Light metering device

Abstract

This photometric device (1) comprises a variable optical attenuator (4). The variable optical attenuator (4) comprises a plurality of optical attenuation filters and a drive device (5). Each of the plurality of optical attenuation filters comprises a multilayered interference film and a transparent substrate. Given two of the plurality of optical attenuation filters combined with each other are taken to be a first optical attenuation filter (optical attenuation filter (10)) and a second optical attenuation filter (optical attenuation filter (20)). A first optical path length of a first transparent substrate (transparent substrate (11)) of the first optical attenuation filter is different from a second optical path length of a second transparent substrate (transparent substrate (21)) of the second optical attenuation filter.

Description

[Technical Field]

[0001] The present disclosure relates to photometric devices. [Background technology]

[0002] Japanese Patent Laid-Open Publication No. 8-15012 (Patent Document 1) discloses an optical spectrum measuring device comprising a spectrometer, optical attenuation means, and an optical detector. The optical attenuation means includes a rotating plate, a plurality of ND filters attached to the rotating plate, and a motor for rotating the rotating plate. The plurality of ND filters have different optical attenuation rates. Depending on the intensity of light incident on the optical spectrum measuring device, the ND filter having the most appropriate optical attenuation rate is inserted into the optical path of the light. In this way, the optical detector is prevented from saturating, and the intensity of the light incident on the optical detector is kept within the dynamic range of the optical detector. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 8-15012 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the light attenuation means included in the optical spectrum measurement device disclosed in Patent Document 1 uses multiple ND filters attached to a rotating plate and a motor to rotate it, which increases the size of the light attenuation means. The present disclosure has been made in consideration of this problem, and its purpose is to provide a photometric device that is more compact in size and can measure light with higher accuracy. [Means for solving the problem]

[0005] The photometric device disclosed herein includes a variable optical attenuator and a photodetector. The variable optical attenuator includes multiple optical attenuation filters and a driving device. The photodetector receives light that has passed through the variable optical attenuator. The driving device can insert the multiple optical attenuation filters into and retract them from the optical axis independently of one another. The multiple optical attenuation filters are arranged at different positions along the optical axis. Each of the multiple optical attenuation filters includes an interference multilayer film and a transparent substrate that supports the interference multilayer film. A combination of any two of the multiple optical attenuation filters is referred to as a first optical attenuation filter and a second optical attenuation filter. In the direction along the optical axis, the second optical attenuation filter is closer to the photodetector than the first optical attenuation filter. The first optical attenuation filter includes a first interference multilayer film as the interference multilayer film and a first transparent substrate as the transparent substrate. The second optical attenuation filter includes a second interference multilayer film as the interference multilayer film and a second transparent substrate as the transparent substrate. The first optical path length of the first transparent substrate is different from the second optical path length of the second transparent substrate.

[0006] Preferably, the light has a distribution of angles of incidence on the variable optical attenuator, and the photometric device satisfies the following conditional expression (1): |OPD θmax1 -OPD θmin1 | / λ>0.5 …(1) However, OPD θmax1 =(OP 1220max -OP 1022max ) OPD θmin1 =(OP 1220min -OP 1022min ) where λ is the wavelength of light within the measurable wavelength range of the photometric device. 1220max is the optical path length of the maximum incident angle light that is reflected twice by the first optical attenuation filter and passes through the second optical attenuation filter without being reflected by the second optical attenuation filter. The maximum incident angle light is the light that has the largest incident angle to the variable optical attenuator. OP 1022max is the optical path length of the maximum incident angle light that passes through the first light attenuating filter without being reflected by the first light attenuating filter and is reflected twice by the second light attenuating filter. 1220minis the optical path length of the minimum incident angle light that is reflected twice by the first optical attenuation filter and passes through the second optical attenuation filter without being reflected by the second optical attenuation filter. The minimum incident angle light is the light that has the smallest incident angle to the variable optical attenuator. OP 1022min is the optical path length of the minimum incident angle light that passes through the first light attenuating filter without being reflected by the first light attenuating filter and is reflected twice by the second light attenuating filter.

[0007] Preferably, the photometric device is a spectroscope capable of measuring spectral information. Preferably, the photometric device satisfies the following conditional expression (2): OPD 12 ×(1 / λ-1 / (λ+Δλ a ))>0.5 …(2) However, OPD 12 =|OP 1220 -OP 1022 | λ is the wavelength of light within the measurable wavelength range of the photometric device. Δλ a is the half-width of the spectral responsivity spectrum of the photodetector element included in the photodetector. 1220 is the optical path length of light that is reflected twice by the first light attenuation filter and passes through the second light attenuation filter without being reflected by the second light attenuation filter. 1022 is the optical path length of light that passes through the first light attenuating filter without being reflected by the first light attenuating filter and is reflected twice by the second light attenuating filter.

[0008] Preferably, the photometric device satisfies the following conditional expression (3): OPD 13 ×(1 / λ-1 / (λ+Δλ b ))>0.5 …(3) However, OPD 13 =|OP 1220 -OP 1022 | λ is the wavelength of light within the measurable wavelength range of the photometric device. Δλ b is the line width of the light emitted from the object under test. 1220is the optical path length of light that is reflected twice by the first light attenuation filter and passes through the second light attenuation filter without being reflected by the second light attenuation filter. 1022 is the optical path length of light that passes through the first light attenuating filter without being reflected by the first light attenuating filter and is reflected twice by the second light attenuating filter.

[0009] Preferably, the first thickness of the first transparent substrate is different from the second thickness of the second transparent substrate. Preferably, the first refractive index of the first transparent substrate is different from the second refractive index of the second transparent substrate.

[0010] Preferably, the multilayer interference films of each of the plurality of light attenuation filters are made of the same material, and the transparent substrates of each of the plurality of light attenuation filters are made of the same material.

[0011] Preferably, the plurality of light-attenuating filters are each arranged at the same angle with respect to the optical axis.

[0012] Preferably, the photometric device further includes a collimating lens disposed on the incident side of the plurality of light attenuation filters.

[0013] Preferably, the photometric device satisfies the following conditions (4) and (5): |OPD θmax2 -OPD θmin2 | / λ>0.5 …(4) |OPD θmax3 -OPD θmin3 | / λ>0.5 …(5) However, OPD θmax2 =(OP 1420max -OP 1022max ) OPD θmin2 =(OP 1420min -OP 1022min ) OPD θmax3 =(OP 1024max -OP 1220max ) OPD θmin3 =(OP 1024min -OP 1220min ) OP 1420max The first light attenuating filter OP is the optical path length of the maximum incident angle light that is reflected four times by the second optical attenuation filter and passes through the second optical attenuation filter without being reflected by the second optical attenuation filter. 1022max is the optical path length of the maximum incident angle light that passes through the first light attenuating filter without being reflected by the first light attenuating filter and is reflected twice by the second light attenuating filter. 1420min is the optical path length of the minimum incident angle light that is reflected four times by the first light attenuation filter and passes through the second light attenuation filter without being reflected by the second light attenuation filter. 1022min is the optical path length of the minimum incident angle light that passes through the first light attenuating filter without being reflected by the first light attenuating filter and is reflected twice by the second light attenuating filter. 1024max is the optical path length of the maximum incident angle light that passes through the first light attenuating filter without being reflected by the first light attenuating filter and is reflected four times by the second light attenuating filter. 1220max is the optical path length of the maximum incident angle light that is reflected twice by the first light attenuation filter and passes through the second light attenuation filter without being reflected by the second light attenuation filter. 1024min is the optical path length of the minimum incident angle light that passes through the first light attenuating filter without being reflected by the first light attenuating filter and is reflected four times by the second light attenuating filter. 1220min is the optical path length of the minimum incident angle light that is reflected twice by the first light attenuation filter and passes through the second light attenuation filter without being reflected by the second light attenuation filter.

[0014] Preferably, the photometric device satisfies the following conditions (6) and (7): OPD 21 ×(1 / λ-1 / (λ+Δλ a ))>0.5 …(6) OPD 22 ×(1 / λ-1 / (λ+Δλ a ))>0.5 …(7) However, OPD 21 =|OP 1420 -OP 1022 | OPD 22 =|OP 1024 -OP 1220 |OP 1420is the optical path length of light that is reflected four times by the first light attenuation filter and passes through the second light attenuation filter without being reflected by the second light attenuation filter. 1022 is the optical path length of light that passes through the first light attenuating filter without being reflected by the first light attenuating filter and is reflected twice by the second light attenuating filter. 1024 is the optical path length of light that passes through the first light attenuation filter without being reflected by the first light attenuation filter and is reflected four times by the second light attenuation filter. 1220 is the optical path length of light that is reflected twice by the first light attenuation filter and passes through the second light attenuation filter without being reflected by the second light attenuation filter.

[0015] Preferably, the photometric device satisfies the following conditions (8) and (9): OPD 21 ×(1 / λ-1 / (λ+Δλ b ))>0.5 …(8) OPD 22 ×(1 / λ-1 / (λ+Δλ b ))>0.5 …(9) However, OPD 21 =|OP 1420 -OP 1022 | OPD 22 =|OP 1024 -OP 1220 |OP 1420 is the optical path length of light that is reflected four times by the first light attenuation filter and passes through the second light attenuation filter without being reflected by the second light attenuation filter. 1022 is the optical path length of light that passes through the first light attenuating filter without being reflected by the first light attenuating filter and is reflected twice by the second light attenuating filter. 1024 is the optical path length of light that passes through the first light attenuation filter without being reflected by the first light attenuation filter and is reflected four times by the second light attenuation filter. 1220 is the optical path length of light that is reflected twice by the first light attenuation filter and passes through the second light attenuation filter without being reflected by the second light attenuation filter.

[0016] Preferably, the plurality of light attenuation filters include a third light attenuation filter as the first light attenuation filter and a fourth light attenuation filter as the second light attenuation filter. The third light attenuation filter and the fourth light attenuation filter are any two light attenuation filters adjacent to each other among the plurality of light attenuation filters. The photometric device satisfies the following conditional expressions (10) and (11). |OPD θmax4 -OPD θmin4 | / λ>0.5 …(10) |OPD θmax5 -OPD θmin5 | / λ>0.5 …(11) However, OPD θmax4 =(OP 3240max -OP 30G240max ) OPD θmin4 =(OP 3240min -OP 30G240min ) OPD θmax5 =(OP 3042max -OP 30G240max ) OPD θmin5 =(OP 3042min -OP 30G240min ) OP 3240max is the optical path length of the maximum incident angle light that is reflected twice by the third light attenuation filter and passes through the fourth light attenuation filter without being reflected by the fourth light attenuation filter. 30G240max is the optical path length of the maximum incident angle light that passes through the third and fourth light attenuation filters without being reflected by them and is reflected twice by the layer between the third and fourth light attenuation filters. 3240min is the optical path length of the minimum incident angle light that is reflected twice by the third light attenuation filter and passes through the fourth light attenuation filter without being reflected by the fourth light attenuation filter. 30G240min is the optical path length of the minimum incident angle light that passes through the third and fourth light attenuation filters without being reflected by them and is reflected twice by the layer between the third and fourth light attenuation filters. 3042max is the optical path length of the maximum incident angle light that passes through the third light attenuation filter without being reflected by the third light attenuation filter and is reflected twice by the fourth light attenuation filter.3042min is the optical path length of the minimum incident angle light that passes through the third light attenuation filter without being reflected by the third light attenuation filter and is reflected twice by the fourth light attenuation filter.

[0017] Preferably, the plurality of light attenuation filters include a third light attenuation filter as the first light attenuation filter and a fourth light attenuation filter as the second light attenuation filter. The third light attenuation filter and the fourth light attenuation filter are any two light attenuation filters adjacent to each other among the plurality of light attenuation filters. The photometric device satisfies the following conditional expressions (12) and (13). OPD g1 ×(1 / λ-1 / (λ+Δλ a ))>0.5 …(12) OPD g2 ×(1 / λ-1 / (λ+Δλ a ))>0.5 …(13) However, OPD g1 =|OP 3240 -OP 30G240 | OPD g2 =|OP 3042 -OP 30G240 |OP 3240 is the optical path length of light that is reflected twice by the third optical attenuation filter and passes through the fourth optical attenuation filter without being reflected by the fourth optical attenuation filter. 30G240 is the optical path length of light that passes through the third and fourth light attenuation filters without being reflected by them and is reflected twice by the layer between them. 3042 is the optical path length of light that passes through the third light attenuating filter without being reflected by the third light attenuating filter and is reflected twice by the fourth light attenuating filter.

[0018] Preferably, the plurality of light attenuation filters include a third light attenuation filter as the first light attenuation filter and a fourth light attenuation filter as the second light attenuation filter. The third light attenuation filter and the fourth light attenuation filter are any two light attenuation filters adjacent to each other among the plurality of light attenuation filters. The photometric device satisfies the following conditional expressions (14) and (15). OPD g1 ×(1 / λ-1 / (λ+Δλ b ))>0.5 …(14) OPD g2 ×(1 / λ-1 / (λ+Δλ b ))>0.5 …(15) However, OPD g1 =|OP 3240 -OP 30G240 | OPD g2 =|OP 3042 -OP 30G240 |OP 3240 is the optical path length of light that is reflected twice by the third optical attenuation filter and passes through the fourth optical attenuation filter without being reflected by the fourth optical attenuation filter. 30G240 is the optical path length of light that passes through the third and fourth light attenuation filters without being reflected by them and is reflected twice by the layer between them. 3042 is the optical path length of light that passes through the third light attenuating filter without being reflected by the third light attenuating filter and is reflected twice by the fourth light attenuating filter. [Effects of the Invention]

[0019] According to the present disclosure, it is possible to provide a photometric device that has a more compact size and is capable of measuring light with higher accuracy. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a schematic perspective view of a photometric device according to an embodiment; [Figure 2] 1 is a schematic block diagram of a variable optical attenuator according to an embodiment; [Figure 3] 1 is a schematic diagram of a variable optical attenuator according to an embodiment; [Figure 4] FIG. 2 is a schematic partial enlarged view of a photodetector according to an embodiment. [Figure 5] FIG. 4 is a schematic diagram showing a first interference in the variable optical attenuator according to the embodiment. [Figure 6]FIG. 4 is a schematic diagram showing a first interference in the variable optical attenuator according to the embodiment. [Figure 7] FIG. 10 is a schematic diagram showing a second interference in the variable optical attenuator according to the embodiment. [Figure 8] FIG. 10 is a schematic diagram showing a second interference in the variable optical attenuator according to the embodiment. [Figure 9] FIG. 10 is a schematic diagram showing a second interference in the variable optical attenuator according to the embodiment. [Figure 10] FIG. 10 is a schematic diagram showing a second interference in the variable optical attenuator according to the embodiment. [Figure 11] FIG. 10 is a schematic diagram showing a third interference in the variable optical attenuator according to the embodiment. [Figure 12] FIG. 10 is a schematic diagram showing a third interference in the variable optical attenuator according to the embodiment. [Figure 13] FIG. 10 is a schematic diagram showing a third interference in the variable optical attenuator according to the embodiment. [Figure 14] FIG. 10 is a schematic diagram showing a third interference in the variable optical attenuator according to the embodiment. [Figure 15] 4 is a graph showing the distribution of the incident angle of light incident on the variable optical attenuator in the first embodiment. FIG. [Figure 16] 10 is a graph showing the relative intensity of interference light caused by first interference when the incident angle of light under measurement to the variable optical attenuator is 5°. FIG. [Figure 17] 10 is a graph showing the relative intensity of interference light caused by first interference when the incident angle range of light to be measured on the variable optical attenuator is 3° or more and 7° or less (5°±2°). FIG. [Figure 18] FIG. 10 is a graph showing the relative intensity of interference light caused by second interference when the incident angle of light under measurement to the variable optical attenuator is 5°. [Figure 19] FIG. 10 is a graph showing the relative intensity of interference light caused by the second interference when the incident angle range of the light to be measured on the variable optical attenuator is 3° or more and 7° or less (5°±2°). [Figure 20]FIG. 10 is a graph showing the relative intensity of interference light caused by third interference when the incident angle of light under measurement to the variable optical attenuator is 5°. [Figure 21] FIG. 10 is a graph showing the relative intensity of interference light caused by third interference when the incident angle range of light to be measured on the variable optical attenuator is 3° or more and 7° or less (5°±2°). [Figure 22] FIG. 2 is a graph showing the spectral responsivity spectrum of one of a plurality of photodetection elements included in the photodetector. [Figure 23] FIG. 1 is a graph showing the spectrum of light emitted from an object to be measured. DETAILED DESCRIPTION OF THE INVENTION

[0021] A photometric device 1 according to an embodiment will be described with reference to Figures 1 to 4. The photometric device 1 is a device that measures light (measured light) emitted from an object under test 2. The object under test 2 is not particularly limited, but may be, for example, a flat panel display such as a liquid crystal display or an organic EL display.

[0022] 1, photometric device 1 mainly includes a variable optical attenuator 4 and a photodetector 8. Photometric device 1 may further include a spectroscopic element 6, and may be a device (e.g., an optical spectrum measuring device) capable of measuring spectral information (e.g., the spectrum of light to be measured) of object 2 under measurement. Photometric device 1 may further include a collimator lens 3 and a condenser lens 7.

