JP2001036754A - Color converter, printer using the converter and printing system using the printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a color converter capable of minimizing the memory occupation quantity of a color conversion table and quickly executing highly accurate color conversion and a printer using the color converter. SOLUTION: The color converter 30 in the printer 10 has color conversion processing parts 34, 37 provided with color conversion look-up tables having the sizes of respective components Si1, Si2, Si3 of a discrete input chrominance signal as look-up values and having the sizes of respective components So1, So2, So3 of an output chrominance color as conversion values in order to convert an input chrominance signal Si into a corresponding output chrominance signal So. These look-up tables include a 1st color conversion table part 34a in which an interval between adjacent look-up values out of look-up values in a 1st range V1 for at least one component of the input chrominance signal coincides with a reference interval Ds and a 2nd color conversion table 37a having look-up values at an interval Da smaller than the interval Ds in a 2nd range V2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a color conversion device, a printer using the same, and a printing system using the printer.

[0002]

2. Description of the Related Art In order to convert an input color signal consisting of three or four components into a corresponding output color signal, the size of each component of the discrete input color signal is used as a lookup value, and the size of each component of the output color signal is determined. A color conversion table processing unit having a color conversion lookup table having the conversion value as a conversion value, and performing an interpolation operation on each component of the input color signal having an intermediate magnitude between adjacent lookup values in the table. 2. Description of the Related Art A color conversion device including an interpolation operation unit for obtaining an interpolation value of each component of an output color signal is known.

A color reproduction device for displaying and printing a color image or the like has a characteristic that each device has a non-linear color difference response to an input color signal to the device. Various measures have been taken to make this more efficient and more accurate.

[0004]

However, in the conventional countermeasure, the lookup value of the color conversion table indicates that the input color space is equally spaced (for example, divided into eight, sixteen, or thirty-two) in each direction (chromaticity coordinates). Etc.). As a result, in the conventional color conversion apparatus, it is necessary to increase the number of lookup values (the number of divisions or separations of the color space) of the color conversion table in order to increase the accuracy of the color conversion, and the file size of the color conversion table is increased. Or, the occupied memory capacity may increase exponentially. Conversely, if the file capacity or memory occupancy of the color conversion table is reduced, linear interpolation with low accuracy or nonlinear conversion with a long interpolation operation time is required. There was a fear.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to perform high-precision color conversion at high speed while minimizing the file capacity or memory occupancy of a color conversion table. An object of the present invention is to provide a color conversion device which can be performed, a printer using the same, and a printing system using the printer.

[0006]

The color conversion apparatus according to the present invention comprises:
To achieve the above object, the size of each component of the discrete input color signal is used as a lookup value to convert the input color signal into a corresponding output color signal, and the size of each component of the output color signal is used as a conversion value. A color conversion table processing unit having a color conversion look-up table, and an interpolation operation for each component of the input color signal having an intermediate size between adjacent lookup values in the table, and And a color conversion table, wherein at least one component of the input color signal has an interval between adjacent lookup values among lookup values in the first range equal to the reference interval. And a second color conversion table section having lookup values at intervals smaller than the reference interval in the second range.

According to the color conversion apparatus of the present invention, the color conversion table is arranged such that, for at least one component of the input color signal, the interval between adjacent lookup values among the lookup values in the first range matches the reference interval. A first color conversion table portion, and a second color conversion table portion having a lookup value at an interval smaller than the reference interval in the second range. " Interpolation can be performed more accurately. In addition, in the second range, since the interval between the lookup values (discrete values) is small, linear interpolation of a type capable of high-speed processing can be used as the interpolation operation as desired. As a result, highly accurate interpolation can be performed at high speed in the second range. on the other hand,
Since the interval of lookup values is larger in the first range than in the second range and the number of divisions or separations of the input color space is smaller,
It is possible to minimize the file capacity or memory occupancy of the color conversion table. Therefore, overall,
High-speed and high-accuracy color conversion can be performed while minimizing the file capacity or memory occupancy of the color conversion table.

[0008] Each of the input and output color signals, for a conventional color display, is typically a three or four component to represent a color in the corresponding three or four dimensional input and output color space. Become. The input color signal and the output color signal are, for example, RGB color system, CMY color system, XYZ color system, L ^* a ^* b ^* (CIELAB) color system, L ^* u ^* v ^* (C
An IELUV color system and an HLS color system include three types (dimensions) of color signals. For example, a CMYK color system including black or black includes four types (dimensions) of color signals. It may be something. The color system of the input color signal and the color system of the output color signal may be the same or different. In addition,
In some cases, each of the input color signal and the output color signal
Two components or one component may be used.

Each component of the input color signal and the output color signal is typically 1 byte (8 bits), and the gradation along the chromaticity axis is represented. However, the number of gradations is larger. (For example, about 10 to 14 bits) or small, and the number of gradations may be different depending on the components (type of color stimulus) of the input color signal and the output color signal. For example, when providing an output color signal from a color conversion device to a color reproduction device such as a device that reproduces colors in hard copy such as a printer or a device that displays colors on a screen such as a display, the input color When the signal is provided as a standard color signal, the color conversion apparatus typically performs an inverse conversion of the characteristic in consideration of a color reproduction characteristic (unique) unique to the color reproduction device. Will be. Here, the “standard color signal” refers to a signal or data that specifies an intended accurate color in a desired color system.

