JPH11225279A - Color image processor and color image forming system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the color image processor and color image forming system that generates an image recoding signal to obtain a print without generation of moire with a sufficient maximum density and excellent granularity so as to attain a high image quantity print. SOLUTION: A maximum black amount decision means 221 and a minimum black amount decision means 222 obtain a maximum black amount Kmax and a minimum black amount Kmin required to reproduce a color indicated by a 3-color signal received from a color image input device 100 and decide a setting black amount K, based on the maximum black amount Kmax and the minimum black amount Kmin. The maximum black amount Kmax and the minimum black amount Kmin are calculated, based on a maximum value and a minimum value of the black amount K being a variable in a function expression where colorimeter measurements of the received color image and the black amount K are related to color signals C, M, Y and the values of the C, M, Y satisfy relations of 0<=C<=100%, 0<=M<=100%, and 0<=Y<=100%. Furthermore, the black amount setting is decided by using functions of hue and chromaticity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for converting an input color image signal such as image data obtained by reading high-quality color data such as a photographic film or image data obtained from a digital camera into a color image forming apparatus. The present invention relates to a color image processing apparatus that converts an image recording signal to be transmitted and an electrophotographic color image forming system that forms a glossy image from an image recording signal input from the color image processing apparatus.

[0002]

2. Description of the Related Art In recent years, with the development of computers and the maintenance of networks and the like, and the emergence of large-capacity storage media and the like, and the spread of scanners and digital cameras, etc., the transfer and output of color image data such as photographs have been rapidly accelerated. The demand for printing out these image data with high image quality is increasing. In particular, there is an increasing demand for improving the image quality by giving gloss to a full-color image. On the other hand, among the color image forming apparatuses, the electrophotographic method does not require photosensitive paper, and can transfer a color toner image to plain paper, so that the use range is widened. In recent years, high-speed fixing has been performed, and fixing properties have been improved by applying instantaneous heating and pressure to a toner image. However, the toner image does not all penetrate into paper, which is a general recording medium, and is formed so as to rise on the recording medium. Therefore, in the halftone area and the highlight area, the structure of the lines and dots is raised from the recording medium in a raised and concaved shape, so that the scattering of incident light is increased and the density gradation is compared as in a human image. When a large image is formed, an image in which a high gloss area and a low gloss area are mixed becomes uncomfortable. Further, such a concavo-convex image has low color reproducibility due to the influence of irregular reflection on the image surface, resulting in an image with low sharpness.

On the other hand, in Japanese Patent Application Laid-Open No. 9-193506, the toner image is transferred to a toner image transfer position by a toner image holding member which holds the toner image and transfers the toner image from a predetermined toner image forming position to a predetermined toner image transfer position. Provided with a transfer and fixing means for transferring and fixing a plurality of color toner images onto a predetermined recording medium while heating by a heating member which is in contact with a heated object comprising at least one of the toner image holding member and the recording medium. In the forming method, by setting the softening point of the thermoplastic resin provided on the surface of the recording medium to be substantially equal to or lower than the softening point of the toner, the thermoplastic resin and the toner on the surface of the recording medium are heated to the same temperature. Even though the effect of sinking the toner resin is enhanced, the image gloss is the same as the recording medium, regardless of the image density and the image area ratio, excellent color reproducibility, and color unevenness. There is no occurrence, excellent granularity, and no fine non-uniformity of gloss of about 1 mm to 3 mm in diameter. Also, the adhesive strength between the recording medium and the image holding member is increased, so that fine adhesion is achieved. A method for eliminating the occurrence of unevenness is disclosed.

In the method disclosed in JP-A-9-193506, in which a toner image is fixed while being transferred onto a recording medium, recording with sufficiently high smoothness can be achieved without providing a resin layer on the recording medium. By using the medium, compared to a method of transferring the toner onto a widely used recording medium and then fixing the toner on the recording medium with a roll heat fixing machine,
It has a feature that a print having high gloss can be obtained.

By outputting a color image using a color image forming apparatus based on an image forming method of fixing such a toner image while transferring the toner image onto a recording medium, a texture close to a glossy silver halide photograph can be obtained. It is possible to obtain a print having

Normally, since an electrophotographic image forming apparatus records an image using an image recording signal of four colors including black, an image processing apparatus converts a three-color signal read by an image input device into black. Is widely used to convert to four-color signals including. In the prior art, the following inking methods are widely used to improve the degree of colorimetric color matching and improve color reproducibility.

Japanese Patent Application Laid-Open No. 7-87346 converts an input three-color signal into a three-variable color signal on a uniform color space,
By determining the R rate, an image output signal of four colors including black is determined from a UCR rate determined from a three-variable color signal and a saturation signal on a uniform color space. JP 6
In −242523, the maximum black amount Kma for reproducing the target color is
x and the minimum black amount Kmin are determined beforehand, and Kmax and Km
An image processing method of setting a value during “in” to the amount of black is performed.

[0008]

A color image processing apparatus in which a conventional inking method is applied to a color image forming apparatus for forming a color image using an image forming method for fixing a toner image while transferring the toner image onto a recording medium. There were problems in using the following.

First, silver halide photography has a feature that the maximum density (Dmax) is higher than that of printing. Therefore, the only reason that a Dmax equivalent to that of printing is obtained is that the image quality is significantly reduced. There is. For example, in a normal silver halide photograph, although the color reproduction is performed in three colors of yellow, magenta and cyan, the maximum density Dmax
Is very high about 4 to 6 in lightness L ^* of CIE L ^* a ^* b ^* color space, whereas in normal printing and electrophotography, yellow (Y), magenta (M) and cyan (C) )), The maximum density Dmax is L
It is known that ^* is relatively low at about 14 to 16.
In printing and electrophotography, it is widely practiced to increase the maximum density Dmax by performing color reproduction in four colors by adding black (K) in addition to three colors of yellow, magenta, and cyan. In printing, if too much black (K) is applied, the total amount of ink will be too large and transfer failure will occur. Therefore, even when four colors are reproduced, the maximum density Dmax is about 9 to 11 and it can be used for silver halide photography. The maximum density Dmax is lower than that in the conventional electrophotography, and the target of color reproduction is often set in printing, and the maximum density Dmax is equivalent to printing.

