JPH04301531A - Photoelectric colorimeter with error correcting function - Google Patents

Abstract

PURPOSE:To effectively correct the measured chromaticity by obtaining the correcting amount based on the measuring error of the wavelength of a crossing point between a straight line connecting an arbitrary reference point on the chromaticity diagram and the chromaticity measuring value of an arbitrary light source to be measured, and the locus of a point obtained by adding the measuring error to the chromaticity coordinates of a monochromatic light of a specific wavelength or the like. CONSTITUTION:The measuring error of the chromaticity for a monochromatic light of the wavelength of the chromaticity coordinates Qm(xm(lambda), ym(lambda)) on the chromaticity diagram are represented by xm(lambda), ym(lambda). At this time, the outputs of photodetectors S1-S3 from an arbitrary light source 1 via optical filters F1-F3 are converted to chromaticity values via corresponding photoelectric converting circuits E1-E3, an A/D converting part, 2 and an operation control part 3. The wavelength lambda1 of a crossing point Q'1 between a straight line connecting the chromaticity measuring value P1 (x1, y1) and the chromaticity coordinates P0 (x0, y0) of an arbitrary reference point, and the locus of a point obtained by adding the measuring error xm(lambda), ym(lambda) to the chromaticity coordinates Qm(xm(lambda), ym(lambda)) of the monochromatic light of the wavelength lambda=380-780nm is operated. The measuring value P1 (x1, y1) is corrected with the correcting amount x, y operated according to the formula.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tristimulus value direct reading type photoelectric colorimeter having an error correction function.

0002

[Prior Art] In a photoelectric colorimeter (tristimulus value direct reading type), spectral responsivity is approximated to color matching functions (outer 1), (outer 2), and (outer 3) by a combination of a color filter and a light receiving element. ing.

0003

[Outside 1]

0004

[Outside 2]

[0005]

[Outer 3]

However, since it is not possible to perfectly match the spectral responsivity of the photoelectric colorimeter to these color matching functions, measurement errors occur when a light source different from the calibration light source is measured.

[0007] Conventionally, in order to suppress such measurement errors, a method has generally been used in which a plurality of calibration reference light sources are prepared and a colorimeter is calibrated using the calibration reference light source whose spectral distribution approximates that of the light source to be measured. It was getting worse. However, it is inefficient for the measurer to select a calibration reference light source according to the type of light source to be measured and always perform calibration before measurement. In order to improve this problem, the following methods have been conventionally used.

First, the colorimeter is provided with a function of storing the calibration constant km of a plurality of calibration reference light sources and the chromaticity coordinate Tm of the calibration point. Then, the chromaticity region is divided into a predetermined number of regions, and each region is provided with a calibration point and a calibration constant km. Furthermore, as another method, the distance on the chromaticity coordinate between the chromaticity coordinate Tm of the calibration point of the plurality of calibration reference light sources and the chromaticity coordinate T1 of the measurement point with respect to the light source to be measured is used as a parameter, A method is also used in which the chromaticity coordinate T1 of the measurement point is corrected from the calibration constant km.

[0009]

[Problems to be Solved by the Invention] However, with such conventional methods, in order to improve measurement accuracy, many calibration points are required, many calibration reference light sources must be prepared, and , it is quite inconvenient for the measurer to calibrate the colorimeter using these multiple light sources. Further, even if the light sources exhibit almost the same chromaticity coordinates, the spectral distribution may differ between the two, and the difference in the spectral distribution causes a difference in the error in the chromaticity measurement value. For this reason, the conventional method of selecting a calibration point close to the measured chromaticity value and performing the correction has a problem in that the error cannot be sufficiently corrected.

0010

[Means for Solving the Problems] The present invention provides a method in which a straight line connecting an arbitrary reference point on a chromaticity diagram and a chromaticity measurement value of an arbitrary measured light source corresponds to the chromaticity coordinates of monochromatic light of wavelength λ. The correction amount Δx is calculated by (Equation 3) based on the measurement error of the wavelength at the point that intersects the locus of λ = 380 to 780 nm at the point including the measurement error.
, Δy, or the average value of the chromaticity measurement error for a plurality of reference light source groups is determined by (Equation 4) and set as the correction amounts Δx, Δy, and the chromaticity coordinates of the measured value of the light source to be measured are determined by the correction amounts Δx, Δy. This is a photoelectric colorimeter characterized by having a function of correcting.

