JP5672867B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus using a juxtaposed image forming method for reproducing a full color image by additive color mixing and subtractive color mixing.

  Usually, in full-color printing such as electrophotographic printing, inkjet printing, and offset printing, first, a color original image to be printed is separated into colors of cyan, magenta, yellow, and black (hereinafter referred to as “C, M, Y, BK”). A plate is created, and color reproduction in printing (especially intermediate color reproduction) is realized by superimposing (subtractive color mixing) the three primary colors of cyan (C), magenta (M), and yellow (Y). For example, printing of red (R), green (G), and blue (B) is realized by stacked printing of M and Y, C and Y, and C and M, respectively. In color printing, it is generally known to use a black plate (BK plate) from the viewpoints of reducing the usage amount of C, M, and Y developers and emphasizing the tone (color tone and density gradation) of a printed image. It has been.

  In addition to the subtractive color mixture, the intermediate color reproduction method includes a method in which C, M, and Y images are juxtaposed to achieve additive color mixing. This side-by-side printing method has the advantage that the amount of developer and ink required for printing can be reduced because images of each color are not overlapped, and all colors are expressed in a single layer. As an electrophotographic printer, CPS700 manufactured by Oce is used. Adopts this method.

  On the other hand, a problem with additive color mixing in side-by-side printing is that the colors are not overlapped, resulting in low color saturation and a small color reproduction range. As a method of expanding the reproduction area in this side-by-side layout printing, a method of expressing halftones by changing the number and arrangement of dots in a dot matrix is disclosed in Patent Document 1, and four colors of high-saturation monochrome blue toner and CMY toner are used. A toner side-by-side printing method is disclosed in Patent Document 2. Further, Patent Document 3 discloses a method of physically mixing a part of each color dot to improve saturation by subtractive color mixture.

A characteristic of the side-by-side image formation is that the color gamut differs depending on the light diffusion characteristics of a recording medium such as paper, and in particular, a difference occurs in the hue of intermediate colors. This is because subtractive color mixing caused by light diffusion in the recording medium occurs at different color boundaries in addition to additive color mixing by reflected light from each single color image in color mixing by juxtaposed image formation. The degree of subtractive color mixing due to light diffusion in the recording medium differs depending on the light diffusion characteristics of the recording medium, and in particular, in the side-by-side arrangement image formation, the influence on the color gamut increases. For this reason, the methods relating to the side-by-side image formation described in Patent Documents 1 to 3 described above have a problem that color reproducibility (particularly color saturation) varies greatly depending on the recording medium used.
An object of the present invention is to provide color variation caused by a difference in light scattering characteristics of a recording medium to be used in image formation using juxtaposed image formation, in particular, instability of intermediate color, and light scattering of the recording medium to be used. An object of the present invention is to provide an image forming apparatus that provides stable color reproducibility by setting image forming conditions in accordance with characteristics.

The image forming apparatus according to the present invention forms a color image by side-by-side image formation using at least three primary colors of cyan, magenta, and yellow and a black developer. An intermediate color that uses two colors of the agent, realizes an intermediate color by using the additive color mixture and the subtractive color mixture of the two colors, and has a ratio between the additive color mixture and the subtractive color mixture according to the light diffusion characteristics of the recording medium used. It is characterized in that the printing area ratio of the two color dots forming the image and the overlapping ratio of the adjacent dots of each color are changed.
The image forming apparatus according to the present invention is characterized in that the change in the overlap rate at the adjacent portion is to change the size of the dot at the adjacent portion .
The image forming apparatus according to the present invention includes a measuring unit that measures the light diffusion characteristics of the recording medium. The measuring unit measures the light diffusion characteristics of the recording medium before printing, and based on the measurement value by the measuring means, The printing area ratio of the two color dots forming the intermediate color image and the overlapping ratio of the adjacent dots of each color are set.
The image forming apparatus according to the present invention, a storage unit for storing the measurement result of the light diffusion properties of the recording medium measured by the measuring means for measuring the light diffusion properties of the recording medium, the light diffusing characteristics stored in the storage unit In accordance with the measurement result, the printing area ratio of the two color dots forming the intermediate color image and the overlapping ratio of the adjacent dots of each color are changed .
The image forming apparatus according to the present invention, has a hue measured colorimetric means for measuring a plurality of evaluation patterns of varying dot printing area ratio of two colors to form a neutral image of a color image, hue measuring colorimetric means The printing area ratio of the two color dots forming the intermediate color image is changed according to the measured result .
In the image forming apparatus according to the present invention, hue measurement colorimetry means for measuring a plurality of evaluation patterns in which the ratio of the two- color dot printing areas forming an intermediate color image of a color image is measured, and light diffusion characteristics of a recording medium are measured A measuring unit that performs hue measurement by the hue measuring and color measuring unit and a printing area ratio of two color dots that form an intermediate color image according to the light diffusion characteristics of the storage medium measured by the measuring unit and adjacent portions of each color dot The overlap ratio is changed for each set printing amount.

