Patent Application
20100231912
The present invention relates to a color-measuring method for body, and to a color-measuring apparatus. A color-measuring method for body and a color-measuring apparatus according to the present invention can be utilized suitably for color reproduction in order to reproduce predetermined colors in apparatus for doing color printing, color displaying, and the like, for instance.
In general, in the case of carrying out color reproduction with display, printer, and the like, such a method has been adopted that, based on the three-primary-color theory, an original tristimulus value and an output tristimulus value are coupled (see Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2003-333,355, and Japanese Unexamined Patent Publication (KOKAI) Gazette No. 7-50,760, for instance).
In such color reproduction, in order to identify the original tristimulus value, a color of body is measured using a spectroscopic color-measuring method, for instance. In this spectroscopic color-measuring method, a spectrophotometer, which has a built-in specific light source for measurement and which is adapted for measuring body colors, has been used.
Specifically, in the spectroscopic color-measuring method, a light is emitted from the specific light source for measurement, light source which is built-in inside the spectrophotometer serving as a body-color measuring instrument, to a body, and thereby a reflectivity (spectroscopic-solid-angle reflectivity) for every wavelength of a reflected light from the body (for every spectrum thereof) is measured in a visible-light wavelength range of 400-700 nm, for instance. And, tristimulus values are found by means of such a calculation that values of the reflectivities (spectroscopic distribution) are multiplied by a color-matching function to carry out integration.
By the way, a body color can be determined depending by means of the dispersion of light source and the reflectivity of body, that is, by means of (dispersion of light source)×(reflectivity of body).
However, a body including fluorescent material has such a property that, in the low-wavelength section of visible-light range, it is excited to increase the reflectivity by means of the ultraviolet-range energy of light source (see
Here, there is such a case that ultraviolet is included abundantly in the light source of living room in general; on the contrary the ultraviolet content is less in the measurement light source of the above-described spectrophotometer serving as a body-color measuring instrument. Accordingly, even when measuring the reflectivity of body including fluorescent material while irradiating it with a specific light source for measurement from this spectrophotometer, the value has become different from the actual reflectivity. That is, when the light source of living room differs from the measurement light source of spectrophotometer, a color, which is different from a color of body including fluorescent material that an observer can view actually, has come to be measured with the spectrophotometer.
For example, as illustrated in
Therefore, even when identifying a color of body including fluorescent material using a spectrophotometer for body-color measurement that possesses a specific light source for measurement, it has become different from an actual color of the body that an observer is viewing in a living room, and thereby there has been such a problem that it is not possible to accurately measure a color of body including fluorescent material.
The present invention has been done in view of the aforementioned circumstances, and it is a technical assignment to be solved to provide a color-measuring method for body and a color-measuring apparatus that can, even when measuring a color of such a body, like a body including a fluorescent material, whose reflectivity has changed depending on the type of light source, measure the color of such a body accurately.
A color-measuring method for body according to the present invention, which solves the aforementioned assignment is a body color-measuring method of measuring a color of light being emitted from a body in a predetermined measurement environment, and which is characterized in that it is equipped with:
Here, the “predetermined measurement environment” means a measurement environment in a living room, or the like, where an observer is present.
According to this color-measuring method for body, the reference-color measurement step, and the objective-portion measurement step are executed using a light-source-color measuring instrument, without irradiating the reference-color portion, and the measurement-objective portion, with a light source for measurement. That is, according the body-color-measuring method of the present invention, spectroscopic-radiation luminances of lights being emitted from the reference-color portion and measurement-objective portion, or tristimulus values thereof, are measured using a light-source-color measuring instrument, without irradiating them with a light source for measurement. Accordingly, the reference-color measurement value being obtained at the reference-color measurement step, and the objective-portion measurement value being obtained at the objective-portion measurement step do not include any influences, which result from being irradiated with the measurement light source, at all. Therefore, it is possible to measure a color of body accurately by finding a color of the measurement-objective portion by means of computation from a ratio between the objective-portion measurement value and the reference-color measurement value.
Thus, according to the body-color-measuring method of the present invention, since the reference-color measurement value, and the objective-portion measurement value are obtained using a light-source-color measuring instrument, without being irradiated with a measurement light source, and thereby a body color of body is found from the measurement values by means of computation, such an accurate measurement that does not include any adverse effects (measurement errors) resulting from the measurement light source becomes possible even in the case of measuring a color of such body, like a body including fluorescent material, that the reflectivity has changed depending on the type of light source.