[0011]

[Math 3]

0012

[Math 4]

[0013]

[Operation] The present invention uses the correction amounts Δx, Δy obtained from the chromaticity measurement error for monochromatic light of wavelength λ by (Equation 5) or the average value of the chromaticity measurement error for a plurality of reference light source groups (
By correcting the chromaticity measurement value of the light source to be measured using the correction amounts Δx and Δy obtained by Equation 6), highly accurate chromaticity measurement can be performed.

[0014]

[Math 5]

[0015]

[Math 6]

[0016]

Embodiment FIG. 1 is a block diagram showing the configuration of a photoelectric colorimeter in a first embodiment of the present invention. In Figure 1, F
1 to F3 are optical filters, and S1 to S3 are light receiving elements. The combination of optical filter F1 and light receiving element S1 constitutes the spectral response (outer 4) that approximates the above color matching function (outer 1), and the combination of optical filter F2 and light receiving element S2 forms the above color matching function (outer 2). The combination of the optical filter F3 and the light receiving element S3 forms a spectral response (outer 6) that approximates the color matching function (outer 3).

[0017]

[Outside 4]

[0018]

[Outer 5]

[0019]

[Outside 6]

FIG. 2 shows the above color matching functions (outer 1) and (outer 2)
, (outer 3) and the spectral responsivity of the colorimeter (outer 4), (outer 5)
), (external 6) is a diagram showing an example. The accuracy of the colorimeter measurements depends on how well the spectral responsivity (outer 4), (outer 5), and (outer 6) are approximated to the color matching functions (outer 1), (outer 2), and (outer 3). , usually cannot be perfectly matched, as shown in FIG. Therefore, this deviation in spectral responsivity causes an error in the chromaticity measurement value.

In FIG. 1, reference numeral 1 indicates a light source to be measured, and E1 to E
3 is a photoelectric conversion circuit, 2 is an A/D conversion section, and 3 is an arithmetic control section. The light emission of the light source 1 to be measured is filtered through optical filters F1 to F.
3. Light is received by the light receiving elements S1 to S3. Light receiving elements S1 to S
The outputs from A/D converter 3 pass through photoelectric conversion circuits E1 to E3, respectively, and are input to A/D converter 2. The output from the A/D converter 2 is converted into a chromaticity value in the arithmetic control section 3 using (Equation 7) and (Equation 8).

[0022]

[Math 7]

[0023]

[Math. 8]

In (Equation 7), P(λ) is the measured light source 1
is the relative spectral distribution of FIG. 3 shows an example of the chromaticity measurement values calculated in this manner expressed on chromaticity coordinates. Figure 3
In , curve 7 (solid line) and white circle mark indicate wavelength λ (λ=
380,385,. ．． ．． , 780 nm) of monochromatic light (xm(λ), ym(λ)). Curve 8 (dashed line) and the triangular mark indicate the spectral responsivity of the colorimeter, which is the color matching function (outer 1), (outer 2) as shown in Figure 2 (outer 4), (outer 5), (outer 6). , (outer 3), the wavelength λ (λ = 380, 385, ..., 78
The chromaticity measurement value Qm'(x
This is an example of a curve connecting m'(λ) and ym'(λ)). The chromaticity coordinates Qm(xm(λ), ym(λ)) are (Equation 7)
In this case, the spectral responsivity of the colorimeter (outer 4), (outer 5), and (outer 6) completely match the color matching functions (outer 1), (outer 2), and (outer 3), Chromaticity coordinate Qm'(xm'(λ
), ym'(λ)) is the color matching function (outer 1) where the spectral responsivity of the colorimeter (outer 4), (outer 5), (outer 6) is the color matching function (outer 1)
, (Outer 2), (Outer 3), the chromaticity coordinates Qm (xm (λ), ym (λ)) and the chromaticity measurement value Qm'(xm' (λ), ym' (λ)) can be calculated using (Equation 7) and (Equation 8) if the spectral responsivity (Ex. 4), (Ex. 5), and (Ex. 6) of the colorimeter is known.

