KR920008900B1 - Device for reproduction of pictures - Google Patents

Abstract

No content.

Description

Image forming apparatus

1 is a diagram showing the relationship between the γ value and the shape change of the gradation characteristic curve.

2 is a correlation diagram of γ _n and H _n .

3 is a diagram for explaining the principle of matching individual density characteristic curves and reference density characteristic curves of color film original images.

4 is a diagram showing a gradation characteristic curve set for a non-standard document.

FIG. 5A shows an example in which an original image having a continuous gradation is expressed by the distribution of unit pixels in the pixel block.

FIG. 5B is a diagram showing a case where the size of the halftone dot is expressed in the photographic plate corresponding to the case of FIG. 5A.

6 is a block diagram of the chemical forming apparatus of the first embodiment of the present invention.

7 is a block diagram of the image forming apparatus of the second embodiment.

8 is a block diagram of the image forming apparatus of the third embodiment.

9 is a block diagram of the image forming apparatus of the fourth embodiment.

10 is a block diagram of the image forming apparatus of the fifth embodiment.

Fig. 11 is a diagram showing an image forming portion in the electrostatic lock type.

[Industrial use]

The present invention relates to an image forming apparatus capable of converting an image information signal obtained by photo-scanning an original image by a novel gradation conversion method to form a recording image excellent in gradation reproducibility.

More specifically, the present invention includes all of the objects to be reproduced on various document images (such as continuous grayscale images such as monochromatic or color photographs, and video images obtained from television or computer video signals). The image obtained from the image conversion process is converted by a gradation adjustment mechanism using a new gradation conversion formula to have a distribution of pixels corresponding to an original image excellent in reproducibility of gradation or color tone on the recording sheet based on the gradation conversion output signal. A method and apparatus for forming a recorded image.

[Private Technology]

When an image is formed on a recording sheet using an image forming apparatus such as a copying machine from an original image having a continuous gradation as in a photograph, the use of photosensitive paper as the recording sheet is applied to the original by the original processing (exposure) of the original. An image having a corresponding continuous gradation is formed (warm photograph recording).

On the other hand, in electrophotographic photocopiers which record images on plain paper, not photosensitive paper, image formation cannot be performed by analytical processing, and it is difficult to reproduce density gradation, and in particular, the formation of color images. In this case, it is not easy to adjust the color balance together with the above-mentioned density gradation.

For this reason, efforts have recently been made to improve the reproducibility to the gradation and color tone in the chemical conversion apparatus.

Formation of a recording image in this type of image forming apparatus is similar to a method of converting from continuous gradation to halftone gradation of photographic printing in printing, and an image obtained by photoscanning of an original image having a continuous gradation such as a photograph It is intended to form an image on a recording site by processing an information signal and forming a distribution of pixels having a gradation or color tone corresponding to an original image by the signal.

However, in the current image forming apparatus, when reflecting the gradation characteristics of the original image on the recording image by the final pixel distribution, what characteristics should the distribution of the pixels have, and how to obtain such a pixel distribution? It is a phenomenon that no satisfactory reproducibility of gradation or color tone is obtained because no scientific examination has been conducted on whether or not it should be done.

In other words, in the pixel block of the recording image corresponding to the sample point with respect to the density value of the sample point of the original image, the ratio of the number of unit pixels constituting the pixel block is recorded. No relational expressions have been developed, and at present, these device makers are forced to rely on decisions made based on experience, emotion or a limited number of fixed conditions.

For this reason, if the device maker did not imagine an image of an image quality, for example, a non-standard color (such as an overly-exposure of an overexposure or an overly-dark one for an underexposure), such as a color film document, a desired recording image excellent in gradation and color tone may be used. Is difficult to get.

Therefore, not only originals having standard image quality, but also non-standard documents described above can obtain desired image quality, and the image quality can be arbitrarily changed or corrected (gradation or color tone). Flexible image forming apparatuses have not been developed.

This means that as mentioned above, it is not scientifically understood which pixel concentration value the conventional image forming apparatus should correspond to the density value of the desired sample point of the original image.

[Problem to Solve Invention]

The cause of the above-mentioned problems in the conventional image forming apparatus is that, when the recording image is formed by the distribution of the final pixel from the original image such as the continuous gradation image, it also plays an important role in its first step. The idea is to fix the gradation conversion of an image.

That is, in the pixel block of the recording image corresponding to the density value of the predetermined sample point of the original image, the ratio of the number of unit pixels to be recorded with respect to the number of unit pixels constituting the pixel block (hereinafter also referred to as "pixel concentration value"). The conventional way of thinking about gradation conversion is not to say, "You must rely on scientifically rational conversion means," but it depends only on experience and feeling.

In view of such a situation, the present inventor has made intensive studies based on the basic recognition that a rational gradation conversion technique must be established for the ultimate rationalization of the image forming process and the formation of a high quality recording image.

[Means for solving the problem]

According to the present invention, the present invention processes an image information signal obtained by photoelectric scanning or the like from an original image with a gradation adjustment mechanism, and based on the processing signal, a recording image by distribution of pixels corresponding to the original on the recording sheet based on the processing signal. In the image forming apparatus for forming, the basic gradation value x of an arbitrary sample point in an original image based on an image information signal obtained from an original image (the density value at the sample point and the moving image image). Difference between the density value in the outermost part) and the ratio y of the number of unit pixels to be recorded with respect to the number of unit pixels constituting the pixel block corresponding to the electrosample point in the recording image to be formed, An image forming apparatus characterized in that the conversion process is performed by the relation (1) >

<Relationship>

only,

x: basic concentration value of arbitrary sample point X in the original image.

Namely, the density value obtained by subtracting the concentration value in the outermost part H portion of the moving image from the concentration value at any sample point X of the moving image.

y: ratio of the number of unit pixels to be recorded with respect to the number of unit pixels which comprise the pixel block Y corresponding to electricity X in the recording image formed.

y _H : Ratio of the number of unit pixels to be recorded with respect to the number of the unit pixels which comprise the pixel block set with respect to the pixel block of the brightest part H of the formed recording image.

y _s : Ratio of the number of unit pixels to be recorded with respect to the number of unit pixels which comprise the pixel block set with respect to the pixel block of the darkest part S of the recording image to be formed.

α: reflectance of the recording paper.

β: A value obtained by β = 10 ^-r .

R: A value obtained by γ / (original image concentration range).

γ: arbitrary coefficient.

Respectively.

Hereinafter, the configuration of the present invention will be described in detail.