The present invention is considered as an image forming method as follows.
As an image forming method, a color image is formed by side-by-side image formation using at least three primary colors of cyan, magenta, and yellow and a black developer. Using two colors, the additive color and subtractive color mixture of the two colors are used together to realize an intermediate color, and an intermediate color image is formed with the ratio of the additive color mixture and the subtractive color mixture according to the light diffusion characteristics of the recording medium used. The printing area ratio of the two color dots and the overlapping ratio of the adjacent dots of each color are changed.
In the image forming method, the change in the overlapping rate at the adjacent portion may be performed by changing the dot size at the adjacent portion .
In the image forming method, when the image forming apparatus includes a measuring unit that measures the light diffusing characteristic of the recording medium, the measuring unit measures the light diffusing characteristic of the recording medium before printing, and the measured value by the measuring unit is measured. The print area ratio of the two color dots forming the intermediate color image of the color image and the overlapping ratio of the adjacent dots of each color may be set based on the above.
In the image forming method, when the image forming apparatus includes a storage unit, the measurement result of the light diffusion characteristic of the recording medium obtained by measuring the light diffusion characteristic of the recording medium by a measuring unit outside the apparatus is stored in the storage unit. The data may be used.
In the image forming method, when the image forming apparatus includes hue measurement and colorimetry means, the hue measurement and colorimetry means uses the plurality of evaluations in which the ratio of the two- color dot printing areas for forming an intermediate color image of the color image is changed. A pattern may be measured.
In an image forming method, a hue measurement color measurement unit that measures a plurality of evaluation patterns in which a ratio of dot printing areas of two colors forming an intermediate color image of a color image is changed, and a measurement unit that measures a light diffusion characteristic of a recording medium In the case where the image forming apparatus is provided, the hue measurement by the hue measurement color measurement unit and the print area ratio of the two color dots that form an intermediate color image according to the light diffusion characteristics of the storage medium measured by the measurement unit and the dot of each color You may change the overlap rate in an adjacent part for every set printing amount or for every predetermined time.

  According to the present invention, the intermediate color of the color image is formed by using two of the developers, realizing the intermediate color by using the additive color mixture and the subtractive color mixture of the two colors, and the light diffusion characteristics of the recording medium to be used Accordingly, the ratio between the additive color mixture and the subtractive color mixture is changed, so that the color reproduction range depending on the type of the recording medium used, particularly the difference between the intermediate colors can be reduced, and stable color reproducibility can be ensured.

