JPH01233328A - Photometric apparatus - Google Patents

Abstract

PURPOSE:To measure accurately the brightness which a man senses, by determining an equivalent luminance in a mesopic vision region from a scotopic vision luminance, a photopic vision luminance and an adaptation coefficient determined from the two luminances. CONSTITUTION:A luminance information, a color information and a scotopic vision luminance value of an object of measurement are measured by four kinds of photosensors 1-4. A chromaticity (x, y) of the object of measurement is determined by a chromaticity computing element 5 from an output of the photosensor among them which corresponds to color matching functions X, Y and Z. From this chromaticity a correction coefficient C is determined for brightness/luminance conversion by a correction coefficient C calculating element 6. From this correction coefficient C and a luminance LP, an equivalent luminance Lbp in a photopic vision region is determined by an equivalent luminance Lbp calculating element 7. An equivalent luminance Lbs in a scotopic vision region is determined from a scotopic vision luminance Ls by an equivalent luminance Lbs calculating element 8. An adaptation coefficient (a) in a mesopic vision region is determined from Lbs and Lbp by an adaptation coefficient (a) calculating element 9, and an equivalent luminance Lbm in the mesopic vision region is determined from the coefficient (a), Lbp and Lbs by an equivalent luminance Lbm calculating element 10.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a photometric device that accurately measures the brightness perceived by humans in the mesopic vision region.

BACKGROUND OF THE INVENTION Conventionally, photometric systems have used values (luminance) measured by a light receiver having sensitivity characteristics matching the standard luminous efficiency Vλ to express the brightness of a reflector or a light emitter. This Vλ is determined as a representative value of the spectral sensitivity characteristics of the human eye in the photopic region.

In recent years, in the field of lighting, there has been a need for photometry that is compatible with various visual environments. Among these, the scotopic luminosity function V'λ is determined in the scotopic vision region, and the standard ratio luminous efficiency Vλ and the scotopic luminosity function V'λ are related at a wavelength of 555n1m, and quantitatively It is determined.

The mesopic vision region is located between the photopic vision region and the scotopic vision region, and the spectral sensitivity characteristics of the human eye change depending on the brightness level. Shifting towards shorter wavelengths. For this reason, the brightness perceived by humans with respect to colored light does not match the value (photometric amount) measured by a light receiver having spectral sensitivity characteristics of Vλ and V'λ.

One method for measuring brightness in the mesopic region is to use the measurement results of a photodetector with spectral sensitivity characteristics of standard luminous efficiency Vλ and scotopic luminous efficiency function V′λ, as shown in Figure 8. There is a method of adding weights according to the brightness level (luminance level) in mesopic vision and measuring the brightness in the mesopic vision region. In FIG. 8, 11 is a Vλ receiver having a spectral sensitivity characteristic of the standard luminous efficiency Vλ shown in FIG. ′
13 is a mesopic level detection section, and 14 is a calculation section. In FIG. 8, when the output of the Vλ photodetector 11 is expressed as L2, and the output of the V'λ photodetector 12 is expressed as L2, the arithmetic unit 14 calculates the brightness Lm in the mesopic vision region using the following equation.

Lm=nL, + (1-n) fist L2 -・・-
(1) Here, n is a coefficient determined by the brightness level in mesopic vision and is calculated by the mesopic vision level detection unit 13.

Generally, the output value of the Vλ photodetector 11, that is, the brightness value is used.

Problems to be Solved by the Invention The method shown in FIG. 8 can measure values closer to the brightness perceived by humans than conventional photometric quantities, but the standard relative luminous efficiency Vλ is also a scotopic luminous efficiency function. V'λ also does not take into account the sensitivity characteristics of humans to the colors of the object to be measured, so there is a discrepancy between the measured value and the brightness perceived by humans for colored light. Furthermore, when colored light is composite light (light that is a combination of monochromatic lights), the sensitivity of the human eye to colored light cannot be expressed as a composite of the sensitivity of the human eye to monochromatic light. It has been shown that additivity does not hold for sensitivity.

