JPH0918733A - Laser beam printer - Google Patents

Abstract

PURPOSE: To provide a laser beam printer employing a new color separation technology integrating (fusing) adjustment of gradation and adjustment of color tone having been difficult in a conventional technology in producing a color copying image. CONSTITUTION: An image information detection section (S) has an image read device consisting of a photo-multiplier or a solid-state image pickup element (CCD) or the like and detects image information from a color original image being an object of a color copy image. An image processing section 20 integrates a gradation and color tone adjustment device having an algorithm of (gradation conversion equation), and is made up in addition of existing circuits such as a shading correction circuit, a gamma correction circuit, a masking processing circuit, a UCR processing circuit, a dither processing circuit and a multi-value processing circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention performs gradation conversion on image information obtained by photoelectrically scanning a continuous-tone color original image, and may be referred to as halftone (hereinafter referred to as halftone or halftone dot gradation). ) And a laser beam printer for producing color reproduction images.

In particular, the present invention relates to a laser beam printer in which a gradation converting section, which is a core component of the laser beam printer, has a new function. More specifically, the gradation conversion unit of the laser beam printer according to the present invention does not use the conventional density information value as the image information of the color original image, but the characteristic curve of the recording medium on which the color original image is recorded ( In order to eliminate the influence of the light amount value incident on the recording medium and the characteristic curve (defined by the density value formed on the recording medium), the light amount value is used and a color original document is formed using a specific gradation conversion formula. It is characterized in that it has a function of converting the light amount value of an image by gradation conversion and at the same time adjusting the color tone. The laser beam printer of the present invention is capable of quantitatively and rationally controlling not only gradation (also referred to as density gradation or gradation) but also color tone (color tone). A high-value-added laser beam printer in which color tone adjustment is integrated is provided.

The present invention relates to a laser beam printer that incorporates a new gradation conversion technique that integrates gradation and color tone control as described above. However, in the following description of the present invention, the gradation conversion unit of the laser beam printer of the present invention is new in the sense that the adjustment of the color tone at the time of gradation conversion, which was difficult in the prior art, was rationalized and quantified. The emphasis is on having a color tone management adjustment function.

[0004]

2. Description of the Related Art As is well known, a print image, a copy image (copy image), a printer output image, a TV (video) image, and the like are printed from a color original image recorded on various recording media by various color reproduction techniques. Various color reproduction images have been produced. In the production of these color reproduction images, first, the density gradation and color tone (color tone) of the color original image are reproduced in Hi-Fi color (High-Fidelity, high fidelity color) on the color reproduction image. Secondly, adjusting to a desired tone (including both gradation and color tone) is a very important issue.

However, in the conventional technology, it is the current situation that the above-mentioned problems cannot be reasonably carried out with work regularity. This is a technique for faithfully reproducing the tone (gradation and color tone) of the color original image on the color reproduction image, and further for adjusting (correcting or changing) the tone of the color original image to a desired tone. , A non-linear conversion processing technique for converting image information of a color original image which is the basis thereof, particularly image information in a density region into half tone gradation (hereinafter referred to as image gradation conversion technology or image gradation conversion method). .)
This is because it does not support rational theory, and performs image gradation conversion irrationally and irrationally, relying largely on human experience and intuition.

The above-mentioned points will be described below in the field of the technology for producing a color print image to which the present invention is related and which is always required to have high quality. The reason why the technology for producing a color print image is cited is because (1) the momentum of the present invention was born by the inventor in an attempt to solve the problems of the conventional technique for producing a color print image. And (2) As is well known, a halftone representation method for a duplicate image of a laser beam printer (a method for displaying the density gradation of pixels)
, (I) a method of changing the pixel coverage by the size of the dots (size modulation method), and (ii) a method of changing the pixel coverage by the number of (specified) dot arrays of a certain size (density modulation). Method), and the former is similar to the method of expressing a printed image by halftone dots, and (3) the color reproduction image produced by a recent digital high-grade laser beam printer is , Color proof for color print images (color proof, proof image, OK-p
That is why it is used as a roof).

In the prior art, when a color print image, which is a duplicate image, is produced from a color film original (about 90% of the color film original is a transmissive type or a transmissive type), the color film original is Brightest part (H
Part) to the darkest part (S part) without any intention to reasonably understand the density characteristics, and the correlation between a continuous tone color film original image and a halftone dot color print image which is a duplicate image. It can be said that the setting of the "color separation curve (also called the color separation work characteristic curve, halftone dot gradation characteristic curve, etc.)" that determines is completely dependent on human experience and intuition.

In general, a color print image is produced by color-separating a color film original image (hereinafter, simply referred to as a color original image) with a color scanner and performing multicolor plate making (generally C plate, M plate). Edition, Y
The four editions, the edition and the BL edition, are considered as one set. ) Is performed to reproduce a halftone dot color print image. As is well known, the C plate (cyan), the M plate (magenta), and the Y plate (yellow) are color-reduced corresponding to R (red), G (green), and B (blue) of the additive method. It has a complementary color relationship according to the law, and the BL plate is called black or black plate. The above-mentioned color scanner is a mechatronics-type extremely expensive device, but one of the major problems in the industry is that its operating rate is about 30 on average.
That is an extremely low level of%. The main reasons why expensive color scanners etc. have the above-mentioned low operation rates are that the setup time (scanner setup time) for operating the color scanner is long, and the quality of the product obtained by the color separation work is unstable and insufficient. Therefore, there are many rescans (rescan, remake).

Considering this from a slightly technical point of view, as described above, as a tool for color separation work, although a color scanner or the like which is highly sophisticated and expensive at first glance is used, Multiple elemental technologies for disassembly work, such as color reproduction, color correction, and color correction (Color Reproduc
technology and density gradation (Gradat
It can be said that the ion () conversion technology is not systematically organized, which is the main reason for the low availability of color scanners.

As is well known, the masking equation (Ma
sking equation) and Neugebauer equation (Neugebauer
has been pursued scientifically by applying equations). However, the latter technique of converting the density gradation of the image (this is attributed to the problem of what size halftone dots should be set for all pixels in the color original image).
Has been left unchecked without rational theoretical support, and this part is largely dependent on human experience and intuition.

Since various devices for color separation have been developed under such a condition, from the viewpoint of practicing color separation under the unified adjustment of color tone and gradation, the device itself In addition to being undeveloped in the basic design technology of, the operator's guessing work and the operator's experience and intuition are eliminated while using an expensive electronic color separation device (color scanner) that is expensive in actual work. Can't do (withou
t operator evalution, without operator's guess wor
k), it is not always possible to produce stable high-quality color print images.

Particularly, when the color original image is not a standard original produced under appropriate shooting and exposure conditions and appropriate development conditions, for example, an overexposed overbright original, an underexposed overexposed original, a high key or low key Manuscript,
Furthermore, if the original is a non-standard original such as an original with color cast or a faded original,
Color separation work cannot be carried out reasonably and efficiently. That is, it is impossible to rationally perform color separation work on these non-standard color original images, and there are problems such as the low operation rate of the color scanner, the instability of the product quality, and the increase in the rescan rate. I have.

[0013]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present inventors not only faithfully reproduce the image quality of a color original image (the quality evaluated by both the gradation and the color tone), but further proceed to the above. In order to rationally produce a halftone gradation color reproduction image having a desired tone (gradation and color tone) from various color original images, prior to improvement of color reproduction and color correction (correction) technology. We have a basic recognition that the technology for converting the density gradation of each pixel of a color original image must be rationalized.

Based on the basic recognition by the present inventors, the present inventors previously proposed a method for rationally converting the gradation of a color original image based on a novel gradation conversion formula. And achieved certain results (for example, Japanese Patent Application No. 63-114599, U.
SP4, 924, 323; Japanese Patent Application No. 1-135825
No., USP 5,313,310; Japanese Patent Application No. 1-2121.
No. 18, USP 5,057,931; Japanese Patent Application No. 3-78.
668, USP 5,134,494, etc.).

Since the novel gradation conversion method previously proposed by the present inventor has a deep relationship with the gradation conversion method applied to the laser beam printer of the present invention, the outline of the gradation conversion method will be described here. Will be explained. The gradation conversion method applied to the present invention is based on the gradation conversion method and is further improved. The improvement is an essential technical constitution of the present invention.

