JP6519733B2 - Image forming device - Google Patents

Description

  The present invention relates to an image forming apparatus.

  In the production market, color reproduction and color stability are required because printed matter is an end product. The color reproducibility and the color stability vary depending on the installation environment of the printing machine for producing the printed matter, the frequency of use, the image density of the output image, and the like, and therefore, the color image is provided with a correction function.

  Here, in Patent Document 1, colors used in a plurality of pages of a print job are extracted, patch images of the extracted colors are formed and measured, and a color fluctuation amount from a reference value in the extracted color is measured. It is disclosed that the determination is made and the correction is made when outputting the printed matter.

JP, 2013-021467, A

  An object of the present invention is to provide an image forming apparatus that forms an image with enhanced color reproducibility and color stability from the viewpoint that the user emphasizes.

Claim 1 is
Gradation correction according to gradation correction data is performed on user image data, a first toner image corresponding to the user image data after gradation correction is formed, and the first toner image is transferred and fixed on a sheet of paper An image forming apparatus for forming an image on the sheet by
A toner image forming unit for forming a second toner image for density measurement;
A density measurement unit that measures the density value of the second toner image;
An image quality monitoring unit that monitors the image quality based on the density value obtained by the measurement of the second toner image by the density measurement unit;
And a reception unit for receiving designation of a key monitoring area on density gradation from a user,
The toner image forming unit analyzes user image data representing an image to be formed on a sheet this time, and between the two first toner images formed on a transfer area to be transferred onto the sheet. , the non-transfer area which is not transferred onto the sheet, there is to form a second toner image conforming fit image density in the specified priority monitoring area with present on the user image data,
The receiving unit further receives an instruction input of formation of one or more second toner images of a near image density near the matching image density in addition to the second toner image of the matching image density,
When the toner image forming unit receives an instruction to form a second toner image of the near image density, the second image of the near image density is formed along with the second toner image of the compatible image density in the non-transfer area. An image forming apparatus characterized by forming a toner image .

Claim 2 is
The receiving unit further receives an instruction on how many second toner images are to be formed in the non-transfer area.
The image forming apparatus according to claim 1, wherein the toner image forming unit forms the second toner image at an interval at which an instruction is received.

Claim 3 is
The toner image forming unit further forms a plurality of third toner images for density measurement in a time zone without image formation on a sheet .
The density measurement unit further measures the density of the third toner image ;
The image quality monitoring unit further adds a correction according to the density of the third toner image measured by the density measuring unit to the gradation correction data .
The color which is not included in the user image data of the plurality of third toner images at least a part of the opportunity of the toner image forming portion forming the third toner image 3. The image forming apparatus according to claim 1, wherein the remaining third toner image from which the third toner image of the image density is omitted is formed.

  According to the first aspect, an image is formed in which color reproducibility and color stability are enhanced from the viewpoint that the user emphasizes.

Further , according to claims 1 and 2 , color reproducibility and color stability according to the degree of emphasis by the user can be obtained, and when the degree of emphasis is low, the productivity of the image can be enhanced.

According to the third aspect , efficient correction processing is performed according to the image formed by the image forming apparatus.

FIG. 1 is a schematic configuration diagram of a printer as an embodiment of an image forming apparatus of the present invention. It is a figure which shows the internal structure of a control part. FIG. 7 is a diagram showing processing in a parameter setting mode for toner patch creation. It is a figure showing a priority mode selection screen. It is a figure showing the example of the user picture for priority mode explanation. It is a figure showing a gradation patch number selection screen. It is the figure which showed the patch preparation frequency selection screen. It is a figure which shows the process at the time of printing. FIG. 5 is a view showing an example of the arrangement of toner images formed on an intermediate transfer belt. FIG. 8 is a view showing another example of the arrangement of toner images formed on the intermediate transfer belt. FIG. 5 is a view showing an arrangement example of a full set of toner patches formed on an intermediate transfer belt. FIG. 6 is a view showing an arrangement example of toner patches formed on an intermediate transfer belt for every 1000 prints.

  Hereinafter, embodiments of the present invention will be described.

  FIG. 1 is a schematic block diagram of a printer as an embodiment of the image forming apparatus of the present invention.

  User image data is externally input to the printer 100, and an image based on the user image data is printed out on paper.