In this way, in the mesopic vision region, it is not possible to accurately measure the brightness perceived by humans in the complex light that exists in general visual environments using conventional photometric quantities and methods of synthesizing visibility functions. .

Means for Solving the Problems The present invention solves the above problems and aims to provide a practical photometric device that accurately measures the brightness perceived by humans in the mesopic vision region.

The present invention uses four types of receivers having spectral sensitivities corresponding to the color matching function "+3'r" and the scotopic luminosity function V'λ.
The tS device, the x+L "father yutake yt indicator 3n, the correction coefficient G production section connected to the chromaticity calculation section, the correction coefficient C calculation section and the y light receiver connected an Lbp calculation unit connected to the V′λ light receiver;
This device is composed of an adaptation coefficient a calculation section connected to the Lbp calculation section and the Lbs calculation section, and an Lbm calculation section connected to the adaptation coefficient a calculation section, the Lbp calculation section, and the Lbs calculation section, and the device calculates the color of the object to be measured. The brightness perceived by humans in the mesopic vision area is measured as equivalent brightness, taking information into consideration.

Function The present invention measures luminance information, 8 color information, and scotopic luminance values of a measurement object using four types of light receivers. Among these, the chromaticity (x, y) of the measurement target is determined from the output of the light receiver corresponding to the color matching function 's 7 *''.The correction coefficient C is used for brightness/luminance conversion from the chromaticity (x, y). Calculate the equivalent brightness Lbp in the photopic region from this correction coefficient C and the brightness. From the scotopic brightness, calculate the equivalent brightness Lb in the scotopic region.
Find s.

Adaptation coefficient a in the mesopic region from Lbs and Lbp
is obtained, and the equivalent luminance Lbm in the mesopic region is obtained from the adaptation coefficient a, Lbp, and Lbs.

Embodiment FIG. 1 shows a configuration diagram of a photometric device in an embodiment of the present invention. In Figure 1, 1 is the X receiver, 2 is 7
3 is an i-receiver, 4 is a V'λ receiver, 6 is a chromaticity calculation section, and 6 is a correction coefficient C calculation section.

7 is the Lbp calculation section, 8 is the Lbs calculation section, and 9 is the adaptation coefficient a.
The calculation unit 10 is an Lbm calculation unit. Figure 2 shows the specific configuration of the i-receiver in Figure 1.1! L
is an x1 photoreceiver, 1b is an x2 photoreceiver, and 1C is an adder circuit. Furthermore, the i1 receiver 11L has a sensitivity characteristic correction filter 1.
fLj, current of light receiving element 11L2 and operational amplifier 1a3 -
Consists of a voltage conversion amplifier circuit. In addition, x2 receiver' bJ
The photoreceiver 2, the photoreceiver 3, and the v'λ photoreceiver 4 have the same configuration as the photoreceiver 1a, except for the characteristics of the spectral characteristic correction filter. This shows the specific configuration of the calculation unit 6, which is composed of an encoding circuit (1) ea, an encoding circuit (?) 6b, and a correction coefficient C table memo 1J5Q. This shows the specific configuration of the calculation unit 9, which includes a t, bp range restriction unit 9a, and an Lbs range restriction unit 9.
b, an Lbp encoding circuit 90, an Lbs encoding circuit 9d, and an adaptation coefficient a table memo IJ 96. FIG. 7 shows a specific configuration of the Lbm calculation unit 10 in FIG. , an exponential separation unit corresponding to the Lbs signal system (
2) 10b, logarithmic conversion section (2) 10d, addition section (2) 1
0f, (1-a) calculation unit 1o1, multiplication unit (1) 10
g, multiplication section (2) 1oh, addition section (3) 10j, exponent separation section (3) 10h, anti-logarithmic transformation section 1ol and synthesis section 10m
It consists of The operation of the photometric device of this embodiment configured as described above will be described below.

