JP2018004828A - Image forming apparatus and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus and program which can set a transfer parameter in consideration of at least one of image defect and density unevenness of an adjustment image without performing processing of comparing a luminance value of one pixel with a luminance value of its peripheral pixel.SOLUTION: An image forming apparatus 10 includes: an image forming unit 82 which forms an image on a recording medium by transferring the image in accordance with a set transfer parameter; and a control unit 50 which performs control for forming an adjustment image while changing the transfer parameter with respect to the image forming unit 82. The control unit 50 derives the density distribution of the adjustment image from read information obtained by reading the adjustment image formed on the recording medium for each transfer parameter, and derives from the derived density distribution the transfer parameter whose value indicating the degree of variations of the density of the adjustment image is within a predetermined allowable range.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image forming apparatus and a program.

  Japanese Patent Application Laid-Open No. 2004-133867 discloses a measuring unit that measures the color of an image formed on a recording medium and an adjustment image forming unit that forms an adjustment image including a composite color in which color materials of two or more component colors are superimposed. And an image forming apparatus including the same. The image forming apparatus is formed on the uppermost layer of the recording medium among the two or more component colors based on a measurement result obtained by the measurement unit measuring a composite color included in the adjustment image. It further comprises density value calculating means for calculating density values of the component colors of the color material. In addition, the image forming apparatus further includes a transfer parameter determining unit that determines a transfer parameter value that defines an operation condition for performing transfer based on the calculated density value.

  Patent Document 2 discloses a mura component enhancement processing step for emphasizing mura components by applying a mura component enhancement filter to each pixel of a captured image, and mura of each pixel obtained in the mura component enhancement processing step. A mura defect detection method having a mura defect detection step of detecting a mura defect based on a component emphasis value is disclosed. In this unevenness defect detection method, in the unevenness component emphasis processing step, the brightness value of each brightness comparison pixel arranged around the target pixel at a predetermined distance from the target pixel selected in the captured image is used as the brightness value of the target pixel. And the number of luminance comparison pixels having a luminance value larger than that of the target pixel is counted. Further, in this unevenness defect detection method, when the number of counted luminance comparison pixels is larger than half of the total number of luminance comparison pixels, the median value at the luminance value of each luminance comparison pixel having a luminance value larger than that of the target pixel. The difference between the value and the luminance value of the target pixel is calculated as the unevenness enhancement value of the target pixel. Further, in this unevenness defect detection method, when the number of counted luminance comparison pixels is less than half of the total number of luminance comparison pixels, the luminance value of each luminance comparison pixel having a luminance value smaller than that of the target pixel. The mura component is emphasized by using a mura component enhancement filter that calculates the difference between the median value at and the luminance value of the target pixel to obtain the mura component enhancement value of the target pixel. In this mura defect detection method, in the mura defect detection step, the mura component emphasis value of each pixel is compared with a predetermined threshold to extract mura defect candidate pixels and detect the mura defect.

JP 2013-195799 A JP 2006-242584 A

  The present invention can set a transfer parameter considering at least one of an image defect and density unevenness of an adjustment image without performing a process of comparing the luminance value of a certain pixel with the luminance values of surrounding pixels. An object is to provide an image forming apparatus and a program.

  In order to achieve the above object, an image forming apparatus according to claim 1 is configured to transfer an image in accordance with a set transfer parameter to form the image on a recording medium, and to the forming unit. On the other hand, a control unit that performs control to form an adjustment image while changing the transfer parameter, and reading of the adjustment image formed by reading the adjustment image formed on the recording medium by the control unit. A derivation unit that derives a density distribution for each transfer parameter, and derives a transfer parameter from which the value representing the degree of variation in density of the adjustment image is within a predetermined allowable range from the derived density distribution. ing.

  According to a second aspect of the present invention, in the first aspect of the present invention, the value representing the degree of density variation is lower than the density having the maximum frequency in the density histogram representing the density distribution. And a value representing the degree of symmetry with the high part.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the value representing the degree of variation in density is a standard deviation of the density in the density distribution.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the read information includes a value indicating the density of each of a plurality of colors, and the derivation unit However, with respect to the density of the complementary color of the adjustment image included in the read information, a density distribution of the adjustment image is derived for each transfer parameter, and the transfer parameter is derived from the derived density distribution. .

  According to a fifth aspect of the present invention, in the invention according to the fourth aspect, the adjustment image includes an image formed on the recording medium by superimposing a plurality of color toners, and the derivation unit includes The density distribution of the adjustment image is derived for each transfer parameter with respect to the density of the complementary color of the toner formed on the uppermost layer of the recording medium included in the read information, and the transfer parameter is derived from the derived density distribution. Is derived.