In photolithography, the density of an image having continuous gradation is represented by the size of the dot by dot dot processing. In an electrophotographic image forming apparatus using digital image processing, scanning is performed by laser beam or the like due to latent image formation on a photosensitive member. At that time, it is very difficult to change the diameter of the beam and to display multi-level gradation.

Therefore, the diameter of the beam is kept constant, and in the pixel block of the aggregate on the matrix of pixels as the minimum unit formed by the beam, the number of unit pixels constituting the pixel block and the image are recorded as an image (i.e., In many cases, the size of the halftone dot is matched by varying the ratio of the number of unit pixels (recorded by a toner or the like). Of course, in the digital image processing technology, a method of changing the size of dots (modulation of dots) in addition to the gradation expression method (dot density modulation method) of changing the number of dots (having a prescribed size) or arrangement as described above. Law). Here, an example of the former is demonstrated.

However, what can be considered as a basic component for the representation of an image is the pixel concentration value (the ratio of the number of pixels to be recorded in the number of unit pixels constituting a predetermined pixel block and the distribution thereof) expressed by the distribution of the foregoing pixels. Form) and the surface reflection density of the recording material (toner, etc.) of the image, and the human vision is, for example, a difference of 1% of the size of the halftone area in the print image. As can be seen from the fact that it has an ability to easily identify, the pixel concentration value expressed by the distribution of pixels in relation to the size of the halftone area plays an extremely important role as the image forming means.

That is, in the pixels to be written in any given pixel block, the latter is particularly large when the influence of the change in the amount of toner applied to them and the change in the size of the pixel on the gradation is very large. It is an extremely important question.

In addition, in the case of attempting to form a recorded image by the image forming apparatus in connection with the above, the quality of the original image varies greatly, the image forming process also has various characteristics, and the evaluation criteria of the image quality are not the same. They have a background such as things and must overcome their complexity and instability.

The concentration ratio of the pixel block of the value list (H) of the recording image by the distribution of the pixel to be created in as the same in fact converts the original image such as a continuous-tone image by recording the image by the distribution of the pixel (y _H) And the density ratio y _s of the pixel block of the darkest part S can be arbitrarily selected, and furthermore, a means for reasonably and easily adjusting and managing the gradation of the image from the brightest part H to the darkest part S. First of all it is necessary to provide.

The method of adjusting the gradation of the present invention, specifically, the method of adjusting the gradation specified in the above <Relational Expression (1)> is devised based on such a way of thinking.

First, the derivation process of the above <Relational Expression (1)> will be described.

The inventors of the present invention described the above-mentioned <Relation formula (1)> in order to reasonably convert the gradation (conversion of the continuous gradation to the halftone gradation) when creating a printed image of the halftone gradation from a color film document of the continuous gradation. The gradation conversion formula is proposed above. (See Special Aid 62-148912, Special Aid 63-2590)

The gray scale conversion equation (hereinafter referred to as &quot; Relational Expression (2) &quot;) proposed by the present inventors is not only for the creation of a print image but also for the creation of various duplicate images such as the creation of a recording image by the distribution of pixels related to the present invention. Although the present invention can be used as described above, it will be described below with reference to the creation of a print image.

<Relationship formula (2)>

only,

x: basic concentration value of arbitrary sample point X in the original image.

Namely, the difference between the concentration value at any sample point X of the moving image and the concentration value at the sharpest part H of the moving image.

y: The numerical value of the half-area area of the halftone point of Y corresponding to the electrical sample point X in a printed image.

y _H : The numerical value of the half-area of the half-dot of the desired arbitrary size halftone set with respect to the outermost part H of a printed image.

y _s : The numerical value of the half-area of the half-dot of the desired arbitrary size halftone set with respect to the darkest part S of a printing image.

α: reflectance of printing paper.

β: surface reflectivity of the printing ink.

R: Ratio of (printed image density range) / (original image density range)

Respectively.

Comparing <Relational Expression (1)> and <Relational Expression (2)>, the meanings of the β value and R value are different, and the <Relational expression (2)> has no definition of the γ value. These differences will be described later, and the derivation process of <Relational Expression (2)> will be described for better understanding of the present invention.

The relational formula (2), which obtains the numerical value y of the percentage of halftone area used in the preparation of the above-described printed image, is a density formula (photo density, optical density), which is generally accepted.

In other words,

D = log ^lo / I = log ¹ / T

Io = incident light intensity

I = reflected light or transmitted light

T = I / IO = reflectance or transmittance

Derived from

Applying the general formula for this concentration D to plate making printing is as follows.

Engraving. Density (D ') in printing =

here,

A: unit area.

d _n : the area of each mesh in the unit area.

α: reflectance of printing paper.

β: surface reflectivity of the printing ink

to be.

<Relational formula (2)> enables to arbitrarily set the halftone of desired size in the H and S portions of the print image in the density formula (D ') for plate making and printing, Incorporate a request to reasonably correlate the basis concentration (x) at the sample point with the corresponding numerical value (y) of the half-area area of the halftone at the sample point on the halftone image to approximate the theoretical and actual values. It is intended to be consistent with each other.

When the above <Relational Expression (2)> is applied to the gray scale conversion method of an image when creating a printed image, the reflectance (α) of the printing paper, the surface reflectivity (β) of the printing ink, and the print image concentration range / original image density Based on the numerical value of the inverse ratio (R), an arbitrary sample point (X) on the original image, while arbitrarily selecting the size of the halftone (y _H , y _s ) to be placed in the H and S portions of the printed image. It is operated to obtain a numerical value y of the half-area area of halftone dots at the corresponding sample points Y of the printed image from the basic concentration value x.

As a result, the density gradation of the original image (continuous gradation image) can be faithfully reproduced in 1: 1 on the printed image (dotted gradation image).

In addition, in the case of a multicolor board (generally considered to be one set of four plates of cyan (C), magenta (M), yellow (Y), ink (BL)), the reference plate (multicolor plate) In this case, as is well known, the work reference characteristic curve of the cyan plate (C) becomes the reference plate, that is, the halftone gradation characteristic curve (referenced x) as a reference for converting the density information of the original image to the target value of the printed image. Value is a graph obtained by graphing y and y values, and this is the basis for converting continuous gradation to halftone gradation. We can always make a reasonable decision by multiplying the appropriate adjustment based on the gray balance ratio of.

The work standard characteristic curves of the color plates thus determined are not only reasonable characteristic curves, but also the correlations related to the gradation and color tone between their characteristic curves are also reasonable and appropriate.

That is, when a printed image of halftone gradation is created from a manuscript image of continuous gradation, if the gradation conversion is performed based on the foregoing <Relational Expression (2)>, it is mistaken for the gradation conversion method of an image depending on the conventional hardness and sense. The gray scale of the image can be converted both reasonably and reasonably, and furthermore, reasonably can be adjusted even for the color tone which is closely related to the gray scale.