Incident light from the object to be measured is received by four types of light receivers (i-receiver, 7-receiver, i-receiver, and V'λ receiver) having spectral sensitivity characteristics as shown in FIG. The brightness of the object to be measured can be measured by limiting the measurement range using a lens system or a light-shielding tube, and by limiting the amount of light that enters the light receiver. Among these, the i-receiver has a wavelength of 6001 as shown in FIG.
The light is separated into short wavelength side and long wavelength side with m as the boundary, and the short wavelength side is received by i and 12 photoreceivers, and the long wavelength side is received by 12 photoreceivers, i.
In the light receiver, the outputs of the light receivers 1a and 12 are weighted by relative sensitivities shown in FIG. 9, and added by an adding circuit 1C. In each photoreceiver, the spectral sensitivity characteristic shown in FIG. 9 is realized by combining the transmission characteristic of the sensitivity correction filter and the spectral sensitivity characteristic of the light receiving element, and is converted into a voltage value by a current-voltage conversion amplifier circuit of an operational amplifier.

i Output X from receiver 1, 7 Output Y from receiver 2, i
The output Z from the light receiver 3 is supplied to the chromaticity calculation section 6. The chromaticity calculation unit 6 calculates the chromaticity (x, y) from the following equation.

x=X/(X+Y+Z) ・・・・・・・・・@)
y = Y / (X + Y + Z)...
(3) Furthermore, the output of the chromaticity calculation section 6 (x
, y) are supplied to the correction coefficient G calculation section 6. Correction coefficient C
The calculation unit 6 calculates a correction coefficient for converting the measured value into brightness perceived by humans based on the physiological effect of the color information. This correction factor is based on the National Research Institute of Canada (NRC).
The coefficients proposed by Ware and Cowan (hereinafter referred to as W&C) are common. In this embodiment, a correction coefficient calculated from the WAC formula was used. The correction coefficient C is used to obtain a correction value for brightness and luminance perceived by humans based on color information from the measurement object, and is obtained using equation (4). Note that equation (4) is normalized to 570nl11.

The correction coefficient G calculation unit 6 has a correction coefficient (table memo IJ 80) in order to perform the calculation of equation (4) in a short time.The output (chromaticity) from the chromaticity calculation unit 6 is
Only values in the range 0 to 1 are accepted. Therefore, the chromaticity X is supplied to the encoding circuit (1) 6 & of the correction coefficient calculation unit 6,
Divide into 00 steps or more and code. For example, 1
If it is divided into 00 steps, 0 to o and ol are treated as one group, and the representative value is XQl. 0.01 to 0.02 is treated as the next group, and the representative value is treated as XO2. Similarly, the chromaticity y is also encoded by the encoding circuit (2) 6b,
One representative value Xci + 3'ci is determined for each group. Representative value of coded chromaticity xc: t l
The correction coefficient C is calculated in advance using equation (4) using 'lcl, and is stored in the correction coefficient G table memory. At the time of measurement, the measured values (x, y) are coded, the table memory is accessed, and the correction coefficient C is read out. As a result, by inputting the measured values (x, y) to the correction coefficient G calculating section 6, the correction coefficient G can be calculated in a short time without performing the calculation of equation (4) during measurement. encoding circuit am,
The number of divisions of ab may be set according to the accuracy of the correction coefficient C to be obtained. The calculation accuracy of the correction coefficient C improves as the number of divisions increases, but generally, the calculation accuracy is sufficient if there are 100 or more divisions.

Next, the output C of the correction coefficient C calculation section 6 and the output Y of the seven light receivers 2 are supplied to the Lbp calculation section 7. Since the Y light receiver has a spectral sensitivity characteristic of the standard luminous efficiency Vλ shown in FIG. 9, the output Y of the Y light receiver 2 represents the luminance value Lp. The Lbp calculation unit 7 calculates the equivalent luminance Lbp in photopic vision based on the following formula.

