KR930004062B1 - Thermal printer - Google Patents

Abstract

No content.

Description

The Thermal Printer

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 view for explaining the principle of matching the individual density characteristic curves with the reference density characteristic curves of a color film original image.

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

5 is a block diagram showing a first embodiment of the thermal printer of the present invention.

6 is a block showing the second embodiment.

7 is a block diagram showing a third embodiment.

[Industrial use]

The present invention relates to a dermallin that can convert an image information signal obtained from an original image by a novel gradation adjustment method to form a recording image excellent in gradation reproducibility.

More specifically, the present invention is intended to duplicate all kinds of original images (continuous gradation images such as monochromatic or color photographs, and video images obtained from a television system or a video signal of a computer system). The image information signal obtained from the same) may be converted and processed under a gradation adjustment mechanism using a new gradation conversion formula to form a recording image on a recording paper based on the gradation conversion output signal. It relates to a thermal printer.

[Private Technology]

When copying an image onto a recording sheet by an image forming apparatus such as a copying machine from an original image having a gradation gradation as shown in the photograph, the use of a photosensitive paper as the recording sheet is performed by an analytical processing (exposure) of the original. An image having a corresponding continuous gradation is formed (silver dye photo recording). On the other hand, in a thermal printer apparatus that records images on plain paper instead of photosensitive paper, image formation cannot be performed by analytical processing, and reproduction of density gradation is difficult, especially in the case of duplication of color images. Color balance is not easy to adjust with the above mentioned density gradation.

For this reason, efforts have been actively made to improve the reproducibility of gradation and color tone in printer apparatuses. The formation of the recording image in the thermal printer is performed by photoinjection of an original image having a continuous gradation such as a photograph, such as a method of converting a continuous gradation from a photo plate in printing to a halftone gradation. By processing, the image is formed on the recording paper by an image composed of a distribution of pixels having a gradation or color tone corresponding to the original image.

However, in the current printer apparatus, it is the present reality that satisfactory gradation reproducibility cannot be obtained because the gradation adjustment method of processing image information signals obtained from original images for gradation reproduction is unscientific.

As is well known, the density gradation of a recorded image depends on the density display method of the pixel. In the case of a thermal printer, a method of displaying the density gray level of a pixel, which is a method of changing the coverage of a pixel by the size of a dot (size modulation method), and the coverage of a pixel as an arrangement number of a specified (same size) dot (Density modulation method) and using the recording material (ink) of the image having the same color concentration thereon, as can be seen in the thermal printer using sublimable dyes, There is a way to change the concentration (direct gradation labeling). However, in the case of copying an original image by a thermal printer, for a density value of a predetermined sample point of the original image, the coverage ratio, i.e., the density density measure of the pixel (hereinafter, simply referred to by dots of pixels of the recording image corresponding thereto) There is no scientific examination of what the pixel density value should be) and how to obtain such a pixel concentration value.

In other words, no scientific correlation has been developed as to which pixel concentration values should be correlated to the pixels of the recording image corresponding to the sample points with respect to the density values of the predetermined sample points of the original image. There is no choice but to rely on the manufacturer's prior decision on experience, feeling, or a limited number of fixed conditions.

For this reason, if the document is not of the image quality expected by the machine manufacturer, for example, a non-standard color (such as an overly-exposure of an overexposure or an overly-dark one for an under-exposure), a film with excellent gradation or color tone is desired. It is difficult to obtain image quality. Therefore, not only originals with standard image quality, but also desired image quality can be obtained from the above-mentioned non-standard originals, and also the quality of the originals can be arbitrarily changed or corrected (gradation or color tone). It is not possible to develop castle thermal prints.

This means that the conventional thermal printer does not scientifically correspond to the pixel concentration value with respect to the density value of a predetermined sample point of the original image.

[Problems that the invention tries to solve]

The above-mentioned problem in the conventional printer apparatus is caused by the fact that an image which plays a more important role in the first step is formed when forming a recording image by distribution of the final pixel from an original image such as a continuous gradation image. It is a way of thinking about the process of gradation conversion. In other words, when converting a density value of a predetermined sample point of an original image into a pixel concentration value of a pixel of a corresponding recording image, a conventional method of thinking about gradation conversion is not performed based on a scientifically rational gradation conversion means. It wasn't, ”he said, but it was based solely on experience and sense.

In view of such a situation, the present inventor has made diligent studies with the basic recognition that a rational image gradation conversion technology must be established for the ultimate rationalization of the image forming process and the formation of recording images having excellent quality.

[Means for solving the problem]

According to the present invention, the present invention is directed to a thermal printer for processing an image information signal obtained from an original image by a manufacturing adjustment mechanism and forming a recording image corresponding to the original image on a recording sheet based on the processing signal. In this case, the electric gradation adjusting mechanism has a basic concentration value (x) of an arbitrary sample point in the original image based on the image information signal obtained from the original image (the density value at the sample point and the density value at the sharpest part H of the same image). To a pixel concentration value y at a position corresponding to an electrosample point of a recording image to be formed, according to the following equation (1). .

[Relationship]

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

In the recording image formed by the thermal printer, the basic component constituting the recording image is the density value in the pixel (this is determined by the number and size of dots in the pixel of the recording image formed as described above). And the surface reflection density of the image forming material (ink and pigment), of which 1% of the size of the halftone area in the printed image is different. As can be seen from having the ability to easily identify by the difference in density, the pixel concentration value having a relation such as the size of the halftone area as an image forming means plays an extremely important role. In other words, paying attention to a certain dot, and examining the effect of the change in the amount of ink applied on the dot and the change in the dot size on the gray scale, the latter side is particularly large, and how the pixel concentration value is set. It is an extremely important question.