  A plurality of (two in this case) paper trays 150 are provided at the lower part of the printer 100, and each paper tray 150 is in a state in which the paper P before use, which is used for image printing, is stacked. It is housed. When printing an image, the sheet P is taken out one by one from the designated sheet tray of the plurality of sheet trays 150 by the sheet take-out roll 151, and the sheet conveyance roll 152 etc. Transported to

  In addition, four image forming engines 130 are mounted on the printer 100. In each of the image forming engines 130, a single color toner image is formed of single color toners of different colors for each of the image forming engines 130Y, 130M, 130C, and 130K.

  Here, with regard to the image forming engine 130, when representing the color of the toner, 'Y' (yellow), 'M' (magenta) are codes representing the color of the toner in addition to the code representing the image forming engine '130'. , 'C' (cyan), 'K' (black). For descriptions that are not related to color, the code representing the color is omitted, and is referred to as the image forming engine 130. The same applies to elements other than the image forming engine.

  In the present embodiment, all four image forming engines 130 have the same configuration. Each image forming engine 130 includes a photosensitive member 131 rotating in the direction of arrow A, and a charger 132, an exposing device 133, a developing device 134, and a cleaner 135 disposed around the photosensitive member 131.

  The charger 132 is in contact with the photosensitive member 131 and uniformly charges the surface of the photosensitive member 131.

  The exposure device 133 irradiates the photosensitive member 131 with exposure light 133 a modulated based on image data to form an electrostatic latent image on the photosensitive member 131.

  Each exposure unit 133 receives, from the control unit 200, image data representing an image of a single color formed of color toner shared by the image forming engine 130. Then, the exposure device 133 emits exposure light 133a modulated with image data representing the single-color image, and an electrostatic latent image corresponding to the image data representing the single-color image is formed on the photosensitive member 131. Be done.

  The developing device 134 includes a developing roller 134 a that carries toner in the area facing the photosensitive member 131. A developing bias is applied to the developing roller 134 a, and the electrostatic latent image formed on the photosensitive member 131 is developed with toner by the action of the developing bias, and the electrostatic latent image is formed on the photosensitive member 131. A single-color toner image is formed which consists of a toner distribution according to the potential distribution of

  Each toner cartridge 139 is provided on the top of each image forming engine 130. Each toner cartridge 139 contains a single color toner for each corresponding image forming engine 130. The toner in the toner cartridge 139 is supplied into the developing device 134 and used to form a toner image. The toner cartridge 139 is replaceable, and when it is emptied, it is replaced with a new toner cartridge 139.

  An intermediate transfer unit 160 is disposed below the image forming engine 130. The intermediate transfer unit 160 includes an endless intermediate transfer belt 161, a drive roll 162 for rotating the intermediate transfer belt 161, a tension applying roll 163 for applying tension to the intermediate transfer belt 161, and the intermediate transfer belt 161. A pressing roll 164 is pressed against the secondary transfer roll 170. The intermediate transfer belt 161 is supported by the drive roll 162, the tension applying roll 163, and the pressing roll 164, and receives rotational driving force from the drive roll 162, and moves along the four image forming engines 130. Move circularly in the direction of arrow B. Further, the intermediate transfer unit 160 is provided with four primary transfer rolls 165, a cleaner 166, and a density sensor 167.

  The four primary transfer rolls 165 are disposed at positions facing the photosensitive members 131 of the respective image forming engines 130 with the intermediate transfer belt 161 interposed therebetween, and intermediate the toner images formed on the photosensitive members 131. It plays a role of transferring onto the transfer belt 161.

  The toner images formed on the respective photosensitive members 131 of the four image forming engines 130 are sequentially superimposed on the intermediate transfer belt 161 moving in the direction of arrow B by the action of the respective primary transfer rolls 163. Transcribed.

  After the transfer of the toner image, the cleaner 135 removes the toner and the like remaining on the surface of the photosensitive member 131.

  The toner images transferred so as to sequentially overlap on the intermediate transfer belt 161 are transferred onto the sheet P conveyed at the same timing by the action of the secondary transfer roll 170. The sheet P which has received the transfer of the toner image is further conveyed on the sheet conveyance path 153 and is subjected to heating and pressure by the fixing unit 180, whereby an image consisting of the fixed toner image is printed on the sheet P. The paper is discharged from the printer 100 onto a paper discharge tray (not shown).

  On the other hand, after transferring the toner image, the intermediate transfer belt 161 removes toner and the like remaining on the surface by the cleaner 166.

