JPH11164167A - Digital data preparation method for halftone image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for obtaining accurate, high resolution digital data capable of describing reflection prints of halftone images of material constitution like normal photographs and printings. SOLUTION: A method of recording images by transferring a color material from the outside of an image supporting body is utilized, and distribution of color materials for constituting reflection prints is accurately reproduced on a transmission type supporting body. Reflection prints are converted into high resolution digital data by reading a transmission type image, correspondence of a calorimetric value indicated by the quantitative combination of optional color materials on the respective supporting bodies is separately obtained and calorimetric value of the transmission type image is converted to one of the reflection prints based on the correspondence chart. By such work of two stages, the reflection prints are concerted into high resolution accurate digital data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for obtaining accurate and high-definition image data of a reflection print image, and more particularly, to a method for producing a standard image or a test chart image.

[0002]

2. Description of the Related Art When a reflection print image exists, it has been extremely difficult to obtain accurate image data. Conventionally, a reflection print has been directly scanned and read by a scanner or a microdensitometer. In that case, in order to obtain sufficiently high-resolution data, it is necessary to reduce the aperture for scanning and reading. However, in the case of reflection printing, since only a small part of the light illuminating the sample enters the light receiving element, the signal to noise ratio (Signalto Noise Ratio,
In order to keep the SNR high, strong illumination is required. Then, the reflective support easily expands and contracts due to the influence of heat, and the positional accuracy of data relating to a plurality of color components is disturbed. In an extreme case, the dye image itself is deteriorated by measurement.

When the aperture is enlarged, spatial accuracy is not obtained, and only low-resolution data can be obtained. One solution is
Scanning is to make the image to be read much larger than the final image and scan with a large aperture,
Such is likely to be impractical, since reflective prints use a relatively large size as a standard.

[0004] Due to such inherent difficulties, for example, when determining a standard image to be a reference for research such as image compression, conventionally, a transmissive image (a transparent positive image by silver halide photography) is used for a manuscript, and this is used. Scanned data was used. In this case, there was no model of the most preferable reflection print based on this data, and it was impossible to show an ideal conversion result in the form of the reflection print. For example, SCID, which has already become an international standard
(Standard Color Image Dat
Both a) and the more recently developed SHIPP consist of data obtained by reading color transparencies and do not have a corresponding reflection print.

[0005] As a reference material, a 175 line lithographic print obtained under standard plate making and printing conditions was prepared as a reference material, but complicated signal processing was applied to the original data until a reflection print was obtained. Since the contents are not disclosed to the outside, there is no simple relationship / correspondence between the reflection print and the image data.

One simple method of obtaining a reflection print having reliable image data is to form an image once on a transparent support, measure the image data, and then appropriately process the support to obtain a reflective print. It is converted into gender. In this case, it is necessary to read the image again after the reflection type and to suppress how the transmission type data is converted to the most preferable reflection print. A specific method of processing the support is to apply a light-scattering layer to the back surface of the transparent support and to attach or apply a light-scattering material to the image surface of the support.

[0007]

However, the reflection print obtained in this way has a unique cross-sectional structure that inevitably produces such operations, and its appearance is the same as that of ordinary printed materials or digital prints. Gives a completely different appearance or texture from the print. Such a difference in texture usually has a strong influence on the image quality evaluation of the observer. For example, in the above case, the optical dot gain is increased due to the light scattering layer through the relatively thick transparent layer below the image. In the case of, since the transparent layer is thickly overlaid on the image, a part of the light incident on the print depends on the refractive index of the material composing the transparent layer and repeats multiple reflections in the horizontal direction. Becomes a slightly darker image. Of course, it will look quite different from a normal print.

[0008] It has been found that the psychology of a human who observes a hard copy is complicated, and the physical composition of an image has a strong influence on image evaluation. Therefore, it is desirable that the structure of the standard image (especially the cross section) is equal to or sufficiently similar to that of the general image.

In summary, the problem to be solved is to obtain, at a high resolution, digital image data constituting a reflection print having no specific sectional configuration.

[Means for Solving the Problems]

As a result of extensive studies of the method for solving the above-mentioned problems, the present inventor has found that the distribution of an image forming material (hereinafter, referred to as a coloring material) constituting a preferable reflection print can be realized on a transmission type support as it is. Noticed. In other words, if the transmitted image is measured with a fine aperture using a microdensitometer or the like, and if the digital data is accurate, spatial resolution can be guaranteed, while the color characteristics at each point will be a certain color material. If you measure with a patch etc. how the quantitative combination changes in reflection and transmission, you can take a correspondence between the two,
Eventually, based on the data obtained by measuring the transmission image, preferable image data at each point of the reflection print can be accurately obtained.