On the other hand, when an output signal from an input device such as an imaging device such as a digital camera is provided to a color conversion device as an input color signal, the color conversion device typically includes a light source such as a CCD. Inverse conversion of the specific type of digital camera, which depends on the spectral characteristics of the sensor and the like, is performed so as to cancel the characteristic, and a standard color signal is given as an output color signal.

A color conversion table, ie, a color conversion look-up
The color table is composed of the first color conversion table and the second color conversion
A table section. The first color conversion table section is an example
For example, the direction of each chromaticity axis or each component in the input color space
Value to divide the input color space into equal intervals at the reference interval Ds
As a lookup value discretely. The first
The range of lookup values covered by the color conversion table,
The first range typically covers the entire gamut of the input color space.
You. However, the first range is substantially “substantial” of the input color space.
Above "may be the whole range. That is, an input that provides an input color signal
Equipment performance or characteristics, information or data to be entered
The range that the input color signal can take in the input color space is
If you know in advance that they are limited,
The maximum range that the input color signal can actually take in the input color space is
The range of lookup values is limited to
Is also good. In addition, the area defined by the extension of the first range
The area defined by the extension of the second area
Where the first color conversion table section is
Need not have a lookup value except for the boundary of
(The first area may be perforated). Reference interval
Ds is common to each chromaticity axis or direction in the input color space.
That is, the values may be the same or different depending on the axis.
As the reference interval Ds, is it easy to process bits?
And typically 2 ^q(Q is a natural number)
And q is typically 3 to 5.
Used. However, even if q is 6 or more,
In some cases, it may be 2 or less. Also, if desired, color
Each direction of the space may be divided into a number other than a power of two. Minute
Does the number of divisions or decompositions directly affect the size of the table?
Selection according to the dimensions of the input color space and the output color space.
You may choose. For example, if the input color space is J-dimensional and the output color space is
If the space is K-dimensional, the input color space and output color space
As well as 2^qWhen dividing or disassembling
Bull is roughly (2^q+1)^J・ From K data
Will be.

[0012] For example, in the case of J = K = 3, when divided into eight as q = 3 is (2 ³ + 1) ^3.3 = 2187 pieces in, q
= 4 as 16 when splitting is (2 ⁴ + 1) ^3.3 = 14
When 739 pieces and q = 5 are divided into 32, (2 ⁵ +
1) ³ · 3 = 107811, and the interval Ds is １ ／
Each time, the number of data, that is, the file capacity or the memory occupancy increases rapidly. Therefore, q is usually selected to be about 3 to 5, for example, 3 or 4.

The second color conversion table section targets a part of the input color space, not the whole area. That is, the second range is a part of the input color space. However, in some cases, the whole range may be included in at least one direction in the multidimensional input color space. The second range is, for example, a three-dimensional input color space represented by chromaticity coordinates corresponding to three color stimuli or three components R ⁱ , G ⁱ , and B ⁱ of the input color signal S ^ij (j = 3). Among them, [R ^im , R
ⁱ h), (G ⁱ m, G ⁱ h], [B ⁱ m, B ⁱ h] part of the area defined is taken in, in this region, the interval of the lookup value Da is Da = Ds / Taken at d2. here,
[R ^im , R ⁱ h] is the lower limit value R of the second range or area related to the chromaticity coordinates of the input color space related to the input color signal R ^i.
represents the range of from ⁱ m to the upper limit value R ⁱ h, as the first and second color conversion table unit can be combined organically, the lower limit value R ⁱ m and the upper limit value R ⁱ h is first It is included in the lookup value of the color conversion table. The same applies to other chromaticity coordinates. Note that R ^im and R ^ih are respectively
This corresponds to the maximum and minimum lookup values for the corresponding chromaticity coordinates in the second color conversion table. Also, d2 is preferably a power of 2 (d2 = 2 ^t (t is a natural number)) from the viewpoint of easiness of operation. The magnitudes of q and t may differ depending on the direction of the input color space. In the case of the above example, when the three chromaticity axes are expressed as three orthogonal axes, the second range is formed of a rectangular parallelepiped, but the second range is formed by connecting two or more rectangular parallelepipeds. It may have a more complicated shape. In addition, the number of dimensions of the second range or region may be smaller than the number of dimensions of the input color space. However, in any case, the maximum and minimum values of the lookup value of the second color conversion table are
It is preferable to select the range of the second color conversion table so as to match the lookup value of the first color conversion table.

In any case, in the second range, the interval is typically given by the interval Da of 1/2 ^t as compared with the interval Ds of the lookup value in the first range.
In the region [R ^im , R ⁱ h], the response of the output chrominance signal S ^o to the input chrominance signal S ⁱ is extremely complicated and cannot be represented by a simple functional form. Intervals and directions in the output color space according to how two points (positions and directions in the input color space) are obtained by projecting any two points having a certain interval in the second range of the color space onto the output color space. Is greatly changed, the output color signal S ^{o with} respect to the input color signal S ⁱ in the region between the adjacent lookup values.
Since the response of the can so be expressed by monotonous and linear or simple functional form may be derived with high accuracy the output color signal S ^o to the input color signal S ^i. As a result, when the color reproduction system to which an output color signal is to be input is a color region having a unique color reproduction characteristic, for example, the color reproduction characteristic of a device such as a printer depends on the specific characteristic of the color reproduction means. Also, when a specific region shows a peculiar behavior, the specific region is selected as the second range, so that the data amount of the entire color conversion table is not excessively increased, and high accuracy and high accuracy are achieved. Color reproduction can be performed.