In relation to the foregoing, when a recorded image is to be formed by a thermal printer, the quality of the original image is the edge of the image, the image forming process also has various characteristics, and the evaluation criteria of the image quality are more consistent. They have a background such as disagreement and must overcome their complexity and instability.

From this, in converting an original image such as a continuous gradation image into a recording image having an intermediate tone by a thermal printer, the pixel concentration value y _H of the pixel block of the sharpest part H and the pixel of the darkest part S It is absolutely necessary to provide a means for arbitrarily selecting the pixel concentration value y _S of the block, and providing a means for rational and simple adjustment and control of the gradation of the image from the brightest part H to the darkest part S.

The method of adjusting the gradation of the present invention, specifically, the method of adjusting the gradation specified by the foregoing [Relational Expression (1)] is devised based on such a thinking method.

First, the derivation process of electricity [relationship (1)] will be described.

The present inventors, in order to reasonably perform gradation conversion (conversion of continuous gradation to halftone gradation) when creating a printed image of halftone gradation from a color film document of continuous gradation, and the like (Equation (1)) ] Was proposed earlier (see Japanese Patent Application No. 62-148912, Japanese Patent Application No. 63-2590).

The gray scale conversion formula (hereinafter referred to as [Relational Expression (2))] proposed by the present inventors not only creates a printed image, but also creates various copied images such as a recorded image in a thermal printer related to the present invention. Although the present invention can be used in the following description, the following description is limited to the creation of a print image.

[Relationship (2)]

When [Relational Expression (1)] and [Relational Expression (2)] are compared, the meanings of the β value and the k value are different, and there is no provision for the gamma value in [Relational Expression (2)]. These differences will be described later, and the derivation process of [Relationship (2)] will be described to help understanding of the present invention.

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

D = log ¹⁰ / I = log ¹ / T

Io = incident light intensity

I = reflected or transmitted light

I = I / Io = reflectance or transmittance

Derived from

The general formula relating to this concentration D is applied to plate making and printing as follows.

Concentration (D ') in engraving and printing

[Relational formula (2)] allows the density formula (D ') relating to plate making and printing to arbitrarily set halftones of a desired size in the H and S portions of the print image, and also in the continuous gradation image. Incorporate a request to reasonably correlate the basic concentration value (x) at any sample point with the numerical value (y) of the percentage of the half-area area of the halftone at the sample point in the halftone image. The observations were derived to approximate agreement.

In the case where the foregoing [Relationship (2)] is applied to the method of converting the gray scale 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 density area / original image density Based on the numerical value of the inverse ratio (k), arbitrary sample points (X) of the original image, while arbitrarily selecting the size (y _H , y _S ) of the desired halftone dots desired to be placed in the H and S portions of the printed image. It is operated to obtain the numerical value y of the half-area area percentage of halftone dots at the corresponding sample points Y of the printed image from the basic concentration value x of the image. As a result, the density gradation of the original image (continuous gradation image) can be faithfully reproduced 1: 1 on the print image (dotted gradation image).

In addition, in the case of multicolor plates (generally considered to be one set of four plates of cyan (C), magenta (M), yellow (Y), and black (BL)), the reference plate (in the case of multicolor plates) As shown, the cyan plate (C) becomes the reference plate), that is, the reference gradation characteristic curve (the previous x value and the reference point for converting the density information of the original image into the halftone area value of the printed image). This is a curve obtained by graphing y value, which is the standard for converting continuous gradation into halftone gradation.) When the other standard color work standard characteristic curve is used, the printing ink is adapted to the value of the standard y. By multiplying the appropriate adjustment value due to the gray balance ratio of, it can always be reasonably determined. The work reference characteristic curves of the color plates thus determined are not only rational characteristic curves, but also the relations related to the gradation and color tone between their characteristic curves are also reasonable and appropriate.

In other words, when a printed image of halftone gradation is made from a manuscript image of continuous gradation, the gradation conversion thereof is carried out based on the electric relation (2). The image tone can be converted arbitrarily and reasonably, and furthermore, the tone can be closely related to the tone. As a result, a printed image having a density gradient and color tone that is natural to human visual sense can be obtained. The above is the content proposed by the present inventors.

In subsequent studies, however, it was found that there were certain limitations in the operation of [Equation (2)].

The limit is

* If the original image is of standard quality, it is extremely effective, but it is not sufficiently compatible with non-standard quality, especially with extremely poor quality content (e.g. when the exposure is over or under). , Etc.

Explaining this from the point of view of the operational operation of the above [Relationship (2)]

* In the case of standard quality (standard document), gray scale conversion using a pulverization concentration value (a typical concentration value of which is 0.9 to 1.0) of a yellow ink having a large stimulus value as a printing ink on a molecule for determining k value can be performed. When (also in multicolor plates, plate C is manufactured using this value), it is extremely effective, but not particularly satisfactory for poor, non-standard manuscripts of the above quality content,

* In the β value, the surface reflectance of the printing ink (yellow ink is used as a reference as mentioned above) or a value other than that may not be sufficiently satisfied.