[0023] The collimator lens 3 is disposed on the incident side of the variable optical attenuator 4 (plurality of optical attenuation filters 10, 20). The collimator lens 3 collimates the light emitted from the object 2 to be measured.

[0024] 1 and 2, the variable optical attenuator 4 is disposed on the output side of the collimator lens 3. Light collimated by the collimator lens 3 is incident on the variable optical attenuator 4. The variable optical attenuator 4 includes a plurality of optical attenuation filters 10, 20 and a driving device 5.

[0025] The multiple light attenuation filters 10, 20 may each be arranged at the same angle with respect to the optical axis 2p of the light incident on the variable optical attenuator 4. The multiple light attenuation filters 10, 20 may each be inclined at the same angle with respect to the optical axis 2p of the light incident on the variable optical attenuator 4. The multiple light attenuation filters 10, 20 may also be arranged parallel to each other. This allows the variable optical attenuator 4 to be made smaller, and the photometric device 1 to be made smaller as well.

[0026] Referring to FIG. 3, the plurality of light attenuation filters 10, 20 each include an interference multilayer film 12, 13, 22, 23 and a transparent substrate 11, 21 supporting the interference multilayer film 12, 13, 22, 23. A combination of any two of the plurality of light attenuation filters 10, 20 is referred to as a first light attenuation filter (e.g., light attenuation filter 10) and a second light attenuation filter (e.g., light attenuation filter 20). In the direction along the optical axis 2p, the second light attenuation filter is closer to the photodetector 8 than the first light attenuation filter. The first light attenuation filter includes a first interference multilayer film (e.g., at least one of the interference multilayer films 12, 13) as an interference multilayer film and a first transparent substrate (e.g., transparent substrate 11) as a transparent substrate. The second light attenuation filter includes a second interference multilayer film (e.g., at least one of the interference multilayer films 22, 23) as an interference multilayer film and a second transparent substrate (e.g., transparent substrate 21) as a transparent substrate.

[0027] The first optical path length of the first transparent substrate (e.g., transparent substrate 11) is different from the second optical path length of the second transparent substrate (e.g., transparent substrate 21). The first optical path length of the first transparent substrate is given by the product of the first refractive index of the first transparent substrate (e.g., refractive index n1) and the first thickness of the first transparent substrate (e.g., thickness d1). The second optical path length of the second transparent substrate is given by the product of the second refractive index of the second transparent substrate (e.g., refractive index n2) and the second thickness of the second transparent substrate (e.g., thickness d2). Since the thicknesses of the interference multilayer films 12, 13, 22, and 23 are negligible compared to the thicknesses of the transparent substrates 11 and 21, the fact that the first optical path length of the first transparent substrate (e.g., transparent substrate 11) is different from the second optical path length of the second transparent substrate (e.g., transparent substrate 21) means that the optical path length of the first light attenuation filter (e.g., light attenuation filter 10) is different from the optical path length of the second light attenuation filter (e.g., light attenuation filter 20).

[0028] The transparent substrates 11 and 21 are made of an optical material that is transparent to the light to be measured, such as glass, plastic, quartz, or sapphire. The transparent optical material that forms the transparent substrates 11 and 21 can be appropriately selected depending on the wavelength range of the light to be measured.

[0029] The interference multilayer films 12, 13, 22, and 23 are each formed on at least one of the incident surfaces 14 and 24 or the exit surfaces 15 and 25 of the corresponding transparent substrates 11 and 21. Specifically, the light attenuation filter 10 includes at least one of the interference multilayer films 12 and 13. The interference multilayer film 12 is formed on the incident surface 14 of the transparent substrate 11. The interference multilayer film 13 is formed on the exit surface 15 of the transparent substrate 11. The light attenuation filter 20 includes at least one of the interference multilayer films 22 and 23. The interference multilayer film 22 is formed on the incident surface 24 of the transparent substrate 21. The interference multilayer film 23 is formed on the exit surface 25 of the transparent substrate 21.

[0030] Specifically, the interference multilayer films 12, 13, 22, 23 are formed on both the incident surfaces 14, 24 and the exit surfaces 15, 25 of the corresponding transparent substrates 11, 21. Specifically, the light attenuation filter 10 includes an interference multilayer film 12 formed on the incident surface 14 of the transparent substrate 11, and an interference multilayer film 13 formed on the exit surface 15 of the transparent substrate 11. The light attenuation filter 20 includes an interference multilayer film 22 formed on the incident surface 24 of the transparent substrate 21, and an interference multilayer film 23 formed on the exit surface 25 of the transparent substrate 21.

[0031] The interference multilayers 12, 13, 22, and 23 may have the same or different multilayer structure. The interference multilayers 12, 13, 22, and 23 may be formed of the same or different materials. Examples of materials that can be used for each layer of the interference multilayers 12, 13, 22, and 23 include dielectric materials such as SiO2 and MgF2, metal oxide materials such as Al2O3, TiO2, Nb2O5, and NbO, and metal materials such as Cr and Nb.

[0032] Known light attenuation filters include absorption-type light attenuation filters that absorb light inside a substrate (e.g., a glass substrate). The degree of freedom in designing the transmission spectrum of absorption-type light attenuation filters is relatively low. Furthermore, the stability of absorption-type light attenuation filters with respect to environmental temperature and humidity is relatively low. In contrast, the degree of freedom in designing the transmission spectrum of interference-type light attenuation filters (e.g., light attenuation filters 10, 20 including interference multilayer films 12, 13, 22, 23) is relatively high. Furthermore, the stability of interference-type light attenuation filters with respect to environmental temperature and humidity is relatively high.

[0033] 2, the driving device 5 can insert the plurality of optical attenuation filters 10, 20 into and retract them from the optical axis 2p of light incident on the variable optical attenuator 4, independently of one another. This prevents the photodetector 8 from becoming saturated, and the intensity of the light to be measured incident on the photodetector 8 can be kept within the dynamic range of the photodetector 8. Furthermore, the photometric device 1 has a more compact size. The driving device 5 is, for example, a linear actuator.

[0034] 1, the spectroscopic element 6 disperses the light that has passed through the variable optical attenuator 4. The spectroscopic element 6 is, for example, a diffraction grating. The condenser lens 7 condenses the light dispersed by the spectroscopic element 6 onto the photodetector 8.

[0035] 1 and 4, the photodetector 8 receives light that has passed through the variable optical attenuator 4. Specifically, the photodetector 8 receives light that has been dispersed by the dispersing element 6. The photodetector 8 is a line sensor including a plurality of photodetecting elements 9. The plurality of photodetecting elements 9 each detects light of a plurality of different wavelengths contained in the light to be measured. Each of the plurality of photodetecting elements 9 is, for example, a charge-coupled device (CCD) sensor or a complementary metal-oxide semiconductor (CMOS) sensor.

[0036] The optical reflectance of the optical attenuation filters 10 and 20, which include the interference multilayer films 12, 13, 22, and 23, tends to be greater than the optical reflectance of an absorptive optical attenuation filter. Therefore, reflected light generated in the optical attenuation filters 10 and 20, which include the interference multilayer films 12, 13, 22, and 23, may adversely affect the measurement results of the photometric device 1. As described below, this adverse effect is reduced in this embodiment.

[0037] When multiple light attenuation filters are inserted multiple times onto the optical axis 2p, it is difficult to always keep the relative tilt angle between any two of the multiple light attenuation filters (e.g., light attenuation filters 10, 20) completely equal. When multiple light attenuation filters are inserted multiple times onto the optical axis 2p, the relative tilt angle between any two of the multiple light attenuation filters (e.g., light attenuation filters 10, 20) may vary slightly. Furthermore, the relative tilt angle between any two of the multiple light attenuation filters (e.g., light attenuation filters 10, 20) may vary slightly due to changes in the temperature of the environment in which the multiple light attenuation filters are arranged.

[0038] If the optical path lengths of the multiple light attenuation filters are equal to each other, a slight change in the relative tilt angle between any two of the multiple light attenuation filters (e.g., light attenuation filters 10 and 20) will cause the measurement results of the photometric device to fluctuate significantly. This makes it difficult to stably measure light using the photometric device. Because the thicknesses of the interference multilayer films 12, 13, 22, and 23 are negligible compared to the thicknesses of the transparent substrates 11 and 21, the fact that the optical path lengths of the multiple light attenuation filters 10 and 20 are equal to each other essentially means that the optical path lengths of the multiple transparent substrates 11 and 21 are equal to each other.

[0039] The inventors have discovered that the cause of the large fluctuations in the measurement results of the photometric device 1 is the fluctuation component of the interference intensity resulting from interference between multiple reflected light beams generated by the multiple light attenuation filters 10, 20. For example, even if the optical path length difference between the two multiple reflected light beams generated by the two light attenuation filters 10, 20 fluctuates by less than the wavelength of the light measured by the photometric device 1 (for example, between several tens of nanometers and several hundreds of nanometers when the measurement light is visible light), the fluctuation component of the interference intensity between the two multiple reflected light beams becomes large, and even a slight change in the relative tilt angle between the two light attenuation filters 10, 20 causes large fluctuations in the measurement results of the photometric device 1. Such interference between multiple reflected light beams mainly includes the following three types of interference (first interference, second interference, and third interference).

[0040] The first type of interference is interference between the second reflected light generated by the first light attenuation filter (light attenuation filter 10) and the second reflected light generated by the second light attenuation filter (light attenuation filter 20) (see FIGS. 5 and 6). The second type of interference is interference between the second reflected light generated by one of the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) and the fourth reflected light generated by the other of the first light attenuation filter and the second light attenuation filter (see FIGS. 7 to 10). The third type of interference is interference between the second reflected light generated by one of the third light attenuation filter (light attenuation filter 10) and the fourth light attenuation filter (light attenuation filter 20) and the second reflected light generated by a layer (e.g., an air layer) between the third and fourth light attenuation filters (see FIGS. 11 to 14). Note that the third light attenuation filter corresponds to the first light attenuation filter, and the fourth light attenuation filter corresponds to the second light attenuation filter. The third light attenuation filter and the fourth light attenuation filter are any two light attenuation filters adjacent to each other among the plurality of light attenuation filters.

[0041] Of the three types of interference, the first type of interference often has the greatest effect on fluctuations in the measurement results of the photometric device 1. The reason for this is as follows: The number of reflections of the multiple-reflected light in the second type of interference is greater than the number of reflections of the multiple-reflected light in the first type of interference. Therefore, the fluctuation component of the interference intensity caused by the second type of interference is often smaller than the fluctuation component of the interference intensity caused by the first type of interference. In addition, the reflectance of a light attenuation filter using an interference multilayer film for light incident on the interference multilayer film from the air layer side is generally lower than the reflectance of the light attenuation filter using an interference multilayer film for light incident on the interference multilayer film from the inner side (transparent substrate side) of the light attenuation filter. Thus, the fluctuation component of the interference intensity caused by the third type of interference is often smaller than the fluctuation component of the interference intensity caused by the first interference.

[0042] Therefore, by reducing the fluctuation component of the interference intensity caused by the first interference, it is possible to effectively reduce the fluctuation in the measurement results of the photometric device 1, and light can be measured stably and with high accuracy using the photometric device 1. In addition to the first interference, it is preferable to further reduce at least one of the fluctuation component of the interference intensity caused by the second interference or the fluctuation component of the interference intensity caused by the third interference. Therefore, it is possible to further effectively reduce the fluctuation in the measurement results of the photometric device 1, and light can be measured with even improved accuracy using the photometric device 1.

[0043] The interference between the multiple reflected light beams generated in the multiple light attenuation filters 10, 20 includes not only first interference, second interference, and third interference, but also higher-order interference. However, the number of reflections of the multiple reflected light beam in the higher-order interference is greater than the number of reflections of the multiple reflected light beam in the first interference, the number of reflections of the multiple reflected light beam in the second interference, and the number of reflections of the multiple reflected light beam in the third interference. Therefore, the fluctuation component of the interference intensity caused by the higher-order interference is smaller than the fluctuation component of the interference intensity caused by the first interference, the second interference, and the third interference, and can be ignored.

[0044] In this embodiment, the first optical path length of the first transparent substrate (e.g., transparent substrate 11) of the first light attenuation filter (e.g., light attenuation filter 10) is different from the second optical path length of the second transparent substrate (e.g., transparent substrate 21) of the second light attenuation filter (e.g., light attenuation filter 20). Therefore, the period of the interference waveform caused by the interference between the multiple reflected lights generated in the multiple light attenuation filters 10 and 20 is shortened. The interference waveform is averaged, and the fluctuation component of the interference intensity between the multiple reflected lights generated in the multiple light attenuation filters 10 and 20 is reduced. Even if the relative tilt angle between the first light attenuation filter and the second light attenuation filter varies, the measurement result of the photometric device 1 hardly varies. The photometric device 1 can measure the light emitted from the object 2 with higher accuracy.

[0045] Below, we will explain the reduction of the fluctuation components of interference intensity caused by the first interference, the second interference, and the third interference in Examples 1 to 3, the reduction of the fluctuation components of interference intensity caused by the first interference in Examples 4 to 6, the reduction of the fluctuation components of interference intensity caused by the first interference and the second interference in Examples 7 to 9, and the reduction of the fluctuation components of interference intensity caused by the first interference and the third interference in Examples 10 to 12.

[0046] <Examples 1, 2, and 3> Examples 1 to 3 will be described with reference to FIGS. 1 to 23. In Examples 1 to 3, the multiple light attenuation filters 10, 20 are configured with two light attenuation filters 10, 20. The first light attenuation filter is the light attenuation filter 10, and the second light attenuation filter is the light attenuation filter 20. Since the light attenuation filter 10 and the light attenuation filter 20 are adjacent to each other, the light attenuation filter 10 also serves as the third light attenuation filter, and the light attenuation filter 20 also serves as the fourth light attenuation filter. The light attenuation filter 10 includes interference multilayer films 12, 13 and a transparent substrate 11 that supports the interference multilayer films 12, 13. The light attenuation filter 20 includes interference multilayer films 22, 23 and a transparent substrate 21 that supports the interference multilayer films 22, 23.

[0047] The configuration of the variable optical attenuator 4 in Examples 1 to 3 is as shown in Table 1. Therefore, the optical path length of the transparent substrate 11 is different from the optical path length of the transparent substrate 21. The reflectance of the incident surface 14 of the transparent substrate 11 and the reflectance of the exit surface 15 of the transparent substrate 11 are each 10%. The reflectance of the incident surface 14 of the transparent substrate 11 is the reflectance of the interference multilayer film 12. The reflectance of the exit surface 15 of the transparent substrate 11 is the reflectance of the interference multilayer film 13. The reflectance of the incident surface 24 of the transparent substrate 21 and the reflectance of the exit surface 25 of the transparent substrate 21 are each 10%. The reflectance of the incident surface 24 of the transparent substrate 11 is the reflectance of the interference multilayer film 22. The reflectance of the exit surface 25 of the transparent substrate 21 is the reflectance of the interference multilayer film 23. 5, 7, 8, 11, and 12, the relative tilt angle θ between the light attenuation filter 10 and the light attenuation filter 20 (for example, the tilt angle of the light attenuation filter 10 relative to the light attenuation filter 20) is 0.0°. In FIGS. 6, 9, 10, 13, and 14, the relative tilt angle θ between the light attenuation filter 10 and the light attenuation filter 20 is 0.1°.

[0048] [Table 1]

[0049] (a) Distribution of the incident angle of the light to be measured incident on the variable optical attenuator 4, (b) Half-width Δλ of the spectral responsivity spectrum of the photodetector element 9 a , or (c) the line width Δλ of the light (measured light) emitted from the object 2 to be measured b At least one of the above reduces the fluctuation component of the interference intensity caused by the interference between the multiple reflected lights, thereby reducing the fluctuation of the measurement result of the photometric device 1 when the relative tilt angle θ between the light attenuation filter 10 and the light attenuation filter 20 changes slightly. In this specification, the incident angle of the light to be measured incident on the variable optical attenuator 4 is defined as the incident angle of the light to be measured (when the light to be measured has a distribution of incident angles, the component of the light to be measured having the central incident angle of the distribution of incident angles of the light to be measured) with respect to the optical axis of the variable optical attenuator 4. Linewidth Δλ of the light to be measured b is defined as the half-width of the spectrum of the light under measurement.

[0050] In the first embodiment, the above (a) reduction of the fluctuation components of the interference intensity caused by the first interference, the second interference, and the third interference due to the distribution of the incident angle of the light to be measured incident on the variable optical attenuator 4 is achieved, and in the second embodiment, the above (b) reduction of the half-width Δλ of the spectral responsivity spectrum of the photodetector element 9 is achieved. a In the third embodiment, the reduction of the fluctuation components of the interference intensity due to the first interference, the second interference, and the third interference is achieved by the above (c) the line width Δλ of the light (measured light) emitted from the object 2 to be measured. b The reduction of the fluctuation components of the interference intensity caused by the first interference, the second interference, and the third interference by the above-mentioned method will be examined. Note that the longer the wavelength λ of the light, the smaller the value of the left side of each of conditional expressions (1) to (15). The smaller the value of the left side of each of conditional expressions (1) to (15), the larger the fluctuation components of the interference intensity caused by interference between multiple reflected light beams. Therefore, in Examples 1 to 3, the wavelength λ of the light is set to the wavelength at which the fluctuation components of the interference intensity caused by interference between multiple reflected light beams are largest, i.e., the maximum wavelength in the measurable wavelength range of the photometric device 1.

