JP5402097B2 - Image forming apparatus, image forming method, program, and recording medium - Google Patents

Description

  The present invention relates to an image forming apparatus such as a color printer using an electrophotographic system, and more particularly to a technique suitable for a multifunction machine, a fax machine, or the like using an electrophotographic system.

In recent years, POD (Print On Demand) has been proposed and is becoming mainstream as an alternative to offset printing. POD is a digital printing technique that prints only a necessary amount when necessary without going through a plate making process in printing. Unlike printing that creates and edits CMYK manuscripts like offset printing, RGB (or CMYK images) are edited using a display to obtain a CMYK image that is the color space of the image forming apparatus and print directly. There are various advantages to doing. For example,
-The cost per part can be reduced when printing small copies.
・ It has free support for graphic functions and enables printing one by one differently.
・ Short delivery time.
Etc.

  In addition, it is a field that has been rapidly developed along with the advancement of information technology, such as the spread of high-performance personal computers and networks, and is expected to grow into a large market in the printing industry.

  As an entry means to POD, inkjet and electrophotographic systems are being introduced. Especially in electrophotography, the laser spot diameter is miniaturized, the polygon is rotated at high speed, the development of 2-beam or 4-beam optical system, and the LED head. Various technologies have been introduced and improved in order to obtain an image quality equivalent to that of offset printing, such as an increase in recording density and recording speed due to improvements in writing technology due to miniaturization and the like.

  On the other hand, a problem in electrophotography is that it is difficult to secure a wide color gamut equivalent to printing by using toner. In order to solve this problem, conventionally, the area ratio of 100%, that is, the density reproducibility of solid and secondary colors has been considered the most important problem. Here, the primary colors are cyan, magenta, yellow, and black, which are basic colors of the color materials used, and the secondary colors are red, green, and blue.

  In an electrophotographic image forming apparatus, the solid density is determined by controlling the exposure energy to the photoconductor. Conventionally, the solid density has been set to a fixed value except for control over time. For this reason, as means for obtaining color reproducibility close to that of offset printing, only color adjustment by RGB to CMYK color conversion table has been performed. In other words, since the solid density is significantly different from that of offset printing, sufficient color approximation cannot be obtained only by halftone color adjustment.

  Therefore, for example, when performing a printing simulation on an electrophotographic image forming apparatus for various papers, a technique for controlling the exposure energy described above is proposed in order to obtain a solid density equivalent to the solid density of offset printing. (See Patent Document 1).

  However, as disclosed in Patent Document 1, it has been found that obtaining a solid density equivalent to offset printing with an electrophotographic image forming apparatus and performing a printing simulation has a great problem in color reproduction. .

  Originally, in electrophotography, since toner is used as a color material, there is a characteristic that gloss is lower than printing and it is difficult to ensure saturation. If you try to match the density of a color material with poor chroma reproducibility (electrophotographic toner) and a color material with good chroma reproducibility (printing ink), the reproduction brightness will decrease, and as a result, the highlight will be reproduced. Sexuality gets worse. This will be described with reference to FIGS.

  FIG. 12 shows cyan spectral reflectances for printing and electrophotography, where the horizontal axis represents wavelength and the vertical axis represents reflectance. In cyan, the reflection band is around 450 to 550 nm, and the absorption band is around 600 to 650 nm. According to the CIE1976L * a * b * color system, the saturation value (= sqrt (a * ^ 2 + b * ^ 2)) depends on the difference in reflectance between the reflection band and the absorption band, and the saturation value increases as the difference increases. Is expensive. On the other hand, the density is defined by the reflectance of the absorption band, and matching the density is nothing but matching the spectral reflectance of the absorption band. As a result, as shown in FIG. 12, the reflectance of the reflection band is lower in the electrophotography with poor saturation reproducibility. On the other hand, according to the CIE 1976 L * a * b * color system, the brightness value is defined by the reflectance over the entire visible light range (400 to 700 nm). Therefore, in FIG. 12, the reproducibility is lower in the electrophotography having a lower reflectance in the reflection band.

