JP4892953B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, or a facsimile, and more particularly to an image forming apparatus having a function of correcting the density of an image to be formed.

  Conventionally known image forming apparatuses include a photosensitive drum, a charging device, an exposure device, a developing device, a transfer device, and the like. In such an image forming apparatus, the rotating photosensitive drum is uniformly charged by a charging device, and the surface of the charged photosensitive drum is selectively exposed by an exposure device, whereby an electrostatic latent image is formed on the photosensitive drum. Form an image. The electrostatic latent image formed on the photosensitive drum is developed by a developing device to be a visible image, and the obtained toner image is transferred to a recording material by a transfer device.

  In this type of image forming apparatus, the obtained image quality is likely to be affected by fluctuations in the environment (temperature and humidity), aging of parts, and the like. Therefore, density deviation control (process control) is indispensable for suppressing deviation (density deviation) between the density of the toner image to be formed and the density of the toner image actually formed.

  Therefore, there is a technique for forming a predetermined image quality adjustment toner image (reference toner image) on an image carrier (for example, a photosensitive drum) and correcting the image forming conditions based on the density measurement result of the formed reference toner image. Widely used (see, for example, Patent Document 1). Further, from the viewpoint of suppressing productivity reduction due to density correction, the reference toner image is formed in an inter-image region provided between image regions where an image toner image for transfer onto a recording material is formed. There is also a technique (see, for example, Patent Document 2). Further, for the purpose of increasing the number of patch images that can be formed in the inter-image area, there is a technique in which the reference toner image is composed of a plurality of patch images and the size of each patch image is reduced (see, for example, Patent Document 3). ).

JP-A-6-102734 (page 6-9, FIG. 9) Japanese Patent Laid-Open No. 5-313454 (page 6, FIG. 3) Japanese Patent Laying-Open No. 2003-186257 (page 4-5, FIG. 2)

  Here, for example, in Patent Document 3, each color (yellow, magenta, cyan, and black) has a plurality of densities (60% and 20% image density) as a reference toner image in each inter-image region. The patch image is formed. That is, in Patent Document 3, the contents of the reference toner image formed in each inter image area are set to be the same. For the density other than the reference toner image, a method is employed in which complementation is performed based on the data obtained by measuring the density of these reference toner images.

However, when the method described in Patent Document 3 is adopted, there is a possibility that sufficient correction may not be performed for a toner image having a density that is not created as a reference toner image. In particular, when the relationship between the image forming conditions and the obtained toner density is non-linear, the correction accuracy tends to decrease, and as a result, density deviation tends to occur.
In order to solve such a problem, it is conceivable to further increase the number of image patches formed in the inter-image area by using the technique described in Patent Document 3. However, since the size of the inter image area is limited, there is a limit to the number of image patches that can be formed in one inter image area even if the size of the image patch is reduced.

  In addition, when the method described in Patent Document 3 is adopted, for example, when forming an image toner image using two colors of magenta and black, in addition to magenta and black reference toner images, reference toners of yellow and cyan are used. An image is also formed. As a result, there is a problem in that the amount of toner that is wasted is increased.

The present invention has been made to solve such a technical problem, and an object of the present invention is to appropriately set the content of an image for image quality adjustment, thereby forming a density for forming an image for image. It is to suppress the deviation.
Another object is to suppress wasteful toner consumption when forming an image quality adjustment image used for density deviation correction or the like.

  For this purpose, an image forming apparatus to which the present invention is applied forms an image for image on an image carrier and forms an image for image quality adjustment in an area where no image for image is formed on the image carrier. An image forming unit that determines the content of the image for image quality adjustment using the input image data, and the image quality that is determined by the determining unit and formed on the image carrier by the image forming unit The image processing apparatus includes a reading unit that reads an adjustment image, and an adjustment unit that adjusts image forming conditions of the image forming unit when an image for image is formed based on image data based on a reading result of the reading unit.

  Here, the image quality adjustment image includes a plurality of patch images, and the determination unit determines a combination of at least one of the color and density of the plurality of patch images as the content of the image quality adjustment image. Can do. And a change unit that increases the size of the image quality adjustment image formed by the image forming unit when at least one of the density and color of the image quality adjustment image read by the reading unit deviates from a predetermined range. be able to. Further, the determination unit determines the content of the image quality adjustment image corresponding to the image data before starting the formation of the image image based on the image data, and the adjustment unit starts forming the image image based on the image data. The adjustment of the image forming conditions of the image forming unit may be completed before the image forming unit. Furthermore, the image forming unit can form a plurality of image quality adjustment images corresponding to a plurality of image data between the image image and another adjacent image image.

  From another viewpoint, the image forming apparatus to which the present invention is applied detects an image forming unit that forms an image on the image carrier and at least one of density and color of the image formed on the image carrier. A detection unit that performs adjustment, an adjustment unit that adjusts an image forming condition in the image forming unit based on a detection result detected by the detection unit, and a determination unit that determines the content of an image for adjusting image quality using input image data The image forming unit forms an image for adjusting the image quality whose contents are determined by the determining unit, and adjusts the image forming conditions of the image forming unit by the adjusting unit based on the density / color detection result of the image for adjusting the image quality by the detecting unit. And a control unit that causes the image forming unit that has completed the adjustment of the image forming conditions to form an image for image using the image data.

  Here, the control unit repeats the formation of the image quality adjustment image by the image forming unit and the adjustment of the image forming conditions by the adjustment unit for one image data, and then forms the image for the image based on the image data. It is possible to execute the following. Further, when determining the content of the image for adjusting the image quality, the determination unit compares the areas of the image data of each color obtained by separating the image data for each color, and increases the priority of the color having a large area. Can be characterized. Further, when determining the content of the image quality adjustment image, the determination unit acquires the distribution of at least one of the density and color of the image data of each color obtained by separating the image data for each color, and the frequency in the distribution is It can be characterized by increasing the priority of at least one of high density and color.