[0051] Example 1 In this embodiment, the measurable wavelength range of the photometric device 1 is 380 nm or more and 780 nm or less. The distribution of the incident angle of light incident on the variable optical attenuator 4 is in the incident angle range of 3° or more and 7° or less (5°±2° incident angle range) (see Table 2), and the light intensity is uniform within this incident angle range (see FIG. 15). The photometric device 1 is a spectrometer (polychromator), and the photodetector 8 includes multiple photodetector elements 9. Of the multiple photodetector elements 9, the photodetector element 9 corresponding to the maximum wavelength in the measurable wavelength range of the photometric device 1 has a Gaussian shape with a peak wavelength of 780 nm. The half-width Δλ of the spectral responsivity spectrum of this photodetector element 9 is a is 10 nm (see Table 2). The spectrum of the light (measured light) emitted from the object 2 under test has a Gaussian shape with a peak wavelength of 780 nm. The linewidth Δλ of the light (measured light) emitted from the object 2 under test b is 0.01 nm (see Table 2).

[0052] [Table 2]

[0053] Line width Δλ of the light (measured light) emitted from the object 2 b is sufficiently small, the half width Δλ of the spectral responsivity spectrum of the photodetector element 9 a and the line width Δλ of the light (measured light) emitted from the object 2 under test (c). b The reduction in the fluctuation components of the interference intensity caused by the interference between the multiple reflected light beams due to the above (a) distribution of the incident angles of the light under measurement incident on the variable optical attenuator 4 is considered in Example 1.

[0054] <Reduction of the fluctuation component of the interference intensity caused by the first interference due to the distribution of the incident angle of the light under measurement incident on the variable optical attenuator 4> In this embodiment, the following conditional expression (1) is satisfied. |OPD θmax1 -OPD θmin1 | / λ>0.5 …(1) OPD θmax1 =(OP 1220max -OP 1022max ) OPD θmin1 =(OP 1220min -OP 1022min ) where λ is the wavelength of light included in the measurable wavelength range of the photometric device 1.

[0055] OP 1220max is the optical path length of the maximum incident angle light that is reflected twice by the first optical attenuation filter (optical attenuation filter 10) and passes through the second optical attenuation filter (optical attenuation filter 20) without being reflected by the second optical attenuation filter. The maximum incident angle light is the light that has the largest incident angle to the variable optical attenuator 4 out of the light that enters the variable optical attenuator 4. OP 1022max is the optical path length of the maximum incident angle light that passes through the first light attenuating filter without being reflected by the first light attenuating filter and is reflected twice by the second light attenuating filter. 1220minis the optical path length of the minimum incident angle light that is reflected twice by the first optical attenuation filter and passes through the second optical attenuation filter without being reflected by the second optical attenuation filter. The minimum incident angle light is the light that has the smallest incident angle to the variable optical attenuator 4 among the lights that are incident on the variable optical attenuator 4. OP 1022min is the optical path length of the minimum incident angle light that passes through the first light attenuating filter without being reflected by the first light attenuating filter and is reflected twice by the second light attenuating filter.

[0056] In this embodiment, when the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 5), |OPD θmax1 -OPD θmin1 | / λ is 3.571. When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 6), |OPD θmax1 -OPD θmin1 | / λ is 3.368. Therefore, this embodiment satisfies conditional expression (1).

[0057] When conditional expression (1) is satisfied, it is possible to reduce the fluctuation component of the interference intensity caused by the first interference (interference between light reflected twice by the first optical attenuation filter (optical attenuation filter 10) and light reflected twice by the second optical attenuation filter (optical attenuation filter 20)). Referring to FIGS. 16 and 17, when the incident angle range of the light to be measured incident on the variable optical attenuator 4 is 3° or more and 7° or less (5°±2°), the fluctuation of the relative interference intensity caused by the first interference is smaller than the fluctuation of the relative interference intensity caused by the first interference when the incident angle of the light to be measured incident on the variable optical attenuator 4 is 5°. In this specification, the relative interference intensity is an interference intensity normalized by a reference intensity of light that transmits through the optical attenuation filters 10 and 20 without being reflected by them, and is obtained by converting this reference intensity to a relative intensity of zero. The reason why the fluctuation component of the interference intensity caused by the first interference is reduced by the distribution of the incident angle of the light to be measured incident on the variable optical attenuator 4 is as follows.

[0058] When the incident angle of the light under measurement incident on the variable optical attenuator 4 changes, the interference waveform in Fig. 16 shifts laterally. The interference waveform in Fig. 17 is an average waveform obtained by adding together multiple interference waveforms in Fig. 16 that are shifted laterally by different amounts depending on the incident angle of the light under measurement incident on the variable optical attenuator 4. Therefore, when the incident angle range of the light under measurement incident on the variable optical attenuator 4 is 3° or more and 7° or less (5°±2°), the fluctuation in interference intensity caused by the first interference is smaller than the fluctuation in interference intensity caused by the first interference when the incident angle of the light under measurement incident on the variable optical attenuator 4 is 5°.

[0059] The left side of conditional expression (1) represents how many times the period of the interference waveform in FIG. 16 shifts between when the angle of incidence of the light to be measured incident on the variable optical attenuator 4 is maximum and when the angle of incidence of the light to be measured incident on the variable optical attenuator 4 is minimum. If conditional expression (1) is satisfied, a high averaging effect can be obtained, and fluctuations in the interference intensity caused by the first interference (interference between light reflected twice by the first optical attenuation filter (optical attenuation filter 10) and light reflected twice by the second optical attenuation filter (optical attenuation filter 20)) can be reduced. Specifically, the fluctuation in the measurement value of the photometric device 1 caused by the first interference when the relative tilt angle θ between the first optical attenuation filter and the second optical attenuation filter changes from 0.0° to 0.1° is 0.26%. In this specification, the measurement value fluctuation of the photometric device 1 is defined as the difference between the relative interference intensity of light with a wavelength of 780 nm at a relative tilt angle θ of 0.0° and the relative interference intensity of light with a wavelength of 780 nm at a relative tilt angle θ of 0.1°. Therefore, even if the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes slightly, the fluctuation in interference intensity caused by the first interference is reduced, and the light to be measured can be measured with high accuracy.

[0060] <Reduction of the fluctuation component of the interference intensity caused by the second interference due to the distribution of the incident angle of the light under measurement incident on the variable optical attenuator 4> In this embodiment, the following conditional expressions (4) and (5) are satisfied. |OPD θmax2 -OPD θmin2 | / λ>0.5 …(4) |OPD θmax3 -OPD θmin3 | / λ>0.5 …(5) OPD θmax2 =(OP 1420max -OP 1022max ) OPD θmin2 =(OP 1420min -OP 1022min ) OPD θmax3 =(OP 1024max -OP 1220max ) OPD θmin3 =(OP 1024min -OP 1220min )

[0061] OP 1420max is the optical path length of the maximum incident angle light that is reflected four times by the first light attenuation filter (light attenuation filter 10) and passes through the second light attenuation filter (light attenuation filter 20) without being reflected by the second light attenuation filter. 1022max is the optical path length of the maximum incident angle light that passes through the first light attenuating filter without being reflected by the first light attenuating filter and is reflected twice by the second light attenuating filter. 1420min is the optical path length of the minimum incident angle light that is reflected four times by the first light attenuation filter and passes through the second light attenuation filter without being reflected by the second light attenuation filter. 1022min is the optical path length of the minimum incident angle light that passes through the first light attenuating filter without being reflected by the first light attenuating filter and is reflected twice by the second light attenuating filter.

[0062] OP 1024max is the optical path length of the maximum incident angle light that passes through the first light attenuation filter (light attenuation filter 10) without being reflected by it and is reflected four times by the second light attenuation filter (light attenuation filter 20). 1220max is the optical path length of the maximum incident angle light that is reflected twice by the first light attenuation filter and passes through the second light attenuation filter without being reflected by the second light attenuation filter. 1024min is the optical path length of the minimum incident angle light that passes through the first light attenuating filter without being reflected by the first light attenuating filter and is reflected four times by the second light attenuating filter. 1220minis the optical path length of the minimum incident angle light that is reflected twice by the first light attenuation filter and passes through the second light attenuation filter without being reflected by the second light attenuation filter.

[0063] In this embodiment, when the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 7), |OPD θmax2 -OPD θmin2 | / λ is 3.061. When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 9), |OPD θmax2 -OPD θmin2 | / λ is 2.797. Therefore, this embodiment satisfies conditional expression (4). When the relative tilt angle θ between the first light attenuating filter and the second light attenuating filter is 0.0° (see FIG. 8), |OPD θmax3 -OPD θmin3 | / λ is 13.772. When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 10), |OPD θmax3 -OPD θmin3 | / λ is 13.367. Therefore, this embodiment satisfies conditional expression (5).

[0064] When conditional expression (4) is satisfied, it is possible to reduce the fluctuation component of the interference intensity caused by the second interference (interference between the light reflected four times by the first light attenuation filter (light attenuation filter 10) and the light reflected twice by the second light attenuation filter (light attenuation filter 20)). As can be seen from FIGS. 18 and 19, when the incident angle range of the light under measurement incident on the variable optical attenuator 4 is 3° or more and 7° or less (5°±2°), the fluctuation of the relative interference intensity caused by the second interference is smaller than the fluctuation of the relative interference intensity caused by the second interference when the incident angle of the light under measurement incident on the variable optical attenuator 4 is 5°. The reason why the fluctuation component of the interference intensity caused by the second interference is reduced by the distribution of the incident angle of the light under measurement incident on the variable optical attenuator 4 is the averaging effect of the interference waveform, similar to the reason why the fluctuation of the interference intensity caused by the first interference is reduced.

[0065] Specifically, the fluctuation in the measurement value of the photometric device 1 due to the second interference (interference between light reflected four times by the first light attenuation filter and light reflected twice by the second light attenuation filter) when the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) changes from 0.0° to 0.1° is −0.01%. Therefore, even if the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter changes slightly, the fluctuation in interference intensity due to the second interference is reduced, and the light to be measured can be measured with high accuracy.

[0066] When conditional expression (5) is satisfied, similarly to when conditional expression (4) is satisfied, it is possible to reduce the fluctuation component of the interference intensity caused by the second interference (interference between the light reflected twice by the first light-attenuating filter (light-attenuating filter 10) and the light reflected four times by the second light-attenuating filter (light-attenuating filter 20)). Specifically, when the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes from 0.0° to 0.1°, the fluctuation in the measurement value of the photometric device 1 caused by the second interference is 0.00%. Therefore, even if the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes slightly, the fluctuation in the interference intensity caused by the second interference is reduced, and the light to be measured can be measured with high accuracy.

[0067] <Reduction of the fluctuation component of the interference intensity caused by the third interference due to the distribution of the incident angle of the light under measurement incident on the variable optical attenuator 4> In this embodiment, the following conditional expressions (10) and (11) are satisfied. |OPD θmax4 -OPD θmin4 | / λ>0.5 …(10) |OPD θmax5 -OPD θmin5 | / λ>0.5 …(11) OPD θmax4 =(OP 3240max -OP 30G240max ) OPD θmin4 =(OP 3240min -OP 30G240min ) OPD θmax5 =(OP 3042max -OP 30G240max ) OPD θmin5 =(OP 3042min -OP 30G240min )

[0068] OP 3240max is the optical path length of the maximum incident angle light that is reflected twice by the third light attenuation filter (light attenuation filter 10) and passes through the fourth light attenuation filter (light attenuation filter 20) without being reflected by the fourth light attenuation filter. 30G240max is the optical path length of the maximum incident angle light that passes through the third and fourth light attenuation filters without being reflected by them and is reflected twice by a layer (for example, an air layer) between the third and fourth light attenuation filters. 3240min is the optical path length of the minimum incident angle light that is reflected twice by the third light attenuation filter and passes through the fourth light attenuation filter without being reflected by the fourth light attenuation filter.

[0069] OP 30G240min is the optical path length of the minimum incident angle light that passes through the third light attenuation filter (light attenuation filter 10) and the fourth light attenuation filter (light attenuation filter 20) without being reflected by them, and is reflected twice by a layer (for example, an air layer) between the third light attenuation filter and the fourth light attenuation filter.3042max is the optical path length of the maximum incident angle light that passes through the third light attenuation filter without being reflected by the third light attenuation filter and is reflected twice by the fourth light attenuation filter. 3042min is the optical path length of the minimum incident angle light that passes through the third light attenuation filter without being reflected by the third light attenuation filter and is reflected twice by the fourth light attenuation filter.

[0070] In this embodiment, when the relative tilt angle θ between the third light attenuation filter (light attenuation filter 10) and the fourth light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 13), |OPD θmax4 -OPD θmin4 | / λ is 40.164. When the relative tilt angle θ between the third light attenuation filter and the fourth light attenuation filter is 0.1° (see FIG. 16), |OPD θmax4 -OPD θmin4 | / λ is 40.774. Therefore, this embodiment satisfies conditional expression (10). When the relative tilt angle θ between the third light attenuation filter and the fourth light attenuation filter is 0.0° (see FIG. 12), |OPD θmax5 -OPD θmin5 | is 36.594. When the relative tilt angle θ between the third light attenuation filter and the fourth light attenuation filter is 0.1° (see FIG. 10), |OPD θmax5 -OPD θmin5 is 37.274. Therefore, this embodiment satisfies conditional expression (11).

[0071] When conditional expression (10) is satisfied, it is possible to reduce the fluctuation component of the interference intensity caused by the third interference (interference between light reflected twice by the third light attenuation filter (light attenuation filter 10) and light reflected twice by a layer (e.g., an air layer) between the third light attenuation filter and the fourth light attenuation filter (light attenuation filter 20)). As can be seen from FIGS. 20 and 21, when the incident angle range of the light to be measured incident on the variable optical attenuator 4 is 3° or more and 7° or less (5°±2°), the fluctuation of the relative interference intensity caused by the third interference is smaller than the fluctuation of the relative interference intensity caused by the third interference when the incident angle of the light to be measured incident on the variable optical attenuator 4 is 5°. The reason why the fluctuation component of the interference intensity caused by the third interference is reduced by the distribution of the incident angle of the light to be measured incident on the variable optical attenuator 4 is the averaging effect of the interference waveform, similar to the reason why the fluctuation of the interference intensity caused by the first interference is reduced.

[0072] Specifically, when the relative tilt angle θ between the third light attenuation filter (light attenuation filter 10) and the fourth light attenuation filter (light attenuation filter 20) changes from 0.0° to 0.1°, the fluctuation in the measurement value of the photometric device 1 due to the third interference (interference between light reflected twice by the third light attenuation filter and light reflected twice by a layer (e.g., an air layer) between the third light attenuation filter and the fourth light attenuation filter) is 0.01%. Therefore, even if the relative tilt angle θ between the third light attenuation filter and the fourth light attenuation filter changes slightly, the fluctuation in interference intensity due to the third interference is reduced, and the light to be measured can be measured with high accuracy.

[0073] When conditional expression (11) is satisfied, similarly to when conditional expression (10) is satisfied, it is possible to reduce the fluctuation component of the interference intensity caused by the third interference (interference between light reflected twice by the fourth light-attenuating filter (light-attenuating filter 20) and light reflected twice by a layer (e.g., an air layer) between the third light-attenuating filter (light-attenuating filter 10) and the fourth light-attenuating filter). Specifically, when the relative tilt angle θ between the third light-attenuating filter and the fourth light-attenuating filter changes from 0.0° to 0.1°, the fluctuation in the measurement value of the photometric device 1 caused by the third interference is 0.00%. Therefore, even if the relative tilt angle θ between the third light-attenuating filter and the fourth light-attenuating filter changes slightly, the fluctuation in the interference intensity caused by the third interference is reduced, and the light to be measured can be measured with high accuracy.

[0074] The measurement value fluctuation of the photometric device 1 of this embodiment is given by the sum of the measurement value fluctuation caused by the first interference, the measurement value fluctuation caused by the second interference, and the measurement value fluctuation caused by the third interference. The measurement value fluctuation of the photometric device 1 of this embodiment is 0.26%. If the absolute value of the measurement value fluctuation of the photometric device 1 is within 5%, the light to be measured can be measured with high accuracy. It is more preferable if the absolute value of the measurement value fluctuation of the photometric device 1 is within 1%. Since the absolute value of the measurement value fluctuation of the photometric device 1 of this embodiment is within 1%, the light to be measured can be measured with high accuracy.

[0075] <Example 2> The photometric device 1 of this embodiment is similar to the photometric device 1 of the first embodiment, but differs mainly in the following points: There is no distribution of the angle of incidence of light incident on the variable optical attenuator 4, and the angle of incidence of light on the variable optical attenuator 4 is 5° (see Table 3). The half-width Δλ of the spectral responsivity spectrum of the photodetector 9 a is 3 nm (see Table 3 and FIG. 22). The line width Δλ of the light (measured light) emitted from the object 2 to be measured b is 300 nm (see Table 3).