  FIG. 13A shows cyan gamut for printing and electrophotography, where the horizontal axis represents saturation and the vertical axis represents lightness. FIG. 13A is caused by the difference in reproduction saturation and reproduction brightness described above when the white point (WP in the figure, paper white) and the black point (BP in the figure, darkest part) match. The gamut difference is shown. In the case of an electrophotography with low reproduction saturation and low reproduction brightness, the shaded area in the figure is an area where color reproduction with an electrophotography is impossible. That is, the highlight gamut cannot be secured by electrophotography.

  Moreover, even if the saturation equivalent to printing can be secured in electrophotography, if the reproduction brightness is low, the highlight reproducibility is poor, and even if the same brightness reproduction as printing is possible, if the reproduction saturation is low A gamut in the vicinity of the solid cannot be secured (FIG. 13B). On the other hand, when the reproducibility of the electrophotographic solid is higher than that of printing, the shadow reproducibility (shaded area in FIG. 13C) is adversely affected.

  Next, FIG. 14 shows the relationship between saturation and lightness in a certain monochromatic hue, with the horizontal axis representing saturation and the vertical axis representing lightness. The inventors' experiments have shown that when the amount of adhesion is changed by changing the thickness of the toner layer, the reproduced color moves on the locus of Line A. That is, as the toner layer is made thicker, it passes through the highest saturation point SP where the saturation is maximum so as to draw an arc from WP (white point) which is paper white. When the maximum saturation point SP is exceeded, the saturation does not increase even if the adhesion amount is increased further, and the saturation and lightness decrease as if the arc is drawn again. Here, the surface shape of the toner layer is the same, and the thickness of the toner layer is adjusted by the intensity of the laser beam exposed to the photoreceptor.

  From the above, when performing a printing simulation with an electrophotographic image forming apparatus, the solid density of the electrophotography should be set so that the reproduction color gamut of printing can be included as much as possible, not the density of printing. . Further, in order to maximally include the reproduction color gamut of printing, it is necessary to adjust the toner layer thickness and control the solid density to an optimum value by controlling the writing exposure energy to the photosensitive member. .

The present invention has been made in view of the above circumstances,
An object of the present invention is to provide an image forming apparatus, an image forming method, a program, and a recording medium capable of obtaining a color reproduction range close to printing when performing a printing simulation in an electrophotographic image forming apparatus. is there.

The present invention is an image forming apparatus for simulating an arbitrary color standard, an exposure unit that forms an electrostatic latent image by exposing light to a photosensitive member, and the formed electrostatic latent image is converted into a toner image. Developing means for forming an image, transfer means for transferring the toner image onto a recording medium, fixing means for fixing the toner image on the recording medium, and the image formation for a color belonging to the color gamut of the color standard It is most important to have acquisition means for acquiring a gamut cover ratio reproduced by the apparatus, and exposure control means for controlling exposure energy in the exposure means so that the gamut cover ratio obtained by the acquisition means is maximized. Features.

  According to the present invention, when a printing simulation is performed by an electrophotographic image forming apparatus, a color reproduction range close to printing can be obtained.

1 shows an overall configuration of an image forming apparatus of the present invention. It is a figure explaining the various sensors incorporated in the image forming apparatus. The structure of the control part of Example 1 is shown. 6 shows an operation flowchart of an exposure energy control mode in the control unit of Embodiment 1. An example of color standard information is shown. The color reproduction information stored in the first and second storage units is shown. It is a figure explaining a gamut outermost outline and a gamut cover rate. The structure of the control part of Example 2 is shown. 9 shows an operation flowchart of an exposure energy control mode in the control unit of Embodiment 2. 6 shows a table of toner adhesion amounts with respect to patch sensor output values. The structure of Example 3 of this invention is shown. The cyan spectral reflectance of printed and electrophotographic images is shown. It is a figure explaining the difference in the color gamut of printing and electrophotography. The relationship between saturation and lightness in a single hue is shown.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  In the first embodiment, color standard information is received, and the gamut cover ratio for each exposure energy is calculated using the basic color in the image forming apparatus and the color information of the dot area ratio of 100% (hereinafter referred to as “solid”). Then, the reproducibility is evaluated, and the exposure energy is controlled using the result.

