JPH06241903A - Colorimeter and compensation thereof - Google Patents

Abstract

PURPOSE:To compensate spectral characteristics at the time of the measurement of a sample over the whole of a measuring wavelength region using the quantity of light at one wavelength point measured at a time of spectral measurement by a compensation sensor. CONSTITUTION:When the spectral reflectance of a sample 12 to be measured is calculated on the basis of the spectral transmittance of a standard white plate, an auxiliary white plate 36 is prepared and a xenon lamp 14 is allowed to emit light and the reflected light from the auxiliary white plate 36 is guided to a sensor array 22 through a mirror 18, a condensing lens 20, a slit 21 and a concaved grating 16. The output of the sensor array 22 is measured to calculate spectral characteristics and the output from the sensor array 22 is measured with respect to the sample 12 to be measured in the same way to calculate spectral characteristics and, at the same time, the quantity of light is measured with respect to the same emitted light by a cumpensation sensor 24. On the basis of this quantity of light, the spectral characteristic value of the auxiliary white plate 36 is corrected and, on the basis of the spectral characteristic value after correction, the spectral characteristic value of the sample 12 to be measured is corrected at every wavelength.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a colorimeter and its compensating method, and in particular, the spectral reflectance of a measurement sample is obtained based on the known spectral reflectance of a standard sample, and the color reflectance is calculated using the spectral reflectance. The present invention relates to a colorimeter and a compensation method suitable for applying the colorimeter.

[0002]

2. Description of the Related Art Conventionally, for example, a measurement sample is irradiated with flash light from a light source such as a xenon lamp, and the reflected light or transmitted light is dispersed and guided to a light receiving sensor such as a silicon diode array, and the received light is photoelectrically converted. There is known a colorimeter which produces a sensor output and performs color calculation processing based on the sensor output to obtain a measurement value.

In this colorimeter, for example, a calibration plate such as a standard white plate (standard sample) is measured, the calibration plate is set to a reference value, and the sample measurement value is calculated based on the reference value. ing.

In the above colorimeter, the spectral waveform of the irradiation light when the light source is irradiated changes depending on the temperature of the light source. Therefore, the spectral waveform of the light source light is measured when measuring the standard sample and when measuring the measurement sample. Can be different.

Therefore, when the measurement sample is measured, it is necessary to make a correction to match the conditions under which the standard sample was measured. As the correction method, a compensation sensor including a sensor array having the same function as the sample sensor is provided at a position different from the sample setting portion (for example, a 37-element sensor in which both the sample sensor and the compensation sensor are arranged at 10 nm intervals). When the measurement sample is set, the spectroscopic measurement of the light source light is performed at the same time with the above compensation sensor, and the measurement is performed based on this spectroscopic waveform and the spectroscopic waveform of the light source light when the standard sample is measured. A method is known in which a spectral waveform of reflected light or the like obtained by actually measuring a sample is corrected for each wavelength.

Further, as a correction method used in a conventional colorimeter, a compensation sensor measures each one point of the long wavelength and the short wavelength in the measurement wavelength range, and the change of the light quantity at each point of the long wavelength and the short wavelength is measured. A method is also known in which the measurement sample is simultaneously measured every time it is measured, the light amount values at the two wavelength points are connected by a straight line, and the light amount for the wavelength between them is interpolated and corrected.

[0007]

However, in the case of a colorimeter using a sensor array having the same number of light receiving elements as the sample sensor as the compensation sensor, even if the functions of the sensor array are completely the same, Since the sample measurement position and the installation position of the compensation sensor are spatially different, the irradiation light reaching each position is not always the same. Therefore, there is a problem that the spectral waveform measured on the measurement sample cannot always be compensated over the entire wavelength based on the result of measuring the light source light with the compensation sensor.

Further, in the case of two-point compensation in which linear interpolation is performed based on the light quantity values measured at one point of long wavelength and one point of short wavelength, the two points are used.
If the spectral waveform between two wavelengths changes differently from a linear change, compensation cannot be performed, resulting in poor accuracy. In fact, when the same sample is compared and measured at different times, a large color difference may be exhibited.