This makes it possible to obtain printed images having a natural concentration gradient and color tone for the human sense of sight. The above is the content of the present inventors.

However, in subsequent studies, it has been found that there are certain limitations in the operation of the aforementioned <Relational Expression (2)>.

The limiting thing,

* If the original image is of standard quality, it is extremely effective, but it will be able to cope with non-standard quality, especially extremely poor quality contents (e.g. exposure at the time of pre-shooting is over or under). There is no way.

If this is explained in terms of operational operation of the above <Relational Expression (2)>,

* In case of standard quality (standard manuscript), when the gradation conversion is carried out using the yellow ink's private printing concentration value (its typical concentration value is 0.9-1.0) in the molecule that determines the R value (large stimulus) with the printing ink. In the case of multicolor plates, plate C is manufactured using this value), although extremely effective, it is not particularly satisfactory for non-standard manuscripts with poor quality.

In the β value, the surface reflectance of the printing ink (a yellow ink is used as a reference as described above) or a value other than that can be satisfactorily satisfied.

In order to overcome the above limitations, it is necessary to match the halftone gradation characteristic curve, which is the work criterion for gradation conversion, to not only standard documents but also to non-standard documents, and the shape of the curves can be arbitrarily modified with reasonableness. .

As a result of the investigation, the inventors have found that satisfactory results can be obtained when the tone conversion is performed under the following conditions.

* R value = γ / (concentration threshold of original image)

γ-value = positive or negative

? value = A value obtained by? = 10 ^−r from a? value defining the above R value.

By operating the above <Relational Expression (2)> under the above conditions, it is possible to produce a printed image excellent in reconstruction of density gradation and its inadequate color tone from standard and nonstandard documents.

As described above, the description has been mainly focused on the creation of a print image of halftone gradation, but it goes without saying that the theory supporting the above-described gradation conversion operation can be dedicated to the creation of a recording image by distribution of pixels. It goes without saying that the gradation conversion equation suitable for the creation of the recording image by the pixel distribution becomes the <Relational Expression (1)> when the above-mentioned examination results are put together.

Next, the meaning of each term of <the relational expression (1)> of this invention, the characteristic of an exercise surface, etc. are demonstrated.

In the operation of the above <Relational Expression (1)>, the basic concentration value x must be obtained from the image information signal of the original image.

Such density information value may be any value as long as it reflects the physical quantity of the density of each pixel of the original image, and should be interpreted broadly. Synonyms include reflection concentration, transmission concentration, luminance, light amount, current, voltage value, and the like. These density information values may be taken out as a density information signal by photo scanning or the like.

In addition, in the said <Relational formula (1)> of this invention, the numerical value by a densitometer for the measurement of the basic concentration value (x) (For example, it has a density value of 0.2-2.70 as a figure of a positive color film, etc.) Also, y _H [pixel concentration value set in the pixel block of the outermost part H] and y _s [pixel concentration value set in the pixel block of the darkest part S] are expressed as a percentage value (for example, 5% or 95%). Y), the pixel concentration value recorded in the pixel block Y corresponding to an arbitrary sample point X of the original image is calculated as a percentage value.

In the operation of the above <Relational Expression (1)> of the present invention, it is free to use it by transforming as follows as well as using any processing, half-shape, or induction.

y = y _H + E (1-10 ^-hx ) (y _s -y _H )

only,

In the electrical deformation, α = 1. The surface reflectivity of the recording paper (substrate) is 100%. As a value of (alpha), you may make 1.0 practically.

In addition, according to the modification (α = 1.0), y _H can be set to the brightest part H and the darkest part S to y _s as scheduled.

This is x = 0 in the outermost part H of the recorded image, and in the darkest part S,

In other words,

=0) 따라서, -Rx=-γ로 되는 것으로부터 명백하다.(Rx = γ

= 0) Therefore, it is clear from the fact that -Rx = -γ.

In the operation of the above <Relational Expression (1)> of the present invention, the numerical values of α, β, and γ (this defines the β value by β = 10 ^−γ as described above) take various values.

In the present invention, by appropriately selecting these numerical values, any change in the gradation of an image can be reasonably performed regardless of the quality characteristics of the original image.

That is, the conversion processing method of the gradation of an image based on the above <Relational Expression (1)> of the present invention is extremely reproducible in reproducing the gradation and color tone of an original image, i.e., reproducing the quality of the original image to 1: 1 in the recorded image. Useful, but its usefulness is not limited to this.

In addition to faithfully reproducing the characteristics of the original image, the <Relational Expression (1)> of the present invention may be used to reasonably change or modify the characteristics of the original image by appropriately selecting the α, β, and γ values and the y _H and y _s values. It is extremely useful to do.

In detail, it should be noted that the user (worker) has the following degrees of freedom in the operation of the above <Relational Expression (1)>.

<His 1>: Use <Relational Expression (1)> for the purpose of forming a faithful image. In other words, the relational expression (1) should be operated with the primary objective of obtaining the same thing as the visual sensory image when observed with the human eye. This attitude of gradation adjustment is described in the present invention by the term &quot; (image) gradation (conversion) &quot;.

<His 2>: Use <Relationship (1)> to change or correct the original image from the technical need of image formation to the artistic request or from the ordering party's request. In other words, <Relationship (1)> should be operated with the primary objective of obtaining the corrected or changed visual sensory image itself when observed with the human eye. This attitude of gray scale adjustment is described in the present invention by the term &quot; (image) manufacturing (correction) (or alteration) &quot;.

In the case of forming a multicolor image using the above <Relational Expression (1)>, for example, in the case of replicating a color document by an image forming apparatus, it is well known in the field of printing and so on, namely, reflected light from a color warmer lamp. Spectroscopy with blue (B), green (G), and red (R) to obtain density information signals for each color, which are processed by the gradation adjustment mechanism using the above <Relational Expression (1)>. An image can be formed by relying on. At that time, the y value of the reference color plate (e.g., C plate), that is, the gray scale characteristic curve (y value of the reference color plate) is calculated and the y value with respect to the x value is plotted. The gradation characteristic curve having the same shape as that of the characteristic curve is obtained), and the gradation characteristic curves of the other color plates (M plate and Y plate) are based on the gray and balance ratio of each ink based on the y value of the color plate as the reference. Since it can be reasonably determined by multiplying an appropriate adjustment value, an image can be formed using these gray scale characteristic curves.

The y value for each color plate determined as described above, that is, the gradation characteristic curve for each color plate is defined by <Relationship (1)>, and is not only a reasonable characteristic curve but also related to the gradation and color tone between the characteristic curves. Interrelationships are reasonable and appropriate.