  FIG. 1 shows the overall configuration of an image forming apparatus of the present invention, and in particular, a tandem type digital color printer. An image forming apparatus shown in FIG. 1 includes an image processing system 10 that forms an image corresponding to gradation data of each color, a sheet conveyance system 40 that conveys a recording medium (a sheet member such as paper), and the like. For example, an image processing apparatus 50 that is connected to a personal computer or an image reading apparatus and performs predetermined image processing on received image data, and a controller 55, and a document image from a double-sided original or a single-sided original And an image reading device 60 for reading. In addition, the image processing system 10 and a fixing unit 29 described later are provided with a control unit 80 that controls the operation of each device (each unit).

  The image processing system 10 includes four image forming units 11Y, 11M, yellow (Y), magenta (M), cyan (C), and black (K) arranged in parallel at a certain interval in the horizontal direction. 11C and 11K. The image forming units 11Y, 11M, 11C, and 11K are transferred onto the intermediate transfer belt 21, and the image forming units 11Y, 11M, 11C, and 11K. An exposure device 30 is provided for forming an electrostatic latent image by exposing the photosensitive member 12 to laser light. Further, the image (toner image) on the recording medium that has been secondarily transferred by the transfer unit 20 is fixed to the main body 1 on the recording medium using heat and pressure roller 29a and pressure roller 29b, for example, using heat and pressure. A fixing device 29 is provided. Further, each of the image forming units 11Y, 11M, 11C, and 11K includes a developing device 13 and a small charger 14 (FIG. 2) called a BCR (Bias Charge Roll). In addition, toner cartridges 19Y, 19M, 19C, and 19K are provided for supplying toner of each color to the developing devices 13 of the image forming units 11Y, 11M, 11C, and 11K.

  Each color toner supplied to the toner cartridges 19Y, 19M, 19C, and 19K is manufactured by melting, kneading, pulverizing, classifying, or polymerizing a polyester resin, a colorant, a charge control material, and the like. Further, in order to transfer the toner image formed on the photosensitive member satisfactorily onto the intermediate transfer member or the recording medium, an external additive having releasability is added.

  The transfer unit 20 includes a drive roller 22 that drives an intermediate transfer belt 21 that is an intermediate transfer member, a tension roller 23 that applies a constant tension to the intermediate transfer belt 21, and a secondary transfer of the superimposed toner images of each color to a recording medium. For this purpose, a backup roller 24 and a cleaning device 25 for removing residual toner and the like existing on the intermediate transfer belt 21 are provided. The intermediate transfer belt 21 is wound around the drive roller 22, the tension roller 23, and the backup roller 24 with a constant tension, and is driven to rotate by a dedicated drive motor (not shown) having excellent constant speed. The drive roller 22 is driven to circulate at a predetermined speed in the direction of the arrow. As the intermediate transfer belt 21, for example, a belt whose resistance is adjusted with a belt material (rubber or resin) that does not cause charge-up is used. The cleaning device 25 includes a cleaning brush 25a and a cleaning blade 25b, and removes residual toner, paper dust, and the like from the surface of the intermediate transfer belt 21 after the toner image transfer process is completed, and performs the next image forming process. It is comprised so that it may prepare for.

  In addition to a semiconductor laser and a modulator (not shown), the exposure unit 30 includes a polygon mirror 31 that deflects and scans laser light emitted from the semiconductor laser. The sheet conveyance system 40 includes a sheet feeding device 41 that loads and supplies a recording medium (hereinafter referred to as “paper”) on which an image is recorded, a nudger roller 42 that picks up and supplies paper from the sheet feeding device 41, and a nudger roller 42. A feed roller 43 that separates and conveys the supplied paper one by one, and a conveyance path 44 that conveys the paper separated by the feed roller 43 toward the image transfer unit. In addition, a registration roller 45 that conveys the paper conveyed through the conveyance path 44 in a timely manner toward the secondary transfer position, and a backup roller 24 that is provided at the secondary transfer position and press-contacts the image on the paper. A secondary transfer roller 46 for secondary transfer is provided. Further, a discharge tray for stacking paper discharged after the toner image is fixed by the fixing device 29 is provided.