The chromaticity coordinate Qm (xm
(λ), ym(λ)), chromaticity measurement value Qm'(xm'(λ
), ym'(λ)) to the measurement error Δxm(λ), Δym
(λ) is obtained by (Equation 9).

[0026]

[Math. 9]

The chromaticity coordinates Qm (xm
(λ), ym(λ)) is stored in the storage unit 4.

In FIG. 3, the chromaticity measurement value for an arbitrary measured light source is P1 (x1, y1), and the separately determined P0
Let (x0, y0) be the chromaticity coordinates of the reference point. Also, P0
The point where the straight line connecting (x0, y0) and P1 (x1, y1) intersects curve 8 is Q1'(x1'(λ), y1'(λ)
), and the wavelength at that time is λ1. Measurement error Δxm(λ1), Δym( when measuring monochromatic light with wavelength λ1
λ1) is called from the storage unit 4 to the error correction calculation unit 5. The error correction calculation unit 5 calculates the correction amounts Δx and Δy of the chromaticity measurement value P1 (x1, y1) using the above (Equation 1). From this correction amount, the corrected chromaticity measurement value P1'(x1', y
1′) is calculated using (Equation 10), and the value is displayed on the display unit 6.

[0029]

[Math. 10]

f(x) in the above (Equation 1) is defined as the measurement point P1 (
x1, y1) is located between the reference point P0 (x0, y0) and the monochromatic light measurement point Q1', which weights the error correction amount.
Takes a value of f(x)≦1. Generally, if the measured value is around the reference point, the error will be small, and the closer you go to the periphery of the chromaticity diagram, the more the error will suddenly increase.When it becomes completely monochromatic light, it will become as shown by the solid line (white circle mark) in Figure 3. This will result in an error. Therefore, if a function such as (Equation 11) is used as f(x), processing similar to the above characteristics can be achieved.

[0031]

[Math. 11]

FIG. 4 shows an example of a value corrected using equation (11). In FIG. 4, R1 to R4 (white circle marks) indicate the chromaticity points (true values) of arbitrary light sources to be measured, and P1 to P4
(Triangular marks) indicate chromaticity measurement values when measuring the light source to be measured, and P1' to P4' (black circle marks) indicate correction values after error correction is performed by the method described above. As can be seen from FIG. 4, according to the present invention, chromaticity measurement values can be corrected with high accuracy.

Next, a second embodiment of the present invention will be explained. In this embodiment, the process of calculating the chromaticity measurement value from the light emission of the light source 1 to be measured is the same operation as in the first embodiment.

A plurality of (n types) white light sources are set as a reference light source group, and the measurement error Δxi of the photoelectric colorimeter for each reference light source is
Δyi (i=1, . . . , n) and the average values Δx and Δy of the measurement errors obtained by the above (Equation 2) are stored in the storage unit 4 in advance. Δxi and Δyi are actually measured by lighting an actual light source, or are calculated from the spectral responsivity using (Equation 7) and (Equation 8). In the error correction calculation section 5, the chromaticity measurement value obtained by the calculation control section 3 is corrected using the correction amount read from the storage section 4, and displayed on the display section 6. FIG. 5 shows an example of values obtained by correcting errors in measured chromaticity values in the embodiment of claim 2 of the present invention. In FIG. 5, R5 to R8 (white circle marks) indicate the chromaticity point (true value) of any measured light source,
P5 to P8 (triangular marks) indicate the chromaticity measurement values when measuring the light source to be measured, and P5' to P8' (black circle marks) indicate the correction values after error correction is performed by the method described above. As can be seen from FIG. 5, according to the present invention, chromaticity measurement values can be corrected with high accuracy.