1 is a schematic diagram illustrating one embodiment of an image forming apparatus according to a first embodiment of the present invention. (A) is explanatory drawing of the light reflection path | route of a completely juxtaposed printed matter, (b) is a top view of (a). (A) is explanatory drawing of the light reflection path | route of the completely juxtaposed printed matter at the time of color misalignment, (b) is a top view of (a). (A) is explanatory drawing of the light reflection path | route of the perfect juxtaposition printed matter at the time of partial superimposition of the adjacent dot in this form, (b) is a top view figure of (a). It is the schematic of a light-diffusion characteristic measurement means. It is a figure which shows the example of a measurement of a beam profile. It is a cross-sectional schematic diagram of an intermediate color image (evaluation pattern) when the dot area ratio is changed from 50% to 100%. It is a figure which shows the example of a measurement result of the light-diffusion characteristic coefficient N of a recording medium, and the saturation C of an evaluation chart. It is a figure which shows the relationship between a dot area ratio and saturation. It is a figure which shows the relationship between the light-diffusion characteristic count N and the dot printing area rate X. FIG. It is the schematic which shows one form of the image forming apparatus which concerns on the 2nd Embodiment of this invention. It is the schematic which shows one form of the image forming apparatus which concerns on the 3rd Embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
The image forming apparatus shown in FIG. 1 is a tandem type electrophotographic image forming apparatus. Reference numeral 1 denotes an apparatus main body of a tandem type color copier as an image forming apparatus, reference numeral 2 denotes a writing unit that emits laser light based on input image information, and reference numeral 3 denotes a document conveying unit that conveys a document D to a document reading unit 4. Reference numeral 4 denotes a document reading unit that reads image information of the document D, reference numeral 7 denotes a paper feeding unit that accommodates a recording medium 200 such as transfer paper, reference numeral 9 denotes a registration roller that adjusts the conveyance timing of the recording medium 200, and reference numeral 11Y. , 11M, 11C, and 11BK are photosensitive drums that are image carriers on which toner images of the respective colors (yellow, magenta, cyan, and black) are formed. Reference numeral 12 denotes the photosensitive drums 11Y, 11M, 11C, and 11BK. A charging unit for charging, reference numeral 13 is a developing unit for developing electrostatic latent images formed on the photosensitive drums 11Y, 11M, 11C, and 11BK, and reference numeral 15 is a photosensitive member. Shows ram 11Y, 11M, 11C, a cleaning unit for collecting respective untransferred toner on 11BK, respectively.

  The photosensitive drums 11Y, 11M, 11C, and 11BK, the charging units 13, the developing units 14, and the cleaning units 15 are respectively incorporated in the casings for the respective colors to form process units for the respective colors. Below each process unit, a transfer belt 17 that is a transfer member wound around a plurality of rollers is disposed so as to face each photosensitive drum. The transfer belt 17 conveys the recording medium 200 so that toner images of a plurality of colors are carried on the recording medium 200 in an overlapping manner. Inside the transfer belt 17, a transfer member serving as a transfer member for transferring the toner images formed on the photoconductive drums 11Y, 11M, 11C, and 11BK on the recording medium 200 in a position facing each photoconductive drum. Each of the bias rollers 14 is positioned.

  Reference numeral 16 denotes a transfer belt cleaning unit that cleans the transfer belt 17, and reference numeral 19 denotes a fixing device that fixes a toner image (unfixed image) on the recording medium 200. In this embodiment, the fixing device 19 employs an electromagnetic induction heating method, but other types of heating may be used.

Hereinafter, an operation during normal color image formation in the image forming apparatus will be described.
First, the document D is transported from the document table in the direction of the arrow in the drawing by the transport rollers of the document transport unit 3 and placed on the contact glass 5 of the document reading unit 4. Then, the document reading unit 4 optically reads the image information of the document D placed on the contact glass 5. Specifically, the document reading unit 4 scans the image of the document D on the contact glass 5 while irradiating light emitted from an illumination lamp. Then, the light reflected by the document D is imaged on a known color sensor via a mirror group and a lens. The color image information of the document D is read for each RGB (red, green, blue) color separation light by the color sensor, and then converted into an electrical image signal. Further, based on RGB color separation image signals, a known image processing unit (not shown) performs color conversion processing, color correction processing, spatial frequency correction processing, and the like, so that yellow, magenta, cyan, and black color images are obtained. get information.
Then, the image information of each color of yellow, magenta, cyan, and black is transmitted to the writing unit 2. From the writing unit 2, laser light (exposure light) based on the image information of each color is emitted toward the corresponding photosensitive drums 11Y, 11M, 11C, and 11BK.
On the other hand, the four photosensitive drums 11Y, 11M, 11C, and 11BK are rotated clockwise in FIG. Then, the surface of each photosensitive drum is uniformly charged at a portion facing each charging unit 12 (charging process). Thus, a charged potential is formed on each photoconductor drum. The surface of each charged photosensitive drum reaches the irradiation position of each laser beam.