  The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein the derivation unit transfers the value indicating the density of the adjustment image from the read information. Further derived for each parameter, a transfer parameter is derived in which a value indicating the degree of density variation is within an allowable range, and a value indicating the density is within an allowable range.

  According to a seventh aspect of the present invention, in the invention of the sixth aspect, the derivation unit sets a value indicating the degree of variation in density or a value indicating the density according to a predetermined priority. The transfer parameters are derived by weighting.

  On the other hand, in order to achieve the above object, a program according to an eighth aspect causes a computer to function as a control unit and a derivation unit of the image forming apparatus according to any one of the first to seventh aspects. belongs to.

  According to the first and eighth aspects of the present invention, at least one of the image defect and the density unevenness of the adjustment image is performed without performing the process of comparing the luminance value of a certain pixel with the luminance value of the surrounding pixels. Can be set in consideration of the transfer parameters.

  According to the second aspect of the present invention, it is possible to derive a transfer parameter that further considers an image defect of the adjustment image.

  According to the third aspect of the present invention, it is possible to derive a transfer parameter that further considers the density unevenness of the adjustment image.

  According to the fourth aspect of the present invention, the transfer parameter can be derived with higher accuracy than when the complementary color is not taken into consideration.

  According to the fifth aspect of the present invention, it is possible to derive the transfer parameter with higher accuracy than in the case of using a complementary color of the toner color formed on a layer other than the uppermost layer of the recording medium.

  According to the sixth aspect of the present invention, it is possible to derive a transfer parameter in consideration of the density of the adjustment image.

  According to the seventh aspect of the present invention, it is possible to derive a transfer parameter in accordance with a predetermined priority.

1 is a block diagram illustrating a configuration of an image forming apparatus according to each embodiment. It is a schematic block diagram (fracture side view) which shows the structure of the image formation part which concerns on each embodiment. It is a top view which shows an example of the image for adjustment which concerns on each embodiment. It is a flowchart which shows the flow of a process of the voltage derivation processing program which concerns on each embodiment. It is a graph which shows an example of the relationship between the average value of the density of the patch image concerning each embodiment, and the voltage level of a secondary transfer voltage. It is a graph which shows an example of the density histogram of the patch image which concerns on each embodiment. It is a graph which shows an example of the relationship between the standard deviation of the density of the patch image which concerns on each embodiment, and the voltage level of a secondary transfer voltage. It is a graph with which it uses for description of an example of the derivation | leading-out process of the symmetry degree in the image for adjustment which concerns on each embodiment. It is a graph which shows an example of the relationship between the area ratio in the density histogram which concerns on each embodiment, and the voltage level of a secondary transfer voltage. It is a side view with which it uses for description of the complementary color in the image for adjustment which concerns on each embodiment. It is a table | surface used for description of the derivation | leading-out process of the secondary transfer voltage which concerns on 1st Embodiment. It is the schematic which shows an example of the selection screen concerning each embodiment. 10 is a chart for explaining secondary transfer voltage derivation processing according to the second embodiment.

  DETAILED DESCRIPTION Hereinafter, exemplary embodiments for carrying out the present invention will be described in detail with reference to the drawings.

[First Embodiment]
First, the configuration of the image forming apparatus 10 according to the present embodiment will be described with reference to FIGS. 1 and 2. In the following, when yellow is indicated by Y, magenta color is indicated by M, cyan color is indicated by C, and black color is indicated by K, each component and image need to be distinguished for each color. A description will be given with corresponding color symbols (Y, M, C, K). Further, in the following description, when each component and image are collectively referred to without being distinguished for each color, the description of the color at the end of the code is omitted.

  As shown in FIG. 1, the image forming apparatus 10 according to the present embodiment includes a control unit 50, a paper supply unit 80, an image forming unit 82, an image reading unit 84, a paper discharge unit 86, a communication line I / F (InterFace ) 88 and an operation display unit 90.

  The control unit 50 according to the present embodiment includes a CPU (Central Processing Unit) 60 that controls the overall operation of the image forming apparatus 10 and a ROM (Read Only Memory) 62 in which various programs, various parameters, and the like are stored in advance. I have. The control unit 50 also includes a RAM (Random Access Memory) 64 used as a work area when the CPU 60 executes various programs, a non-volatile storage unit 66 such as a flash memory, and an input / output I / F 68. .

  The CPU 60, the ROM 62, the RAM 64, the storage unit 66, and the input / output I / F 68 are connected to each other via a bus 70 such as an address bus, a data bus, and a control bus. The input / output I / F 68 is connected to a paper supply unit 80, an image forming unit 82, an image reading unit 84, a paper discharge unit 86, a communication line I / F 88, and an operation display unit 90.

  The sheet supply unit 80 according to the present embodiment takes out a sheet storage unit on which a plurality of sheets P (see also FIG. 2) as an example of a recording medium are stacked, and the sheets P stacked in the sheet storage unit one by one. And a supply mechanism for supplying the image forming unit 82.