In the image forming apparatus of the present invention, in the gradation adjusting mechanism thereof, the exposure scanning beam is modulated by an algorithm of <Relational Expression (1)>, and arithmetic processing is performed in accordance with a predetermined pattern of distribution of pixels to sequentially process pixels. This can be done.

For example, in the order of FIG. 5A as shown in FIG. 5, the distribution of pixels to be recorded is in a positional relationship that is mutually distributed within the pixel block as the number of pixels to be recorded is increased. It is also conceivable to volcano in a shape swirling outwards sequentially from the center of the pixel block, and in such a case, it is approximated to the halftone in the photo plate making. In addition, in the order of FIG. 5B, the halftone point which has the area corresponding to the number of calcinations in the order of FIG. 5A is shown. The pixel block has been described here as a matrix of 4x4, but the gray level of 17 steps is expressed by this.

In general, an n × n matrix pixel block expresses the gray level (0 to 100%) of n ² +1 steps.

Thus, in the matrix type pixel block, a method of expressing the density of an original image such as a continuous gradation image by the distribution of pixels to be formed is generally known as a dither or a matrix matrix method. For example, Japanese Patent Application Laid-Open No. 58-58134, 58-114569, 59-52969, 60-141585, 62-186663, etc.).

As described above, when a recording image is formed by the image forming apparatus of the present invention, the gray scale is incorporated by incorporating a hard or soft to perform gray scale conversion based on the above <Relational Expression (1)> in the gray scale adjusting mechanism. As a matter of course, it is possible to obtain a recorded image excellent in reproducing a color tone or a recorded image arbitrarily corrected or changed in image quality of an original image.

Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to the thing of these Examples, unless the summary of this invention is exceeded.

As described above, the gradation adjustment mechanism portion for forming the recording image by the image format apparatus of the present invention has the greatest feature in that the gradation is converted by &lt; Relational Expression (1) &gt;. Therefore, the aspect in which <Relational formula (1)> is sufficient and complete operation, especially the handling of (gamma) value, is demonstrated.

EXAMPLE

(1) About the determination method of γ value employed in <relational formula (1)>,

In the present invention, when the recording image is formed by the image forming apparatus of the present invention, the greatest feature of the present invention is to perform the conversion process of the incremental gradation in the process of creating the recording image based on the above <Relational Expression (1)>. Have

In such a case, it goes without saying that it is desirable to form an image of the same quality as that of a recorded image in which the content of content is formed from a standard document, even if the quality of the document is very different, such as light or dark.

To do this, it is necessary to obtain a gradation characteristic curve that defines the relationship between the x value and the y value giving the same thing as the recorded image obtained from the standard document without being dependent on the quality of the original image.

In <Relational Expression (1)> of the present invention, it is the γ-value that can greatly change the shape of the gradation characteristic curve thereof.

Hereinafter, a method of determining the gamma value which is extremely important in the operation of <Relational Expression (1)> will be described. The image forming apparatus of the present invention can form a recording image excellent in reproducibility of gradation and color tone only by reasonably determining this gamma value.

Table 1 shows how the y value (that is, the pixel concentration value) changes for various gamma values. In Table 1, while changing the value of γ (as shown in Table 1, the value of γ value = 2.00 to -0.20), the formula (1) was expressed by y _H = 3%, y _s = 95%, α = 1.00, β. = 10- ^γ , R = β / (concentration threshold of the original image) = γ (2.8 ~ 0.2) in each concentration step (calculated under the conditions of the original image, each concentration step is divided into nine steps) It is to show y value.

TABLE 1

<Relationship between y Value and y Value>

Note) The numbers in the table indicate the y value (pixel concentration value,%) at each concentration step.

(2) The pixel concentration values of H and S are both 3% and 95%.

According to Table 1, when the gamma values are converted, individual gray scale characteristic curves corresponding to each are obtained. Therefore, it is good to perform gradation conversion by setting the optimal one from the quality content of a given original image. The results of Table 1 are shown in FIG.

Therefore, when a manuscript image having a predetermined quality content is given, the problem is how to reasonably determine the optimal gamma value to be employed in <Relational Expression (1)>.

As an original image, in particular, a monochromatic or colored film that is faithful in reproducing gradation or color tone is used as an original, and a method of determining the gamma value to be adopted in accordance with the image quality of the original is to be established. This is because it is thought that it is useful for other manuscript images if a method of determining the gamma value effective under a monochromatic or color film document with high reproducibility of gradation is established.

If you analyze the image quality of the original color film in detail, you can compare the image quality of the originals such as white key (photographed with exposure over light) and low key (photo taken with exposure index) with standard color film originals shot with standard exposure. In comparison, it is different.

However, the difference in the image quality of the color film original can be objectively defined by paying attention to the advantages from the fact that the difference in the exposure amount directly affects the darkest density value H _n of the original.

As proposed by the present inventors and the like, in the case of a standard document (exposure of proper exposure), when considering that the value of γ is 0.9-1.0, the correlation between H _n and γ may be obtained.

The reason why H _n is selected is that the concentration region is important in the vicinity of the sharpest part in the reproduction of the gradation. Theoretically, it may be said that the darkest concentration value S _n of the manuscript may be selected.

Therefore, experiments were conducted to obtain a relationship between H _n and gamma values by forming a recording image having excellent image quality using various color film documents. The experimental data are shown in Table 2. In Table 2, Experiment No. 2 is a standard document, and 0.9 was adopted as the gamma value.

TABLE 2

(Note) H _n and S _n indicate the darkest and darkest density values of a given individual color film document.

From these experiments, γ can be reasonably determined by the following equation.

(Iii) When the relationship between γ _n and H _n in Table 2 is graphed as shown in Fig. 2 (epoch graph), γ _n is obtained by the following equation.

γ _n = γ _o ± | D _n | tanα

However, γ _o = 0.90

D _n = H _n -H _o

H _o = Minimum concentration of the standard document, 0.2 for this experiment.

tanα represents the tangent as shown in FIG.

The ± sign is + when H _n > H _{o and} -when H _n <H _o .

(Ii) Other standard manuscripts (concentration range 0.20 to 2.80) were formed by gamma _o = 1.00, and experiments were performed to obtain the same recording images from various color film manuscripts. As a result, the relationship between γ _n and H _n can be defined as follows.