In order to overcome the foregoing 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 changed arbitrarily and arbitrarily. . As a result of the investigation, the inventors found that satisfactory results can be obtained when the tone conversion is performed under the following conditions.

* k value = γ / (density threshold of original image)

γ-value = positive or negative

* β value = The numerical value determined by β = 10 ^−γ from the γ value defining the k value.

By operating the electric relation (2) under the above conditions, it is possible to produce a printed image excellent in the reproducibility of density gradation and incomparable color tone from standard and non-standard documents.

The foregoing has focused on the creation of printed images of halftone gradations, but needless to say, the theory supporting the above-described gradation conversion can be dedicated to the creation of recorded images by a thermal printer.

It goes without saying that the gradation conversion equation suitable for the creation of the recording image by the thermal printer becomes [Relational Expression (1)] when the above-mentioned examination results are incorporated together.

Next, the meanings of the terms of the foregoing [Relational Expression (1)] of the present invention, the characteristics of the operating surface, and the like will be described.

In the operation of the foregoing (Relational Expression (1)) of the present invention, the basic concentration value x must be obtained from the image information signal of the original image. Such density information 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 can be taken out by taking the original image as a density information signal by photoelectric scanning or the like. In addition, in the electric relation (1) of the present invention, there is a numerical value (for example, having a density value of 0.2 to 2.70 as a personification of the positive color film) for the measurement of the basic concentration value (x). .) the radeunga in y _H [pixel is set to a pixel block of choemyeongbu (H) concentration values] and y _S percentage value in the darkest part (pixel concentration values to be set in the pixel block of S)] (for example, 5% to 95 Using a numerical value of%.), [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 electric relation (1) of the present invention, it is also possible to use it by modifying as follows, as well as by using any processing, deformation, or induction.

y = y _H + E (1-10 ^-kx ) (y _S -y _H )

only,

The former modified example is alpha = 1. This is to make the surface reflectivity of the recording paper (substrate) 100%. As a value of (alpha), you may make 1.0 practically.

In addition, according to the electric modification example (α = 1.0), y _H can be set to the brightest part H of the recording image by the thermal printer and y _S to the darkest part _S as scheduled. This means that x = 0 in the outermost part H of the recorded image, and x = [original image concentration range] in the darkest part S,

=γ), 따라서That is, (kx = γ

= γ), thus

It is evident from -kx = -γ.

In the operation of the foregoing (Relational Expression (1)) of the present invention, the numerical values of α, β, and γ (which defines the β value by β = 10 ^−γ as described above) take various values. In the present invention, by appropriately selecting these numerical values, it is possible to reasonably perform the conversion process of the gray level of the image, whatever the quality characteristic of the original image.

That is, the conversion processing method of image gradation based on the electric relation (1) of the present invention is extremely useful for reproducing gradation or color tone of an original image, that is, reproducing the state of the original image in a recorded image 1: 1. However, his usefulness is not limited to this. In addition to faithfully reproducing the characteristics of the original image, the foregoing [Relational Expression (1)] of the present invention rationally changes the characteristics of the original image by appropriately selecting the α, β, γ values, and furthermore, y _H , y _S. It is extremely useful for making modifications.

In detail, it should be noted that the user (the person in charge) has the following degrees of freedom in the operation of the electric relation (1).

[1]: [Relationship (1)] is primarily aimed at obtaining the same visual-sensitized image as observed by the human eye when using the image for the purpose of forming an image faithful to the original image. In view of this, the relation (1) is to be operated, and the attitude of the gradation adjustment is described in terms of " (image) gradation conversion " of the present invention.

[His 2]: When using the relational expression (1) to change or modify the manuscript image in the technical need of image formation, the artistic request, or the client's request, The first goal is to obtain the correction or change of the image itself, and to operate the [Relational Expression (1)]. In the present invention, the attitude of the tone adjustment is corrected (or changed) of the image (gradation). It is described as a term.

In the case of forming a multicolor image using electricity (Relational Expression (1)), for example, in the case of replicating a color document by a thermal printer, it is well known in the field of printing or the like, namely, reflected light from a color document. The spectrophotometer is spectroscopically analyzed with blue (B), green (G), and red (R) to obtain density information signals for each color, and this is processed by a gradation adjustment mechanism using electricity (Relational Expression (1)). An image may be formed based on the information. At that time, y values of the reference color plate (e.g., C plate), that is, the gray scale characteristic curve (y value of the reference color plate and the y value with respect to the x value) are plotted. And the gray scale characteristic curve of the other color plate (M plate, Y plate) is the y value of the color plate as the reference, and the gray balance ratio of each ink is determined. Since it can be reasonably determined by multiplying an appropriate adjustment value according to the above, an image may be formed using these gray scale characteristic curves.

The y value for each color plate determined as described above, that is, the gray scale characteristic curve for each color plate is not only a reasonable characteristic curve because it is defined by [Equation (1)], but also related to the gray scale and color tone between the characteristic curves. The interrelationships between them are reasonable and appropriate.

As described above, when the recording image is formed by the thermal printer, the gray scale is, of course, by incorporating a hard or soft to perform gradation conversion based on the electrical relation (1) in the gradation adjustment mechanism. A recorded image excellent in reproducing a color tone or a recorded image arbitrarily corrected or changed in quality of an original image can be obtained.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited only to these Examples, unless the gist of the present invention is exceeded.