In the prior art, color separation of a color original image is performed by literally separating an original image (subject, entity image, actual image).
A scene is the apple itself if the subject is an apple. ) To a "recording medium" called a photographic light-sensitive material (photographic light-sensitive emulsion) under a predetermined exposure condition (as is well known, the intensity I of the incident light and the incident time t are E, the exposure amount E is E = It.) Based on the density information of the color photographic image recorded (the color separation operation includes both reproduction of gradation and reproduction of color tone as described above). I am doing it. As is well known, photographic density (photographic d
ensity) is formed, and this becomes a medium image. The curve showing the correlation between the above-mentioned photographic density (blackening degree) and the exposure amount E of the photographic light-sensitive material is a photographic density characteristic curve. This is the photographic density (D) on the vertical axis (D = logIo /
I) and the horizontal axis is the logarithmic value (logE) of the exposure amount E and is displayed. For a film or a dry plate (transparent original), the ratio of the intensity I of transmitted light to the intensity Io of incident light is
It goes without saying that the ratio of the intensity I of reflected light to the intensity Io of completely reflected light is used for printing paper (reflection original).

The above-mentioned photographic density characteristic curve (hereinafter, simply referred to as "density characteristic curve") is typically a downwardly convex foot portion, a substantially straight linear portion (linear intermediate portion), and an upward convex shape. Is a complex curve with shoulders (see FIG. 1 below for this point). In the prior art, the color separation work is performed based on the density information value of each pixel of the color original image. In other words, the conventional color separation technology is constructed from the standpoint of the vertical axis (density value) of the density characteristic curve. The image information value (density information value) of the color original image (medium image), which is the basis of the color separation work in the related art, is not proportional to the image information value of the original image (entity image, subject, actual scene). It is greatly influenced by the light-sensitive characteristics (density characteristic curve) of the photographic light-sensitive material (photographic light-sensitive emulsion) which is a recording medium. That is, the photographic density of the color original image which is a medium image is linearly related (the linear relationship of 45 ° of 1: 1) to the exposure amount (logarithmic value) which is the image information value from the subject (substantial image, real scene). Not what I did. It is well known that the discrimination characteristic of light and darkness in human vision is logarithmic, and humans can determine the amount of light incident on the visual system from a subject (substantial image) based on the discrimination characteristic described above. I am evaluating. Here, the gradient of concentration change is linear
I feel something that is natural.

As is clear from the above description, in the production of a color print image, when the color separation work is carried out by using the density value (D = logIo / I) of the medium image recorded on the photographic light-sensitive material as a clue, it becomes Since the density information value after being affected by the photosensitivity of the photosensitivity material is used, the image information value (light intensity value) obtained from the subject (real image, real scene) that is the true target of duplication is used. It's not what you're doing. Based on the above situation, the present inventors have
An approach that uses the image information value of the medium image, that is, the density value, which is changed non-linearly by the photosensitive characteristic (density characteristic curve) of the recording medium (photosensitive material) for producing a color print image. Instead of the first (raw, primitive) obtained from the subject (real image, real scene)
The method of producing a printed image based on the image information value related to the light amount such as the exposure amount was earnestly studied.

As a result, in the density gradation conversion operation which is primarily important in the color separation operation, (1) the density characteristic curve (photographic density characteristic curve) of the photographic light-sensitive material on which a color original image is photographed and recorded. The value of the horizontal axis (logE) is obtained from the density value of the vertical axis (D = logIo / I) (hereinafter, the vertical axis is also referred to as the D axis, and the horizontal axis is also referred to as the x axis). The light amount value on the x-axis is calculated from the density value on the D-axis of the medium image), and (2) more specifically, the density information value on the D-axis of an arbitrary pixel point (n point) on the color original image ( D _n ) is projected on the X-axis through the density characteristic curve to obtain an image information value (x _n ) relating to the exposure amount of the corresponding pixel, and then (3)
Based on the x _n value (light quantity value) obtained as described above, and the gradation conversion formula proposed by the present inventors (this is the gradation conversion formula adopted in the present invention described later. However, the present invention is completely different in terms of usage and application of the gradation conversion formula.) When gradation conversion of an image is performed under the condition (substantial image) ,
It has been found that a color print image with excellent image quality that is faithful to real images is produced.

The gradation conversion technique previously proposed by the inventors of the present invention is, as is apparent from the above, the first meaning in producing a color print image of halftone dots. It is applied for the gradation conversion, which is important in particular. That is, the gradation conversion technology proposed by the present inventors has a fidelity of 1: 1 for the density gradation of various original images including color original images, and the human vision It is used to produce color reproduction images with natural gradation. The gradation conversion technology described above is not limited to standard color original images, but also non-standard originals (overexposed or underexposed, high-key or low-key originals, color fog or fading). Even in this case, it is useful for reproducing the density gradation that the subject (substantial image) has. In addition, it was confirmed that the tone conversion technology described above can reproduce a rich tone of color (color tone) based on faithful reproduction of density gradation.

However, as described above, the gradation conversion technology previously proposed by the inventors of the present invention is as follows. Firstly, the gradation conversion is emphasized in the color separation work. Emphasizing realization of density gradation Hi-Fi conversion (conversion of gradation with a high fidelity of 1: 1 between a continuous gradation original image and a halftone dot reproduction image) It was confirmed that the gradation conversion technology can perform the gradation conversion with high fidelity and rationally, and that the tone can be reproduced richly along with the gradation conversion.

By the way, the market needs for the quality of the color print image are not limited to the need to reproduce the color print image having the tone (gradation and color tone) according to the color original image, and become more sophisticated, complicated and diversified. It is coming. For example, a specific part (person, ceramics,
Clothes, furniture, woodworking products, paintings, etc.) or specific parts (areas) should be emphasized and reproduced, or the overall color tone should be blue, dark green, light green, pink, sepia. There is a need to change to the desired one. To meet these needs, for example, conventional color correction (color correction)
In the case of using technology, even if the color tone of a specific portion can be reproduced as required, the tone of the entire image is distorted and the image quality is severely deteriorated. Needless to say, in order to meet the above needs, we have established a gradation and color tone conversion technology that gives the human eye a natural feeling in both the tone of a specific portion or region (region) and the tone of the entire image. It is important to.

In order to meet the above-mentioned sophistication and complexity of market needs, it means that in the color separation technology, the gradation conversion technology and the color tone adjustment technology must be unified (integrated). It is a thing. In that case, for example, in the case of a color print image, the halftone dots forming the color print image always have gradation (tone) and color tone (color tone) or both density and color. It has a direct relationship with. This is natural because the image quality is determined by the size of the halftone dot (defines the density gradation) and the colored ink applied on the halftone dot (defines the color tone). . And
The present inventors have established means for rationally adjusting and managing the size of halftone dots (halftone dot% value) in the previously proposed gradation conversion technique. Therefore, the inventors of the present invention are keenly aware that the integration of the gradation adjustment technology and the color adjustment technology described above is an extension of the gradation conversion technology previously proposed by the inventors. Considered.

As a result, the inventors of the present invention have adopted the tone conversion formula, which is the core of the previously proposed tone conversion technique, and combined this with the idea of color tone adjustment. We have found that both gradations can be adjusted and managed rationally. The present invention has been completed based on the above knowledge and bearing in mind the technical similarity between a color scanner and a laser beam printer for producing a color printed image. Color separation technology that rationally adjusts and manages both tones, and in particular, color tone management and adjustment technology that can adjust the tone to the desired one with rich tone reproducibility, which was difficult to achieve with conventional technology. The present invention provides a laser beam printer incorporating the. The laser beam printer of the present invention has a great feature in that it is equipped with the color separation technology in which both the gradation and the color tone are integrated as described above. However, in the following description of the invention,
In view of the current situation in which the prior art cannot reasonably and quantitatively manage the color tone, the explanation will be made with emphasis on the color tone management and adjustment function of the gradation conversion unit, which is a core component of the laser beam printer. .

