JP6631001B2 - Stimulus value direct reading type colorimeter - Google Patents

Description

  The present invention relates to a stimulus value direct reading type colorimeter that measures colorimetric values corresponding to each of a plurality of color matching functions.

  The color matching function of the XYZ color system adopted by the International Commission on Illumination (CIE) in 1931 (hereinafter referred to as the "CIE 1931 XYZ color matching function") is used to find objective color index values. Is a kind of color evaluation function. The CIE1931XYZ color matching function has been employed for a long time as a standard color evaluation function for measuring colors of displays, lamps, and the like. Patent Literature 1 is an example.

  However, the colorimetric value obtained when the CIE1931XYZ color matching function is selected as the color evaluation function does not always match the actual human visual perception as described in Patent Document 2. For this reason, a color matching function in which the CIE 1931 XYZ color matching function is modified (hereinafter, referred to as “modified color matching function”) has been proposed. For example, Vos and Judd (1978) modified color matching function, TR-170-1 modified color matching function, Stockman and Sharpe (1998) modified color matching function, and the like have been proposed. The colorimetric value obtained when the corrected color matching function is selected is more consistent with the actual human visual perception as compared with the colorimetric value obtained when the CIE1931XYZ color matching function is selected.

JP-A-11-6766 JP 2011-517783 A

  As described above, the colorimetric value obtained when the corrected colorimetric function is selected is compared with the colorimetric value obtained when the CIE1931XYZ colorimetric function is selected, and is closer to the actual human visual perception. Matches. However, since the CIE1931XYZ color-matching function has occupied the position of a standard color evaluation function for a long time, the colorimetric value when the CIE1931XYZ color-matching function is selected for comparison with past measurement data, etc. It is often desired to measure. Therefore, it is desirable that both the colorimetric value when the CIE1931XYZ colorimetric function is selected and the colorimetric value when the corrected colorimetric function is selected can be measured by one colorimeter.

  To measure both the colorimetric value when the CIE1931XYZ colorimetric function is selected and the colorimetric value when the modified colorimetric function is selected with one colorimeter, the colorimetry method must be spectrophotometric. The color method may be used, or the colorimetry method may be a direct stimulus value reading method, and both a colorimetric optical system corresponding to the CIE1931XYZ colorimetric function and a colorimetric optical system corresponding to the corrected colorimetric function may be provided. However, they complicate the colorimeter.

  This problem is not limited to the case where one colorimeter measures the colorimetric values corresponding to each of the CIE1931XYZ colorimetric function and the modified colorimetric function. This generally occurs when a colorimetric value corresponding to is measured.

  The invention described in the detailed description of the invention aims to solve the above problems. The problem to be solved by the invention described in the detailed description of the invention is to measure a colorimetric value corresponding to each of a plurality of color matching functions by using a single stimulus value direct reading type colorimeter having a simple configuration. It is to be.

A stimulus value direct-reading colorimeter that measures colorimetric values corresponding to a first color matching function and a second color matching function different from the first color matching function for a plurality of different objects to be measured . The colorimetric optical system group receives a light flux that does not pass through the correction color filter when one correction color filter is disposed at the non-correction position, and has a spectral responsivity group approximate to the first color matching function. And outputting a first signal group having an intensity corresponding to the spectral intensity of the light to be measured. When one correction color filter is arranged at the correction position, the light beam transmitted through the correction color filter is output. The light receiving unit outputs a second signal group having a spectral responsivity group approximate to the second color matching function and having an intensity corresponding to the spectral intensity of the measured light. The deriving mechanism derives a colorimetric value when the first color matching function is selected from the first signal group, and derives a colorimetric value when the second color matching function is selected from the second signal group. Derived from The spectral transmittance of the correction color filter is a value obtained by dividing the second color matching function by the first color matching function.

  The colorimetric value corresponding to each of the plurality of color matching functions is measured by one stimulus value direct reading type colorimeter having a simple configuration.

  These and other objects, features, aspects and advantages of the invention will become more apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.

It is a graph which shows CIE1931XYZ color matching function. 31 is a graph showing Vos and Judd (1978) modified color matching function and CIE1931XYZ color matching function. It is a graph which shows TR-170-1 correction color matching function and CIE1931XYZ color matching function. It is a schematic diagram of a color luminance meter. It is a schematic diagram of an optical system of a measurement probe. It is a schematic diagram of an electric system of a measurement probe and a measuring instrument main body. 4 is a graph showing a spectral transmittance of a color filter and the like. 9 is a graph showing a spectral transmittance of a correction color filter. 9 is a graph showing a product obtained by multiplying a spectral transmittance of a correction color filter by a Vos and Judd modified color matching function and a CIE1931XYZ color matching function. 6 is a graph showing a quotient obtained by dividing a color matching function B by a color matching function A. FIG. 3 is a diagram for explaining a chromaticity calculation algorithm. 5 is a flowchart illustrating a flow of chromaticity measurement. It is a schematic diagram of an illuminometer. It is a graph which shows the spectral intensity of the light which a white LED emits for every individual.

1. Color matching function The color luminance meter of this embodiment has both a colorimetric value when the CIE1931XYZ color matching function is selected as the color evaluation function and a colorimetric value when the modified color matching function is selected as the color evaluation function. Can be measured. In the following description, the CIE1931XYZ color matching function and the modified color matching function will be described before describing the color luminance meter.

2 CIE1931XYZ color matching function The graph of FIG. 1 shows the CIE1931XYZ color matching function.

  As shown in FIG. 1, the CIE1931XYZ color matching function has an x component xbar (lambda), a y component ybar (lambda), and a z component zbar (lambda). The x component xbar (lambda), the y component ybar (lambda), and the z component zbar (lambda) of the CIE1931 XYZ color matching function are functions of the wavelength lambda. The x component xbar (lambda) of the CIE1931XYZ color matching function has peaks near 442 nm and 599 nm. The y component ybar (lambda) of the CIE1931XYZ color matching function has a peak near 555 nm. The z-component zbar (lambda) of the CIE1931XYZ color matching function has a peak near 446 nm. The x component xbar (lambda) of the CIE1931 XYZ color matching function can be divided into a short wavelength side xbar1 (lambda) and a long wavelength side xbar2 (lambda). The short wavelength side xbar1 (lambda) is a portion of the wavelength range that includes the short wavelength peak of the x component xbar (lambda) but does not include the long wavelength peak, for example, a wavelength range of 500 nm or less. The long wavelength side xbar2 (lambda) is a portion of the x component xbar (lambda) in a wavelength range that includes a peak on the long wavelength side but does not include a peak on the short wavelength side, for example, a portion in a wavelength range of 500 nm or more. is there. The boundary between the short wavelength side xbar1 (lambda) and the long wavelength side xbar2 (lambda) is, for example, 490 nm or more and 510 nm or less.