The present invention has been made to solve the above-mentioned conventional problems, and when measuring the spectral reflectance of a measurement sample, the amount of light measured at one wavelength point by a compensation sensor is used for measurement. It is an object of the present invention to provide a colorimeter capable of compensating the irradiation light of (1) over the entire measurement wavelength range, and as a result, capable of accurately obtaining the spectral reflectance, and a compensation method thereof.

[0010]

The present invention is directed to a light source for irradiating a sample with flash light, a spectroscopic means for separating reflected light when the sample is irradiated with flash light, and a spectroscopic means Using a colorimeter equipped with a sample sensor that photoelectrically converts the reflected light for each wavelength and a compensation sensor that measures the amount of flash light, the spectral reflectance based on the output from the sample sensor during irradiation In the compensating method of the colorimeter when calculating with the spectral reflectance of the standard sample as a reference, the output from the sample sensor for the auxiliary standard sample is measured to obtain its spectral characteristics, and the sample sensor for the measurement sample is also measured. At the same time as measuring the output from the device to obtain its spectral characteristics, measure the light intensity of the irradiation light with a compensation sensor, correct the spectral characteristics of the auxiliary standard sample based on the measured light intensity, and The value of the spectral characteristics obtained, for each wavelength, by correcting on the basis of the corrected spectral characteristic values of the auxiliary reference sample after is obtained by achieving the above objects.

Further, according to the present invention, a light source for irradiating a sample with flash light, a spectroscopic means for separating reflected light when the sample is irradiated with flash light, and a reflected light dispersed by the spectroscopic means are provided. In a colorimeter equipped with a sample sensor that performs photoelectric conversion for each wavelength and a compensation sensor that measures the amount of flash light, the auxiliary standard sample for obtaining the spectral characteristics for correction is substantially the same as the sample setting position. The above-mentioned problem is similarly achieved by adopting a configuration in which auxiliary standard sample installation means installed in the same position is provided.

[0012]

As a result of various studies, the present inventor has found that when measuring a sample with a colorimeter, the irradiation light amount changes with each measurement, but the spectral waveform of the irradiation light itself does not change abruptly and continuously. It was found that there is almost no change when measuring.

The present invention has been made based on the above findings,
When calculating the spectral reflectance of the measurement sample based on the spectral reflectance of the standard sample, obtain the spectral characteristics of the auxiliary standard sample before measuring the measurement sample, and then obtain the spectral characteristics of the measurement sample. The value of the spectral characteristic of the measurement sample is corrected by correcting the value of the spectral characteristic of the auxiliary standard sample based on the amount of irradiation light measured at the same time, and using the corrected spectral characteristic value of the auxiliary standard sample. Since the wavelength is corrected for each wavelength, the spectral waveform of the irradiation light is substantially the same when performing continuous measurement. Therefore, the irradiation light amount is measured for one wavelength point with a compensation sensor, and the result is Therefore, it is possible to compensate the spectral characteristics over the entire measurement wavelength range only by correcting the light amount. Therefore, for example, the stimulus values X, Y, Z in the XYZ color system can be calculated with high accuracy.

Further, in the present invention, since the colorimeter is provided with auxiliary standard sample setting means for setting the above-mentioned auxiliary standard sample at substantially the same position as the sample setting position, by using the colorimeter, It is possible to easily and surely perform the compensation of the above-mentioned spectral characteristics.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is an explanatory diagram showing a schematic configuration of a colorimeter of one embodiment according to the present invention.

The colorimeter 10 of this embodiment comprises a xenon lamp (light source) 14 for irradiating a measurement sample 12 with flash light.
A concave grating (spectral means) 16 for splitting the reflected light when the measurement sample 12 is irradiated by the xenon lamp 14, and a mirror for guiding the reflected light from the measurement sample 12 to the concave grating 16. 18, an optical system including a condenser lens 20, a slit 21 and the like, a sensor array (sample sensor) 22 that receives the reflected light (spectral reflected light) dispersed by the concave grating 16;
Compensation sensor 24 for measuring the amount of irradiation light at the time of measurement
It has and.