  As shown in FIG. 2, the image forming unit 82 according to the present embodiment includes four photoreceptors 12 that rotate in the direction of arrow A in FIG. 2 for each of Y, M, C, and K colors. . Further, the image forming unit 82 includes a charger 14 that charges the surface of each photoconductor 12 by applying a charging bias.

  The image forming unit 82 exposes the surface of the charged photoconductor 12 with exposure light modulated based on image data of a corresponding color, and forms an electrostatic latent image on the photoconductor 12. 16 is provided.

  Further, the image forming unit 82 applies a developing bias to the developing roll 18 by a developing bias power source (not shown), thereby developing the electrostatic latent image on the photosensitive member 12 with the corresponding color toner, and Is provided with a developing device 20 for forming a toner image. Further, the image forming unit 82 includes a primary transfer unit 24 that transfers the toner image on the photoconductor 12 to the intermediate transfer belt 22 at the transfer position T1.

  Further, the image forming unit 82 includes a cleaning device 26 on the downstream side of the transfer position T1 along the surface of the photoconductor 12 in the rotation direction of the photoconductor 12. The cleaning device 26 also includes a cleaning blade 28 that removes toner remaining on the surface of the photoconductor 12 after the primary transfer.

  Further, the image forming unit 82 includes a static elimination lamp 29 on the downstream side of the cleaning device 26 along the surface of the photosensitive member 12 in the rotation direction of the photosensitive member 12 and on the upstream side of the charger 14. The neutralization lamp 29 irradiates the surface of the photoconductor 12 with a neutralization light, thereby removing charges remaining on the surface of the photoconductor 12 after the primary transfer.

  The intermediate transfer belt 22 is wound around rollers 30 </ b> A to 30 </ b> C and a backup roll 32 </ b> A of a secondary transfer device 32 described later. The image forming unit 82 also transfers the toner image on the intermediate transfer belt 22 to the paper P supplied from the paper supply unit 80 at the transfer position T2 and the toner transferred to the paper P. And a fixing device 36 for fixing the image.

  Further, the image forming unit 82 includes a cleaning device 38 on the downstream side of the transfer position T2 along the surface of the intermediate transfer belt 22 in the direction of arrow B in FIG. Further, the cleaning device 38 includes a cleaning blade 40 that removes toner remaining on the surface of the intermediate transfer belt 22 after the secondary transfer.

  The image reading unit 84 according to the present embodiment includes an image reading sensor such as a CCD (Charge Coupled Device) line sensor. Then, the image reading unit 84 reads the image formed on the paper P by the image forming unit 82 and outputs the image data obtained by the reading to the CPU 60 via the input / output I / F 68. In the present embodiment, for example, the image reading unit 84 converts each pixel value of R (Red), G (Green), and B (Blue) for each pixel through the input / output I / F 68 as the image data. To the CPU 60.

  The paper discharge unit 86 according to the present exemplary embodiment has a paper discharge unit for discharging the paper P and a paper P on which an image is formed by the image forming unit 82 and the image read by the image reading unit 84 on the discharge unit. A discharge mechanism for discharging is provided.

  The communication line I / F 88 according to the present embodiment transmits / receives communication data to / from an external device. The operation display unit 90 according to the present embodiment accepts an instruction from the user to the image forming apparatus 10, and displays various types of information regarding the operation status of the image forming apparatus 10 to the user. The operation display unit 90 includes, for example, a display button that realizes reception of an operation instruction by executing a program, a display provided with a touch panel on a display surface on which various information is displayed, and hardware keys such as a numeric keypad and a start button. including.

  Next, an image forming process in the image forming apparatus 10 according to the present embodiment will be described.

  When image data indicating an image to be formed is input, the image forming apparatus 10 starts driving (rotating) each photoconductor 12, applies a charging bias to each charger 14, and sets each photoconductor 12. The surface is charged to the negative electrode. On the other hand, the image forming apparatus 10 decomposes the image data into image data of each color of YMCK, and then outputs a modulation signal based on the image data of each color to the laser output unit 16 of the corresponding color. The laser output unit 16 outputs a laser beam L modulated according to the input modulation signal.

  Each of the modulated laser beams L is irradiated on the surface of the photoreceptor 12. The surface of the photoconductor 12 is in a state of being negatively charged by the charger 14, but when the surface of the photoconductor 12 is irradiated with the laser beam L, the charge of the portion irradiated with the laser beam L disappears and the photoconductor 12 is exposed. An electrostatic latent image corresponding to each color image data of YMCK is formed on the body 12.

