JPH0953988A - Apparatus for measuring coloring of liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an apparatus for automatically measuring the coloring of liquid using a three-dimensional color space for measuring faint coloring of liquid (coloring of city water) or the difference of faint coloring and to employ the apparatus for calibration of precise measurement. SOLUTION: The apparatus for measuring the coloring of liquid comprises a light source 1, a flow cell 3 for containing a sample liquid, a spectroscopic section for sorting the wavelength of a light emitted from the light source 1 and passing through the flow cell 3 into a plurality of types, a photodetector 6 for detecting the light emitted from the light source 1 and passing through the flow cell 3 and spectroscopic section, and a signal processing section for processing the measurements as the extent of coloring and hue based on a signal from the photodetector 6. The apparatus is additionally provided with a calibration coloring filter 2 and a calibration processing section 7 so that the difference of faint coloring can be measured accurately.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in an apparatus for automatically measuring the coloring of a liquid, and more particularly to a coloring measurement / calibration mechanism of the apparatus.

[0002]

2. Description of the Related Art Conventionally, various liquids have been measured for coloring in various industrial fields. For example, a method using a convenient index called "chromaticity" is widely used for measuring the coloring of water in the water supply field. are doing. However, the conventional measuring device (for example, the device disclosed in Japanese Patent Laid-Open No. 4-9746) obtains "chromaticity" based on the absorbance of monochromatic light (390 nm), and catches one side of coloring of the liquid. However, there is a demand for an apparatus that can appropriately and easily measure coloration.

Japanese Patent Application No. 6-20 previously proposed by the applicant of the present application
In No. 6227, in order to solve the above situation, tristimulus value data corresponding to the relative spectral sensitivity characteristic by the CIE XYZ color system color matching function defined by the International Commission on Illumination is obtained,
By introducing the concepts of degree of coloring and hue on the three-dimensional color space constructed based on them, we showed that it is possible to measure coloration equivalent to visual observation.

On the other hand, when measuring the color of a liquid, in order to correct the fluctuation of the light amount of the light source, which is a factor of fluctuation of the measurement, and the influence of dirt in the measurement environment, correction by reference light measurement that does not pass through the sample liquid and non-coloring It was customary to introduce a calibration mechanism for the non-colored point (zero point) by measuring the sample liquid of. However, in the case of measuring an extremely minute color (coloring of tap water, etc.) or a very small color difference, there is a problem that accurate measurement is difficult even if the above-described variation correction is performed.
The cause of this is that in conventional correction and calibration, the characteristics of the light-receiving element change when the spectrum of the measurement light changes differently between the measurement light path and the reference light path, when the measurement light path shows spectral dependence and is deformed. If there is a change in the spectrum intensity shape in the entire measurement system, such as in the case of occurrence, it is impossible to correct the measurement condition variation.

[0005]

An object of the present invention is to provide a liquid sample as a sample having a calibration mechanism corresponding to the liquid color measuring function using the three-dimensional color space in Japanese Patent Application No. 6-206227. It is an object of the present invention to solve the conventional problems by providing an apparatus capable of accurately measuring the minute coloring and the slight difference in coloring.

[0006]

In order to solve the above-mentioned problems, in a liquid coloring measuring apparatus according to the present invention, a light source, a flow cell containing a liquid to be a sample, and a wavelength of light emitted from the light source and transmitted through the flow cell are set to a plurality of wavelengths. Equipped with a spectroscopic unit that selects the type, a photodetector that detects light from a light source that passes through the flow cell and the spectroscopic unit, and a signal processing unit that arithmetically outputs the measurement value as the coloring degree and hue based on the signal from the photodetector. It is possible to accurately measure a very slight difference in color by adding a color filter for calibration and an arithmetic unit for performing a calibration operation to the liquid color measuring device.

The principle of coloring measurement and the principle of calibration will be shown below using the configuration diagram (FIG. 1) and the three-dimensional color space diagram (FIGS. 2 and 3) of the present invention. FIG. 1 shows the measurement principle of the present invention. The light from the light source 1 is passed through the spectral optical filter 8,
To correspond to the CIE XYZ color system color matching function, red,
Creates green and blue light. These lights are attenuated as they pass through the sample liquid in the flow cell 3. The light amount of the light that has passed through the uncolored liquid is detected by the photodetector 6 in advance, and is stored as 100% in the calculation unit 7. Then, the amount of light transmitted through the sample liquid is measured, the transmittance of the sample liquid with respect to the amount of transmitted light of the non-colored liquid is calculated by the calculation unit, and the output X,
Get Y and Z. From these outputs, x according to equation (1),
If y and w are calculated, coloring can be evaluated as one point (measurement point S) on the three-dimensional color space shown in FIG.

[0008]

[Equation 1]

The xy plane of the three-dimensional color space of FIG.
This is called an E1931xy chromaticity diagram, and the w axis represents the degree of decrease in the brightness of transmitted light. Where X, Y,
When the values of Z are equal, x = y = 1/3 = 0.333, and even if the condition is satisfied, the point where the degree of decrease in brightness is 0 (w = 0, that is, Y = 1) is excluded. The coloring point (W) is used.

The measurement point is represented on the three-dimensional color space of FIG. 2 by point S, and the point P is projected on the xy plane. In the above-mentioned Japanese Patent Application No. 6-206227, the applicant of the present application sets the coloring degree of the sample liquid to a non-colored point W in the three-dimensional color space.
And the measurement point S, the hue of the sample water is determined from the color of the area including the point P on the chromaticity diagram on the xy plane.

