JP4590255B2 - Evaluation apparatus and evaluation method - Google Patents

Description

The present invention relates to an evaluation apparatus and an evaluation method, and more particularly to an evaluation apparatus and an evaluation method for detecting metallic luster generated in a printed image.

  When evaluating an image printed on a recording medium such as a hard copy, the color of the illumination reflected in the image on the surface of the recording medium to be evaluated appears to have a metallic luster that is different from the original color of the illumination. May occur, and this phenomenon is called “bronze phenomenon”. Note that this bronze phenomenon means the case where the color of the illumination reflected in the image on the surface of the recording medium is different from the original color of the illumination, and the brightness of the reflected illumination reflects the image. The phenomenon that the brightness looks different is not called a bronze phenomenon.

  In general, the bronze phenomenon is treated as an element that hinders the observation of an image due to color development different from the original color of illumination. In many cases, the evaluation of the bronze phenomenon in a recording medium is currently based on the subjectivity of the observer.

  As in the above-described conventional method, in the method of evaluating the bronze phenomenon based on the subjectivity of the observer, the evaluation differs depending on the individual observer, the degree of eye fatigue of the observer, the observation conditions, etc., and stable evaluation. It is difficult to get a value.

  Therefore, it is preferable to always obtain a stable evaluation value by using a physical evaluation method that causes few changes in the evaluation, but at present there is no means for physically evaluating the bronze phenomenon in the recording medium. It was.

The present invention has been made to solve the above-described problems, and an object thereof is to provide an evaluation apparatus and an evaluation method for quantitatively evaluating the generated bronze, that is, metallic luster.

  The present invention has the following configuration as one means for achieving the above object.

That is, an evaluation apparatus for calculating a metallic gloss evaluation value of an evaluation recording medium, and measuring regular reflection light from the evaluation recording medium illuminated by an illumination unit to obtain information of the regular reflection light an optical information obtaining unit, an illumination optical information obtaining means for obtaining information of the illumination light, by calculating the chroma of the specular reflection light based on said information of the illumination light and the specular reflected light information, the object evaluation a metallic luster calculating means for calculating a metallic luster evaluation value of the recording medium, characterized by having a.

  According to the present invention, it is possible to quantitatively evaluate the generated metallic luster based on information on illumination light and information on regular reflection light on the surface of a recording medium to be evaluated.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with reference to the accompanying drawings.

<First Embodiment>
FIG. 1 is a block diagram showing a configuration of a bronze evaluation apparatus used in the evaluation method of the present embodiment. FIG. 2 is a diagram schematically showing an optical system of the evaluation apparatus in the present embodiment.

  In FIG. 1, an illuminating unit 11 includes a light source such as a halogen, transmits light emitted from the light source through an optical fiber or the like, and illuminates the recording medium surface from a predetermined angle. As the light source, pulse xenon or the like may be used in addition to halogen. The recording medium is fixed to a predetermined installation base.

  The reflected light receiving unit 12 receives the reflected light from the recording medium surface of the illumination light by the illumination unit 11. Here, since the bronze phenomenon is related to the color of the reflected illumination image, the reflected light described above is, for example, regular reflection or reflected light in the vicinity of regular reflection. For this reason, in the evaluation apparatus of the present embodiment, as shown in FIG. 2, a light receiving unit (reflected light receiving unit 23 in FIG. 2) is installed at a position in the regular reflection direction of illumination light. In addition, the evaluation apparatus of this embodiment has a light shielding unit for shielding light from the outside. Information on the reflected light received by the reflected light receiving unit 12 is temporarily held in the reflected light information storage unit 13. The reflected light information storage unit 13 is a storage device on a PC, for example.

  The illumination light receiver 14 directly measures the illumination light. For example, although not shown in FIG. 2, the illumination light receiving unit 14 of the present embodiment may be provided anywhere as long as the illumination light can be directly measured. Information on illumination received by the illumination light receiving unit 14 is temporarily held in the illumination information storage unit 15. The illumination information storage unit 15 is a storage device on a PC, for example.

  Since the light characteristics may change due to changes in the light source over time, etc., in the present embodiment, an example in which illumination photometry is performed every time the amount of bronze is measured in the illumination light receiving unit 14 will be described. The illumination data may be stored in the illumination information storage unit 15 and used.

  The reflected light receiving unit 12 and the illumination light receiving unit 14 include a spectroscope such as a diffraction grating that splits the received light and a detector such as a photodiode that detects the split light. In order to perform highly accurate measurement, it is preferable that the detectors of the reflected light receiving unit 12 and the illumination light receiving unit 14 have the same specifications. As this detector, a photomultiplier tube or the like may be used.