[0025]

The present invention will be summarized as follows.
The present invention relates to a laser beam printer for producing a halftone (halftone) color reproduction image by gradation-converting image information of a continuous-tone color original image by a gradation conversion unit of the laser beam printer. (1) Characteristic curve of recording medium on which color original image is recorded [Relationship between light quantity value (x value) incident on recording medium and density value (D value) formed on recording medium] The characteristic curve that defines the Dx orthogonal coordinate system] is used to obtain the light intensity value (x value) from the density value (D value), (2) The light intensity value (x value) is Tone conversion formula> is used to perform gradation conversion to obtain a gradation intensity value (y _n value),
And (3) a color tone adjusting function used during the gradation conversion, wherein the color tone adjusting function is (3) -1. H part (lightest part) to S part (darkest part) of the color original image. In the predetermined area between
A color tone management point (M ₁ ) for managing the color tone of the color reproduction image is set, and (3) -2. At the color tone management point (M ₁ ), the color tone adjustment condition is a desired color plate (C plate). , M plate, Y plate, and BL plate), and (3) -3. Level of the color plate that reflects the light amount value at the color tone management point (M ₁ ) and the adjustment condition of the color tone. The tone intensity value and the desired tone intensity values to be set in the H and S portions are substituted into the following <tone conversion formula> to determine the γ value, and the H of the color plate is determined.
A <grayscale conversion formula> for performing a grayscale conversion of the light amount values of the pixels from section S to section S into a grayscale intensity value (y _n value), and
(3) -4. <Gradation conversion formula> for each color plate whose γ value is determined
The present invention relates to a laser beam printer characterized by having a color tone adjusting function configured to perform a gradation conversion of a light amount value of each pixel for each color plate and manage and adjust a color tone. Is. <Gradation conversion formula> y _n = y _H + [α (1-10 ^−kx ) (y _S −y _H ) /
(Α-β)] In the above item <tonal conversion formula>, the meaning of each symbol are as follows; x: shows the (x _n -x _H). That is, the color similarly obtained from the light amount value (x _n ) corresponding to the density information value (D _n ) at any pixel point (n point) of the color original image obtained by using the characteristic curve of the recording medium. The basic light amount value obtained by subtracting the light amount value (x _H ) corresponding to the density information value (D _H ) of the H portion of the original image is shown. y _n : Gradation intensity value set for a pixel on the color reproduction image corresponding to an arbitrary pixel point (n point) on the color original image. y _H : Gradation intensity value preset in the H portion on the color reproduction image corresponding to the H portion on the color original image. y _S : A gradation intensity value preset in the S portion of the color reproduction image corresponding to the S portion of the color original image. α: Surface reflectance of an image representation medium for recording a color reproduction image. β: Numerical value determined by β = 10 ^−γ . k: Numerical value determined by k = γ / (x _S −x _H ). However, x _S represents a light amount value (x _S ) corresponding to the density information value (D _S ) of the S portion of the color original image obtained by using the characteristic curve of the recording medium. γ: arbitrary coefficient.

The technical configuration of the laser beam printer of the present invention will be described in detail below. For convenience of description, the image information value and the document image will be described here. In the laser beam printer of the present invention, as image information used in producing a color print image from a color reproduction image, the image information value correlated with the density is not used as in the prior art, but the image correlated with the light amount is used. There is a major feature in using information. Further, in the present invention, the color original image is one recorded or accumulated in a predetermined recording medium, and is also called a medium image. On the other hand, an image before being recorded or accumulated in the recording medium, that is, an object that is a true target of duplication is called a substantial image (subject, actual object, real scene).
The color tone management method applied to the laser beam printer of the present invention will be described below with reference to a color print image having a strong technical similarity as a technique for producing a color reproduction image.

First, in order to gain an understanding of the present invention, a method of adjusting a color tone will be described in detail later. An outline of a gradation conversion technique using the <gradation conversion formula> will be described below.
explain. As described above, at present, a color scanner color separation device is very commonly used in the duplication work of a color print image, and the color separation work by the device is performed by a color original image (a transparent original and a reflection original as medium images). including.)
It is carried out based on the concentration information value obtained from.
More specifically, as a conventional method for producing a color print image, generally, a C plate (cyan) and an M plate (magenta) based on density information values obtained from a color original image (medium image) through R, G, and B filters. ), Y version (yellow), and BL version (black). However, for example, when a color film (transmissive type) original image (medium image) recorded on a recording medium called a photographic photosensitive material is used as a color original image, a method of utilizing the density information value taken from the image is It has the above-mentioned limitations (defects).

On the other hand, according to the present invention, as described above,
The true target of the copy is not the image recorded on the recording medium (medium image) but the literal color original image of the medium image, that is, the subject (substantial image) itself, and the image to be used at the time of duplication. The information value is based on the idea that the information value should be based on the image information value correlated with the amount of light incident on the recording medium from the subject. The above points are the basic differences between the gradation conversion technique of the present invention and the conventional technique.

This will be described below from another angle. In the color separation technique, it is necessary to convert a continuous tone color original image (for example, a transmissive color film original document) into a halftone dot color original image. A color separation curve (gradation conversion curve) defines the correlation between halftone dot images. The conventional color separation curve is formed on the D axis (density axis) of the photosensitive characteristic curve (photographic density characteristic curve defined by the D axis-x axis orthogonal coordinate system) of the photographic light-sensitive material as the recording medium. It is set based on the density information value. On the other hand, the color separation curve of the present invention is set on the basis of the image information value correlated with the light quantity of the subject (real image) on the x-axis of the photographic density characteristic curve as described above. That is, while the conventional color separation technology uses the D-axis color separation curve,
It can be said that the present invention uses the x-axis color separation curve, and both are basically different.

Next, a method of obtaining the image information value of each pixel of the color original image, that is, the light amount value in the image gradation conversion method using the <gradation conversion formula> of the present invention will be described.
First, from a characteristic curve of a photographic light-sensitive material as a recording medium used for photographing a color film original image (medium image), specifically, a photographic density value (D = logIo / I) and a subject (substantial image, real scene). A density characteristic curve showing the relationship between the image information value correlated with the amount of light incident on the photographic light-sensitive material as the recording medium, that is, the logarithmic value of the exposure amount (E = It) is prepared. Next, an arbitrary pixel (n
To determine light intensity values density value from (D _n) via the characteristic curves of the point) the (x _n), it is a function of the characteristic curves. For this purpose, for example, a density characteristic curve corresponding to the recording medium provided as a technical material by a photographic light-sensitive material manufacturer may be made into a function. If it can be reasonably functionalized, D
The D _n value on the axis can be easily converted to the x _n value on the x axis. Figure 1 shows the concentration characteristic curve (F company, Fujichrome)
Is shown. Further, Table 1 shows the result of formulating the concentration characteristic curve of FIG. In addition, as shown in Table 1, in order to formulate the concentration characteristic curve as accurately as possible, the formulating section is set to 8 sections, and the formulating is attempted in each section. It goes without saying that the more functional divisions, the more accurate the functional formula can be obtained.

[0031]

[Table 1]

In the mathematical expression of the density characteristic curve, an image information value correlated with the scale of the D axis indicating the density value of the color original image (medium image) and the light amount indicated by logE of the subject (substantial image). Assuming that the scales on the X-axis indicating the are the same, a function that defines the correlation between D and x was obtained. This is a kind of imitation made from the following viewpoints, and the present inventors consider that it is rational.
In this sense, the term canonical value is used on the X axis of FIG. That is, originally, in the photographic density characteristic curve, the logarithmic value of the exposure amount E on the X axis logE = logI ×
t) is located, which corresponds to the fact that the discriminative property for light and darkness of the visual sense is logarithmic as well as the perception of the density (visual sense) of the D axis, and thus the imitation on the above scale is reasonable. I think that is. It is needless to say that the above-mentioned grading in the present invention is a kind of simple method and is not limited to this.

In the present invention, the density value (D) of the color original image (medium image) formed by photographing and recording the subject (substantial image) on the recording medium (photosensitive material) as described above.
_n value) rather than based on, is to subject (entity image) correlated image information value to the amount represented by the x-axis is incident on the recording medium from the (x _n values) based. As described above, since the density characteristic curve is shown in Table 1 and the D _n value and the x _n value are correlated by the functional expression of x = f (D), it is easy to change the x _n value from the D _n value. You can ask.

Next, in the gradation conversion technique of the present invention, a color separation curve (gradation conversion curve) is obtained by using the light quantity value (x _n value) obtained as described above and the <gradation conversion formula>. That is, it suffices to obtain an x-axis color separation curve that replaces the conventional D-axis color separation curve and perform tone conversion of the image. That is,
For fabrication of a color print image, the image information values correlated to the amount of the corresponding pixel from under predetermined density characteristic curve, the concentration value at an arbitrary pixel (n point) on the original image (D _n) (x _The gradation intensity value (y _n ), that is, the halftone dot area% value (y _n ) is calculated by obtaining _n ) and substituting the (x _n ) value into the <gradation conversion formula>. Then, the gradation intensity value (y _n ) (halftone dot (area)% value) may be input to the output unit (halftone dot generator, dot generator) of the color scanner to produce a color print image.

The above-described <gradation conversion formula> derivation process of the present invention will be briefly described here. Halftone dot% value (y _n ) used when producing a color print image having the above-mentioned halftone dot gradation
<Gradation conversion formula> is a generally accepted density formula (photographic density, optical density), that is, D = logIo / I = log1 / T Io = incident light amount I = reflected light amount or transmitted light amount T = I / Io = It is derived from the reflectance or the amount of transmitted light. The general formula for the density D described above is applied to plate making / printing as follows. Density (D ') in plate making / printing = log (Io /
I) = log unit area × paper reflectance / [(unit area−
Halftone dot area × paper reflectance) + halftone dot area × ink surface reflectance] = log αA / [α {A- (d1 + d2 + ...
dn)} + β (d1 + d2 + ... dn)] where: A: unit area dn: area of each halftone dot within the unit area α: reflectance of printing paper β: surface reflectance of printing ink.