  FIG. 2 is a diagram for explaining various sensors built in the main body 1 of the image forming apparatus. As shown in FIG. 2, each developing device 13 of the image forming units 11Y, 11M, 11C, and 11K detects the internal toner density and keeps the toner density (mixing ratio of toner and magnetic carrier) constant. An ATC (Auto Toner Concentration Control) sensor (toner density detection sensor) 91 is attached. A patch sensor 90 that measures the toner image on the photoconductor 12 is attached downstream of the developing device 13. A patch sensor 92 for measuring the toner image on the intermediate transfer belt 21 is attached to the downstream side of the image forming unit 11K and the upstream side of the tension roller 23. Further, a patch sensor 93 for measuring a toner image on paper is attached in front of the fixing device 29, and a patch sensor 94 for measuring a toner image fixed on paper is attached between the fixing device 29 and the discharge tray. ing.

  Next, the operation of the image forming apparatus shown in FIG. 1 will be described. When an instruction to perform a printing simulation is issued by a personal computer or the like, first an “exposure energy control mode” described later is entered. After performing the exposure energy control described later, the image data received from the personal computer is output to the exposure device 30.

  The exposure device 30 emits laser light emitted from a semiconductor laser (not shown) to the polygon mirror 31 through an f-θ lens (not shown) in accordance with the input image data. In the polygon mirror 31, the incident laser light is modulated in accordance with gradation data of each color, deflected and scanned, and image forming units 11Y, 11M, 11C, and 11K through an imaging lens and a plurality of mirrors (not shown). The photosensitive drum 12 is irradiated. On the photosensitive drums 12 of the image forming units 11Y, 11M, 11C, and 11K, the surface charged by the charger 14 is subjected to scanning exposure to form an electrostatic latent image. The formed electrostatic latent image is developed as a toner image of each color of yellow (Y), magenta (M), cyan (C), and black (K) in each of the image forming units 11Y, 11M, 11C, and 11K. The

  The toner images formed on the photosensitive drums 12 of the image forming units 11Y, 11M, 11C, and 11K are transferred onto an intermediate transfer belt 21 that is an intermediate transfer member. If necessary, reflected light on the photosensitive member is measured by the patch sensor 90, and reflected light on the intermediate transfer belt is measured by the patch sensor 92.

  On the other hand, in the sheet conveying system 40, the nudger roller 42 rotates in synchronization with the image formation timing, and a predetermined size of paper is supplied from the paper feeding device 41. The sheets separated one by one by the feed roller 43 are conveyed to the registration roller 45 through the conveyance path 44 and are temporarily stopped. Thereafter, the registration roller 45 rotates in accordance with the movement timing of the intermediate transfer belt 21 on which the toner image is formed, and the paper is conveyed to the secondary transfer position formed by the backup roller 24 and the secondary transfer roller 46. On the paper conveyed from the lower side to the upper side at the secondary transfer position, the toner images in which the four colors are multiplexed are sequentially transferred in the sub-scanning direction using the press contact force and a predetermined electric field. The paper on which the toner images of the respective colors are transferred is subjected to a fixing process by heat and pressure by the fixing device 29. If necessary, the reflected light before the fixing process by the patch sensor 93 or after the fixing process by the patch sensor 94 is measured. The paper on which the toner image is transferred is discharged to a discharge tray 47.

  FIG. 3 illustrates a configuration of the control unit according to the first embodiment. As shown in FIG. 3, the control unit 80 includes an information acquisition unit 101 that acquires color standard information sent from a personal computer, a first storage unit 102 that stores reproduction area information of various color standards, and an exposure. A second storage unit 103 for storing exposure energy, which is the energy of laser light emitted from the semiconductor laser in the device 30, and color reproduction information at a dot area ratio of 100% of the basic color; a first storage unit 102; A reproducibility acquisition unit 104 that calculates a gamut cover ratio, which will be described later, which is color reproducibility for each exposure energy using information from the second storage unit 103, and an exposure control unit 105 that controls exposure energy are provided.

  Next, the operation in the exposure energy control mode shown in FIG. 3 will be described using the flowchart of FIG. The operator designates color standard information to be simulated via a personal computer or the like. As the color standard information, for example, “Japan Color 2001” or “art paper” as shown in FIG. 5, it is desirable to clearly know the type of ink and printing paper. In addition, DIC and PANTONE which are printing color standards may be used.