3. Modified Color Matching Function The modified color matching function has an x component xbar (lambda), a y component ybar (lambda), and a z component zbar (lambda), like the CIE1931XYZ color matching function. The x component xbar (lambda) of the modified color matching function can be divided into a short wavelength side xbar1 (lambda) and a long wavelength side xbar2 (lambda), similarly to that of the CIE1931XYZ color matching function.

4 Comparison of CIE1931XYZ color-matching function and modified color-matching function The modified color-matching function is significantly different from the CIE1931XYZ color-matching function in the wavelength range of 500 nm or less, especially in the wavelength range of 400 nm to 500 nm. In the wavelength range, it is not significantly different from the CIE1931XYZ color matching function.

  For this reason, the short wavelength side xbar1 (lambda) of the x component xbar (lambda) of the modified color matching function having a large relative intensity in the wavelength range of 500 nm or less is significantly different from that of the CIE1931XYZ color matching function. Further, the z component zbar (lambda) of the modified color matching function having a large relative intensity in the wavelength range of 500 nm or less is significantly different from that of the CIE 1931 XYZ color matching function.

  However, the x component xbar (lambda) on the long wavelength side xbar2 (lambda) of the modified color matching function, which does not have a large value in the wavelength range of 500 nm or less, is not significantly different from that of the CIE1931XYZ color matching function. Further, the y component ybar (lambda) of the modified color matching function, which does not have a large value in the wavelength range of 500 nm or less, is not significantly different from that of the CIE1931XYZ color matching function.

  These are described using Vos and Judd (1978) modified color matching function and TR-170-1 modified color matching function as examples.

  The graph of FIG. 2 shows the Vos and Judd (1978) modified color matching function and the CIE 1931XYZ color matching function. The graph of FIG. 3 shows the TR-170-1 modified color matching function and the CIE1931XYZ color matching function.

  As shown in FIG. 2, the portion xbar1 (lambda) in the wavelength range from 380 nm to 500 nm of the x component xbar (lambda) of the Vos and Judd (1978) modified color matching function is significantly different from that of the CIE1931 XYZ color matching function. In contrast, the z component zbar (lambda) of the Vos and Judd (1978) modified color matching function is significantly different from that of the CIE 1931 XYZ color matching function.

  However, as shown in FIG. 2, the part xbar2 (lambda) in the wavelength region from 500 nm to 780 nm of the x component xbar (lambda) of the Vos and Judd (1978) modified color matching function is different from that of the CIE1931XYZ color matching function. There is no significant difference, and the y component ybar (lambda) of the Vos and Judd (1978) modified color matching function is not significantly different from that of the CIE1931XYZ color matching function.

  As shown in FIG. 3, the same can be said for the TR-170-1 modified color matching function.

5. Part Used for Deriving Colorimetric Values In the following description, it is assumed that one of the color matching functions A and B is a CIE1931XYZ color matching function, and the other of the color matching functions A and B is a modified color matching function. In the following description, the x component xbar (lambda), y are used as a first part, a second part, and a third part necessary to derive a colorimetric value when the color matching function A is selected. A fourth part and a fifth part necessary to derive a colorimetric value when the component ybar (lambda) and the z component zbar (lambda) are extracted from the color matching function A and the color matching function B is selected. And a sixth component, x-component xbar (lambda), y-component ybar (lambda) and z-component zbar (lambda) are extracted from the color matching function B, respectively. The colorimetric value when the color matching function A is selected can be derived from the first part, the second part, and the third part, and the colorimetric value when the color matching function B is selected is the fourth part. , The extraction positions of the first part, the second part, and the third part from the color matching function A may be changed as long as they can be derived from the part, the fifth part, and the sixth part. The locations where the fourth, fifth, and sixth portions are extracted from the color function B may be changed. For example, as the first part, the second part, and the third part, the x component xbar (lambda), the long wavelength side xbar2 (lambda), the y component ybar (lambda), and the z component zbar (lambda) are color matching functions, respectively. Extracted from A, the fourth component, the fifth component and the sixth component are respectively x component xbar (lambda) long wavelength side xbar2 (lambda), y component ybar (lambda) and z component zbar (lambda) It may be extracted from the color matching function B. The long wavelength side xbar2 (lambda) of the x component xbar (lambda) can be used instead of the x component xbar (lambda) because the short wavelength side xbar1 (lambda) of the x component xbar (lambda) is the z component zbar ( This is because it can be approximated by a coefficient multiplication of (lambda).

6. Color Luminance Meter The schematic diagram of FIG. 4 shows a color luminance meter 1000 of this embodiment.

  The color luminance meter 1000 measures the color of the display surface of the liquid crystal display. The color luminance meter 1000 may measure the color of the display surface of a flat panel display other than the liquid crystal display. The color luminance meter 1000 may measure the color of a luminescent material other than the flat panel display. The color luminance meter 1000 may measure the color of a non-luminous object.

The color luminance meter 1000 measures luminance and chromaticity in the Yxy color system. The color luminance meter 1000 may measure other colorimetric values in place of the luminance and chromaticity in the Yxy color system, or in addition to the luminance and chromaticity in the Yxy color system. For example, the color luminance meter 1000 is a lightness index and a chromaticness index in the L ^* a ^* b ^* color system, a lightness index in the L ^* C ^* h color system, saturation and hue angle, a hue in the Munsell color system, Lightness and saturation, a lightness index and a chromaticness index in the L ^* u ^* v ^* color system, a stimulus value in the XYZ color system, a stimulus value in the RGB color system, a color temperature, and the like may be measured. The color luminance meter 1000 may measure the color difference. The measurement of the luminance may be omitted.

  Depending on the measurement target, the measured colorimetric value, the measurement accuracy, and the like, the device may be called by a name other than the color luminance meter. For example, the device may be called a colorimeter, a color illuminometer, a color reader, or the like. In this application, a device for measuring a colorimetric value is generally referred to as a colorimeter.

  The color luminance meter 1000 is a kind of stimulus value direct reading type colorimeter that measures colorimetric values by a stimulus value direct reading method.