The present invention is based on the density formula (D ') relating to plate making and printing, and a basic density value (x) at an arbitrary sample point (pixel) (n point) on a continuous tone color original image, In order to associate the theoretical value with the actually measured value in association with the halftone dot% value (y _n ) of the halftone dot at the sample points on the color print image corresponding to this halftone gradation, Is derived.

In the operation of the <gradation conversion formula> of the present invention, generally 5% for y _H , 95% for y _S for C plate, 3% for y _H and 90% for y _S for M plate and Y plate. Is used. In the operation of the <gradation conversion formula>, if the densitometer measurement value is used for the density value and the percentage value (% value) as described above is used for y _H and y _S , the y _n value also becomes the percentage value ( % Value).

In the operation of the <gradation conversion formula> of the present invention, it is possible to use it by modifying it as follows as well as using it by arbitrarily processing, deforming or guiding it. y _n = y _H + E (1-10 ^−kx ) · (y _S −y _H ), where E = 1 / (1−β) = 1 / (1−10 ^−γ ), α = It is one. This is one in which the surface reflectance of the printing paper (base material) used for expressing a color print image is 100%. The value of α may be any value, but may be 1.0 in practice.

Further, according to the modification (alpha = 1.0), a y _H in the brightest part (H portion) of the color print image, as was expected a y _S to darkest part (S unit) It can be set, which is a great feature of the present invention. By the definition, the above-mentioned point is that x = 0 in the H part on the color print image, and x = x _S in the S part.
It is the -x _H, i.e., -k · x = γ · ( x S -x H) / (x S -x H) = - is evident from the fact that the gamma. Thus, the present invention <
By using the gradation conversion formula> (a modified example of a = 1), it is possible to always set the planned y _H value and y _S value in the H portion and the S portion on the color print image. This point
This is a very important point for users to evaluate and consider the work results. That is, y _H and y _S in the color print image
Set the desired value to and change the γ value (however,
= 1.0), various x-axis color separation curves (gradation conversion curves) can be obtained. Then, the image quality contents of the color print image produced under these x-axis color separation curves can be easily evaluated in relation to the γ value.

X of each color plate for multicolor plate making (generally, four plates of C plate / M plate / Y plate / BL plate are used) utilizing the <gradation conversion formula> of the present invention. To set the axis color separation curve (gradation conversion curve), the following may be done.
In the industry, it is common practice to first set a reference C color separation curve (gradation conversion curve), and then set the other color plates so that the gray balance and color balance are maintained. Is. The maintenance of the gray balance described above is a condition for reproducing a neutral density (gray) by three color plates (C / M / Y plates) and is a main requirement. In the industry, standard values shown in Table 2 below are generally adopted in order to maintain the gray balance. In Table 2, M ₁ is a gray balance management point (hereinafter, also referred to as an intermediate point) set in the intermediate portion of the dynamic range (density area) of the H portion to the S portion. In the art, the M ₁ point is usually set at a dot% value of C plate of 50% as shown in Table 2.
The main reason that the M ₁ point is set to the halftone dot 50% value of the C plate is that it is widely recognized that the halftone dot% value region is a reproduction region with rich gradation. From Table 2, in the art, in the M ₁ point (halftone), the halftone dot value of C plate is 50%, and the halftone dot value of other color plates (M / Y plate) is 4%.
It is understood that the gray balance is maintained by setting it to 0%.

[0041]

[Table 2]

As described above, the gradation conversion technique of the present invention is
In producing a color print image, the density information value (D _n ) obtained from a color original image (medium image) is not used, but is incident on a recording medium for forming a medium image from a subject (substantial image). It is premised that the image information value (x _n ) correlated with the amount of light is used and the <gradation conversion formula> is used, and the color has gradation characteristics faithful to the subject (real image). It is possible to produce a print image, and further, a color print image in which gradation characteristics are changed to a desired one, with work regularity, universality and elasticity.

Next, the core technical constitution of the present invention, that is, incorporating the tone adjustment technique into the above-mentioned tone conversion technique, in other words, integrating the tone conversion technique and the tone management adjustment technique Will be described. The trigger for the integration of the gradation and the color tone was as follows. (1) The <gradation conversion formula> proposed by the present inventors and used also in the present invention is the halftone dot of all the pixels from the H portion to the S portion of the color print image as described above. (Dot)
The halftone dot% value (in other words, the size of the halftone dot) of the original faithfully reproduces the gradation characteristic of the color original image, and the gradation characteristic is natural to human vision. It is an important tool for adjusting to. (2) The halftone dot value set for each pixel always has a direct relationship and influence on both gradation and color tone (or density and color). (3) As market needs, not only 1: 1 reproduction of color original image (Hi-Fi reproduction), but also enhancement of color tone of specific part of image, specific part of dynamic range of H part to S part,
The number of cases requiring (changing) changes and modifications is increasing. In addition, in the above request, customers and designers
The request contents are presented and specified by halftone dot% values by a color chart owned by them (which will be described later in detail). (4) In the case where the above needs are met by the conventional color separation technology, particularly the conventional color correction (color correction), even if the color tone of a specific portion is approximated to the requested content,
In many cases, the tone (gradation and color tone) of the entire image is distorted, and the value of the product is lost.

The color chart is a basic scale (reference table) for color reproduction in which all the colors are expressed by halftone dot density gradations using the printing process 4 primary color inks. For example, "DIC GRAF-G Color Chart" issued by Dainippon Ink and Chemicals, Inc.
(March 1991). In the color chart, there are various combinations as shown below as combinations of each color plate for color reproduction. 1. Basic combination: C (cyan) and M (magenta)
There is a chart based on the combination of. For example, (C) is printed on the vertical axis, and (M) is printed on the horizontal axis in 12 gradations with halftone dot% values of 0 to 100%, respectively, to form a basic pattern. There is a structure in which Y (yellow) and BL (sumi) having a% value are printed and overlapped. As Y or BL of the constant halftone dot% value, Y = 10
%, BL = 10%, Y = 10%, BL = 30
%, Y = 50%, BL = 10%,
and so on. 2. Other combinations: (1) A combination of (Y) on the vertical axis and (M) on the horizontal axis,
(2) A combination of (C) on the vertical axis and (Y) on the horizontal axis,
(3) Combination of (BL) on the vertical axis and (Y) on the horizontal axis,
(4) Combination of (BL) on the vertical axis and (M) on the horizontal axis,
(5) Combination of (C) on the vertical axis and (BL) on the horizontal axis.

As described above, the color tone on the color chart is specified by the halftone dot% value of each color plate (C / M / Y / BL). Therefore, in response to a color tone change request from a customer or a graphic designer based on the color chart, a technology for quantitatively and rationally managing and adjusting all halftone dot% values of each pixel is used as a color separation technology. It goes without saying that we must secure it.

From the background described above, the present inventors have
The gradation conversion formula> has the ability to completely quantitatively and reasonably manage and adjust the halftone dot value of all pixels from the H point to the S point, and is therefore effective for adjusting the color tone. I thought it would be a powerful tool. This is an opportunity to develop a color separation technique that integrates gradation and color tone using the <gradation conversion formula> as a main tool.

In the laser beam printer of the present invention, as described above, the gradation conversion section, which is the core component of the laser beam printer, incorporates the color separation technology in which gradation adjustment and color tone adjustment are integrated. It has characteristics. In particular, in the present invention, the color separation technique incorporating the color tone management adjustment is significantly different from the conventional technique, and this point will be described below.

1. First, a color tone management point (M ₁ ) for managing the color tone of the color print image is set at a desired portion between the H portion and the S portion of the color original. In the present invention, the same symbol (M ₁ ) as the halftone point (M ₁ ) for maintaining the gray balance in Table 2 is used as the symbol of the color tone management point (M ₁ ). This reflects that the tone reproduction in the halftone region is an important point in the color separation technique, and thus is also important in the tone reproduction. Needless to say, the color tone management point (M ₁ ) is not limited to the halftone point for maintaining the gray balance, and may be a desired point between the H portion and the S portion. .
The color tone management point (M ₁ ) displays a vertical axis (y-axis: halftone dot% value) and a horizontal axis (x-axis: light amount value), as will be described later in the embodiment and in FIG. .) Cartesian coordinates are displayed with the light amount value on the horizontal axis. Since the light quantity value correlates with the density value of the color original image, it may be displayed as the density value.

