JPH0660846B2 - Photoelectric colorimeter with spectral sensitivity correction function - Google Patents

Description

TECHNICAL FIELD The present invention relates to a tristimulus value type photoelectric colorimeter with a spectral sensitivity correction function.

<Prior Art> Conventionally, a photoelectric colorimeter (tristimulus colorimeter) is a color matching function [
(Λ), (λ), (λ)] has a spectral sensitivity similar to that.

<Problems to be Solved by the Invention> However, the spectral sensitivity of this tristimulus value type photoelectric colorimeter is
Since it does not completely match the color matching function, there is an error in the measured value, and because there is an error in the spectral sensitivity between the devices such as the optical filters, there is a machine difference in the measured value. Therefore, when absolute value accuracy is required and measurement with few machine differences is required, it is common sense to use a spectroscopic colorimeter that can theoretically match spectral sensitivity to the color matching function in theory. There is.

However, the spectroscopic colorimeter is large and expensive.

Therefore, an object of the present invention is to minimize the above-mentioned error and machine difference in a tristimulus value type photoelectric colorimeter characterized by being inexpensive and compact.

<Means for Solving Problems> A photoelectric colorimeter with a spectral sensitivity correction function of the present invention decomposes light from a sample irradiated by a light source into basic color components and photoelectrically converts the light of the basic color components. The photoelectric conversion unit and the calibration sample are measured in advance, and the calibration constant for the calibration sample is calculated based on the basic color component information of the light from the calibration sample output from the photoelectric conversion unit. A calculating means, a storage means for storing a plurality of calibration constants calculated by measuring a plurality of calibration samples, a measurement value of the measurement sample when measuring the measurement sample, and a storage value previously stored in the storage means. Based on the calibration constants determined by the determining means and the determining means for determining the optimum calibration constant based on the plurality of calibration constants,
It is characterized by comprising a correction means for correcting the measurement value of the measurement sample, and a data processing section having the correction means.

<Operation> The calibration constants of the plurality of calibration samples calculated by the calibration constant calculation means are stored in the storage means. On the other hand, the calibration constant determining means determines the optimum calibration constant from the memory means based on, for example, the distance between the chromaticity points in accordance with the measured value of the measurement sample detected by the photoelectric conversion unit. The correction means corrects the measured value of the sample with the optimum calibration constant determined by the calibration constant determination means.

As a result, the absolute value measurement error caused by the spectral sensitivity error and the machine difference between the measured values due to the variation in the spectral sensitivity between the devices are minimized.

<Example> Hereinafter, the present invention will be described in detail with reference to illustrated examples.

FIG. 1 is a block diagram of this embodiment, FIG. 2 is a timing chart of a photoelectric conversion unit, and FIG. 3 is a flow chart showing acquisition of tristimulus value data of a sample from the photoelectric conversion unit.

As shown in FIG. 1, this photoelectric colorimeter with a spectral sensitivity correction function includes a photoelectric conversion unit (100) and a data processing unit (200).
The photoelectric conversion part (100) has photodiodes (P ₁ to ₆ ) which are _six photosensors, and among them, 3 photodiodes (P ₁ to ₃ ) are used for measuring the sample (1) and the remaining 3 The two photodiodes (P ₄ to ₆ ) are used for the measurement of the light source (2), the fluctuation of the light source (2) is canceled by calculating (measurement value of sample) / (measurement value of light source), and It enables measurement in a certain state. The light from the sample (1) or the light source (2) is decomposed into the basic color components by the optical filters (F ₁ to ₆ ), and the basic color components are detected by the photodiodes (P ₁ to ₆ ), and the respective photoelectric conversions are performed. The circuit (E ₁ to ₆ ) converts it to an electric signal, amplifies it, and outputs the electric quantity according to the optical signal.
(G ₁ to ₆ ) for each sample and hold circuit (H ₁ to
₆ ), and further through the gates (G ₇ to ₁₂ ) A /
It is sent to the D conversion circuit (3) and taken in as a digital value by the central processing unit (CPU) 5 which is the control unit of the data processing unit (200).

In this way, the CPU (5) calculates the tristimulus value data (X, Y, Z) of the sample (1) in a constant state in which the fluctuation of the light source (2) is canceled by the steps in FIG. through S ₁ ~ _12, S _14, is performed in step S _13. A in step S ₁₃
(1), A (2), ..., A (6) are photodiodes P ₁ , P ₂ ,
..., corresponding to the output of P ₆ . The photodiode P ₁ ,
When capturing the signals from P ₂ , ..., P ₆ , the gates (G ₁ ~
₁₂ ) opens at the timing shown in FIG.