  As shown in FIG. 4, the color luminance meter 1000 includes a measurement probe 1010 and a measuring instrument main body 1011.

  The measurement probe 1010 is arranged in a measurement posture in front of the display surface 1030 of the liquid crystal display 1020 when measurement is performed. When the measurement probe 1010 is arranged as such, the measurement probe 1010 faces the display surface 1030, and the measurement light emitted from the display surface 1030 is received by the measurement probe 1010.

  When detecting that the operation has been performed, the measuring device main body 1011 transmits a control signal to the measurement probe 1010 to cause the measurement probe 1010 to perform a process corresponding to the detected operation. When receiving the control signal, the measurement probe 1010 performs processing in accordance with the control signal, detects the intensities of the X, Y, and Z components of the measured light, and detects the X, Y, and Z components of the measured light. Primary signal values V1 (X), V1 (Y), and V1 (Z) representing the component intensities are output to the measuring instrument main body 1011. When the primary signal values V1 (X), V1 (Y) and V1 (Z) are input, the measuring instrument main body 1011 converts the primary signal values V1 (X), V1 (Y) and V1 (Z). The chromaticities x and y are derived, and the chromaticities x and y are displayed. The measurement probe 1010 may perform all or a part of the functions of the measuring instrument main body 1011. The measuring device main body 1011 may perform a part of the function of the measurement probe 1010. When the measurement probe 1010 performs all the functions of the measuring instrument main body 1011, the measuring instrument main body 1011 may be omitted and the measuring probe 1010 may be a stand-alone. The measurement probe 1010 may be called a measurement head, a sensor head, or the like.

7 Measurement Probe The schematic diagram of FIG. 5 shows the optical system of the measurement probe 1010. The schematic diagram of FIG. 6 shows the electrical system of the measurement probe 1010 and the measuring instrument main body 1011.

  As shown in FIGS. 5 and 6, the measurement probe 1010 includes a correction color filter 1040, a switching mechanism 1041, an objective optical system 1042, a branch optical system 1043, a colorimetric optical system group 1044, a signal processing circuit 1045, and the like. The switching mechanism 1041 arranges the correction color filter 1040 at the non-correction position 1050 or the correction position 1051 according to the received switching signal. The switching mechanism 1041 is an automatic mechanism including a driving force source such as a motor and an actuator that generates a driving force necessary to move the correction color filter 1040. The switching mechanism 1041 may be a manual mechanism that does not include the driving force source.

  When the correction color filter 1040 is arranged at the non-correction position 1050, the measured light 1060 is converged by the objective optical system 1042, is branched into three by the branch optical system 1043, and is received by the colorimetric optical system group 1044. You. Thus, the colorimetric optical system group 1044 receives a light beam that does not pass through the correction color filter 1040. When the correction color filter 1040 is arranged at the correction position 1051, the light under measurement 1060 passes through the correction color filter 1040, is converged by the objective optical system 1042, is branched into three by the branch optical system 1043, and is colorimetrically measured. The light is received by the optical system group 1044. Accordingly, the colorimetric optical system group 1044 receives the light beam transmitted through the correction color filter 1040. The measured light 1060 may be diverged or collimated by the objective optical system 1042. The measured light 1060 may pass through an optical system other than the objective optical system 1042 and the branch optical system 1043. In some cases, both or one of the objective optical system 1042 and the branch optical system 1043 may be omitted.

  The colorimetric optical system group 1044 outputs the signals S (Xa), S (Ya), and S (Za) when receiving a light beam that does not pass through the correction color filter 1040, and outputs the light beams transmitted through the correction color filter 1040. When a bundle is received, it outputs signals S (Xb), S (Yb) and S (Zb). The intensity of the signals S (Xa), S (Ya) and S (Za) depends on the spectral intensity of the measured light 1060. The spectral responsivity indicating the relationship between the spectral intensity of the measured light 1060 and the intensities of the signals S (Xa), S (Ya) and S (Za) approximates the color matching function A. The intensity of the signals S (Xb), S (Yb) and S (Zb) depends on the spectral intensity of the measured light 1060. The spectral responsivity indicating the relationship between the spectral intensity of the measured light 1060 and the intensity of the signals S (Xb), S (Yb) and S (Zb) approximates the color matching function B.

  When the signals S (Xa), S (Ya), and S (Za) are input, the signal processing circuit 1045 processes the signals S (Xa), S (Ya), and S (Za), and processes the signal S ( Xa), S (Ya) and S (Za) to obtain primary signal values V1 (Xa), V1 (Ya) and V1 (Za), respectively, and obtain primary signal values V1 (Xa), V1 ( Ya) and V1 (Za) are transmitted to the measuring instrument main body 1011. When the signals S (Xb), S (Yb) and S (Zb) are input, the signal processing circuit 1045 processes the signals S (Xb), S (Yb) and S (Zb), and Obtain primary signal values V1 (Xb), V1 (Yb) and V1 (Zb) representing the intensities of S (Xb), S (Yb) and S (Zb), respectively, and obtain primary signal values V1 (Xb), V1 (Yb) and V1 (Zb) are transmitted to the measuring instrument main body 1011.

8 Uncorrected Position and Corrected Position The corrected position 1051 is on the optical path of the measured light 1060 and between the entrance of the measured light 1060 and the objective optical system 1042. Therefore, when the correction color filter 1040 is at the correction position 1051, the measured light 1060 passes through the correction color filter 1040 in a section from the entrance of the measured light 1060 to the objective optical system 1042. As long as the correction position 1051 is on the optical path of the measured light 1060, the correction position 1051 may be changed. For example, the correction position 1051 may be changed between the objective optical system 1042 and the branch optical system 1043, between the branch optical system 1043 and the colorimetric optical system group 1044, inside the colorimetric optical system group 1044, or the like. . However, when the branch optical system 1043 is provided, the correction position 1051 is desirably between the entrance of the measured light 1060 and the branch optical system 1043. Thus, one correction color filter 1040 is sufficient. When the correction color filter 1040 is an interference filter, the correction position 1051 is preferably at a position where the light beam becomes a parallel light beam. This suppresses wavelength shift due to oblique incidence, influence of polarized light, and the like.