Therefore, in accordance with the body-color-measuring method of the present invention, even in the case of measuring a color of such body, like a body including fluorescent material, that the reflectivity has changed depending on the type of light source, it is possible to accurately measure a color of the body that an observer is viewing actually in the measurement environment. Hence, when the method according to the present invention is executed in a living room or the like that possesses a certain measurement environment and then the measurement outcome is applied to a color management system (CMS) that is based on colorimetric color reproduction, it is possible to materialize optimum color reproduction for the measurement environment.
In a preferable aspect of the color-measuring method for body according to the present invention,
When finding a spectroscopic-radiation luminance factor β(λ), which serves as a reflectivity-equivalent value that is equivalent to a spectroscopic-solid-angle reflectivity of the measurement-objective portion, using a spectroscopic-radiation luminance meter as the light-source-color measuring instrument and then finding a color of the measurement-objective portion from the spectroscopic-radiation luminance factor β(λ) and a color-matching function, it is possible to more accurately identify a color that an observer can view actually.
In the case of thus obtaining the reference-color measurement value Lw(λ) of spectroscopic-radiation luminance and the objective-portion measurement value L01(λ) of spectroscopic-radiation luminance, it is preferable that, when taking a theoretical value of a spectroscopic-radiation luminance of perfectly-diffuse reflective surface as Lw*(λ) and taking the spectroscopic-radiation luminance factor of said reference-color portion as βw(λ)=Lw(λ)/Lw*(λ), the spectroscopic-radiation luminance factor β(λ) of said measurement-objective portion can be found by means of Equation (1) below at said color identification step.
Moreover, in the case of finding a color of the measurement-objective portion from the thus obtained spectroscopic-radiation luminance factor β(λ) of the measurement-objective portion, it is preferable that a color of the measurement-objective portion can be found as a relative value by means of Equation (2) below.
When a color of the measurement-objective portion can be thus found as a relative value, it becomes possible to identify a color, which possesses certain brightness that is not dependent on the brightness of measurement environment, because the brightness of the color according to the measurement outcome does not change due to the brightness of measurement environment.
Moreover, when the tristimulus values X, Y and Z of an XYZ color specification system are thus found, it is possible to readily convert these into the other color specification systems, such as an L*a*b* color specification system, a Munsell color specification system and an Luv color specification system.
Further, by using a spectroscopic-radiation luminance meter as the light-source-color measuring instrument, a highly-accurate measurement becomes possible.
In a preferable aspect of the color-measuring method for body according to the present invention,
When a color of the measurement-objective portion can be thus found as a relative value, it becomes possible to identify a color, which possesses certain brightness that is not dependent on the brightness of measurement environment, because the brightness of the color according to the measurement outcome does not change due to the brightness of measurement environment.
Moreover, when using a color meter as the light-source-color measuring instrument, the measuring instrument becomes less expensive and compact.
Further, when the tristimulus values X, Y and Z of an XYZ color specification system are found, it is possible to readily convert these into the other color specification systems, such as an L*a*b* color specification system, a Munsell color specification system and an Luv color specification system.
In a preferable aspect, the color-measuring method for body according to the present invention can execute the measurement in said reference-color measurement step, and the measurement in said objective-portion measurement step within a case that is adapted into an irradiation condition being equivalent to that of said measurement environment.
According to this color-measuring method for body, since the measurement in the reference-color measurement step, and the measurement in the objective-portion measurement step are executed within an case that is adapted into an irradiation condition being equivalent to that of the measurement environment, an accurate measurement, which is not affected by environmental changes outside the case, becomes possible under such a stable irradiation condition being inside the case.
In a preferable aspect of the color-measuring method for body according to the present invention,
According to this color-measuring method for body, it is possible to accurately measure a plurality of colors in the patched-color sheet.