Next, a third embodiment of the present invention will be explained. In the third embodiment, in the second embodiment, the storage unit 4
The amount of correction stored in 1 and the operation of the error correction section 5 are changed as follows. That is, a plurality of reference light source groups are classified by type of light source such as fluorescent lamps and metal halide lamps (m ways), and the correction amount (Δx, Δy) i is calculated from the average value of the measurement error for the reference light source group for each classified type. (
i=1,. ．． ．． , m) and store the values in the storage unit 4 in advance. In the error correction calculation section 5, depending on the type of the light source 1 to be measured,
The corresponding value from among the correction amounts (Δx, Δy) i (i=1, . . . , m) is read, and the chromaticity measurement value calculated by the arithmetic control unit 4 is corrected. The display unit 6 displays the chromaticity measurement value corrected by the error correction unit 5. By correcting the measured chromaticity value using such a method, the measured value of chromaticity can be corrected with higher accuracy because the correction can be made in accordance with the type of light source.

[0036] The above-mentioned error correction calculation section 5 and the like are usually realized in software using a computer, but are not limited to this, and of course may also be realized using a dedicated hardware circuit equipped with these functions. good.

[0037]

[Effect of the invention] As is clear from the above,
In the present invention, a straight line connecting an arbitrary reference point and an arbitrary measured chromaticity value of a light source on a chromaticity diagram is a point where a measurement error is added to the chromaticity coordinates of monochromatic light with wavelength λ = λ = Based on the measurement error of the wavelength at the point intersecting the trajectory of 380 to 780 nm, the above (Equation 1)
) By correcting the chromaticity measurement value for the light source to be measured using the correction amounts Δx and Δy obtained by the above equations, the present invention has the advantage that correction that is particularly effective for colored light can be realized.

Furthermore, the present invention calculates the average value of the chromaticity measurement errors for a plurality of reference light source groups using the above (Equation 2) and sets the correction amounts Δx, Δy, and uses these correction amounts Δx, Δy to adjust the color of the light source to be measured. By correcting the power measurement value, there is an advantage that effective correction can be made especially for general illumination light sources whose type of light source is clearly defined.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a photoelectric colorimeter with an error correction function according to an embodiment of the present invention.

FIG. 2 is a graph showing an example of color matching functions and spectral responsivity of a colorimeter.

FIG. 3 is a graph of chromaticity coordinates with chromaticity measurements shown.

FIG. 4 is a graph of chromaticity coordinates showing a corrected example.

FIG. 5 is a graph of chromaticity coordinates showing an example corrected according to another embodiment.

[Explanation of symbols]

1. Light source to be measured 2 A/D conversion section 3 Arithmetic control section 4. Storage section 5 Error correction calculation section 6 Display section

Claims (3)

[Claims] Claim 1: The chromaticity coordinates are Qm(xm(λ), ym(λ)
) The chromaticity measurement error for monochromatic light of wavelength λ is Δxm
(λ), Δym(λ), on the chromaticity diagram, the chromaticity measurement value P1 (x1, y1) for any input measured light source and the chromaticity coordinate P0 ( x
0, y0), the measurement error Δ
Point Qm'(xm'(
Calculate the wavelength λ1 of the point Q1' that intersects the locus of λ = 380 nm to 780 nm of λ), ym' (λ)), and calculate the chromaticity measurement value by the correction amount Δx, Δy obtained by calculating by (Equation 1). A photoelectric colorimeter with an error correction function, characterized in that it includes a calculation means for correcting P1 (x1, y1). [Math 1] Claim 2: When the chromaticity measurement error for a plurality of (n) reference light source groups is expressed as Δxi, Δyi (i=1,...,n), the chromaticity measurement value for any measured light source. P5
A photoelectric colorimeter with an error correction function, characterized in that it is equipped with a calculation means for correcting a measurement error by correction amounts Δx, Δy obtained by (Equation 2) for (x5, y5). [Math 2] 3. A plurality of reference light source groups are classified into several types (m ways), and the correction amount (Δx, Δy) i (i=1, . . . , m) is calculated for each classified type. ) is stored in the storage means in advance, and the calculation means corrects the measurement error by selecting a corresponding value from the correction amount (Δx, Δy) i according to the type of the light source to be measured. 3. A photoelectric colorimeter with an error correction function according to claim 2.