[0076] [Table 3]

[0077] The half-width Δλ of the spectral responsivity spectrum of the photodetector element 9 a is the line width Δλ of the light (measured light) emitted from the object 2 under test. b Since the interference intensity fluctuation component caused by the interference between the multiple reflected lights is sufficiently smaller than the above (b) half width Δλ of the spectral responsivity spectrum of the photodetector element 9, the reduction of the interference intensity fluctuation component caused by the interference between the multiple reflected lights is a and (c) the line width Δλ of the light (measured light) emitted from the object 2 to be measured. b Among these, (b) the half-width Δλ of the spectral responsivity spectrum of the photodetector element 9 a In this embodiment, since there is no distribution of the incident angle of the light to be measured incident on the variable optical attenuator 4, there is no reduction in the fluctuation component of the interference intensity caused by the interference between a plurality of multiple reflected lights due to the distribution of the incident angle of the light to be measured incident on the variable optical attenuator 4. In this embodiment ... distribution of the incident angle of the light to be measured incident on the variable optical attenuator 4 due to the distribution of the incident angle of the light to be measured a The present invention considers the reduction of fluctuation components of interference intensity caused by first interference, second interference, and third interference among a plurality of multiple reflected lights.

[0078] <Frequency width Δλ of the spectral response spectrum of the photodetector element 9 a Reduction of the fluctuation component of the interference intensity caused by the first interference by In this embodiment, the following conditional expression (2) is satisfied. OPD 12 ×(1 / λ-1 / (λ+Δλ a ))>0.5 …(2) OPD 12 =|OP 1220 -OP 1022 λ is the wavelength of light included in the measurable wavelength range of the photometric device 1. Δλ a is the half-width of the spectral responsivity spectrum of the photodetector element 9.

[0079] OP 1220 is the optical path length of light that is reflected twice by the first light attenuation filter (light attenuation filter 10) and passes through the second light attenuation filter (light attenuation filter 20) without being reflected by the second light attenuation filter (see FIG. 5). 1022is the optical path length of light that passes through the first light attenuation filter (light attenuation filter 10) without being reflected by it and is reflected twice by the second light attenuation filter (light attenuation filter 20) (see FIG. 6).

[0080] In this embodiment, when the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 5), OPD 12 ×(1 / λ-1 / (λ+Δλ a When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 6), the OPD 12 ×(1 / λ-1 / (λ+Δλ a )) is 5.237. Therefore, this embodiment satisfies conditional expression (2).

[0081] When conditional expression (2) is satisfied, it is possible to reduce the fluctuation component of the interference intensity caused by the first interference (interference between light reflected twice by the first light attenuation filter (light attenuation filter 10) and light reflected twice by the second light attenuation filter (light attenuation filter 20)). The measured value measured by the photodetector 8 is given by the product of the spectrum of the relative interference intensity caused by the first interference (see FIG. 16) and the spectral responsivity spectrum of the photodetector 9 (see FIG. 22). The left side of conditional expression (2) is the half-width Δλ of the spectral responsivity spectrum of the photodetector 9 shown in FIG. 22. a 16. If conditional expression (2) is satisfied, a high averaging effect of the interference waveform can be obtained, and fluctuations in the interference intensity caused by the first interference can be reduced.

[0082] Specifically, the fluctuation in the measurement value of the photometric device 1 due to the first interference (interference between light reflected twice by the first light attenuation filter and light reflected twice by the second light attenuation filter) when the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) changes from 0.0° to 0.1° is 0.00%. Therefore, even if the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter changes slightly, the fluctuation in interference intensity due to the first interference is reduced, and the light to be measured can be measured with high accuracy.

[0083] <Frequency width Δλ of the spectral response spectrum of the photodetector element 9 a Reduction of the fluctuation component of the interference intensity caused by the second interference> In this embodiment, the following conditional expressions (6) and (7) are satisfied. OPD 21 ×(1 / λ-1 / (λ+Δλ a ))>0.5 …(6) OPD 22 ×(1 / λ-1 / (λ+Δλ a ))>0.5 …(7) OPD 21 =|OP 1420 -OP 1022 | OPD 22 =|OP 1024 -OP 1220 |

[0084] OP 1420 is the optical path length of light that is reflected four times by the first light attenuation filter (light attenuation filter 10) and passes through the second light attenuation filter (light attenuation filter 20) without being reflected by the second light attenuation filter (see FIGS. 7 and 9). 1022 is the optical path length of light that passes through the first light attenuating filter without being reflected by the first light attenuating filter and is reflected twice by the second light attenuating filter (see Figures 7 and 9). 1024 is the optical path length of light that passes through the first light attenuating filter without being reflected by the first light attenuating filter and is reflected four times by the second light attenuating filter (see Figures 8 and 10). 1220is the optical path length of light that is reflected twice by the first light-attenuating filter and passes through the second light-attenuating filter without being reflected by the second light-attenuating filter (see FIGS. 8 and 10).

[0085] In this embodiment, when the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 7), OPD 21 ×(1 / λ-1 / (λ+Δλ a When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 9), the OPD 21 ×(1 / λ-1 / (λ+Δλ a )) is 4.489. Therefore, this embodiment satisfies conditional expression (6). When the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter is 0.0° (see FIG. 8), OPD 21 ×(1 / λ-1 / (λ+Δλ a When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 10), the OPD 21 ×(1 / λ-1 / (λ+Δλ a )) is 20.196. Therefore, this embodiment satisfies conditional expression (7).

[0086] When conditional expression (6) is satisfied, it is possible to reduce the fluctuation component of the interference intensity caused by the second interference (interference between light reflected twice by the first light attenuation filter (light attenuation filter 10) and light reflected twice by the second light attenuation filter (light attenuation filter 20)). The measured value measured by the photodetector 8 is given by the product of the spectrum of the relative interference intensity caused by the second interference (see FIG. 18) and the spectral responsivity spectrum of the photodetector 9 (see FIG. 22). The left side of conditional expression (6) is the half-width Δλ of the spectral responsivity spectrum of the photodetector 9. a18 is included within the specified period. If conditional expression (6) is satisfied, a high averaging effect of the interference waveform can be obtained, and fluctuations in the interference intensity caused by the second interference can be reduced.

[0087] Specifically, the fluctuation in the measurement value of the photometric device 1 due to the second interference when the relative tilt angle θ between the first light-attenuating filter (light-attenuating filter 10) and the second light-attenuating filter (light-attenuating filter 20) changes from 0.0° to 0.1° is 0.00%. Therefore, even if the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes slightly, the fluctuation in the interference intensity due to the second interference (interference between the light reflected twice by the first light-attenuating filter and the light reflected twice by the second light-attenuating filter) is reduced, and the light to be measured can be measured with high accuracy.

[0088] When conditional expression (7) is satisfied, similarly to when conditional expression (6) is satisfied, it is possible to reduce the fluctuation component of the interference intensity caused by the second interference (interference between light reflected twice by the first light-attenuating filter (light-attenuating filter 10) and light reflected four times by the second light-attenuating filter (light-attenuating filter 20)). As a result, even if the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes slightly, the interference intensity caused by the second interference hardly changes. Specifically, when the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes from 0.0° to 0.1°, the fluctuation in the measurement value of the photometric device 1 caused by the second interference is 0.00%. Therefore, even if the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes slightly, the fluctuation in the interference intensity caused by the second interference is reduced, and the light to be measured can be measured with high accuracy.

[0089] <Frequency width Δλ of the spectral response spectrum of the photodetector element 9 a Reduction of the fluctuation component of the interference intensity caused by the third interference by In this embodiment, the following conditional expressions (12) and (13) are satisfied. OPD g1 ×(1 / λ-1 / (λ+Δλ a ))>0.5 …(12) OPDg2 ×(1 / λ-1 / (λ+Δλ a ))>0.5 …(13) OPD g1 =|OP 3240 -OP 30G240 | OPD g2 =|OP 3042 -OP 30G240 |

[0090] OP 3240 is the optical path length of light that is reflected twice by the third light attenuation filter (light attenuation filter 10) and passes through the fourth light attenuation filter (light attenuation filter 20) without being reflected by the fourth light attenuation filter. 30G240 is the optical path length of light that passes through the third and fourth light attenuation filters without being reflected by them and is reflected twice by a layer (for example, an air layer) between the third and fourth light attenuation filters. 3042 is the optical path length of light that passes through the third light attenuating filter without being reflected by the third light attenuating filter and is reflected twice by the fourth light attenuating filter.

[0091] In this embodiment, when the relative tilt angle θ between the third light attenuation filter (light attenuation filter 10) and the fourth light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 11), OPD g1 ×(1 / λ-1 / (λ+Δλ a When the relative tilt angle θ between the third and fourth light attenuation filters is 0.1° (see FIG. 13), the OPD g1 ×(1 / λ-1 / (λ+Δλ a )) is 19.634. Therefore, this embodiment satisfies conditional expression (12). When the relative tilt angle θ between the third light attenuation filter and the fourth light attenuation filter is 0.0° (see FIG. 12), OPD g2 ×(1 / λ-1 / (λ+Δλ aWhen the relative tilt angle θ between the third and fourth light attenuation filters is 0.1° (see FIG. 14), the OPD g2 ×(1 / λ-1 / (λ+Δλ a )) is 14.398. Therefore, this embodiment satisfies conditional expression (13).

[0092] When conditional expression (12) is satisfied, it is possible to reduce the fluctuation component of the interference intensity caused by the third interference (interference between light reflected twice by the third light attenuation filter (light attenuation filter 10) and light reflected twice by a layer (e.g., an air layer) between the third light attenuation filter (light attenuation filter 10) and the fourth light attenuation filter (light attenuation filter 20)). The measured value measured by the photodetector 8 is given by the product of the spectrum of the relative interference intensity caused by the third interference (see FIG. 20) and the spectral responsivity spectrum of the photodetector element 9 (see FIG. 22). The left side of conditional expression (12) is the half-width Δλ of the spectral responsivity spectrum of the photodetector element 9. a 20. If conditional expression (12) is satisfied, a high averaging effect of the interference waveform can be obtained, and fluctuations in the interference intensity caused by the third interference can be reduced.

[0093] Specifically, the fluctuation in the measurement value of the photometric device 1 due to the third interference when the relative tilt angle θ between the third light attenuation filter (light attenuation filter 10) and the fourth light attenuation filter (light attenuation filter 20) changes from 0.0° to 0.1° is 0.00%. Therefore, even if the relative tilt angle θ between the third light attenuation filter and the fourth light attenuation filter changes slightly, the fluctuation in the interference intensity due to the third interference (interference between light reflected twice by the third light attenuation filter and light reflected twice by a layer (e.g., an air layer) between the third light attenuation filter and the fourth light attenuation filter) is reduced, and the light to be measured can be measured with high accuracy.

[0094] When conditional expression (13) is satisfied, similarly to when conditional expression (12) is satisfied, it is possible to reduce the fluctuation component of the interference intensity caused by the third interference (interference between light reflected twice by the fourth light-attenuating filter (light-attenuating filter 20) and light reflected twice by a layer (e.g., an air layer) between the third light-attenuating filter (light-attenuating filter 10) and the fourth light-attenuating filter). As a result, even if the relative tilt angle θ between the third light-attenuating filter and the fourth light-attenuating filter changes slightly, the interference intensity caused by the third interference hardly changes. Specifically, when the relative tilt angle θ between the third light-attenuating filter and the fourth light-attenuating filter changes from 0.0° to 0.1°, the fluctuation in the measurement value of the photometric device 1 caused by the third interference is 0.00%. Therefore, even if the relative tilt angle θ between the third light-attenuating filter and the fourth light-attenuating filter changes slightly, the fluctuation in the interference intensity caused by the third interference is reduced, and the light to be measured can be measured with high accuracy.

[0095] The measurement value fluctuation of the photometric device 1 of this embodiment is given by the sum of the measurement value fluctuation caused by the first interference, the measurement value fluctuation caused by the second interference, and the measurement value fluctuation caused by the third interference. The measurement value fluctuation of the photometric device 1 of this embodiment is 0.00%. If the absolute value of the measurement value fluctuation of the photometric device 1 is within 5%, the measured light can be measured with high accuracy. It is more preferable if the absolute value of the measurement value fluctuation of the photometric device 1 is within 1%. Since the absolute value of the measurement value fluctuation of the photometric device 1 of this embodiment is within 1%, the measured light can be measured with high accuracy.

[0096] Example 3 The photometric device 1 of this embodiment is similar to the photometric device 1 of the first embodiment, but differs mainly in the following points: There is no distribution of the angle of incidence of light incident on the variable optical attenuator 4, and the angle of incidence of light on the variable optical attenuator 4 is 5° (see Table 4). The half-width Δλ of the spectral responsivity spectrum of the photodetector 9 a is 20 nm (see Table 4). The line width Δλ of the light (measured light) emitted from the object 2 to be measured b is 1 nm (see Table 4 and Figure 23).

[0097] [Table 4]

[0098] Line width Δλ of the light (measured light) emitted from the object 2 b is the half-width Δλ of the spectral responsivity spectrum of the photodetector element 9 a Since the interference intensity fluctuation component caused by the interference between the multiple reflected lights is sufficiently smaller than the above (b) half width Δλ of the spectral responsivity spectrum of the photodetector element 9, the reduction of the interference intensity fluctuation component caused by the interference between the multiple reflected lights is a and (c) the line width Δλ of the light (measured light) emitted from the object 2 to be measured. b Among these, (c) the line width Δλ of the light (measured light) emitted from the object 2 to be measured b In this embodiment, since there is no distribution of the incident angle of the light to be measured incident on the variable optical attenuator 4, there is no reduction in the fluctuation component of the interference intensity caused by the interference between a plurality of multiple reflected lights due to the distribution of the incident angle of the light to be measured incident on the variable optical attenuator 4. In this embodiment, the linewidth Δλ of the light (light to be measured) emitted from the object to be measured 2 is b The present invention considers the reduction of fluctuation components of interference intensity caused by first interference, second interference, and third interference among a plurality of multiple reflected lights.

[0099] <Line width Δλ of the light (measured light) emitted from the object 2 b Reduction of the fluctuation component of the interference intensity caused by the first interference by In this embodiment, the following conditional expression (3) is satisfied.

[0100] OPD 13 ×(1 / λ-1 / (λ+Δλ b ))>0.5 …(3) OPD 13 =|OP 1220 -OP 1022 λ is the wavelength of light included in the measurable wavelength range of the photometric device 1. Δλ b is the line width of the light (measurement light) emitted from the object 2 under test.

[0101] OP 1220is the optical path length of light that is reflected twice by the first light attenuation filter (light attenuation filter 10) and passes through the second light attenuation filter (light attenuation filter 20) without being reflected by the second light attenuation filter (see FIG. 5). 1022 is the optical path length of light that passes through the first light-attenuating filter without being reflected by the first light-attenuating filter and is reflected twice by the second light-attenuating filter (see FIG. 5).

[0102] In this embodiment, when the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 5), OPD 13 ×(1 / λ-1 / (λ+Δλ b When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 6), the OPD 13 ×(1 / λ-1 / (λ+Δλ b )) is 1.750. Therefore, this embodiment satisfies conditional expression (3).

[0103] When conditional expression (3) is satisfied, it is possible to reduce the fluctuation component of the interference intensity caused by the first interference (interference between light reflected twice by the first light attenuation filter (light attenuation filter 10) and light reflected twice by the second light attenuation filter (light attenuation filter 20)). The measured value measured by the photodetector 8 is given by the product of the spectrum of the relative interference intensity caused by the first interference (see FIG. 16) and the spectrum of the light (measured light) emitted from the object to be measured 2 (see FIG. 23). The left side of conditional expression (3) is the linewidth Δλ of the light (measured light) emitted from the object to be measured 2 shown in FIG. 23. b 16. If conditional expression (3) is satisfied, a high averaging effect of the interference waveform can be obtained, and fluctuations in the relative interference intensity caused by the first interference can be reduced.

[0104] Specifically, the fluctuation in the measurement value of the photometric device 1 due to the first interference (interference between light reflected twice by the first light attenuation filter and light reflected twice by the second light attenuation filter) when the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) changes from 0.0° to 0.1° is 0.00%. Therefore, even if the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter changes slightly, the fluctuation in interference intensity due to the first interference is reduced, and the light to be measured can be measured with high accuracy.

[0105] <Line width Δλ of the light (measured light) emitted from the object 2 b Reduction of the fluctuation component of the interference intensity caused by the second interference> In this embodiment, the following conditional expressions (8) and (9) are satisfied: OPD 21 ×(1 / λ-1 / (λ+Δλ b ))>0.5 …(8) OPD 22 ×(1 / λ-1 / (λ+Δλ b ))>0.5 …(9) OPD 21 =|OP 1420 -OP 1022 | OPD 22 =|OP 1024 -OP 1220 |

[0106] OP 1420 is the optical path length of light that is reflected four times by the first light attenuation filter (light attenuation filter 10) and passes through the second light attenuation filter (light attenuation filter 20) without being reflected by the second light attenuation filter (see FIGS. 7 and 9). 1022 is the optical path length of light that passes through the first light attenuating filter without being reflected by the first light attenuating filter and is reflected twice by the second light attenuating filter (see Figures 7 and 9). 1024 is the optical path length of light that passes through the first light attenuating filter without being reflected by the first light attenuating filter and is reflected four times by the second light attenuating filter (see Figures 8 and 10). 1220is the optical path length of light that is reflected twice by the first light-attenuating filter and passes through the second light-attenuating filter without being reflected by the second light-attenuating filter (see FIGS. 8 and 10).