The second range described above is not only when the response of the output color signal to the input color signal is complicated and greatly changes, but also in a color region where the gray scale resolution of human vision is high, that is, a human. Or, sensitive visual color areas common to specific races or areas sensitive to color differences, such as "human skin color like skin color", "green" vegetation, or "blue" in the sky Even when it is desired to reproduce or intentionally create a color having a smaller color difference than the other color regions in the color region, the color region may be provided to reduce the color difference in at least one color region. For example, a printer that often prints an image representing a person uses a color conversion table having a look-up table having a “skin color” area as a second range. In some cases, a plurality of types of color conversion tables having different second ranges are stored in an external storage device or the like including a removable medium, and a specific type of color conversion table can be stored as required for the type of image data to be processed. The table may be read into a memory to perform color conversion.

Further, when a color region having a high appearance frequency in the input color signal, for example, an image is composed of a specific type of color,
That is, when handling an image that is biased toward the color of a specific area in the color space, a range corresponding to the color space area in the input color signal may be selected as the second area. . Also in this case, a plurality of types of alternative color conversion tables may be selectively readably stored in an external storage device or the like.

In the above, the second range may be provided at a plurality of locations for at least one type of input color signal.
q and t may be the same or different from each other. In the above, typically, the first range will occupy most of the input color space, but in some cases, the first range may occupy less than half of the input color space. .

In other words, the color conversion table of the present invention has lookup values at different intervals depending on the area of the input color space in order to achieve the above object. Color conversion look-up table. Since the input color space is distorted in terms of color difference and the distribution of input color signals used in the input color space is often biased to some regions, the input color space is divided evenly. Since the color conversion look-up table is wasteful, for example, the input color space is divided so that the spatial region used when the color difference is mapped to a substantially uniform color space is almost uniformly divided. It is good to determine the lookup value to be divided. However, it is preferable to make the look-up value finer as desired in a region having a high gradation resolution peculiar to the characteristics of the color reproduction system and human vision.

The output color signal of the color conversion device as described above is
It may be used for controlling display colors in a display device such as a CRT display or a liquid crystal display, or may be used for controlling color reproduction in a device that provides a hard copy such as a copying machine or a printer. In the present invention, typically, a color conversion device is used for a printer as a color reproduction device. Therefore, in order to achieve the above object, a printer according to the present invention includes the above-described color conversion device, and is configured such that a printing unit is driven by an output color signal from the color conversion device. Of course, if desired, the printing unit may be driven after performing another desired process on the output color signal from the color conversion device.

A printer for reproducing colors is a thermal printer such as a sublimation dye thermal transfer type or a melt thermal transfer type, an ink jet printer, an electrophotographic printer, a photosensitive pressure sensitive type printer. There may be. The printer of the present invention is typically composed of a photosensitive pressure-sensitive printer, and typically constitutes a printing system for printing on media (print paper) coated with photosensitive-pressure-sensitive microcapsules. .

Here, "photosensitive pressure sensitive microcapsule"
Is a microcapsule that is configured to be easily crushed or hardly crushed (ie, a latent image is formed) when receiving light of a specific wavelength range, A substance in which a color-forming substance that enables color development (that is, development) is contained (typically enclosed).

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a preferred embodiment of the present invention will be described with reference to a preferred embodiment shown in the accompanying drawings.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing a printing system having a printer having a color conversion device according to a preferred embodiment of the present invention, a case where interpolation is performed using a color conversion lookup table of the color conversion device will be described. The necessity of making the value intervals uneven will be described with reference to FIG.

In FIG. 3, for simplicity of explanation, the input color
Signal SⁱIs one type and the output color signal S^oIs one type, ie
S^ij, S^OKThe order of the input and output color signals at
j and k are 1, for example, each consisting only of lightness, like black and white
A case of a simple monochrome signal will be described. In the example of FIG.
The power color space is divided or decomposed into eight. Input color signal
SⁱIs the gradation in the range of 0 to 8 in the input color space.
Sⁱ ₀, Sⁱ ₁,. . . , Sⁱ ₈(Input color in input color space
Signal SⁱOf the output color signal S^oBut
Gray scale S in the range from n0 to n8^o ₀, S^o ₁,. . . , S
^o ₈(In the output color space, the output color signal S^oOf possible values
Range), the input color space and the output color space
Input color signal S due to the relative distortion betweenⁱAgainst
Output color signal S^oIs the solid line F in FIG.^ioAs shown in
Will have a response.

In this case, the input color signal S ⁱ is 0 to 1,7
In 8 of the range, since the small and linearity is high variation of the output color signal S ^o, color reproduction of sufficient accuracy to accuracy in the linear interpolation is considered to be expected. When the input color signal S ⁱ is in the range of 3 to 4 and 5 to 6, the output color signal S ^o has a relatively large variation, but its linearity is high. Can be expected. Even if the input color signal S ⁱ is in the range of 2 to 3, it is considered that color reproduction with sufficient accuracy or accuracy can be expected by linear interpolation except for special cases for the same reason.