  The four image forming engines 130 form not only a toner image representing an image instructed by the user for image formation, but also a toner patch for density measurement based on measurement image data generated in the printer 100. . This toner patch is an example of the second toner image according to the present invention. On the other hand, the toner image representing the image instructed to form an image by the user is an example of the first toner image in the present invention.

  The toner patch formed by the image forming engine 130 is transferred onto the intermediate transfer belt 161. The density sensor 167 is a sensor that measures the density of the toner patch by irradiating the toner patch with light, receiving the reflected light, and receiving the reflected light. The toner patch after the measurement is removed from the intermediate transfer belt 161 by the cleaner 166. The measured density of the toner patch is adjusted for the potential adjustment of the developing bias applied to the developing roller 134a and the tone correction LUT (look-up table) so that a high quality image is always formed by the printer 100. This is reflected in the adjustment etc. of FIG. This LUT corresponds to an example of gradation correction data according to the present invention.

  The printer 100 shown in FIG. 1 further includes a control unit 190 and a UI (user interface) 200. The control unit 190 is responsible for controlling the operation of the printer 100 in cooperation with the above-described units. The control unit also has the above-described LUT (look-up table), and also plays a role in adjusting the image quality of the printer 100, such as correcting the gradation of the input user image data. The user image data after tone correction is sent to the exposure unit 133, and the exposure unit 133 outputs exposure light 133a modulated based on the user image data after correction, and the exposure light 133a is irradiated to the photosensitive member 131, An electrostatic latent image is formed on the body 131.

  Further, the UI 200 includes a touch panel display screen 210, and has a role of displaying various operation screens and receiving an operation by the user. In the printer 100, processing corresponding to the operation by the user on the operation screen is executed.

  FIG. 2 is a diagram showing an internal configuration of the control unit.

  The control unit 190 is responsible for control of each unit of the printer 100 shown in FIG. 1 and control of communication with an external device. The control unit 190 includes a timing generator 191, a memory 192, a pattern generator 193, a LUT storage unit 194, and a control unit 195.

  The timing generator 191 generates a timing signal which determines the operation timing of each part constituting the printer 100.

  The memory 192 stores various programs and data for operating the printer 100.

  The pattern generator 193 forms various patterns such as halftone dot patterns at the time of image formation and patterns of toner patches.

  The LUT storage unit 194 is a storage unit that stores a tone correction LUT.

  The control unit 195 communicates with the inside and outside of the control unit 190 to control the operation and the like of each unit of the printer 100.

  FIG. 3 is a diagram showing processing in a parameter setting mode for toner patch creation. The process shown in FIG. 3 corresponds to an example of the receiving unit according to the present invention.

  When the user enters the parameter setting mode by operating the UI 200 shown in FIG. 1, the process shown in FIG. 3 is started.

  Here, first, the "priority mode selection screen" is displayed (step S101).

  FIG. 4 is a diagram showing a priority mode selection screen.

  Here, four types of priority modes are displayed: “Omakase”, “highlight emphasis”, “solid image emphasis”, and “text emphasis”. The default is "OK". When one of these four types is selected and the “OK” button is pressed, the priority mode is selected.

  FIG. 5 is a diagram showing an example of a user image for explaining the priority mode.

  The user image 10 is composed of a background portion 11, a light-colored area 12, a dark-colored area 13, and characters 14. The background portion 11 has the largest area, and is an intermediate-dark area between the light-colored area 12 and the dark-colored area 13. Specifically, the background portion 11 is (C25% / M5% / Y20% / K0%). Moreover, the light colored area 12 is (C10% / M0% / Y10% / K0%). Furthermore, the dark area 13 is (C0% / M85% / Y85% / K0%). Furthermore, the character 14 is (C0% / M0% / Y0% / K100%).

  Here, the user image data representing the user image 10 shown in FIG. 5 is an object (partial image) of one background portion 11, one light color region 12, one dark color region 13 and one character 14 The entire user image 10 is represented by the four objects in total.

  One of the priority modes shown in FIG. 4 is a mode in which user image data is analyzed to form toner patches of high appearance frequency and image density.

  In the case of the user image 10 shown in FIG. 5, the appearance frequency is the highest since the background portion 11 has the largest area, and the toner patch of the color of the background portion 11 and the image density, that is, the C25% toner patch and the M5% toner Three toner patches consisting of a patch and a Y20% toner patch will be formed.