[0107] In this embodiment, when the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 7), OPD 21 ×(1 / λ-1 / (λ+Δλ b When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 9), the OPD 21 ×(1 / λ-1 / (λ+Δλ b )) is 1.500. Therefore, this embodiment satisfies conditional expression (8). When the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter is 0.0° (see FIG. 8), OPD 22 ×(1 / λ-1 / (λ+Δλ b When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 10), the OPD 22 ×(1 / λ-1 / (λ+Δλ b )) is 6.749. Therefore, this embodiment satisfies conditional expression (9).

[0108] When conditional expression (8) is satisfied, it is possible to reduce the fluctuation component of the interference intensity caused by the second interference (interference between the light reflected twice by the first light attenuation filter (light attenuation filter 10) and the light reflected twice by the second light attenuation filter (light attenuation filter 20)). The measured value measured by the photodetector 8 is given by the product of the spectrum of the relative interference intensity caused by the second interference (see FIG. 18) and the spectrum of the light (measured light) emitted from the object to be measured 2 (see FIG. 23). The left side of conditional expression (8) is the linewidth Δλ of the light (measured light) emitted from the object to be measured 2 shown in FIG. 23. b18 is included within the specified period. If conditional expression (8) is satisfied, a high averaging effect of the interference waveform can be obtained, and fluctuations in the interference intensity due to the second interference can be reduced.

[0109] Specifically, the fluctuation in the measurement value of the photometric device 1 due to the second interference when the relative tilt angle θ between the first light-attenuating filter (light-attenuating filter 10) and the second light-attenuating filter (light-attenuating filter 20) changes from 0.0° to 0.1° is 0.00%. Therefore, even if the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes slightly, the fluctuation in the interference intensity due to the second interference (interference between the light reflected twice by the first light-attenuating filter and the light reflected twice by the second light-attenuating filter) is reduced, and the light to be measured can be measured with high accuracy.

[0110] When conditional expression (9) is satisfied, similarly to when conditional expression (8) is satisfied, it is possible to reduce the fluctuation component of the interference intensity caused by the second interference (interference between light reflected twice by the first light-attenuating filter (light-attenuating filter 10) and light reflected four times by the second light-attenuating filter (light-attenuating filter 20)). As a result, even if the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes slightly, the interference intensity caused by the second interference hardly changes. Specifically, when the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes from 0.0° to 0.1°, the fluctuation in the measurement value of the photometric device 1 caused by the second interference is 0.00%. Therefore, even if the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes slightly, the fluctuation in the interference intensity caused by the second interference is reduced, and the light to be measured can be measured with high accuracy.

[0111] <Line width Δλ of the light (measured light) emitted from the object 2 b Reduction of the fluctuation component of the interference intensity caused by the third interference by In this embodiment, the following conditional expressions (14) and (15) are satisfied. OPD g1 ×(1 / λ-1 / (λ+Δλ b ))>0.5 …(14) OPDg2 ×(1 / λ-1 / (λ+Δλ b ))>0.5 …(15) OPD g1 =|OP 3240 -OP 30G240 | OPD g2 =|OP 3042 -OP 30G240 |

[0112] OP 3240 is the optical path length of light that is reflected twice by the third light attenuation filter (light attenuation filter 10) and passes through the fourth light attenuation filter (light attenuation filter 20) without being reflected by the fourth light attenuation filter. 30G240 is the optical path length of light that passes through the third and fourth light attenuation filters without being reflected by them and is reflected twice by a layer (for example, an air layer) between the third and fourth light attenuation filters. 3042 is the optical path length of light that passes through the third light attenuating filter without being reflected by the third light attenuating filter and is reflected twice by the fourth light attenuating filter.

[0113] In this embodiment, when the relative tilt angle θ between the third light attenuation filter (light attenuation filter 10) and the fourth light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 11), OPD g1 ×(1 / λ-1 / (λ+Δλ b When the relative tilt angle θ between the third and fourth light attenuation filters is 0.1° (see FIG. 13), the OPD g1 ×(1 / λ-1 / (λ+Δλ b )) is 6.562. Therefore, this embodiment satisfies conditional expression (14). When the relative tilt angle θ between the third light attenuation filter and the fourth light attenuation filter is 0.0° (see FIG. 12), OPD g1 ×(1 / λ-1 / (λ+Δλ bWhen the relative tilt angle θ between the third and fourth light attenuation filters is 0.1° (see FIG. 14), the OPD g1 ×(1 / λ-1 / (λ+Δλ b )) is 4.812. Therefore, this embodiment satisfies conditional expression (15).

[0114] When conditional expression (14) is satisfied, it is possible to reduce the fluctuation component of the interference intensity caused by the third interference (interference between light reflected twice by the third light attenuation filter (light attenuation filter 10) and light reflected twice by a layer (e.g., an air layer) between the third light attenuation filter and the fourth light attenuation filter (light attenuation filter 20)). The measured value measured by the photodetector 8 is given by the product of the spectrum of the relative interference intensity caused by the third interference (see FIG. 20) and the spectrum of the light (measured light) emitted from the object to be measured 2 (see FIG. 23). The left side of conditional expression (14) is the linewidth Δλ of the light (measured light) emitted from the object to be measured 2 shown in FIG. 23. b 20. If conditional expression (14) is satisfied, a high averaging effect of the interference waveform can be obtained, and fluctuations in the interference intensity caused by the third interference can be reduced.

[0115] Specifically, the fluctuation in the measurement value of the photometric device 1 due to the third interference when the relative tilt angle θ between the third light attenuation filter (light attenuation filter 10) and the fourth light attenuation filter (light attenuation filter 20) changes from 0.0° to 0.1° is 0.00%. Therefore, even if the relative tilt angle θ between the third light attenuation filter and the fourth light attenuation filter changes slightly, the fluctuation in the interference intensity due to the third interference (interference between light reflected twice by the third light attenuation filter and light reflected twice by a layer (e.g., an air layer) between the third light attenuation filter and the fourth light attenuation filter) is reduced, and the light to be measured can be measured with high accuracy.

[0116] When conditional expression (15) is satisfied, similarly to when conditional expression (14) is satisfied, the fluctuation component of the interference intensity caused by the third interference (interference between light reflected twice by the fourth light-attenuating filter (light-attenuating filter 20) and light reflected twice by a layer (e.g., an air layer) between the third light-attenuating filter (light-attenuating filter 10) and the fourth light-attenuating filter) can be reduced. As a result, even if the relative tilt angle θ between the third light-attenuating filter and the fourth light-attenuating filter changes slightly, the interference intensity caused by the third interference hardly changes. Specifically, when the relative tilt angle θ between the third light-attenuating filter and the fourth light-attenuating filter changes from 0.0° to 0.1°, the fluctuation in the measurement value of the photometric device 1 caused by the third interference is 0.00%. Therefore, even if the relative tilt angle θ between the third light-attenuating filter and the fourth light-attenuating filter changes slightly, the fluctuation in the interference intensity caused by the third interference is reduced, and the light to be measured can be measured with high accuracy.

[0117] The measurement value fluctuation of the photometric device 1 of this embodiment is given by the sum of the measurement value fluctuation caused by the first interference, the measurement value fluctuation caused by the second interference, and the measurement value fluctuation caused by the third interference. The measurement value fluctuation of the photometric device 1 of this embodiment is 0.00%. If the absolute value of the measurement value fluctuation of the photometric device 1 is within 5%, the measured light can be measured with high accuracy. It is more preferable if the absolute value of the measurement value fluctuation of the photometric device 1 is within 1%. Since the absolute value of the measurement value fluctuation of the photometric device 1 of this embodiment is within 1%, the measured light can be measured with high accuracy.

[0118] <Examples 4, 5, and 6> Examples 4 to 6 will be described with reference to Figures 1 to 23. The photometric devices 1 of Examples 4 to 6 have the same configuration as the photometric devices 1 of Examples 1 to 3, but differ mainly in the following respects.

[0119] The configuration of the variable optical attenuator 4 of Examples 4 to 6 is as shown in Table 5. Therefore, the optical path length of the transparent substrate 11 is different from the optical path length of the transparent substrate 21.

[0120] [Table 5]

[0121] Example 4 The distribution of the incident angle of light incident on the variable optical attenuator 4 of this embodiment, and the half-width Δλ of the spectral responsivity spectrum of the photodetector element 9 a , and the line width Δλ of the light (measured light) emitted from the object 2 to be measured b are the distribution of the incident angle of light incident on the variable optical attenuator 4 of Example 1, and the half-width Δλ of the spectral responsivity spectrum of the photodetector element 9, respectively. a , and the line width Δλ of the light (measured light) emitted from the object 2 to be measured b (See Table 2.) Therefore, in this embodiment, similarly to the first embodiment, a consideration is made on the reduction of the fluctuation components of the interference intensity caused by the first interference, the second interference, and the third interference among a plurality of multiple reflected light beams due to the distribution of the incident angles of the light under measurement incident on the variable optical attenuator 4 (a).

[0122] <Reduction of the fluctuation component of the interference intensity caused by the first interference due to the distribution of the incident angle of the light under measurement incident on the variable optical attenuator 4> In this embodiment, when the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 5), |OPD θmax1 -OPD θmin1 | / λ is 5.101. When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 6), |OPD θmax1 -OPD θmin1 | / λ is 4.898. Therefore, this embodiment satisfies conditional expression (1). The fluctuation in the measurement value of the photometric device 1 due to the first interference (interference between light reflected twice by the first light attenuation filter and light reflected twice by the second light attenuation filter) when the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter changes from 0.0° to 0.1° is −0.03%.

[0123] <Reduction of the fluctuation component of the interference intensity caused by the second interference due to the distribution of the incident angle of the light under measurement incident on the variable optical attenuator 4> In this embodiment, when the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 7), |OPD θmax2 -OPD θmin2 | / λ is 0.000. When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 9), |OPD θmax2 -OPD θmin2 | / λ is 0.203. Therefore, this embodiment does not satisfy conditional expression (4). The variation in the measurement value of the photometric device 1 due to the second interference (interference between light reflected four times by the first light-attenuating filter and light reflected twice by the second light-attenuating filter) when the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes from 0.0° to 0.1° is −0.20%.

[0124] When the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 8), |OPD θmax3 -OPD θmin3 | / λ is 15.303. When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 10), |OPD θmax3 -OPD θmin3 | / λ is 14.897. Therefore, this embodiment satisfies conditional expression (5). The variation in the measurement value of the photometric device 1 due to the second interference (interference between light reflected twice by the first light attenuation filter and light reflected four times by the second light attenuation filter) when the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter changes from 0.0° to 0.1° is 0.00%.

[0125] <Reduction of the fluctuation component of the interference intensity caused by the third interference due to the distribution of the incident angle of the light under measurement incident on the variable optical attenuator 4> In this embodiment, when the relative tilt angle θ between the third light attenuation filter (light attenuation filter 10) and the fourth light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 13), |OPD θmax4 -OPD θmin4 | / λ is 5.038. When the relative tilt angle θ between the third light attenuation filter and the fourth light attenuation filter is 0.1° (see FIG. 16), |OPD θmax4 -OPD θmin4 | / λ is 5.243. Therefore, this embodiment satisfies conditional expression (10). When the relative tilt angle θ between the third light-attenuating filter and the fourth light-attenuating filter changes from 0.0° to 0.1°, the fluctuation in the measurement value of the photometric device 1 due to third interference (interference between light reflected twice by the third light-attenuating filter and light reflected twice by a layer (e.g., an air layer) between the third light-attenuating filter and the fourth light-attenuating filter) is 0.03%.

[0126] When the relative tilt angle θ between the third light attenuation filter (light attenuation filter 10) and the fourth light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 12), |OPD θmax5 -OPD θmin5 | is 0.063. When the relative tilt angle θ between the third light attenuation filter and the fourth light attenuation filter is 0.1° (see FIG. 10), |OPD θmax5 -OPD θmin5 | is 0.244. Therefore, this embodiment does not satisfy conditional expression (11). When the relative tilt angle θ between the third light-attenuating filter and the fourth light-attenuating filter changes from 0.0° to 0.1°, the variation in the measurement value of the photometric device 1 due to the third interference (interference between light reflected twice by the fourth light-attenuating filter and light reflected twice by a layer (e.g., an air layer) between the third light-attenuating filter and the fourth light-attenuating filter) is −2.04%.

[0127] The measurement value fluctuation of the photometric device 1 of this embodiment is given by the sum of the measurement value fluctuation due to the first interference, the measurement value fluctuation due to the second interference, and the measurement value fluctuation due to the third interference. The measurement value fluctuation of the photometric device 1 of this embodiment is -2.24%. Since the absolute value of the measurement value fluctuation of the photometric device 1 of this embodiment is within 5%, the measured light can be measured with high accuracy. The absolute value of the measurement value fluctuation of the photometric device 1 of this embodiment is larger than the absolute value of the measurement value fluctuation of the photometric device 1 of embodiment 1. Therefore, the photometric device 1 of embodiment 1 is more preferable than the photometric device 1 of this embodiment.

[0128] <Example 5> The incident angle of light to the variable optical attenuator 4 of this embodiment, and the half width Δλ of the spectral responsivity spectrum of the photodetector element 9 a , and the line width Δλ of the light (measured light) emitted from the object 2 to be measured b are the incident angle of light to the variable optical attenuator 4 of Example 2, and the half width Δλ of the spectral responsivity spectrum of the photodetector element 9, respectively. a , and the line width Δλ of the light (measured light) emitted from the object 2 to be measured b (See Table 3.) Therefore, in this embodiment, as in the second embodiment, the half width Δλ of the spectral responsivity spectrum of the photodetector 9 (b) is the same as a The present invention considers the reduction of fluctuation components of interference intensity caused by first interference, second interference, and third interference among a plurality of multiple reflected lights.

[0129] <Frequency width Δλ of the spectral response spectrum of the photodetector element 9 a Reduction of the fluctuation component of the interference intensity caused by the first interference by In this embodiment, when the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 5), OPD 12 ×(1 / λ-1 / (λ+Δλ a When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 6), the OPD 12 ×(1 / λ-1 / (λ+Δλ a)) is 7.480. Therefore, this embodiment satisfies conditional expression (2). The fluctuation in the measurement value of the photometric device 1 due to the first interference (interference between light reflected twice by the first light-attenuating filter and light reflected twice by the second light-attenuating filter) when the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes from 0.0° to 0.1° is 0.00%.

[0130] <Frequency width Δλ of the spectral response spectrum of the photodetector element 9 a Reduction of the fluctuation component of the interference intensity caused by the second interference> In this embodiment, when the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 7), OPD 21 ×(1 / λ-1 / (λ+Δλ a When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 9), the OPD 21 ×(1 / λ-1 / (λ+Δλ a )) is 0.001. Therefore, this embodiment does not satisfy conditional expression (6). The variation in the measurement value of the photometric device 1 due to the second interference (interference between light reflected four times by the first light-attenuating filter and light reflected twice by the second light-attenuating filter) when the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes from 0.0° to 0.1° is −0.20%.

[0131] When the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 8), OPD 21 ×(1 / λ-1 / (λ+Δλ a When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 10), the OPD 21 ×(1 / λ-1 / (λ+Δλ a)) is 22.440. Therefore, this embodiment satisfies conditional expression (7). The variation in the measurement value of the photometric device 1 due to the second interference (interference between light reflected twice by the first light-attenuating filter and light reflected four times by the second light-attenuating filter) when the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes from 0.0° to 0.1° is 0.00%.

[0132] <Frequency width Δλ of the spectral response spectrum of the photodetector element 9 a Reduction of the fluctuation component of the interference intensity caused by the third interference by In this embodiment, when the relative tilt angle θ between the third light attenuation filter (light attenuation filter 10) and the fourth light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 11), OPD g1 ×(1 / λ-1 / (λ+Δλ a When the relative tilt angle θ between the third and fourth light attenuation filters is 0.1° (see FIG. 13), the OPD g1 ×(1 / λ-1 / (λ+Δλ a )) is 7.395. Therefore, this embodiment satisfies conditional expression (12). When the relative tilt angle θ between the third light-attenuating filter and the fourth light-attenuating filter changes from 0.0° to 0.1°, the fluctuation in the measurement value of the photometric device 1 due to the third interference (interference between light reflected twice by the third light-attenuating filter and light reflected twice by a layer (e.g., an air layer) between the third light-attenuating filter and the fourth light-attenuating filter) is 0.00%.