  In the control unit 80, the information acquisition unit 101 receives the color standard information (S201) and transmits it to the reproducibility acquisition unit 104. The reproducibility acquisition unit 104 stores the color standard information from the information acquisition unit 101, the color standard gamut outermost color space coordinate information (S202) stored in the first storage unit 102, and the second storage unit 103. The stored color space coordinate information is obtained (S203).

FIG. 6A shows an example of a table stored in the first storage unit 102. Reproduced colors for CMYK halftone dot area ratio (%) are described in color space coordinate information. FIG. 6B shows an example of the table 1 stored in the second storage unit 103. For each CMYK exposure energy (E1 to E3), the corresponding basic color (C , M, Y, K, R, G, B), paper white (W), and black point (B) color space coordinate information. In this embodiment, the L * a * b * color system which is CIE 1976 is used as the color space coordinates.

  Next, the reproducibility acquisition unit 104 calculates a gamut coverage described later for each exposure energy (S204), and transmits the calculation result to the exposure control unit 105. The exposure control unit 105 selects the exposure energy that maximizes the gamut coverage from the received calculation result (S205), transmits the result to the exposure device 30 (S206), and ends the exposure energy control mode.

  Thereafter, when outputting the image data received from the personal computer, the exposure device 30 emits laser light with the intensity set in the exposure energy control mode.

  Next, the coordinates of the gamut outermost contour in the color space will be described with reference to FIGS. FIG. 7A shows a gamut outermost contour of a certain color standard, and FIG. 7B shows a gamut outermost contour of the image forming apparatus. In the example of FIG. 6A, since the first storage unit 102 stores the reproduction colors for the CMYK halftone dot area ratio, the outermost shape of the gamut in FIG. 7A is like a rugby ball. is there. On the other hand, in the example of FIG. 6B, the table 1 stored in the second storage unit 103 describes the reproduction color for the dot area ratio of 100%. The shape is a shape in which two hexagonal thrusts are stacked one above the other. In the figure, WP indicates a white point that is white of paper, and BP indicates a black point that is the minimum lightness that can be reproduced. The coordinates of the white point depend on the paper used, and the coordinates of the black point depend on the color material used, the total amount regulation value, and the halftone processing method.

  Next, calculation of the gamut cover ratio will be described with reference to FIG. FIG. 7C shows the a * b * plane when L * = 50. Solid lines Y1, R1,... G1 are color standard gamut outermost contours, and dotted lines Y2, R2,... G2 are gamut outermost contours of the image forming apparatus. The gamut coverage is the area of the gamut outermost outline of the color standard at a certain lightness (for example, L * = 50) (the area consisting of Y1, R1, M1, B1, C1, G1, Y1 in FIG. 7C). ), The area of the outermost gamut of the image forming apparatus (area consisting of Y2, R2, M2, B2, C2, G2, and Y2) is calculated, and a value obtained by adding all brightness values (for example, from L * = 10) It is calculated in increments of ΔL * = every 5 steps until L * = 90. In the example of FIG. 7C, the gamut outermost contour of the color standard is a polygon. Therefore, the area of the outermost gamut contour is triangular (Y1, O, YR1), triangular (YR1, O, YR2), triangular (YR2). , O, YR3)... And the triangular area may be added. Similarly, the area of the outermost gamut of the image forming apparatus is calculated by adding triangles (Y2, O, R2), triangles (R2, O, M2), triangles (M2, O, B2). If there is no data on brightness, a value interpolated from neighboring data may be used. The gamut coverage is calculated by performing the above processing.

  In this way, in the image forming apparatus, it is possible to stably create an image capable of expressing the reproduction color gamut of the color standard to the maximum by reflecting the control result of the exposure energy on the controller using the gamut coverage. It is.

  As described above, in the first embodiment, in the image forming apparatus, a reproduction target color standard is selected, a gamut cover ratio for the color reproduction range of the color standard is calculated, and exposure energy is set so that the gamut cover ratio is maximized. By controlling this, the solid density can be set. That is, by controlling the exposure energy based on the gamut coverage, color reproduction close to the target color standard can be obtained.