2. Next, at the color tone management point (M ₁ ) designated as described above, the color tone adjustment condition is determined by the halftone dot value of the desired color plate (C plate, M plate, Y plate, and BL plate). To do. The specific content of the adjustment (change) condition of the color tone is as described in the description of the color chart.

3. The next step is to use each of the color plates (C plate, M plate, Y plate, BL
Preparation of the color separation curve (gradation conversion curve) used for producing the color separation image of (version), more specifically, the <gradation conversion formula> for setting the color separation curve for each color plate. Preparation. By the above steps (1 to 2), the light quantity value of the color tone management point (M ₁ ), for example, M ₁
= 0.400, ・ Color tone adjustment conditions, for example, C plate halftone dot% value (50%),
Halftone dot value for M plate (20%), Halftone dot value for Y plate (10%), B
L halftone dot% value (10%) is set. The halftone dot% values (y _H , y _S ) set in the H and S parts of each color plate are set to values given in advance or desired values. It should be noted that the y _H value and the y _S value given as the above-mentioned conditions are C,
It means 5% and 95% for the plates, respectively, and 3% and 90% for the plates M and Y, respectively (see Table 2). Under the above conditions, the γ value of the <gradation conversion formula> used to determine the color separation curve for each color plate is determined. For example, the γ value of the <gradation conversion formula> for determining the color separation curve for C plate is determined as follows. In the above <gradation conversion formula>, x _H = 0.00, x _S = 1.00, x _n = M ₁ = 0.4
0, α = 1.00, y _H = 0 (%), y _S = 95
By substituting (%), y _n = 50% for solving, a value of γ = 0.45 is obtained. As a result, <gradation conversion formula> for setting the color separation curve for C plate is prepared. The same applies to other color plates.

4. The next step is the γ value (0.
45) is used, the light amount values (x _n ) of all pixel points (n points) from the H section to the SH section are subjected to gradation conversion, and the C separation color separation curve ( This is a step of obtaining a gradation conversion curve). In other words, the color separation work is performed using the <gradation conversion formula> for the C plate in order to produce the C plate color plate image. The same applies to other color plates.

As described above, the laser beam printer of the present invention, in particular, the color scanner for producing a color print image having a strong technical relevance with respect to the characteristics and characteristics of the gradation converting portion which is the central mechanism (main component) thereof. It was explained using the example. As described above, there is no substantial difference between the method for producing a color printed image by the color scanner and the method for producing a color duplicate image by the laser beam printer. The laser beam printer of the present invention has been described by taking the color scanner as an example because the structure and mechanism of the color scanner for producing a color print image are well known, and the color separation technology adopted is well known. It is merely a convenience to gain an understanding of the present invention.

The laser beam printer of the present invention has the greatest feature in the color separation technique incorporating the gradation conversion and color tone adjustment functions in the gradation conversion unit. This will be described below. The laser beam printer of the present invention uses various color original images, that is, various color original images obtained by recording, photographing or image-converting a subject (substantial image) on a desired recording medium using an information transmission medium such as light and electromagnetic waves. (Medium image) can be used. Examples of the recording medium for the color original image include a transmission type color film (photosensitive emulsion), a photoelectric conversion element such as a two-dimensional CCD or a photodiode, an optical disk or a porcelain disk. It goes without saying that a reflection original such as a painting or a color print can be used as the color original image.

In order to obtain the light intensity value from the density information value in the various recording media described above, a photographic density characteristic curve or a photoelectric conversion characteristic curve may be used depending on the type of recording medium. It should be noted that reflective documents such as paintings and color prints are treated as if their characteristic curves correspond linearly with a density information value and a light intensity value of 1: 1 (corresponding to a linear relationship of 45 °). Needless to say, that is all right.

In the laser beam printer of the present invention,
Photodiodes and CCs that constitute the recording medium system described above
If a density characteristic curve (photoelectric conversion characteristic curve) peculiar to these recording media can be defined as a recording medium such as D,
The performance of existing recording media is sufficient, and using these recording media, it is possible to produce a color reproduction image having significantly higher gradation (density gradation or color tone) than ever before. That is, attempts are being made to improve the characteristics (photosensitive characteristics and photoelectric conversion characteristics) of various recording media in an attempt to produce high-quality color reproduction images (for example, high dynamic range and linearity of characteristic curves). In order to produce a color reproduction image according to the present invention, it is not always required that various recording media have high quality and high performance, and existing performances (characteristics) are sufficient. This is due to the gradation conversion technology incorporated in the laser beam printer of the present invention, and constitutes another feature of the present invention.

Next, in the laser beam printer according to the present invention, the structure of the gradation conversion unit, which is the main constituent element (mechanism) for performing color separation by integrating the above-described gradation and color tone adjustment, will be described. 1. In the present invention, the gradation conversion unit is configured as follows, for example. (1) A density information value obtained from a color original image recorded on a predetermined recording medium (sensor), and an image information value correlated with the amount of light incident on the recording medium (sensor) from a subject (actual image) The image information value and / or the image information electric signal value (either analog or digital) relating to the density of a color original image (including a hard original and a soft original) based on a density characteristic curve that defines the correlation between It is also possible to provide a mechanism (for software) that obtains an image information value correlated with the light amount corresponding to (2), and (2) a mechanism (for software) that operates the <tone conversion formula>. .

2. Further, the configuration of the output unit is such that the current value and voltage value of the recording unit (recording head) of the device are associated with the calculated value by the <gradation conversion formula>, that is, the y _n value (gradation intensity value).
Alternatively, by controlling the application time, etc., the size of dots and the array density of dots are changed (the size modulation method or the density modulation method is adopted), and the half tone (halftone dot level) in which the gradation and color tone are adjusted as desired. It is sufficient to configure so that a color duplicate image of (tone) is output. The y _n value of the present invention is also called a halftone dot value in connection with a color printing image reproduction technique, but is generally called a gradation intensity value as described above.
The y _n value of the present invention should be construed in the broadest sense regardless of its nominal law.

For example, a color film original image (transmissive medium image) is irradiated with a small spot light, and the transmitted light (image information signal) is converted into a photoelectric conversion unit (photomul or CC).
D) receives the light, converts the intensity of light into the intensity of voltage, digitizes the obtained image information electrical signal (voltage value), and performs necessary organization and processing by a computer, that is, by <gradation conversion formula> Converts the gradation and activates the output part of the laser beam printer based on the gradation intensity value (y _n value) output from the computer, ejects ink onto the recording paper in synchronization with the input system, and reproduces a color reproduction image. It is sufficient to use a well-known existing system for creating.

At this time, the computer processing mechanism unit for organizing and processing the image information electric signals of the color original image (medium image) is reconfigured, and the color original image recorded on the color film (recording medium) ( The image information value correlated with the light amount is obtained from the density information value of the medium image) through the density characteristic curve of the color film (recording medium), and the halftone dot value (y _n value)
All you have to do is to incorporate software that outputs.

As can be seen from the above description, a color original image (a medium image photographed and recorded on a recording medium called a photographic photosensitive material) is an image information acquisition mechanism (detection unit) of a laser beam printer, specifically, photoelectric conversion. Department (Photomaru and C
Image information values that are processed in CD) and are correlated to density. Strictly speaking, since the photoelectric conversion unit has its own characteristic curve (photoelectric conversion characteristic curve),
In the photoelectric conversion unit, the image information of the color original image is affected (altered or deteriorated) by the photoelectric conversion characteristic curve of the photoelectric conversion unit. Therefore, it is preferable to eliminate the influence of the photoelectric conversion characteristic curve, but this may be ignored. In other words, the image information of the color original image is affected (altered or deteriorated) by the photoelectric conversion characteristic curve of the photoelectric conversion unit. Therefore, it is preferable to eliminate the influence of the photoelectric conversion characteristic curve, but this may be ignored in consideration of the characteristics of the photoelectric conversion unit.

As the software applied to the above-mentioned gradation conversion unit, the image information which correlates the density information value (D _n ) which correlates with the density of the color original image with the corresponding light quantity under a predetermined density characteristic curve is used. A general-purpose computer that converts into a value ( _xn ) and has the algorithm of <gradation conversion formula> as software and has an A / D (analog-digital conversion) and a D / A I / F (interface), An electrical circuit that embodies a general-purpose IC with the algorithm as logic, and an RO that holds the algorithm operation result
Various forms such as an electric circuit including M, a PAL in which an algorithm is embodied as an internal logic, a gate array, a custom IC, and the like can be taken. Particularly in recent years, modularization has been developed, and an arithmetic mechanism capable of performing gradation conversion of an image based on the above <gradation conversion formula> of the present invention is a dedicated IC, LSI, microprocessor, or microprocessor. It can be easily manufactured as a module such as a computer.