However, if the input color signal S ⁱ is 1 to
The range of 2,6～7, although the output color signal variation of S ^o is too large is not, due to the low linearity (second order differential values for S ⁱ of the curve F ^io is relatively large), in special cases Except, the accuracy or accuracy of the color reproduction is likely to be low. Therefore, it is desirable to provide a second color conversion table unit having at least one value between 1 and 2 and 6 to 7 as a lookup value. Similarly, when the input color signal S ⁱ is in the range of 4 to 5 and a unique response is generated in the characteristics of the color reproduction system of the printer and a complicated response is generated, simple linear interpolation or function interpolation is used. It is difficult to expect highly accurate or accurate color reproduction. Therefore, in such an area, it is necessary to have a second color conversion table section having a lookup value at a smaller interval by dividing the area more finely.

That is, in this example, the input signal S ⁱ is 0
Range ～1,2～4,5～6,7～8 as first range, for example, enough in the first color conversion lookup table of 8 division, the input signal S ⁱ is 1-2, range of 6-7, as a second range, for example, 16 division or 32 provided a second color transform look up table of the division, the range of the input signal S ⁱ is 4-5, another second As a range, for example, another second color conversion look-up table section of 32 divisions or 64 divisions is provided. Note that an interpolation operation unit that performs a linear interpolation operation may be provided corresponding to each color conversion table unit.

Similarly, as shown in FIG. 4, the input color space is two-dimensional, and the input color signal ^Sij has two types (two components) S
ⁱ¹ and ^Si2 , the output color space is also two-dimensional, and when the output color signal ^Sok is of two types (two components) ^Sol and ^So2 , the entire range of the two-dimensional input color space is defined as the first range. If the sampled input color space is divided into eight in each direction (q = 3, that is, d = 8), the first color conversion look-up table T2
Has eight levels (0 to 8) of the two chromaticity axes of the input color space as lookup values, and the input color signal component has nine levels S ^ij _m (m: 0
(Integer of ８8) are obtained as table data S ^ok _mn . here,
k is a type of chromaticity axis of the output color space according to the kind (component) to the signal of the output color signal S ^o, m a first input color signal S
ⁱ¹ indicates an output when the m-th lookup value of the eight-segment lookup value is taken, and n indicates that the second input color signal S ⁱ² is the n-th lookup value of the eight-segment lookup value. Indicates that this is the output when a lookup value is taken. For example, for the reason described with reference to FIG. 3, the input color space is defined by the range of 3 to 5 in the first chromaticity axis direction and the range of 6 to 7 in the second chromaticity axis direction. second range, i.e., lookup values are desired detailed by when taking a second range defined by the input color signal [S ⁱ¹ _3, S ⁱ¹ _5] and [S ⁱ² _6, S ⁱ² _7] Then, FIG.
As shown in the above, for example, a second color conversion lookup table unit T2a including only a second range or region having a lookup value such that d = 5 (d2 = 2), that is, dividing the whole into 32, is separately provided. Be prepared. Incidentally, the first color conversion table unit T2 is a lookup value S ⁱ¹ ₄ may not have. Further, the second color conversion table unit T2a
, Respectively region [S ⁱ¹ _3, S ⁱ¹ _4] and [S ⁱ² _6, S ⁱ² _7]
If, region [S ⁱ¹ _4, S ⁱ¹ _5] and [S ⁱ² _6, S ⁱ² _7] and may be divided into two tables portions consisting. Further, it is not necessary to physically separate the first table and the second table, and the first and second color conversion table units may be in the form of a single table.

The interpolation may be performed, for example, by performing linear interpolation on each of the two axes S ⁱ¹ and S ⁱ² , or by another method. In this case, as the linear interpolation, four points of a related square may be used, or one of two types of polygonal lines connecting diagonal vertices of the square may be used. In addition, weighting may be performed according to two directions at the time of linear interpolation.

Next, a printer according to a preferred embodiment of the present invention and a photosensitive pressure-sensitive print sheet 1 according to a preferred embodiment to which a color converter for the printer is applied will be described with reference to FIG. In FIG. 6, print paper 1
Is formed by applying photosensitive pressure-sensitive microcapsules. Here, the “photosensitive pressure-sensitive microcapsules” are easily crushed or hardly crushed when light in a specific wavelength range is received (that is, a latent image is formed in the form of regions having different pressure-sensitive characteristics). ) Having a color-forming substance contained therein (typically encapsulated) that allows a specific color to be developed (ie, developed) when crushed. Say. More specifically, as shown in FIG. 6, for example, the print paper 1 is a sheet-like base (base) 2 made of white PET (polyethylene terephthalate).
And an image receiving layer 3 formed on the sheet-like base portion 2 and containing a color developer, and a photosensitive material in which photosensitive pressure-sensitive microcapsules are uniformly dispersed in a binder (adhesive) and uniformly applied on the image receiving layer 3. It comprises a pressure-sensitive microcapsule layer 4 and a protective layer 5 such as transparent PET. Sheet substrate or substrate 2
May be another material such as paper instead of a plastic material. The microcapsule layer 4 does not need to have a binder, and the image receiving layer 3 and the microcapsule layer 4 may be a single mixed layer. The paper 1 having the above-described laminated structure is, for example, about 0.17 mm, typically 0.1 to
It has a thickness of about 0.2 mm.