  Further, from another viewpoint, the image forming apparatus to which the present invention is applied forms an image for image on the image carrier, and is used for image quality adjustment in an area where the image for image on the image carrier is not formed. An image forming unit that forms an image, a detection unit that detects at least one of the density and color of the image for image quality adjustment formed on the image carrier, and a predetermined detection result detected by the detection unit And a changing unit that increases the size of the image for adjusting the image quality formed by the image forming unit when deviating from the range.

  According to the present invention, since the content of the image quality adjustment image is determined using the input image data, the content of the image quality adjustment image can be appropriately set, and the image image is formed. Can be suppressed.

The best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a diagram showing an outline of an image forming apparatus according to the present embodiment. The image forming apparatus includes, for example, a plurality of (four in the present embodiment) image forming units 10 (specifically, 10Y (yellow), 10M (magenta)) on which each color component toner image is formed by electrophotography. 10C (cyan), 10K (black)). In addition, the image forming apparatus includes an intermediate transfer belt 20 that sequentially transfers (primary transfer) and holds each color component toner image formed by each image forming unit 10. The image forming apparatus further includes a secondary transfer device 30 that collectively transfers (secondary transfer) the superimposed image transferred to the intermediate transfer belt 20 onto the paper P. Furthermore, the image forming apparatus includes a fixing device 50 that fixes the second-transferred image on the paper P.

  Each image forming unit 10 (10Y, 10M, 10C, 10K) as an image forming unit has the same configuration except for the color of the toner used. Therefore, the yellow image forming unit 10Y will be described as an example. The yellow image forming unit 10Y includes a photosensitive drum 11 that has a photosensitive layer (not shown) and is rotatably arranged in an arrow A direction. Around the photosensitive drum 11, a charging roll 12, an exposure unit 13, a developing device 14, a primary transfer roll 15, and a drum cleaner 16 are disposed. Among these, the charging roll 12 is rotatably disposed in contact with the photosensitive drum 11 and charges the photosensitive drum 11 to a predetermined potential. The exposure unit 13 writes an electrostatic latent image on the photosensitive drum 11 charged to a predetermined potential by the charging roll 12 with the laser beam Bm. The developing device 14 stores corresponding color component toner (yellow toner in the yellow image forming unit 10Y), and develops the electrostatic latent image on the photosensitive drum 11 with this toner. The primary transfer roll 15 primarily transfers the toner image formed on the photosensitive drum 11 to the intermediate transfer belt 20. The drum cleaner 16 removes residues (toner and the like) on the photosensitive drum 11 after the primary transfer.

The intermediate transfer belt 20 as an image carrier is stretched and supported rotatably on a plurality of (five in the present embodiment) support rolls. Of these support rolls, the drive roll 21 stretches the intermediate transfer belt 20 and drives the intermediate transfer belt 20 to rotate. Further, the driven rolls 22 and 25 are stretched by the intermediate transfer belt 20 and rotated by the intermediate transfer belt 20 driven by the drive roll 21. The correction roll 23 is a steering roll that stretches the intermediate transfer belt 20 and restricts meandering in a direction substantially orthogonal to the conveyance direction of the intermediate transfer belt 20 (is disposed so as to be tiltable about one end in the axial direction). Function. Further, the backup roll 24 stretches the intermediate transfer belt 20 and functions as a constituent member of the secondary transfer device 30 described later.
Further, a belt cleaner 26 for removing residues (toner and the like) on the intermediate transfer belt 20 after the secondary transfer is disposed at a portion facing the drive roll 21 with the intermediate transfer belt 20 interposed therebetween. A density sensor 27 is disposed opposite to the intermediate transfer belt 20. A density sensor 27 serving as a reading unit or a detection unit is disposed adjacent to the black image forming unit 10K, and detects the density of each color toner image primarily transferred onto the intermediate transfer belt 20. .

  The secondary transfer device 30 includes a secondary transfer roll 31 disposed in pressure contact with the toner image carrying surface side of the intermediate transfer belt 20 and a counter electrode of the secondary transfer roll 31 disposed on the back surface side of the intermediate transfer belt 20. And a backup roll 24. A power supply roll 32 for applying a secondary transfer bias having the same polarity as the toner charging polarity is disposed in contact with the backup roll 24. On the other hand, the secondary transfer roll 31 is grounded.

  The paper transport system includes a paper tray 40, a transport roll 41, a registration roll 42, a transport belt 43, and a discharge roll 44. In the paper transport system, after the paper P stacked on the paper tray 40 is transported by the transport roll 41, the paper P is temporarily stopped by the registration roll 42 and then moved to the secondary transfer position of the secondary transfer device 30 at a predetermined timing. Send in. Further, the sheet P after the secondary transfer is conveyed to the fixing device 50 via the conveying belt 43, and the sheet P discharged from the fixing device 50 is sent out to the outside by the discharge roll 44.

  Next, a basic image forming process of the image forming apparatus will be described. Now, when a start switch (not shown) is turned on, a predetermined image forming process is executed. More specifically, for example, when the image forming apparatus is configured as a printer, digital image signals input from the outside such as a PC (personal computer) are temporarily stored in a memory. Then, toner images of each color are formed based on the digital image signals of four colors (Y, M, C, K) stored in the memory. That is, each image forming unit 10 (specifically, 10Y, 10M, 10C, and 10K) is driven according to the digital image signal of each color. Next, in each image forming unit 10, an electrostatic latent image is formed by irradiating the photosensitive drum 11 uniformly charged by the charging roll 12 with the laser beam Bm corresponding to the digital image signal by the exposure unit 13. Form. Then, the electrostatic latent image formed on the photosensitive drum 11 is developed by the developing device 14 to form toner images of each color. When the image forming apparatus is configured as a copying machine, a document set on a document table (not shown) is read by a scanner, and the obtained read signal is converted into a digital image signal by a processing circuit. Thus, the toner images of the respective colors may be formed.

  Thereafter, the toner images formed on the respective photosensitive drums 11 are sequentially primary-transferred to the surface of the intermediate transfer belt 20 by the primary transfer roll 15 at a primary transfer position where the photosensitive drum 11 and the intermediate transfer belt 20 are in contact with each other. . On the other hand, the toner remaining on the photosensitive drum 11 after the primary transfer is cleaned by the drum cleaner 16.