That is, the present invention uses a recording material or a recording method capable of discharging an image forming material to an image receiving member in an image form in response to a signal, and forms an image based on digital data on an image receiving member having a reflective support. By using an image receiving body formed by using the same data and using the same data and under the same recording conditions, only the support is changed to a light transmitting type, a transmission type image composed of the same image forming material as the image of the transmission type image is formed. , And the resulting transmission image is scanned and read by a scanner, microdensitometer, etc.
Separately, a quantitative combination of an imaging material determines the correspondence between the reflective and transmissive color characteristics used, and measures the data for a sufficient number of combinations to obtain the corresponding data. Is a method for creating digital data of a halftone image in the form of a reflective print with high accuracy, by converting the value into a value on a reflective support on the basis of.

The recording method that can be used in the present invention may be any method that includes a process of moving an image forming material constituting an image, that is, ink, toner, dye itself, etc., to a support. Such examples include dye-transfer silver salt photography, dye-transfer thermal recording, ink-jet recording, and melt-transfer thermal recording. Of these, the first two can form a density-modulated image, while the later ones can only form an area-modulated image because the number of recording density levels is limited. As a reference image for the purpose of research or the like, an image of a density modulation type is more preferable, and therefore, also in the present invention, the first two recording methods are particularly preferable.

Dye-transfer-type silver halide photographs include a type in which a viscous developer currently marketed as an instant color photograph is developed between a photosensitive sheet and an image receiving sheet, and a developing component is included in the two sheets. In addition, there is a heat development type in which a small amount of water is used instead of a viscous developer while heating the system to a high temperature. The latter is commercially available under the trade name Pictography, but has a feature that the developing characteristics are very stable because the developing components are always supplied in a fresh state. In order to carry out the present invention, it is necessary to make two reflection prints and two transmission images. At that time, it is required that the developing characteristics do not fluctuate as much as possible and exhibit stable reproducibility. Therefore, among dye thermal transfer type silver halide photographs, a system in which a developing component is incorporated in a sheet can be said to be the most suitable for the present invention among practical recording systems.

When the dye thermal transfer type silver salt photographic method is used in the present invention, it is necessary to pay attention to the following points. That is, since the state of transmission of heat applied in the development and transfer process is slightly changed depending on the support of the image receiving material, an image receiving material having the same recording characteristics is prepared in advance, or processing conditions for compensating for the change are used. Need to be sought. As processing conditions, the development temperature and the development time are important, but the characteristics of the developing components and the area density of the two materials are also important. With all these constant, an experiment was performed with only the support changed, and the amount of dye transferred to the image receiving material was extracted and quantified with a solvent, etc., to confirm whether the same amount as that on the reflective support was actually transferred. Try. If a quantitative change is found, it is necessary to determine the conditions for forming a transmission image so that the transfer amount is the same by changing the factor which is most easily and easily controlled. One way is to change the development time.

Next to this is dye transfer thermal recording. The principle is simple, and the reproducibility and stability of recording are already sufficiently good due to advances in thermal control of the recording head. As above, if you take into account the differences between the supports,
No problem at all. However, the stability of the image itself is preferably subjected to a special treatment. Specifically, it is preferable to use a post-chelate type image receiving material or to provide an ultraviolet absorbing protective layer on the surface.

Although a recording method such as fusion transfer thermal, dry or wet electrophotography, and ink jet can be used in the present invention, it is somewhat less general as a standard image. Of the area-modulated images, printing is most desirable, but the preparation process is complicated and long, and careful attention is required to ensure reproducibility.

Since it is necessary to obtain digital data for the support of the reflective print, which is a starting point, it is easier to handle the measurement results by using a support that does not contain a fluorescent whitening agent.

As a precautionary measure, another method is described which could more easily achieve the objects of the present invention. That is, the same light-sensitive silver halide emulsion layer is provided on a reflective support and a transparent support, and the same exposure is applied to achieve the same color material distribution.

Although such a method seems to be preferable at first glance, in order to make the behavior of light upon exposure exactly the same on the two supports, the light absorbing layer which eliminates the difference between the supports is exposed to light. It must be provided between the layer and the support, which must of course be colorless by treatment. In practice, taking such measures has a complex effect on the properties of the emulsion, and as a result it is difficult to guarantee that the distribution of the resulting colorants is exactly the same. From this, the superiority of the transfer recording method as in the present invention emerges.

The following description relates to a heat-developing dye-transfer silver salt photographic method in which the present inventors have actually conducted experiments.

A reflective image-receiving sheet containing no fluorescent whitening agent, which was specially prepared using a commercially available Pictography 3000 (manufactured by Fuji Photo Film Co., Ltd.) in cooperation with Ashigara Laboratory of Fuji Photo Film Co., Ltd. Using a transmissive image receiving sheet that exhibits exactly the same image receiving characteristics as this reflective image receiving sheet,
Patches of three primary colors of CMY were output, and the density of each patch was measured depending on the support.