  The uncorrected position 1050 is outside the optical path of the measured light 1060. The non-correction position 1050 may be inside the color luminance meter 1000 or outside the color luminance meter 1000. Therefore, when the correction color filter 1040 is disposed at the non-correction position 1050, the correction color filter 1040 may be moved inside the color luminance meter 1000 or may be removed from the color luminance meter 1000. When the correction color filter 1040 is removed from the color luminance meter 1000, for example, a holder that holds the correction color filter 1040 at the correction position 1051 is provided inside the color luminance meter 1000, and the correction color filter 1040 is removed from the holder. The correction color filter 1040 is retracted out of the optical path.

9. Colorimetric Optical System Group The colorimetric optical system group 1044 includes colorimetric optical systems 1070, 1071 and 1072. The colorimetric optical systems 1070, 1071 and 1072 are provided with condenser lens groups 1080, 1081 and 1082, respectively, with color filters 1090, 1091 and 1092, respectively, and with light receiving sensors 1100, 1101 and 1102, respectively.

  When the colorimetric optical system group 1044 receives the light beam, each of the colorimetric optical systems 1070, 1071 and 1072 receives the light beam that is branched into three by the branch optical system 1043 such as a bundle fiber. Light beams received by the colorimetric optical systems 1070, 1071 and 1072 are condensed by condensing lens groups 1080, 1081 and 1082, respectively, and transmitted through color filters 1090, 1091 and 1092, respectively, and received by light receiving sensors 1100 and 1101, respectively. And 1102. In some cases, the condenser lens groups 1080, 1081, and 1082 may be omitted.

  When the correction color filter 1040 is located at the non-correction position 1050, the light receiving sensor 1100 receives a light beam that does not pass through the correction color filter 1040, outputs a signal S (Xa), and outputs the signal S (Xa). When it is arranged at 1051, it receives the light beam transmitted through the correction color filter 1040 and outputs a signal S (Xb). The intensity of the signal S (Xa) depends on the spectral intensity of the measured light 1060. The intensity of the signal S (Xb) depends on the spectral intensity of the measured light 1060. The spectral responsivity indicating the relationship between the spectral intensity of the measured light 1060 and the intensity of the signal S (Xa) approximates the x component xbar (lambda) of the color matching function A. The spectral responsivity indicating the relationship between the spectral intensity of the measured light 1060 and the intensity of the signal S (Xb) approximates the x component xbar (lambda) of the color matching function B.

  When the correction color filter 1040 is located at the non-correction position 1050, the light receiving sensor 1101 receives a light beam that does not pass through the correction color filter 1040, outputs a signal S (Ya), and outputs the signal S (Ya). When it is arranged at 1051, it receives the light beam transmitted through the correction color filter 1040 and outputs a signal S (Yb). The intensity of the signal S (Ya) depends on the spectral intensity of the measured light 1060. The intensity of the signal S (Yb) depends on the spectral intensity of the measured light 1060. The spectral responsivity indicating the relationship between the spectral intensity of the measured light 1060 and the intensity of the signal S (Ya) approximates the y component ybar (lambda) of the color matching function A. The spectral responsivity indicating the relationship between the spectral intensity of the measured light 1060 and the intensity of the signal S (Yb) approximates the y component ybar (lambda) of the color matching function B.

  When the correction color filter 1040 is located at the non-correction position 1050, the light receiving sensor 1102 receives a light beam that does not pass through the correction color filter 1040, outputs a signal S (Za), and outputs the signal S (Za). When it is arranged at 1051, it receives the light beam transmitted through the correction color filter 1040 and outputs a signal S (Zb). The signal S (Za) intensity depends on the spectral intensity of the measured light 1060. The intensity of the signal S (Zb) depends on the spectral intensity of the measured light 1060. The spectral responsivity indicating the relationship between the spectral intensity of the measured light 1060 and the intensity of the signal S (Za) approximates the z component zbar (lambda) of the color matching function A. The spectral responsivity indicating the relationship between the spectral intensity of the measured light 1060 and the intensity of the signal S (Zb) approximates the z component zbar (lambda) of the color matching function B.

  When the correction color filter 1040 is arranged at the non-correction position 1050, all of the colorimetric optical systems 1070, 1071 and 1072 receive a light beam that does not pass through the correction color filter 1040, and the correction color filter 1040 is positioned at the correction position 1051. When arranged, all of the colorimetric optical systems 1070, 1071 and 1072 receive the light beam transmitted through the correction color filter 1040. However, when the correction color filter 1040 is arranged at the correction position 1051, only a part of the colorimetric optical systems 1070, 1071 and 1072 may receive the light beam transmitted through the correction color filter 1040. For example, when the y component of the color matching function B is not significantly different from the y component of the color matching function A, only the colorimetric optical systems 1070 and 1072 correct when the correction color filter 1040 is disposed at the correction position 1051. The light beam transmitted through the color filter 1040 may be received.

  When the correction position 1051 is inside the colorimetric optical system group 1044, the correction position 1051 is between the condenser lens groups 1080, 1081 and 1082 and the color filters 1090, 1091 and 1092, and the color filters 1090 and 1091. , 1092 and the light receiving sensors 1100, 1101, and 1102.

10 Spectral Transmittance of Color Filter FIG. 7 shows the spectral transmittance of the color filter, the spectral transmittance of the objective optical system, the spectral transmittance of the branch optical system, the spectral transmittance of the condenser lens group, and the spectral sensitivity of the light receiving sensor. And the overall spectral responsivity.

  As shown in FIG. 7, the transmittance of the objective optical system, the transmittance of the branch optical system, the transmittance of the condenser lens group, and the sensitivity of the light receiving sensor depend on the wavelength. The overall spectral responsivity, which indicates the relationship with the intensity of the signal output by the sensor, is not determined solely by the spectral transmittance of the color filter, but rather the spectral transmittance of the objective optical system, the spectral transmittance of the branching optical system, and the condenser lens group. Is affected by the spectral transmittance. For example, the overall spectral responsivity is affected by the spectral transmittance of the lens forming the objective optical system, the spectral transmittance of the optical fiber forming the branching optical system, and the like. When the measured light passes through an optical system other than the objective optical system, the branch optical system, and the condenser lens group, the overall spectral responsivity is also affected by the spectral transmittance of the optical system. The overall spectral responsivity may be affected by other factors. For example, the overall spectral responsivity may be affected by the spectral reflectance of the light receiving surface of the light receiving sensor.