A color-measuring apparatus according to the present invention is one which is characterized in that it is equipped with:
According to this color-measuring apparatus, it is possible to measure a color of light being emitted from the measurement-objective substance, which is retained on the movable retainer table, in a measurement direction, using the light-source-color measuring instrument, but without irradiating the measurement-objective substance with a light source for measurement. Accordingly, even in the case of measuring a color of such body, like a body including fluorescent material, that the reflectivity has changed depending on the type of light source, such an accurate measurement that does not include any adverse effects (measurement errors) resulting from the measurement light source becomes possible.
Moreover, according to this color-measuring apparatus, since the movable retainer table that retains the measurement-objective substance can reciprocate in the X-direction and in the Y-direction, and since a position of this movable retainer table in the X-direction and in the Y-direction and a measurement by means of the light-source-color measuring instrument are controlled automatically by means of the controller means, it is possible to automatically carry out a color measurement at any position on the measurement-objective substance. Therefore, when using a colored patch, for instance, as the measurement-objective substance, it becomes possible to automatically measure respective colors, which constitute the colored patch, consecutively.
In a preferable aspect of the color-measuring apparatus according to the present invention, said movable retainer table is made rotatable within a plain including the X-direction and the Y-direction.
According to this color-measuring apparatus, since the movable retainer table is made rotatable, by means of positioning the measurement-objective substance by rotating the movable retainer table by a predetermine magnitude in a predetermined direction after retaining it on the movable retainer table, it is possible to accurately align a measurement-developing direction in the measurement-objective substance with the X-direction and Y-direction that the movable retainer table moves, without ever positioning the measurement-objective substance accurately in said rotary direction when retaining it onto the movable retainer table.
In a preferable aspect of the color-measuring apparatus according to the present invention,
According to this color-measuring apparatus, it is possible to securely retain the sheet serving as the measurement-objective substance onto the retainer surface of the movable retainer table by means of the electrostatic attraction.
In a preferable aspect, the color-measuring apparatus according to the present invention can be equipped with a case possessing a light source for illumination, the light source being equivalent to that of a measurement environment; and
Here, “possessing a light source for illumination, the light source being equivalent to that of a measurement environment” means to possess a light source for illumination, light source which is equivalent to a light source for illumination in a living room, or the like, where an observer is present, so that an illumination condition within the case becomes an illumination condition that is equivalent to a measurement environment in the living room, or the like.
According to this color-measuring apparatus, since a measurement within such a case that possesses a light-source condition being equivalent to that of a measurement environment becomes possible, an accurate measurement, which is not affected by environmental changes outside the case, becomes possible under such a stable irradiation condition being inside the case.
Hereinafter, specific embodiments according to the present invention will be explained while referring to the drawings.
The present embodiment is one which embodies claims 1-4 and 6-11, and is one for measuring respective colors in a patched-color sheet that serves as a measurement-objective substance.
First of all, a color-measuring apparatus illustrated in
The case 1 is provided with a back wall surface la and both left and right surfaces 1b and 1c that surround the side faces, thereby having a forward opening 1d. Moreover, in a ceiling wall surface le of the case 1, there is provided a light source 11 for illumination that is identical with a light source for illumination that a measurement environment in which an observer is present, that is, a living room where an observer is present is equipped with. Thus, the inside of the case 1 is adapted into being under an illumination condition that is equivalent to a measurement environment in a living room where an observer is present.
The base table 2 is placed on a floor surface if of the case 1; one of the opposite end sides is disposed within the case 1; and additionally the other one of the opposite end sides is equipped with a plate-shaped body 21, which sticks out through the forward opening la of the case 1 forward (the left direction in
The movable retainer table 3 is disposed on the base table 2 reciprocably in the X-direction (in the horizontal direction, i.e., in the left/right direction in
Moreover, the movable retainer table 3 is made rotatable about a rotary center, which the center of the movable retainer table 3 makes, on the base table 2 within a plane that includes the X-direction and the Y-direction. A rotary mechanism for rotating the movable retainer table 3 is not limited in particular; for example, however, it is possible to adopt a rotary mechanism which is equipped with: a first rotary shaft one of whose opposite end sides is fixed to a later-described rotary-angle adjuster knob 32; a first gear being fixed to the other one of the opposite end sides of this first rotary shaft, thereby being made rotatable about the first rotary shaft; a second rotary shaft one of whose opposite end sides is fixed to the movable retainer table 3 in such a direction that crosses the first rotary shaft orthogonally; and a second gear being fixed to the other one of the opposite end sides of this second rotary shaft, and meshing with the first gear, thereby being made rotatable about the second rotary shaft crossing the first rotary shaft orthogonally.