  The reflected light information and the illumination information described above are the spectral intensities as the output values of the detectors included in each of the reflected light receiving unit 12 and the illumination receiving unit 14. Even if other spectral characteristic values such as spectral radiance are used as the spectral intensity, the same argument as this embodiment described below is established.

  The bronze amount calculation unit 16 performs a predetermined process, which will be described later, on the basis of the spectral data of the reflected light stored in the reflected light information storage unit 13 and the spectral data of the illumination stored in the illumination information storage unit 15. A bronze amount indicating the size of the gloss is calculated.

  Hereinafter, the processing procedure in the bronze amount calculating unit 16 will be described with reference to the flowchart of FIG.

  First, the spectroscopic data of specular light stored in the reflected light information storage unit 13 and the spectroscopic data of illumination stored in the illumination information storage unit 15 are input (S301). Next, tristimulus values Xx, Yx, Zx in the XYZ color system are calculated according to the following equation (1) from the spectroscopic data of specularly reflected light of the recording medium to be evaluated input in step S301 (S302). ). Here, in the present embodiment, in calculating the tristimulus values Xx, Yx, Zx of specularly reflected light, the calculation method of the tristimulus value of the light source color is applied instead of the method of calculating the tristimulus value of the object color. Yes. Hereinafter, this reason will be described with reference to FIG.

  FIG. 4 schematically shows the spatial distribution of the amount of reflected light on the surface of the recording medium to be evaluated. 41 is a light source that illuminates the recording medium surface, 42 is a recording medium to be evaluated, 43 Is a specular reflection component of the light reflected by the evaluation recording medium, and 44 is a diffuse reflection component of the light reflected by the evaluation recording medium. Normally, when measuring color, since specularly reflected light is not measured, an optical system that measures the diffuse reflection component 44 shown in FIG. 4 is used. However, in the present embodiment, an optical system that measures specular reflection light, that is, specular reflection component 43, is used for the reason described below.

  That is, for example, when the evaluated recording medium 42 has a high gloss level such as glossy paper, the specular reflection component 43 is large, so the diffuse reflection component 44 used in normal color measurement is a light quantity range. Are significantly different from each other, and the range of measured values of specular reflection light is close to that of a light source. That is, it is similar to a measurement system that directly measures light from a light source.

  Therefore, in the present embodiment, when calculating the tristimulus value XxYxZx of the regular reflection light of the recording medium 42 to be evaluated, the relative spectral distribution of the regular reflection light is used instead of the method of calculating the tristimulus value of the object color by the normal reflection. It is regarded as the relative spectral distribution of the light source and follows the method of calculating the tristimulus values of the light source color. This calculation formula is shown in Formula (1).

  In this embodiment, normalization by multiplication of a proportional constant is not performed, but normalization such as multiplication by the following equation (2) may be performed.

  Next, tristimulus values in the XYZ color system are calculated from the spectral data of illumination input in step S301 (S303). Specifically, the illumination spectral data is multiplied by the color matching function of JIS Z 8782, and the lighting tristimulus value XsYsZs is calculated based on the XYZ color system of JIS Z 8701. That is, the tristimulus value XsYsZs is calculated from the spectral data of the illumination by the equation (3) based on the method for calculating the tristimulus value of the light source color. In Equation (3), k is a proportionality constant, and is determined so that the Ys value of the tristimulus value matches the photometric quantity.

  Next, from the tristimulus value XxYxZx of regular reflection of the recording medium 42 to be evaluated calculated in step S302 and the tristimulus value XsYsZs of illumination calculated in step S303, the recording medium 42 to be evaluated is based on JIS Z 8729. Regular reflection L * a * b * is calculated (S304). This calculation formula (4) is shown below. In the formulas defined in JIS Z 8729, the values of X, Y, and Z are tristimulus values (Xx, Yx, Zx) is applied, and the tristimulus values (Xs, Ys, Zs) of the light source are applied as the values of Xn, Yn, Zn.

  Then, the ab chroma is calculated based on JIS Z 8729 from the a * b * value of the specularly reflected light of the recording medium 42 to be evaluated calculated in step S304 (S305), and the calculated ab chroma is the size of the bronze. Is quantitatively evaluated as a bronze amount B. This calculation formula (5) is shown below.

Note that since the bronze phenomenon is related not to the brightness of the image of the reflected illumination but to its color, the present embodiment does not use the L * value, which is a value indicating the brightness.
In this embodiment, the tristimulus value in the XYZ color system is calculated from the spectral intensity and L * a * b * is calculated. However, the color of XYZ or the like is detected using a detector having a color filter. Spatial information may be measured.

  The information stored in the reflected light information storage unit 13 and the illumination information storage unit 15 is not limited to spectral data, and tristimulus values in the XYZ color system calculated based on the spectral data may be stored. In this case, the bronze amount calculation unit 16 only needs to perform the processes of steps S304 and S305 in FIG.