  From the writing unit 2, laser light corresponding to the image signal is emitted from four light sources corresponding to each color. Each laser beam has a resolution of 2400 dpi and passes through different optical paths for each of the yellow, magenta, cyan, and black color components (exposure process).

Laser light corresponding to the yellow component is irradiated on the surface of the first photosensitive drum 11Y from the left side of the drawing. At this time, the yellow component laser light is scanned in the rotation axis direction (main scanning direction) of the photosensitive drum 11Y by a polygon mirror that rotates at high speed. Thus, an electrostatic latent image corresponding to the yellow component is formed on the photosensitive drum 11Y charged by the charging unit 12.
Similarly, the laser beam corresponding to the magenta component is irradiated onto the surface of the second photosensitive drum 11M from the left side of the paper, and an electrostatic latent image corresponding to the magenta component is formed. The cyan component laser light is applied to the surface of the third photosensitive drum 11C from the left side of the paper, and an electrostatic latent image of the cyan component is formed. The black component laser beam is applied to the surface of the fourth photosensitive drum 11BK from the left side of the paper, and an electrostatic latent image of the black component is formed.

The surface of each photoconductive drum on which the electrostatic latent image of each color is formed reaches a position facing the developing unit 13, and each color toner is supplied from each developing unit 13 onto each photoconductive drum. The latent image on the drum is developed with each color toner (development process).
The surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK after the development process reach the facing portions of the transfer belt 17, respectively. Here, the transfer bias roller 14 is installed at each facing portion so as to contact the inner peripheral surface of the transfer belt 17. Therefore, the toner images of the respective colors formed on the photosensitive drums 11Y, 11M, 11C, and 11BK are sequentially transferred to the recording medium 200 on the transfer belt 17 at the position of the transfer bias roller 14 (transfer process).

  The surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK after the transfer process reach positions facing the cleaning unit 15, and the untransferred toner remaining on the photosensitive drums is collected by the cleaning unit 15 (cleaning). Process). The surface of each photoconductive drum that has finished the cleaning process passes through a static elimination unit (not shown) and the potential is reset. When this process is finished, a series of image forming processes in the photosensitive drums 11Y, 11M, 11C, and 11BK is finished.

  On the other hand, the recording medium 200 on which the toner of each color on the photosensitive drums 11Y, 11M, 11C, and 11BK is transferred (carrying) travels in the direction of the arrow in FIG. The position facing the separation charger 18 is reached. Then, the charge accumulated in the recording medium 200 is neutralized at a position facing the separation charger 18, and the recording medium 200 is separated from the transfer belt 17 without causing toner dust or the like.

  The surface of the transfer belt 17 from which the recording medium 200 has been separated reaches the position of the transfer belt cleaning unit 16, and deposits adhering to the transfer belt 17 are cleaned and collected by the transfer belt cleaning unit 16.

The recording medium 200 conveyed on the transfer belt 17 is conveyed from the paper supply unit 7 via the registration roller 9 and the like. Specifically, the recording medium 200 fed by the paper feeding roller 8 from the paper feeding unit 7 that houses the recording medium 200 passes through a conveyance guide (not shown) and is then guided to the registration roller 9. The recording medium 200 that has reached the registration roller 9 is conveyed toward the position of the transfer belt 17 at the same timing, and toner images of each color are sequentially transferred. The recording medium 200 onto which the full color toner image has been transferred is separated from the transfer belt 17 and then guided to the fixing device 19. In the fixing device 19, a color image (toner) is fixed on the recording medium 200 at the nip between the fixing roller and the pressure roller. The recording medium 200 after the fixing step is discharged as an output image outside the apparatus main body 1 by a discharge roller (not shown), and a series of image forming processes is completed.
(First embodiment)