  According to the present invention, since the exposure energy is controlled so that the reproducibility of the color reproduced by the image forming apparatus is maximized with respect to the color belonging to the color standard representing the color gamut of printing, the color standard An image forming apparatus capable of obtaining a color reproduction range close to.

  According to the present invention, since the color reproducibility as the control condition is evaluated by the coverage with respect to the gamut of the color standard, it is possible to provide an image forming apparatus capable of obtaining a color reproduction range close to the color standard.

  According to the present invention, it is possible to provide an image forming apparatus that can obtain a gamut coverage, which is color reproducibility, with a minimum amount of information.

  According to the present invention, since the table 1 for associating the color characteristics of the image forming apparatus and the control target is built in, it is possible to omit the work of outputting an image and performing color measurement, and to provide an image forming apparatus that can be easily controlled. it can.

  According to the present invention, it is possible to provide an image forming apparatus capable of obtaining optimum color reproduction according to the contents of an image.

  According to the present invention, it is possible to provide an image forming apparatus capable of obtaining an optimum color reproduction according to a color standard.

  In the second embodiment, an example in which the exposure energy varies with time will be described. A patch sensor is used to estimate the toner adhesion amount on the photosensitive member or transfer belt, and appropriate control is performed even when the exposure energy fluctuates over time. In this embodiment, an example in which the toner adhesion amount on the photosensitive member is estimated by converting the output from the patch sensor 90 into the toner adhesion amount will be described.

  FIG. 8 illustrates a configuration of the control unit according to the second embodiment. As shown in FIG. 8, the control unit 80 includes an information acquisition unit 101 that acquires color standard information sent from a personal computer, a first storage unit 102 that stores reproduction area information of various color standards, and a photosensitive unit. Using the information from the second storage unit 103 storing the toner adhesion amount on the body and the color reproduction information at the halftone dot area ratio of 100% of the basic color, and the information from the first storage unit 102 and the second storage unit 103, A reproducibility acquisition unit 104 that calculates a gamut coverage described later, which is color reproducibility for each exposure energy, and an exposure control unit 105 that controls the exposure energy are provided.

  Further, the controller 80 receives an output from the patch sensor 90 and estimates the amount of adhesion on the photoconductor, and the exposure energy of the laser beam emitted from the exposure device 30 and the amount of adhesion on the photoconductor. A table rewriting unit 107 that rewrites the relationship between and the third storage unit 108 that stores the relationship between the toner adhesion amount on the photosensitive member and the exposure energy.

  Next, the operation in the exposure energy control mode shown in FIG. 8 will be described using the flowchart of FIG. When the exposure energy control mode is entered, an operation for obtaining the relationship between the exposure energy of the laser beam irradiated to the photosensitive member first and the amount of adhesion on the photosensitive member is started. First, the table rewriting unit 107 obtains the exposure energy of the laser light applied to the photoconductor based on the output from the exposure device 30 (S301). Next, the adhesion amount conversion unit 106 obtains an output from the patch sensor 90 (S302), and obtains the toner adhesion amount on the photoconductor. The adhesion amount conversion unit 106 holds a table of toner adhesion amounts with respect to sensor output values as shown in FIG. 10, and the adhesion amount estimation is performed using the table to obtain the adhesion amount value (S303). The table rewriting unit 107 creates a table representing the relationship between the exposure energy and the adhesion amount based on the output from the adhesion amount conversion unit 106 (adhesion amount) and the output from the exposure device 30 (exposure energy) described above. If necessary, the old table (table 2) stored in the third storage unit 108 is rewritten (S304) and stored in the third storage unit (S305). Thus, in Table 2, the relationship between the exposure energy of the laser beam applied to the photoconductor and the amount of adhesion on the photoconductor was obtained.

  Next, the operator designates color standard information to be simulated via a personal computer or the like. In the control unit 80, the information acquisition unit 101 receives the color standard information (S306) and transmits it to the reproducibility acquisition unit 104. The reproducibility acquisition unit 104 stores the color standard information from the information acquisition unit 101, the color standard gamut outermost color space coordinate information (S307) stored in the first storage unit 102, and the second storage unit 103. The stored color space coordinate information is obtained (S308).