(A) γ _n = 1.70 = 2.2961 (log H _n +1) (Relational expression obtained when γ _n , H _n are expressed in logarithm scale)

(B) γ _n = 1.70 to 2.3 (log H _n +1) (relational expression obtained when γ _n is normally scaled and H _n is represented as logarithmic scale)

From the above, in order to reproduce a recording image having excellent reproducibility of gradation by the image forming process of the present invention from an original image having only the quality contents according to the thousandth difference, first, γ _n is determined from the H _n value of the original image, and then < It is only necessary to adopt the gamma value of 1) &gt;

In the gradation adjustment mechanism portion of the image forming apparatus of the present invention, in order to operate the <Relational Expression (1)> based on the γ value determined as described above, the mechanism for measuring H _n of various original images on the chemical conversion apparatus, H _n. What is necessary is just to add the mechanism which calculates (gamma) value from a. Or you may leave these measurements and calculations to an operator.

(2) In the method of fixing (correction) the γ value employed in the <Relational Expression (1)>, in the above-mentioned <Relational Expression (1)>, the method of determining the aforementioned γ value is complicated. The recording image to be created by the present invention is strictly different from the recording image obtained from the standard document. It is natural to say that this is different from the minimum density value (H _n ) of color film originals and the minimum density value (H _o ) of standard documents.

As described above, in <Relational Expression (2)>, which is useful for the gradation conversion of a standard document, a copy image excellent in the reproducibility of hue as well as gradation with a value of γ = 0.9 (or a value between 0.9 and 1.0) is obtained. You can write

Therefore, in the operation of <Relational Expression (1)>, the concentration gradation of the original image must be adjusted (corrected) to the normalization density gradation in order to purify the value of γ to γ = 0.9 or the like. Hereinafter, the method of integerizing (gamma) value is demonstrated.

In the case of a color film document, the above-described density adjustment can be performed very reasonably. This is illustrated in FIG.

As is well known, the relationship between the exposure amount X of the color film sensitive material (note that it is different from the X of the sample point X described above) and the color film concentration D at that time is as shown by the basic concentration characteristic curve in FIG. will be.

The standard document and the non-standard document are based on whether or not the exposure dose is appropriate, and each density characteristic curve appears as having a specific range on the basic concentration characteristic curve.

In FIG. 3, the former is a reference concentration characteristic curve and the latter is shown as an individual concentration characteristic curve. (In FIG. 3, the exposure underneath is shown as a non-standard document).

Therefore, in order to adjust the density characteristic of the non-standard document to the density characteristic of the standard document, the basic density characteristic curve can be functioned very easily.

The basic concentration characteristic curve is defined as a function of D = F _D (X), as shown in Table 3 below. (Table 3 shows the inverse function)

In addition, it will be understood that the method of functionalizing the basic concentration characteristic curve shown in Table 3 is one example, and a simplified equation may be used.

TABLE 3

(Example of function display of basic concentration characteristic curve)

We use color film made by F company

(Weeks) showed a basic density characteristics in curves, X → D → to obtain the function f X _S (D) function to obtain the _D f D (X), that its inverse function shown in FIG. 3.

Note: In order to faithfully define the basic concentration characteristic curve, it is formulated in each domain of X or D.

In order to match the individual density characteristic curve of the color document to the reference density characteristic curve, the following procedure is used. (See Figure 3)

(Iii) From the density values of H and S of the color original image and the basic density characteristic curve (D = f _D (X)) of the color film-sensitive material of the color original, the individual density characteristic curve of the color original image is defined, Ii) Substituting the color values D _Hn to D _sn into X = f _x (D) to obtain the range of the color original image on the X axis, X _Hn to X _sn , and (i) the density characteristics based on this. Match the band X _Ho to X _so on the X axis of the curve. (Iii) Next, find the range of D axis, D _Ho ~ -D _so of the reference concentration characteristic curve.

Naturally, it goes without saying that when the individual density characteristic curve of the color document coincides with the reference density characteristic curve, the matching of both is unnecessary. In addition, image processing may be performed in the same manner as that of the reference concentration characteristic curve.

In the matching procedure of the individual and reference density characteristic curves above, it is normal that XR _o (exposure range of standard documents) and XR _n (exposure range of non-standard color documents) do not match XR _n to XR. It is necessary to match to _o (see steps (ii) and (iii) above).

Matching XR _n to XR _o consists of simple matching (an attitude that matches the marginal concentration values to the same value, regardless of the darkest position matching) and proportional matching (an attitude that matches both the peak and darkest concentration values). In FIG. 3, the proportional matching was performed mathematically.

As shown in Fig. 3, XR _n is substituted by substituting the concentration information value (D _n between D _Hn and D _sn) of the individual concentration characteristic curve into the basic concentration characteristic curve D = f _D (X). The density information value (D density information value between D _Ho and D _so , D _o ) of the color document adjusted by the X value adjusted to XR _o is obtained, but XR _n is adjusted to XR _o . The relational expression for calculating the X value after the calculation is as follows by simple calculation.

(1) For simple matching, X = f _x (D _n ) ± | m |

(2) In case of proportional matching, X = f _x (D _Ho ) + [{f _x (D _n ) ± | m |} -f _x (D _Ho )] ×

Where m is the required parallel displacement

XR _o : Exposure range of the standard density curve of the standard document on the X side

XR _n : Exposure range of the individual density characteristic of non-standard individual documents on the X side, of standard quality (D _Ho = 0.20, D _So = 2.80), of high-key (exposure oven) (D _Ho = 0.10) , D _So = 2.70), and those of the low key (exposure under) (D _Hn = 0.60, D _Sn = 3.20) are shown in Table 3 and match the individual concentration curves to the reference concentration curves under the basic concentration curve. The matching data at the time of use are shown in Table 4 below.

TABLE 4

Matching Data between Individual Concentration Characteristic Curve and Reference Concentration Characteristic Curve

In the above matching experiments, the density region (DR) of the three color film originals used was 2.60, so that one was simple matching and the other was proportional matching.

In the concentration values of D _n and D _o in Table 4, y values (pixel concentration values,%) were obtained by <Relational Expression (1)> based on D _o . The results are shown in Table 5. 4 shows the correlation between the y values in Table 5 and the D _n values.

The curve shown in FIG. 4 can produce a recorded image excellent in reproducibility of gradation from an original image of non-standard image quality. It is a gray scale characteristic curve defining the correlation between x and y values.

TABLE 5

(Gradation Characteristic Setting Data)

Integer of <Relation Formula (1)>: α = 1.00, γ = 0.90, y _H = 5%, y _s = 95%

In the gradation adjustment mechanism portion of the image forming apparatus of the present invention, in order to operate by fixing (correcting) the γ value of the relation (1), the mechanism for measuring the density of the original image in the image forming apparatus (H, S and H ~). Measurement of density over S), software or hard to match the individual density characteristic curve of the original image to the reference density characteristic curve must be incorporated, thereby recording images excellent in gradation and color tone from originals of any quality content. Can't write

(3) About the Forming Apparatus The imaging apparatus of the present invention will be described with reference to Figs.