  Here, in the full-color image formation according to the present invention, C, M, Y, and K toner images on the transfer belt 17 are arranged in parallel. However, in the completely juxtaposed image in which the toner images (image surfaces 201 and 202) are not superimposed at all as shown in FIG. 2B, the image surfaces 201 and 202 are displayed on the image surfaces 201 and 202 as shown in FIG. Most of the incident light 203 is only the reflected light 204 and 205 from the single color toner layer, and the amount of the light 206 returned from the image surface after propagating between adjacent colors is very small. Therefore, since most of the mixed colors in the side-by-side arrangement image formation are additive mixed colors by the reflected lights 204 and 205, the saturation of intermediate colors such as R (red), G (green), and B (blue) is lowered. Further, in the completely juxtaposed image formation, when color misregistration occurs between the C, M, Y, and K toner images, the support (recording medium) 301 is exposed as shown in FIGS. 3 (a) and 3 (b). As a result, the color variation increases due to the influence of the reflected light 302 from the exposed support 301.

  Therefore, in full-color image formation according to the present invention, as shown in FIGS. 4A and 4B, the constituent dot size of each color is set large so that adjacent portions of each color dot partially overlap. As a result, the color adjacent portion 401 has a superposed structure of C toner and M toner, and the reflected light 402 therefrom becomes a subtractive color mixture light with higher saturation. Therefore, the subtractive color mixture is reflected on the reflected light from the above-described single color toner. By adding to the additive color mixture of 204 and 205, the saturation of the intermediate color can be increased, and as a result, the color reproduction range of the full color image can be expanded. Furthermore, by overlapping the adjacent portions as in the color adjacent portion 401 in FIG. 4, even if a slight color shift occurs, the support (recording medium) 200 can be prevented from being exposed, and stable color reproducibility can be achieved. It can be secured.

  Here, as shown in FIG. 4, in the side-by-side image formation, there is color generation due to subtractive color mixing caused by light diffusion in the recording medium that is the support in the adjacent portion 401 of each color toner image. However, since the subtractive color mixture amount greatly changes in the light diffusion characteristics of the recording medium, the hue (especially saturation) of the intermediate color differs depending on the type of the image support (recording medium) 200 used for printing.

  In this embodiment, the light diffusion characteristics of the recording medium 200 are calculated from the size (diameter) of the diffused light (shadow) of the laser light irradiated perpendicularly to the recording medium and the laser spot diameter not passing through the recording medium. Specifically, a paper light diffusion measuring device 500 serving as a measuring means as shown in FIG. 5 is used. In the paper light diffusion measuring apparatus 500, a laser beam 501 (a semiconductor laser having a wavelength of 780 nm) and a 14-bit digital CCD 502 (hereinafter referred to as “CCD 502”) are arranged to face each other, and the recording medium 200 is arranged between the two. Is configured to do. The CCD 502 is connected to beam profile measuring means 503 that measures the light diffusion characteristics of the recording medium 200.

  FIG. 6 shows an example of a beam profile output by the beam profile measuring unit 503. A beam intensity profile 601 with no recording medium 200 between the laser beam 501 and the CCD 502 and a beam intensity profile 602 transmitted through the recording medium 200 when the recording medium 200 is disposed between the laser beam 501 and the CCD 502 are measured. The light scattering characteristics of the recording medium 200 were defined by the spot diameter ratio. Here, in FIG. 6, the laser spot diameter X 1 and the paper transmission spot diameter X 2 are defined as the width of the light intensity at the 1 / e 2 (13.5%) level of the peak value of the light intensity detected by the CCD 502. The light diffusion coefficient N was X2 / X1 of the ratio.

  In this embodiment, the recording medium 200 uses three types of paper, coated paper (paper A), high-quality paper (paper B), and recycled paper (paper C), and color charts (C, M, and C) for measuring the color gamut. Y, K, R, G, B solid patches) printing was performed. The intermediate colors R, G, B for color chart printing were produced by side-by-side printing of checkered flag patterns of single colors C, M, Y. The checkered flag pattern had 2400 dpi for each color constituent dot and a dot size of 4 dots × 4 dots. In addition, as the intermediate color pattern, six types of patterns having a dot area ratio of two colors to be formed of 50%, 60%, 70%, 80%, 90%, and 100% were printed.