  The second storage unit 102 stores reproduction color information corresponding to the amount of CMYK toner adhering to the photoconductor as a table 1, and a color space of basic colors, white paper, and black points with a dot area ratio of 100%. Coordinate information is described. Next, the reproducibility acquisition unit 104 calculates a gamut cover ratio for each toner adhesion amount (S309), and transmits the calculation result to the exposure control unit 105. The exposure control unit 105 selects an adhesion amount that maximizes the gamut coverage from the received calculation result (S310), and determines the corresponding exposure energy with reference to the table 2 held in the third storage unit. (S311). The result is transmitted to the exposure device 30 (S312), and the exposure energy control mode is terminated.

  Thereafter, the operator designates color standard information to be simulated via a personal computer or the like. When outputting the image data received from the personal computer, the exposure device 30 emits laser light with the intensity set in the exposure energy control mode.

  As described above, in the second exemplary embodiment, in the image forming apparatus, the table 2 representing the relationship between the exposure energy and the toner adhesion amount on the photosensitive member is first held, so that even when the exposure energy varies with time. By appropriately controlling the exposure energy, a color reproduction close to the target color standard can be obtained.

  In this embodiment, the toner adhesion amount on the photosensitive member is estimated using the patch sensor 90. In addition, the patch sensors 92, 93, and 94 are used to estimate the toner adhesion amount on the intermediate transfer belt 21 and before and after the fixing process. The toner adhesion amount on the paper may be estimated. In this case, the toner adhesion amount described in the table stored in the adhesion amount conversion unit 106 or the third storage unit 108 is the toner amount adhering to the target location.

  In the present embodiment, the table 1 stored in the second storage unit is the color reproduction space information of the basic color and the halftone dot area rate of 100%. However, the table 1 is not limited to 100% and various halftone dot area rates. The table 1 may be configured by the combination. In that case, the shape of the outermost outline of the gamut of the image forming apparatus is not a combination of hexagonal guesses as shown in FIG. 7B, but is a polyhedron. In this case, when calculating the gamut coverage, there may be no data on brightness, but a value interpolated from neighboring data may be used.

  In the present embodiment, the exposure energy is controlled so that the color standard gamut coverage is maximized in the entire color space. However, for example, it may be assumed that priority is given to color reproduction only in the halftone area. In such a case, you may perform processing such as calculating the gamut coverage with a certain level of brightness, or conversely, if you want to emphasize color reproduction in the shadow area, May be calculated.

  Furthermore, when the reproduction color to be emphasized, such as a memory color, is known in advance, the gamut coverage of the color reproduction area may be calculated. For example, object discrimination or face recognition processing of an image input from a personal computer may be performed to estimate important colors used in the image, and a reproduction color gamut to be emphasized may be obtained in advance.

  According to the present invention, since the table 2 for associating the color characteristics of the image forming apparatus and the control target is built in, it is possible to omit the work of measuring the color by outputting an image, and to provide an image forming apparatus that can be easily controlled. it can.

  According to the present invention, it is possible to provide an image forming apparatus capable of obtaining optimum color reproduction according to the contents of an image.

  FIG. 11 shows a system configuration example using a recording medium storing a program for executing image formation control and fixing control in the above-described image forming apparatus. This processing system includes a computer 400 such as a workstation, a display 401, and a printer 403 as an image forming apparatus. The computer 400 realizes the function of the control unit 80 described in the first embodiment, and includes an arithmetic processing device 410, a program reading device 411, a keyboard 412, a mouse 413, and the like.

  The arithmetic processing unit 410 executes various commands and controls the entire apparatus, a CPU 421, a program executed by the CPU 421, a ROM 422 for storing other fixed data, a RAM 423 for temporarily storing image data and the like, and a large amount A DISK 407 such as a hard disk as a storage device and a NIC 424 for communicating with devices on the network are provided, and each is connected via a bus. The program reading device 411 is a storage medium storing various program codes, such as a flexible disk, hard disk, optical disk (CD-ROM, CD-R, CD-R / W, DVD-ROM, DVD-RAM, etc.), magneto-optical. An apparatus for reading a program code stored in a disk, a memory card or the like, that is, a flexible disk drive, an optical disk drive, a magneto-optical disk drive, or the like.

  The program code stored in the storage medium is read by the program reading device 411 and then stored in the DISK 407 or the like. The CPU 421 executes the above-described image processing by executing the program code stored in the DISK 407. I can do it.