  The spectral transmittance of the color filter 1090 is not selected so that the spectral transmittance itself of the color filter 1090 approximates the x component xbar (lambda) of the color matching function A, but the spectral response of the entire color matching function is The x component of A is chosen to approximate xbar (lambda). That is, the spectral transmittance of the color filter 1090 is determined by the spectral responsivity indicating the relationship between the spectral intensity of the measured light 1060 incident on the color luminance meter 1000 and the intensity of the signal S (Xa) output by the colorimetric optical system 1070. It is selected to approximate the x-component xbar (lambda) of the color matching function A. Similarly, the spectral transmittance of the color filter 1091 is a spectral responsivity indicating the relationship between the spectral intensity of the measured light 1060 incident on the color luminance meter 1000 and the intensity of the signal S (Ya) output from the colorimetric optical system 1071. Is selected to approximate the y component ybar (lambda) of the color matching function A. The spectral transmittance of the color filter 1092 is such that the spectral responsivity indicating the relationship between the spectral intensity of the measured light 1060 incident on the color luminance meter 1000 and the intensity of the signal S (Za) output from the colorimetric optical system 1072 is equal. It is chosen to approximate the z-component ybar (lambda) of function A.

  Each of the color filters 1090, 1091 and 1092 may be a laminate of a plurality of absorption filters, may be an interference filter, or may be a combination of an absorption filter and an interference filter. The material of the interference film constituting the interference filter is a dielectric, for example, an oxide.

11 Spectral Transmittance of Correcting Color Filter The spectral transmittance of the correcting color filter 1040 is measured light incident on the color luminance meter 1000 after the spectral transmittances of the color filters 1090, 1091 and 1092 are selected as described above. The spectral responsivity indicating the relationship between the spectral intensity of 1060 and the intensity of the signal S (Xb) output from the colorimetric optical system 1070 approximates the y component xbar (lambda) of the color matching function B, and enters the color luminance meter 1000. The spectral responsivity indicating the relationship between the spectral intensity of the measured light 1060 and the intensity of the signal S (Yb) output from the colorimetric optical system 1071 approximates the y component ybar (lambda) of the color matching function B, and the color luminance The spectral responsivity indicating the relationship between the spectral intensity of the measured light 1060 incident on the meter 1000 and the intensity of the signal S (Zb) output from the colorimetric optical system 1072 approximates the z component ybar (lambda) of the color matching function B. To be selected.

  The graph of FIG. 8 shows the spectral transmittance of the correction color filter 1040 when the color matching function A is the Vos and Judd corrected color matching function and the color matching function B is the CIE1931XYZ color matching function. The graph of FIG. 9 shows the spectral transmittance of the correction color filter 1040 shown in FIG. 8 multiplied by the Vos and Judd modified color matching function and the CIE1931XYZ color matching function.

  As shown in FIG. 9, the product obtained by multiplying the spectral transmittance of the correction color filter 1040 shown in FIG. 8 by the Vos and Judd modified color matching function does not have a great difference from the CIE 1931XYZ color matching function. This means that when the correction color filter 1040 has the spectral transmittance shown in FIG. 8, when the correction color filter 1040 is arranged at the correction position 1051, the colorimetric optical system group 1044 approximates the CIE1931XYZ color matching function. It has a spectral responsivity.

  The spectral transmittance of the correction color filter 1040 is basically a quotient obtained by dividing the color matching function B by the color matching function A. For example, the x component xbar (lambda) of the color matching function B The first quotient divided by the component xbar (lambda), the second quotient of the y component ybar (lambda) of the color matching function B divided by the y component ybar (lambda) of the color matching function A, and the color matching function B Is divided by the z component zbar (lambda) of the color matching function A and the third quotient of the z component zbar (lambda) of the color matching function A. However, it is also allowed to consider only the wavelength range where the influence on the colorimetric value is relatively large and not consider the wavelength range where the influence on the colorimetric value is relatively small. It is also permissible to consider only components that have a relatively large effect on colorimetric values and not consider components that have a relatively small effect on colorimetric values. For example, in view of the fact that the ratio of the peak size of the short wavelength side xbar1 (lambda) and the long wavelength side xbar2 (lambda) of the x component xbar (lambda) to the colorimetric value has a large effect, May be considered as the spectral transmittance of the correction color filter 1040. In addition, in the wavelength range of 500 nm or less, the third quotient is used as the spectral transmittance of the correction color filter 1040, and in the wavelength range of 500 nm or more, the average of the first quotient and the second quotient is used as the correction color filter. A spectral transmittance of 1040 is also conceivable.

  The graph of FIG. 10 shows a quotient obtained by dividing the CIE1931XYZ color matching function by the Vos and Judd modified color matching function. The spectral transmittance of the correction color filter 1040 shown in FIG. 8 is obtained by dividing the x component xbar (lambda) of the CIE1931XYZ color matching function shown in FIG. 10 by the x component xbar (lambda) of the Vos and Judd modified color matching function. However, on the long wavelength side where the influence on the colorimetric value is relatively small, it takes a constant value regardless of the quotient.

  The correction color filter 1040 may also be a laminate of a plurality of absorption filters, an interference filter, or a combination of an absorption filter and an interference filter.

12 Signal Processing Circuit As shown in FIG. 6, the signal processing circuit 1045 includes amplification circuits 1110, 1111 and 1112, analog / digital converters 1120, 1121 and 1122, and the like. Depending on the specifications of the light receiving sensors 1100, 1101 and 1102 and the analog / digital converters 1120, 1121 and 1122, the amplifier circuits 1110, 1111 and 1112 may be omitted.

  When the signals S (Xa), S (Ya) and S (Za) are input to the signal processing circuit 1045, the amplifier circuits 1110, 1111 and 1112 respectively output the signals S (Xa), S (Ya) and S (Za). ) And the analog / digital converters 1120, 1121 and 1122 respectively convert the amplified signals S (Xa), S (Ya) and S (Za) into primary signal values V1 (Xa), V1 (Ya) and Convert to V1 (Za). When the signals S (Xb), S (Yb) and S (Zb) are input to the signal processing circuit 1045, the amplifier circuits 1110, 1111 and 1112 respectively output the signals S (Xb), S (Yb) and S (Zb). ), And the analog / digital converters 1120, 1121 and 1122 respectively convert the amplified signals S (Xb), S (Yb) and S (Zb) into primary signal values V1 (Xb), V1 (Yb) and Convert to V1 (Zb).