  Also, “highlight emphasis” shown in FIG. 4 is a mode in which user image data is analyzed to form toner patches of the color and the image density of the portion with a low image density (less than 30% of the image density).

  In the case of the user image 10 shown in FIG. 5, two toner patches consisting of a toner patch having the color of the light colored area 12 and the image density, that is, a C10% toner patch and a Y10% toner patch are formed. It will be.

  Further, “focus on solid image” shown in FIG. 4 is a mode in which user image data is analyzed to form toner patches of color and image density of a portion with high image density (image density of 80% or more).

  In the case of the user image 10 shown in FIG. 5, since the character 14 is composed of another object, a portion having a high image density is selected among the characters 14 except for it. That is, here, a toner patch having the color of the dark area 13 and the image density, that is, two toner patches consisting of a M85% toner patch and a Y85% toner patch, is formed. In the case where the user image 10 shown in FIG. 5 is configured of one object including the character 14, the character 14 is also treated as a part of the image. It is selected to form a K100% toner patch.

  Further, “emphasis on characters” shown in FIG. 4 is a mode in which toner patches of the color and the image density of the object of the characters are formed when the objects of the characters are independent.

  In the case of the user image 10 shown in FIG. 5, a K100% toner patch representing the character 14 is formed. When the object is not divided, a toner patch of the color and the image density of the portion having the highest image density in the user image is formed. That is, in this case, toner patches of the same color and the same image density are formed in the "solid image emphasis" mode and the "character emphasis" mode.

  The toner patch of the color and the image density extracted according to the mode selected on the "Priority mode selection screen" shown in FIG. 4 based on the analysis result of the user image data is referred to herein as the "compatible image density" toner patch. .

  When the selection on the priority mode selection screen shown in FIG. 4 is completed (FIG. 3, step S102), next, a "gradation patch number selection screen" is displayed (step S103).

  FIG. 6 is a diagram showing a gradation patch number selection screen.

  Here, there are three options, “one type”, “two types”, and “three types”. The default is "1 type".

  “One kind” is a mode in which only the toner patch of “adaptive image density” described above is created.

  “Two types” is, in addition to the “compatible image density” toner patch, for each one of the “compatible image density” toner patches described above, the same color as the color of the “compatible image density” toner patch This is a mode for forming a "first neighboring image density" toner patch whose image density is 5% lower than that "suitable image density" toner patch.

  Furthermore, “three types” is, in addition to the “compatible image density” toner patch, for each one of the “compatible image density” toner patches described above, the same as the color of the “compatible image density” toner patch A first first image density toner patch whose color density is 5% lower than that of the "compatible image density" toner patch and an image density more than that of the "compatible image density" toner patch Is a mode for forming a toner patch of “second neighboring image density”, which is 5% higher.

  When one of “1 type”, “2 types”, and “3 types” is selected on the “tone patch number selection screen” shown in FIG. 6 and the “OK” button is pressed, the mode (FIG. 3, step S104).

  Next, the “patch creation frequency selection screen” is displayed (step S105).

  FIG. 7 is a diagram showing a patch creation frequency selection screen.

  There are four options here: "all pages", "every other page", "every other page", and "every other page". The default is "all pages".

  "All pages" is a mode in which toner patches of "adaptive image density" are formed on all non-transferred areas not transferred onto a sheet between two toner images based on user image data. In this mode, the formation of toner patches of "nearby image density" ("first near image density" or both "first near image density" and "second near image density") is specified If there is a “near image density” (“first near image density” or “first near image density”) and “second All of the toner patches (both near image density) are formed.

  “Every other page” is a combination of toner patches of “adaptive image density” and toner patches of “nearby image density” when “nearby image density” toner patch formation is selected. In this mode, two adjacent non-transfer areas are formed in a dispersed manner. If there is only one toner patch to be formed (only one toner patch with "compatible image density" and no "toner patch with" near image density "), then the non-transfer area and toner that will form the toner patch Non-transfer areas which do not form a patch will be alternately arranged.

  The same applies to "every two pages" and "every three pages", and in this mode, toner patches combined in all are formed to be dispersed in three continuous non-transfer areas and four continuous non-transfer areas. .

  On the "Patch creation frequency selection screen" shown in FIG. 7, one of the modes "All pages", "every other page", "every two pages", and "every three pages" is selected and When the "OK" button is pressed, the mode is set (FIG. 3, step S105), and the parameter setting mode shown in FIG. 3 ends.