In addition, the movable retainer table 3 is equipped with an electrostatic attracter means 31 for electrostatically attracting the patched-color sheet 8 serving as a measurement-objective substance onto the retainer surface 3a. This electrostatic attracter means 31 can be constituted of vacuum system or “Cueron” system (produced by TAIHEI KAGAKU CORPORATION).
Note that the base table 2 is equipped with; an X-direction transfer switch 24 for driving the driver means 4 by means of an observer's manual operation to transfer the moveable retainer table 3 in the X-direction; a Y-direction transfer switch 25 for driving the driver means 4 by means of an observer's manual operation to transfer the movable retainer table 3 in the Y-direction; and an attracter switch 26 for actuating the electrostatic attracter means 31 by means of an observer's manual operation. Moreover, the movable retainer table 3 is equipped with a rotary-angle adjuster knob 32 for rotating the movable retainer table 3 by means of an observer's manual operation.
The light-source-color measuring instrument 5 is retained to a stand 22, which is mounted upright on the plate-shaped body 21 of the base table 2, so that the focus of the light-source-color measuring instrument 5 agrees with a measurement position “P,” which positions at the center of the base table 2, and so that the focus falls on the measurement position “P” from a 45-degree oblique direction with respect to the surface of the base table 2. Thus, the light-source-color measuring instrument 5 is adapted into being capable of measuring a color of light, which is emitted from a position that corresponds to the measurement position “P” in the patched-color sheet 8 being retained on the movable retainer table 3, in a measurement direction (in the arrow “Q” direction in
In the present embodiment, as the light-source-color measuring instrument 5, a spectroscopic-radiation luminance meter, which does not possess any light source for measurement, is adopted.
The controller means 6 comprises a personal computer, which is equipped with a CPU, an input means (keyboard), and the like. This controller means 6 is connected to the driver means 4, light-source-color measuring instrument 5 and displayer means (display monitor) 7, controls the position of the movable retainer table 3 in the X-direction and Y-direction and the measurement by means of the light-source-color measuring instrument 5 automatically, and additionally lets the displayer means 7 display the resulting measurement outcomes.
Moreover, in the patched-color sheet 8 that serves as a measurement-objective substance, a plurality of measurement-objective portions 8a comprising a plurality of different colors, and a plurality of reference-color portions 8b are arranged at the paper surface. Although a color of the reference-color portions 8b is not limited in particular, it can suitably be adapted into being a white color. In this patched-color sheet 8, the reference-color portions 8b are arranged so that, when measuring the respective patches in a certain order, the intervals between them become equal substantially in that order. For example, when measuring the patched-color sheet 8, this can be done in the following manner: a patch of a first piece of the reference-color portions 8b is measured first off and thereafter patches of 10 pieces of the measurement-objective portions 8a are measured; and then a patch of a second piece of the reference-color portions 8b is measured subsequently and thereafter patches of 10 pieces of the measurement-objective portions 8a are measured similarly; and then a patch of a third piece of the reference-color portions 8b is measured subsequently; and thereby the reference-color portions 8b are arranged so that the intervals between them become equal substantially in the order of measuring the respective patches.
As illustrated in
A color-measuring method using the color-measuring apparatus having the aforementioned construction will be hereinafter explained.
First of all, after placing the patched-color sheet 8 on the movable retainer table 3, the attracter switch 26 is turned on to attract the patched-color sheet 8 onto the retainer surface 3a by means of the electrostatic attracter means 31. And, by means of adjusting the rotary-angle adjuster knob 32 repeatedly, the movable retainer table 3 is rotated by a predetermined angle in a predetermined direction so that, when the X-direction transfer switch 24 is turned on to transfer the movable retainer table 3 in the X-direction, the point of regard of the light-source-color measuring instrument 5 scans the patches of the patched-color sheet 8 accurately in the horizontal direction (X-direction) and additionally so that, when the Y-direction transfer switch 25 is turned on to transfer the movable retainer table 3 in the Y-direction, the point of regard of the light-source-color measuring instrument 5 scans the patches of the patched-color sheet 8 accurately in the vertical direction (Y-direction).