13 Measuring Instrument Main Body The measuring instrument main body 1011 includes an embedded computer 1130, an operation section 1131, and a display section 1132. The embedded computer 1130 performs the following functions by executing the installed firmware. Hardware without software may perform all or a part of the following functions. The display unit 1132 is a display, a lamp, a printer, or the like. The operation unit 1131 is a keyboard, a pointing device, a touch panel, a switch, a dial, and the like.

  When detecting that an operation has been performed on the operation unit 1131, the embedded computer 1130 performs processing according to the detected operation.

  When receiving the primary signal values V1 (Xa), V1 (Ya) and V1 (Za), the embedded computer 1130 converts the chromaticities xa and ya when the color matching function A is selected into the primary signal values V1. Calculate from (Xa), V1 (Ya) and V1 (Za), display chromaticity xa and ya on the display unit 1132 and receive the primary signal values V1 (Xb), V1 (Yb) and V1 (Zb) Then, the chromaticities xb and yb when the color matching function B is selected are calculated from the primary signal values V1 (Xb), V1 (Yb) and V1 (Zb), and the chromaticities xb and yb are displayed on the display unit. 1132 is displayed. The embedded computer 1130 calculates the luminance Lv from the primary signal value V1 (Ya) or V1 (Yb), and causes the display unit 1132 to display the luminance Lv. The luminance Lv is preferably calculated from a signal value representing the intensity of a signal output by a spectral colorimetric system having a spectral response close to the y component of the CIE1931XYZ color matching function.

14. Chromaticity Calculation Algorithm The block diagram in FIG. 11 is a diagram for describing a chromaticity calculation algorithm.

  The mode setting unit 1140, the calibration units 1141 and 1142, and the chromaticity calculation units 1143 and 1144 shown in FIG.

  The mode setting unit 1140 specifies a mode based on an operation performed on the operation unit 1131, and sets the color luminance meter 1000 to mode 1 or mode 2. The color luminance meter 1000 may have a mode other than the mode 1 and the mode 2. When the color luminance meter 1000 is set to the mode 1, the mode setting unit 1140 transmits to the switching mechanism 1041 a switching signal that causes the switching mechanism 1041 to perform an operation of arranging the correction color filter 1040 at the non-correction position 1050. When the luminance meter 1000 is set to the mode 2, a switching signal for causing the switching mechanism 1041 to perform an operation of arranging the correction color filter 1040 at the correction position 1051 is transmitted to the switching mechanism 1041. Whether the correction color filter 1040 is located at the non-correction position 1050 or the correction position 1051 is detected, and when the correction color filter 1040 is located at the non-correction position 1050, the mode 1 is selected. Mode 2 may be selected when 1040 is located at the correction position 1051.

  When the mode setting unit 1140 sets the color luminance meter 1000 to mode 1, the chromaticity is calculated from the primary signal values V1 (Xa), V1 (Ya) and V1 (Za) by the calibration unit 1141 and the chromaticity calculation unit 1143. xa and ya are calculated.

  When the mode setting unit 1140 sets the color luminance meter 1000 to mode 2, the chromaticity is calculated from the primary signal values V1 (Xb), V1 (Yb) and V1 (Zb) by the calibration unit 1142 and the chromaticity calculation unit 1144. xb and yb are calculated.

  The calibration unit 1141 multiplies each of the primary signal values V1 (Xa), V1 (Ya), and V1 (Za) by a calibration coefficient corresponding to the color matching function A, thereby obtaining the primary signal values V1 (Xa), V1 ( Ya) and V1 (Za) are calibrated to obtain secondary signal values V2 (Xa), V2 (Ya) and V2 (Za). Accordingly, the relative relationship between the spectral responsivity of the colorimetric optical system 1070, the spectral responsivity of the colorimetric optical system 1071 and the spectral responsivity of the colorimetric optical system 1072 is determined by the x component xbar (lambda) of the color matching function A. , Even if the relative relationship between the y component ybar (lambda) of the color matching function A and the z component zbar (lambda) of the color matching function A does not match, the x component xbar (lambda) of the color matching function A, the color matching function Secondary signal values V2 (Xa), V2 (Ya) and V2 (Za) reflecting the relative relationship between the y component ybar (lambda) of A and the z component zbar (lambda) of the color matching function A are obtained. The secondary signal values V2 (Xa), V2 (Ya) and V2 (Za) are used as stimulus values Xa, Ya and Za.

  The calibration unit 1142 multiplies each of the primary signal values V1 (Xb), V1 (Yb), and V1 (Zb) by a calibration coefficient corresponding to the color matching function B, so that the primary signal values V1 (Xb), V1 ( Yb) and V1 (Zb) are calibrated to obtain secondary signal values V2 (Xb), V2 (Yb) and V2 (Zb). Accordingly, the relative relationship between the spectral responsivity of the colorimetric optical system 1070, the spectral responsivity of the colorimetric optical system 1071 and the spectral responsivity of the colorimetric optical system 1072 is determined by the x component xbar (lambda) of the color matching function B. , Even if the relative relationship between the y component ybar (lambda) of the color matching function B and the z component zbar (lambda) of the color matching function B does not match, the x component xbar (lambda) of the color matching function B, the color matching function Secondary signal values V2 (Xb), V2 (Yb) and V2 (Zb) reflecting the relative relationship between the y component ybar (lambda) of B and the z component zbar (lambda) of the color matching function B are obtained. The secondary signal values V2 (Xb), V2 (Yb) and V2 (Zb) are used as stimulus values Xb, Yb and Zb.

  Calibration may be performed by other than multiplying the primary signal value by the calibration coefficient. For example, calibration may be performed by adjusting the amplification factors of the amplifier circuits 1110, 1111 and 1112 according to the calibration coefficients. That is, analog signal calibration may be performed instead of digital signal value calibration. The calibration units 1141 and 1142 may be omitted. If the calibration units 1141 and 1142 are omitted, the primary signal values V1 (Xa), V1 (Ya) and V1 (Za) are used as the stimulus values Xa, Ya and Za, and the secondary signal values V2 (Xb) , V2 (Yb) and V2 (Zb) are used as stimulus values Xb, Yb and Zb.

  The chromaticity calculator 1143 calculates chromaticities xa and ya from the stimulus values Xa, Ya and Za.

  The chromaticity calculator 1144 calculates chromaticities xb and yb from the stimulus values Xb, Yb and Zb.