As described above, the present invention has the greatest feature in that the tone adjustment mechanism of the thermal printer allows the tone to be converted by the relational expression (1). Thus, an aspect in which the operation of [Relational Expression (1)] is sufficient will be described from the handling of the γ value in particular.

EXAMPLE

(1) Regarding the method for determining the gamma value employed in [Relational Expression (1)], the present invention relates to the process of converting the final gradation in the process of creating a recording image when the recording image is formed by a thermal printer. The biggest feature is that it is performed based on the foregoing (Relational Expression (1)).

In such a case, it would be natural to wish that, even from a manuscript image whose quality contents vary widely, such as light or dark, a quality identical to a recorded image formed from a standard standard manuscript is formed.

To do this, it is necessary to obtain a gradation characteristic curve that defines the relationship between the x value and the y value that give the same quality as the recorded image obtained from the standard document, without being influenced by the quality of the original image. In the relation (1) of the present invention, it is a gamma value that can greatly change the shape of the gradation characteristic curve.

Hereinafter, a method of determining the gamma value which is extremely important in the operation of [Relational Expression (1)] will be described. The thermal printer of the present invention can form a recording image having excellent reproducibility of gradation and hue as a ratio by rationally determining this γ.

The first table shows how the y value (that is, the pixel concentration value) changes for various gamma values. A first table, while changing γ value (employing a γ value = 2.00 ~ -0.20, as shown in the first table), the electrical relationship (1), _H y = 3%, y = 95% _S, α = 1.00 , each concentration step calculated in the condition of β-10 ^-γ and k = γ / (concentration threshold of the original image) = γ / (2.8-0.2) (the first table shows the concentration region of the original image in nine steps). The y value in ().

[Table 1]

[Relationship between y Value and y Value]

(Note) ① The numbers in the table indicate the y value (pixel concentration value,%) in each concentration step.

The pixel concentration values set at (H) and (S) are all 3% and 95%.

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

Here, when a manuscript image having a predetermined quality content is given, the question is how to reasonably determine the optimal gamma value to be employed in [Relational Expression (1)].

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

If you analyze the image quality of the original color film in detail, his image quality such as Hi-key (taken by exposure ober) or Low-key (taken by exposure under) is the standard color film document taken with standard exposure. Compared with, However, the difference in the image quality of the color film document can be objectively defined by paying attention to the advantage that the difference in the exposure dose directly affects the maximum concentration value Hn of the document. As the inventors have proposed above, the standard In the case of a manuscript (exposure is appropriate), considering γ taking a value from 0.9 to 1.0, we can find the correlation between Hn and γ. The reason why Hn is selected is that the concentration region near the sharpest part is important in the reproduction of the gradation. Theoretically, it is needless to say that the darkest concentration value Sn of the manuscript may be selected.

Thus, experiments were conducted using various color film documents to form a recording image with excellent image quality and to find the relationship between Hn and? Values. The experimental data are shown in Table 2. In Table 2, Experiment No. 2 is a standard manuscript, and 0.9 is adopted as the γ value.

[Table 2]

(Note) Hn and Sn represent the brightest and darkest concentrations of predetermined individual color film originals.

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

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

γn = γo ± | Dn | tanα

(Ii) In addition, an experiment was performed in which a standard image (concentration area 0.20-2.80) was formed under? O = 1.00 and a recording image of the same quality was obtained from various color film originals. As a result, the relationship between γn and Hn could be defined as follows.

(A) γn = 1.70-2.2961 (log Hn + 1)

(Relational expression obtained when both γn and Hn are expressed in logarithmic scale)

(B) γn = 1.70-2.3 (log Hn + 1)

(Relational expression obtained when γn is represented by normal scale and Hn by logarithmic scale)

As described above, in order to reproduce a recording image having excellent reproducibility of gradation by a thermal printer from an original image having different quality contents, γn is first determined from the Hn value of the original image, and then γ of [Equation (1)] is determined. In this case, the tone may be adopted as a value, and the tone conversion process may be performed.

In the gradation adjustment mechanism of the thermal printer, in order to operate below the γ value determined as described in [Relational Expression (1)], the γ value is calculated from the mechanism for measuring Hn of various original images on the thermal printer. What is necessary is just to add the mechanism. Alternatively, these measurements and calculations may be left to the operator.

(2) About a method of fixing (correction) of the γ value employed in [Relational Expression (1)],

In the operation of the relation (1) of the present invention, the determination method of the above gamma value is complicated, and the recording image produced by this method is strictly different from the recording image obtained from a standard document. It is natural to say that the maximum density value (Hn) of the color film original is different from the maximum density value (Ho) of the standard document.

As described above, in [Relational Expression (2)], which is useful for the gradation conversion of a standard document, a value of? You can write Therefore, in the operation of [Relational Expression (1)], in order to purify the value of gamma to be equal to gamma = 0.9 or the like, it is necessary to adjust (correct) the density gray level of the original image. 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 the difference from the X of the sample point X described above) and the color film concentration D at that time is shown in the basic concentration characteristic curve of FIG. As shown.

The standard document and the non-standard document are based on whether the exposure amount is appropriate or not, and each density characteristic curve is represented as having a specific range on the basic concentration characteristic curve. In FIG. 3, the former is shown as the reference concentration characteristic curve, and the latter is shown as the individual concentration characteristic curve (in FIG. 3, the non-standard manuscript and the under exposure are also shown).

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.