  As described above, according to the present embodiment, based on the spectral data of the illumination light and the spectral data of the specular reflection light on the surface of the recording medium to be evaluated, the L * of the specular reflection light from the tristimulus values XYZ. It is possible to calculate a * b * and quantitatively evaluate the bronze phenomenon by the ab chroma.

<Second Embodiment>
Hereinafter, a second embodiment according to the present invention will be described. The configuration of the bronze evaluation apparatus in the second embodiment is the same as that of FIG. 1 shown in the first embodiment described above. Therefore, in the second embodiment, in particular, differences in operation from the first embodiment described above will be described.

  FIG. 5 is a flowchart showing the processing of the bronze amount calculation unit 16 in the second embodiment. It should be noted that the flow of processing until the measurement of the specular reflection light and the illumination photometry of the recording medium to be evaluated and the calculation of the tristimulus value XxYxZx and the tristimulus value XsYsZs of the regular reflection light of the recording medium to be evaluated (S501- (S503) is the same as the above-described processing (S301 to S303) of the first embodiment, and thus description thereof is omitted. Hereinafter, processing after each tristimulus value is calculated will be described.

  In step S504, the light intensity Yxr at a predetermined wavelength in the spectroscopic data of the regular reflection light of the recording medium to be evaluated input in step S501 is divided by the brightness of the regular reflection light, that is, Yx in the above formula (1). Normalize by In step S505, the light intensity Ysr at a predetermined wavelength in the illumination spectral data input in step S501 is normalized by dividing it by the luminance of the illumination light, that is, Ys in equation (3). Since the bronze phenomenon is related not to the brightness of the image of the illumination but to its color, the normalization performed in the above steps S504 and S505 cancels the difference in luminance, and the relative spectroscopic light of the recording medium to be evaluated and the relative spectrum of the illumination Distribution is calculated.

  In the second embodiment, the absolute value of the difference between the relative light amount of illumination at a predetermined wavelength corresponding to the color of the color material and the relative light amount of specularly reflected light of the recording medium to be evaluated is calculated, and this is calculated as the bronze amount B As a quantitative evaluation (S506).

  The calculation formula (6) by steps S504 to S506 described above is shown below.

Here, FIG. 6 shows a graph of an example of the relative spectral distribution of specular reflection light and illumination of the recording medium to be evaluated. According to the figure, it can be seen that, as compared with the relative spectral distribution of illumination, a large amount of absorption is observed around a wavelength of 540 nm, and thus bronze having a color close to magenta is generated.
Since the difference between the specularly reflected light color and the illumination color of the recording medium to be evaluated represents bronze, the total absolute value of the difference in relative light quantity in the visible wavelength region (380 nm to 780 nm in the present embodiment) is represented by bronze. It may be evaluated as a quantity.

  As described above, according to the second embodiment, based on the spectral data of the illumination light and the spectroscopic data of the specularly reflected light on the surface of the recording medium to be evaluated, the normalized relative light amount of the predetermined wavelength is obtained. The bronze phenomenon can be quantitatively evaluated by the difference value.

[Other embodiments]
Although the embodiments have been described in detail above, the present invention can take embodiments as, for example, a system, an apparatus, a method, a program, or a storage medium (recording medium). The present invention may be applied to a system composed of a single device or an apparatus composed of a single device.

  In the present invention, a software program (in the embodiment, a program corresponding to the flowchart shown in the drawing) that realizes the functions of the above-described embodiment is directly or remotely supplied to the system or apparatus, and the computer of the system or apparatus Is also achieved by reading and executing the supplied program code.

  Accordingly, since the functions of the present invention are implemented by computer, the program code installed in the computer also implements the present invention. In other words, the present invention includes a computer program itself for realizing the functional processing of the present invention.

  In that case, as long as it has the function of a program, it may be in the form of object code, a program executed by an interpreter, script data supplied to the OS, or the like.

  As a recording medium for supplying the program, for example, floppy (registered trademark) disk, hard disk, optical disk, magneto-optical disk, MO, CD-ROM, CD-R, CD-RW, magnetic tape, nonvolatile memory card , ROM, DVD (DVD-ROM, DVD-R).

  As another program supply method, a client computer browser is used to connect to an Internet homepage, and the computer program of the present invention itself or a compressed file including an automatic installation function is downloaded from the homepage to a recording medium such as a hard disk. Can also be supplied. It can also be realized by dividing the program code constituting the program of the present invention into a plurality of files and downloading each file from a different homepage. That is, a WWW server that allows a plurality of users to download a program file for realizing the functional processing of the present invention on a computer is also included in the present invention.