However, when a color image is formed by using an image forming method in which a toner image is fixed while being transferred onto a recording medium, the glossiness is equivalent to that of a silver halide photograph. When the color reproduction is performed, there is a problem that black is not tighter than a print obtained by a silver halide photograph, giving an impression that the image is blurred, and the image quality is remarkably deteriorated.

Further, since a print obtained by silver halide photography does not have a screen structure seen in printing or electrophotography, even if the same gloss is obtained in electrophotography, a screen-dependent pattern such as moiré is perceived. In such a case, there is a problem that the texture is far from the print obtained by the silver halide photograph. Furthermore, silver halide photography is much better in graininess than electrophotography, so even if the same gloss is obtained in electrophotography, especially if the graininess in the highlight part is poor, it can be obtained in silver halide photography There is a problem that the texture is far from the print.

The method of determining the amount of inking according to the saturation of an input color signal proposed in Japanese Patent Application Laid-Open No. 7-87346 can reduce the amount of inking in a high-saturation part and improve color reproducibility.
Improving the inking amount of the gray portion is certainly effective in that the reproducibility of the character portion of the image signal in which pictorial characters are mixed can be improved. However, the maximum black amount K for reproducing the target color is
Since the final set black amount K is determined only from the max, there is a problem that it is impossible to guarantee the maximum density Dmax that the image forming apparatus has when reproducing four colors.

Further, as disclosed in Japanese Patent Application Laid-Open No. 6-242523, this method has a region which cannot be used in the maximum color gamut which can be reproduced by a CMYK four-color printer. There is a problem that the color reproducibility of the part is poor. Therefore, assuming photo reproduction,
It gives the impression of insufficient concentration. Further, since the blackening amount is set from the saturation signal of the input color signal, black is mixed from the highlight portion in the gray portion, and the granularity of the highlight portion in the gray portion deteriorates. is there.

When a color image is formed by using an image forming method for fixing a toner image while transferring it onto a recording medium, a color shift due to a pixel position shift occurs because a belt is used for the intermediate transfer medium. It's easy to do. So 4
Although color misregistration is prevented by changing the screen angles of colors, the screen angles of yellow, magenta, and cyan are set sufficiently far apart so that moire is not perceived in three-color reproduction. In many cases, black is set to a screen angle close to one of the three colors. Therefore, according to the method disclosed in Japanese Patent Application Laid-Open No. 7-87346, black is always applied to the gray portion of the highlight portion where the screen structure is easily perceived, and moire occurs in the highlight portion, and the texture of the photograph is increased. There is a problem that it greatly deviates from the above.

The method disclosed in Japanese Patent Application Laid-Open No. 6-242523 discloses a maximum black amount Kmax and a minimum black amount Km for reproducing a target color.
Since the inking amount is determined from “in”, the maximum density Dmax that the image forming apparatus has when reproducing four colors can be guaranteed, and it is certainly effective in that a sufficiently high maximum density can be obtained. However, in this method, the maximum black amount K
Since there is no indication as to which value between the maximum and the initial black amount Kmin the black amount is set, the black amount is set to a constant rate between Kmax and Kmin as shown in the embodiment. In this case, as in Japanese Patent Application Laid-Open No. 7-87346, there is a problem that black is mixed in the highlight portion, and the graininess is deteriorated and moire is generated, so that the texture is far from the texture of a photograph.

SUMMARY OF THE INVENTION The present invention has been made to solve various problems in the above-described conventional color image processing apparatus, and an object thereof is to fix a toner image while transferring the toner image onto a recording medium. In a color image processing apparatus that inputs an image signal to a color image forming apparatus that forms a color image by using an image forming method, image recording for obtaining a print with sufficient maximum density, good graininess, and generation of moiré-free An object of the present invention is to provide a color image processing apparatus and a color image forming system capable of obtaining a high-quality print having a texture equivalent to that of a silver halide photograph by generating a signal.

[0017]

In order to achieve the above object, a color image processing apparatus according to the present invention converts three color signals read by a color image input device into four color signals including black (K: black). In the color image processing apparatus which converts the image recording signal to the color image forming apparatus and outputs the signal to the color image forming apparatus, the maximum black amount Kmax required to reproduce the colors indicated by the three color signals input from the color image input apparatus is calculated. Means for determining the maximum amount of black to be determined, and the minimum amount of black Kmi required to reproduce the colors indicated by the three color signals input from the color image input device.
minimum black amount determining means for determining n, and black amount determining means for determining a set black amount K based on the maximum black amount Kmax determined by the maximum black amount determining means and the minimum black amount Kmin determined by the minimum black amount determining means. And outputting image recording signals of four colors including the set black amount K determined by the black amount determining means to the color image forming apparatus.

Further, the color image processing apparatus of the present invention comprises:
The color signals of the three colors read by the color image input device are represented by L ^*
a ^* b ^* data, the first color conversion means for converting the lightness signal L obtained by the first color conversion means;
^The set black amount K is determined based on ^* , the maximum black amount Kmax determined by the maximum black amount determining means, and the minimum black amount Kmin determined by the minimum black amount determining means.

Further, in the color image processing apparatus according to the present invention, the maximum black amount determining means and the minimum black amount determining means include L ^* a ^* b ^* data obtained by the first color conversion means, and the L ^* a ^* data ^. A function (C, M, Y, K) relating the output amounts of C (cyan), M (magenta), Y (yellow), and K (black) in the color image forming apparatus corresponding to the b ^* data (C, M, Y, K) L ^* , a ^* , b ^* ) = F (C, M,
Formula (C, M, Y) = G (L ^* , Y) for calculating C, M, Y from L ^* , a ^* , b ^* , and K values based on Y, K)
a ^* , b ^* , K), and the equation (C, M, Y) = G
In (L ^* , a ^* , b ^* , K), each value of C, M, and Y when K is set as a variable is calculated, and 0 ≦ C ≦ 100
% And 0 ≦ M ≦ 100% and 0 ≦ Y ≦ 100%, the maximum value and the minimum value of K, respectively, are defined as the maximum black amount K
max and the minimum black amount Kmin, and the black amount determining means determines the set black amount based on an equation using the blackening rate α for the lightness L ^* , K = (1−α) Kmin + α · Kmax. It has a configuration for determining K.