On the other hand, in the data processing unit (200), the above-mentioned CPU (5) for performing control and arithmetic processing, a read-only memory (ROM) (6) for storing programs such as system control and color conversion, and color information A random access memory (RAM) (7) which is a memory means for storing the like, a clock (8), an I / O port (9),
There is a display unit (10) such as a liquid crystal display device or a printer for displaying the result obtained by the measurement, and a keyboard (12) for operating the photoelectric colorimeter. Furthermore, a warning unit (11) and a decoder (13) are provided.

Before using this photoelectric colorimeter, it is necessary to calibrate it according to the flowchart shown in FIG. This photoelectric colorimeter has 10 calibration channels from 0 to 9, and can calibrate 10 kinds of calibration reference samples. In this photoelectric colorimeter, it is necessary to input channel 0 first, and if channel 0 is calibrated, then the channels can be selected arbitrarily. In this calibration channel 0, common error factors due to temperature etc. are removed.

Enter the calibration mode by pressing the calibration key on the keyboard (12). Calibration correction channel 0 in step S ₂₁ it is determined whether being performed, the process proceeds to step S ₂₂ if no calibration channel 0 is performed automatically becomes the calibration channel zero. Providing a calibration reference sample for calibration channel 0, the tristimulus values of the calibration reference sample in step S ₂₃ (X _0,
Input (Y ₀ , Z ₀ ) with the ten keys on the keyboard (12). Then, a calibration reference sample proceeds to step S ₂₄ measured by operating the measurement key, obtain the tristimulus values (X, Y, Z). Step S ₂₅
Then, the calibration constants (α, β, γ) are obtained by the following formula, and the tristimulus values (X ₀ , Y ₀ , Z ₀ ) of the calibration reference sample are used in step S ₂₆ to obtain
L ^* _a ^* _b ^* performs color space conversion to the coordinate system, the converted result ^{_{L 0 *, a0 *, b0}} * ungated, the results obtained are stored in the memory area at step S _28.

Note that L ₀ ^* is lightness information.

If it is determined that the finished calibration correction channel 0 in the step S _21, the correction channel in step S ₂₉ 1
Select arbitrarily from ~ 9. Select the selected calibration channel as i (= 1
~ 9). Providing a calibration reference sample for calibration channel i, and inputs tristimulus values of the sample at step S ₃₀ the (Xi, Yi, Zi) in the numeric keypad. Then, the process proceeds to S _31, the calibration standard samples was measured by the measuring key, obtain the tristimulus values (X, Y, Z). Then
Proceeding to step S ₃₂ , this is corrected by the following equation using the calibration constants αmemo (0), βmemo (0), γmemo (0) of the calibration channel 0.

Xm = X ・ αmemo (0) Ym = Y ・ βmemo (0) Zm = Z ・ γmemo (0) Using the calculated (Xm, Ym, Zm), the calibration constants (α, β, γ) are calculated by the following formula. Ask for.

Subsequently, the procedure proceeds to step S _34, using the tristimulus values of the calibration standard samples for calibration channel i (Xi, Yi, Zi) , L * a * b *
Color space conversion is performed to the coordinate system, and the conversion result is (L _i ^* ,
_ai ^* , _bi ^* ) and store this in the memory area.

Subsequently, the procedure proceeds to step S _35, S _36, calibration constants (alpha,
(β, γ) is stored in the calibration constant memory area, and the chromaticity points ( _ai ^* , _bi ^* ) of the calibration constant are stored in the memory.

Step S ₂₁ to S ₃₅ shown in this FIG. 4 is an example of a calibration constant calculating means.

Next, the measurement of the actual sample is performed according to the flowchart shown in FIG.

In step S ₄₁ , the measurement sample is operated by operating the measurement key to obtain the tristimulus values (X, Y, Z) of the sample. Step S
Recall the calibration data of the calibration channel 0 at _42, corrects the measured data by the following equation proceeds to step S _43.

α ₀ = αmemo (0), β ₀ = βmemo (0), γ ₀ = γmemo (0) Xm = α ₀ · X, Ym = β ₀ · Y, Zm = γ ₀ · Z Next, in step S ₄₄ Determine whether it is in automatic calibration mode.

(I) In the case of automatic calibration mode The measurement data (X
m, and converts Ym, Zm) at step S ₄₅ to L ^* _a ^* _b ^* coordinate system, the converted result ^{_{(L m *, am *,}} bm *) to. Then step S
Proceed to _47, S _48, the chromaticity point of the calibration sample correction channel ^{_{0~9 (a * memo (J)}} , b * memo and (J), the chromaticity point of the measurement sample (
_Am ^* , _bm ^* ) distances are calculated using the following formulas.

Next, in step S ₄₉ , the calculated ΔL (0) to ΔL
From (9), find J that minimizes ΔL (J). Then
In step S ₅₀ , it is determined whether J is 0, J
If is not 0, proceed to step S ₅₁ to recall the calibration constant of calibration channel J, proceed to step S ₅ , correct the sample data with the calibration constant of calibration channel J according to the following equation, and execute step S _Continue to ₅₃ .