  Next, processing at the time of printing will be described.

  FIG. 8 is a diagram showing processing at the time of printing.

  When user image data is input to printer 100 shown in FIG. 1 and printing of an image based on the user image data is instructed, the print process shown in FIG. 8 is started.

  Here, first, a color histogram is created for the input user image data (step S201). Here, when there is a plurality of user image data representing a plurality of types of images, a color histogram is created when all of the plurality of user image data are summed.

  Here, a color histogram refers to a histogram created by voting each pixel constituting an image to each point on a color space. Specifically, for example, the luminances of the red component (R), the green component (G), and the blue component (B) of an image are each expressed in four steps (2 bits), and the combinations of R, G and B ( If R, G, B) are counted as one color, 64 colors represented by 6 bits will exist. Therefore, a color histogram representing the distribution of the number of pixels for each color is created by fitting each pixel of the image for histogram creation to any of the 64 colors according to the color of the pixel.

  After the color histogram is created, the frequently used color is identified from the color histogram, and the identified color is subjected to color separation into CMYK, whereby the image density of each of the CMYK is identified.

  The color and the image density of the toner patch are determined by comparing the analysis result of the user image data with the contents set in the parameter setting mode described with reference to FIGS. 3 to 7 (step S202). Toner patches of the color and image density determined in this step are created in the non-transfer area between toner images created based on user image data, as described above for "compatible image density" or "near image density" Toner patch.

  Next, toner patches to be formed every 1000 sheets of the user image are determined (step S203).

  In the printer 100, the density of the toner patch is measured by the density sensor 167 (see FIG. 1). The measured density of the toner patch is reflected in the adjustment of the developing bias potential applied to the developing roller 134a and the adjustment of the LUT (look-up table) (see FIG. 2) for gradation correction. Adjustment image data representing a full set of toner patches for this adjustment is set in advance in the printer 100. The toner patch formed in step 219 described later is this full set of toner patches. In the printer 100, when the number of sheets to be printed out in one job is large, the printing process is interrupted every 1000 sheets, and toner patches are created based on the adjustment image data. The toner patch created at this time is not the full set toner patch formed in step 219 described later, but the user image data out of the full set toner patch based on the analysis result in step S201. Toner patches representing colors and image density that are unused or infrequently used (for example, less than 5% in area ratio of the image) (ie toner patches of that color, image density close to the image density Toner patch) is the remaining toner patch. In this way, by omitting toner patches representing unused or infrequently used colors and image densities, the time from the formation of toner patches to the end of adjustment is reduced. That is, this shortens the interruption time for every 1000 prints and improves the productivity of the prints.

  When the analysis of the user image data (step S201), the determination of the toner patch to be formed in the non-transfer area between the images based thereon (step S202) and the determination of the toner patch to be formed every 1000 copies (step S203) are completed. Then, the actual printing operation is disclosed.

  Here, first, the sheet counter for counting the number of printed sheets is cleared to zero (step S204), and then it is determined whether all print output in the current job is completed (step S205).

  If the current job has not ended, the sheet number counter is incremented by one (step S206), and a toner image is formed (step S207). The formation of a toner image here includes the formation of a toner image based on user image data and the formation of a toner patch on a non-transfer area immediately following the toner image.

  FIG. 9 is a view showing an example of the arrangement of toner images formed on the intermediate transfer belt.

  Here, two toner images 20 formed on the intermediate transfer belt 161 based on user image data and three toner patches 21 formed in respective non-transfer areas subsequent to the toner images 20 are shown. ing.

  Here, the three toner patches 21 are composed of a toner patch 21C of C color, a toner patch 21M of M color, and a toner patch 21Y of Y color.

  Here, “one type” is selected on the “gradation patch number selection screen” shown in FIG. 6, and therefore all three toner patches 21C, 21M and 21Y have the above-mentioned “conforming image density”. Toner patch. Furthermore, here, "All pages" is selected on the "Patch creation frequency selection screen" shown in FIG. 7, and a total number (three here) of toner patches 21C, 21M, 21Y is formed.

  The intermediate transfer belt 161 moves in the direction of arrow B (see arrow B shown in FIG. 1), and the density of each toner patch 21C, 21M, 21Y is read by the density sensor 167.