Further, the color image processing apparatus according to the present invention comprises:
The color signals of the three colors read by the color image input device are represented by L ^*
a first color conversion means for converting the data into a ^* b ^* data; and a saturation determination means for calculating a saturation signal C ^* based on the a ^* and b ^* data obtained by the first color conversion means. The amount determining means is a lightness signal L ^* obtained by the first color converting means ^.
And a saturation signal C ^* calculated by the saturation determining means, a maximum black amount Kmax determined by the maximum black amount determining means, and a minimum black amount Kmin determined by the minimum black amount determining means.
Is determined.

Further, in the color image processing apparatus of the present invention, the maximum black amount determining means and the minimum black amount determining means include the L ^* a ^* b ^* data obtained by the first color converting means and the L ^* a ^* b. ^* C (cyan), M (magenta), Y (yellow), K in color image forming apparatus corresponding to data
Based on a function (L ^* , a ^* , b ^* ) = F (C, M, Y, K) relating the output amount (C, M, Y, K) of (black), L ^* , a Formula (C, M, Y) for calculating C, M, and Y from ^* , b ^* , and K values = G (L ^* , a ^* , b ^* , K)
And the formula (C, M, Y) = G (L ^* , a ^* , b ^* ,
In K), C, M, and K when K is set as a variable
Each value of Y is calculated, and 0 ≦ C ≦ 100% and 0 ≦ M ≦ 1
100%, and the maximum and minimum values of K that satisfies 0 ≦ Y ≦ 100% respectively have a configuration that determines the maximum black ink amount Kmax and the minimum black amount Kmin, black amount determining means, regarding the lightness L ^* Expression using the inking ratio α and the inking ratio β for the saturation C ^* , K = (1−α · β) Kmin
It is characterized by having a configuration for determining the set black amount K based on + α · β · Kmax.

Further, in the color image processing apparatus according to the present invention, the saturation determining means converts the saturation signal C ^* into a formula based on the values of a ^* and b ^* obtained by the first color conversion means,
C ^* = (a ^{* 2} + b ^{* 2} ) ^1/2 .

Furthermore, in the color image processing apparatus of the present invention, the value of the inking rate α about lightness L ^* is characterized in that set to be zero at high high-lightness region lightness L ^*.

Furthermore, in the color image processing apparatus of the present invention, the value of the inking rate β about chroma C ^* is characterized in that set to be zero in the high saturation C ^* high chroma region.

Further, the color image processing system of the present invention converts the three color signals read by the color image input device into four color image recording signals including black (K: black). And a color image forming apparatus that receives an image recording signal output from the color image processing apparatus and forms a color image, wherein the color image processing apparatus is input from a color image input apparatus. Maximum black amount determining means for determining the maximum black amount Kmax necessary for reproducing the color indicated by the three color signals, and for reproducing the color indicated by the three color signals input from the color image input device. The minimum black amount Kmin determined by the minimum black amount Kmin and the maximum black amount Kmax determined by the maximum black amount determination unit and the minimum black amount Kmin determined by the minimum black amount determination unit. Black amount determining means for determining a set black amount K, and output means for outputting to the color image forming apparatus four color image recording signals including the set black amount K determined by the black amount determining means. The color image forming apparatus includes a toner image carrier that conveys from a predetermined toner image forming position to a predetermined toner image transfer position based on four color image recording signals including a set black amount K input from the color image processing apparatus. A toner image forming means for forming a toner image thereon, and a multi-color toner image conveyed to the toner image transfer position on a predetermined recording medium, and a heated image comprising at least one of the toner image holding body and the recording medium. Transfer fixing means for transferring and fixing while heating by a heating element in contact therewith.

Further, in the color image processing system of the present invention, the recording medium has a surface coated with a thermoplastic resin, and the transfer and fixing means in the color image forming apparatus causes the toner image to permeate the thermoplastic resin. In which the toner image is transferred and fixed.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a schematic block diagram of a color image processing apparatus and a color image forming system of the present invention configured as described above. Color image processing device 20
0, the three color signals read by the color image processing input device 100 are converted into four color image recording signals including black (K: black). The printout is performed based on the four-color image recording signals input from the printer 200. The color image forming apparatus 300 includes a toner image forming unit that forms a toner image on a toner image holding body that holds a plurality of color toner images and conveys the toner image from a predetermined toner image forming position to a predetermined toner image transfer position. And transferring and fixing the toner images of a plurality of colors conveyed to the toner image transfer position onto a predetermined recording medium while heating them by a heating body which is in contact with a heated body comprising at least one of the toner image holding body and the recording medium. Transfer fixing means, and a glossy print is possible by transfer fixing of the toner image by these means.

Here, the color image processing device 200 has a maximum black amount determining means for determining the maximum black amount Kmax required to reproduce the colors indicated by the three color signals input from the color image input device 100. Minimum black amount determining means for determining the minimum black amount Kmin required to reproduce the colors indicated by the input three color signals, and the set black amount K from the maximum black amount Kmax and the minimum black amount Kmin. The determined black amount is determined by the maximum black amount Kmax and the minimum black amount Kmin.
Is determined, the maximum density at the time of four-color reproduction can be guaranteed, and a print having the same density as that of a silver halide photograph can be obtained.

Further, in the color image forming apparatus 300, the recording medium on which the transfer and fixing are performed is coated with a thermoplastic resin on the surface, so that a glossy image having a texture similar to a silver halide photograph can be obtained. .