The sensor array 22 has sensors (light receiving elements) arranged at positions corresponding to respective wavelengths of the spectral light. For example, if the measurement range is 400 to 700 nm, the sensors are arranged every 20 nm. In total, 16 sensors can be used.

The colorimeter 10 is a xenon lamp 1.
The measuring sample 12 and the compensation sensor 24 are provided with an integrating sphere 26 for diffusing the flash light from
Are arranged so as to face the windows 26A and 26B formed in the integrating sphere 26, and the measurement sample 12 is detachable.

Further, the integrating sphere 26 is provided with a window 26C for extracting the vertically reflected light from the measurement sample 12 to an optical system (mirror 18 etc.), and the light from the xenon lamp 14 is measured. A baffle 28 is provided to prevent direct irradiation of 12 and the compensation sensor 24.

Further, in the colorimeter 10, the window 26A for disposing the measurement sample 12 can be opened and closed by the shutter 30, and the shutter 30 is opened and closed by the motor 34 connected through the speed reduction mechanism 32. It is supposed to be done. Then, an auxiliary white plate (auxiliary standard sample) 36 made of barium sulfate applied by coating is attached to the inner surface of the shutter 32 (the side facing the inside of the integrating sphere 26), and the shutter 30 is attached. When closed, the auxiliary white plate 36 is installed at substantially the same position where the measurement sample 12 is installed.

Next, the operation of this embodiment will be described.

First, the xenon lamp 14 is caused to emit light with the shutter 30 kept closed. At this time, the auxiliary white plate 36 provided inside the shutter 30 is illuminated, and the reflected light is guided to the condenser lens 22 via the mirror 18 and narrowed down to the slit 21 by the condenser lens 20. After that, the light is incident on the concave grating 16 with an appropriate opening angle.

When reflected light is incident on the concave grating 16, the reflected light is spectrally dispersed, is incident on the sensor array 22 as spectral light, is photoelectrically converted for each wavelength, and is output. At this time, the sensor output R _{0, f} (f: wavelength) of each wavelength is measured. For example, as described above, the sensor array 2
If 2 consists of 16 sensors, then 2
16 pieces of measurement data R _{0, f} are obtained for wavelengths every 0 nm.

Next, at the sample setting position outside the window 26A,
The standard white plate (standard sample) 38 is installed, the motor 34 is driven, and the shutter 30 is moved through the speed reduction mechanism 32 from the measurement position, that is, the window 26A, and then the same as the case of the auxiliary white plate 36. The xenon lamp 14 is caused to emit light, and the spectral reflection light of the standard white plate 38 is transmitted to the sensor array 2
2 and the sensor array 2 for each wavelength at this time
The output of 2 is S _{0, f} .

Simultaneously with this measurement, the compensation sensor 24 receives light of a specific wavelength for the same light emission and measures the amount of light, and the sensor output by the compensation sensor 24 is R ₀ .
The compensation sensor 24 can capture only the light that has passed through the interference filter 24A so as to receive the light of one specific wavelength. Then, this interference filter 2
4A is matched with one specific wavelength of the wavelengths captured by the sensor array 22.

As the specific one wavelength, a wavelength point at which the spectral waveform of the light reaching at the measurement position and the position of the compensation sensor 24, that is, the windows 26A and 26B does not change even when the irradiation light amount changes at each measurement is selected. It For example, if the specific one wavelength is now 500 nm, the interference filter 24A causes the compensation sensor 24 to capture only light of 500 nm in order to match the array output R _0,500 for that wavelength.

After performing the above measurement, the standard white plate 38
The calibration coefficient Kf is calculated by the following equation (1). The calibration coefficient Kf is a coefficient for calibrating the value of the spectral characteristic of the reflected light by the auxiliary white plate 36 with the value of the spectral characteristic of the reflected light by the standard white plate 38. In the following description, it is assumed that the specific one wavelength (compensation point) is 500 nm.