The photosensitive pressure-sensitive type microcapsule has a transparent outer capsule wall made of gelatin or the like and having a diameter of about several microns, in which a photo-curing substance which is cured by light of a specific wavelength and a curable substance. A color-forming substance that contacts the developer of the image-receiving layer 3 to form a color when the missing capsule is crushed is enclosed. Typically, each microcapsule includes a color-forming substance that develops into one of the three primary colors of the paint when contacted with a developer, and a color that is actually complementary to the color developed by the color-forming substance ( A light-curing substance that cures with light of the three primary colors of light is enclosed together. That is, there are three types of microcapsules, each of which is a type Y microcapsule 4y in which a yellow (Y) coloring material that exhibits yellow and a photocurable material that cures with blue light (B) are enclosed. , A color developing material for magenta (M) exhibiting a red (purplish purple) color and a photo-curing material which selectively absorbs and cures green light (G) having a complementary color relationship with the magenta (M) to encapsulate the same. It comprises a capsule 4m, and a type C microcapsule 4c enclosing a blue (blue-violet) cyan (C) color-forming substance and a photo-curing substance that cures with red light (R). In the microcapsule layer 4, these three types of microcapsules 4y,
4m and 4c are uniformly dispersed and applied. FIG. 7A shows an example of light absorption characteristics of each type of microcapsules 4y, 4m, and 4c in a state in which a photoinitiator for initiating a curing reaction by polymerization of a photocurable substance is dispersed in a solvent (methanol). FIG. 7B shows an example of light absorption characteristics in a state where the coloring substance is dispersed in a solvent (methanol).

For example, when performing color printing on print paper at 300 dpi, one dot is formed in an area having a diameter of about 85 μm. When the dot area is irradiated with, for example, red light from the exposure head, the photocurable substance in the type C microcapsule 4c is cured,
The photocurable substance in the microcapsules 4m and 4y of types M and Y is not cured, and a red latent image is formed in this dot area. When the dot area is placed under pressure, the cured type C microcapsules 4c are kept as they are, but the uncured type M and Y microcapsules 4m and 4y are crushed, and the respective color-forming substances are imaged. It reacts with the developer of the layer 3 to exhibit a purple-red color and a yellow color, and has a substantially red color as a whole. Type C microcapsules 4
The degree to which c is cured depends on the intensity (light amount) of light applied to the dot area, and depending on the degree, the microcapsules 4c of type C are slightly crushed or not crushed at all, The degree of mixing of blue in the dot area changes. Therefore, the degree of curing of the three types of microcapsules 4y, 4m, 4c differs depending on the color of the irradiation light, and the microcapsules 4y, 4m, 4c
The color developed by the crushing of the color will be different.

As described above, the microcapsules are formed of one type or three types of Y, M, and C, which enable color development according to each of the three wavelengths of light corresponding to the three primary colors of light. Two or more one or two that enable color development in response to light in any particular wavelength range,
Or it may be of any number of types greater than that. Each type of microcapsule is typically
Although the microcapsules are uniformly distributed on the application surface of the paper 1, the distribution of the microcapsules may be different depending on the area of the paper 1 in some cases. Microcapsules 4y, 4
m, 4c typically form a non-overlapping layer, but in some cases the same type of microcapsules are less likely to overlap and are stacked such that the same type of microcapsules form a continuous projection plane. Is also good. In some cases, the same type of microcapsules may be stacked in multiple layers or multiple layers.

In the printer 10 shown in FIG. 1, the print head 1 is intermittently fed by the paper feed mechanisms 11 and 12 at a pitch Z0 in the longitudinal direction Z.
The printing is performed by 3. Print head 13
Is a photosensitive pressure-sensitive print sheet 1 according to the input color pattern.
An exposure head unit 14 for irradiating a color light to form a pressure-sensitive latent image corresponding to a color pattern in the form of a pressure-sensitive dot pattern, and a pressure development head unit 1 for pressing and developing the pressure-sensitive latent image
And 5. This print head 13
While the feeding in the direction is stopped, the side wall 1 of the printer 10 is stopped.
A guide shaft 1 extending in the width direction X of the sheet 1 between 6, 6
7 and the exposure head unit 14 moves the paper 1
The pressure-sensitive latent image is linearly formed in the width direction X of the image forming apparatus, and the latent-image-formed area is linearly developed by the pressure developing head unit 15. Reference numeral 18 denotes a scale representing the position in the scanning direction, and 19 denotes a sensor for reading the scale of the scale. Under the control of a controller 20 including a microprocessor or the like, a driving source 21 and an X-direction and Z-direction driving mechanism 22,
The position control of the print head 13 in the X and Z directions with respect to the sheet 1 is performed via 23.

The exposure head 14 has a light source E including a red light source Er, a green light source Eg, and a blue light source Eb. Each light source E (expressed by the symbol “E” when collectively referring to the light sources of the respective colors or when they are not distinguished from each other) has the same configuration. For example, as shown in FIG. And a substrate 25 supporting the light source main body 24 and supplying power to the light source main body 24, and an opening plate 27 for narrowing light from the light source main body 25 with an aperture or an aperture 26. The light exits from the light source main body 24 and passes through the opening 26. The color light is applied to a spot or dot area 28 on the print paper 1 to form a dot latent image corresponding to the color light applied to the area 28. The adjacent light sources E, E are separated by a partition (not shown). Light source Er, E of each color
The number of g and Eb may be one, two or more, and may be different depending on the color.