As will be described in detail later with reference to FIG. 3, the image processing apparatus 200 has black amount determining means for determining the set black amount K, and also obtains a brightness signal indicating the brightness of the input color signal. A determination means is provided to determine the set black amount K from the maximum black amount Kmax and the minimum black amount Kmin based on the brightness signal. Further, the black amount determination means includes a brightness determination means for obtaining a brightness signal indicating the brightness of the input color signal, and a brightness signal and saturation obtained from the saturation determination means for obtaining a saturation signal indicating the vividness of the input color signal. It is also possible to determine the black amount from the maximum black amount and the minimum black amount based on the signal. here,
In the black amount determining means, by setting the black amount to zero in a bright area where the brightness signal obtained by the brightness determining means is a certain value or more, the graininess in the highlight portion is maximized, and the occurrence of moire is prevented. be able to.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a color image processing apparatus and a color image forming system according to the present invention will be described in detail with reference to the drawings. As described above, FIG. 1 is a block diagram showing one embodiment of a color image output system using the color image processing apparatus and the color image forming apparatus of the present invention. As shown in FIG. 1, the color image output system includes:
The image processing apparatus 200 includes the image input apparatus 100, the image processing apparatus 200, and the image forming apparatus 300.
Are the first color conversion means 210 and the second color conversion means 22
It has 0.

The image input device 100 takes in color images of various formats from the outside, and
Output to 0. In the example shown in FIG. 1, R (red),
For the data of each color of G (green) and B (blue), a color image signal composed of RGB data of 24 bits in total of 8 bits and 256 gradations is output to the image processing apparatus 200.

More specifically, the image input device 100 reads a silver halide photographic film represented by a 35 mm color negative film, a positive film, or an APS film as RGB data by a CCD sensor. Alternatively, image data is read from a CD-ROM in the KODAK / PhotoCD format and converted into RGB data, or captured image data is read from a digital camera such as Canon DCS1c, and RGB data is read.
Convert to B data. Alternatively, color image data edited by a user using another computer and stored in a recording medium typified by MO or Zip is read from the recording medium and converted into RGB data. Further, the image processing apparatus 2 converts the data read in various forms into RGB data, such as converting image information transmitted from a device connected on the network into RGB data.
00 is provided.

The image processing apparatus 200 has a first
The RGB data input from the image input device 100, which is constituted by the color conversion means 210 and the second color conversion means 220, is converted by the first color conversion means 210 into CIE L ^* a ^* b which is one of the uniform color spaces. ^* Converted to color space data.

The L ^* a ^* b ^* data from the first color conversion means 210 is input to the second color conversion means 220, and the second color conversion means 220 outputs an image recording signal in the color space of the image forming apparatus 300, In this example, the data is converted into data of four colors of Y (yellow), M (magenta), C (cyan) and K (black) and transferred to the image forming apparatus 300. Then, in the image forming apparatus 300, an image is formed on a sheet based on the YMCK data.

The input color signal from the image input device 100 is
Most commonly, it is RGB data. In the following example, the case of RGB data is also shown. However, data in another color space such as the CMYK color space used in printing or the YCC color space used in PhotoCD is used. Is also possible.

As the first color conversion means 210, a means for converting an input color signal into an L ^* a ^* b ^* color space can be typically used. In the following example, the L ^* a ^* b ^* color is also used. Although a case of converting into a space is shown, any color space that does not depend on a device may be converted into another color space such as an XYZ color space or an L ^* u ^* v ^* color space. However, it is desirable that the image data be converted into a uniform color space.

As the first color conversion means 210, a matrix operation type color conversion circuit, a direct lookup table type color conversion circuit, or a neural network type color conversion circuit widely used as a color conversion circuit is used. In this embodiment, a direct look-up table type color conversion circuit is used. The color conversion coefficient of the first color conversion means 210 was determined by the following method. First, colorimetric values of the color image input to the image input apparatus 100 a (L ^* a ^* b ^*) was measured with a commercially available colorimeter, the colorimetric values of the color image to be input (L ^* a ^* b ^*) Corresponding RGB
Data is obtained, and a conversion characteristic of output data (RGB) with respect to an input colorimetric value (L ^* a ^* b ^* ) is modeled. Such a model uses a high-order polynomial or a neural network. In the present embodiment, the characteristics of the image input device 100 are modeled using a neural network.
The color conversion coefficient of the first color conversion means 210 is determined by inversely solving the output L ^* a ^* b ^* color data corresponding to the address of the input RGB data using a neural network model using a nonlinear optimization method.

Further, the color space of the image forming apparatus 300 is
The following example shows the case of the YMCK color space, but other color spaces such as the YMC color space and the RGB color space may be used.

FIG. 2 schematically shows the structure of a color image forming apparatus according to one embodiment of the present invention. In FIG. 2, reference numeral 50 denotes a belt-shaped intermediate transfer member,
-1, 5-2, 5-3, 5-4 and the heating roll 2 to rotate in the direction of the arrow. A heating roll 3 is arranged opposite to the heating roll 2. Four photoconductors 1-1 and 1 arranged around the intermediate transfer body 50
-2, 1-3, and 1-4 are the electrostatic latent image forming chargers 15, 1
6, 17 and 18, the image processing apparatus 2
The image recording signals of the four colors CMYK transferred from 00 are output as laser light pulse-width-modulated by a screen generator 390 and output by a laser scanner 380.
Horizontal scanning is performed on the two photoconductors 1-1, 1-2, 1-3, and 1-4 to form an electrostatic latent image.

Next, a black developing unit 11, a yellow developing unit 12, and a magenta developing unit 13 are placed on the four photosensitive members 1-1, 1-2, 1-3, and 1-4 on which the electrostatic latent images are formed. And the cyan developing device 14 form black, yellow, magenta, and cyan toner images, respectively. The toner images are sequentially transferred to transfer units 50-1, 50-2, 50-3, 5
By 0-4, the toner image is transferred to the intermediate transfer member 50, and a plurality of color toner images are formed on the intermediate transfer member.