Lbp = Lp -G ・・・River...
(6) On the other hand, the output Lst from the V'λ photodetector 4 is Lbs
It is supplied to the calculation unit 8. The scotopic luminosity function is the spectral sensitivity characteristic of the human eye that corresponds to areas with low brightness levels.
There is little color information. Therefore, the equivalent luminance Lbs in the scotopic region is calculated using equation (6).

Lbs=to*Ls (K: constant) −−−−・−(
6) Next, the output Lbp of the Lbp calculation unit 7 and the output Lbs of the Lbs calculation unit 8 are supplied to the adaptation coefficient a calculation unit 9.

In the adaptation coefficient 1 calculating section, the Lbp range limiting section 9! L and Lb
The range limiter 9b limits the range that the Lbp value and Lbg value can take. The logarithmic values of Lbp and Lbs are encoded by an Lbp encoding circuit 9C and an Lbg encoding circuit 9d,
Read the adaptation coefficient a table memory with the encoded value. A method of calculating the adaptation coefficient & in the adaptation coefficient a calculation section 9 will be explained using FIGS. Figure 6 is a curve showing the relationship between adaptation coefficient a and equivalent luminance (Lb).
This was obtained through observation experiments conducted by several people using colored light at the level of mesopic vision, with the horizontal axis representing the equivalent luminance and the vertical axis representing the adaptation coefficient a.

The adaptation coefficient & is the measured value L of the equivalent luminance in the photopic region
Logarithmic value of bpi Lbpi and logarithmic value log of the measured value of equivalent luminance in scotopic vision Lbsi Connect Lbsi with a straight line, and the value ai for the intersection point m with the curve of adaptation coefficient a
It can be found as The adaptation coefficient a can be easily obtained graphically as shown in FIG. 6, but it is necessary to perform complicated calculations to obtain it by calculation. Furthermore, since both Lbpi and Lbsi can take numerical values from 0 to o:1 in principle, the calculation target range is wide and calculation becomes complicated. Therefore, the possible range of Lbs and Lbp is limited to the mesopic region. The calculation range of Lbs is L
bs range limited part 9 b TeO0OO30d/m”≦Lb
Limited to s≦300cd7/i, Lbp range limiting part 9a
The calculation range of Lbp is set to 0.000141 cd/
'irr≦Lbp≦14. I Cd/rn”,
There were 10 change ranges. Generally, the range of mesopic vision is 0.003 cd/rn" to 14.1 cd/in
Since the range of change is ``, it is a range that can sufficiently cover the range of change of 1o5.It will be explained with reference to FIG. 6 that even if the ranges of Lbp and Lbg are limited to the above, there is no major influence on measurement.

FIG. 6 shows what value the adaptation coefficient a takes with respect to Lbp and Lbs. In Figure 6, the horizontal axis is L
bs, and the vertical axis is Lbp. In Figure 6, 0.00
3cd/iy≦Lbg≦3000 d/m” Te, 0,
oo0141Cd/rrf≦Lbp≦14.1 cd/
In the case of i (area A), the adaptation coefficient a is determined according to the curve a=&1 shown in Fig. 6.
Lbs in Lbp) 14.10(!/rn' (
In the area (region opening), the curve of the adaptation coefficient turtle and the straight line connecting Lbpi and Lbsi do not intersect, and a=o. Similarly, Lbp≦
14.10 (27m” or less, Lbs<o, oo3Cd
/mI (area C), a=1 o O,0
03ca/static≦Lbs≦3ooCd/ml, Lbp
<o, o In the case of OO141ca7y (region 2), theoretically a=ai, but since a takes a value close to 1, a=1 is set.