Moreover, by means of operating the X-direction transfer switch 24 and the Y-direction transfer switch 25, the movable retainer table 3 is transferred in the X-direction and in the Y-direction so as to position the upper left patch 81 in the patched-color sheet 8 at the measurement position “P,” and the resulting position is input into the controller means 6 and is registered therewith as a measurement starting point. Similarly, the movable retainer table 3 is transferred in the X-direction and in the Y-direction so as to position the upper right patch 82 in the patched-color sheet 8 at the measurement position “P,” and the resulting position is input into the controller means 6 and is registered therewith as an X-direction measurement ending point. Similarly, the movable retainer table 3 is transferred in the X-direction and in the Y-direction so as to position the lower right patch 83 in the patched-color sheet 8 at the measurement position “P,” and the resulting position is input into the controller means 6 and is registered therewith as a Y-direction measurement ending point. Note that, through these operations, the value of “EndX” (the distance from the left-end patch to the right-end patch) and the value of “EndY” (the distance from the upper-end patch to the lower-end patch) are memorized in the controller means 6.
Further, the number of the X-direction patches in the patched-color sheet 8 is input into the controller means 6 and is registered therewith as a number of X-direction measurement points. Similarly, the number of the Y-direction patches in the patched-color sheet 8 is input into the controller means 6 and is registered therewith as a number of Y-direction measurement points.
And, the reference-color measurement step, the objective-portion measurement step, and the color identification step are executed while automatically controlling the position of the movable retainer table 3 in the X-direction and Y-direction and the measurement by means of the light-source-color measuring instrument 5 by means of the controller means 6 in an automatic mode, thereby measuring colors of the respective measurement objective portions 8a in the patched-color sheet 8; and then the resulting measurement outcomes are displayed on the displayer means 7 and additionally are memorized in the controller means 6.
At this moment, in said reference-color measurement step, a plurality of spectroscopic-radiation luminances of lights that are emitted from a plurality of the reference-color portions 8b being positioned at the measurement position “P” are measured by means of a spectroscopic-radiation luminance meter serving as the light-source-color measuring instrument 5, and an averaged value of them is obtained as a reference-color measurement value Lw (λ) of a spectroscopic-radiation luminance.
Moreover, in said objective-portion measurement step, spectroscopic-radiation luminances of lights that are emitted from a plurality of the measurement-objective portions 8a being positioned at the measurement position “P” are measured respectively by means of a spectroscopic-radiation luminance meter serving as the light-source-color measuring instrument 5, and objective-portion measurement values L01(λ) of a plurality of the spectroscopic-radiation luminances are obtained.
And, in said color identification step, spectroscopic-radiation luminance factors β(λ), which serve as reflectivity-equivalent values that are equivalent to spectroscopic-solid-angle reflectivities of the respective measurement-objective portions 8a, are found respectively from said reference-color measurement value Lw(λ) and said respective objective-portion measurement values L01(λ) using known spectroscopic-radiation luminance factors βw(λ) of the reference-color portions 8b.
Specifically, when taking a theoretical value of a spectroscopic-radiation luminance of perfectly-diffuse reflective surface as Lw*(λ) and taking said spectroscopic-radiation luminance factors of the reference-color portions 8b as βw(λ)=Lw(λ)/Lw*(λ), the spectroscopic-radiation luminance factors of the respective measurement-objective portions 8a, β(λ)=L01(λ)/Lw*(λ), are found by means of said Equation (1).
Further, in said color identification step, colors of the respective measurement-objective portions 8a are found as relative values of tristimulus values in an XYZ color specification system by means of said Equation (2) from said spectroscopic-radiation luminance factors β(λ) of the respective measurement-objective portions 8a and a color-matching function.
Thus, according the body-color-measuring method of the present embodiment, the spectroscopic-radiation luminances of the lights being emitted from the reference-color portions 8b and measurement-objective portions 8a are measured by executing the reference-color measurement step and objective-portion measurement step using a spectroscopic-radiation luminance meter that serves as the light-source-color measuring instrument 5, without irradiating the reference-color portions 8b and measurement-objective portions 8a with a light source for measurement.