  The toner image primarily transferred to the intermediate transfer belt 20 in this way is superimposed on the intermediate transfer belt 20 and conveyed to the secondary transfer position as the intermediate transfer belt 20 rotates. On the other hand, the paper P is conveyed to the secondary transfer position at a predetermined timing, and the secondary transfer roll 31 nips the paper P with respect to the backup roll 24.

  Then, at the secondary transfer position, the toner image carried on the intermediate transfer belt 20 is secondarily transferred to the paper P by the action of a transfer electric field formed between the secondary transfer roll 31 and the backup roll 24. . The sheet P on which the toner image is transferred is conveyed to the fixing device 50 by the conveyance belt 43. In the fixing device 50, the toner image on the paper P is heated and pressure-fixed, and then sent out to a paper discharge tray (not shown) provided outside the apparatus. On the other hand, the toner remaining on the intermediate transfer belt 20 after the secondary transfer is cleaned by the belt cleaner 26.

  As described above, each of the image forming units 10Y, 10M, 10C, and 10K forms a corresponding color component toner image by electrophotography, and primarily transfers the formed color component toner image to the intermediate transfer belt 20. . In the tandem type image forming apparatus, since the respective photosensitive drums 11, the charging rolls 12, and the primary transfer rolls 15 are used, the degree of deterioration differs for each color. That is, the thickness of the photosensitive layer provided on the photosensitive drum 11 and the resistance values of the charging roll 12 and the primary transfer roll 15 are different for each image forming unit 10. Also, the charging characteristics of the toner for each color are different. For this reason, even if the corresponding color component toner images are formed by the image forming units 10Y, 10M, 10C, and 10K to form images of the same density for each color and are primarily transferred onto the intermediate transfer belt 20, the The image density of each color component toner formed on the transfer belt 20 is not actually the same.

  Therefore, in the present embodiment, the image quality adjustment toner images created by the image forming units 10Y, 10M, 10C, and 10K are transferred onto the intermediate transfer belt 20, and the image quality adjustment of each color transferred onto the intermediate transfer belt 20 is performed. The toner image is read by the density sensor 27, and the density adjustment (process control) of each color component toner image is performed based on the obtained reading result. Then, after the density adjustment is performed, an actual image toner image is formed. The details of the process control in the present embodiment will be described below.

  First, the formation position of the image quality adjusting toner image will be described. FIG. 2 is a development view of the intermediate transfer belt 20. In the present embodiment, eight sheets of images can be formed on the outer peripheral surface of the intermediate transfer belt 20 in the case of A4 size paper P (A4LEF), for example. Here, an area on the intermediate transfer belt 20 corresponding to one sheet of paper P is referred to as a panel Pa. Therefore, in the case of A4LEF, eight panels Pa1 to Pa8 exist on the peripheral surface of the intermediate transfer belt 20. An area corresponding to the panel Pa with respect to the traveling direction of the intermediate transfer belt 20 is referred to as an image area S1, and an area between the image area S1 and the next image area S1 is referred to as an inter image area S2. In the present embodiment, an image toner image G1 is formed in the image area S1, and an image quality adjustment toner image G2 is formed in the inter-image area S2. Here, the image toner image G1 is secondarily transferred onto the paper P by the secondary transfer device 30, but the image quality adjusting toner image G2 is not secondarily transferred onto the paper P and is removed by the belt cleaner 26 as it is. Is done.

FIG. 3 is a block diagram showing a signal processing system in this image forming apparatus. In this example, the image forming apparatus is configured as a printer. This signal processing system includes a printer driver 60 and an image processing unit 70 as a control unit.
The printer driver 60 includes a PC (personal computer) 61 and a PDL (PDL: Page Description Language) generating unit 62. The PDL generation unit 62 converts an image described in a predetermined PDL on the screen of the PC 61 by the user into code data and outputs the code data.

  The image processing unit 70 includes a raster image generation unit 71, a color conversion processing unit 72, an output image processing unit 73, a data storage unit 74, an output data selection unit 75, a pulse width modulation unit 76, and a laser driver 77. The image processing unit 70 further includes a creation patch determination unit 78. The image processing unit 70 further includes a density comparison unit 81, a correction data generation unit 82, and a correction data storage unit 83. In the present embodiment, the density comparison unit 81, the correction data generation unit 82, and the correction data storage unit 83 constitute an adjustment unit. The data storage unit 74 includes an image data storage unit 74a and a patch data storage unit 74b.

The raster image generation unit 71 converts the code data described in PDL output from the PDL generation unit 62 into raster data for each pixel. The raster image generation unit 71 outputs the converted raster data as RGB (Red, Green, Blue) video data (RGB video data). At this time, the raster image generation unit 71 outputs RGB data for each page. The color conversion processing unit 72 converts the RGB data input from the raster image generation unit 71 into device-independent color values such as [XYZ], [L ^* a ^* b ^* ], and [L ^* u ^* v ^* ]. After the conversion, it is converted into YMCK data which is the reproduction color (yellow, magenta, cyan, black) of the image forming apparatus and output. This YMCK data is composed of Y color data, M color data, C color data, and K color data separated for each color.

  The output image processing unit 73 performs γ conversion, definition processing, halftone processing, and the like on the YMCK data input from the color conversion processing unit 72, and outputs it as image data for forming the image toner image G1. To do. The image data storage unit 74a of the data storage unit 74 stores the image data (image processed YMCK data) output from the output image processing unit 73.

  On the other hand, a creation patch determination unit 78 as a determination unit and a change unit determines the content of the image quality adjustment toner image G2 (patch image) to be created based on the YMCK data input from the color conversion processing unit 72. The data is output as patch data for forming the image quality adjusting toner image G2. The patch data storage unit 74 b of the data storage unit 74 stores the patch data output from the created patch determination unit 78.