  The signal processing circuit 1045 and the embedded computer 1130 constitute a derivation mechanism 1150. The derivation mechanism 1150 derives the chromaticities xa and ya from the signals S (Xa), S (Ya) and S (Za) as a whole, and obtains the colors from the signals S (Xb), S (Yb) and S (Zb). Deriving the degrees xb and yb.

15 Flow of Measurement The flowchart of FIG. 12 shows a flow of measurement of chromaticity.

  In the color luminance meter 1000, when the built-in computer 1130 detects that the operation for instructing the start of the measurement is performed on the operation unit 1131, the built-in computer 1130 measures the control signal for causing the measurement probe 1010 to start the measurement. Transmit to probe 1010. This control signal is a measurement trigger that causes the measurement probe 1010 to start measurement.

  As shown in FIG. 12, embedded computer 1130 receives a measurement trigger at step 1160.

  The embedded computer 1130 confirms the mode in step 1161, and performs different processing according to the mode.

  When the embedded computer 1130 confirms that mode 1 is selected in step 1161, the embedded computer 1130 places the correction color filter 1040 at the non-correction position 1050 in step 1162, and in step 1163, the primary signal values V1 (Xa), V1 (Ya) and V1 (Za).

  When the embedded computer 1130 confirms that the mode 2 has been selected in Step 1162, the embedded computer 1130 places the correction color filter 1040 at the correction position 1051 in Step 1164, and in Step 1165, the primary signal values V1 (Xb), V1 ( Yb) and V1 (Zb) are obtained.

  Subsequently, the embedded computer 1130 confirms the mode in step 1166, and performs different processing according to the mode.

  When the embedded computer 1130 confirms that the mode 1 has been selected in step 1166, the embedded computer 1130 refers to the calibration coefficient A corresponding to the color matching function A in step 1167, and the primary signal values V1 (Xa), V1 ( Ya) and V1 (Za) are calibrated to obtain secondary signal values V2 (Xa), V2 (Ya) and V2 (Za), and in step 1168, secondary signal values V2 (Xa), V2 (Ya) and V2 Calculate chromaticities xa and ya from (Za) (stimulus values Xa, Ya and Za).

  When the embedded computer 1130 confirms that the mode 2 is selected in step 1166, in step 1169, the embedded computer 1130 refers to the calibration coefficient B corresponding to the color matching function B, and the primary signal values V1 (Xb), V1 ( Yb) and V1 (Zb) are calibrated to obtain secondary signal values V2 (Xb), V2 (Yb) and V2 (Zb), and in step 1170, the secondary signal values V2 (Xb), V2 (Yb) and V2 Calculate chromaticities xb and yb from (Zb) (stimulus values Xb, Yb and Zb).

  The embedded computer 1130 displays the chromaticity calculated in step 1171.

16. Example of Application in Illuminometer A correction color filter similar to the above-described correction color filter 1040 is also used in an illuminometer that is a type of colorimeter.

  The schematic diagram of FIG. 13 shows an illuminometer 2000.

  As shown in FIG. 13, in the illuminometer 2000, when the correction color filter 2010 is arranged at the non-correction position 2020, the measured light 2040 coming from the light source 2030 is transmitted by the diffusion plate 2011 which is an objective optical system. When the light is diffused and received by the colorimetric optical system group 2012 and the correction color filter 2010 is arranged at the correction position 2021, the measured light 2040 arriving from the light source 2030 is diffused by the diffusion plate 2011 and corrected. The light passes through the filter 2010 and is received by the colorimetric optical system group 2012.

17 Advantages of Stimulus Value Direct Reading Method over Spectral Colorimetry Method The colorimetry method is roughly classified into a spectral colorimetry method and a stimulus value direct reading method.

  When colorimetry is performed by a spectral colorimetry method, the light to be measured is spectrally separated by a spectral element such as a diffraction grating, and the intensity of each wavelength component is detected by a light receiving sensor array including a large number of light receiving sensors. A colorimetric value is calculated from the color function. According to the spectral colorimetric method, colorimetric values corresponding to each of a plurality of color matching functions are calculated from the same spectral spectrum. However, in the spectral colorimetric method, a complicated optical system such as a spectral element and a lens system having a high resolution and a high brightness is required, a large number of light receiving sensors are required, and the colorimeter is large and costly.

  On the other hand, when the colorimetry is performed by the stimulus value direct reading method, the light receiving sensor group generally includes three light receiving sensors and a spectral response approximating the color matching function. A stimulus value is detected by a color filter group including three color filters, and a colorimetric value is calculated from the stimulus value. According to the stimulus value direct reading method, a complicated optical system becomes unnecessary, a large number of light receiving sensors become unnecessary, and the colorimeter becomes small and low-cost. However, in the stimulus value direct reading method, a colorimetric value corresponding to each of a plurality of color matching functions cannot be calculated from the same stimulus value. To obtain colorimetric values corresponding to each of a plurality of color matching functions when colorimetry is performed by the stimulus value direct reading method, a color filter group corresponding to each of the plurality of color matching functions is required. Therefore, to obtain colorimetric values corresponding to each of the two color matching functions, two color filter groups are required, and six color filters are required.

  On the other hand, in the improved direct reading method of the stimulus value provided by this embodiment, four color filters are sufficient to obtain the colorimetric values corresponding to each of the two color matching functions.

  Therefore, according to the improved direct reading method of stimulus value provided by this embodiment, the colorimetric value corresponding to each of the plurality of color matching functions can be obtained by one stimulus value direct reading type colorimeter having a simple configuration. Measured.

18 Particularly Suitable Applications Devices using a white light emitting diode (LED) as a light source are widely used. For example, lighting fixtures using a white LED as a light source, liquid crystal displays, and the like are widely used. Many white LEDs excite a yellow phosphor with blue excitation light emitted by a blue LED, cause the yellow phosphor to emit yellow fluorescence, and obtain white light composed of a blue excitation light component and a yellow fluorescence component. Has been adopted.

  In the color evaluation of the light emitted from the white LED, the accuracy of measurement in a wavelength range from 400 nm to 500 nm to which the excitation light component belongs is important. The reason will be described.

  FIG. 14 is a graph showing the spectral intensity of light emitted from a white LED for each individual.

  Generally speaking, as shown in FIG. 14, the spectral intensity of the fluorescent component is relatively stable, while the spectral intensity of the excitation light component is relatively unstable. The spectral intensity of the excitation light component has an individual difference of about 10 nm for the peak wavelength, and about 10% for the peak intensity. In addition, the peak wavelength of the spectral intensity of the excitation light component varies by about 2 nm depending on the temperature, even for the same individual.