  In this embodiment, as an example of intermediate color correction, color correction between paper types of blue (B created by juxtaposition of M toner dots and C toner dots) will be described.

  FIG. 7 is a schematic cross-sectional view of the six types of print patterns of the intermediate color B. In FIG. 7, a dot area ratio of 50% is a completely juxtaposed arrangement, and a dot area ratio of 100% is a completely overlapped arrangement. FIG. 8 shows the measurement results of the light diffusion characteristic coefficient N of the evaluation chart printed using the sheets A, B, and C and the saturation C of the evaluation chart. FIG. 9 is a diagram illustrating the relationship between the intermediate color B: blue saturation C of the paper A, the paper B, and the paper C and the dot area ratio. As shown in FIGS. 8 and 9, the saturation C of the intermediate color is the same as that of the recording medium 200 to be used in the case of the side-by-side arrangement image formation (the print area ratio of the two colors constituting each is 50%). The greater the light diffusion characteristic coefficient N, the greater the saturation C.

  That is, the intermediate color (saturation) varies depending on the type of the recording medium 200 used. It can also be seen that the saturation increases when the ratio of the printing areas of the two colors constituting each is increased. This is thought to be because the subtractive color mixture area that occurs in the overlapping area has increased. In addition, when the printing area ratio of the two colors is 80% or more, there is almost no color difference due to the difference in the paper type, and it is understood that the saturation when the printing area ratio is 50% to 80% changes substantially linearly. .

  Using the above-mentioned data, when the saturation C of blue B is obtained by second-order polynomial approximation, the light diffusion characteristic count N of the recording medium 200 when obtaining 30, 35, and 40, and the dot printing area ratio X of C and M are arranged. The relationship shown in FIG. 10 is obtained.

  For example, when the saturation C of the intermediate color blue B on the paper A (N = 0.51) and the paper C (0.89) having the most different light diffusion characteristics is set to 35, the printing area ratio X of C and M Is set to 56% for paper A and about 63% for paper C. As a result of printing the paper A and the paper C at the above-mentioned printing area ratio, the saturation C of the intermediate color B is 35.08 for the paper A, and the saturation of the paper C is 35.02. The saturation of red: R and green: G could be corrected by the same method.

  In this embodiment, the paper light diffusion measuring device 500 is installed, for example, upstream or downstream of the registration roller 9 of the image forming apparatus shown in FIG. Diffusion characteristics can be measured. Then, the light diffusion characteristics of the recording medium 200 are measured by the paper light diffusion measuring device 500 before printing, and the print area ratio of a plurality of colors forming an intermediate color image of the color image based on the measurement value by the paper light diffusion measuring device 500 is determined. Set.

  As described above, according to the image forming method and the image forming apparatus of this embodiment, even when the light diffusion characteristics of the recording medium 200 to be used are different, the light diffusion characteristic coefficient N of the recording medium 200 is measured, and the printing area ratio corresponding to the coefficient is measured. By setting, it becomes possible to correct the difference in color reproducibility (saturation) of intermediate colors between paper types. For this reason, the color reproduction range according to the type of the recording medium 200 to be used, particularly the difference between intermediate colors can be reduced, and stable color reproducibility can be ensured. In addition, the change in the ratio of the two colors of additive color mixture and subtractive color mixture performed according to the light diffusion characteristics of the recording medium 200 is performed by changing the print area ratio of a plurality of colors forming an intermediate color image, so that the optical conditions are not changed. In addition, the color reproduction range difference depending on the type of the recording medium 200 can be easily corrected by the image processing in the controller.

