first measurement result of the reflectance is corrected, and a density correction parameter is generated based on the corrected measurement result of the reflectance and the table. Law.   A program for causing a computer to realize the image forming method according to claim 7.   A computer-readable recording medium on which a program for causing a computer to realize the image forming method according to claim 7 is recorded.

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