Accordingly, the reference-color measurement value Lw(λ) being obtained at the reference-color measurement step, and the objective-portion measurement values L01(λ) being obtained at the objective-portion measurement step are those that do not include any influences resulting from being irradiated with a light source for measurement. Therefore, even when the patched-color sheet 8 is one that includes a fluorescent material, the reference-color measurement value Lw(λ), and the objective-portion measurement values L01(λ) become accurate measurement values that do not include any adverse effects (measurement errors) resulting from a light source for measurement. Hence, it is possible to more accurately measure the respective colors of the patched-color sheet 8 that are being viewed by an observer actually.
Moreover, in the present embodiment, since it is possible to find the colors of the respective measurement-objective portions 8a as the relative values of tristimulus values in an XYZ color specification system, the brightness of the colors according to the measurement outcomes do not change at all due to the brightness of measurement environment. Accordingly, it becomes possible to identify colors with certain brightness that is not dependent on the brightness of measurement environment.
Note that the tristimulus values X, Y, Z being thus obtained can be readily converted into the other color specification systems, such as an L*a*b* color specification system and a Munsell color specification system.
Therefore, in accordance with the color-measuring method for body according to the present embodiment, it is possible to accurately measure the respective colors of a patched-color sheet 8, colors which an observer is viewing actually in a measurement environment where the observer is present, even when the patched-color sheet 8 is one that includes a fluorescent material. Hence, when the method according to the present embodiment is executed in a living room or the like that possesses a certain measurement environment and then the measurement outcomes are applied to a color management system (CMS) that is based on colorimetric color reproduction, it becomes possible to materialize optimum color reproduction for the measurement environment.
Moreover, according to the present embodiment, since the measurement in said reference-color measurement step, and the measurement in said objective-portion measurement step are executed within the case 1 that is adapted into an irradiation condition being equivalent to that of a measurement environment in a living room where an observer is present, an accurate measurement, which is not affected by environmental changes outside the case 1, becomes possible under such a stable irradiation condition being inside the case 1.
Moreover, according to the present embodiment, it becomes possible to automatically measure the respective colors, which constitute the patched-color sheet 8, consecutively by means of said color-measuring apparatus.
In addition, according to the present embodiment, since a spectroscopic-radiation luminance meter is used as the light-source-color measuring instrument 5, a high-accuracy measurement becomes possible.
The present embodiment is one which embodies claims 1 and 5-11. According to the present embodiment, a color luminance meter that serves as a color meter is used instead of using a spectroscopic-radiation luminance meter that serves as the light-source-color measuring instrument 5 in said Embodiment No. 1.
Specifically, in a color-measuring method for body according to this embodiment, tristimulus values of lights being emitted from a plurality of the reference-color portions 8b are measured using a color luminance meter that serves as the light-source-color measuring instrument 5 at said reference-color measurement step, thereby obtaining an averaged value of them as a reference-color measurement value (Xw, Yw, Zw) of the tristimulus values.
Moreover, at said objective-portion measurement step, tristimulus values of lights being emitted from the respective measurement-objective portions 8a are measured by means of the color luminance meter that serves as the light-source-color measuring instrument 5, thereby obtaining objective-portion measurement values (X′, Y′, Z′) of a plurality of the tristimulus values.
And, at said color identification step, colors of the respective measurement-objective portions 8a are found as relative values of tristimulus values in an XYZ color specification system by means of said equation (3) from the reference-color measurement value (Xw, Yw, Zw) and objective-portion measurement values (X′, Y′, Z′) using (Xw, Yw*, Zw), a theoretical value of a tristimulus value of perfectly-diffuse reflective surface, and r=Yw*/Yw, a known calibrated value for said reference-color portions.
Moreover, according to the present embodiment, since a color meter is used as the light-source-color measuring instrument 5, the measuring instrument becomes less expensive and compact.
Since the other constructions and operations/effects are the same as those of said Embodiment No. 1, their explanations are omitted herein.
Note that, according to the above-described embodiments, although the patched-color sheet 8 is adopted as a measurement-objective substance, the measurement-objective substance to which the present invention is applicable is not limited to this, that is, it is possible to apply the present invention to color measuring for a variety of bodies.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-081439 | Mar 2006 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2007/057022 | 3/23/2007 | WO | 00 | 9/22/2008 |