[0133] When the relative tilt angle θ between the third light attenuation filter (light attenuation filter 10) and the fourth light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 12), the OPD g2 ×(1 / λ-1 / (λ+Δλ a When the relative tilt angle θ between the third light attenuation filter and the fourth light attenuation filter is 0.1° (see FIG. 14), the OPD g2 ×(1 / λ-1 / (λ+Δλ a)) is 0.085. Therefore, this embodiment does not satisfy conditional expression (13). When the relative tilt angle θ between the third light-attenuating filter and the fourth light-attenuating filter changes from 0.0° to 0.1°, the measurement value fluctuation of the photometric device 1 due to the third interference (interference between light reflected twice by the fourth light-attenuating filter and light reflected twice by a layer (e.g., an air layer) between the third light-attenuating filter and the fourth light-attenuating filter) is 1.37%.

[0134] The measurement value fluctuation of the photometric device 1 of this embodiment is given by the sum of the measurement value fluctuation due to the first interference, the measurement value fluctuation due to the second interference, and the measurement value fluctuation due to the third interference. The measurement value fluctuation of the photometric device 1 of this embodiment is 1.16%. Since the absolute value of the measurement value fluctuation of the photometric device 1 of this embodiment is within 5%, the measured light can be measured with high accuracy. The absolute value of the measurement value fluctuation of the photometric device 1 of this embodiment is larger than the absolute value of the measurement value fluctuation of the photometric device 1 of embodiment 2. Therefore, the photometric device 1 of embodiment 2 is more preferable than the photometric device 1 of this embodiment.

[0135] Example 6 The incident angle of light to the variable optical attenuator 4 of this embodiment, and the half width Δλ of the spectral responsivity spectrum of the photodetector element 9 a , and the line width Δλ of the light (measured light) emitted from the object 2 to be measured b are the incident angle of light to the variable optical attenuator 4 of Example 3, and the half-width Δλ of the spectral responsivity spectrum of the photodetector element 9, respectively. a , and the line width Δλ of the light (measured light) emitted from the object 2 to be measured b (See Table 4.) Therefore, in this embodiment, as in the third embodiment, the line width Δλ of the light (measured light) emitted from the object 2 under test is b The present invention considers the reduction of fluctuation components of interference intensity caused by first interference, second interference, and third interference among a plurality of multiple reflected lights.

[0136] <Line width Δλ of the light (measured light) emitted from the object 2 b Reduction of the fluctuation component of the interference intensity caused by the first interference by In this embodiment, when the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 5), OPD 13 ×(1 / λ-1 / (λ+Δλ b When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 6), the OPD 13 ×(1 / λ-1 / (λ+Δλ b )) is 2.500. Therefore, this embodiment satisfies conditional expression (3). The fluctuation in the measurement value of the photometric device 1 due to the first interference (interference between light reflected twice by the first light-attenuating filter and light reflected twice by the second light-attenuating filter) when the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes from 0.0° to 0.1° is 0.00%.

[0137] <Line width Δλ of the light (measured light) emitted from the object 2 b Reduction of the fluctuation component of the interference intensity caused by the second interference> In this embodiment, when the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 7), OPD 21 ×(1 / λ-1 / (λ+Δλ b When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 9), the OPD 21 ×(1 / λ-1 / (λ+Δλ b )) is 0.000. Therefore, this embodiment does not satisfy conditional expression (8). The variation in the measurement value of the photometric device 1 due to the second interference (interference between light reflected four times by the first light-attenuating filter and light reflected twice by the second light-attenuating filter) when the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes from 0.0° to 0.1° is −0.20%.

[0138] When the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 8), OPD 22 ×(1 / λ-1 / (λ+Δλ b When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 10), the OPD 22 ×(1 / λ-1 / (λ+Δλ b )) is 7.499. Therefore, this embodiment satisfies conditional expression (9). The variation in the measurement value of the photometric device 1 due to the second interference (interference between light reflected twice by the first light-attenuating filter and light reflected four times by the second light-attenuating filter) when the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes from 0.0° to 0.1° is 0.00%.

[0139] <Line width Δλ of the light (measured light) emitted from the object 2 b Reduction of the fluctuation component of the interference intensity caused by the third interference by In this embodiment, when the relative tilt angle θ between the third light attenuation filter (light attenuation filter 10) and the fourth light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 11), OPD g1 ×(1 / λ-1 / (λ+Δλ b When the relative tilt angle θ between the third light attenuation filter and the fourth light attenuation filter is 0.1° (see FIG. 13), the OPD g1 ×(1 / λ-1 / (λ+Δλ b )) is 2.471. Therefore, this embodiment satisfies conditional expression (14). When the relative tilt angle θ between the third light-attenuating filter and the fourth light-attenuating filter changes from 0.0° to 0.1°, the fluctuation in the measurement value of the photometric device 1 due to the third interference (interference between light reflected twice by the third light-attenuating filter and light reflected twice by a layer (e.g., an air layer) between the third light-attenuating filter and the fourth light-attenuating filter) is 0.00%.

[0140] When the relative tilt angle θ between the third light attenuation filter (light attenuation filter 10) and the fourth light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 12), the OPD g1 ×(1 / λ-1 / (λ+Δλ b When the relative tilt angle θ between the third light attenuation filter and the fourth light attenuation filter is 0.1° (see FIG. 14), the OPD g1 ×(1 / λ-1 / (λ+Δλ b )) is 0.028. Therefore, this embodiment does not satisfy conditional expression (15). When the relative tilt angle θ between the third light-attenuating filter and the fourth light-attenuating filter changes from 0.0° to 0.1°, the measurement value fluctuation of the photometric device 1 due to the third interference (interference between light reflected twice by the fourth light-attenuating filter and light reflected twice by a layer (e.g., an air layer) between the third light-attenuating filter and the fourth light-attenuating filter) is 2.30%.

[0141] The measurement value fluctuation of the photometric device 1 of this embodiment is given by the sum of the measurement value fluctuation due to the first interference, the measurement value fluctuation due to the second interference, and the measurement value fluctuation due to the third interference. The measurement value fluctuation of the photometric device 1 of this embodiment is 2.10%. Since the absolute value of the measurement value fluctuation of the photometric device 1 of this embodiment is within 5%, the measured light can be measured with high accuracy. The absolute value of the measurement value fluctuation of the photometric device 1 of this embodiment is larger than the absolute value of the measurement value fluctuation of the photometric device 1 of embodiment 3. Therefore, the photometric device 1 of embodiment 3 is more preferable than the photometric device 1 of this embodiment.

[0142] <Examples 7, 8, and 9> Examples 7 to 9 will be described with reference to Figures 1 to 23. The photometric devices 1 of Examples 7 to 9 have the same configuration as the photometric devices 1 of Examples 1 to 3, but differ mainly in the following points.

[0143] The configuration of the variable optical attenuator 4 of Examples 7 to 9 is as shown in Table 6. Therefore, the optical path length of the transparent substrate 11 is different from the optical path length of the transparent substrate 21.

[0144] [Table 6]

[0145] Example 7 The distribution of the incident angle of light incident on the variable optical attenuator 4 of this embodiment, and the half-width Δλ of the spectral responsivity spectrum of the photodetector element 9 a , and the line width Δλ of the light (measured light) emitted from the object 2 to be measured b are the distribution of the incident angle of light incident on the variable optical attenuator 4 of Example 1, and the half-width Δλ of the spectral responsivity spectrum of the photodetector element 9, respectively. a , and the line width Δλ of the light (measured light) emitted from the object 2 to be measured b (See Table 2.) Therefore, in this embodiment, similarly to the first embodiment, a consideration is made on the reduction of the fluctuation components of the interference intensity caused by the first interference, the second interference, and the third interference among a plurality of multiple reflected light beams due to the distribution of the incident angles of the light under measurement incident on the variable optical attenuator 4 (a).

[0146] <Reduction of the fluctuation component of the interference intensity caused by the first interference due to the distribution of the incident angle of the light under measurement incident on the variable optical attenuator 4> In this embodiment, when the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 5), |OPD θmax1 -OPD θmin1 | / λ is 2.040. When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 6), |OPD θmax1 -OPD θmin1 | / λ is 1.838. Therefore, this embodiment satisfies conditional expression (1). The fluctuation in the measurement value of the photometric device 1 due to the first interference (interference between light reflected twice by the first light-attenuating filter and light reflected twice by the second light-attenuating filter) when the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes from 0.0° to 0.1° is −0.05%.

[0147] <Reduction of the fluctuation component of the interference intensity caused by the second interference due to the distribution of the incident angle of the light under measurement incident on the variable optical attenuator 4> In this embodiment, when the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 7), |OPD θmax2 -OPD θmin2 | / λ is 6.121. When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 9), |OPD θmax2 -OPD θmin2 | / λ is 5.797. Therefore, this embodiment satisfies conditional expression (4). The fluctuation in the measurement value of the photometric device 1 due to the second interference (interference between light reflected four times by the first light attenuation filter and light reflected twice by the second light attenuation filter) when the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter changes from 0.0° to 0.1° is 0.00%.

[0148] When the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 8), |OPD θmax3 -OPD θmin3 | / λ is 12.242. When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 10), |OPD θmax3 -OPD θmin3 | / λ is 11.837. Therefore, this embodiment satisfies conditional expression (5). The fluctuation in the measurement value of the photometric device 1 due to the second interference (interference between light reflected twice by the first light attenuation filter and light reflected four times by the second light attenuation filter) when the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter changes from 0.0° to 0.1° is 0.00%.

[0149] <Reduction of the fluctuation component of the interference intensity caused by the third interference due to the distribution of the incident angle of the light under measurement incident on the variable optical attenuator 4> In this embodiment, when the relative tilt angle θ between the third light attenuation filter (light attenuation filter 10) and the fourth light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 13), |OPD θmax4 -OPD θmin4 | / λ is 0.362. When the relative tilt angle θ between the third light attenuation filter and the fourth light attenuation filter is 0.1° (see FIG. 16), |OPD θmax4 -OPD θmin4 | / λ is 0.120. Therefore, this embodiment does not satisfy conditional expression (10). When the relative tilt angle θ between the third light-attenuating filter and the fourth light-attenuating filter changes from 0.0° to 0.1°, the measurement value fluctuation of the photometric device 1 due to the third interference (interference between light reflected twice by the third light-attenuating filter and light reflected twice by a layer (e.g., an air layer) between the third light-attenuating filter and the fourth light-attenuating filter) is −2.41%.

[0150] When the relative tilt angle θ between the third light attenuation filter (light attenuation filter 10) and the fourth light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 12), |OPD θmax5 -OPD θmin5 | is 2.402. When the relative tilt angle θ between the third light attenuation filter and the fourth light attenuation filter is 0.1° (see FIG. 10), |OPD θmax5 -OPD θmin5 | is 2.120. Therefore, this embodiment satisfies conditional expression (11). When the relative tilt angle θ between the third light-attenuating filter and the fourth light-attenuating filter changes from 0.0° to 0.1°, the fluctuation in the measurement value of the photometric device 1 due to the third interference (interference between light reflected twice by the fourth light-attenuating filter and light reflected twice by a layer (e.g., an air layer) between the third light-attenuating filter and the fourth light-attenuating filter) is 0.07%.

[0151] The measurement value fluctuation of the photometric device 1 of this embodiment is given by the sum of the measurement value fluctuation due to the first interference, the measurement value fluctuation due to the second interference, and the measurement value fluctuation due to the third interference. The measurement value fluctuation of the photometric device 1 of this embodiment is -2.39%. Since the absolute value of the measurement value fluctuation of the photometric device 1 of this embodiment is within 5%, the measured light can be measured with high accuracy. The absolute value of the measurement value fluctuation of the photometric device 1 of this embodiment is larger than the absolute value of the measurement value fluctuation of the photometric device 1 of embodiment 1. Therefore, the photometric device 1 of embodiment 1 is more preferable than the photometric device 1 of this embodiment.

[0152] Example 8 The incident angle of light to the variable optical attenuator 4 of this embodiment, and the half width Δλ of the spectral responsivity spectrum of the photodetector element 9 a , and the line width Δλ of the light (measured light) emitted from the object 2 to be measured b are the incident angle of light to the variable optical attenuator 4 of Example 2, and the half width Δλ of the spectral responsivity spectrum of the photodetector element 9, respectively. a , and the line width Δλ of the light (measured light) emitted from the object 2 to be measured b (See Table 3.) Therefore, in this embodiment, as in the second embodiment, the half width Δλ of the spectral responsivity spectrum of the photodetector 9 (b) is the same as a The present invention considers the reduction of fluctuation components of interference intensity caused by first interference, second interference, and third interference among a plurality of multiple reflected lights.

[0153] <Frequency width Δλ of the spectral response spectrum of the photodetector element 9 a Reduction of the fluctuation component of the interference intensity caused by the first interference by In this embodiment, when the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 5), OPD 12 ×(1 / λ-1 / (λ+Δλ a When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 6), the OPD 12 ×(1 / λ-1 / (λ+Δλ a)) is 2.993. Therefore, this embodiment satisfies conditional expression (2). The fluctuation in the measurement value of the photometric device 1 due to the first interference (interference between light reflected twice by the first light-attenuating filter and light reflected twice by the second light-attenuating filter) when the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes from 0.0° to 0.1° is 0.00%.

[0154] <Frequency width Δλ of the spectral response spectrum of the photodetector element 9 a Reduction of the fluctuation component of the interference intensity caused by the second interference> In this embodiment, when the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 7), OPD 21 ×(1 / λ-1 / (λ+Δλ a When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 9), the OPD 21 ×(1 / λ-1 / (λ+Δλ a )) is 8.977. Therefore, this embodiment satisfies conditional expression (6). The variation in the measurement value of the photometric device 1 due to the second interference (interference between light reflected four times by the first light-attenuating filter and light reflected twice by the second light-attenuating filter) when the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes from 0.0° to 0.1° is 0.00%.

[0155] When the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 8), OPD 21 ×(1 / λ-1 / (λ+Δλ a When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 10), the OPD 21 ×(1 / λ-1 / (λ+Δλ a)) is 17.952. Therefore, this embodiment satisfies conditional expression (7). The variation in the measurement value of the photometric device 1 due to the second interference (interference between light reflected twice by the first light-attenuating filter and light reflected four times by the second light-attenuating filter) when the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes from 0.0° to 0.1° is 0.00%.

[0156] <Frequency width Δλ of the spectral response spectrum of the photodetector element 9 a Reduction of the fluctuation component of the interference intensity caused by the third interference by In this embodiment, when the relative tilt angle θ between the third light attenuation filter (light attenuation filter 10) and the fourth light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 11), OPD g1 ×(1 / λ-1 / (λ+Δλ a When the relative tilt angle θ between the third light attenuation filter and the fourth light attenuation filter is 0.1° (see FIG. 13), the OPD g1 ×(1 / λ-1 / (λ+Δλ a )) is 0.265. Therefore, this embodiment does not satisfy conditional expression (12). When the relative tilt angle θ between the third light-attenuating filter and the fourth light-attenuating filter changes from 0.0° to 0.1°, the variation in the measurement value of the photometric device 1 due to the third interference (interference between light reflected twice by the third light-attenuating filter and light reflected twice by a layer (e.g., an air layer) between the third light-attenuating filter and the fourth light-attenuating filter) is 2.74%.

[0157] When the relative tilt angle θ between the third light attenuation filter (light attenuation filter 10) and the fourth light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 12), the OPD g2 ×(1 / λ-1 / (λ+Δλ a When the relative tilt angle θ between the third light attenuation filter and the fourth light attenuation filter is 0.1° (see FIG. 14), the OPD g2 ×(1 / λ-1 / (λ+Δλ a)) is 2.727. Therefore, this embodiment satisfies conditional expression (13). When the relative tilt angle θ between the third light-attenuating filter and the fourth light-attenuating filter changes from 0.0° to 0.1°, the fluctuation in the measurement value of the photometric device 1 due to the third interference (interference between light reflected twice by the fourth light-attenuating filter and light reflected twice by a layer (e.g., an air layer) between the third light-attenuating filter and the fourth light-attenuating filter) is 0.00%.

[0158] The measurement value fluctuation of the photometric device 1 of this embodiment is given by the sum of the measurement value fluctuation caused by the first interference, the measurement value fluctuation caused by the second interference, and the measurement value fluctuation caused by the third interference. The measurement value fluctuation of the photometric device 1 of this embodiment is 2.74%. Since the absolute value of the measurement value fluctuation of the photometric device 1 of this embodiment is within 5%, the measured light can be measured with high accuracy. The absolute value of the measurement value fluctuation of the photometric device 1 of this embodiment is larger than the absolute value of the measurement value fluctuation of the photometric device 1 of embodiment 2. Therefore, the photometric device 1 of embodiment 2 is more preferable than the photometric device 1 of this embodiment.

[0159] Example 9 The incident angle of light to the variable optical attenuator 4 of this embodiment, and the half width Δλ of the spectral responsivity spectrum of the photodetector element 9 a , and the line width Δλ of the light (measured light) emitted from the object 2 to be measured b are the incident angle of light to the variable optical attenuator 4 of Example 3, and the half-width Δλ of the spectral responsivity spectrum of the photodetector element 9, respectively. a , and the line width Δλ of the light (measured light) emitted from the object 2 to be measured b (See Table 4.) Therefore, in this embodiment, as in the third embodiment, the line width Δλ of the light (measured light) emitted from the object 2 under test is b The present invention considers the reduction of fluctuation components of interference intensity caused by first interference, second interference, and third interference among a plurality of multiple reflected lights.