It should be noted that, with the commercially available Pictography 3000, when a roll of OHP film is loaded, it is automatically detected as a film and the development conditions are changed. For the current purpose, this is unpleasant, so we process the magazine that contains the film,
It is necessary to disable this automatic detection mechanism.

As a result of such considerations, it was confirmed that the concentrations of the same amount of dye on the two supports satisfy the following relationship. _{D R -D RO = K (D} T -D TO) m (1) where, _{D R:} Concentration D _RO on a reflective support: background density on a reflective support D _T: transparent support Density on the body D _TO : background density on the permeable support, K is 2.1 to 2.4, m is 0.72 to 0.
It is a constant of about 75.

The relationship between the two images can be quantified based on such data. However, as digital data, device-independent values such as Lab or XYZ are used.
It is better to describe the characteristics of each point in the image, for example. In particular, when two or more dyes are superimposed, the density initially determined is the integrated density, and further calculation is required to obtain the analysis density. A practical approach is to use L and L on the reflective and transmissive supports for a sufficiently large number of dye combinations.
^Find the relationship between the ^* a ^* b values and find the three-dimensional Look-Up
A table (LUT) is created, and values between the tables are obtained by interpolation. The method of interpolation is cube interpolation,
Many such methods as prism interpolation, pyramid interpolation, and tetrahedron interpolation have already been developed, and any one of them may be used.

The color space of L ^* a ^* b is originally defined as follows for a reflective object. _{^{L * = 116 (Y / Y}} n) 1/3 -16 (2) a * = 500 {(X / X n) 1/3 - (Y / Y n) 1/3} (3) b * = 200 {(Y / Y _n ) ^1/3 − (Z / Z _n ) ^1/3 } (4) where XY and Z are tristimulus values of the target reflective object,
X _{n, Y n, Z n} are tristimulus values of a perfect reflecting diffuser,
Normalize to Y _n = 100. Where the above series of equations is X
_{/ X n> 0.008856, Y /} Y n> 0.0088
56, Z / Z _n > 0.008856. If the value is outside this range, the following equation is used. _{^{L * = 116f (Y / Y}} n) -16 (5) a * = 500 {f (X / X n) -f (Y / Y n)} (6) b * = 200 {f (Y / Y n ) −f (Z / Z _n )｝ (7) where f (X / X _n ) = 7.787 (X / X _n ) +16/116 X / X _n ≦ 0.008856 (8) f (Y / Y _n ) and f (Z / Z _n ) have exactly the same form as in equation (8).

As can be seen from the above description, L ^* a ^* b
Does not adapt to the description of transmissive images. However, in this case, L ^* a ^* b of the transmission type image is tentatively promised in the following manner so as to obtain the correspondence with the colorimetric values of the reflection print.

The transmitted image is illuminated with a light source having the same constant color temperature as that of the reflected image, and transmitted through an image area showing so-called _Dmin (the lowest density in the print). By assuming that the XYZ values calculated based on the light entering the photometric system correspond to the tristimulus values (or light source colors) of the perfect diffuse reflection surface, the _Xnt Y of the transmitted image is obtained.
_nt Z _nt is obtained, and the value of L ^* a ^* b is calculated using the same equation as above.

As long as a correspondence between the two values obtained in this way is obtained, all the advantages of the present invention can be realized. The above calculation is complicated, but once obtained, the accuracy of the digital data is guaranteed, and if a reflection print is actually created based on the data obtained in that way, the reflection print that is equal to the original document that was started can get.

The characteristics of the reflection print are affected by the whiteness of the support itself. It is not practical to look for a support that we consider the norm, for example, a support having exactly the same optical properties as the support of a pictographic print. Therefore, in the description of the characteristics of the reflection print, a relative L ^* _rel a ^* _rel b ^* _rel as defined below using D _min of the reflection print as the coordinate origin can also be used.

Normal XY of D _min area of reflection print
When the Z represents an _{X p Y} p _Z p, it is used in place of _X n _Y n _{Z n} of within formula to these values (2) below (8). Such an operation, in other words, the L ^* _rel a ^* _rel b ^* _rel value at D _{min of} the reflection print (often equal to the whiteness of the paper itself) is (10
(0, 0, 0) is equivalent to using a color system.

Thus, when an image is obtained on a support having different whiteness, L ^* _rel a ^* _rel b ^* _rel
It is often practically convenient because it is only necessary to match the values. Recently, it has been debated whether to use black paper or blank paper for the backing of the support as a characteristic measurement condition of reflection print, but if the relative value as defined above is used, The effect of the difference can be almost completely absorbed.