  The output data selection unit 75 sequentially selects the image data stored in the image data storage unit 74a of the data storage unit 74 and the patch data stored in the patch data storage unit 74b according to the set order, Output. The pulse width modulation unit 76 modulates the image data (image data or patch data) of each color output from the output data selection unit 75 in accordance with the density of the image data, thereby increasing the on-time length of the pulse. It converts and outputs as light quantity data of each color. Based on the light amount data of each color input from the pulse width modulator 76, the laser driver 77 exposes each color exposure unit 13 (specifically, a yellow exposure unit (Y exposure unit) 13Y, a magenta exposure unit (M exposure unit) 13M). , The cyan exposure unit (C exposure unit) 13C and the black exposure unit (K exposure unit) 13K) are driven. The laser driver 77 receives light amount correction data from the correction data storage unit 83, and the laser driver 77 drives each color exposure unit 13 while performing light amount correction based on the light amount correction data.

  In addition, density data obtained by reading the image quality adjustment toner image G <b> 2 by the density sensor 27 and information on patch data sent from the output data selection unit 75 are input to the density comparison unit 81. Then, the density comparison unit 81 compares the target density of each patch image constituting the image quality adjustment toner image G2 with the actually measured density, and uses the obtained comparison results as a creation patch determination unit 78 and a correction data generation unit 82. Output to. The correction data generation unit 82 generates light amount correction data for each color for performing density correction based on the comparison result input from the density comparison unit 81. The correction data storage unit 83 stores the light amount correction data for each color generated by the correction data generation unit 82. The created patch determination unit 78 also has a function of determining whether to increase the size of the patch image to be formed based on the comparison result input from the density comparison unit 81.

FIG. 4 is a block diagram for explaining the configuration of the created patch determination unit 78 provided in the image processing unit 70 shown in FIG. The created patch determination unit 78 includes a specified color storage unit 91, a specified color extraction unit 92, an area acquisition unit 93, a density distribution acquisition unit 94, an attention color extraction unit 95, a patch data storage unit 96, and a content determination unit 97. .
The designated color storage unit 91 stores a designated color (referred to as a device designated color) determined in advance for the image forming apparatus. Here, the device designated color is determined in advance when it is known that density deviation is likely to occur in a specific color toner. Therefore, there is a case where the device designated color is not stored in the designated color storage unit 91. The designated color extracting unit 92 reads the device designated color and outputs it to the content determining unit 97 as designated color information when the designated color storage unit 91 stores the device designated color. The designated color extraction unit 92 outputs the user designated color to the content determination unit 97 as designated color information when an instruction of a designated color (referred to as a user designated color) is received from the PC 61 by a user or the like.

The area acquisition unit 93 acquires the area of each color for each color based on the YMCK data input from the color conversion processing unit 72 and outputs the acquired area to the target color extraction unit 95. The density distribution acquisition unit 94 acquires the density distribution of each color based on the YMCK data input from the color conversion processing unit 72 and outputs it to the target color extraction unit 95. The attention color extraction unit 95 extracts a color to be noticed and its density based on the area information of each color input from the area acquisition unit 93 and the density distribution information of each color input from the density distribution acquisition unit 94, and It outputs to the content determination part 97 as color information. The content determination unit 97 refers to the specified color information input from the specified color extraction unit 92 and the target color information input from the target color extraction unit 95, and the image quality adjustment toner image G2 corresponding to the input YMCK data. Is output to the patch data storage unit 74b of the data storage unit 74.
The content determination unit 97 also receives a comparison result based on the read result of the image quality adjustment toner image G2 actually formed from the density comparison unit 81. Then, the content determination unit 97 determines the content of the patch image constituting the image quality adjustment toner image G2 (in this case, whether to increase the size of the patch image) based on the input comparison result. Here, the patch data storage unit 96 stores patch data including a large patch image. When the content determination unit 97 determines to enlarge the patch image, the content determination unit 97 reads out the patch data including the large patch image from the patch data storage unit 96 and outputs it to the patch data storage unit 74b of the data storage unit 74. To do.

  FIG. 5 is a block diagram for explaining the configuration of the data storage unit 74 provided in the image processing unit 70 shown in FIG. The data storage unit 74 includes an interface (I / F) 101, a memory controller 102, and a memory 103. In the present embodiment, the memory 103 functions as an image data storage unit 74a and a patch data storage unit 74b.

  The I / F 101 passes the image data sent from the output image processing unit 73 and the patch data sent from the created patch determination unit 78 to the memory 103 via the memory controller 102. Further, the I / F 101 passes the image data (image data or patch data) read from the memory 103 by the memory controller 102 to the output data selection unit 75. The memory controller 102 controls storage and reading of image data and patch data with respect to the memory 103. The memory 103 can store image data In (n-th), In + 1 (n + 1-th), In + 2 (n + 2-th), In + 3 (n + 3-th) for four sheets on which image formation is to be performed. Of these four image data In to In + 3, patch data Pn + 1 corresponding to the (n + 1) th image data In + 1 and patch data corresponding to the (n + 2) th image data In + 2 Pn + 2 has a capacity capable of storing the patch image data Pn + 3 corresponding to the (n + 3) th image data In + 3. Then, the memory controller 102 erases the image data and the patch data that have been output to the output data selection unit 75, and the image data newly input from the output image processing unit 73 or the created patch determination unit 78 Data is updated by storing patch data.

  FIG. 6 is a flowchart for explaining the flow of basic image processing in the image processing unit 70 shown in FIG. When the PDL is input from the PDL generation unit 62 (step 101), the raster image generation unit 71 converts the code data described in the PDL to generate raster data (step 102). Next, the color conversion processing unit 72 performs color conversion processing on the RGB video data input from the raster image generation unit 71 (step 103), and outputs YMCK data.

  Then, the output image processing unit 73 performs predetermined output image processing on the input YMCK data (step 104), and stores the obtained image data in the data storage unit 74 (image data storage unit 74a). (Step 105). On the other hand, the created patch determining unit 78 determines the content of the patch image to be created based on the input YMCK data (step 106), and the patch data whose content is determined is stored in the data storage unit 74 (for patch). The data is stored in the data storage unit 74b) (step 107).