Next, the related matters for exhibiting the color tone adjusting function in the gradation converting section of the laser beam printer of the present invention will be specifically described. In the case of a laser beam printer, unlike the case of producing a color print image, each color plate (C / M / Y / BL) is individually produced, and the approach of overprinting this is not adopted, and each color is sequenced. We have adopted the approach of continuously overlapping under control. However, for convenience of description, in the following description, it is called a color plate image that statically captures each color image, and in relation to this, a C plate image (color plate image), a C plate separation curve (gradation conversion curve), etc. Is used.

(1) Determination of Color Tone Management Point (M ₁ ) The color tone management point (M ₁ ) may be any point between the H section and the S section. However,
In order to reproduce rich gradation in a monochrome print image or a color print image, a halftone, more specifically, a point where the halftone dot value of the C plate image (color plate image) is 50% is widely adopted as a management point. ing. Therefore, also in the laser beam printer of the present invention, the C plate color separation curve (gradation conversion curve) is used as the color tone management point (M ₁ ).
In, it is preferable to select a region _{where the} gradation intensity value (y _n value) = 50%. Color tone management point (M ₁ )
Is the standard condition (see Table 2) for maintaining the gray balance at the time of producing a color print image.
Needless to say, in the present invention, as described above, the color tone management point (M ₁ ) is not limited to the region where the gradation intensity value (y _n value) = 50%.

(2) Light intensity value (x value) of color tone management point (M ₁ ) The light intensity value (x value) of color tone management point (M ₁ ) may be determined as follows. In each color plate of the laser beam printer, it is preferable to set a reference color separation curve (gradation conversion curve) and set the other color plates so as to maintain gray balance and color balance in relation to this. This idea is the same as the production of a color print image. Therefore, as in the color printing technique, the reference color plate is the C plate, and (i) the desired γ value, for example, γ = 0.45 used when the color print image is produced, and (ii) the desired y _H , Y
_S , α value, for example y _H = 0 adopted when the printed image is produced
%, Y _S = 95%, α = 1.00. <Gradation conversion formula> is operated under the condition of (1) to set the color separation curve for C plate (gradation conversion curve). Then C determined as above
In the plate color separation curve (gradation conversion curve), y _n =
The light quantity value (x value) at 50% may be obtained. That is, the above condition may be substituted into <gradation conversion formula> to solve the following formula.
In this case, a light quantity value of x = 0.40 is obtained. 50 = 0 + [(1-10 ^-0.45x ) (95-0) / (1-
10 ^-0.45 )] (Note) In the operation of <Gradation conversion formula>, x _S −
x _H = 1.000. Generally, the dynamic range (x _S of the light amount value obtained from the color original image (medium image) is calculated.
Although −x _H ) is not 1.00, here, a value obtained by normalizing the dynamic range to 1.00 is used.
Needless to say, even if the dynamic range is normalized to 1.00, the image quality contents are changed relative to each other, so that there is no problem in image processing.

(3) Method for Determining γ Value for Determining Color Separation Curve for Each Color Plate (C / M / Y / BL) As described above, the color separation curve for C plate (gradation conversion curve)
The γ value for setting is determined as γ = 0.45. For other color plates, the γ value for setting the color separation curve must be obtained according to the content of the color tone adjustment conditions. For example, in the case of the M plate, at the color tone management point (M ₁ ) (this x value is x = 0.40), the gradation intensity value (y _n value) of the M plate is 20%, and under the initial conditions. The gradation intensity value (0%) of a certain y _H portion and the gradation intensity value (68%) of a y _S portion are substituted into the <gradation conversion formula> to obtain the γ value for the M plate. That is, γ = 0.20 is obtained from the following formula. 20 = 0 + [(1-10- ^{γ (0.40)} ) (68-0) /
(1-10 ^−γ )] In the laser beam printer of the present invention, the light amount value of the color tone management point (M ₁ ) and the γ value for each color plate are automatically calculated, and a desired color separation curve is prepared. The above software may be installed in the gradation conversion unit.

[0066]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The laser beam printer of the present invention will be described in more detail with reference to the drawings. 2 to 5
FIG. 1 is a diagram illustrating a laser beam printer device according to a first embodiment of the present invention. FIG. 2 is a block diagram illustrating a schematic configuration (mechanism) of the laser beam printer. As shown in the figure, the image information detection unit (S) has an image reading mechanism composed of a photomultiplier, a solid-state image sensor (CCD), and the like, and an image is read from a color original image to be a color duplicate image. Information is detected. For example, when a color film original (transmissive type) is used as the color original image, the density information value (D _n ) detected by the detection unit (S)
The characteristic curve of the recording medium (density characteristic curve) image information values correlated to the quantity by using the (x _n), further obtains basic amount value _{(x = x n -x H)} . The density information value (D
_The function of obtaining the image information value (x _n ) or the like correlated with the light amount value from _n ) may be incorporated in the image processing unit (20) described below. The image processing unit (20) incorporates a gradation and color tone adjusting mechanism having the <gradation conversion type> algorithm of the present invention, and the others include existing shading correction circuits, γ correction circuits, masking processing circuits. , UCR
It is composed of a processing circuit, a dither processing circuit, a multilevel processing circuit, and the like.

FIG. 3 shows an output pattern (dot pattern).
FIG. That is, in the laser beam printer of the present invention, the color original image is color-separated, and C, M,
A dot pattern as shown in FIG. 3 is output in order to reproduce a halftone (half tone) based on the well-known dither matrix method by applying the <tone conversion formula> to each of Y and BL colors. As described above, in the laser beam printer of the present invention, the image information signal obtained from the image information detecting unit (S) is the <gradation conversion formula> of the image processing unit (20).
The tone is converted in the tone conversion section based on the laser beam, and the beam emitted from the laser tube (L) is modulated. A good recorded image or a recorded image whose gradation and color tone are adjusted as desired is developed.

FIG. 4 is a detailed block diagram of the laser beam printer apparatus according to the first embodiment of the present invention. As shown in FIG. 4, the laser beam printer device of the present invention is
A detection unit (1) for reading transmitted light or reflected light of the color original image (5) by dividing it into R (red), G (green), and B (blue), and output signals C (cyan), M (magenta). , Y (yellow), K (black) (hereinafter, K is used instead of BL as a symbol) to process a color separation signal so that an appropriate gradation image is formed. , The output unit (4) for exposing the photosensitive drum by a laser modulated based on the output signal of the gradation adjusting unit (3) to form a latent image, and further developing and fixing the latent image. .

In the present invention, among the four blocks,
The detection unit (1), the color separation unit (2), and the output unit (4)
The mechanism and configuration of the conventional laser beam printer are used as they are. In other words, the gradation adjusting unit (3) is the object of the improvement of the present invention. Strictly speaking, the gradation and color tone of the present invention
The gradation conversion unit based on the <gradation conversion formula> that integrates the adjustment of [1] to perform color separation is also related to the improvement of the function of the color separation unit (2). Therefore, the laser beam printer of the present invention is configured by changing the configuration of the conventional gradation conversion unit to the gradation conversion unit of the present invention while utilizing the color separation unit (2) of the existing laser beam printer. It can be said that

The structure of the laser beam printer of the present invention will be specifically described below. Detection unit (1) described above
Detects the transmitted light or the reflected light of each part of the color original image (5) such as Photomul, and outputs R, G, and
Each of the B and USM signals is output, and this signal is converted into a voltage signal in the A / V converter (6). Color separation part (2)
In the log amplifier (7), R of the detection unit (1),
The voltage signals of G, B, and USM are logarithmically calculated and converted into densities, and the basic masking (BM) (8) separates C / M / Y color components (basic color components) and black (K) components. To separate. That is, in the laser beam printer of the present invention, an original image (5) which is an object to be duplicated (color print, color print, etc.) is first detected by a photomultiplier or solid-state image sensor (CCD) in the detection unit (1) by a conventional method. Image information for each color (R, G, B) is detected by the image information reading mechanism, and the density information value (D _n for producing a color duplicate image by performing color separation in the color separation unit (2)). ) Is obtained. this is,
As described above, each color (C, M, Y) component (basic color component)
Ask for each.

The density information value (D _n ) is a characteristic curve of the recording medium system, for example, a photoelectric conversion characteristic curve of the CCD which is the recording medium, and is used as an image information value (x _n ) correlated with the light amount.
Further, it goes without saying that it is converted into the basic light amount value (x). In addition, in order to obtain the image information correlated with the above-described light amount, it may be performed by software or hardware (not shown). In the present invention, the image information value (x _n ) correlated with the amount of light from the density information value (D _n ) described above.
The function of obtaining the basic light amount value (x) may be incorporated in the gradation adjusting unit (3) described below. This is because the gradation adjusting unit (3) operates an algorithm of <gradation conversion formula>, and since the image information of the light quantity value correlation is also obtained by a predetermined algorithm, it is said that the calculation functions are integrated into one. It is based on the idea. In addition,
It goes without saying that the present invention is not limited to this method.