Thereafter, the recording paper having a surface coated with a thermoplastic resin layer on the surface fed from the paper tray 6 by the paper feeding device 7 is rotated by a pin roll 9-attached to a winding mechanism 8.
After being heated while being wound around the heating roll 3 by 1, 9-2, it is heated under pressure by the heating roll 2 and the heating roll 3 in a state of being in close contact with the intermediate transfer body 50. Thereby, the toner permeates into the thermoplastic resin layer on the recording paper.

The intermediate transfer body 50 and the recording paper pressed and heated by the heating roll 2 and the heating roll 3 move while being in close contact with each other, and are cooled by the cooling device 4. As a result, the toner that has permeated into the thermoplastic resin layer is coagulated and solidified to generate a strong adhesive force with the recording paper. Thereafter, on the roll 5-1 having a small curvature, the recording paper is separated from the intermediate transfer body 50 together with the toner by the stiffness of the recording paper itself, and a color image is formed. The toner image transferred and fixed on the recording paper is integrated with the resin layer on the surface of the recording paper, and the surface is smoothed and has high gloss.

As the photoconductors 1-1, 1-2, 1-3 and 1-4, various inorganic photoconductors (Se, a-Si, a-Si
C, CdS, etc.) and various organic photoreceptors can be used.

The toner is composed of a thermoplastic binder containing dyes such as yellow, magenta, and cyan, and can be made of a known material. In this embodiment, a polyester toner having a weight average molecular weight of 54000, a softening point of 113 ° C., and an average particle size of 7 μm was used. The amount of toner on the recording medium of each color is approximately 0.4 mg depending on the content of the dye.
The exposure condition or the developing conditions are set / cm ² so as to ～0.7Mg / cm ^2. In the present embodiment, each color 0.1.
It was set to 65 mg / cm ² .

The recording medium is a commercially available cast-coated paper, which is enamel-coated paper having a basis weight of 127.9 g / m ² (Yonago Processed Paper Co., Ltd.) and coated on its surface with a 7 μm-thick polyester. In this example, the weight average molecular weight was 12300 and the number average molecular weight was 327.
The case where a polyester having 0 and a softening point of 100 ° C. is used will be described.

The intermediate transfer member 50 is composed of a base layer and a surface layer.
A layered structure was used. As the base layer, a 70 μm-thick polyimide film to which carbon black was added was used. The volume resistivity was adjusted to 10 ¹⁰ Ωcm by changing the amount of carbon black added. As the base layer, for example, a highly heat-resistant sheet having a thickness of 10 to 300 μm can be used, and polyester, polyethylene terephthalate, polyether sulfone, polyether ketone, polysulfone, polyimide, polyimide amide, and polyamide For example, various polymer sheets can be used.

The surface layer is adjusted to have a volume resistivity of 10 ¹⁴ Ωcm in order to electrostatically transfer the toner image from the photoreceptor to the intermediate transfer member without image disturbance. When performing the simultaneous transfer and fixing to the toner, a rubber hardness of 40
A silicon copolymer having a thickness of 50 μm was used. The silicone copolymer has a property that its surface is tacky to the toner at room temperature, and that the toner that has been melted and fluidized is easily released in order to transfer the toner to the recording medium efficiently. Therefore, it is most suitable for the surface layer. In addition,
For the surface layer, for example, a resin layer having a high releasability having a thickness of 1 to 100 μm can be used, and for example, a tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, polytetrafluoroethylene, or the like can be used. It is.

As the heating roll, a metal roll,
Alternatively, a metal roll having a heat-resistant elastic layer made of silicon rubber or the like can be used. A heat source is arranged inside the heating roll, and its set temperature is determined by the heat melting characteristics of the thermoplastic resin layer on the surface of the toner and the recording paper,
Since the softening point of the toner> the softening point of the resin layer, the temperature is set so that the set temperature of the heating roll 2> the set temperature of the heating roll 3. In this embodiment, the heating roll 2 is 15
The temperature of the heating roll 3 was set to 120 ° C, and the temperature of the heating roll 3 was set to 120 ° C.
The heating roller 2 at the time of transfer and fixing, the pressure between the heating roller 3 is set to 5 kgf / cm ^2, the pressure may be in the range of 1kgf / cm ² ~10kgf / cm ² is not limited to this value. The outer diameter of the heating roll 2 and the heating roll 3 is 50.
mm, and the rotation speed of the heating roll was set such that the conveyance speed of the intermediate transfer body 50 was 240 mm / sec.

Further, in the present embodiment, the temperature of the surface of the recording medium in contact with the intermediate transfer member when the recording medium is separated from the intermediate transfer member is adjusted to 70 ° C. by adjusting the air volume of the cooling device 4. did.

In this embodiment, as the image forming apparatus 300,
Although a tandem engine electrophotographic color printer was applied, the image forming apparatus 300 is not limited to this, and a single engine type or an intermediate transfer member is not used, and a belt photoconductor having heat resistance is used. Transfers multiple color toner images formed on the belt photoreceptor directly to recording paper
A fixing method may be used.

Next, the image processing apparatus 20 according to the gist of the present invention will be described.
0 will be described. FIG. 3 shows a detailed configuration block diagram of the image processing apparatus 200. Hereinafter, the processing of the image processing apparatus 200 will be described with reference to FIG. L ^* a ^* b ^* data obtained from the first color conversion unit 210 is input to the maximum black amount determination unit 221 and the minimum black amount determination unit 222, and colorimetric values (L ^* a ^* b) input by a method described later. Kmax representing the maximum black amount and Kmin representing the minimum black amount for ^* ) are determined and sent to the black amount determining means 224. Further, a ^* and b ^* obtained from the first color conversion unit 210 are input to the saturation determination unit 223, and a saturation signal C ^* is obtained by the definition formula conversion shown in the following equation (1), and the black amount determination is performed. Input to the means 224.