FIG. 3 shows the principle of calibration. The conventional measurement of the uncolored point is based on the reference point W in the three-dimensional color space.
Equivalent to calibrating the points. Therefore, by introducing the method of the present invention and inserting the coloring filter 2 for calibration which grasps coloring (wavelength / transmittance characteristics are known) into the optical path,
One more reference point N can be calibrated in the three-dimensional space.
This means calibrating the reference axis (Vf) in the three-dimensional space, which has been changed by various factors as described above, to the correct position (Vn). Therefore, if this mechanism is added, the space can be correctly corrected for variations, and coloring measurement can be accurately performed.

Even in the conventional liquid color measuring device, there has been established a calibration method for one-dimensional characteristic measurement (for example, chromaticity standard solution for calibrating chromaticity measurement of tap water).
The present invention is epoch-making as a mechanism capable of accurately and simply calibrating a color measurement using a three-dimensional color space.

[0013]

1 is a block diagram of the first embodiment of the present invention. The effect does not change wherever the calibration color filter 2 is arranged between the light source 1 and the photodetector 6.
In the case where liquid coloring is continuously measured, the calibration coloring filter 2 is periodically inserted into the optical path to correct fluctuations, whereby accurate measurement can be continued. At the time of measurement, remove the color filter for calibration from the optical path.

FIG. 3 shows a commercially available N as a color filter for calibration.
This is an example using a D filter. The ND filter is a filter that shows a constant attenuation rate over the entire predetermined wavelength region, and by inserting this into the optical path, the light amount is reduced without changing the balance of the spectrum of light (without changing the color). be able to. Therefore, if a color filter for calibration is inserted into the optical path while the flow cell is filled with a non-colored liquid, the calibration reference point will be on the achromatic axis of transparent → gray → black, and the reference axis will be as shown in Fig. 3. Is calibrated to.

An arithmetic expression when the ND filter is used for calibration is shown below. Here, the transmitted light amount of the uncolored liquid is Bl,
The amount of transmitted light when an ND filter is inserted there is Nd,
Let Sp be the actual amount of transmitted light of the sample liquid, A be the transmittance of the ND filter, and N be the transmittance of the actual sample liquid. If there is no calibration,

[0016]

[Equation 2]

If there is calibration by the ND filter,

[0018]

(Equation 3)

[0019]

(Equation 4)

Therefore, the color measurement can be performed without being affected by the offset and the fluctuation of the span.

[0021]

With the liquid coloring measuring apparatus of the present invention, it is possible to grasp the degree of coloring, for example, to show the same transmittance over the entire measurement wavelength range (wavelength-transmittance characteristics are known. ) By using a color filter, a new proofreading function was established that utilizes the above-mentioned three-dimensional color space and introduces the concepts of coloring degree and hue. This makes it possible to measure extremely minute colors (coloring of tap water, etc.) and even very small differences in color,
It is possible to correct different changes in the measurement light spectrum between the measurement light path and the reference light path, stains and deformations of the measurement light path exhibiting spectral dependence, and changes in the characteristics of the light-receiving element, thus enabling accurate measurement.

4 (a) and 4 (b), in order to investigate the above-mentioned effects, four kinds of standard solutions which are the criteria for coloring evaluation were prepared, and the solutions were diluted in 3 to 4 steps to a concentration near the visual limit. It is the experiment example which plotted the projection point on the xy plane chromaticity diagram of the measurement result which appears in a three-dimensional color space using the sample liquid. In FIG. 4 (a) before the introduction of the present invention, when the dilution degree is increased with the same type of sample liquid, there is a trace of a jagged path. This is because the color areas are interlaced, and there is a portion where the area cannot be divided for color discrimination. On the other hand, in FIG. 4 (b) after the introduction of the present invention, when the dilution degree is increased with the same type of sample solution, the measured value becomes a straight line toward the uncolored point (x = y = 0.333). Therefore, it can be seen that the resolution of the hue discrimination of each type of sample liquid is remarkably improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 shows an xy chromaticity diagram (a) is a three-dimensional color space diagram and an explanatory diagram of the coloring degree and hue using it, and (b) is xy
Illustration of chromaticity diagram and hue judgment

FIG. 3 is a conceptual diagram of calibration performed in a three-dimensional color space when an ND filter is used as a calibration color filter.

FIG. 4 is a chromaticity diagram showing an example in which a color measurement function is improved when an ND filter is used as a calibration color filter.
(a) is the chromaticity diagram before the invention is introduced, and (b) is the chromaticity diagram after the invention is introduced.

[Explanation of reference numerals] 1 light source 2 calibration filter 3 flow cell 4a optical window 4b optical window 5a inflow valve 5b outflow valve 6 photodetector 7 arithmetic unit 8 spectroscopic optical filter

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Hiroshi Tada 1-1, Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Fuji Electric Co., Ltd. No. 1 inside Fuji Electric Co., Ltd.

Claims (2)

[Claims] 1. A light source, a flow cell containing a liquid to be a sample, a spectroscopic unit capable of selecting a plurality of types of wavelengths of light emitted from the light source and passing through the flow cell, and light from the light source passing through the flow cell and the spectroscopic unit is detected. A photo-detector, a liquid color-measuring device using a three-dimensional color space, characterized by comprising a signal processing unit for calculating and outputting a measured value as a coloring degree based on a signal from the photo-detector. A coloring measurement apparatus for liquids, comprising: a coloring filter for use with a liquid; and a calculation unit for performing a calibration calculation. 2. A liquid color measuring apparatus according to claim 1, further comprising a signal processing section for calculating and outputting a measured value as a hue.