0.000141 cd/mI≦Lbp≦14. IC
(If Lbs > 3o o cl/m" at 1/rn" (area E), theoretically a = ai, but a is close to 0, so a = O. , Lbp
) 14. I Cd/in”, Lbs <0.003
cd/rn' (7) region (to region) and Lbp <0.0
00141cd/rn"Lbs) 300cd/
In the region of inJ (area G), Lbp is the value obtained based on Vλ in Fig. 9, and Lbs is the value obtained based on V'λ in Fig. 9, and these wavelength ranges overlap. Therefore, it is thought that such conditions almost never exist during measurement. Therefore, the areas to and from are excluded from the measurement range. As a result, with respect to changes in Lbp and Lbs, it is possible to almost accurately determine 8 within the mesopic vision region.

Next, the output of the adaptation coefficient a calculation section 9 and the outputs of the Lbp calculation section 7 and the Lbs calculation section 8 are supplied to the Lbm calculation section 1o. The Lbm calculation unit 10 calculates the equivalent luminance Lbm in mesopic vision according to equation ('7).

Lbm −Lbp −Lbs(” ) -----
-.- (7) The Lbm calculation unit 1o changes equation (V) to equation (8) to obtain Lbm.

log Lb+++ = a JogLbS-)-(1
-t) logLbp (8) The Lbp signal input to the Ltoa calculation unit 10 is separated by the exponent separation unit (1) 101L into the mantissa part (absolute value is less than 1 t4) and the exponent part ( integers). The mantissa part is further supplied from the exponent separation unit (1) 101L to the logarithmic conversion unit (1) 1oC, and the exponent part is supplied to the addition unit (1) 100. A logarithmic conversion unit (1) 100 converts the mantissa into a logarithm. The logarithmically converted mantissa part is added to the exponent part in an adder (1) 1015 to obtain a log Lbp value. Similarly, log Lbs is obtained using an exponent separation section (2) 10b, a logarithmic conversion section (2) 10d, and an addition section (2) 10f'. The output value a of the adaptation coefficient a calculation unit 9 is determined by the (1-a) calculation unit 1oi. The multiplier (1) 10g calculates the second term (
1-a) - Find JogLbp. In addition, the multiplication section (2
) 1oh, the output log Lb of the adder (2) 1of
From the g and a values, & −log Lb in the first term of equation (8),
Find s. Furthermore, in the addition section (3) 10j,
The right side of equation (8) is calculated from the output of the multiplier (1) 10g and the output of the multiplier (2) 10h. Addition section (3) 1
The output of 0j is supplied to an exponent separation unit (3) 10k, and is separated into an integer part (exponent part) and a decimal part (mantissa part).

As a result, the mantissa takes only numerical values from 0 to 1, and is subjected to anti-logarithm transformation in the anti-logarithm transformation unit 101. Anti-logarithm transformation unit 1
The output of 01 and the index output of index separation unit (3) 10k are supplied to a synthesis unit 1011, and the equivalent luminance Lbm value in the mesopic region is determined. By doing this, L
The numerical values that are logarithmically transformed or antilogarithmically transformed in the bm calculation unit 10 are both in the range of 0 to 1 in absolute value, and if the logarithmic value and antilogarithm value are calculated and stored in advance using table memory, the memory will be saved. Logarithm/anti-logarithm conversion can be performed in a short time and with a small capacity.

In the above embodiment, the correction coefficient C based on the color of the object to be measured is calculated using the WIC formula, but it may be calculated using a model formula similar to this. Furthermore, it is practically acceptable to use the output of the device as a substitute.

In the above embodiment, it was limited to the mesopic vision region, but as is clear from equation (8), if a=O, Lbm = Lbp, and if a=1, Lbm = Lbs, (8)
In the present invention, the equivalent luminance can be measured over the range from the photopic region to the scotopic region.

In addition, when calculating the equivalent brightness Lbs in the scotopic vision area, the contribution of color information is small in the scotopic vision area, so Lbs was calculated by multiplying the scotopic brightness by a constant K. If Lbs is determined by using the brightness, it is possible to measure the brightness even closer to the brightness perceived by humans, and the measurement accuracy is improved.