Kf = Wf / {S _{0, f} / (R _{0, f} × R ₀ / R _0,500 )} (1)

Here, Wf is the wavelength range f = 400 to 70
The reflectance of the standard white plate 38 for each wavelength at 0 nm is a known value.

In the above equation (1), (R _{0, f} × R ₀ / R
_0,500 ) is an auxiliary white plate based on the spectral characteristics of the light reflected by the auxiliary white plate 36, based on the ratio of the irradiation light amount when the auxiliary white plate 36 is measured to the irradiation light amount when the standard white plate 38 is measured. The spectral characteristic of the reflected light by 36 is equivalent to the correction of the change in the irradiation light amount over the entire measurement wavelength range.

Then, the standard white plate 38 is removed from the measurement position, the measurement sample 12 is placed at the sample setting position (the same position as the standard white plate 38), and each auxiliary white plate 36 is operated by the same operation as described above. The output R _{1, f} of the sensor array 22 for each wavelength is measured, and then the output S _{1, f} of the same sensor array 22 for each wavelength by the measurement sample 12 is measured, and at the same time, the specific wavelength by the compensation sensor 24 for the same light emission is measured. The sensor output R ₁ at (500 nm) is measured.

That is, R _{0, f} is a measurement value (sensor output) of the reflected light by the auxiliary white plate (barium sulfate) 36 attached to the shutter 30 measured before measuring the standard white plate 38. On the other hand, this R _{1, f} is the measurement sample 12
Is a measurement value (sensor output) of the reflected light by the auxiliary white plate 36 measured immediately before measurement.

By the above respective operations, R _{1, f} and S measured
_{By using 1, f} and R ₁ and the calibration coefficient Kf obtained by the equation (1), the reflectance S ′ _{1, f of} each wavelength corrected for the measurement sample 12 is calculated by the following equation (2). You can ask. Note that R _1,500 is the sensor array 2 obtained by measuring the auxiliary white plate 36 immediately before measuring the measurement sample 12.
With the output of 500 nm according to 2, R in the above formula (1)
Equivalent to _0,500 .

S ′ _{1, f} = Kf {S _{1, f} / (R _{1, f} × R ₁ / R _1,500 )} (2)

With respect to the measurement sample, the corrected reflectance for each wavelength obtained by the equation (2) is used for the calculation of the color system, and, for example, the stimulus values X, Y and Z in the XYZ color system are used. calculate.

In this embodiment described in detail above, immediately before the spectral characteristics of the standard white plate 38 are measured, the spectral characteristics of the reflected light when the flash light of the xenon lamp 14 is applied to the auxiliary white plate 36 is measured. Then, the spectral reflection light of the standard white plate 38 is measured, and at the same time, the change of the light amount is captured by the compensation sensor 24 for the same light emission. A correction is performed, and a calibration coefficient Kf for associating the spectral characteristic of the auxiliary white plate 36 with the spectral reflectance of the standard white plate 38 is obtained from the equation (1).

Next, before measuring the measurement sample 12, the flash light of the xenon lamp 14 is similarly supplied to the auxiliary white plate 3.
By measuring and storing the spectral characteristics of the reflected light when irradiating the sample 6 and measuring the spectral reflected light of the measurement sample 12 and simultaneously capturing the change in the light amount with the compensation sensor for the same light emission, the auxiliary white plate 36 is used. The spectral characteristic of the reflected light can be corrected by the amount of change in the light amount, and the spectral reflectance of the measurement sample 12 can be corrected and calculated by the equation (2).
Therefore, the spectral characteristic of the reflected light can be compensated with one measurement value by the compensation sensor 24 over the entire measurement wavelength range, and the spectral reflectance of the measurement sample 12 can be obtained with high accuracy. .