[0160] <Line width Δλ of the light (measured light) emitted from the object 2 b Reduction of the fluctuation component of the interference intensity caused by the first interference by In this embodiment, when the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 5), OPD 13 ×(1 / λ-1 / (λ+Δλ b When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 6), the OPD 13 ×(1 / λ-1 / (λ+Δλ b )) is 1.000. Therefore, this embodiment satisfies conditional expression (3). The fluctuation in the measurement value of the photometric device 1 due to the first interference (interference between light reflected twice by the first light attenuation filter and light reflected twice by the second light attenuation filter) when the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter changes from 0.0° to 0.1° is 0.01%.

[0161] <Line width Δλ of the light (measured light) emitted from the object 2 b Reduction of the fluctuation component of the interference intensity caused by the second interference> In this embodiment, when the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 7), OPD 21 ×(1 / λ-1 / (λ+Δλ b When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 9), the OPD 21 ×(1 / λ-1 / (λ+Δλ b )) is 3.000. Therefore, this embodiment satisfies conditional expression (8). When the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes from 0.0° to 0.1°, the fluctuation in the measurement value of the photometric device 1 due to the second interference (interference between light reflected four times by the first light-attenuating filter and light reflected twice by the second light-attenuating filter) is 0.00%.

[0162] When the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 8), OPD 22 ×(1 / λ-1 / (λ+Δλ b When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 10), the OPD 22 ×(1 / λ-1 / (λ+Δλ b )) is 5.999. Therefore, this embodiment satisfies conditional expression (9). The fluctuation in the measurement value of the photometric device 1 due to the second interference (interference between light reflected twice by the first light-attenuating filter and light reflected four times by the second light-attenuating filter) when the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes from 0.0° to 0.1° is 0.00%.

[0163] <Line width Δλ of the light (measured light) emitted from the object 2 b Reduction of the fluctuation component of the interference intensity caused by the third interference by In this embodiment, when the relative tilt angle θ between the third light attenuation filter (light attenuation filter 10) and the fourth light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 11), OPD g1 ×(1 / λ-1 / (λ+Δλ b When the relative tilt angle θ between the third light attenuation filter and the fourth light attenuation filter is 0.1° (see FIG. 13), the OPD g1 ×(1 / λ-1 / (λ+Δλ b )) is 0.088. Therefore, this embodiment does not satisfy conditional expression (14). When the relative tilt angle θ between the third light-attenuating filter and the fourth light-attenuating filter changes from 0.0° to 0.1°, the fluctuation in the measurement value of the photometric device 1 due to the third interference (interference between light reflected twice by the third light-attenuating filter and light reflected twice by a layer (e.g., an air layer) between the third light-attenuating filter and the fourth light-attenuating filter) is 3.43%.

[0164] When the relative tilt angle θ between the third light attenuation filter (light attenuation filter 10) and the fourth light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 12), the OPD g1 ×(1 / λ-1 / (λ+Δλ b When the relative tilt angle θ between the third light attenuation filter and the fourth light attenuation filter is 0.1° (see FIG. 14), the OPD g1 ×(1 / λ-1 / (λ+Δλ b )) is 0.911. Therefore, this embodiment satisfies conditional expression (15). When the relative tilt angle θ between the third light-attenuating filter and the fourth light-attenuating filter changes from 0.0° to 0.1°, the fluctuation in the measurement value of the photometric device 1 due to the third interference (interference between light reflected twice by the fourth light-attenuating filter and light reflected twice by a layer (e.g., an air layer) between the third light-attenuating filter and the fourth light-attenuating filter) is 0.06%.

[0165] The measurement value fluctuation of the photometric device 1 of this embodiment is given by the sum of the measurement value fluctuation due to the first interference, the measurement value fluctuation due to the second interference, and the measurement value fluctuation due to the third interference. The measurement value fluctuation of the photometric device 1 of this embodiment is 3.50%. Since the absolute value of the measurement value fluctuation of the photometric device 1 of this embodiment is within 5%, the measured light can be measured with high accuracy. The absolute value of the measurement value fluctuation of the photometric device 1 of this embodiment is larger than the absolute value of the measurement value fluctuation of the photometric device 1 of embodiment 3. Therefore, the photometric device 1 of embodiment 3 is more preferable than the photometric device 1 of this embodiment.

[0166] <Examples 10, 11, and 12> Examples 10 to 12 will be described with reference to Figures 1 to 23. The photometric devices 1 of Examples 10 to 12 have the same configuration as the photometric devices 1 of Examples 1 to 3, but differ mainly in the following respects.

[0167] The configuration of the variable optical attenuator 4 of Examples 10 to 12 is as shown in Table 7. Therefore, the optical path length of the transparent substrate 11 is different from the optical path length of the transparent substrate 21.

[0168] [Table 7]

[0169] Example 10 The distribution of the incident angle of light incident on the variable optical attenuator 4 of this embodiment, and the half-width Δλ of the spectral responsivity spectrum of the photodetector element 9 a , and the line width Δλ of the light (measured light) emitted from the object 2 to be measured b are the distribution of the incident angle of light incident on the variable optical attenuator 4 of Example 1, and the half-width Δλ of the spectral responsivity spectrum of the photodetector element 9, respectively. a , and the line width Δλ of the light (measured light) emitted from the object 2 to be measured b (See Table 2.) Therefore, in this embodiment, similarly to the first embodiment, a consideration is made on the reduction of the fluctuation components of the interference intensity caused by the first interference, the second interference, and the third interference among a plurality of multiple reflected light beams due to the distribution of the incident angles of the light under measurement incident on the variable optical attenuator 4 (a).

[0170] <Reduction of the fluctuation component of the interference intensity caused by the first interference due to the distribution of the incident angle of the light under measurement incident on the variable optical attenuator 4> In this embodiment, when the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 5), |OPD θmax1 -OPD θmin1 | / λ is 5.101. When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 6), |OPD θmax1 -OPD θmin1 | / λ is 4.898. Therefore, this embodiment satisfies conditional expression (1). The fluctuation in the measurement value of the photometric device 1 due to the first interference (interference between light reflected twice by the first light attenuation filter and light reflected twice by the second light attenuation filter) when the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter changes from 0.0° to 0.1° is −0.03%.

[0171] <Reduction of the fluctuation component of the interference intensity caused by the second interference due to the distribution of the incident angle of the light under measurement incident on the variable optical attenuator 4> In this embodiment, when the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 7), |OPD θmax2 -OPD θmin2 | / λ is 0.000. When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 9), |OPD θmax2 -OPD θmin2 | / λ is 0.203. Therefore, this embodiment does not satisfy conditional expression (4). The variation in the measurement value of the photometric device 1 due to the second interference (interference between light reflected four times by the first light-attenuating filter and light reflected twice by the second light-attenuating filter) when the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes from 0.0° to 0.1° is −0.20%.

[0172] When the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 8), |OPD θmax3 -OPD θmin3 | / λ is 15.303. When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 10), |OPD θmax3 -OPD θmin3 | / λ is 14.897. Therefore, this embodiment satisfies conditional expression (5). The variation in the measurement value of the photometric device 1 due to the second interference (interference between light reflected twice by the first light attenuation filter and light reflected four times by the second light attenuation filter) when the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter changes from 0.0° to 0.1° is 0.00%.

[0173] <Reduction of the fluctuation component of the interference intensity caused by the third interference due to the distribution of the incident angle of the light under measurement incident on the variable optical attenuator 4> In this embodiment, when the relative tilt angle θ between the third light attenuation filter (light attenuation filter 10) and the fourth light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 13), |OPD θmax4 -OPD θmin4 | / λ is 41.694. When the relative tilt angle θ between the third light attenuation filter and the fourth light attenuation filter is 0.1° (see FIG. 16), |OPD θmax4 -OPD θmin4 | / λ is 42.274. Therefore, this embodiment satisfies conditional expression (10). When the relative tilt angle θ between the third light-attenuating filter and the fourth light-attenuating filter changes from 0.0° to 0.1°, the fluctuation in the measurement value of the photometric device 1 due to third interference (interference between light reflected twice by the third light-attenuating filter and light reflected twice by a layer (e.g., an air layer) between the third light-attenuating filter and the fourth light-attenuating filter) is 0.03%.

[0174] When the relative tilt angle θ between the third light attenuation filter (light attenuation filter 10) and the fourth light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 12), |OPD θmax5 -OPD θmin5 | is 36.594. When the relative tilt angle θ between the third light attenuation filter and the fourth light attenuation filter is 0.1° (see FIG. 10), |OPD θmax5 -OPD θmin5 | is 37.274. Therefore, this embodiment satisfies conditional expression (11). When the relative tilt angle θ between the third light-attenuating filter and the fourth light-attenuating filter changes from 0.0° to 0.1°, the fluctuation in the measurement value of the photometric device 1 due to the third interference (interference between light reflected twice by the fourth light-attenuating filter and light reflected twice by a layer (e.g., an air layer) between the third light-attenuating filter and the fourth light-attenuating filter) is 0.00%.

[0175] The measurement value fluctuation of the photometric device 1 of this embodiment is given by the sum of the measurement value fluctuation caused by the first interference, the measurement value fluctuation caused by the second interference, and the measurement value fluctuation caused by the third interference. The measurement value fluctuation of the photometric device 1 of this embodiment is -0.21%. Since the absolute value of the measurement value fluctuation of the photometric device 1 of this embodiment is within 5%, the light to be measured can be measured with high accuracy.

[0176] Example 11 The incident angle of light to the variable optical attenuator 4 of this embodiment, and the half width Δλ of the spectral responsivity spectrum of the photodetector element 9 a , and the line width Δλ of the light (measured light) emitted from the object 2 to be measured b are the incident angle of light to the variable optical attenuator 4 of Example 2, and the half width Δλ of the spectral responsivity spectrum of the photodetector element 9, respectively. a , and the line width Δλ of the light (measured light) emitted from the object 2 to be measured b (See Table 3.) Therefore, in this embodiment, as in the second embodiment, the half width Δλ of the spectral responsivity spectrum of the photodetector 9 (b) is the same as a The present invention considers the reduction of fluctuation components of interference intensity caused by first interference, second interference, and third interference among a plurality of multiple reflected lights.

[0177] <Frequency width Δλ of the spectral response spectrum of the photodetector element 9 a Reduction of the fluctuation component of the interference intensity caused by the first interference by In this embodiment, when the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 5), OPD 12 ×(1 / λ-1 / (λ+Δλ a When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 6), the OPD 12 ×(1 / λ-1 / (λ+Δλ a)) is 7.480. Therefore, this embodiment satisfies conditional expression (2). The fluctuation in the measurement value of the photometric device 1 due to the first interference (interference between light reflected twice by the first light-attenuating filter and light reflected twice by the second light-attenuating filter) when the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes from 0.0° to 0.1° is 0.00%.

[0178] <Frequency width Δλ of the spectral response spectrum of the photodetector element 9 a Reduction of the fluctuation component of the interference intensity caused by the second interference> In this embodiment, when the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 7), OPD 21 ×(1 / λ-1 / (λ+Δλ a When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 9), the OPD 21 ×(1 / λ-1 / (λ+Δλ a )) is 0.001. Therefore, this embodiment does not satisfy conditional expression (6). The variation in the measurement value of the photometric device 1 due to the second interference (interference between light reflected four times by the first light-attenuating filter and light reflected twice by the second light-attenuating filter) when the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes from 0.0° to 0.1° is −0.20%.

[0179] When the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 8), OPD 21 ×(1 / λ-1 / (λ+Δλ a When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 10), the OPD 21 ×(1 / λ-1 / (λ+Δλ a)) is 22.440. Therefore, this embodiment satisfies conditional expression (7). The variation in the measurement value of the photometric device 1 due to the second interference (interference between light reflected twice by the first light-attenuating filter and light reflected four times by the second light-attenuating filter) when the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes from 0.0° to 0.1° is 0.00%.

[0180] <Frequency width Δλ of the spectral response spectrum of the photodetector element 9 a Reduction of the fluctuation component of the interference intensity caused by the third interference by In this embodiment, when the relative tilt angle θ between the third light attenuation filter (light attenuation filter 10) and the fourth light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 11), OPD g1 ×(1 / λ-1 / (λ+Δλ a When the relative tilt angle θ between the third and fourth light attenuation filters is 0.1° (see FIG. 13), the OPD g1 ×(1 / λ-1 / (λ+Δλ a )) is 21.878. Therefore, this embodiment satisfies conditional expression (12). When the relative tilt angle θ between the third light-attenuating filter and the fourth light-attenuating filter changes from 0.0° to 0.1°, the fluctuation in the measurement value of the photometric device 1 due to the third interference (interference between light reflected twice by the third light-attenuating filter and light reflected twice by a layer (e.g., an air layer) between the third light-attenuating filter and the fourth light-attenuating filter) is 0.00%.

[0181] When the relative tilt angle θ between the third light attenuation filter (light attenuation filter 10) and the fourth light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 12), the OPD g2 ×(1 / λ-1 / (λ+Δλ a When the relative tilt angle θ between the third and fourth light attenuation filters is 0.1° (see FIG. 14), the OPD g2 ×(1 / λ-1 / (λ+Δλ a)) is 14.398. Therefore, this embodiment satisfies conditional expression (13). When the relative tilt angle θ between the third light-attenuating filter and the fourth light-attenuating filter changes from 0.0° to 0.1°, the fluctuation in the measurement value of the photometric device 1 due to the third interference (interference between light reflected twice by the fourth light-attenuating filter and light reflected twice by a layer (e.g., an air layer) between the third light-attenuating filter and the fourth light-attenuating filter) is 0.00%.

[0182] The measurement value fluctuation of the photometric device 1 of this embodiment is given by the sum of the measurement value fluctuation due to the first interference, the measurement value fluctuation due to the second interference, and the measurement value fluctuation due to the third interference. The measurement value fluctuation of the photometric device 1 of this embodiment is -0.20%. Since the absolute value of the measurement value fluctuation of the photometric device 1 of this embodiment is within 5%, the measured light can be measured with high accuracy. The absolute value of the measurement value fluctuation of the photometric device 1 of this embodiment is larger than the absolute value of the measurement value fluctuation of the photometric device 1 of embodiment 2. Therefore, the photometric device 1 of embodiment 2 is more preferable than the photometric device 1 of this embodiment.

[0183] Example 12 The incident angle of light to the variable optical attenuator 4 of this embodiment, and the half width Δλ of the spectral responsivity spectrum of the photodetector element 9 a , and the line width Δλ of the light (measured light) emitted from the object 2 to be measured b are the incident angle of light to the variable optical attenuator 4 of Example 3, and the half-width Δλ of the spectral responsivity spectrum of the photodetector element 9, respectively. a , and the line width Δλ of the light (measured light) emitted from the object 2 to be measured b (See Table 4.) Therefore, in this embodiment, as in the third embodiment, the line width Δλ of the light (measured light) emitted from the object 2 under test is b The present invention considers the reduction of fluctuation components of interference intensity caused by first interference, second interference, and third interference among a plurality of multiple reflected lights.

[0184] <Line width Δλ of the light (measured light) emitted from the object 2 b Reduction of the fluctuation component of the interference intensity caused by the first interference by In this embodiment, when the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 5), OPD 13 ×(1 / λ-1 / (λ+Δλ b When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 6), the OPD 13 ×(1 / λ-1 / (λ+Δλ b )) is 2.500. Therefore, this embodiment satisfies conditional expression (3). The fluctuation in the measurement value of the photometric device 1 due to the first interference (interference between light reflected twice by the first light-attenuating filter and light reflected twice by the second light-attenuating filter) when the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes from 0.0° to 0.1° is 0.00%.

[0185] <Line width Δλ of the light (measured light) emitted from the object 2 b Reduction of the fluctuation component of the interference intensity caused by the second interference> In this embodiment, when the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 7), OPD 21 ×(1 / λ-1 / (λ+Δλ b When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 9), the OPD 21 ×(1 / λ-1 / (λ+Δλ b )) is 0.000. Therefore, this embodiment does not satisfy conditional expression (8). The variation in the measurement value of the photometric device 1 due to the second interference (interference between light reflected four times by the first light-attenuating filter and light reflected twice by the second light-attenuating filter) when the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes from 0.0° to 0.1° is −0.20%.

[0186] When the relative tilt angle θ between the first light attenuation filter (light attenuation filter 10) and the second light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 8), OPD 22 ×(1 / λ-1 / (λ+Δλ b When the relative tilt angle θ between the first light attenuation filter and the second light attenuation filter is 0.1° (see FIG. 10), the OPD 22 ×(1 / λ-1 / (λ+Δλ b )) is 7.499. Therefore, this embodiment satisfies conditional expression (9). The variation in the measurement value of the photometric device 1 due to the second interference (interference between light reflected twice by the first light-attenuating filter and light reflected four times by the second light-attenuating filter) when the relative tilt angle θ between the first light-attenuating filter and the second light-attenuating filter changes from 0.0° to 0.1° is 0.00%.