The exposure by the light source E is performed by inputting the input color signals R ⁱ , G ⁱ , and B ⁱ representing the image information obtained by the image information processing device 29 such as a digital camera into the controller 20 as shown in FIG. output color signal obtained by color conversion processing by the color conversion apparatus ^{30 R o ', G o'} , the B ^o ', a light source Er of the exposure head 14 through an exposure head driving device 31, Eb,
This is performed by controlling the drive current of Eg.

Next, the color conversion by the color conversion device 30 will be described in detail with reference to FIG. The input color signal S ⁱ in the color conversion device 30 of FIG. 2 is represented by signals R ⁱ , G ⁱ , and B ⁱ , for example, tristimulus values of the RGB color system, and the output color signal S ^o is also output by the printer 10. signal of the print characteristics considered to modified example RGB color system to the printing paper 1 R ^o and ', G ^o', represented by B ^o '. In addition,
As the output color signal S ^o , actually, a printing unit or a print head 13 of a color reproduction device such as the printer 10 is used.
A color system is selected according to the specifications.

It is assumed that the input color signal S ⁱ is provided from the image information processing apparatus 29 such as the digital camera shown in FIG. 1 and is a standard signal excluding the dependence on the device. The input color signal S ⁱ may be a signal of another color system. If desired, the color signal S ⁱ is transmitted to the color conversion device 30 via a conversion unit for converting the color system as shown by an imaginary line 32 in FIG. may be given an input color signal S ^i.

[0039] Each component R ⁱ of the input color signal S ^i, G ^i, B ⁱ is
Each of them is provided in the form of 8-bit data of 256 gradations. In the following, for simplicity of explanation, R ⁱ ,
Let G ⁱ , B ⁱ take 256 integer values from 0 to 255, but if desired, at least one component, eg, R ⁱ , may have a range containing negative values (eg, −1).
27 to +128).

The output color signal S ^o is such that the color of an image to be obtained when the input color signal S ⁱ is input to a device-independent color reproduction device and the color is reproduced is reproduced on the printing paper 1. Is selected and set. In the case of the printer 10 of FIG. 1, the exposure head 14 driven by the exposure head driving device 31
Emission characteristics of the light source bodies Er, Eg, and Eb (e.g., current dependence of emission intensity and spectral distribution characteristics of light emitted from the light source body)
Of the microcapsules 4c, 4m, and 4y of each type C, M, and Y of the microcapsule layer 4 of the printing paper 1 and the characteristics of the image receiving layer 3 are determined by the printing portion of the printer 10. This causes the color reproduction system 33 composed of the print head 13 and the print paper 1 to exhibit a unique color. Here, various characteristics of the microcapsules can depend not only on the spectral distribution of the related light, but also on the color mixing method, temperature, and the like.

The characteristics of the color reproduction system 33 are obtained, for example, by repeating inputting various color signals Sa to the printer 10 and measuring the color C of the print paper 1 when the printer 10 prints on the print paper 1. The color signal Sa to be measured and input to the color reproduction system 33 of the printer 10 to give an arbitrary color C, that is, the output color signal ^So to be output from the color conversion device 30 can be obtained in advance.

[0042] Each component R ^o of the output color signal S ^o ', G ^o',
B ^o ′ is also given in the form of 8-bit data of 256 gradations, and further takes 256 integer values from 0 to 255, respectively. Where ^Ro ',
G ^o ′ and B ^o ′ are color data in a kind of modified R, G, and B systems determined to cancel characteristics peculiar to the color reproduction system 33. The output color signal S to the color reproduction system 33 ^o, as compared easily between the output color of the color reproduction system 33, color data Y ^o that fix the YMC color system ', M ^o', C ^o 'and forms of the color difference is close to the visual L ^* a ^* b ^* was modified in color system ^{L * o', a * o} ', b * o' it may be in the form of.

The color conversion device 30 outputs a three-dimensional input color signal S
^A first color conversion lookup table unit 34 having lookup values divided into eight in each direction of the input color space corresponding to each color component S ⁱ¹ = R ⁱ , S ⁱ² = G ⁱ , S ⁱ³ = B ⁱ of ^ij.
a first color conversion unit 36 having a first color conversion table processing unit 34 including a and a first interpolation calculation unit 35 associated with the processing unit 34 and performing a coarse interpolation calculation, and a second color conversion lookup A second color conversion section 39 having a second color conversion table processing section 37 including a table section 37a, a second color conversion section 39 having a second interpolation calculation section 38 associated with the processing section 37 and performing a precise interpolation calculation, and an input color signal S a discriminator 40 for distributing the input color signal S ⁱ to the first and second color converters 35 and 39 according to the three component values or vector values of ^ij .