  Thereafter, the output data selection unit 75 selects and reads out image data or patch data from the data storage unit 74 in accordance with a procedure to be described later (step 108). The pulse width modulation unit 76 performs pulse width modulation on the image data of each color output from the output data selection unit 75 (S109), and outputs the light amount data of each color. The laser driver 77 performs light amount correction on the light amount data of each color input from the pulse width modulation unit 76 based on the light amount correction data of each color read from the correction data storage unit 83 (step 110), and the exposure unit 13 of each color. (Specifically, Y exposure unit 13Y, M exposure unit 13M, C exposure unit 13C, K exposure unit 13K) are driven (step 111). Thereafter, in each image forming unit 10, charging, exposure, development, and primary transfer are performed, and a toner image (image toner image and patch toner image) is formed on the intermediate transfer belt 20.

  FIG. 7 is a flowchart for explaining the flow of density correction processing in the image processing unit 70 shown in FIG. First, density data obtained by reading the image quality adjusting toner image G2 formed on the intermediate transfer belt 20 is input from the density sensor 27 to the density comparison unit 81 (step 201). Further, the output of the patch data (information regarding the color and density of each patch image constituting the read image quality adjustment toner image G2) is input from the output data selection unit 75 to the density comparison unit 81. (Step 202). Next, the density comparison unit 81 compares the density of each read patch image with the density targeted by each patch image (step 203). Then, the density comparison unit 81 determines whether or not any density comparison result (density difference) of each patch image deviates from a preset allowable range (step 204), and deviates from the allowable range. If there is one, a patch image size change request is output to the created patch determination unit 78 (step 205). On the other hand, if no density comparison result deviates from the allowable range in step 204, the density comparison unit 81 outputs the density comparison result to the correction data generation unit 82. The correction data generation unit 82 generates light amount correction data for performing density correction for each color based on the input density comparison result (step 206). Then, the correction data storage unit 83 stores the light amount correction data for each color generated by the correction data generation unit 82 (step 207).

  FIG. 8 is a flowchart for explaining the operation of the created patch determination unit 78 (see FIG. 4) in steps 106 to 107 in the image processing process shown in FIG. First, the designated color extraction unit 92 determines whether or not a user designated color has been designated by the PC 61 (step 301). If there is a user designated color, this user designated color is designated as designated color information of importance level 1. As an entry (step 302). On the other hand, if there is no user-specified color, the process proceeds to the next step 303 as it is. Next, the designated color extraction unit 92 determines whether or not a device designated color is stored in the designated color storage unit 91 (step 303). If there is a device designated color, the device designated color is important. It is entered as designated color information of degree 2 (step 304). On the other hand, if there is no device designated color, the process proceeds to the next step 305 as it is.

  Next, the area acquisition unit 93 acquires the area of each color for each color based on the YMCK data input from the color conversion processing unit 72 (step 305). The density distribution acquisition unit 94 acquires the density distribution of each color based on the YMCK data data input from the color conversion processing unit 72 (step 306). The attention color extraction unit 95 extracts a color to be noticed and its density based on the area information of each color input from the area acquisition unit 93 and the density distribution information of each color input from the density distribution acquisition unit 94. Then, it is entered as attention color information of importance 3 (step 307). At this time, the attention color extraction unit 95 extracts the one having the largest area among the YMCK colors and the one having the highest frequency of density distribution in each YMCK color as attention color information.

  The content determination unit 97 receives the specified color information (user specified color (importance 1), device specified color (importance 2)) input from the specified color extraction unit 92 and the target color extraction unit 95. Based on the target color information (importance 3), the content (patch data) of the image quality adjustment toner image G2 (patch image) to be formed corresponding to the YMCK data is determined (step 308). Details of the patch image constituting the image quality adjustment toner image G2 will be described later. The determined patch data is stored in the patch data storage unit 74b of the data storage unit 74 (step 309).

  FIG. 9 is a flowchart for explaining the operation of the output data selection unit 75 (see FIG. 3) in step 108 in the image processing process shown in FIG. The output data selection unit 75 first reads and outputs the (n + 1) th patch data Pn + 1 from the patch data storage unit 74b of the data storage unit 74 shown in FIG. 5 (step 401). Next, the output data selection unit 75 reads and outputs the (n + 2) th patch data Pn + 2 from the patch data storage unit 74b of the data storage unit 74 (step 402). Further, the output data selection unit 75 reads out and outputs the (n + 3) th patch data Pn + 3 from the patch data storage unit 74b of the data storage unit 74 (step 403). Then, the output data selection unit 75 reads and outputs the nth image data In from the image data storage unit 74a of the data storage unit 74 (step 404). Thereafter, the output data selection unit 75 updates the value of n to n + 1 (step 405), and whether or not the nth image data exists (stored in the image data storage unit 74a of the data storage unit 74). (Step 406). If the next n-th image data exists, the process returns to step 401 to continue the processing. On the other hand, when the next n-th image data does not exist, the series of processes is terminated.

  Accordingly, on the intermediate transfer belt 20, the formation of three patch toner images and the formation of one image toner image are alternately performed. Three patch toner images are formed in the inter-image area S2, and one image toner image is formed in the image area S1.

Here, the flow of processing until the image toner image for one sheet is formed using this image forming apparatus will be described with a little change in viewpoint. 10 to 12 are flowcharts for explaining the flow of this processing.
When PDL is input from the PDL generation unit 62 (step 501), the raster image generation unit 71 converts the code data described in PDL to generate raster data (step 502). Next, the color conversion processing unit 72 performs color conversion processing on the RGB video data input from the raster image generation unit 71 (step 503), and outputs YMCK data.

  Then, the output image processing unit 73 performs predetermined output image processing on the input YMCK data (step 504), and stores the obtained image data in the data storage unit 74 (image data storage unit 74a). (Step 505). On the other hand, the created patch determining unit 78 determines the content of the patch image to be created based on the input YMCK data (step 506), and the patch data whose content is determined is stored in the data storage unit 74 (for patch). The data is stored in the data storage unit 74b) (step 507).