FIG. 6 is a block diagram of the image forming apparatus of the first embodiment of the present invention. As shown in FIG. 6, the image forming apparatus of the present invention provides a transmission field or reflected light of an original image in R (red) and G (green). ), A detector 1 for spectroscopically reading B (blue), and a color separation unit 2 for converting the output signal of the detector 1 into color separation signals in Y (yellow), M (magenta), C (cyan), and K (black). A gradation adjusting unit 3 for obtaining an image gradation based on an appropriate distribution of pixels using the relation (1), an output unit 4 for outputting laser light based on an output signal of the gradation adjusting unit 3, And an image forming unit 17.

The laser beam output from the output unit 4 exposes the electrophotographic photosensitive member 18 in the image forming unit 17, and a latent image formed on the photosensitive member 18 is manifested in the developing unit 19. It is in the form of a toner and is transferred to the recording sheet 21 on the transfer drum 20 and fixed at the fixing unit.

In order to form a color image, each component color has a separate photosensitive member and a developing unit, and the formed toner images are transferred to a recording sheet sequentially, or a latent image of a component color is formed on one photosensitive member to form a toner image. Are transferred in order to repeat this process for each color component.

The detection unit 1 detects the transmission field or reflected light of each part of the original 5 by photoelectric conversion elements such as an electron multiplier or a solid state image pickup device (CCD), and outputs R, G, B, and USM signals as currents. The A / V converter 6 converts this signal into a voltage signal.

The color separation unit 2 converts the voltage signals of the R, G, B, and USM signals of the detection unit 1 into a concentration in a log amplifier 7 and converts them into concentrations. From the concentration in the basic masking (BM) 8, the black (K) ) Components are separated, and each component of Y, M, and C is separated again. Next, in the color correction section CC, Y, M, and C components are controlled and adjusted for each of the original colors of R, G, B, and Y, M, and C. Then, the black component of the original is UCR / In the under control removal (UCR) or under control addition (UCA) of the UCA part 10, the ratio expressed by three components of Y, M, and C is determined. After these Y, M, C, and K components are obtained, the area ratios of pixels of each component in the gradation control section of the gradation adjustment section IMC are conventionally obtained by the area ratio ye ', me', ce ', Although ke 'has been obtained and inversely log converted, in this embodiment, instead of the gradation control unit and the inverse log converting unit, the gray scale adjusting unit 3 is used, where Y', me ', from Y, M, C, and K are used. Conversion to ce 'and ke' is performed.

In the gradation adjustment section 3 of the present invention, in particular, the adjustment section 11 has the algorithm of <Relationship Expression (1) therein and applies <Relationship Expression (1)> to Y, M, C, and K, respectively, to obtain ye '. Find me, ce ', and ke'.

As the adjusting unit 11, a general-purpose computer having an algorithm of <Relational Expression (1)> as software, and having an I / F (interface) of A / D and D / A, and an algorithm as an internal logic, The electric circuit embodied, the electric circuit containing the ROM which holds the calculation result of the algorithm, the electric circuit containing the ROM which held the operation result of the algorithm, PAL, gate array, custom IC, etc. which are embodied with the internal logic. It can take many forms. In order to form an image corresponding to the density of the original image by the laser beam, the diameter and intensity of the laser beam are made constant as described above, and formed in the image blunt by corresponding to the area of the dot in the case of photolithography. Ji calculates the number of unit pixels and their distribution and outputs the data.

The area ratio of the pixels obtained by the adjusting unit 11 is input to the color channel selector 12, and the color channel selector 12 selectively outputs ye ', me', ce ', and ke' in order. This output is converted into A / D by the A / D converter 13 and input to the output unit 4. FIG.

In the output section 4, the dot control section 14 controls the laser beam due to the output section of the gradation adjustment section 3.

7 shows a second example of the experiment, and the conventional inverse log converting section 15 is used as it is. Therefore, the adjusting section 11 outputs ye ', me', ce ', and ke' in logarithmic form. do.

In this way, by converting one component in the conventional apparatus, <Relational Expression (1)> can be applied, and the existing system is converted into the system according to the present system with fewer changes than in the first embodiment. You can do it.

8 shows the third embodiment, and disconnects the inverse log converter 15 from the gradation control unit 16, leaving the conventional gradation control (IMC) unit 16 as it is. And the adjusting part 11 which outputs ye ', me', ce ', and ke' in the form of a logarithmic shape similar to the 2nd Embodiment is employ | adopted. The adjusting unit 11 receives the Y, M, C, K signals from the front end of the gradation control unit 16 and outputs the converted value to the inverse log converting unit 15.

FIG. 9 shows the fourth embodiment, and disconnects the connection between the inverted log converter 15 and the color channel selector 12 as it is.

That is, the adjusting unit 11 receives Y, M, C, K signals from the front end of the gradation control unit 16 and directly connects the color channel selector 12, and connects ye ', me', ce ', and ke'. Without being constrained by the conventional system, ye ', me', ce ', and ke' can be obtained with the optimum processing form as in the adjusting section of the first embodiment. In the same manner as in the third embodiment, the conventional system can be embodied by slight modification.

FIG. 10 shows the fifth embodiment, in which the entire conventional gray scale adjustment unit is constituted by the new adjustment unit 11 of the present invention. In this adjustment unit, the relational expression (1) can be applied.

6 to 10, the image forming unit 17 is of an electrophotographic type which forms an electrostatic latent image by scanning a laser beam on a photoconductor having photoconductivity. However, as a method of forming a recording image by distribution of pixels, various methods, for example, electrostatic siloxane and magnetic recording, can be adopted.

11 shows the electrostatically locked image forming section 22. As shown in FIG. This type of recording head comprises a plurality of recording electrodes 24 arranged in a direction perpendicular to or in contact with the electrostatic lock 23 made of a sheet-like dielectric moving as shown in FIG. A voltage is applied to each electrode of the electrostatic latent image. After the step of developing a toner by adding a toner to the latent image, it is the same as in the case of electrophotographic. A voltage as an output signal corresponding to an image to be recorded from 14 is applied to the recording head 14 as an electrode assembly.

11 shows the counter electrode 25 in which the electrostatic body 23 serves as a recording layer (dielectric material) and a base layer (resistance body), and is disposed at opposing positions of the recording electrode 24. Although not shown in the figure, magnetic recording type uses a magnetic material uniformly coated on the surface of a drum body, and applies a voltage as an image information signal to a magnetic recording head in contact with the surface thereof. The recording head and the surface of the recording body are moved relatively to form a magnetic latent image on the surface.