  FIG. 10 is a view showing another example of the arrangement of toner images formed on the intermediate transfer belt.

  Here, two toner images 20 formed on the intermediate transfer belt 161 based on user image data are formed. Further, in the non-transfer area following the toner image 20 in the forward direction (left side in the drawing) of the two toner images 20 as indicated by the arrow B, two C toner patches 21C and 22C and an M color 2 Two toner patches 21M and 22M are formed. Furthermore, two toner patches 21Y and 22Y of Y color are formed in a non-transfer area following the toner image 20 on the rear side (right side in the drawing) of the two toner images 20 in the direction of travel. Of the six toner patches 21C, 22C, 21M, 22M, 21Y, and 22Y in total, one toner patch for each color, that is, three toner patches 21C, 21M, and 21Y in total have the above-mentioned "compatible image density". It is a toner patch. On the other hand, the remaining three toner patches 22C, 22M, 22Y have the “first neighboring image density” in which the image density is 5% lower than that of the “compatible image density” toner patches 21C, 21M, 21Y of the same color. It is a toner patch.

  That is, in FIG. 10, “two types” is selected on the “gradation patch number selection screen” shown in FIG. 6, and “every other page” is selected on the “patch creation frequency selection screen” shown in FIG. The case is illustrated.

  The intermediate transfer belt 161 moves in the direction of the arrow B, and the density of each toner patch 21C, 22C, 21M, 22M, 21Y, 22Y is read by the density sensor 167.

  Returning to FIG. 8, the description will be continued.

  In step S207, a toner image as shown in FIG. 9 or 10 is formed, and the density of the toner patch formed in the non-transferred area of the toner image is measured by the density sensor 167 (step S208). On the other hand, the toner image 20 based on the user image data is printed and output on the sheet by being transferred and fixed on the sheet (step S209). The toner patch is not transferred onto the sheet, but is removed from the intermediate transfer belt 161 by the cleaner 166 (see FIG. 1).

  In the next step S210, it is determined whether the density measurement result of the toner patch does not exceed the threshold. In the printer 100, the upper limit threshold and the lower limit threshold based on the density of the toner patch of the same color and the same image density initially formed for each toner patch of each color and each image density in the present job However, each toner patch of the same color and the same image density is set. In step S210, it is determined whether the density of the toner patch measured this time is within a range between the upper limit threshold and the lower limit threshold or is out of the range.

Here, although relative density fluctuation is determined with reference to the density of the toner patch formed first, it has an absolute reference value, and the upper limit threshold when the absolute reference is used. It may be determined whether or not it is within the concentration range between the lower threshold and the lower threshold.

  Here, as a result of the determination, when it is determined that the value is within the range between the upper limit threshold and the lower limit threshold (step S211), the density measurement result of the toner patch is reflected in the gradation correction LUT or the like. (Step S212).

  On the other hand, when it is determined that it is out of the range (step S211), a warning is displayed on the display screen 210 (see FIG. 1) of the UI 200 in the present embodiment (step S213). Then, at this time, the measured value of the density of the toner patch this time is not reflected in the correction of the LUT or the like. This is because there is a possibility that an incorrect concentration measurement value is obtained due to noise or the like.

  Here, when the density measurement result of the toner patch is out of the range between the upper limit threshold and the lower limit threshold, the warning display on the display screen 210 is completed, but, for example, the printing operation It may be stopped or the printing operation may be interrupted to perform correction processing with a full set of toner patches. Alternatively, the number of times the density measurement result deviates from the range may be counted, and depending on the count value, a multi-step treatment such as mere warning display or stop of the printing operation may be performed.

  In step S214, it is determined whether the count value of the sheet number counter counted up in step S206 has reached 1000 or not. If it has not reached 1000, the process returns to step S205, and if the job is not completed, the above-described printing operation is repeated.

  If it is determined in step S214 that 1000 has been reached, the printing operation is temporarily suspended to form a toner patch every 1000 prints (step S215), density measurement is performed (step S216), and density measurement is performed. The result is reflected on the correction (step S217). After that, the process returns to step S204, and the sheet number counter is cleared to zero. Thereafter, the printing operation described above is continued.

