Measurement method of reflectance, measurement method of transmittance, and vessel used for measuring transmittance

Abstract

To increase efficiency of measurement of reflectance and transmittance.SOLUTION: In a measurement method of reflectance of a multiple reflecting mirror (20), the multiple reflecting mirror (20) has a concave mirror (21) and a reflector (22), and the measurement method includes processing for measuring intensity of first light (L1o) that is reflected for a first count (n1) between the concave mirror and the reflector, is emitted from the multiple reflecting mirror, and is transmitted through a measurement object, processing for measuring intensity of second light (L2o) that is reflected for a second count (n2) between the concave mirror and the reflector, is emitted from the multiple reflecting mirror, and is transmitted through a measurement object, and processing for calculating reflectance of light by the multiple reflecting mirror on the basis of the first and second intensity and the first and second counts.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for measuring reflectance, a method for measuring transmittance, and a container for use in measuring transmittance. [Background technology]

[0002] Various techniques are used to measure the optical characteristics of an object (Patent Document 1, Non-Patent Document 1). In Patent Document 1, the method of measuring the reflectance of a concave surface includes (1) irradiating a flat plate with a reference light and measuring the amount of the reflected light (reference light measurement), and (2) irradiating a concave surface with a measurement light and measuring the amount of the reflected light (measurement light measurement). Then, the reflectance of the concave surface is calculated based on the amount of the reference light and the amount of the measurement light (see the claims of Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2006-71510 A [Non-patent literature]

[0004] [Non-Patent Document 1] T. Takemoto et al., Optik 127, 2950-2953 (2016). “Investigation of cat's eye mirror with seven reflective surfaces for in-situ spectral calibration system on divertor impurity monitor for ITER” Summary of the Invention [Problem to be solved by the invention]

[0005] However, when measuring the reflectance, it is cumbersome to measure the reflectance separately using a reference light and a measurement light, and therefore it is preferable to be able to measure the reflectance using a measurement light without using a reference light.

[0006] Now, let us consider measuring transmittance. The transmittance of an object can be measured by placing a reflecting mirror on the opposite side of the object. In other words, when light from a light source is incident on an object, this light passes through the object, is reflected by the reflecting mirror, and passes through the object again before returning. As a result, the transmittance of the object can be measured based on the ratio (I2 / I1) of the intensity I1 of the light before it enters the object to the intensity I2 of the light that has passed through the object twice and returned. In this case, the light intensity I2 changes depending on the reflectance of the reflecting mirror, so it is necessary to measure the reflectance of the reflecting mirror separately.

[0007] One aspect of the present invention aims to provide a method for measuring reflectance, a method for measuring transmittance, and a container for use in measuring transmittance, which improve the efficiency of measuring reflectance and transmittance. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, a reflectance measurement method according to one embodiment of the present invention is a method for measuring the reflectance of a multiple reflecting mirror, the multiple reflecting mirror having a concave mirror and a reflector arranged opposite the concave mirror, the measurement method including a first measurement process for measuring a first intensity of a first light that is incident on a first position of the multiple reflecting mirror, is reflected a first number of times between the concave mirror and the reflector, and exits from the multiple reflecting mirror, a second measurement process for measuring a second intensity of a second light that is incident on a second position of the multiple reflecting mirror different from the first position, is reflected a second number of times between the concave mirror and the reflector different from the first number of times, and exits from the multiple reflecting mirror, and a calculation process for calculating the reflectance of light at the multiple reflecting mirror based on the first intensity, the second intensity, the first number of times, and the second number of times. Effect of the Invention

[0009] According to one aspect of the present invention, it is possible to realize a reflectance measuring method, a transmittance measuring method, and a container for use in measuring transmittance, which improve the efficiency of measuring reflectance and transmittance. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram illustrating a measurement system according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is an exploded perspective view showing a state in which the multiple reflecting mirror is disassembled. [Diagram 3] FIG. 2 is a front view showing the division of the positions of the multiple reflecting mirrors on a concave mirror. [Figure 4] 1 is a cross-sectional view showing multiple reflections of light within a multiple reflecting mirror. [Diagram 5] FIG. 1 is a flow chart illustrating an example of a measurement method according to the first embodiment of the present invention. [Figure 6] FIG. 4 is a schematic diagram illustrating a measurement system according to a second embodiment of the present invention. [Figure 7] FIG. 11 is a schematic diagram illustrating a measurement system according to a third embodiment of the present invention. [Figure 8] FIG. 11 is a schematic diagram illustrating a measurement system according to a fourth embodiment of the present invention. [Figure 9] FIG. 11 is a schematic diagram illustrating an application example of a measurement system according to a fourth embodiment of the present invention. [Figure 10] 6 is a cross-sectional view showing multiple reflections of light within a multiple reflecting mirror according to Modification 1 of the present invention. FIG. [Figure 11] 10 is a cross-sectional view showing multiple reflections of light within a multiple reflecting mirror according to Modification 2 of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] [Embodiment 1] An embodiment of the present invention will be described in detail below. Fig. 1 is a schematic diagram showing a measurement system 10 according to the first embodiment of the present invention. Fig. 1 shows an X direction, a Y direction, and a Z direction. The Z direction is set parallel to a central axis CA described below. This is the same in Figs. 2 and 3. The measurement system 10 includes a light source LS, a beam splitter BS, a photodetector LD, and a multi-reflection mirror 20.