  Further, when executing the program code read from the computer 400, based on the instruction of the program code, a part of the actual processing in the OS (operating system) or device driver running on the computer 400, or the like You can also do everything. Further, after the program code read from the storage medium is written in a memory provided in a function expansion card (not shown) inserted in the computer 400 or a function expansion unit connected to the computer 400, the program code is instructed. Based on this, it is also possible to cause a CPU or the like provided in the function expansion card or function expansion unit to execute part or all of the actual processing. That is, the present invention can be configured as a printer driver or a program that causes a computer to implement the image control method according to the present invention. Further, the program for realizing the functions and the like of the embodiments of the present invention may be provided from a server by communication via a network.

30 Exposure unit 80 Control unit 101 Color information acquisition unit 102 First storage unit 103 Second storage unit 104 Reproducibility acquisition unit 105 Exposure control unit

Japanese Patent Laid-Open No. 2003-149796

Claims (13)

An image forming apparatus for simulating an arbitrary color standard, comprising exposing means for exposing a photosensitive member to light to form an electrostatic latent image, and forming the formed electrostatic latent image as a toner image. Reproduced by the developing means, the transfer means for transferring the toner image onto the recording medium, the fixing means for fixing the toner image on the recording medium, and the image forming apparatus for colors belonging to the color reproduction range of the color standard. An image forming apparatus comprising: an acquisition unit that acquires a gamut cover ratio; and an exposure control unit that controls exposure energy in the exposure unit so that the gamut cover ratio obtained by the acquisition unit is maximized. . In obtaining the gamut coverage , at least one of basic color information having a halftone dot area ratio of 100% is used, and at least one of paper information or black point information is used. The image forming apparatus according to claim 1. The image forming apparatus according to claim 2 , wherein the basic color is a primary or secondary color. And storing means for storing a first table defining a correspondence relationship between reproduction color information of basic colors and exposure energy, wherein the acquisition means acquires a gamut cover ratio for each exposure energy, and performs the exposure control. 2. The image forming apparatus according to claim 1, wherein the means controls exposure energy with reference to a gamut coverage obtained by the acquisition means. From the measuring means for measuring the toner adhesion amount on the photosensitive member, the intermediate transfer member, or paper, the storage means storing the second table defining the correspondence between the exposure energy and the toner adhesion amount, and the measurement means Rewriting means for updating the second table in accordance with the output of the exposure table, and the exposure control means refers to the gamut coverage obtained by the acquisition means and the exposure energy by referring to the second table. The image forming apparatus according to claim 1, wherein the image forming apparatus is controlled. When emphasizing the reproducibility of colors belonging to highlights, the acquisition of the gamut coverage rate uses at least the basic color information of a dot area ratio of 100% and the information of paper as a recording medium. The image forming apparatus according to claim 1 or 2 . 2. When the reproducibility of colors belonging to shadows is emphasized, basic color information with at least a halftone dot area rate of 100% and further black point information are used in obtaining the gamut coverage. Or the image forming apparatus according to 2 ;   The image forming apparatus according to claim 1, wherein the exposure energy is controlled according to a type of an object of an image to be output and a color to be used.   The image forming apparatus according to claim 1, wherein the exposure energy is controlled according to at least the type of the color standard. The color standard is at least printing color standard Japan Color, DIC, image forming apparatus according to claim 1 or 9, wherein is any one of PANTONE. An image forming method for simulating an arbitrary color standard, an exposure procedure for forming an electrostatic latent image by exposing light to a photoconductor, and forming the formed electrostatic latent image as a toner image Reproduced by the development procedure, the transfer procedure for transferring the toner image onto the recording medium, the fixing procedure for fixing the toner image on the recording medium, and the image forming method for colors belonging to the color reproduction range of the color standard. acquisition procedures and, as gamut coverage obtained by the acquisition procedure is maximum, the image forming method characterized by comprising an exposure control step of controlling the exposure energy in the exposure steps to acquire that gamut coverage . The program for making a computer implement | achieve the image forming method of Claim 11 . A computer-readable storage medium describing a program for causing a computer to implement the image forming method according to claim 11 .

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