  When the electrostatic latent image formed on the photoreceptor 12 reaches the position where the developing roll 18 of the developing device 20 is disposed, a developing bias is applied to the developing roll 18 by a developing bias power source (not shown). Then, the toner of each color held on the peripheral surface of the developing roll 18 adheres to the electrostatic latent image on the photoreceptor 12, and a toner image corresponding to the image data of the corresponding color is formed on the photoreceptor 12. .

  Further, as the rollers 30A to 30C and the backup roll 32A of the secondary transfer device 32 are rotated by a motor (not shown), the intermediate transfer belt 22 is rotated. At this time, when a primary transfer voltage is applied to the primary transfer unit 24, the toner images of the respective colors formed on the photoreceptor 12 are transferred to the intermediate transfer belt 22. In this case, by controlling the rotation of the rollers 30A to 30C and the backup roll 32A so that the transfer start positions of the toner images of the respective colors to the intermediate transfer belt 22 are matched, the toner images of the respective colors are overlapped to form image data. A corresponding toner image is formed on the intermediate transfer belt 22.

  After the toner image is transferred to the intermediate transfer belt 22, the cleaning blade 28 removes the adhering matter such as residual toner on the surface, and the charge remaining on the surface is removed by the discharge light from the discharge lamp 29. Removed.

  On the other hand, the secondary transfer device 32 includes, for example, a backup roll 32A that supports the intermediate transfer belt 22, and a secondary transfer roll 32B that sandwiches the paper P and the intermediate transfer belt 22 together with the backup roll 32A. The backup roll 32 </ b> A and the secondary transfer roll 32 </ b> B rotate following the rotation of the intermediate transfer belt 22 by sandwiching the intermediate transfer belt 22.

  Further, the paper transport roller 42 is rotated by a motor (not shown), so that the paper P in the paper storage unit 34 is transported to a gap formed by the backup roll 32A and the secondary transfer roll 32B.

  When the toner image on the intermediate transfer belt 22 is sandwiched between the backup roll 32A and the secondary transfer roll 32B, a secondary transfer voltage is applied to the backup roll 32A, and the toner formed on the intermediate transfer belt 22 is formed. The image is transferred to the paper P. Then, the paper P is conveyed to the position where the fixing device 36 is disposed, and the toner image transferred onto the paper P by the fixing device 36 is heated and melted, and the toner image is fixed on the paper P. In this manner, an image corresponding to the image data is formed on the paper P.

  On the other hand, the intermediate transfer belt 22 that has transferred the toner image onto the paper P is removed by the cleaning blade 40 to remove deposits such as residual toner adhered to the surface.

  Incidentally, the image forming apparatus 10 according to the present embodiment is equipped with a setting function for setting a secondary transfer voltage in consideration of image defects and density unevenness of the adjustment image. The secondary transfer voltage is an example of the transfer parameter of the present invention.

  With reference to FIG. 3, an adjustment image G formed on the paper P by the image forming unit 82 in order to realize the setting function will be described. As shown in FIG. 3, the adjustment image G according to the present embodiment intersects in the intersecting direction (hereinafter referred to as “perpendicular” in the present embodiment) in the transport direction of the paper P (hereinafter simply referred to as “conveyance direction”). In this example, the patch image groups PSa to PSh are formed by a plurality of (eight in the example shown in FIG. 3) patched at predetermined intervals. In the following description, when the patch image groups PSa to PSh are collectively referred to without being distinguished from each other, the alphabet (a to h) at the end of the code is omitted.

  Each patch image group PS is composed of a plurality (16 in the example shown in FIG. 3) patch images PG formed at predetermined intervals in the transport direction. Further, each patch image PG included in the patch image group PS according to the present embodiment is a rectangular image having the same color and uniform density in the same patch image group PS.

  In addition, the color of the patch image PG is different between the patch image groups PS. Specifically, for example, the patch image PG included in the patch image group PSa is a black (so-called process black) image formed using Y, M, and C toners. Further, for example, the patch image PG included in each of the patch image groups PSb to PSd is an image formed by superposing two toners of three colors of Y, M, and C. Further, for example, each patch image PG included in each of the patch image groups PSe to PSh is a single-color halftone image of each of Y, M, C, and K.

  In the present embodiment, the voltage level of the secondary transfer voltage (hereinafter, referred to as “secondary transfer voltage”) is set at a predetermined interval from one end portion (left end portion in the example shown in FIG. 3) in the crossing direction of the adjustment image G. A numerical value representing simply “voltage level” is formed on the paper P. This numerical value is a predetermined numerical interval (from the lower limit value (−5 in the example shown in FIG. 3) to the upper limit value (+10 in the example shown in FIG. 3) with the same interval as the patch images PG in the transport direction. In the example shown in FIG. 3, the value is increased by 1). This numerical value represents a voltage level, which will be described later, of the secondary transfer voltage when the patch image PG formed at the same position (that is, the same row) in the transport direction is formed on the paper P.