In this embodiment, since the optical characteristics of the recording medium itself to be used are measured, for example, it is possible to measure a difference in optical characteristics between lots on the same paper type, and it is possible to correct a stable color reproduction range difference. .
(Second embodiment)

Although the paper light diffusion measuring device 500 shown in FIG. 5 may be installed in the image forming apparatus, the light diffusion characteristics of the paper 200 are substantially the same as long as they are the same type of recording medium. Therefore, in this embodiment, as shown in FIG. 11, the paper diffusion characteristic coefficient N is measured by the paper light diffusion measuring apparatus 500 installed outside the image forming apparatus, and the measured information on the paper light diffusion coefficient N is obtained as follows. The information is stored in advance in a recording medium database 600 serving as a storage unit provided in the image forming apparatus. As a result, the color reproduction correction before the start of printing can be performed in a shorter time. Further, in the configuration of the present embodiment, since the sheet light diffusion measuring device 500 is not included in the image forming apparatus, the cost of the apparatus can be greatly reduced.
(Third embodiment)

In the present embodiment, as shown in FIG. 12, hue measurement and colorimetric means 700 for a plurality of evaluation patterns in which the ratio of dot printing areas of a plurality of colors forming an intermediate color image is changed downstream of a fixing device 19 in the image forming apparatus. The image area ratio and saturation data as shown in FIG. 6 were automatically measured, and the printing area ratio X was corrected regularly (every 2000 pages) by the method described in the first embodiment. As a result, it was confirmed that the intermediate color can be corrected with high accuracy even when the printing environment such as the deterioration of the developer and each photosensitive drum with the passage of time, temperature, and humidity changes.
The sheet light diffusion measurement device 500 and the hue measurement color measurement means 700 are installed in one image forming apparatus, and the light diffusion characteristics and the evaluation pattern (hue measurement) of the recording medium are respectively measured. Correction of the printing area ratio of a plurality of colors forming the image may be performed for each set printing amount. In this case, the color reproduction change due to the deterioration of the developer and the photosensitive drum with the passage of time and the change in engine characteristics due to environmental changes (temperature, humidity) can be reduced, and stable color reproducibility can be secured over a long period of time.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 500 Measuring means 600 Storage part 700 Hue measurement colorimetric means

JP-A-57-129750 JP-A-6-115174 Japanese Patent Application No. 8-523394

Claims (6)

In an image forming apparatus that forms a color image by side-by-side image formation using at least three primary colors of cyan, magenta, and yellow and a black developer.
The intermediate color of the color image is formed by using two of the developers, using the additive color mixture and subtractive color mixture of the two colors to achieve an intermediate color, and depending on the light diffusion characteristics of the recording medium used , An image forming apparatus , wherein a ratio of a print area of two color dots forming an intermediate color image and an overlapping ratio of adjacent dots of each color, which are ratios of the additive color mixture and subtractive color mixture, are changed. The image forming apparatus according to claim 1 , wherein the change in the overlapping rate in the adjacent portion is a change in a dot size in the adjacent portion . Comprising measuring means for measuring the light diffusion characteristics of the recording medium,
The measurement means measures the light diffusion characteristics of the recording medium before printing, and based on the measurement values obtained by the measurement means, the print area ratio of the two color dots that form the intermediate color image and the overlap of adjacent dots of each color 3. The image forming apparatus according to claim 1, wherein a rate is set. A storage unit for storing a measurement result of the light diffusion characteristic of the recording medium measured by a measuring unit that measures the light diffusion characteristic of the recording medium ;
According to the measurement result of the light diffusion characteristic stored in the storage unit, the printing area ratio of the two color dots forming the intermediate color image and the overlapping ratio of the adjacent dots of each color are changed. The image forming apparatus according to claim 1. Have a hue measuring colorimetric means for measuring a plurality of evaluation patterns obtained by changing the two-color dot printing area ratio of forming a neutral image of the color image,
The image forming apparatus according to claim 1 , wherein a printing area ratio of two color dots forming the intermediate color image is changed according to a measurement result measured by the hue measurement and colorimetric unit . Wherein comprising a color measuring color measuring means for measuring a plurality of evaluation patterns and the two-color dot printing area ratio of forming the intermediate color image is changed in color images, the measurement means for measuring the light diffusion properties of the recording medium,
The hue measurement by the hue measurement color measurement means and the printing area ratio of the two color dots forming the intermediate color image according to the light diffusion characteristic of the storage medium measured by the measurement means and the overlapping ratio of the adjacent dots of each color The image forming apparatus according to claim 1, wherein the value is changed for each set printing amount.

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