The discriminator 40 converts the three-dimensional input color space into a three-dimensional output color space, that is, converts the three-dimensional input signal S ^ij into a three-dimensional output color signal S ^oj . , A reference value that defines the boundary of the second range or the area V2 that needs to be referred to the precise second color conversion look-up table unit as in T2a of FIG. 5 in the two-dimensional case. In this example, the second region, for S ⁱ¹ [m
1, M1] and S ⁱ² are [m2, M2], and S ⁱ³ are [m3, M3]. Where m1, m
2, m3, M1, M2, and M3 are integers of 0 to 8;
1 is m1 or more, M2 is m2 or more, and M3 is m3 or more. Also, [m1, M
At least one of [1], [m2, M2], and [m3, M3] has a finite range. In this case, although it is limited to a single cube, a rectangular parallelepiped, a plane, or a straight line, the second range or the region V2 is a more complicated region such as a combination of a plurality of types or a plurality of them.
It may be a plurality of regions separated from each other.

The discriminator 40 further determines that the input color signal S ^ij is
For S ⁱ¹ , S ⁱ² , and S ⁱ³ , respectively, [m1, M1], [m
2, M2], a second range V defined by [m3, M3]
It is determined whether or not belonging to 2, when the input color signal S ^ij entering the second region V2 sends an input color signal S ^ij to the first color conversion unit 36, the input color signal S ^ij When entering the second area V2, the input color signal S ^ij is sent to the second color conversion unit 39.

When the first color signal processing unit 36 receives the input color signal S ^ij from the discrimination unit 40, the first color signal processing unit 36 processes the upper 3 bits of the 8-bit data S ^ij for each component into the first color conversion table processing. To the first interpolation calculation unit 35. The color conversion table processing section 34 has three types of input color signals S ⁱ¹ , S ⁱ² , S ^i3, that is, R ⁱ , based on a three-dimensional color conversion lookup table 34a similar to the two-dimensional table shown in FIG. G ^i, B
Output color signal data S ^oj _r3g3b3 determined from the upper three bits r3, g3, b3 of ⁱ , and
The adjacent output color signal data (position data in the output color space) in the table 34a is provided to the interpolation calculation unit 35 for the interpolation calculation according to the interpolation calculation method. When linear cubic interpolation is performed by the interpolation calculation unit 35, seven interpolation data including the lookup value r3 + 1, g3 + 1, and b3 + 1 one level higher for each component are simultaneously sent to the interpolation calculation unit 35. As the linear interpolation, other types of interpolation such as six types of tetrahedral interpolation, oblique triangular prism interpolation, and pyramid interpolation may be used instead of cubic interpolation. In these cases, weighting depending on the directions of the three axes may be performed. If the interpolation is a non-linear interpolation including interpolation using another function, output color signal data corresponding to a lookup value other than the closest lookup value is simultaneously sent to the interpolation calculation unit 35 accordingly. Can be On the other hand, the lower 5 bits of the 8-bit data S ^ij from the discriminator 40 are sent to the first interpolation calculator 35, where the interpolation calculation is performed by the interpolation calculator 35, and the color conversion table processor interpolation increment in the output data _S ^ij r3g3b3 from 34 is output as the output color signal S ^o of the interpolated are added.

Therefore, in the first area or range V1 where the coarse interpolation operation is sufficient, the number of data to be held in the first color conversion table 34a can be minimized, and the file capacity and memory occupancy can be minimized. . The lookup value belonging to the second area V2 where the processing by the second lookup table 37a is performed and not used as an end value in the first interpolation calculation unit 35 is the first color. The conversion table 34a may not be provided.

When the second color signal processing unit 39 receives the input color signal S ^ij from the discrimination unit 40, the second color signal processing unit 39 processes the upper 5 bits of the 8-bit data S ^ij for each component into the second color conversion table processing. The data is supplied to a second interpolation calculator 38. In the color conversion table processing unit 37, three types of input color signals S ⁱ¹ , S ⁱ² , and S are based on the three-dimensional second color conversion lookup table unit 37a.
^i3, that is, the value r of the upper 5 bits of each of R ⁱ , G ⁱ , and B ⁱ
Output color signal data S ^{o j} _r5g5b5 determined from 5, g5, b5
And outputs the adjacent output color signal data for the interpolation calculation to the interpolation calculation unit 38 according to the interpolation calculation method. When linear cubic interpolation is performed by the second interpolation calculation unit 38 as in the case of the interpolation calculation unit 35 of the first color signal processing unit 36, the lookup values r5 + 1 and g5 + 1 that are higher by one for each component. , B5 + 1 are simultaneously supplied to the interpolation calculation unit 35. In this case as well, interpolation such as tetrahedral interpolation, oblique triangular prism interpolation, or pyramid interpolation may be used instead of cubic interpolation, and weighting depending on the directions of the three axes may be performed. On the other hand, the lower 3 bits of the 8-bit data S ^ij from the discriminator 40 are sent to the second interpolation calculator 38, where the interpolation calculation is performed by the interpolation calculator 38, and the color conversion table 37 Is added to the output data S ^oj _r5g5b5, and the _resultant is output as an output color signal S ^o after interpolation.

Therefore, if color reproduction is attempted only by the first color conversion section 36, for example, the second color conversion section may be such that the color difference is likely to increase or the color may be uncomfortable in a region where the human visual sensitivity is sensitive. In the region V2, accurate and precise color reproduction can be performed by the second color conversion unit 39.
On the other hand, the second color conversion section 39 can be used only for a very small area of the color space. In such a case, the second color conversion table section 37a should have the second color conversion table section 37a. The number of lookup values of each component, in other words, the file capacity or memory occupancy of the second color conversion table unit 37a can be reduced.