Effects of the Invention The photometric device of the present invention has color matching functions X, 7. Four types of receivers having spectral sensitivities of Z and scotopic luminosity function V'λ,
,7. A chromaticity calculation section connected to the Z light receiver, a correction coefficient G calculation section connected to the chromaticity calculation section, a correction coefficient C calculation section connected to the Y light receiver, and a correction coefficient G calculation section connected to the y light receiver to calculate equivalent luminance L in the photopic region.
a bp calculating section, an Lbg calculating section connected to the V'λ light receiver and calculating equivalent luminance in a scotopic vision region, an adaptation coefficient 1 calculating section connected to the Lbp calculating section and the Lbs calculating section, and an adaptation coefficient a calculating section. By providing an Lbm calculation section that is connected to the Lbp calculation section and the Lbs calculation section and calculates the equivalent luminance in the mesopic region, the color information of the measurement target is measured in the mesopic region, and the luminance value is corrected based on this. , it is possible to measure the brightness perceived by humans as equivalent luminance, which has great practical effects.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a photometric device according to an embodiment of the present invention, FIG. 2 is a specific block diagram of the i-receiver of the same device, and FIG. 3 is a specific block diagram of the correction coefficient C calculating section. Fourth
The figure is a concrete block diagram of the correction coefficient C calculating section, FIG. 6 is a characteristic diagram showing the curve of the adaptation coefficient &, and FIG. Equivalent luminance Lbp in the region, equivalent luminance Lbs in the scotopic region
Figure 7 is a concrete block diagram of the four Lbm calculation unit, Figure 8 is a block diagram of a conventional photometer, and Figure 9 is a characteristic diagram showing the relative sensitivity of four types of light receivers. It is. 1... i-receiver, 2...i-receiver, 3
......i photoreceiver, 4...V'λ photoreceiver,
6...Chromaticity calculation unit, 6...Correction coefficient C
Calculation unit, 7... Lbp calculation unit, 8...
Lbs calculation unit, 9...adaptation coefficient a calculation unit, 1o
...Lbm calculation section. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure 3 Figure 4 Figure N 5 Figure α003 300Lbs
(cd/m Figure 8

Claims (4)

[Claims] (1) Four types of light receivers with spectral sensitivities of color matching functions @x@, @y@, @z@ and scotopic luminosity function V'λ, and these @x@, @y@, @ z@ A chromaticity calculation unit connected to the light receiver, a correction coefficient C calculation unit connected to this chromaticity calculation unit and which calculates a coefficient depending on the color of the brightness perceived by humans, and this correction coefficient C calculation unit and the @ an Lbp calculation unit connected to the y@ light receiver and which calculates the equivalent brightness in the photopic region; an Lbs calculation unit connected to the V′λ light receiver and which calculates the equivalent brightness in the scotopic region; and the Lbp calculation unit. an adaptation coefficient a calculation section that is connected to the Lbs calculation section and calculates an adaptation coefficient a according to the brightness level, an adaptation coefficient a calculation section and the Lb
It is connected to the p calculation section and the Lbs calculation section and logLbm=alogLbs+(1-a)logLb
Lb to find the equivalent luminance in the mesopic region based on p
A photometric device comprising an m calculation section. (2) The adaptation coefficient 1 calculation unit calculates that Lbp≦14.1cd/m
^2 and Lbs≧0.03cd/m^2. (3) The adaptation coefficient a calculation section is 10 of Lbp and Lbs.
3. The photometric device according to claim 2, which operates over an input range of ^5. (4) The adaptation coefficient a calculation unit determines that Lbs>300cd/m^
2, 0.000141cd/m^2≦Lbp≦14.
For 1cd/m^2, a=0 and Lbp<0.0
00141cd/m^2 and 0.003cd/m^2≦L
For bs≦300cd/m^2, a=1 and 0.0
00141cd/m^2≦Lbp≦14.1cd/m^
2 0.003cd/m^2≦Lbs≦300cd/m
Claim 3, wherein a for ^2 is determined by a theoretical formula.
Photometric device as described.