  If it is determined in step S205 that the printing operation of the current job is all finished, it is determined whether the threshold for forming a full set of toner patches has been exceeded (step S218). This threshold is composed of a plurality of thresholds such as a threshold for the number of prints after the formation of a full set of toner patches, and a threshold for temperature / humidity change. If it is determined in step S218 that any one of these threshold values is exceeded, a full set of toner patches is formed (step S219), density measurement is performed (step S220), and density measurement is performed. The result is reflected on the correction (step S221), and the printing process shown in FIG. 8 ends. If it is determined in step S218 that the determination result shows that neither of the threshold values has been exceeded, the printing process shown in FIG. 8 is ended without forming the toner patch.

  FIG. 11 is a view showing an arrangement example of a full set of toner patches formed on the intermediate transfer belt. Here, although the full set is used, four toner patches 31K, 32K, 33K, 34K; 31C, 32C, 33C, 34C; 31M, 32M, 31C, 32C, 34C; 33M, 34M; 31Y, 32Y, 33Y, 34Y are shown.

  The formation of the full set toner patch, the measurement of the density, the adjustment of the LUT, etc. are performed not only at the end of the job but also, for example, when the printer 100 is powered on or after a while. It is also executed at predetermined timings such as the start of a new job.

  FIG. 12 is a view showing an arrangement example of toner patches formed on an intermediate transfer belt for every 1000 prints.

  As described above, in the case of toner patches formed for every 1000 prints, among toner patches based on adjustment image data set in advance, colors and images which are not used or used less frequently in user image data of the job It is not created for toner patches that represent density.

  In the example shown in FIG. 12, six toner patches 31K, 32K, 31C, 31M, 34M and 34Y of the full set of toner patches shown in FIG. 11 are omitted, and the remaining ten toner patches 33K, 34K, 32C, 32C, 34C, 32M, 33M, 31Y, 32Y, 33Y are formed. By omitting unused or infrequently used toner patches, the time for interrupting the printing operation can be shortened.

  Here, a so-called tandem-type color printer shown in FIG. 1 has been described as an example, but the present invention is not limited to the tandem-type, and may be applied to, for example, a rotary-type color printer and a monochrome printer. it can.

DESCRIPTION OF SYMBOLS 10 user image 11 background part 12 color light area 13 color dark area 14 characters 21, 21 C, 21 M, 21 Y toner patch 22, 22 C, 22 M, 22 Y toner patch 31 K, 32 K, 33 K, 34 K, ... , 31Y, 32Y, 33Y, 34Y toner patch 100 printer 130 image forming engine 131 photoreceptor 150 sheet tray 161 intermediate transfer belt 167 density sensor 190 control unit 200 control unit 210 display screen

Claims (3)

Gradation correction according to gradation correction data is performed on user image data, a first toner image corresponding to the user image data after gradation correction is formed, and the first toner image is transferred and fixed on a sheet of paper An image forming apparatus for forming an image on the sheet by
A toner image forming unit for forming a second toner image for density measurement;
A density measurement unit that measures the density value of the second toner image;
An image quality monitoring unit that monitors the image quality based on the density value obtained by the measurement of the second toner image by the density measurement unit;
And a reception unit for receiving designation of a key monitoring area on density gradation from a user,
The toner image forming unit analyzes user image data representing an image to be formed on a sheet this time, and between the two first toner images formed on a transfer area to be transferred onto the sheet. Forming a second toner image of a compatible image density, which is present on the user image data and conforms to a designated emphasis monitoring area, in a non-transferred area not transferred onto a sheet of paper;
The receiving unit further receives an instruction input of formation of one or more second toner images of a near image density near the matching image density in addition to the second toner image of the matching image density,
When the toner image forming unit receives an instruction to form a second toner image of the near image density, the second image of the near image density is formed along with the second toner image of the compatible image density in the non-transfer area. An image forming apparatus characterized by forming a toner image. The receiving unit further receives an instruction on how many second toner images are to be formed in the non-transfer area.
The image forming apparatus according to claim 1, wherein the toner image forming unit forms the second toner image at intervals according to an instruction. The toner image forming unit further forms a plurality of third toner images for density measurement in a time zone without image formation on a sheet .
The density measurement unit further measures the density of the third toner image ;
The image quality monitoring unit further adds a correction according to the density of the third toner image measured by the density measuring unit to the gradation correction data .
The color which is not included in the user image data of the plurality of third toner images at least a part of the opportunity of the toner image forming portion forming the third toner image The image forming apparatus according to claim 1 or 2, wherein the remaining third toner image from which the third toner image of the image density is omitted is formed.