  In the image forming apparatus 10 according to the present embodiment, the voltage level and the image data for forming the adjustment image G shown in FIG. 3 (hereinafter referred to as “adjustment image data”) are stored in the storage unit 66 in advance. Has been.

  Next, the operation of the image forming apparatus 10 according to the present embodiment will be described with reference to FIG. FIG. 4 is a flowchart showing the flow of the voltage derivation program executed by the CPU 60. This voltage derivation processing program is, for example, when an instruction to start execution is input by the user via the operation display unit 90, or whenever an image is formed on a predetermined number (for example, 1000 sheets) of paper P. To be executed. Further, the voltage derivation processing program may be executed each time the type of paper P used is changed, for example. The voltage derivation program is preinstalled in the ROM 62. Here, in order to avoid complications, it is assumed that a counter described later is initialized to 0 (zero) at the start of execution of the voltage derivation processing program.

  In step 100 of FIG. 4, the CPU 60 reads the adjustment image data from the storage unit 66. In the next step 102, the CPU 60 controls the image forming unit 82, and based on the adjustment image data read in step 100, the numerical value representing the voltage level and the adjustment image G (see FIG. 3). Is formed on the paper P. In this formation, the CPU 60 controls the image forming unit 82 to form the adjustment image G by increasing the voltage value of the secondary transfer voltage at predetermined time intervals. As a result, the image forming unit 82 applies the secondary transfer voltage having a higher voltage value to the backup roll 32A as the patch image PG is located at the rear of the transport direction, and forms the patch image PG on the paper P.

  Specifically, in the present embodiment, the voltage level is predetermined as the secondary transfer voltage of the paper P of a predetermined type (plain paper in the present embodiment) as a voltage value of 0 (zero). The applied voltage value is applied. In this embodiment, the voltage value for forming the adjustment image G includes a voltage value with a voltage level of 0, and is predetermined within a range that is greater than or equal to the lower limit value of the secondary transfer voltage and less than or equal to the upper limit value. A voltage value of a voltage interval (in this embodiment, 100 [V] interval) is applied.

  That is, when the secondary transfer voltage when forming the patch image PG of the row with the voltage level of 0 shown in FIG. 3 is A [V], the patch image PG of the row with the voltage level of −5 is formed. The secondary transfer voltage is (A-500) [V]. Similarly, the secondary transfer voltage when forming the patch image PG of the row whose voltage level is +10 is (A + 1000) [V].

  In the present embodiment, if the determination in step 126 described later is a negative determination and the processing in this step 102 is executed for the second time or later after the execution of this voltage derivation processing program is started, the patch image is displayed. The adjustment image G is formed by changing the number of patch images PG included in the group PS and the voltage interval. Details of the second and subsequent adjustment image G forming processes will be described later.

  In the next step 104, the CPU 60 controls the image reading unit 84 to read the adjustment image G formed on the paper P in step 102, and configures each of R, G, and B with the density for each pixel. Obtain concentration data.

  In the next step 106, the CPU 60 uses the density data acquired in step 104 to derive an average density value for each pixel of each patch image PG as a value indicating the density of each patch image PG. In this step 106, the CPU 60 may derive a value indicating another density such as a median value or a mode value instead of the average density value. As an example, as shown in FIG. 5, the average value of the density for each pixel of the patch image PG corresponding to each voltage level is derived for each patch image group PS by the processing of this step 106.

  In the next step 108, the CPU 60 derives a density histogram of each patch image PG using the density data acquired in step 104. When the patch image PG is formed on the paper P without any problem, the density histogram derived in this step 108 becomes a substantially symmetrical curve as shown by a solid line L1 in FIG. 6 as an example. On the other hand, for example, when an image defect such as a white spot occurs in the patch image PG due to a discharge defect or the like caused by the secondary transfer voltage being too high, the density histogram derived in this step 108 is shown in FIG. As shown by the broken line L2, the curve is distorted compared to the solid line L1.

  In the next step 110, the CPU 60 derives a value (standard deviation in the present embodiment) representing the degree of density variation of each patch image PG from the density histogram derived in step 108. In this step 110, the CPU 60 may derive a value representing the degree of other variations such as variance instead of the standard deviation. As an example, as shown in FIG. 7, the standard deviation of the density of the patch image PG corresponding to each voltage level is derived for each patch image group PS by the processing of this step 110.

  In the next step 112, the CPU 60 derives a value representing the degree of symmetry between the lower part and the higher part of the density having the maximum frequency in the density histogram derived in step 108. Specifically, as shown in FIG. 8 as an example, the CPU 60 divides the regions in the density histogram into a region R1 having a higher density than a density N and a region R2 having a lower density than the density N at which the frequency in the density histogram is the maximum value MV. Divide into Then, the CPU 60 derives an area b / area a that divides the area b by the area a as a value representing an area ratio between the area a of the area R1 and the area b of the area R2. As an example, as shown in FIG. 9, the area ratio (area b / area a) of the patch image PG corresponding to each voltage level is derived for each patch image group PS by the processing of this step 112.