The image data thus obtained is recorded on an arbitrary recording medium in a format suitable for the purpose and distributed.

[0033]

The present invention will be described more specifically with reference to the following examples.

Using a standard donor film of Pictography 3000 manufactured by Fuji Photo Film Co., Ltd. and a standard image receiving sheet without a fluorescent whitening agent, the test chart No. Transparent positive 5 inch x 7 inch size original film of the standard image included in 5.2 (Film used: Fuji Photo Film's Provia. The pattern is a model woman and Macbeth color checker in the center, flowers and fruits around it 12-bit digital data obtained by reading a wine bottle, a metal product, etc.) with a plate-making scanner (25 μm opening) and subjecting it to appropriate image processing to produce an A4 size visually preferable reflection print It was created. This image is called a standard reflection image.

Separately, RG to pictography donor
Create a combination 928 of B signal amounts, each 10mm
The color patches of the mouth size were output under the same development and transfer conditions on the image receiving paper used for the preparation of the standard reflection image and on the transmission type image receiving sheet showing exactly the same image receiving characteristics. Here, "showing exactly the same image receiving characteristics" means that the amount of dye transferred to a certain input signal is exactly the same. The transmission image obtained in this manner is a weak image having no power, such that the density of each point is reduced to about half that of the reflection image.

The fact that the dye amounts were equal was confirmed by extracting the dye contained in a uniform density region of a fixed area with a solvent and comparing the spectral densities near the absorption peak.

Table 1 shows L ^* a ^* b ^* data relating to the step wedges of CMY and RGB among the results. The measurement was performed using a color analyzer TC-18 manufactured by Tokyo Denshoku Co., Ltd.
Performed using 00M. The receiving paper for the pictography was relatively thick and was hardly affected by the backing material, but in this case, the black paper was temporarily laid on the back. The light source was D50, and the criterion for transmission image measurement was light transmitted through the lowest density range of the image.

Although Table 1 includes only a very simple case, the color correspondence table for an actual image contains information on 928 kinds of colors which cover the entire reproduction color gamut of the printer almost evenly. Based on these, the color of the transmission image corresponding to the color of the reflection print was determined.

Next, the same image data was output to the transmission type image receiving sheet used for preparing the patch under exactly the same conditions as when the standard reflection image was prepared, and a standard transmission image was obtained. This is also a faint and weak image as a whole.

The colorimetric value of each point of the standard transmission image is converted into a colorimetric value that will be shown on the reflection print by the previously obtained correspondence table and interpolation, and the resolution is 400 dpi and 8-bit image data.

This data was converted to a Victorography 3000
The system was supplied and a comparative reflection print was prepared. The appearance of the image is a faithful reproduction of the standard reflection image created first, and one of the Macbeth color checkers included in the image is included.
The average color difference between the two colors and the various points 20 in the image was 2 or less, and the standard deviation of the color difference was 2 or less.

[0042]

As described above, according to the present invention, since the reflection print is formed by the transfer type recording method, the formation of the transmission type image by the distribution of the same color material is facilitated. Since the pattern image can be read with a fine aperture, it has become possible to obtain accurate and high-resolution digital data. Regarding the color characteristics, a sufficiently large number of combinations of color materials are formed in the form of a patch in the same manner as a reflection print and a transmission image, and a correspondence table between the two is created. It is now possible to determine the colorimetric values of reflection prints. In this way, the effect of obtaining precise digital data of the reflection print of the ordinary material configuration was obtained.

Claims (4)

[Claims] An image is formed on a receiver having a reflective support on the basis of digital data by using a recording material or a recording method capable of discharging the image forming material to the receiver in an image form in response to a signal. Using data, under the same recording conditions, by using an image receiving body in which only the support is changed to a light transmitting type, a transmission type image composed of the same image forming material distribution as the image is formed and obtained. The read transmission image is scanned and read by a scanner, a microdensitometer, etc., and colorimetric values at each point are obtained. Separately, quantitatively different combinations of image forming materials are applied on the reflective and transmissive supports used. The correspondence between the indicated densities (light modulating abilities) is measured for a sufficient number of combinations, and the colorimetric values obtained in the corresponding colorimetric values that would be indicated on the reflective support are obtained in the corresponding table. Halftone image in the form of a reflection print consisting of conversion using High-precision digital data creation method. 2. The method according to claim 1, wherein the recording method is a heat development type dye transfer method using a heat development type silver halide photosensitive material and an image receiving material. 3. The method according to claim 1, wherein the recording method is a heat development type dye transfer method in which a developing component is incorporated in a photosensitive material and an image receiving material. 4. The method according to claim 1, wherein the recording method is a dye transfer thermal recording method.