A base concentration curve electricity is to be defined a function of, as shown in Table 3, D = f _D (X) (Fig indicates inverse function to the third table). In addition, the method of functionalizing the basic concentration characteristic curve in Table 3 will be interpreted as an example, and a more simplified formula may be used.

[Table 3]

(Example of Function Display of Basic Concentration Characteristic Curve)

I use color film made in F company

Note: In the basic concentration characteristic curve shown in Fig. 3,

A function f _D (X) that finds X → D, and becomes its inverse

The function f _X (D) to find D → X is shown.

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 curves of the color document with the reference density characteristic curves, the following procedure can be used (see FIG. 3).

(Iii) From the density values of the 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, define the individual density characteristic curve of the color original image; Ii) Substituting the density values D _Hn to D _Sn of the color originals into X = f _X (D), the range of the color original image on the X axis, X _Hn to X _Sn is obtained, and (i) the density based on this. Match the characteristic curve on the X-axis, X _Ho to X _So. (Iii) Next, find the D-axis range, D _Ho to D _So of the reference concentration characteristic curve.

It goes without saying that, if the individual density characteristic curve of the color document coincides with the reference density characteristic curve, the matching of both is unnecessary. In addition, an arbitrary allowable range is defined in the reference concentration characteristic curve, and when it is within the allowable range, the image processing can be performed to be regarded as the same as the reference concentration characteristic curve.

In the matching procedure of the individual and reference density characteristic curves described above, it is normal that XR (exposure range of standard documents) and XRn (exposure range of non-standard color documents) match with XRn to XRo. (See the order of (ii) and (iii) above.) To match XRn to XRo, simple matching (an attitude that matches the minimum concentration value to the same value and matches the darkest portion). And proportional matching (an attitude that matches both the peak and dark concentrations). In FIG. 3, the proportional matching was performed mathematically.

As shown in FIG. 3, XRn is obtained by substituting the concentration information value of the individual concentration characteristic curve (density information value between D _Hn and D _Sn , Dn) into the basic concentration characteristic curve D = f _D (X). The density information value (Density information value between D _Hn and D _Sn , Do) between color originals adjusted by X adjusted to XRo is obtained, but the X value after adjusting X _R n to XRo is obtained. The relational expression to be obtained is as follows by simple calculation.

(1) In case of simple matching

X = f _X (Dn) ± | m |

(2) In case of proportional matching

X = f _X (D _Ho ) + [{f _X (Dn) ± | m |} -f _X (D _Ho )] ×

only,

m: Parallel travel required

XRo: Exposure range of the standard density characteristic curve of the standard document on the X axis.

XRn: Exposure range of individual density characteristics of nonstandard individual originals on the X-axis.

Color film originals of standard quality (D _Ho = 0.20, D _So = 2.80), those of high key (exposure over) (D _Hn = 0.10, D _Sn = 2.70), and those of low key (exposure under) Using D _Hn = 0.60 and D _Sn = 3.20), the matching data when the individual concentration characteristic curve is matched to the reference concentration characteristic curve is shown in Table 4 below under the basic concentration characteristic curve shown in Table 3.

[Table 4]

Matching Data of 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 one was simple matching and the other was proportional matching.

In the concentration values of D _n and D _{o in} the above Table 4, y values (pixel concentration values,%) were obtained by the relational formula (1) based on D _o . The results are shown in Table 5. 4 shows correlations between y values and D _n values in the fifth table. The curve shown in FIG. 4 is a manufacturing characteristic curve that defines the correlation between the x value and the y value that can produce a recording image having excellent reproducibility of manufacture from an original image of non-standard image quality.

[Table 5]

(Gradation Characteristic Setting Data)

Integer of [Expression (1)]: α = 1.00, γ = 0.90, y _H = 5%, y _S = 95%

In order to operate (fixed) the γ value of [Relational Expression (1)] in the gray scale adjustment mechanism of the thermal printer, the radix (concentration over H, S, and H to S for measuring the density of the original image in the thermal printer) Measurement), software or hard to match the individual density characteristic curve of the original image to the standard concentration characteristic curve, but this makes it possible to produce a recording image excellent in gradation and color tone from an original of any quality content. .

(3) About Thermal Printer

The thermal printer of the present invention will be described based on FIGS. 5 to 7.

5 is a block diagram of the thermal printer of the first embodiment of the present invention. As shown in FIG. 5 (a), the thermal printer of the present invention includes a detection section 1 that spectroscopically reads the transmitted or reflected light of an original image into R (rad), G (green), and B (blue); Color separation using the color separation unit 2 for converting the output signal of the detection unit 1 into the color separation signals of Y (yellow), M (magenta), C (cyan), and K (black) and the above-described [Relational Expression (1)] The heating calorific value of the thermal stylus (head) of the printer is converted based on the gradation adjustment mechanism 3 for processing a signal to form an appropriate gradation image, and the output signal of the gradation adjustment mechanism 3, thereby transferring ink to the recording paper. It is composed of four blocks with the output unit 4.

The detector 1 detects transmitted light or reflected light of each part of the original 5, such as a photomultiplier tube or a solid state image pickup device (CCD), and outputs R, G, B, and USM signals as current values, and outputs the signals as A / V. The change section 6 converts the voltage signal.