As a result, the color conversion device 30 performs high-accuracy and high-precision color conversion at a high speed while minimizing the file capacity or the memory occupancy of the first and second color conversion table units 34a and 37a. You can go to. In the printer 10, the thus obtained output color signal ^{R o ', G o',} B o '
Of the light source body Er, Eb, E of the exposure head 14 based on
g is driven to emit light, and the corresponding microcapsules 4c, 4m, and 4y of the microcapsule layer 4 of the printing paper 1 are hardened in accordance with the amount of exposure by the light from the main body E, and the microcapsules 4c, 4m, and 4y in the XZ plane of the printing paper 1 Microcapsules 4c,
Color development C, M, and Y by the color former is performed according to the crushing of the microcapsules 4c, 4m, and 4y according to the distribution of the degree of curing of 4m and 4y.

In this printer 10, the exposure characteristics of the exposure head 14 and the microcapsules 4 c and 4
m, an input signal in advance considering the specificity in photocuring properties and coloring characteristics of 4y color reproduction system 33, i.e., the output color signal R ^o of the color conversion apparatus ^{30 ', G o', B} o ' is Since it has been determined, in a color space in a range that can be expressed by the color reproduction system 33 of the printing system 10a including the printer 10 and the printing paper 1, color printing is performed in a desired range with a small color difference and close to the desired color. It can be performed at high speed while minimizing the memory occupancy and the like.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of an example of a printer using a color conversion device according to a preferred embodiment of the present invention.

FIG. 2 is a schematic block diagram of a color conversion device according to a preferred embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a relationship between a one-dimensional input color space and a one-dimensional output color space in which the color conversion device according to the present invention is used.

FIG. 4 is an example of a two-dimensional look-up table using a color conversion device according to a preferred embodiment of the present invention.

FIG. 5 is an example of another look-up table used in combination with the look-up table of FIG. 4 in the color conversion device according to a preferred embodiment of the present invention;

FIG. 6 is an explanatory sectional view of an example of a print sheet and a light source used in the printer of FIG. 1;

7A and 7B show light absorption characteristics of the printing paper of FIG. 6, wherein FIG. 7A is a graph showing an example of light absorption effect characteristics;
(B) is a graph showing an example of light absorption and coloring characteristics.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Photosensitive pressure sensitive printing paper 4 Photosensitive pressure sensitive microcapsule layer 10 Printer 10a Printing system 30 Color conversion device 35 First interpolation operation unit 36 Second interpolation operation unit 34 First color conversion table processing unit 34a, T2 First Color conversion (lookup) table section 37 Second color conversion table processing section 37a, T2a Second color conversion (lookup) table section Ds Reference interval between adjacent lookup values Da Small interval between adjacent lookup values S ⁱ , S ^ij input color signals S ⁱ¹ , S ⁱ² , S ⁱ³ input color signal components S ^o , S ^ok output color signals S ^o1 , S ^o2 , S ^o3 output color signal components V 1 first range (region) V 2 Second range (area)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C262 AA24 BA01 BC01 BC15 5B057 AA11 CA01 CA08 CA12 CB01 CB08 CB12 CC01 CE18 CH07 DB02 DB06 DB09 5C077 LL17 LL18 MP08 PP31 PP32 PP33 PP38 PQ23 RR19 5C079 HB02 LA11H02MA NA11

Claims (11)

[Claims] 1. A color having a magnitude of each component of a discrete input color signal as a lookup value and a magnitude of each component of an output color signal as a conversion value in order to convert an input color signal into a corresponding output color signal. A color conversion table processing unit having a conversion lookup table, and performing an interpolation operation on each component of the input color signal having an intermediate magnitude between adjacent lookup values in the table, and An interpolation operation unit for obtaining an interpolation value, wherein the color conversion table is based on an interval between adjacent lookup values among lookup values in a first range for at least one component of the input color signal. A color conversion device, comprising: a first color conversion table unit corresponding to an interval; and a second color conversion table unit having a lookup value at an interval smaller than the reference interval in a second range. 2. The color conversion device according to claim 1, wherein the first and second color conversion tables are configured to convert an input color signal composed of at least three components into a corresponding output color signal. 3. The color according to claim 1, wherein the first range covers substantially the entire range of the input color space for displaying the input color signal, and the second range is a part of the input color space. Conversion device. 4. The color range according to claim 1, wherein the second range is a color region in which a color reproduction system to which an output color signal is to be input has a unique color reproduction characteristic. Conversion device. 5. The color range having a high gradation resolution of a color reproduction system including a printing unit driven by an output color signal and a printing paper printed by the printing unit. Color conversion device. 6. The color conversion device according to claim 1, wherein the second range is a color region having high gradation resolution of human vision. 7. The color conversion device according to claim 1, wherein the second range is a color region having a high appearance frequency in the input color signal. 8. A color conversion device having a color conversion look-up table having lookup values at different intervals depending on the region of the input color space. 9. A printer having the color conversion device according to claim 1, wherein a printer is configured to be driven by an output color signal from the color conversion device. . 10. The printer according to claim 9, wherein the printer is configured to perform printing on print paper coated with photosensitive pressure-sensitive microcapsules. 11. A printing system comprising the printer according to claim 9, and printing paper printed by the printer, wherein the printing paper is a printing paper coated with a photosensitive microcapsule.