  In the present embodiment, the processing from step 106 to step 112 described above is executed using the density data of the complementary color of each patch image PG among the density data of each color of R, G, and B acquired in step 104. Is done. Specifically, as shown in FIG. 10 as an example, for the monochrome patch images PG constituting each of the patch image groups PSe to PSh, B, G, and R, which are complementary colors of Y, M, C, and K, respectively. , G density data is used.

  Further, the patch image PG formed by superimposing a plurality of colors of toner constituting each of the patch image groups PSa to PSd is a complementary color of Y, M, Y, and Y, which are the colors of the uppermost toner. This is executed using density data of B, G, B, and B.

  In the next step 114, the CPU 60 derives the secondary transfer voltage based on the average value of the density derived in step 106, the standard deviation of the density derived in step 110, and the area ratio derived in step 112. To do. With reference to FIG. 11, the secondary transfer voltage derivation process in step 114 will be described in detail.

  As an example, as shown in FIG. 11, for the voltage level corresponding to each patch image PG of each patch image group PS, an average value of density is derived by the process of step 106, and a standard deviation of density is derived by the process of step 110. Then, the area ratio is derived by the process of step 112. In FIG. 11, for example, each value derived for the patch image group PSa is shown.

  Here, for each value, the CPU 60 derives an evaluation value “1” if the value is within the predetermined allowable range, and “0” if the value is outside the allowable range. For example, regarding the average value of the density, the CPU 60 has a difference from the density of the corresponding patch image PG in the adjustment image data within a range not less than a predetermined lower limit value and not more than an upper limit value (for example, −5 or more +5 In the following range, the evaluation value is derived as “1”. Further, when the difference is out of the range, the CPU 60 derives the evaluation value as “0”.

  Further, for example, when the standard deviation of the concentration is not less than the minimum value of the derived standard deviation and within a predetermined multiple (for example, 1.25 times) of the minimum value, The evaluation value is derived as “1”. Further, when the standard deviation is out of the range, the CPU 60 derives the evaluation value as “0”.

  Further, for example, when the area ratio is within a range of a predetermined lower limit value or more and an upper limit value (for example, 0.7 or more and 1.2 or less), the CPU 60 sets the evaluation value to “1”. To derive. Further, when the area ratio is out of the range, the CPU 60 derives the evaluation value as “0”.

  Further, the CPU 60 derives the total value of the evaluation values for each voltage level. Then, the CPU 60 derives a secondary transfer voltage corresponding to a voltage level at which the total value of the evaluation values is equal to or greater than a predetermined threshold (for example, 3) as a secondary transfer voltage within the allowable range as a set value. To do.

  In the present embodiment, when the secondary transfer voltage derived for each patch image group PS by the processing of this step 114 is different, the patch image group PSa formed using the largest number of color toners. Although priority is given to the derived secondary transfer voltage, the present invention is not limited to this. For example, priority may be given to the secondary transfer voltage derived for the patch image group PS corresponding to the color of toner that is most used by the user from the past image formation history. Further, for example, a secondary transfer voltage common to the secondary transfer voltage derived for each patch image group PS may be derived as a secondary transfer voltage that is within an allowable range as a set value.

  In the next step 116, the CPU 60 displays a selection screen for allowing the user to select the voltage level of the secondary transfer voltage derived in step 114 on the display of the operation display unit 90.

  FIG. 12 shows an example of the selection screen according to the present embodiment. As shown in FIG. 12, on the selection screen according to the present embodiment, information prompting the user to select a voltage level, and information prompting re-execution when there is no voltage level with sufficient image quality for the user are displayed. . In the selection screen according to the present embodiment, a selection button, a “set” button, and a “re-execute” button each displaying a selectable voltage level are displayed. FIG. 12 shows an example in which the total value of the evaluation values in the voltage range of −2 to +6 is derived to be equal to or greater than the threshold value by the process of step 114 above.

  Here, the user visually confirms the adjustment image G formed on the paper P in step 102 based on the display content of the selection screen. The user specifies an optimum voltage level when there is an image with sufficient image quality for the user among the patch images PG corresponding to the voltage level displayed on the selection screen. Then, the user designates a “set” button after designating a selection button in which the specified voltage level is displayed on the button via the operation display unit 90. On the other hand, when the patch image PG having sufficient image quality for the user does not exist in the adjustment image G formed on the paper P in step 102, the user designates a “re-execute” button.

  Therefore, in step 118, the CPU 60 stands by until input by the user through the operation display unit 90 is performed. When the “set” button or “re-execute button” is designated by the user on the selection screen, the process proceeds to step 120.