Xm ← Xm · αmemo (J) Ym ← Ym · βmemo (J) Zm ← Zm · γmemo (J) When J = 0, the correction has already been made in the calibration channel 0, so the process directly proceeds to step S ₅₃ .

In step S _53, the tristimulus values of the sample which is calculated by the above procedure using (Xm, Ym, Zm), performs color space conversion into color system specified in the color system switching key, a display unit ( Display and print in 10).

In this way, since the calibration constant of the calibration reference sample having the chromaticity point closest to the chromaticity point of the measurement sample 1 is recalled and corrected, the absolute value measurement error caused by the spectral sensitivity error and the spectral sensitivity between the devices are increased. It is possible to minimize the machine difference of the measured values due to the variation of.

Correction channel i selected in (II) if not automatic calibration mode step S ₅₄ it is determined whether or not 0, and when the correction channel that is selected for 0 the process proceeds to step S _53, is selected When the calibration channel is not 0, the process proceeds to steps S ₅₅ and S _56, and the tristimulus value of the measurement sample is corrected as follows with the calibration constant of the designated calibration channel i.

Xm ← Xm ・ αmemo (i) Ym ← Ym ・ βmemo (i) Zm ← Zm ・ γmemo (i) Tristimulus value (Zm, Ym, Zm) of the sample calculated by the above procedure
Is used to perform color space conversion to the color system specified by the color system switching key, and display and print are performed on the display unit (10).

The steps S ₄₇ , S ₄₈ and S ₄₉ constitute an example of the calibration constant selecting means, and the step S ₄₃ or S ₅₂ constitutes an example of the correcting means.

In the above example, the measurement value was corrected by the calibration constant of the calibration reference sample having the closest chromaticity point to the chromaticity point of the measurement sample. Determine the calibration constant with a calibration reference sample that has points, determine in which region the chromaticity of the measurement sample exists, and correct the measured value with the calibration constant of the region where the chromaticity point of the measurement sample exists. May be. Also, select several calibration reference samples that have the closest chromaticity point to the measurement sample chromaticity point, and interpolate the calibration constants according to the distance between the measurement sample chromaticity point and the calibration reference sample chromaticity point. The calibration value may be newly obtained and the measured value may be corrected.

In the above embodiment, the user calibrated using several types of calibration reference samples when using the instrument, and performed the measurement in the automatic calibration mode. Obtain it and store it in a non-volatile memory etc., and if the user does not have multiple calibration reference samples, use the calibration constants stored in the machine to enable measurement in the automatic calibration mode. You can At this time, the user is channel 0
The automatic calibration mode can be used only by calibration using the dedicated calibration reference sample.

<Effects of the Invention> As is clear from the above, according to the present invention, a calibration constant is obtained from a plurality of calibration samples, the calibration constant is stored, and the measured value of the measured sample and the stored calibration constants are stored. Since the optimum calibration constant is determined based on the above, and the measured value is corrected, the measurement value due to the variation in the absolute value measurement error caused by the spectral sensitivity error and the variation in spectral sensitivity between devices can be minimized. can do.

[Brief description of drawings]

FIG. 1 is a block diagram of a photoelectric colorimeter with a spectral sensitivity correction function according to an embodiment of the present invention, FIG. 2 is a timing chart of a photoelectric conversion unit, and FIG. 3 is a flow chart showing data acquisition of tristimulus values of a sample. Fig. 4 is a flow chart showing the calculation of calibration constants and the storage of chromaticity points of calibration reference samples, and Fig. 5 is the selection of calibration constants and measurement data based on the chromaticity points of measurement samples and calibration reference samples. 3 is a flowchart showing the correction of 1 ... Sample, F ₁ , F ₂ , ..., F ₆ ... Optical filter, P ₁ ,
P ₂ , ..., P ₆ ... Photodiode, 5 ... CPU, 6 ... R
OM, 7 ... RAM, 100 ... Photoelectric conversion unit, 200 ... Data processing unit.

Claims (1)

[Claims] 1. A photoelectric conversion unit that decomposes light from a sample illuminated by a light source into basic color components and photoelectrically converts the light of the basic color components, and a calibration sample is measured in advance, Based on the information of the basic color components of the light from the calibration sample output from the conversion unit, the calculation means for calculating the calibration constant for the calibration sample, and the measurement by measuring a plurality of calibration samples A storage means for storing a plurality of calibration constants, and a determination for determining an optimum calibration constant based on a measured value of the measurement sample and a plurality of calibration constants stored in advance in the storage means when measuring the measurement sample. Based on the means and the calibration constant determined by the determining means,
A photoelectric colorimeter with a correction function, comprising: a correction unit that corrects a measurement value of a measurement sample; and a data processing unit having the correction unit.