The color separation unit 2 converts the voltage signals of each of R, G, B, and USM signals of the detection unit 1 into a concentration in a logarithmic amplifier 7 and converts them into a concentration in the base masking (BM) 8 from the black (K). ), And then separate each component of Y, M, and C. Next, the color correction (CC) section 9 controls the Y component, the M component, and the C component for each of the original colors of R, G, B, and Y, M, and C. Then, the black component of the original is converted into the UCR / UCA section. In 10 UCR (under color removal) or UCA (under color addition), the ratio represented by three types of ink of Y, M, and C, and the ratio represented by K (black ink) are determined. After these Y, M, C, and K components are obtained, the pixel concentration values in the pixel blocks of the respective color components from Y, M, C, and K in the gradation adjusting section 11, that is, ye ', me', which represent the effective area ratios of the respective color components, The conversion is performed to ce 'and ke'. The gradation adjusting unit 11 has the algorithm of [Relational Expression (1)] inside, and applies the [Relational Expression (1)] to each of Y, M, C, and K to obtain the electric ye ', me', ce ', and ke'. .

As a gradation adjusting section 11, a general-purpose computer which holds the algorithm of [Relational Expression (1)] as software and has A / D and I / F (interface) of D / A, and is implemented by a general-purpose IC using the algorithm as logic. It can take various forms such as circuits, electrical circuits including ROMs that hold the computational results of algorithms, PALs implemented with algorithms internally, gate arrays, custom ICs, and so on.

The effective area corresponding to the color density information of each life component obtained by the gradation adjusting section 11 is input to the color channel selector 12, and the color channel selector 12 outputs ye ', me', ce ', and ke'. This output is subjected to A / D conversion by the A / D conversion unit 13 and input to the output unit 4. In output unit 4, a pulse signal corresponding to the image information signal from dot control unit 14 is applied to thermal head 16 by known thermal printing means, and recording is performed on recording paper 17. In addition, in the present Example, the color ink film 18 is used, as shown to the same figure (b).

6 is a block diagram of a thermal printer of a second embodiment of the present invention. In Fig. 6, a TV signal is used as the image information signal of the original image. The Y, M, C, and K component signals of the TV signal are input to the gradation adjusting unit 11 having the algorithm of [Relational Expression (1)], and the digital signal is converted by the A / D converter 21 through the color channel selector 12. The digital signal is sent to a data storage device 22 such as a semiconductor memory, and the address is determined and stored as many pixels as necessary, and StarArt Pulse is applied to the address counter 24, and the reference clock is sent to the address counter 24. The first address is sent to the data storage device 22, and the data contained in the address is returned from the data storage device 22, and this data is sent to the data comparison unit 25 to the joke data comparison unit. At this time, the count of the data counter 26 is set to 0, and the data returned from the data storage device 26 is compared with the data (count 0) from the data counter 26 by the joke data comparison unit 25, so that the data from the data storage device 22 is compared. A signal of 1 is sent to the shift register circuit 27 if it is equal to or larger than data (count 0) from the data counter 26, and 0 is sent to the shift register circuit 27 if it is small. Thus, the heat generating resistors R ₁ , R ₂ ,... Of the thermal head for 24 hours in the address counter. When the total number n of R _n is counted, one data transmission pulse is sent to the latch circuit 28. Also, when the first data pulse is sent, the heating pulses are simultaneously gated G ₁ , G ₂ ,. Send it to G _n .

After that, each time the counter counter 24 finishes n counts, the count of data counter 26 is increased by one. If the maximum color concentration is m, n of the address counter 24 is counted m times. The data of each address returned from the data storage unit 22 and the data returned from the data storage unit 22 are compared each time in the joke data comparison unit 25, and if the data from the data storage unit 22 is greater than or equal to the number of counts from the data counter 26, the shift register circuit 27 Send one signal, 0 if not. Then, the address counter 24 is a heat transfer antibody R ₁ , R ₂ ,. When the total number n of R _n is completed, one data transfer pulse is sent to the latch circuit 28, and at the same time, the heating pass is connected to the gates G ₁ , G ₂ ,. Send it to G _n .

Thus, the heat generating resistors R ₁ , R ₂ ,. A predetermined time current flows in R _n between the heated thermal head 4 and the pressure roller 3 in close contact with the heat-melting ink 2 'of the transfer 2 and is sent at a speed V in the direction of the arrow of the recording paper 1. If the time required for the count of n in the address counter 24 is t, the dot of mvt length is transferred in the part corresponding to the maximum color concentration, and the dot of vt length in the part corresponding to the minimum color concentration. Transfer is carried out, and dots of integral length of vt are transferred in accordance with respective color concentrations, so that a recording image having a changed color density per unit area such as the same degree (b) (size modulation method) can be produced.

7 is a block diagram of a thermal printer of a third embodiment of the present invention. 15 ₁ to 15 ₃ are dot pattern generators and 16 are buffer memories. This example is a dot pattern method in which MxN dots correspond to one pixel, and a medium tone reproduction method (density modulation method) generally called. The dot pattern generators 15 ₁ to 15 ₃ select and output the pattern of dots including the number of " 1 " corresponding to the level in response to the density level of each primary color adjusted by [Relational Expression (1)]. In addition, the buffer memory 16 is a buffer for absorbing the difference in speed generated due to the correspondence of MxN dots to one pixel, that is, the difference between the writing speed of a dot and the input speed of an image information signal.

Moreover, the example of the dot pattern in the case where M = N = 4 is shown in the same figure (b).