In order to develop this latent image, the use of a toner made of a magnetic material is carried out in the same manner as in the case of the electrophotographic elsewhere.

As described above, if the gradation adjustment unit of the conventional equipment is modified, the coordination between the relational expression (1) and other processing can be performed, and the system is optimized for high speed and compactness, and at the same time the cost performance per system (cost performance) ) Can be increased.

In addition, in the above embodiment, the color separation part has the same configuration as before, but the color correction (CC) part 9 and the USR / UCA / part 10 are not required by using the relational expression (1). Omitted color separation units may be employed.

In addition, a part related to the effect generally used, for example, the dote mask, the sharpness effect, etc. which are not directly related to this invention, abbreviate | omits description in the above Example.

(4) The usefulness of <Relational Expression (1)> Next, the usefulness of <Relational Expression (1)> applied to the gradation adjustment mechanism of the image forming apparatus of the present invention will be further explained.

This is a supplementary explanation for better understanding of the present invention, and will be described in detail mainly on the operation of <Relational Expression (1)> applied to the gradation adjustment mechanism of the image type apparatus of the present invention and its significance.

(A) Operation experiment of <Relationship (1)>

The following two experiments were conducted as a basic experiment for incorporating <Relational Expression (1)> into the tone adjustment mechanism of the image forming apparatus.

a) First of all, by inserting a desired value into <Relational Expression (1)> using a conventional simple calculator, that is, a trade name, Sharp a Pythagorean EL509A (manufactured by Sharp), the following table 6 (1) (2) (3) The gradation adjustment table of the images shown in Table 7, Table 8 was created. As a result, the time required for these operations was 3 hours, 2 hours, and 2 hours, respectively, including the check time of the calculation results.

b) The following experiment was also performed. The desired software obtained separately from the simplified personal computer (PC-9801-MZ, manufactured by NEC Corporation) is input as function data, and the basic concentration value (x) of the original image (continuous sol image) is recorded by the distribution of pixels corresponding thereto. In the imaginary pixel block, work was performed to adjust the ratio y of the number of pixels to be recorded (hereinafter referred to as the area ratio of the pixels to be recorded).

The result is natural, but the same numerical value as the result of manual calculation using the said simple calculator was obtained.

In addition, in this experiment, it is not necessary to use a special software for adjusting the gradation of an image for input to the personal computer, and use the N88-BASIC included with the personal computer to create and work. In other words, it only took an hour for his completion.

In addition, the gradation of the target image can be converted or corrected by software that can directly input the measured value by the densitometer from the highlight (H) to the shadow (S) of the original image in place of the original density value of the original image. It was confirmed.

Using these software, a desired density interval (for example, 0.05 to 0.00 to 1.00 and 0.10 to 1.00 to 3.00) is provided for the original image, and its value is input to the personal computer. Therefore, the area ratio y of the target pixel could be obtained.

In addition, by inputting density values from the highlight of the original image to the shadow, the corresponding area ratio y of the desired desired recorded pixel was obtained.

The area ratio y of the pixel to be recorded by the above software can be output either independently or simultaneously with a positive image or a negative image.

(B) The usefulness of the calculation result obtained from <Relational formula (1)> will be described below for the usefulness of Table 6 (1), (2) (3), Table 7, and Table 8 described above. Y value is the pixel concentration value.)

About Table 6 (1) (2) (3)

In Table 6, when a black and white image is formed from an original image by a document forming apparatus, the density of the image recording material such as a toner (in the table, the recording image concentration range is indicated, which corresponds to the r value in <Relational Expression (1)>). Ideal when the range of use of the area ratio of the pixel to be recorded (indicated as the standard maximum small concentration value, represented three cases of 0 to 100%, 0 to 98%, and 0 to 95%) is changed. In order to obtain the gradation characteristic curve, the table shows how the area ratio y (pixel concentration value) of the pixel at each sample point must be set.

In this table, even when the toners and the like have the same concentration, how does the ideal gradation characteristic curve change when the use range of the area ratio of the recorded appeal is changed (that is, when the r value is changed). You can see if it must be done.

In Table 6, the β value for determining the ε value is determined as β = 10 ^−γ . In this relationship, the recorded image concentration range = r-value = 1.0, and ε = 1 / (1-β) = 1.1111. In addition, it is a theoretical value when (beta) = (epsilon = 1.0) the value of the type same as pixel concentration value (%).

In addition, forming a black and white image based on the distribution of pixels corresponding to 1: 1 from an original image such as a continuous gray scale image, and obtaining a technique and a method capable of arbitrarily adjusting the gray scale characteristics of a black and white image is a method of multicolor image formation. It is also basic.

[Table 7]

As in Table 6, Table 7 shows the case where the density of the image forming material (toner, etc.) changes when the monochrome image is formed from the original image by the image forming apparatus (that is, when the recording image concentration range = r value is changed). For each sample point necessary for a human to form an image having the same image quality and the same image quality with respect to the visual sense, while the maximum small concentration use range is 0% to 100%. The area ratio y (pixel concentration value) of the pixel is taken as a list.

In other words, when the conditions are ideal, the area ratio y of the pixels on which the sample points are recorded on the ideal gradation characteristic curve corresponding to the density value of the image forming material (toner, etc.) to be used is a table.

[Table 8]

The basic conditions in Table 8 are the same as those in Table 7, but the percentage of the area of the pixel to be recorded for each sample point on the ideal gradation characteristic curve when the maximum concentration range (5% to 95%) is used (y The table shows whether or not (pixel concentration) should be set.

Until now, the color separation work in printing images, etc. is primarily focused on color correction by masking technology, and the work of gradation adjustment of images is basically only human experience and feeling or fixed number of fixed images. It only relied on the data. For this reason, it is necessary to make the gradation conversion technique at the time of making a duplicate image scientifically based on the aspect of the reproduction image etc. being copied.

<Relational Expression (1)> of the present invention performs gradation conversion in producing a duplicate image in a reasonable manner. The data in Tables 6 to 8, which show the correlation between the basic density value x of the original image obtained by <Relational Expression (1)> and the area ratio y of the pixel to be recorded, are used for the color separation operation during image formation. It is a useful basic resource for scientific review of various basic matters.

From each of these tables, what is the nature or principle that exists between the color separation work of the original image? It is also possible to extract what should be noted and proportioned in order to reasonably match his essence, principle and practice.