  Next, the patch data is read by the output data selector 75 (step 508), and the image quality adjustment toner image G2 (first time) is formed based on the patch data (step 509). Then, density data obtained by reading the image quality adjusting toner image G2 (first time) formed on the intermediate transfer belt 20 is input from the density sensor 27 to the density comparison unit 81 (step 510). Further, the output of the patch data (information regarding the color and density of each patch image constituting the read image quality adjustment toner image G2) is input from the output data selection unit 75 to the density comparison unit 81. (Step 511). Next, the density comparison unit 81 compares the density of each read patch image with the density targeted by each patch image (step 512). Then, the density comparison unit 81 determines whether or not any density comparison result (density difference) of each patch image deviates from a preset allowable range (step 513), and deviates from the allowable range. If there is one, a patch image size change request is output to the created patch determination unit 78 (step 514). On the other hand, if there is no density comparison result that deviates from the allowable range in step 513, the density comparison unit 81 outputs the density comparison result to the correction data generation unit 82. The correction data generation unit 82 generates light amount correction data (first time) for performing density correction for each color based on the input density comparison result (step 515). Then, the correction data storage unit 83 stores the light amount correction data (first time) of each color generated by the correction data generation unit 82 (step 516).

  Next, the same patch data as in step 508 is read out by the output data selection unit 75 (step 517), and the light amount correction data (first time) of each color stored in the correction data generation unit 82 in step 516 above. It is read (step 518). Then, the image quality adjusting toner image G2 (second time) is formed based on the patch data (step 519). At this time, the laser driver 77 performs light amount correction using the light amount correction data (first time) read from the correction data storage unit 83 in step 518. For this reason, the image quality adjustment toner image G2 (second time) is formed in a state where the light amount is corrected. Then, density data obtained by reading the image quality adjusting toner image G2 (second time) formed on the intermediate transfer belt 20 is input from the density sensor 27 to the density comparison unit 81 (step 520). Further, the information on the output patch data is input to the density comparison unit 81 from the output data selection unit 75 (step 521). Next, the density comparison unit 81 compares the density of each read patch image with the density targeted by each patch image (step 522). Then, the density comparison unit 81 determines whether or not any density comparison result (density difference) of each patch image deviates from the preset allowable range (step 523), and deviates from the allowable range. If there is one, a patch image size change request is output to the created patch determination unit 78 (step 524). On the other hand, if there is no density comparison result that deviates from the allowable range in step 523, the density comparison unit 81 outputs the density comparison result to the correction data generation unit 82. The correction data generation unit 82 generates light amount correction data (second time) for performing density correction for each color based on the input density comparison result (step 525). Then, the correction data storage unit 83 stores the light amount correction data (second time) for each color generated by the correction data generation unit 82 (step 526).

  Next, the same patch data as in steps 508 and 517 is read by the output data selection unit 75 (step 527), and the light amount correction data (2 for each color) stored in the correction data generation unit 82 in step 526 above. Time) is read (step 528). Then, the image quality adjusting toner image G2 (third time) is formed based on the patch data (step 529). At this time, the laser driver 77 performs light amount correction using the light amount correction data (second time) read from the correction data storage unit 83 in step 528. Therefore, the image quality adjustment toner image G2 (third time) is formed in a state where the light amount is corrected. Then, density data obtained by reading the image quality adjusting toner image G2 (third time) formed on the intermediate transfer belt 20 is input from the density sensor 27 to the density comparison unit 81 (step 530). Further, the information of the output patch data is input to the density comparison unit 81 from the output data selection unit 75 (step 531). Next, the density comparison unit 81 compares the density of each read patch image with the density targeted by each patch image (step 532). Then, the density comparison unit 81 determines whether or not any density comparison result (density difference) of each patch image deviates from a preset allowable range (step 533), and deviates from the allowable range. If there is one, a patch image size change request is output to the created patch determination unit 78 (step 534). On the other hand, if there is no density comparison result that deviates from the allowable range in step 533, the density comparison unit 81 outputs the density comparison result to the correction data generation unit 82. The correction data generation unit 82 generates light amount correction data (third time) for performing density correction for each color based on the input density comparison result (step 535). Then, the correction data storage unit 83 stores the light amount correction data (third time) for each color generated by the correction data generation unit 82 (step 536).

  Then, the patch data and the original YMCK data are the same image data by the output data selection unit 75, that is, the image data stored in the data storage unit 74 (image data storage unit 74a) in step 505 above. Is read (step 537), and the light amount correction data (third time) of each color stored in the correction data generation unit 82 in step 536 is read (step 538). Then, an image toner image G1 is formed based on the read image data (step 539). At this time, the laser driver 77 performs light amount correction using the light amount correction data (third time) read from the correction data storage unit 83 in step 538. For this reason, the image toner image G1 is formed in a state where the light amount correction is performed a plurality of times.

  Here, FIG. 13A is a diagram for explaining the contents of the toner image formed on the intermediate transfer belt 20 (see FIG. 1). In this example, the image toner image G1 based on the first image data I1 is displayed in the most upstream image area S1 of the intermediate transfer belt 20 shown in the figure, and the second image is displayed in the next image area S1. An image toner image G1 based on the image data I2, a next image toner image G1 based on the third image data I3 in the image region S1, and a fourth image in the most downstream image region S1. It is assumed that an image toner image G1 based on the use data I4 is formed.

  In the present embodiment, the image toner image G1 and the image quality adjustment toner image G2 are formed according to the procedure described with reference to FIG. For this reason, for example, in the inter image area S2 upstream of the image area S1 where the image toner image G1 based on the first image data I1 is formed, the patch data for three sheets, that is, the second patch data is used. An image quality adjustment toner image G2 based on the data P2, the third patch data P3, and the fourth patch data P4 is formed. Here, the second patch data P2 corresponds to the second image data I2 from which image formation will be performed, and the third patch data P3 is the third image data from which image formation will be performed. Corresponding to I3, the fourth patch data P4 corresponds to the fourth image data I4 from which image formation will be performed. Similarly, in the other inter-image areas S2, image quality adjustment toner images G2 based on the patch data for three sheets corresponding to the image data for three sheets on which image formation is to be performed are formed.