  In step 120, the CPU 60 determines whether or not any selection button is designated by the user and a “setting” button is designated on the selection screen. If this determination is affirmative, it is considered that the voltage level has been input by the user, and the process proceeds to step 130. If the determination is negative, the “re-execute” button is designated on the selection screen. The process proceeds to step 122.

  In step 122, the CPU 60 derives a secondary transfer voltage when the next adjustment image G is formed. In the present embodiment, the CPU 60 has a voltage interval smaller than the voltage interval of the secondary transfer voltage in the immediately preceding step 102 (in this embodiment, a voltage interval that is half the voltage interval of the secondary transfer voltage in the immediately preceding step 102). The secondary transfer voltage is derived. As a result, the determination at step 126, which will be described later, becomes a negative determination, and when the adjustment image G is formed next at step 102, the number of patch images PG in each patch image group PS is doubled.

  For example, in the first step 102, when the adjustment image G is formed on the paper P with the secondary transfer voltage increased by 100 [V] from -5 to +10, the second step 102 The adjustment image G is formed on the paper P with the following secondary transfer voltage. That is, in this case, the lower limit value and the upper limit value of the secondary transfer voltage are the same as the first time, and the adjustment image G is printed on the sheet with the secondary transfer voltage increased by 50 [V] from -10 to +20. P is formed. Therefore, in this case, the number of patch images PG in each patch image group PS is 32, which is double from the initial 16 images.

  In the next step 124, the CPU 60 adds 1 to the counter. In the next step 126, the CPU 60 determines whether or not the counter is equal to or greater than a predetermined threshold (for example, 3). If this determination is negative, the process returns to step 102, whereas if an affirmative determination is made, the process proceeds to step 128.

  In step 128, the CPU 60 displays on the display of the operation display unit 90 an error notification screen that displays information or the like that prompts the user to contact the maintenance staff, and then ends the voltage derivation process.

  On the other hand, in step 130, the CPU 60 stores the secondary transfer voltage corresponding to the voltage level selected by the user on the selection screen in the storage unit 66 in association with the sheet information indicating the type of the sheet P, and then The voltage derivation process ends. The secondary transfer voltage stored for each piece of paper information in the storage unit 66 by the processing of step 130 is the secondary when an instruction to form an image on the corresponding type of paper P is input after the voltage derivation processing is completed. The transfer voltage is applied to the backup roll 32A.

[Second Embodiment]
Hereinafter, the second embodiment of the present invention will be described in detail. Note that the configuration of the image forming apparatus 10 according to the present embodiment is the same as that of the first embodiment (see FIGS. 1 and 2), and thus the description thereof is omitted here.

  In the image forming apparatus 10 according to the present embodiment, as an operation mode of the apparatus, a density priority mode in which priority is given to forming a darker image on the paper P, or an image defect such as occurrence of uneven density of the image or generation of a white spot is performed. An image quality priority mode for further reduction can be set. That is, in the image forming apparatus 10 according to the present embodiment, it is possible to set a priority indicating which of the priority is given to forming an image darker and reducing image defects. For example, the image forming apparatus 10 operates in an operation mode in accordance with information indicating an operation mode input by the user via the operation display unit 90 and stored in the storage unit 66.

  Next, the operation of the image forming apparatus 10 according to the present embodiment will be described with reference to FIG. Note that the voltage derivation process according to the present embodiment is different from the first embodiment in the process of step 114, and therefore the process of step 114 will be described here.

  In step 114 of FIG. 4, the CPU 60 calculates the secondary transfer voltage based on the average density derived in step 106, the standard deviation of density derived in step 110, and the area ratio derived in step 112. To derive. In the present embodiment, the CPU 60 performs weighting according to information indicating the operation mode stored in the storage unit 66 to derive the secondary transfer voltage. With reference to FIG. 13, the secondary transfer voltage derivation process in step 114 will be described in detail. FIG. 13 shows an example in which the density priority mode is set as the operation mode of the image forming apparatus 10. Further, the method of deriving the average value of the concentration derived in step 106, the standard deviation of the concentration derived in step 110, and the evaluation value of each value of the area ratio derived in step 112 is the first embodiment. Since it is the same as that, description here is abbreviate | omitted.

  As an example, as illustrated in FIG. 13, when the operation mode of the image forming apparatus 10 is the density priority mode, the CPU 60 weights the evaluation value of the average density value. FIG. 13 shows an example in which weighting is performed to double the evaluation value of the average density value. In the present embodiment, when the operation mode of the image forming apparatus 10 is the image quality priority mode, the CPU 60 weights the evaluation value of the standard deviation of density. When the operation mode of the image forming apparatus 10 is the image quality priority mode, the evaluation value of the area ratio may be weighted instead of the evaluation value of the density standard deviation, or the evaluation value and the area of the density standard deviation may be weighted. Both of the evaluation values of the ratio may be weighted.