[0187] <Line width Δλ of the light (measured light) emitted from the object 2 b Reduction of the fluctuation component of the interference intensity caused by the third interference by In this embodiment, when the relative tilt angle θ between the third light attenuation filter (light attenuation filter 10) and the fourth light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 11), OPD g1 ×(1 / λ-1 / (λ+Δλ b When the relative tilt angle θ between the third and fourth light attenuation filters is 0.1° (see FIG. 13), the OPD g1 ×(1 / λ-1 / (λ+Δλ b )) is 7.311. Therefore, this embodiment satisfies conditional expression (14). When the relative tilt angle θ between the third light-attenuating filter and the fourth light-attenuating filter changes from 0.0° to 0.1°, the fluctuation in the measurement value of the photometric device 1 due to the third interference (interference between light reflected twice by the third light-attenuating filter and light reflected twice by a layer (e.g., an air layer) between the third light-attenuating filter and the fourth light-attenuating filter) is 0.00%.

[0188] When the relative tilt angle θ between the third light attenuation filter (light attenuation filter 10) and the fourth light attenuation filter (light attenuation filter 20) is 0.0° (see FIG. 12), the OPD g1 ×(1 / λ-1 / (λ+Δλ b When the relative tilt angle θ between the third and fourth light attenuation filters is 0.1° (see FIG. 14), the OPD g1 ×(1 / λ-1 / (λ+Δλ b )) is 4.812. Therefore, this embodiment satisfies conditional expression (15). When the relative tilt angle θ between the third light-attenuating filter and the fourth light-attenuating filter changes from 0.0° to 0.1°, the fluctuation in the measurement value of the photometric device 1 due to the third interference (interference between light reflected twice by the fourth light-attenuating filter and light reflected twice by a layer (e.g., an air layer) between the third light-attenuating filter and the fourth light-attenuating filter) is 0.00%.

[0189] The measurement value fluctuation of the photometric device 1 of this embodiment is given by the sum of the measurement value fluctuation due to the first interference, the measurement value fluctuation due to the second interference, and the measurement value fluctuation due to the third interference. The measurement value fluctuation of the photometric device 1 of this embodiment is -0.20%. Since the absolute value of the measurement value fluctuation of the photometric device 1 of this embodiment is within 5%, the measured light can be measured with high accuracy. The absolute value of the measurement value fluctuation of the photometric device 1 of this embodiment is larger than the absolute value of the measurement value fluctuation of the photometric device 1 of embodiment 3. Therefore, the photometric device 1 of embodiment 3 is more preferable than the photometric device 1 of this embodiment.

[0190] (Variation) The optical path length of the transparent substrate 11 may be made different from the optical path length of the transparent substrate 21 by making the refractive index n1 of the transparent substrate 11 different from the refractive index n2 of the transparent substrate 21.

[0191] Although the photometric device 1 of the embodiment is equipped with two light attenuation filters, it may be equipped with three or more light attenuation filters. Any two of the multiple light attenuation filters equipped in the photometric device 1 may satisfy the conditional expressions shown in the embodiment.

[0192] The photometric device 1 of the embodiment can also be applied to a photometric device such as a stimulus value direct reading colorimeter. In that case, the spectral responsivity spectrum width of the light detecting element 9 is large, at approximately 50 nm or more, but if the conditions shown in the embodiment are met, it is possible to provide a photometric device 1 that has a wide dynamic range, is compact in size, and can measure light with higher accuracy.

[0193] In the embodiment, it is assumed that two light-attenuating filters are inserted or retracted, but multiple filters may be fixed on the optical axis 2p. Even when multiple filters are fixed on the optical axis 2p, the relative tilt angle between the multiple filters may change slightly due to changes in the environmental temperature around the photometric device 1 or vibrations or shocks applied to the photometric device 1. In this way, even when multiple filters are fixed on the optical axis 2p and the relative tilt angle between the multiple filters changes slightly, it is possible to measure light with higher accuracy and more stability.

[0194] The photometric device 1 of the embodiment is not limited to a light attenuation filter, and may include an interference filter having characteristics different from those of a light attenuation filter, such as a shortcut filter, a long-cut filter, or a band-pass filter. A photometric device 1 including an interference filter having characteristics different from those of a light attenuation filter is capable of optical measurement of different characteristics.

[0195] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is defined by the scope of the claims, and it is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0196] 1 photometric device, 2 object to be measured, 2p optical axis, 3 collimator lens, 4 variable optical attenuator, 5 driving device, 6 spectroscopic element, 7 condenser lens, 8 photodetector, 9 photodetector element, 10, 20 optical attenuation filter, 11, 21 transparent substrate, 12, 13, 22, 23 interference multilayer film, 14, 24 incident surface, 15, 25 exit surface.

Claims

1. a spectroscopic element; a photodetector that receives light from the spectroscopic element; a variable optical attenuator including a plurality of optical attenuation filters for attenuating light to the photodetector and a driver; the photodetector is a sensor including a plurality of photodetection elements that detect light of a plurality of different wavelengths included in the light from the spectroscopic element, the driving device can insert the plurality of light attenuation filters into and retract them from the optical axis of the light independently of one another, the plurality of light-attenuating filters are stationary during the measurement of the spectrum; the plurality of light attenuation filters are arranged at different positions in a direction along the optical axis, each of the plurality of light attenuation filters includes an interference multilayer film and a transparent substrate supporting the interference multilayer film; When a combination of any two of the plurality of light attenuation filters is a first light attenuation filter and a second light attenuation filter, the second light-attenuating filter is closer to the photodetector than the first light-attenuating filter in the direction along the optical axis; the first light attenuation filter includes a first interference multilayer film as the interference multilayer film and a first transparent substrate as the transparent substrate, the second light attenuation filter includes a second interference multilayer film as the interference multilayer film and a second transparent substrate as the transparent substrate, A photometric device, wherein a first optical path length through the first transparent substrate is different from a second optical path length through the second transparent substrate.

2. the light has a distribution of angles of incidence on the variable optical attenuator; The photometric device according to claim 1 , which satisfies the following conditional expression (1): |OPD θmax1 -OPD θmin1 | / λ>0.5 …(1) however, OPD θmax1 = (OP 1220max -OP 1022max ) and OPD θmin1 = (OP 1220min -OP 1022min ) and λ is the wavelength of the light that is within the measurable wavelength range of the photometric device, OP 1220max is the optical path length of maximum incident angle light that is reflected twice by the first optical attenuation filter and passes through the second optical attenuation filter without being reflected by the second optical attenuation filter, and the maximum incident angle light is light that has the largest incident angle to the variable optical attenuator among the light, OP 1022max is the optical path length of the maximum incident angle light that passes through the first light attenuation filter without being reflected by the first light attenuation filter and is reflected twice by the second light attenuation filter, OP 1220min is the optical path length of the minimum incident angle light that is reflected twice by the first optical attenuation filter and passes through the second optical attenuation filter without being reflected by the second optical attenuation filter, and the minimum incident angle light is the light that has the smallest incident angle to the variable optical attenuator among the light, OP 1022min is the optical path length of the minimum incident angle light that passes through the first light attenuation filter without being reflected by the first light attenuation filter and is reflected twice by the second light attenuation filter.

3. The photometric device according to claim 1 , which satisfies the following conditional expression (2): OPD 12 ×(1 / λ-1 / (λ+Δλ a ))>0.5 …(2) however, OPD 12 =|OP 1220 -OP 1022 | and λ is the wavelength of the light that is within the measurable wavelength range of the photometric device, The Δλ a is the half-width of the spectral responsivity spectrum of the photodetector element included in the photodetector, OP 1220 is the optical path length of the light that is reflected twice by the first light attenuation filter and passes through the second light attenuation filter without being reflected by the second light attenuation filter, OP 1022 is the optical path length of the light that passes through the first light attenuation filter without being reflected by the first light attenuation filter and is reflected twice by the second light attenuation filter.

4. The photometric device according to claim 1 , which satisfies the following conditional expression (3): OPD 13 ×(1 / λ-1 / (λ+Δλ b ))>0.5 …(3) however, OPD 13 =|OP 1220 -OP 1022 | and λ is the wavelength of the light that is within the measurable wavelength range of the photometric device, The Δλ b is the line width of the light emitted from the object to be measured, OP 1220 is the optical path length of the light that is reflected twice by the first light attenuation filter and passes through the second light attenuation filter without being reflected by the second light attenuation filter, OP 1022 is the optical path length of the light that passes through the first light attenuation filter without being reflected by the first light attenuation filter and is reflected twice by the second light attenuation filter.

5. The photometric device according to claim 1 , wherein a first thickness of the first transparent substrate is different from a second thickness of the second transparent substrate.

6. The photometric device according to claim 1 , wherein a first refractive index of the first transparent substrate is different from a second refractive index of the second transparent substrate.

7. the interference multilayer films of the plurality of light attenuation filters are formed of the same material, The photometric device according to claim 1 , wherein the transparent substrate of each of the plurality of light attenuation filters is made of the same material.

8. The photometric device according to claim 1 , wherein the plurality of light attenuation filters are each disposed at the same angle with respect to the optical axis.

9. The photometric device according to claim 1 , further comprising a collimator lens disposed on the incident side of the plurality of light attenuation filters.

10. The photometric device according to claim 2 , which satisfies the following conditional expressions (4) and (5): |OPD θmax2 -OPD θmin2 | / λ>0.5 …(4) |OPD θmax3 -OPD θmin3 | / λ>0.5 …(5) however, OPD θmax2 = (OP 1420max -OP 1022max ) and OPD θmin2 = (OP 1420min -OP 1022min ) and OPD θmax3 = (OP 1024max -OP 1220max ) and OPD θmin3 = (OP 1024min -OP 1220min ) and OP 1420max is the optical path length of the maximum incident angle light that is reflected four times by the first light attenuation filter and passes through the second light attenuation filter without being reflected by the second light attenuation filter, OP 1022max is the optical path length of the maximum incident angle light that passes through the first light attenuation filter without being reflected by the first light attenuation filter and is reflected twice by the second light attenuation filter, OP 1420min is the optical path length of the minimum incident angle light that is reflected four times by the first light attenuation filter and passes through the second light attenuation filter without being reflected by the second light attenuation filter, OP 1022min is the optical path length of the minimum incident angle light that passes through the first light attenuation filter without being reflected by the first light attenuation filter and is reflected twice by the second light attenuation filter, OP 1024max is the optical path length of the maximum incident angle light that passes through the first light attenuation filter without being reflected by the first light attenuation filter and is reflected four times by the second light attenuation filter, OP 1220max is the optical path length of the maximum incident angle light that is reflected twice by the first light attenuation filter and passes through the second light attenuation filter without being reflected by the second light attenuation filter, OP 1024min is the optical path length of the minimum incident angle light that passes through the first light attenuation filter without being reflected by the first light attenuation filter and is reflected four times by the second light attenuation filter, OP 1220min is the optical path length of the minimum incident angle light that is reflected twice by the first light attenuation filter and passes through the second light attenuation filter without being reflected by the second light attenuation filter.

11. The photometric device according to claim 3 , which satisfies the following conditions (6) and (7): OPD 21 ×(1 / λ-1 / (λ+Δλ a ))>0.5 …(6) OPD 22 ×(1 / λ-1 / (λ+Δλ a ))>0.5 …(7) however, OPD 21 =|OP 1420 -OP 1022 | and OPD 22 =|OP 1024 -OP 1220 | and OP 1420 is the optical path length of the light that is reflected four times by the first light-attenuating filter and passes through the second light-attenuating filter without being reflected by the second light-attenuating filter, OP 1022 is the optical path length of the light that passes through the first light attenuation filter without being reflected by the first light attenuation filter and is reflected twice by the second light attenuation filter, OP 1024 is the optical path length of the light that passes through the first light attenuation filter without being reflected by the first light attenuation filter and is reflected four times by the second light attenuation filter, OP 1220 is the optical path length of the light that is reflected twice by the first light attenuation filter and passes through the second light attenuation filter without being reflected by the second light attenuation filter.

12. The photometric device according to claim 4, which satisfies the following conditions (8) and (9): OPD 21 ×(1 / λ-1 / (λ+Δλ b ))>0.5 …(8) OPD 22 ×(1 / λ-1 / (λ+Δλ b ))>0.5 …(9) however, OPD 21 =|OP 1420 -OP 1022 | and OPD 22 =|OP 1024 -OP 1220 | and OP 1420 is the optical path length of the light that is reflected four times by the first light-attenuating filter and passes through the second light-attenuating filter without being reflected by the second light-attenuating filter, OP 1022 is the optical path length of the light that passes through the first light attenuation filter without being reflected by the first light attenuation filter and is reflected twice by the second light attenuation filter, OP 1024 is the optical path length of the light that passes through the first light attenuation filter without being reflected by the first light attenuation filter and is reflected four times by the second light attenuation filter, OP 1220 is the optical path length of the light that is reflected twice by the first light attenuation filter and passes through the second light attenuation filter without being reflected by the second light attenuation filter.

13. the plurality of light attenuation filters include a third light attenuation filter as the first light attenuation filter and a fourth light attenuation filter as the second light attenuation filter, the third light attenuation filter and the fourth light attenuation filter being any two light attenuation filters adjacent to each other among the plurality of light attenuation filters, The photometric device according to claim 2 or claim 10, which satisfies the following conditional expressions (10) and (11): |OPD θmax4 -OPD θmin4 | / λ>0.5 …(10) |OPD θmax5 -OPD θmin5 | / λ>0.5 …(11) however, OPD θmax4 = (OP 3240max -OP 30G240max ) and OPD θmin4 = (OP 3240min -OP 30G240min ) and OPD θmax5 = (OP 3042max -OP 30G240max ) and OPD θmin5 = (OP 3042min -OP 30G240min ) and OP 3240max is the optical path length of the maximum incident angle light that is reflected twice by the third light attenuation filter and passes through the fourth light attenuation filter without being reflected by the fourth light attenuation filter, OP 30G240max is the optical path length of the maximum incident angle light that passes through the third light attenuation filter and the fourth light attenuation filter without being reflected by the third light attenuation filter and the fourth light attenuation filter and is reflected twice by a layer between the third light attenuation filter and the fourth light attenuation filter, OP 3240min is the optical path length of the minimum incident angle light that is reflected twice by the third light attenuation filter and passes through the fourth light attenuation filter without being reflected by the fourth light attenuation filter, OP 30G240min is the optical path length of the minimum incident angle light that passes through the third light attenuation filter and the fourth light attenuation filter without being reflected by the third light attenuation filter and the fourth light attenuation filter and is reflected twice by the layer between the third light attenuation filter and the fourth light attenuation filter, OP 3042max is the optical path length of the maximum incident angle light that passes through the third light attenuation filter without being reflected by the third light attenuation filter and is reflected twice by the fourth light attenuation filter, OP 3042min is the optical path length of the minimum incident angle light that passes through the third light attenuation filter without being reflected by the third light attenuation filter and is reflected twice by the fourth light attenuation filter.

14. the plurality of light attenuation filters include a third light attenuation filter as the first light attenuation filter and a fourth light attenuation filter as the second light attenuation filter, the third light attenuation filter and the fourth light attenuation filter being any two light attenuation filters adjacent to each other among the plurality of light attenuation filters, The photometric device according to claim 3 or claim 11, which satisfies the following conditional expressions (12) and (13): OPD g1 ×(1 / λ-1 / (λ+Δλ a ))>0.5 …(12) OPD g2 ×(1 / λ-1 / (λ+Δλ a ))>0.5 …(13) however, OPD g1 =|OP 3240 -OP 30G240 | and OPD g2 =|OP 3042 -OP 30G240 | and OP 3240 is the optical path length of the light that is reflected twice by the third light attenuation filter and passes through the fourth light attenuation filter without being reflected by the fourth light attenuation filter, OP 30G240 is the optical path length of the light that passes through the third light attenuation filter and the fourth light attenuation filter without being reflected by the third light attenuation filter and the fourth light attenuation filter and is reflected twice by a layer between the third light attenuation filter and the fourth light attenuation filter, OP 3042 is the optical path length of the light that passes through the third light attenuation filter without being reflected by the third light attenuation filter and is reflected twice by the fourth light attenuation filter.

15. the plurality of light attenuation filters include a third light attenuation filter as the first light attenuation filter and a fourth light attenuation filter as the second light attenuation filter, the third light attenuation filter and the fourth light attenuation filter being any two light attenuation filters adjacent to each other among the plurality of light attenuation filters, The photometric device according to claim 4 or claim 12, which satisfies the following conditional expressions (14) and (15): OPD g1 ×(1 / λ-1 / (λ+Δλ b ))>0.5 …(14) OPD g2 ×(1 / λ-1 / (λ+Δλ b ))>0.5 …(15) however, OPD g1 =|OP 3240 -OP 30G240 | and OPD g2 =|OP 3042 -OP 30G240 | and OP 3240 is the optical path length of the light that is reflected twice by the third light attenuation filter and passes through the fourth light attenuation filter without being reflected by the fourth light attenuation filter, OP 30G240 is the optical path length of the light that passes through the third light attenuation filter and the fourth light attenuation filter without being reflected by the third light attenuation filter and the fourth light attenuation filter and is reflected twice by a layer between the third light attenuation filter and the fourth light attenuation filter, OP 3042 is the optical path length of the light that passes through the third light attenuation filter without being reflected by the third light attenuation filter and is reflected twice by the fourth light attenuation filter.

Images