[0053]

## EQU1 ## C ^* = (a ^{* 2} + b ^{* 2} ) ^1/2 . . . . . . (1)

In the black amount determining means 224, the brightness signal L ^* obtained from the first color converting means 210 and the saturation determining means 223
The obtained saturation signal C ^* , the maximum black amount Kmax obtained by the maximum black amount determining means 221 and the minimum black amount determining means 222
The set black amount K is determined from the minimum black amount Kmin obtained by the method described later, and the CMY determining unit 226 determines the set black amount K.
The output is sent to the K output unit 227. Parameter input means 225
Sets the inking function of the black amount determining means 224 described later. The CMY determining unit 226 uses the three-color signal L ^* a ^* b ^* obtained from the first color converting unit 210 and the set black amount K obtained from the black amount determining unit 224 according to a method to be described later to determine the image forming apparatus 300 corresponding thereto. The image recording signal CMY is determined and sent to the CMYK output unit 227.
The CMYK output unit 227 outputs the three-color image recording signals CMY obtained from the CMY determining unit 226 and the black amount determining unit 22.
The set black amount K obtained from No. 4 is output to the image forming apparatus 300.

The maximum black amount determining means 221 and the minimum black amount determining means 222 include an L ^* a ^* b ^* prediction unit, a CCM (Comp
outer color matching) section and a binary search section. The L ^* a ^* b ^* prediction unit is configured by a neural network. A plurality of pairs of CMYK and L ^* a ^* b ^* of the target printer are prepared in advance, and these pairs are learned as teacher data by the neural network of the L ^* a ^* b ^* prediction unit. Where CMYK and L ^*
The relationship with a ^* b ^* can be expressed by the following function (2).

[0056]

(L ^* , a ^* , b ^* ) = F (C, M, Y, K). . . . . . . (2)

The inverse function of the normal function F cannot be found. However, if L ^* a ^* b ^* is given and one variable in CMYK is appropriately determined, the remaining three variables can be obtained from equation (2).
For example, if K is given, CMY can be determined.
The CCM unit efficiently calculates CMY based on the following equation (3) by a method called CCM.

[0058]

(C, M, Y) = G (L ^* , a ^* , b ^* , K). . . . . . . (3)

Further, the CCM unit calculates the K on the right side of the above equation (3).
It is determined whether or not CMY satisfies the following equation (4) while shaking.

[0060]

## EQU4 ## 0 ≦ C, M, Y ≦ 100%. . . . . . . (4)

The largest K satisfying this condition is the maximum black amount Kmax, and the smallest K is the minimum black amount Kmin.
Is required. The binary search unit efficiently obtains the maximum black amount Kmax and the minimum black amount Kmin satisfying the expression (4) by assigning K in the expression (3) by the binary search algorithm.

The CMY determining means 226 also has a CCM unit,
CMY is calculated from L ^* a ^* b ^* and K according to equation (3).

The black amount determining means 224 determines the black amount K based on the following equation (5).

[0064]

K = (1−α · β) Kmin + α · βKmax. . . . . . . (5)

Here, the variables α and β are functions of the lightness L ^* and the saturation C ^* , respectively, and are set, for example, to the characteristics shown in FIG. The function shown in FIG. 4A represents the inking ratio α for the lightness L ^{*, and the} function shown in FIG. 4B represents the inking ratio β for the saturation C ^* . FIG.
In the figure of the inking rate α with respect to the lightness L ^* shown in (A), L is conveniently set so that the density increases in the X-axis increasing direction.
The value of ^* is shown so as to be small. These variables α and β are input from the parameter input unit 225 to the black amount determining unit 224, respectively.

In the present embodiment, if black is mixed in a bright portion having a high lightness of a medium density or less, the granularity is deteriorated and moire is generated. Therefore, a bright portion having an L ^* value of 50 or more, that is, FIG. Lightness L ^* 50 to 10 shown in FIG.
0 not at all put ink in a portion of, in order to achieve a sufficiently high maximum density Dmax, and 0 percent inking rate of 50 parts of the value of L ^*, a portion of 0 the value of L ^* black 7
Assuming 0%, both are connected by a straight line, and the value of L ^* 50 or more
Is used as the inking function. This makes it possible to realize a sufficiently high maximum density Dmax with excellent graininess and no moiré, because black does not appear on a bright portion below the set medium density.

In the present embodiment, the inking rate of a bright portion of 50 or more in the value of L ^* is set to 0, but the set value is L
^* = Not limited to 50, 70 preferably L ^* value
It is desirable to set in the range of ~ 30. In the present embodiment, the inking ratio at the maximum density point (the point where the value of L ^* is 0) is 7%.
Although set to 0%, the value of the set value is not limited to 70%, and is desirably set to a range of 30 to 100%. Further, in the present embodiment, the function of the inking rate relating to lightness is set to a polygonal line function using a linear function connecting two set points, but the type of function is limited to a polygonal line function using a linear function. Instead, any function such as a quadratic function can be used. Experiments are performed to set a free functional relationship by a look-up table, and α and β are stored in the parameter input means 225 and extracted as appropriate. You may comprise so that it may be used.

[0068] In the present embodiment, the saturation decreases the saturation black is mixed in a high portion, since the graininess deteriorates, as shown in FIG. 4 (B), C ^* values to in order to ensure that the more than 40 vivid part not at all put the ink, a 100% inking rate of the portion of the 0 in the value of C ^*, the inking rate of 40 part of the value of C ^* Assuming 0%, the two were connected by a straight line, and the line function with the value of C ^* 40 or more set to 0 was defined as the inking function. As a result, no black ink is applied to a vivid portion having a saturation higher than the set saturation. Therefore, a decrease in the saturation in the high saturation portion does not occur, and color reproduction with excellent graininess can be performed.