  Then, as in the first embodiment, the CPU 60 is within the allowable range with the secondary transfer voltage corresponding to the voltage level at which the total value of the evaluation values is equal to or greater than a predetermined threshold as a set value. Derived as a secondary transfer voltage.

  In each of the above embodiments, the case where the secondary transfer voltage is applied as the transfer parameter has been described. However, the present invention is not limited to this. For example, a secondary transfer current may be applied as the transfer parameter. In this case, for example, as in the above-described embodiments, a mode in which the adjustment image G is formed on the paper P while increasing the secondary transfer current from the lower limit value to the upper limit value at predetermined current intervals is exemplified. .

  Further, in each of the above-described embodiments, the case where the derived secondary transfer voltage is displayed on the operation display unit 90 to be selected by the user has been described. However, the present invention is not limited to this. For example, any secondary transfer voltage among the derived secondary transfer voltages may be set. In this case, for example, a mode in which the secondary transfer voltage having the maximum density average value among the derived secondary transfer voltages is set as an example. Further, in this case, in the second embodiment, the secondary transfer voltage may be set according to the operation mode of the image forming apparatus 10. For example, when the operation mode of the image forming apparatus 10 is the image quality priority mode, a mode in which the secondary transfer voltage having the smallest standard deviation in density is set among the derived secondary transfer voltages is exemplified.

  In each of the above-described embodiments, the case where the voltage derivation processing program is preinstalled in the ROM 62 has been described. However, the present invention is not limited to this. For example, the voltage derivation processing program may be provided by being stored in a storage medium such as a CD-ROM (Compact Disk Read Only Memory) or provided via a network.

  Further, although cases have been described with the above embodiments where voltage derivation processing is realized by a software configuration using a computer by executing a program, the present invention is not limited to this. For example, the voltage derivation process may be realized by a hardware configuration or a combination of a hardware configuration and a software configuration.

  In addition, the configuration (see FIGS. 1 and 2) of the image forming apparatus 10 described in the above embodiments is merely an example, and unnecessary portions are deleted or new portions are within the scope not departing from the gist of the present invention. Needless to say, you may add.

  Further, the flow of the voltage derivation program described in each of the above embodiments (see FIG. 4) is also an example, and unnecessary steps can be deleted or new steps can be added within the scope not departing from the gist of the present invention. Needless to say, they may be added or the processing order may be changed.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 32 Secondary transfer apparatus 32A Backup roll 32B Secondary transfer roll 50 Control part 60 CPU
62 ROM
66 Storage Unit 82 Image Forming Unit 84 Image Reading Unit 90 Operation Display Unit P Paper

Claims (8)

A forming unit that forms the image on a recording medium by transferring the image in accordance with the set transfer parameters;
A control unit that controls the forming unit to form an adjustment image while changing the transfer parameter;
The density distribution of the adjustment image is derived for each transfer parameter from the read information obtained by reading the adjustment image formed on the recording medium by the control unit, and the density of the adjustment image is derived from the derived density distribution. A derivation unit for deriving a transfer parameter in which a value indicating the degree of variation is within a predetermined allowable range;
An image forming apparatus. The image formation according to claim 1, wherein the value representing the degree of density variation is a value representing a degree of symmetry between a lower part and a higher part of the density histogram representing the density distribution, which has a maximum frequency. apparatus. The image forming apparatus according to claim 1, wherein the value representing the degree of density variation is a standard deviation of the density in the density distribution. The read information includes a value indicating the density of each of a plurality of colors,
The derivation unit derives a density distribution of the adjustment image for each transfer parameter with respect to a density of a complementary color of the color of the adjustment image included in the read information, and derives the transfer parameter from the derived density distribution. The image forming apparatus according to any one of claims 1 to 3. The adjustment image includes an image formed on the recording medium by superimposing a plurality of color toners,
The derivation unit derives a density distribution of the adjustment image for each transfer parameter with respect to a density of a complementary color of the toner color formed on the uppermost layer of the recording medium included in the read information, and the derived density distribution The image forming apparatus according to claim 4, wherein the transfer parameter is derived from the image forming apparatus. The deriving unit further derives a value indicating the density of the adjustment image from the read information for each transfer parameter, the value indicating the degree of density variation is within an allowable range, and the value indicating the density is allowable. The image forming apparatus according to any one of claims 1 to 5, wherein a transfer parameter that is a range is derived. The image forming apparatus according to claim 6, wherein the deriving unit derives the transfer parameter by weighting a value indicating the degree of density variation or a value indicating the density according to a predetermined priority.   A non-transitory computer-readable storage medium storing a program for causing a computer to function as a control unit and a derivation unit of the image forming apparatus according to claim 1.