  Here, focusing on the fourth sheet, the first image quality adjustment toner image G2 (based on the patch data P4) is formed by the image toner image G1 (based on the first image data I1). To the inter image area S2 upstream of the image area S1 to be processed. The second image quality adjustment toner image G2 is formed in the inter-image area S2 upstream of the image area S1 where the image toner image G1 (based on the second image data I2) is formed. . Further, the third image quality adjustment toner image G2 is formed in the inter image area S2 upstream of the image area S1 where the image toner image G1 (based on the third image data I3) is formed. . In this example, it is assumed that it takes time for one image area S1 to acquire the third light amount correction data, and the formation of the corresponding image quality adjustment toner image G2 is completed on the upstream side. Yes.

  13B shows the configuration of the image quality adjustment toner image G2 based on the patch data P2, the third patch data P3, and the fourth patch data P4 shown in FIG. 13A. An example is shown. Here, each of the patch data P2, P3, and P4 includes eight patch images a to h. However, the contents of the patch data P2, P3, and P4 are determined corresponding to the corresponding image data I2, I3, and I4, and the contents of the image data I2, I3, and I4 are different. Of course, the contents are different.

  Here, Table 1 shows an example of the contents of the patch data P2, P3, and P4.

  For example, when the content of the second image data I2 is a reddish full color image, the ratio of yellow and magenta forming red in the eight patch images a to h constituting the patch data P2 On the other hand, the proportion of cyan and black decreases. For example, when the content of the third image data I3 is a monochrome image in the photo mode, all the patch images a to h constituting the patch data P3 are black, and yellow, magenta, and cyan are not included. . Further, for example, when magenta is designated as the user designated color or the device designated color for the fourth image data I4, the magenta of the eight patch images a to h constituting the patch data P4 is displayed. The proportion occupied is high.

  FIG. 14A is a diagram for explaining the size of each patch image shown in FIG. As shown in the figure, each patch image has a square shape of 1 mm × 1 mm, and the interval between the patch images is 1 mm. That is, the image quality adjustment toner image G2 formed in the inter-image area S2 is composed of such a small patch image (micropatch). This is very effective for forming many image patches in the inter-image area S2, which is difficult to secure widely from the viewpoint of productivity.

  On the other hand, FIG. 14B is a diagram for explaining the size of the patch image formed when a patch size change request is issued in step 205 shown in FIG. As shown in the figure, each patch image has a square shape of 20 mm × 20 mm, and the interval between the patch images is 20 mm. Therefore, compared with the micropatch shown in FIG.

In this embodiment, normally, the micropatch shown in FIG. 14A is formed in the inter-image area S2, and density control is performed based on the reading result. However, when the area of the patch image is small, the color tends to be shifted due to an edge effect or the like as compared to when the area is large. In other words, the micropatch is suitable for making a relative comparison of whether it is dark or light, but in some cases it is not sufficient for an absolute comparison.
Therefore, in this embodiment, when a large density shift is detected, a large image patch shown in FIG. 14B is formed to perform density correction. This makes it easy to obtain an absolute density, and more accurate density correction can be performed.

As described above, in the present embodiment, the content of the image quality adjustment toner image G2 to be created in advance is determined according to the image data (YMCK data) to be created. Then, after correcting the image forming condition (the amount of light in the present embodiment) based on the image formation result (density detection result) of the determined image quality adjustment toner image G2, the image toner image G1 based on the image data is corrected. The formation of. As a result, it is possible to form the image toner image G1 in a state where appropriate correction is performed for each image data, and it is possible to obtain a good image with suppressed density deviation. In this embodiment, the image quality adjusting toner image G2 is formed in the inter image area S2 provided between the image areas S1 where the image toner image G1 is formed. For this reason, it is possible to adjust the concentration without causing a decrease in productivity.
In a general image, it can be said that the entire color gamut is not actually used in one page, and most of the color gamut is composed only of a limited color gamut. Therefore, in the present embodiment, the color used for each image data (page) is extracted, only the image patch of the necessary color is created, and density correction is performed so that the color is optimized. did. This makes it possible to set optimal image forming conditions for each image data without increasing the number of image patches to be created.

  Further, in this embodiment, before starting an image forming operation based on certain image data (formation of an image toner image G1), an image quality adjustment toner image G2 corresponding to the image data is created a plurality of times in advance. The image forming condition (light quantity) was corrected while performing feedback control. In other words, before the formation of the image toner image G1 based on the image data is started, the formation and density correction of the image quality adjustment toner image G2 determined based on the image data are completed. For this reason, it is possible to perform more accurate correction and further suppress the density deviation. In particular, in the present embodiment, since the image quality adjustment toner image G2 for a plurality of pages is formed in the inter image area S2, the image quality adjustment toner image G2 corresponding to certain image data can be formed a plurality of times. it can.

  Further, in the present embodiment, since the content of the image quality adjustment toner image G2 is determined according to the image data, the determined image quality adjustment toner image G2 includes, for example, colors not included in the image data. The toner image of the component or density component is not included. Therefore, useless toner consumption can be suppressed.

  In the present embodiment, the image quality adjustment toner image G2 is usually formed by a very small micropatch image, and when the density deviation of the image quality adjustment toner image G2 composed of the micropatch image is significant, the large patch image is used. An image quality adjusting toner image G2 is formed. Thereby, it is possible to suppress wasteful toner consumption while suppressing density deviation.

  In this embodiment, the density sensor 27 is disposed opposite to the intermediate transfer belt 20, and the image quality adjustment toner image G2 (each color) primarily transferred from the image forming units 10Y, 10M, 10C, and 10K to the intermediate transfer belt 20. However, the present invention is not limited to this. That is, for example, a configuration may be adopted in which density sensors are arranged to face the photosensitive drums 11 of the image forming units 10Y, 10M, 10C, and 10K, and patch images of each color are read. In this case, each photosensitive drum 11 functions as an image carrier. However, in the intermediate transfer type image forming apparatus as in the present embodiment, since there are not a few density fluctuations in the primary transfer, the image quality adjusting toner image G2 that has been primarily transferred onto the intermediate transfer belt 20 is read. Is effective.