Generally, the light quantity of the xenon lamp 14 changes with each emission, but the spectral characteristics gradually change. Therefore, when the auxiliary white plate 36 and the standard white plate 38 or the measurement sample 12 are continuously measured. , The above compensation method is extremely effective. As the light receiving wavelength of the compensation sensor for measuring the change in the light amount at that time, a wavelength point where the spectral waveform does not change between the measurement position and the installation position of the compensation sensor is selected as described above.

Although the present invention has been specifically described above, the present invention is not limited to the above-mentioned embodiments, and various modifications can be made without departing from the scope of the invention.

For example, in the above-described embodiment, the change in the amount of light is calculated from one of the measured values of the auxiliary white plate 36 and the measured value of the compensation sensor 24, but the invention is not limited to this, and the auxiliary white plate 36 is measured. At the same time, the compensation sensor 24 measures the light amount of the specific wavelength, and the measured value (sensor output) R ′ ₀
Alternatively, the change in light amount may be captured by the measurement value R ₀ of the compensation sensor 24 at the time of measuring the sample, and the calibration coefficient Kf may be calculated by the following equation (3) instead of the equation (1). This is the measurement sample 1
The same applies to 2, and in this case, R in (2) above is used.
_1,500, may be changed to ₁ 'R corresponds to _0' to R.

Kf = Wf / {S _{0, f} / (R _{0, f} × R ₀ / R ′ ₀ )} (3)

Further, in the above embodiment, the standard white plate or the auxiliary white plate was measured before the measurement of the measurement sample, but the order of measurement may be reversed.

In the above embodiment, the case where the auxiliary white plate 36 is attached to the back surface of the shutter 30 has been shown, but the auxiliary white plate 36 may be installed at the measurement position by other means. The auxiliary white plate is not limited to barium sulfate.

[0045]

As described above, according to the present invention,
When measuring the spectral reflectance of the measurement sample, by using the light quantity measured at one wavelength point by the compensation sensor, the irradiation light at the time of measurement can be compensated over the entire measurement wavelength range. Therefore, it is possible to accurately obtain the spectral reflectance of the measurement sample and to use the value to perform accurate color calculation.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of a colorimeter according to an embodiment of the present invention.

[Explanation of symbols]

 10 ... Colorimeter 12 ... Measurement sample 14 ... Xenon lamp 16 ... Concave grating 18 ... Mirror 20 ... Condensing lens 21 ... Slit 22 ... Sensor array 24 ... Compensation sensor 30 ... Shutter 36 ... Auxiliary white plate 38 ... Standard white plate

Claims (2)

[Claims] 1. A light source that irradiates a sample with flash light, a spectroscopic unit that disperses reflected light when the sample irradiates the sample with flash light, and a reflected light dispersed by the spectroscopic unit is photoelectrically converted for each wavelength. Using a colorimeter equipped with a sample sensor for conversion and a compensating sensor for measuring the amount of flash light, the spectral reflectance of the standard sample is determined based on the output from the sample sensor during irradiation. In the method of compensating the colorimeter when calculating with reference to, the output from the sample sensor for the auxiliary standard sample is measured to obtain its spectral characteristics, and the output from the sample sensor for the measurement sample is measured. At the same time as obtaining the spectral characteristics, the light amount of the irradiation light is measured by the compensation sensor, the spectral characteristic values of the auxiliary standard sample are corrected based on the measured light intensity, and the spectral characteristic values obtained for the measurement sample are measured. Is compensated for each wavelength based on the spectral characteristic value of the supplemental standard sample after compensation. 2. A light source for irradiating a sample with flash light, a spectroscopic means for separating reflected light when the sample is irradiated with flash light, and a reflected light dispersed by the spectroscopic means for each wavelength. In a colorimeter equipped with a sample sensor for conversion and a compensating sensor for measuring the amount of flash light, an auxiliary standard sample for obtaining spectral characteristics for correction is installed at the same position as the sample setting position. A colorimeter characterized in that it is provided with an auxiliary standard sample setting means for performing.