FIG. 4 shows a color correction (CC) section (9) as a structure of the color separation section (2). Here, for each original color of R, G, B and C, M, Y, C
Components, M component, and Y component are controlled, and the K component of the original is further controlled by the UCR (under co
lor removal) or UCA (uncer color additio)
In n), the ratio represented by three types of inks of C, M, and Y and the ratio represented by K (black ink) are determined.

The C, M, Y and K components converted into the image information value correlated with the light quantity in this manner are C, M and Y components in the gradation conversion unit (11) of the gradation adjustment unit (3). , K to pixel density values (gradation intensity values) in pixel blocks of each color component, that is, ce ′, me indicating the effective area ratio of each color component.
Conversion to ', ye', ke 'is performed. Gradation converter (1
1) is an algorithm for obtaining a light intensity value (x _n ) value from a density value (D _n ) using a characteristic curve of a recording medium on which a color original image is recorded, and a <gradation conversion formula> calculation It has an algorithm. And
<Gradation conversion formula> is applied to each of C, M, Y and K to obtain ce ', me', ye 'and ke'.

The gradation conversion unit (11) has an algorithm of <gradation conversion formula> as software and
/ D, D / A general-purpose computer having I / F (interface), general-purpose I using algorithm as logic
Various forms such as an electric circuit embodied by C, an electric circuit including a ROM holding the operation result of the algorithm, a PAL embodying the algorithm as an internal logic, a gate array, a custom IC, and the like can be taken.

The effective area ratio corresponding to the pixel density value of each color component obtained by the gradation conversion unit (11) is input to the color channel selector (CHS) (12) and the color channel selector (CHS) (12). Is ce ', me
′, Ye ′, and ke ′ are sequentially output at the time of selection. This output is A / D converted by the A / D conversion unit (13) and input to the dot control (D / C) unit (14) for each color. After that, the laser light modulated according to the output value of the dot control section (14) is changed to a laser light source (15).
Is emitted and an electrostatic latent image is formed on the photosensitive drum.
Next, the image formed by each color developing machine (16a to 16b) is developed on the recording paper (17) and fixed by the fixing machine (18), and a color reproduction image (recorded image) excellent in gradation and color tone is obtained. Is formed. In addition, (19) is a charger for uniformly charging the photosensitive drum.

<Basic Experiment> Next, in the laser beam printer according to the first embodiment of the present invention described above, the core gradation conversion unit (11) integrally adjusts the gradation and the color tone of the color reproduction image. I confirmed whether I had the ability to do it. In particular, a basic experiment was conducted in the following manner in order to confirm whether the color tone could be adjusted rationally while maintaining the gradation. Since this is a basic experiment, only the color plate (C / M / Y plate) was tested, and the BL (K) plate was not used. (1) Color original image A standard quality brown pottery jar (transparent original) was used as the color original image. (2) Design material for each color plate Table 3 shows the design material for each color plate for the management and adjustment of color tone as a basic experiment. (Note 1) In the experiment A, the tone intensity value (y _S ) of the S portion was designated first, and then the tone intensity value of the M ₁ point (color tone control point) was obtained by the following equation (1) and the experiment was conducted. It is a thing. In addition,
The standard values of the following formula (1) are shown in Table 2. Dot% values of M ₁ point = (standard value of M ₁ point) × (tone intensity value specified in the S portion) / (standard value of the S portion) ......... (1) (Note 2) Experiment B is , M ₁ was adopted as the gradation intensity value of Experiment _{1, and} the standard value (Table 2) was adopted as the gradation intensity value of the S portion. (Note 3) Since the catch light portion is selected as the H portion of the color original image (pot), the halftone dot% value of the H portion of all color plate images is "0".

[0077]

[Table 3]

The four experimental results of the basic experiment were all as expected in the light of experience. This means
The color tone management method using the <gradation conversion formula> of the present invention is rational. The contents of the four color reproduction images obtained from the basic experiment are as follows. (1) At all four points, the gradation (density gradation) is well reproduced in the entire dynamic range of the H to S parts, and the halftone volume feeling is also suitable for human vision. (2) The color tone of the vase is blue in Experiment A (No. 1 to No. 2), blue in the halftone area in Experiment B (No. 1 to No. 2), and the original image is in S part. It was a brownish street. It should be noted that these color tones are exactly the same as in practice.

Incidentally, the γ value for setting the color separation curve for each color plate of Experiment A (No. 1 to No. 2) and the halftone dot value (calculated value) at M ₁ point are as follows. (1) Experiment A (No. 1) C version γ = 0.45,% dot value of M ₁ point = 50.0000% M plate γ = −0.20,% dot value of M ₁ point = 30.9878% Y version γ = -0.18, M ₁ dot half value = 35.8678% (2) Experiment B (No. 2) C version γ = 0.45, M ₁ dot half value = 50.0000 % M Version gamma = -0.18, dot% values of M ₁ point = 26.9006% Y Version gamma = -0.20, dot% values of M ₁ point = 30,9878% Note, BL version gamma value Is γ = −0.25.

The outline of the basic experiment and the experiment A (N
Fig. 5 shows the color separation curve (gradation conversion curve) for each color plate used in o. 1) and execution B (No. 1). (A) in the figure
Is a combination of color separation curves that has been adopted as a standard in the industry for maintaining gray balance. The design materials are given in Table 2. (A) in the figure is a combination of color separation curves (gradation conversion curves) of each color plate of Experiment A (No. 1), and (B) is Experiment B (No. 1).
The combination of color separation curves (gradation conversion curves) of each color plate is shown.

<Application Experiment> In this experiment, a color separation experiment is performed by a method closer to the daily color separation work, and the color tone management method using the <tone conversion formula> of the present invention determines the color tone of the color print image. The purpose is to check whether or not it has a function for reasonably adjusting and managing. In this experiment, the tone control value (M ₁ ) was set so that the tone intensity value of the C plate image was 50%.
It became the point that becomes. In addition, the details of the adjustment of the color tone at the color tone management point (M ₁ ) (specific details of the correction and change of the color tone requested by the user, etc.) are defined by the halftone dot% of each color of C / M / Y of each color plate image. "DIC GRA" manufactured by Dainippon Ink and Chemicals, Inc. is used as the basic scale specified by the value.
FG Color Chart "(March 1991, second edition)
It was adopted. In this experiment, the halftone dot value of the color chart was read as the gradation intensity value (%) and adopted. In this experiment, six colors were selected from the color chart. In Table 4, the above-mentioned "DIC GRAF-G
6 types of colors selected from the "color chart" and designated gradation intensity values for color tone adjustment are shown.

In the above-mentioned color chart, the above-mentioned 6 kinds of colors have a gradation intensity value of C / M of 12 between 0 and 100.
It is displayed in stages, and Y / BL (having a constant gradation intensity value, for example, a gradation intensity value of 10% or 50% as shown in Table 4) is shown as a color overprinted thereon. Has been done. Therefore, the specified gradation strength value for color tone adjustment can be easily specified in the same chart, and Table 4 shows the specified gradation strength value. Needless to say, it is possible to examine whether or not the color specified by the above gradation intensity value is faithfully reproduced on the color plate image without causing deterioration of gradation. , The purpose of this experiment.

[0083]

[Table 4]

Table 5 below shows each color plate design material for this experiment prepared based on the material of Table 4 above. (Note 1) In this experiment, it is needless to say that the gradation intensity value at M ₁ point is the specified gradation intensity value for color tone adjustment in Table 4. (Note 2) In the experiment A of this experiment, the gradation intensity value for the M / C plate of the S part was obtained by the following equation (2). For C plate, the value in Table 2 (standard value for maintaining gray balance) (95%)
It was adopted. The standard values of (2) below are shown in Table 2. When the calculation result by the following formula (2) exceeds the standard halftone dot% value, the standard halftone dot% value is adopted. S portion of the dot% value = (standard value of the S portion) × (tone intensity value specified in the M ₁₎ / (standard value of M ₁₎ ......... (2) (3) color original image (pot Since the catch light portion is selected as the H portion of), the halftone dot% value of the H portion of all color plate images is “0” (zero). (Note 4) The BL version (black) version is a skeleton type, that is, the starting point (SP) of black ink is M
_One point was set, and the end point (EP) was set as the S section. In addition, the maximum halftone dot% value of the BL plate put in the S part is 8 in Experiment A.
0% and 70% in Experiment B.