(C) Regarding application to correction (or change) of the gradation of <Relational Expression (1)>, <Relational Expression (1)> shows the conversion of the gradation of the image (i.e., a pixel having high fidelity from the original image of the continuous gradation). This is effective not only for converting to a gradation image by the distribution of, but also for modifying (or changing) the so-called gradation that corrects the original image itself.

The correction (or change) of the gradation of the image includes a change in the reduction / enlargement ratio of the recording image to be formed, the intention of the client, the type of the target image in the color document, the purpose of using the image to be formed, and the color scheme or image of the recording paper. In some cases, the concentration of the recording material (ink) must be used, but in any case, the operation of <Relational Expression (1) can be reasonably supported, and various color separation operations can be standardized and standardized.

In addition, according to the present invention, the image of the highlight portion and the shadow portion can be corrected (or changed) in the same manner. As shown in FIG. 1, it is apparent that the shape of the gradation characteristic curve (curve defining the correlation between the x value and the y value) can be arbitrarily changed by the corresponding r value.

Further, it was confirmed by the gradation conversion according to the relation (1) of the present invention that the color density in the highlight portion of the color document was automatically removed without taking special countermeasures.

Table 6 (1)

Recorded image concentration (r),

Relationship between the maximal small concentration value range and the pixel concentration value (theoretical value)

When improved: Y = y _H- (1-10 ^-h ) ¹ (y _s -y _u ) X: basic concentration,

α = 100%

y _H ~ y _s = 0 ~ 100%, 0 ~ 98%, 0 ~ 95% y: Pixel concentration value (%)

ε = 1 / (1β) theory

Table 6 (2)

Table 6 (3)

TABLE 7

Relationship between recorded image concentration range (r value) and pixel concentration value (y value) (sample point of image selects 1/8 point of image)

Range of pixel concentration used: 0% ~ 100%

TABLE 8

Relationship between recorded image concentration range (r value) and pixel concentration value (y value) (sample point of image selects 1/8 point of image)

Range of pixel concentration used: 5% ~ 95%

[Effects of the Invention]

The present invention achieves the following excellent effects.

1) Determine the correlation between the density value of original images, such as continuous gradation images, which are the most basic matters for image formation, and the area ratio of pixels to be recorded in the recorded images (images recorded by the distribution of pixels). In the past, it was based solely on irrational methods that were based solely on the experience and feeling of the worker or on a limited number of fixed conditions.

On the other hand, in this invention, in any case, it can reasonably determine by these <relational formula (1)>. In addition, the management of gradation (conversion, correction or change of gradation), which is the most important requirement when converting an original image such as a continuous gradation image into a recording image by distribution of pixels, does not simply remain in the gradation of the image. Since the image has a deep relationship directly to the color tone of the image, the present invention can reasonably manage the gradation and color tone.

That is, the image forming apparatus incorporating the algorithm of <Relational Expression (1)> of the present invention into the adjustment mechanism of gradation can theoretically and rationalize the gradation conversion work (color separation work) and simplify its work. It's very big.

2) By putting <Relational Expression (1)> into the gradation adjustment mechanism of the image forming apparatus, it is possible to rationalize and simplify the equipment and reduce the manufacturing cost.

In addition, the operation of these devices can be simplified and clarified to minimize the need for rework, thereby significantly reducing the consumption of consumable materials, and greatly improving the performance of the image forming apparatus.

In particular, the performance of the image forming apparatus has a great positive effect that a recording image excellent in gradation and color tone can be formed, regardless of the quality of the original image.

3) By adopting the <Relational Expression (1)>, the education and training of the technicians required in addition to the advancement of the image forming apparatus can be effectively performed through the operation of the <Relational Expression (1)>, and it is useless in daily work. Efforts can be eliminated, freeing up time for new creative research and development.

Claims (5)

The image information signal obtained from the original image 5 is processed by the gradation adjusting section 3, and based on the processing signal, distribution of pixels corresponding to the recording sheets 21 of the image forming sections 17 and 22 is performed. An image forming apparatus for forming a recording image by means of the above, wherein the gradation adjusting section (3) is a means for performing gradation conversion processing by the following &quot; (1) &gt; (17) and (22) are means for obtaining pixel concentration values of an image (sample point) on a recording sheet corresponding to an arbitrary sample point of the original image. <Relationship formula (1)>

However, x: The density | concentration value which subtracted the density | concentration value in the outermost part H of the image from the density | concentration value in arbitrary sample point X of an original image, ie, the density value in arbitrary sample point X of the said image. y: ratio of the number of unit pixels to be recorded with respect to the number of unit pixels which comprise the pixel block Y corresponding to said X on the formed recording image. y _H : Ratio of unit pixels to be recorded with respect to the number of unit pixels which comprise the pixel block set with respect to the pixel block of the brightest part H of the formed recording image. y _s : Ratio of the number of unit pixels to be recorded with respect to the number of unit pixels which comprise the pixel block set with respect to the pixel block of the darkest part S of the recording image formed. α: reflectance of the recording paper. β: A value obtained by β-10 ^- _r . R: A value obtained by r / (concentration range of the original image). r: arbitrary coefficient. Respectively. The distribution of the electropixels according to claim 1, wherein the image forming section 17 has a laser beam scanned on a photosensitive member 18 having a photoconductive layer evenly charged for recording pixels onto the recording sheet 21. Means for forming a latent image representing the latent image, the latent image being developed by the toner of the developing unit 19, and then transferred to the recording sheet 21 on the transfer drum 20, and fixed. Device. 3. The image forming unit (17) according to claim 2, wherein the image forming unit (17) specifies a series of operations or a part thereof, such as forming a latent image into the photosensitive member (18), developing into a toner, and transferring to a recording sheet (21). A toner of a different color, and the same operation is performed with a toner of a different color, and the same operation is repeated by the required number of colors as described below. Image forming apparatus, characterized in that means for. 2. A plurality of recording electrodes as claimed in claim 1, wherein the image forming section (22) is arranged in a direction perpendicular to the direction of movement with respect to the electrostatic lock (23) moving for the recording of pixels onto the recording sheet (21). And means for applying a voltage to the electrostatic latent body 23 to form a latent electrostatic image on the electrostatic lock body 23, developing the latent image with a toner, and then transferring the image to the recording sheet 21 and fixing it. Device. 5. The image forming unit (22) according to claim 4, wherein the image forming unit (22) identifies a series of operations such as the formation of a latent image on the electrostatic lock body (23), a phenomenon such as a toner, and a transfer to the recording sheet (21). Means for forming a color image by performing the same operation with a toner of a different color and performing the same operation with a toner of a different color, and repeating the same operation by the required number of colors in the same position on the same recording sheet, and then fixing it to form a color image. Image forming apparatus characterized in that.

Images