[0069] In this embodiment, although the inking rate of more than 40 bright part by the value of C ^* is 0, the set value is not limited to C ^* 40, preferably C ^* value At 20
It is desirable to set in the range of ~ 60. Further, in the present embodiment, since the basic inking rate is controlled by the inking function relating to the lightness, the gray portion (the value of C ^* is 0).
Is set to 100%, the value of the set value is not limited to 100% and may be set to another value. Further, in the present embodiment, the function of the inking rate relating to the saturation is set to a polygonal line function using a linear function connecting two set points, but the type of the function is not limited to this. Any function such as a function can be used, and an experiment may be performed to set a free functional relationship by a look-up table. Further, in the equation (5), β is 1
00% without considering the change in the amount of inking related to saturation,
The amount of inking may be controlled according to an inking function of only brightness.

As described above, the inking rate for the lightness L ^* and the saturation C ^*, which are the components orthogonal to each other in the color space, is described as an arbitrary functional relationship such as a linear function. By determining the set black amount K as a value between the amount Kmax and the minimum black amount Kmin, in a state where the maximum density is assured, an inking function taking into account the improvement of the graininess important for image quality and the prevention of occurrence of moiré is considered. By outputting an image with a color image forming apparatus using an image forming method of fixing a toner image onto a recording medium while transferring the toner image onto a recording medium, it is possible to obtain a glossy and texture similar to a silver halide photograph. You can get a print with

The above equation (5) is simplified and the function α of the lightness L ^* , the maximum black amount Kmax and the minimum black amount Kmin are obtained without using the function β of the saturation C ^* in the equation (5). It is also possible to configure so as to obtain the set black amount K by the following equation (6) using only

[0072]

K = (1−α) Kmin + α · Kmax. . . . . . . (6)

Using this equation (6), the maximum black amount Kmax and the minimum black amount Kmin are obtained by using only the L ^* , a ^* , and b ^* signals output from the first color conversion means 210. The set black amount K can be determined using each value of the maximum black amount Kmax, the minimum black amount Kmin, and the function α of the lightness L ^* .

In this case, the function α of the lightness L ^* is α at a lightness L ^* = 50 as shown in FIG.
= 0%, L ⁼⁼ 0 and α = 70% can be set by a linear function. In addition to such a setting, it can be set freely by various defined functions or a preset look-up table. It is possible to obtain α by setting a functional relationship.

[0075]

As described above in detail, according to the color image processing apparatus of the present invention, the maximum black amount K required to reproduce the colors indicated by the three color signals input from the image input apparatus is obtained.
a maximum black amount determining means for determining max, and a minimum black amount K required to reproduce the color indicated by the input three color signals.
minimum black amount determining means for determining min, and maximum black amount Kma
x and a minimum black amount Kmin to determine a set black amount K. The black amount determining unit determines the maximum black amount Kmax.
By determining the set black amount between the minimum black amount Kmin and the minimum black amount Kmin, it is possible to guarantee the maximum density when reproducing four colors, and it is possible to obtain a print having the same density as a silver halide photograph.

Further, according to the color image forming system of the present invention, a toner image is formed on the basis of an image recording signal of four colors input from a color image processing apparatus, and a plurality of color toner images are formed on a toner image carrier and In a color image forming system in which transfer is performed while heating is performed by a heating body that is in contact with a heated body made of at least one of the recording media,
The maximum black amount Kmax and the minimum black amount Kmin required to reproduce the color indicated by the color signal of the color are determined in advance, and the set black amount K is set between the maximum black amount and the minimum black amount. Since the maximum color reproduction range of the image forming apparatus is guaranteed, the maximum density
max can be expressed with a sufficient density.

Further, according to the present invention, the black amount determining means has a lightness determining means for obtaining a lightness signal indicating the brightness of the input color signal, and the blackening amount is controlled by a blackening function based on the lightness signal. Thereby, the graininess of the highlight portion which is important for photograph reproduction can be reproduced well, and the occurrence of moire can be prevented.

Further, according to the present invention, in addition to the brightness determining means for obtaining the brightness signal indicating the brightness of the input color signal in the black amount determining means, the saturation determining means for obtaining the saturation signal indicating the vividness of the input color signal is provided. By having a determining means and controlling the amount of inking by an inking function based on the brightness signal and the saturation signal, the graininess of the highlight portion important for photograph reproduction is reproduced well, and the occurrence of moire is prevented. In addition, a vivid color reproduction can be performed by preventing a decrease in the saturation of the high saturation portion.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example of a color image forming system including an image processing apparatus according to the present invention.

FIG. 2 is a detailed diagram illustrating an example of an image forming apparatus of the color image forming system of FIG.

FIG. 3 is a detailed block diagram showing an embodiment of the image processing apparatus of the present invention.

FIG. 4 is a diagram showing an inking function in a black amount determining unit of the image processing apparatus shown in FIG. 3;

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 Image input device 200 Image processing device 210 First color conversion unit 220 Second color conversion unit 300 Image forming device 1-1 to 1-4 Photoconductor 2 Heating roll 3 Pressure roll 4 Cooling device 5-1 to 5-4 Roller 6 Paper tray 7 Paper feeder 8 Winding mechanism 9-1, 9-2 Pin roll 11 Black developing device 12 Yellow developing device 13 Magenta developing device 14 Cyan developing device 15-18 Charger for forming electrostatic latent image 50 Intermediate transfer Body 50-1 to 50-4 Transfer device 200 Image processing device 300 Image forming device 380 Laser scanner scanning device 390 Screen generator 221 Maximum black amount determining unit 222 Minimum black amount determining unit 223 Saturation determining unit 224 Black amount determining unit 225 Parameter Input means 226 CMY determination means 227 CMYK output unit

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04N 1/46 H04N 1/46 Z (72) Inventor Kazuhiro Iwaoka 430 Sakai Nakaicho, Ashigara-gun, Kanagawa Prefecture Green Tech Nakai Fuji Xerox Co., Ltd.