[0085]

[Table 5]

The results of the applied experiments were all as expected, as in the basic experiments. The color tone at the color tone management point (M ₁ ) obtained in the color reproduction image is completely in agreement with the color tone on the color chart as the basic scale, and the gradation is not limited to the entire dynamic range of the H part to the S part. The color tone was also natural to human eyes. That is, based on the results of the above-mentioned applied experiments, the color separation technique using the <tone conversion formula> of the present invention as a tool further integrates the tone adjustment and the tone adjustment when performing the tone adjustment management. Above, it was confirmed to have rationality.

FIG. 6 is a block diagram of a laser beam printer apparatus according to the second embodiment of the present invention. The laser beam printer according to the second embodiment uses a TV signal as the image information signal 10 'of the color original image. The TV signal 10 ′ correlates with the image information value of the object to be reproduced, which is similar to the first embodiment by utilizing the photoelectric conversion characteristic curve of the image pickup device such as CCD for picking up an object. It goes without saying that it has already been converted into the image information value (x value) correlated with the light amount.

The image information signal 10 'is input to a gradation adjusting unit 11' based on <gradation conversion formula>, subjected to gradation conversion processing, and color channel select (CHS).
12 'is input to each engineering system for color 1'a-1'd. Next, the laser beam modulated based on the signal output from each color engineering system (1'a to 1'd) has a halftone corresponding to the image information signal on each photosensitive drum 2a 'to 2d'. An electrostatic latent image is formed, and the latent image is transferred as a color image onto the recording paper on the conveyor belt 7'by the electrophotographic process.

In the production of a color reproduction image by the laser beam printer of the present invention, the coverage factor (pixel density value) of the pixel is changed by modulating the dot size such as a dot in the printing technique. This may be done (dot size modulation), or by devising the arrangement of prescribed dots (dots of a certain size) as seen in the dither matrix method (dot density modulation).

[0090]

The laser beam printer of the present invention can perform color separation by integrating both the gradation and the color tone by using a specific <gradation conversion formula> for the gradation conversion unit which is the core component of the laser beam printer. It is a thing. It was difficult in the prior art to integrate the adjustment of gradation and color tone quantitatively and rationally, which is a breakthrough point of the present invention.
In the prior art, when trying to answer the needs of the color tone adjustment (color tone correction, change) of specific parts, specific portions, and even the entire image that have high market needs (high demand), the color tone adjustment is quantitative. In addition, it is impossible to produce a high-quality color duplicate image because the color tone of the part concerned and other parts are unbalanced and the tone of image combination (gradation and color tone) is distorted. It is the current situation.

On the other hand, the color separation (gradation conversion) technology incorporated in the heart of the laser beam scanner of the present invention is
By adopting and operating a specific <Gradation conversion formula>, gradation adjustment and color adjustment can be quantified completely, and color original image can be color-separated for the purpose. It is possible to efficiently produce a high-quality color reproduction image in which the color tone is adjusted as well as the reproducibility.

That is, the laser beam printer of the present invention is
It has the following excellent effects. (1) It is possible to rationally meet the needs for the quality of color reproduction images in the sophisticated, complicated and diversified market. (2) Production of color reproduction images, especially color separation work is quantitative,
Since it is practiced rationally, it has a remarkable effect on productivity improvement, work time reduction, efficient use of equipment, saving of consumables, and reduction. (3) In the production of color reproduction images, it is possible to pave the way to make the most of sensitivity and artistry. As a result, the high added value of the laser beam printer is realized.

[Brief description of the drawings]

FIG. 1 is a diagram showing a density characteristic curve of a color film (manufactured by Company F).

FIG. 2 is a schematic mechanism diagram of the laser beam printer according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of an output pattern (dither matrix).

FIG. 4 is a block diagram of the laser beam printer according to the first embodiment of the present invention.

FIG. 5 is a diagram illustrating an outline of a basic experiment of the present invention and a color separation curve (gradation conversion curve) used.

FIG. 6 is a block diagram of a laser beam printer according to a second embodiment of the present invention.

[Explanation of symbols]

 1 ............ Detection unit 2 ............ Color separation unit 3 ............ Gradation adjustment unit 11 ………… Gray conversion unit 4 ………… Output unit 5 ………… Color original image 15…. ………… Laser light source 16 ………… Developer 17 ………… Recording paper 18 ………… Fixer 19 ………… Charger

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G03G 15/01 B41J 3/00 A H04N 1/46 H04N 1/46 Z

Claims (8)

[Claims] 1. A laser beam printer for producing a halftone (halftone) color reproduction image by subjecting image information of a continuous tone color original image to tone conversion by a tone conversion section of the laser beam printer. The tone conversion section (1) shows a characteristic curve of a recording medium on which a color original image is recorded [a light quantity value (x value) incident on the recording medium and a density value (D value) formed on the recording medium. A characteristic curve that defines the relationship in the Dx orthogonal coordinate system] is used to obtain the light intensity value (x value) from the density value (D value). (2) The light intensity value (x value) Gradation conversion formula> is used to perform gradation conversion to obtain a gradation intensity value (y _n value),
And (3) a color tone adjusting function used during the gradation conversion, wherein the color tone adjusting function is (3) -1. H part (lightest part) to S part (darkest part) of the color original image. In the predetermined area between
A color tone management point (M ₁ ) for managing the color tone of the color reproduction image is set, and (3) -2. At the color tone management point (M ₁ ), the color tone adjustment condition is a desired color plate (C plate). , M plate, Y plate, and BL plate), and (3) -3. Level of the color plate that reflects the light amount value at the color tone management point (M ₁ ) and the adjustment condition of the color tone. The tone intensity value and the desired tone intensity values to be set in the H and S portions are substituted into the following <tone conversion formula> to determine the γ value, and the H of the color plate is determined.
A <grayscale conversion formula> for performing a grayscale conversion of the light amount values of the pixels from section S to section S into a grayscale intensity value (y _n value), and
(3) -4. <Gradation conversion formula> for each color plate whose γ value is determined
A laser beam printer having a color tone adjusting function configured to perform the gradation conversion of the light amount value of each pixel for each color plate and manage and adjust the color tone. <Gradation conversion formula> y _n = y _H + [α (1-10 ^−kx ) (y _S −y _H ) /
(Α-β)] In the above item <tonal conversion formula>, the meaning of each symbol are as follows; x: shows the (x _n -x _H). That is, a color original obtained in the same manner from the light quantity value (x _n ) corresponding to the density value (D _n ) of an arbitrary pixel point (n point) of the color original image obtained using the characteristic curve of the recording medium. The basic light amount value obtained by subtracting the light amount value (x _H ) corresponding to the density value (D _H ) of the H portion of the image is shown. y _n : Gradation intensity value set for a pixel on the color reproduction image corresponding to an arbitrary pixel point (n point) on the color original image. y _H : Gradation intensity value preset in the H portion on the color reproduction image corresponding to the H portion on the color original image. y _S : A gradation intensity value preset in the S portion of the color reproduction image corresponding to the S portion of the color original image. α: Surface reflectance of an image representation medium for recording a color reproduction image. β: Numerical value determined by β = 10 ^−γ . k: Numerical value determined by k = γ / (x _S −x _H ). However, x _S represents a light amount value (x _S ) corresponding to the density value (D _S ) of the S portion of the color original image obtained by using the characteristic curve of the recording medium. γ: arbitrary coefficient. 2. The laser beam printer according to claim 1, wherein the color original image is recorded on a photoelectric conversion element as a recording medium. 3. The characteristic curve of the recording medium is a photoelectric conversion characteristic curve that defines the relationship between the light quantity value (x value) incident on the recording medium (photoelectric conversion element) and the formed density value (D value). Item 3. A laser beam printer according to item 2. 4. The laser beam printer according to claim 1, wherein the color original image is recorded on a photographic light-sensitive material as a recording medium. 5. The characteristic curve of the recording medium is a photographic density characteristic curve that defines the relationship between the light quantity value (x value) incident on the recording medium (photosensitive material) and the formed density value (D value). Item 5. A laser beam printer according to item 4. 6. The laser beam printer according to claim 1, wherein the color original image is a color print (reflection type) original image. 7. The characteristic curve of a color print (reflective type) original image is defined by a relationship of a light quantity value (x value) and a density value (D value) of 1: 1. Laser beam printer. 8. A method of recording a color reproduction image on an image expression medium (recording sheet) includes (1) an image forming body having a uniformly charged photoconductive layer,
A latent image representing the pixel distribution of a color reproduction image is formed by scanning a laser beam, (2) the latent image is developed with toner, and (3) then transferred and fixed on a recording sheet. The laser beam printer according to claim 1.