(4) Usefulness of [Relational Expression (1)] Next, the usefulness of [Relational expression (1)] applied to the manufacturing adjustment mechanism of the thermal printer of the present invention will be supplementally explained.

This is a supplementary description to help the understanding of the present invention, and will be described in detail mainly on the operation of [Relational Expression (1)] applied to the gray scale adjustment mechanism of the thermal printer and its significance.

(A) Operation experiment of [Relationship (1)]

As the basic experiment for incorporating [Relational Expression (1)] into the tone adjustment mechanism, the following two experiments were performed.

a) First of all, a conventional simple calculator, namely, the product of Shaaff Pidagolas EL 5094A (manufactured by Shaaf), is operated by fitting the desired value to [Relational Expression (1)] while operating the simple calculator. The gradation adjustment table of the images shown in 6 tables (1) (2) (3), 7th table, and 8th table 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 a simple personal computer (PC-9801-M2 manufactured by NEC Corporation) is input as function data, and the basic density value (x) of the original image (continuous gradation image) is the density value of the pixel of the recording image corresponding thereto. The operation to adjust to (y) was performed.

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

In addition, in this experiment, no special software was required to create the above software for use in the gradation adjustment of the image input to the personal computer. As a result of the creation work using the N88-BASIC included with the personal computer, It only took one hour to complete.

In addition, by the software which can input the density value by the density meter from the highlight (H) to the shadow (S) of the original image instead of the basic density value of the original image, the manufacture and conversion of the manufacture of the target image can be performed. It was confirmed that there was.

Using these software, a desired density interval (-0.05 for 0.00 to 1.00 and 0.10 for 1.00 to 3.000) is set in the original image, and the value is transferred to the personal computer. By the input command, the target image density value y was obtained.

In addition, by inputting a plurality of density values ranging from highlights to shadows of the original image, a desired pixel concentration value y corresponding to them could be obtained.

The pixel concentration value y by the software described above can be output to either a positive image or a negative image alone or simultaneously.

(B) The calculation results obtained from [Relational Expression (1)] and their usefulness will be described below for the usefulness of the sixth tables (1), (2), (3), 7th, and 8th tables.

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

In Table 6, when a monochrome image is formed from an original image by an image forming apparatus such as a dust mill printer, the density of the ink material (in the table, the density range of the recording image is expressed, which is the γ value of [Equation (1)]). ) And when the range of use of the maximal subconcentration changes (in the table, three cases of 0-100%, 0-98% and 0-95% are shown). The table shows how image density values y at points should be set.

Also, even if the concentration of the ink material in this table is the same (that is, even if the recording image concentration range of the leftmost column in the first table is equal to γ), how does the ideal gray scale characteristic curve change when the use range of the maximum small concentration value is changed? It can be seen whether or not it should be changed.

In Table 6, the β value for determining the ε value is determined as β = 10 ^−γ . Incidentally, when the recording image concentration range = gamma value = 1.0, epsilon = 1 / (1-β) = 1.1111. Note that the pixel concentration value (%) and the value coincident with each other are the theoretical values when β = 0.

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

[Table 7]

Similarly to Table 6, when the density of the forming material (ink, pigment) of the image is changed (i.e., the recorded image concentration range =? Value) when forming the monochrome image from the original image, While using the maximum concentration level in the range of 0% to 100%, the contrast of the whole image is separated, and each sample point necessary for forming an image having the same image quality and the same image quality with respect to the human visual sense is provided. The pixel concentration value y in the table is a list.

In other words, when the conditions are ideal, the pixel concentration values y of the respective sample points on the ideal gradation characteristic curve corresponding to the density values of the forming materials (inks and colors) of the image to be used are listed.

[Table 8]

In Table 8, the basic conditions are the same as in Table 7, but when the range of maximum concentration is used (5% to 95%), the pixel concentration value (y) of several% is obtained for each sample point on the ideal gray scale characteristic curve. It indicates whether or not to set.

Until now, color separation work in printing images, etc. is regarded as the primary goal of color correction by masking technology, and manipulation of the gradation of the image is basically only human experience and feeling, or In other words, they only relied on a limited number of fixed conditions. For this reason, it is necessary to scientifically convert the gradation when creating a duplicate image based on the side of the image to be copied, such as a print image or a recorded image by a printer.

[Equation (1)] of the present invention is to perform gradation conversion in creating a duplicate image in a reasonable manner. In addition, the data of Tables 6 to 8, which show the correlation between the basic density value of the original image obtained and the pixel concentration value of the image formed by [Relational Expression (1)], are basic in color separation operations during image formation. It is a useful basis for scientific review of various matters.

From these tables, it is possible to extract what the essence or principle exists between the original image and the color separation work, and what must be paid attention to and consideration for rational matching of the essence, principle and practice. .

(C) Regarding the application as the correction (or change) of the manufacture of the relational expression (1), the relational expression (1) is based on the conversion of the gradation of the image (that is, the distribution of pixels of high fidelity from the original image of the continuous gradation). In addition to the conversion to a gradation image, the so-called gradation (or change) of the original image itself is effective. The correction (or change) of the manufacture of this image includes the change of the reduction / enlargement ratio of the recording image to be formed, the intention of the orderer, the type of the target image in the color document, the purpose of using the image to be formed, the whiteness of the recording paper and the image. In some cases, the concentration of the recording material (ink, pigment), etc., must be performed, but in any case, it is possible to reasonably cope with the operation of the relation (1) and to standardize and standardize various color separation operations. .