In the present embodiment, the adjustment of the exposure amount in the exposure unit 13 occurs when adjusting the image forming conditions in each of the image forming units 10Y, 10M, 10C, and 10K. However, the present invention is not limited to this. . That is, for example, adjustment of the charge amount by the charging roll 12, adjustment of the developer amount and developing bias of the developing device 14, adjustment of the primary transfer bias by the primary transfer roll 15, and further correction for the image data itself. Also good.
Furthermore, in the present embodiment, an example of density detection using a density sensor has been described. However, the present invention is not limited to this, and correction by color detection such as L ^* a ^* b ^* using a color sensor or the like may be used. .
Furthermore, in the present embodiment, an image forming apparatus using an electrophotographic method has been described as an example. However, the present invention is not limited to this, and an apparatus that forms an image by, for example, an electrostatic recording method or an ink jet method. It can be similarly applied to.

1 is an overall configuration diagram of an image forming apparatus to which an embodiment is applied. FIG. 4 is a diagram for explaining an image area and an inter image area on an intermediate transfer belt. 2 is a block diagram illustrating a signal processing system in the image forming apparatus. FIG. It is a figure for demonstrating the structure of the preparation patch determination part. It is a block diagram for demonstrating the structure of a data storage part. It is a flowchart for demonstrating the flow of the basic image processing in an image processing part. It is a flowchart for demonstrating the flow of the density correction process in an image process part. It is a flowchart for demonstrating operation | movement of the preparation patch determination part. It is a flowchart for demonstrating operation | movement of an output data selection part. 5 is a flowchart (1) for explaining the flow of processing until an image toner image for one sheet is formed. 12 is a flowchart (2) for explaining the flow of processing until an image toner image for one sheet is formed. 12 is a flowchart (3) for explaining the flow of processing until an image toner image for one sheet is formed. (a) is a diagram showing the positional relationship between an image toner image and an image quality adjustment toner image formed on the intermediate transfer belt, and (b) is a plurality of image quality adjustment images formed in one inter image area. FIG. 4 is a diagram for explaining a configuration of a toner image. (a) is a diagram for explaining the size of a patch image (micropatch) that is normally formed, and (b) is a diagram for explaining the size of a patch image that is formed when a patch size change request is issued.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Image forming unit, 11 ... Photosensitive drum, 12 ... Charging roll, 13 ... Exposure part, 14 ... Developing device, 15 ... Primary transfer roll, 20 ... Intermediate transfer belt, 27 ... Density sensor, 30 ... Secondary transfer device , 60 ... Printer driver, 70 ... Image processing unit, 71 ... Raster image generation unit, 72 ... Color conversion processing unit, 73 ... Output image processing unit, 74 ... Data storage unit, 75 ... Output data selection unit, 76 ... Pulse width Modulating unit 77... Laser driver 78. Preparation patch determining unit 81. Density comparing unit 82. Correction data generating unit 83. Correction data storage unit S 1 Image area S 2 Inter image area

Claims (8)

An image image including one or a plurality of colors is formed on the image carrier, and a plurality of patch images whose number is determined in advance are included in an area where the image image is not formed on the image carrier. An image forming unit for forming an image for image quality adjustment;
A determination unit that determines a combination of colors in the plurality of patch images constituting the image quality adjustment image, using image data input to form the image for image ;
A reading unit for reading the image for image quality adjustment, the content of which is determined by the determining unit and formed on the image carrier by the image forming unit;
An image forming apparatus including: an adjustment unit that adjusts an image forming condition of the image forming unit when the image image is formed based on the image data based on a reading result of the reading unit. An acquisition unit for acquiring a designated color designated among a plurality of colors constituting the image for image;
The determination unit determines the number of patch images of the designated color acquired by the acquisition unit in the plurality of patch images when determining the combination of colors in the plurality of patch images constituting the image quality adjustment image. The image forming apparatus according to claim 1, wherein the number is increased. The determining unit, when determining a combination of colors in the plurality of patch images constituting the image quality adjustment image, compares the area of the image data of each color obtained by separating the image data for each color, The image forming apparatus according to claim 1, wherein, in the plurality of patch images, the number of patch images having a large area is increased. The determination unit obtains a color distribution in the image data of each color obtained by separating the image data for each color when determining a combination of colors in the plurality of patch images constituting the image for image quality adjustment 4. The image forming apparatus according to claim 1, wherein, in the plurality of patch images, the number of color patch images having a high frequency in the distribution is increased. 5. The determining unit obtains a density distribution in the image data of each color obtained by separating the image data for each color when determining a combination of colors in the plurality of patch images constituting the image for image quality adjustment. 5. The image according to claim 1, wherein, in the plurality of patch images for which color distribution is determined, the density of each patch image is determined to be a density having a high frequency in the distribution. Forming equipment. The image forming unit forms the image for image in a first area set on the image carrier, and the first area on the image carrier and another first area adjacent to the first area. Forming the image quality adjustment image in the second region set between the image image, the image image and the image quality adjustment image are alternately formed on the image carrier,
The determination unit determines the content of the image quality adjustment image corresponding to the image data before starting the formation of the image image based on the image data,
The adjustment unit, according to any one of claims 1 to 5, characterized in that to complete the adjustment of the imaging conditions of the image forming unit before starting the formation of the image for an image based on the image data Image forming apparatus. For the common image data, the image forming unit forms the image for adjusting the image quality in the second region, reads the image by the reading unit, and adjusts the image forming condition by the adjusting unit for each second region. The image forming apparatus according to claim 6, wherein the image forming unit executes the formation of the image for the image based on the image data in the first area after repeating a plurality of times. The image processing apparatus further includes a changing unit that increases the size of the image quality adjustment image to be formed next in the image forming unit when the density of the image quality adjustment image read by the reading unit deviates from a predetermined range. The image forming apparatus according to claim 7.

Images