  In addition, the program of the present invention is encrypted, stored in a storage medium such as a CD-ROM, distributed to users, and key information for decryption is downloaded from a homepage via the Internet to users who have cleared predetermined conditions. It is also possible to execute the encrypted program by using the key information and install the program on a computer.

  In addition to the functions of the above-described embodiments being realized by the computer executing the read program, the OS running on the computer based on the instructions of the program is a part of the actual processing. Alternatively, the functions of the above-described embodiment can be realized by performing all of them and performing the processing.

  Furthermore, after the program read from the recording medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion board or The CPU or the like provided in the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are also realized by the processing.

It is a block diagram which shows the structure of the bronze evaluation apparatus in one Embodiment which concerns on this invention. It is a schematic diagram which shows the optical system of the bronze evaluation apparatus in this embodiment. It is a flowchart which shows the bronze amount calculation process in this embodiment. It is a figure which shows the spatial distribution of the reflected light quantity of the to-be-evaluated recording medium surface. 10 is a flowchart showing a bronze amount calculation process in the second embodiment. 6 is a graph showing a relative spectral distribution of specularly reflected light and illumination of an evaluation recording medium in a second embodiment.

Claims (10)

An evaluation apparatus for calculating a metal gloss evaluation value of a recording medium to be evaluated,
Specularly reflected light information acquisition means for measuring the specularly reflected light from the evaluation recording medium illuminated by the illuminating unit and acquiring information of the specularly reflected light;
Illumination light information acquisition means for acquiring information of the illumination light;
By obtaining the chroma of the specular reflection light based on said information of the illumination light and the specular reflected light information, a metallic luster calculating means for calculating a metallic luster evaluation value of the object to be evaluated recording medium,
The evaluation apparatus characterized by having. The evaluation apparatus according to claim 1, wherein the information on the illumination light and the information on the regular reflection light are spectral data . Evaluation apparatus according to claim 1, wherein the information and the information of the specular reflection light of the illumination light respectively the tristimulus values. The metallic gloss calculation means obtains an a * b * value of specular reflection light from the tristimulus value of the illumination light and the tristimulus value of the specular reflection light, and calculates the metal gloss evaluation value from the a * b * value. The evaluation device according to claim 3 , wherein the evaluation device calculates. The metallic luster calculation means, according to claim 1, characterized in that calculated from the tristimulus values XnYnZn of the illumination light and the tristimulus values XsYsZs of the specular reflected light, based on the metallic luster evaluation value B the following formula The evaluation device described.

  An evaluation apparatus for calculating a metal gloss evaluation value of a recording medium to be evaluated,
  Specularly reflected light information acquiring means for measuring specularly reflected light from the recording medium to be illuminated illuminated by the illuminating unit and acquiring spectral data of the specularly reflected light;
  Illumination light information acquisition means for acquiring spectral data of the illumination light;
  Normalizing means for normalizing the spectral data of the illumination light and the spectral data of the specularly reflected light;
  Metal gloss calculation means for calculating a metal gloss evaluation value in the recording medium to be evaluated using a difference between the spectral data of the normalized illumination light and the spectral data of the normalized specular reflection light;
The evaluation apparatus characterized by having.   The evaluation apparatus according to claim 6, wherein the metallic luster calculation unit calculates a sum of absolute values of differences in a visible wavelength region. An evaluation method in an evaluation apparatus for calculating a metal gloss evaluation value of a recording medium to be evaluated ,
Regular reflection light information acquisition means acquires the information of the regular reflection light obtained by measuring the regular reflection light from the illuminated recording medium to be illuminated;
Illumination light information acquisition means acquires the information of the illumination light illumination light information acquisition step,
Metallic luster calculating means, by obtaining the chroma of the specular reflection light on the basis of information of the illumination light and said positive reflected light information, a metallic luster calculating a metallic luster evaluation value of the evaluation target recording medium ,
The evaluation method characterized by having.   An evaluation method in an evaluation apparatus for calculating a metal gloss evaluation value of a recording medium to be evaluated,
  Regular reflection light information acquisition means, the regular reflection light information acquisition step for measuring the specular reflection light from the illuminated recording medium to obtain the spectral data of the regular reflection light,
  Illumination light information acquisition means, the illumination light information acquisition step of acquiring spectral data of the illumination light,
  A normalizing step, wherein the normalizing means normalizes the spectral data of the illumination light and the spectral data of the specularly reflected light;
  Metal gloss calculation means for calculating a metal gloss evaluation value in the recording medium to be evaluated using a difference between the normalized spectral data of the illumination light and the normalized specular data of the regular reflection light. Steps,
The evaluation method characterized by having. The program for functioning a computer as an evaluation apparatus of any one of Claim 1 to 7.

Images