In addition, according to the present invention, the gray scale correction (or change) of the image of the highlight portion or the shadow portion can be performed in the same manner. This is evident from the fact that, as shown in Fig. 1, 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? Value to be employed. Further, it was confirmed by the gradation conversion according to [Equation (1)] of the present invention that the color flow (Fog) in the highlight portion of the color document is automatically removed without taking special countermeasures.

[Table 6]

Relationship between Record Image Concentration Value (γ Value), Maximal Small Concentration Value Use Range and Pixel Concentration Value (Theoretical Value)

Calculation: y = y _H + ε (1-10 ^- _kx ), X: base concentration,

α = 100%

y ₁₁ to y _S = 0 to 100%, 0 to 98%, 0 to 95%, Y: pixel concentration (%) (theoretical value)

ε = 1 / (1-β)

[Table 7]

의 점을 선정)Relationship between the recorded image concentration range (γ value) and pixel concentration value (y)

Select points)

Range of pixel concentration used: 0% ~ 100% (Unit: percentage)

[Table 8]

의 점을 선정)Relationship between the recorded image concentration range (γ value) and pixel concentration value (y)

Select points)

Range of pixel concentration used: 5% ~ 95% (Unit: percentage)

[Effects of the Invention]

This invention has the following outstanding effects.

1) In determining the correlation between the density value of an original image such as a continuous gradation image, which is the most basic matter for image formation, and the pixel concentration value of a recording image (image recorded by the distribution of pixels), Was based on irrational methods that were based solely on the experience and feeling of the worker or on a limited number of fixed conditions. In the present invention, on the other hand, under any circumstances, this can be reasonably determined based on [Relational Expression (1)]. When converting an original image such as a continuous gradation image to a recording image by distribution of pixels, the management of gradation (conversion, correction or change of gradation), which is the most important requirement, does not simply remain in the gradation of the image. Therefore, since the present invention has a direct relationship with the color tone of the image, the present invention can reasonably manage the production and color tone.

That is, the thermal printer 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. Is extremely large.

2) By inserting the algorithm of [Relational Expression (1)] into the tone adjusting mechanism of the thermal printer, the printer device can be rationalized and simplified, and manufacturing cost can be reduced. In addition, the operation can be simplified and clarified, and the work can be significantly reduced, the consumption of consumable materials can be greatly reduced, and the performance of the thermal printer can be greatly improved. In particular, in the performance of a thermal printer, there is a great positive effect that a recording image excellent in gradation and color tone can be formed even if the quality of an original image is anything.

3) The gradation adjustment mechanism incorporating the algorithm of [Relational Expression (1)] can separate the image information from the original image and provide a reasonable and simple evaluation criteria for the quality of the recorded image by the distribution of pixels. Therefore, it is possible to reasonably respond to the diversified needs of customers.

4) By adopting [Relational Expression (1)], the training of technicians required by the advancement of printer equipment can be effectively carried out through the operation of [Relational Expression (1)], and at the same time, it is useless in insolation work. By eliminating effort, you can free up time for new creative development.

Claims (6)

The detection unit that spectroscopically reads the transmitted and reflected light of the original image into red (R), green (G), and blue (B), and outputs signals from the detection unit to yellow (Y), magenta (M), and cyan (C). ), Based on the color separation unit for converting to a black (K) color separation signal, and a gradation adjustment mechanism for processing to form an appropriate gradation image from the chrominance signal and the output signal of the gradation adjustment mechanism. A thermal printer, comprising: an output unit for forming a recording image having a halftone of one color or a plurality of colors on a recording paper, wherein the gradation adjustment unit of the gradation adjustment mechanism is used for an original image based on an image information signal. The base concentration value X of the arbitrary sample point of the sample (difference from the density value in the sharpest part of the density image in the sample point) at the position corresponding to the electric sample point of the recording image to be formed. Get the pixel concentration values (y), the more eomeol printer characterized in that the conversion treatment by [Expression 1] below. [Relationship]

X: Basic concentration value of arbitrary sample point X in the original image. Namely, the density value obtained by subtracting the concentration value at the outermost part H of the moving image from the concentration value at any sample point X of the moving image. Y: pixel concentration value of position Y corresponding to electricity X in the recording image to be formed, Y _H : pixel concentration value of a desired size set for the pixel of the sharpest portion H of the recording image to be formed. Y _S : pixel concentration value of a desired size set for the pixel of the darkest part S of the recording image to be formed. α: reflectance of the recording paper. Formula obtained by β: β = 10 ^-γ . A formula obtained by k: γ / (concentration range of the original image). γ: represents an arbitrary coefficient, respectively. The thermal printer according to claim 1, wherein the recording image having the halftone is a modulated image having a dot density formed by a Dier Matrix. The thermal printer according to claim 1, wherein the recording image having the halftone is a dot size modulation image formed by converting a recording dot diameter. The thermal printer according to claim 1, wherein the recording image having the intermediate tone is formed by changing the concentration of the recording dot itself. The thermal printer according to any one of claims 1 to 4, wherein the multicolor recording image is obtained by a plurality of print heads and a plurality of print heads corresponding thereto. The thermal printer according to any one of claims 1 to 4, wherein the multicolored recording image is obtained by an ink film arranged with a single printhead and multicolored repeatedly.

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