  In addition, while the peak of the spectral intensity of the fluorescent component is relatively gentle, the peak of the spectral intensity of the excitation light component is relatively steep.

  From these facts, in the color evaluation of the light emitted by the white LED, the effect of the measurement accuracy in the wavelength range from 400 nm to 500 nm to which the excitation light component belongs to the colorimetric value, in particular, the stimulation values X, Y, and Z The effect on our Z is great.

  For this reason, in the color evaluation of the light emitted from the white LED, it is important to select the z component of the color matching function, and a colorimetric value corresponding to the corrected color matching function having the z component that matches the human visual perception is obtained. There is a strong desire to be able to do so.

  On the other hand, there is a strong demand for obtaining a colorimetric value corresponding to the CIE1931XYZ color matching function, for example, when comparing with past measurement results.

  The CIE1931 XYZ colorimeter 1000 that can measure both the colorimetric value when the color matching function is selected and the colorimetric value when the corrected color matching function is selected can meet these demands. Particularly suitable for evaluating the color of emitted light.

  Although the present invention has been shown and described in detail, the above description is illustrative in all aspects and is not restrictive. Accordingly, it will be understood that numerous modifications and variations may be devised without departing from the scope of the invention.

1000 Color luminance meter 1010 Measurement probe 1011 Measuring instrument body

Claims (9)

A stimulus direct reading colorimeter that measures colorimetric values corresponding to a first color matching function and a second color matching function different from the first color matching function for a plurality of different objects to be measured. So,
One correction color filter,
A switching mechanism for arranging the correction color filter at a non-correction position or a correction position,
A first colorimetric optical system including a first colorimetric optical system, a second colorimetric optical system, and a third colorimetric optical system, wherein when the correction color filter is arranged at the non-correction position, The second colorimetric optical system and the third colorimetric optical system receive a light beam that does not pass through the correction color filter, and include a first part, a second part, and a first color matching function. Each of the correction color filters has a spectral responsivity close to the third portion, and outputs a first signal, a second signal, and a third signal according to the spectral intensity of the measured light. When disposed at a position, all or a part of the first colorimetric optical system, the second colorimetric optical system, and the third colorimetric optical system is a light beam transmitted through the correction color filter. And the first color measurement optical system, the second color measurement optical system, and the third color measurement optical system Fourth, fifth and sixth signals having spectral responsivities approximate to the fourth, fifth and sixth parts of the function, respectively, and corresponding to the spectral intensity of the measured light. Colorimetric optics that output
A first colorimetric value when the first color matching function is selected is derived from the first signal, the second signal, and the third signal, and the second color matching function is selected. A derivation mechanism for deriving a second colorimetric value in the case where the second colorimetric value is obtained from the fourth signal, the fifth signal, and the sixth signal;
With
A stimulus value direct-reading colorimeter in which a spectral transmittance of the correction color filter is a value obtained by dividing a second color matching function by a first color matching function. When the correction color filter is disposed at the correction position, all of the first color measurement optical system, the second color measurement optical system, and the third color measurement optical system perform the correction color filter. The stimulus value direct-reading colorimeter according to claim 1, which receives the transmitted light beam. The first colorimetric optical system includes:
A first color filter having a first spectral transmittance;
A first light receiving sensor that receives the light beam transmitted through the first color filter and outputs the first signal;
With
The second colorimetric optical system includes:
A second color filter having a second spectral transmittance;
A second light-receiving sensor that receives the light beam transmitted through the second color filter and outputs the second signal;
With
The third colorimetric optical system includes:
A third color filter having a third spectral responsivity;
A third light receiving sensor that receives the light beam transmitted through the third color filter and outputs the third signal;
The stimulus value direct reading type colorimeter according to claim 1 or 2. 4. The switching mechanism according to claim 1, wherein the switching mechanism is an automatic mechanism having a driving force source for generating a driving force necessary to move the correction color filter, or a manual mechanism not having the driving force source. Stimulus value direct reading type colorimeter. The derivation mechanism includes:
Processing the first signal, the second signal, the third signal, the fourth signal, the fifth signal, and the sixth signal, and processing the first signal, the second signal , A first primary signal value, a second primary signal value, and a third primary signal value representing the intensities of the third signal, the fourth signal, the fifth signal, and the sixth signal, respectively. A signal processing circuit for obtaining a next signal value, a fourth primary signal value, a fifth primary signal value, and a sixth primary signal value;
The first primary signal value, the second primary signal value, and the third primary signal value are calibrated by multiplying by a calibration coefficient corresponding to the first color matching function, and a first secondary signal value is calibrated. A first calibration unit for obtaining a signal value, a second secondary signal value, and a third secondary signal value;
The fourth primary signal value, the fifth primary signal value and the sixth primary signal value are calibrated by multiplying by a calibration coefficient corresponding to the second color matching function to obtain a fourth secondary signal value. A second calibration unit for obtaining a signal value, a fifth secondary signal value, and a sixth secondary signal value;
A first colorimetric value calculation unit that calculates the first colorimetric value from the first secondary signal value, the second secondary signal value, and the third secondary signal value;
A second colorimetric value calculation unit that calculates the second colorimetric value from the fourth secondary signal value, the fifth secondary signal value, and the sixth secondary signal value;
The stimulus value direct-reading type colorimeter according to any one of claims 1 to 4, further comprising: 6. The colorimeter of claim 1, wherein the correction color filter is a color absorption filter, an interference film filter, or a combination of a color absorption filter and an interference film filter. The first part is an x component of the first color matching function,
The second part is a y component of the first color matching function,
The third part is the z component of the first color matching function,
The fourth part is an x component of the second color matching function,
The fifth part is a y component of the second color matching function,
7. The colorimeter according to claim 1, wherein the sixth part is a z-component of the second color matching function.   One of the first color matching function and the second color matching function is a color matching function of the XYZ color system adopted in 1931 by the International Commission on Illumination, and the first color matching function and the second color matching function are the same. 8. The stimulus according to claim 1, wherein the other of the second color matching functions is a color matching function different from the color matching function of the XYZ color system adopted in 1931 by the International Commission on Illumination. Direct reading colorimeter.   9. The stimulus direct reading colorimeter according to claim 8, wherein the second color matching function is a Vos and Judd (1978) corrected color matching function or a TR-170-1 corrected color matching function.

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