Claims (10)

[Claims] 1. A color image processing apparatus for converting three color signals read by a color image input apparatus into four color image recording signals including black (K: black) and outputting the same to a color image forming apparatus. A maximum black amount determining means for determining a maximum black amount Kmax required to reproduce the color indicated by the three color signals input from the color image input device; and three colors input from the color image input device. , A minimum black amount determining means for determining a minimum black amount Kmin necessary for reproducing the color indicated by the color signal, and a maximum black amount Kmax determined by the maximum black amount determining means and a determination of the minimum black amount determining means. Black amount determining means for determining the set black amount K based on the minimum black amount Kmin to be set, and including the set black amount K determined by the black amount determining means.
A color image processing apparatus for outputting a color image recording signal to the color image forming apparatus. 2. The color image processing apparatus converts three color signals read by the color image input device into L ^* a ^* b ^*.
A first color conversion unit for converting data into data; wherein the black amount determination unit includes a lightness signal L ^* obtained by the first color conversion unit, a maximum black amount Kmax determined by the maximum black amount determination unit, and 2. The color image processing apparatus according to claim 1, wherein the set black amount K is determined based on the minimum black amount Kmin determined by the minimum black amount determining means. 3. The maximum black amount determination means and the minimum black amount determination means, wherein the L ^* a ^* b ^* data obtained by the first color conversion means and the L ^* a ^* b ^* data corresponding to the L ^* a ^* b ^* data Functions (L ^* , a ^* , b) relating output amounts (C, M, Y, K) of C (cyan), M (magenta), Y (yellow), and K (black) in a color image forming apparatus ^* ) = F (C, M,
Formula (C, M, Y) = G (L ^* , Y) for calculating C, M, Y from L ^* , a ^* , b ^* , and K values based on Y, K)
a ^* , b ^* , K), and the equation (C, M, Y) = G
In (L ^* , a ^* , b ^* , K), each value of C, M, and Y when K is set as a variable is calculated, and 0 ≦ C ≦ 100
% And 0 ≦ M ≦ 100% and 0 ≦ Y ≦ 100%, the maximum value and the minimum value of K, respectively, are defined as the maximum black amount K
max and the minimum black amount Kmin, and the black amount determining means sets black based on a formula using a blackening rate α related to lightness L ^* , K = (1−α) Kmin + α · Kmax. 3. The color image processing apparatus according to claim 2, further comprising a configuration for determining the quantity K. 4. The color image processing device converts the three color signals read by the color image input device into L ^* a ^* b ^*.
First color conversion means for converting data into data; and saturation determination means for calculating a saturation signal C ^* based on the a ^* and b ^* data obtained by the first color conversion means. The means includes a lightness signal L ^* obtained by the first color conversion means, a saturation signal C ^* calculated by the saturation determination means, a maximum black amount Kmax determined by the maximum black amount determination means, and the minimum black amount. Minimum black amount K determined by the amount determining means
2. The color image processing apparatus according to claim 1, wherein the set black amount K is determined based on min. 5. The maximum black amount determining means and the minimum black amount determining means, wherein the L ^* a ^* b ^* data obtained by the first color conversion means and the L ^* a ^* b ^* data corresponding to the L ^* a ^* b ^* data Functions (L ^* , a ^* , b) relating output amounts (C, M, Y, K) of C (cyan), M (magenta), Y (yellow), and K (black) in a color image forming apparatus ^* ) = F (C, M,
Formula (C, M, Y) = G (L ^* , Y) for calculating C, M, Y from L ^* , a ^* , b ^* , and K values based on Y, K)
a ^* , b ^* , K), and the equation (C, M, Y) = G
In (L ^* , a ^* , b ^* , K), each value of C, M, and Y when K is set as a variable is calculated, and 0 ≦ C ≦ 100
% And 0 ≦ M ≦ 100% and 0 ≦ Y ≦ 100%, the maximum value and the minimum value of K, respectively, are defined as the maximum black amount K
max and the minimum black amount Kmin, and the black amount determining means uses an inking ratio α for the lightness L ^{* and} an inking ratio β for the chroma C ^* , K = (1
5. The color image processing apparatus according to claim 4, wherein a setting value of the set black amount K is determined based on-[alpha] [beta]) Kmin + [alpha] [beta] Kmax. 6. The saturation determining unit calculates a saturation signal C ^* based on each of a ^* and b ^* values obtained by the first color conversion unit, and calculates C ^* = (a ^{* 2} + b ^{*). 2} ) The color image processing apparatus according to claim 4, wherein the color image processing apparatus has a configuration of calculating by ^1/2 . 7. The value of the lightness L ^* inking rate for α is the color image processing apparatus according to claim 3 or 5, wherein the set so as to be zero at high high-lightness region lightness L ^* . The value of 8. The chroma C ^* inking rate for β, a color image processing apparatus according to claim 5, characterized in that set to be zero in the high saturation C ^* high chroma region. 9. A color image processing device for converting three color signals read by a color image input device into four color image recording signals containing black (K: black), and an output from the color image processing device. A color image forming apparatus for receiving a recorded image recording signal and forming a color image, the color image processing apparatus comprising: Means for determining the maximum amount of black Kmax necessary to reproduce the color, and the minimum amount of black Kmin necessary to reproduce the colors indicated by the three color signals input from the color image input device And a maximum black amount Kmax determined by the maximum black amount determining unit and a minimum black amount Kmin determined by the minimum black amount determining unit. 4 including a black amount determining means, the setting black amount K which is determined by the black amount determining means
Output means for outputting a color image recording signal to the color image forming apparatus, the color image forming apparatus comprising: a set black amount K input from the color image processing apparatus;
A toner image forming means for forming a toner image on a toner image carrier conveyed from a predetermined toner image formation position to a predetermined toner image transfer position based on image recording signals of four colors including: Transfer-fixing means for transferring and fixing a plurality of color toner images conveyed to a predetermined recording medium while heating and transferring the toner images to a predetermined recording medium by a heating member which is in contact with a heated member comprising at least one of the toner image holding member and the recording medium. A color image forming system comprising: 10. The recording medium has a surface coated with a thermoplastic resin, and the transfer and fixing means in the color image forming apparatus causes the toner image to penetrate into the thermoplastic resin to form a toner image. 10. The color image forming system according to claim 9, wherein the color image forming system has a configuration for performing transfer fixing.