[0012] The light source LS emits a light flux LBi including a first light L1i and a second light L2i toward the object OB. The beam splitter BS separates the light flux LB into a transmitted light and a reflected light. This transmitted light passes through the object OB and is incident on the multi-reflection mirror 20. The object OB is an object whose transmittance is measured by the measurement system 10. The multi-reflection mirror 20 reflects the incident light flux LBi multiple times inside itself and emits it as a light flux LBo. The emitted light flux LBo passes through the object OB again, is reflected by the beam splitter BS, and is incident on the photodetector LD. The photodetector LD has multiple photodetection elements that detect light, and can measure the intensity distribution of the incident light flux LBo. An image sensor (camera) can be used as the photodetector LD.

[0013] The multiple reflecting mirror 20 has a concave mirror 21 and a reflector 22 disposed opposite the concave mirror. A first light L1i incident on a first position P1 of the concave mirror 21 is reflected a first number n1 between the concave mirror 21 and the reflector 22, and then exits from the multiple reflecting mirror 20. A second light L2i incident on a second position P2 different from the first position P1 of the concave mirror 21 is reflected a second number n2 different from the first number n1 between the concave mirror 21 and the reflector 22, and then exits from the multiple reflecting mirror 20. That is, in the multiple reflecting mirror 20, the number of internal reflections n1 and n2 differ depending on the positions P1 and P2 at which the light is incident.

[0014] 2 is an exploded perspective view showing a disassembled state of the multiple reflecting mirror 20. In this example, the multiple reflecting mirror 20 is formed by disposing a base 25, a cylindrical body 26, and a light entrance portion 27 one above the other and fixing them with screws 28.

[0015] Base 25 is a base for multiple reflecting mirror 20. Concave mirror 21 is formed on the surface of base 25 facing the positive direction of the Z axis. Concave mirror 21 may have, for example, a parabolic shape having a central axis CA. In this case, concave mirror 21 focuses light incident along central axis CA onto focal point F.

[0016] The cylinder 26 has an internal space that allows light to pass in the Z-axis direction and blocks external light from other directions.

[0017] The light incident section 27 has a reflector 22 and an opening. The reflector 22 causes light in the negative Z-axis direction that is incident from the opening of the light incident section 27 to be multiple-reflected between the reflector 22 and the concave mirror 21, and causes the light to exit from the opening.

[0018] The reflector 22 may have a first reflecting member 23 arranged on the central axis CA of the concave mirror 21, and one or more second reflecting members 24 arranged to radiate from the central axis CA. In this example, the first reflecting member 23 has a first reflecting surface located at a focal point F on the central axis CA of the concave mirror 21 on the negative side of the Z axis. This first reflecting surface can be, for example, a plane perpendicular to the central axis CA. In this example, the one or more second reflecting members 24 have three rod-shaped second reflecting members 24a to 24c. However, the number of second reflecting members 24 is not limited to three, and may be two or less, or four or more. The second reflecting members 24a to 24c have, for example, a planar second reflecting surface perpendicular to the central axis CA on the negative side of the Z axis. The second reflecting members 24a to 24c connect the outer periphery of the light entrance portion 27 and the first reflecting member 23, and also function as holding members (arms) that hold the first reflecting member 23 on the central axis CA of the concave mirror 21. The spaces between the second reflecting members 24a to 24c are the openings of the light entrance portion 27.

[0019] In relation to the second reflecting members 24a-24c, the surface of the concave mirror 21 can be divided as follows. The intersection point of the concave mirror 21 and the central axis CA is defined as the center C of the concave mirror 21. Lines Ba-Bc parallel to the central axis CA are drawn from the bases of the rod-shaped second reflecting members 24a-24c, forming intersection points Da-Dc between the concave mirror 21 and the concave mirror 21. Lines Aa1-Ac1 connect the intersection points Da-Dc and the center C. The lines Aa1-Ac1 on the concave mirror 21 correspond to the second reflecting members 24a-24c, respectively. That is, the surface of the concave mirror 21 on the lines Aa1-Ac1 faces the second reflecting members 24a-24c. These lines Aa1-Ac1 are extended to the opposite side of the central axis CA to define the lines Aa-Ac. The lines Aa-Ac on the concave mirror 21 do not correspond to the second reflecting members 24a-24c. In other words, the surface of concave mirror 21 on line Aa to Ac does not face second reflecting members 24a to 24c.

[0020] 3 is a front view showing the division of positions of multiple reflecting mirror 20 on concave mirror 21. Here, the region along lines Aa-Ac that is the width of second reflecting members 24a-24c is defined as second position P2, and the other region on the surface of concave mirror 21 that does not face second reflecting members 24a-24c is defined as first position P1. By setting first position P1 and second position P2 in this way, it is possible to vary the number of multiple reflections of incident light.

[0021] 4 is a cross-sectional view showing multiple reflections of light within multiple reflecting mirror 20. In cross-sectional view L1, multiple reflecting mirror 20 is cut along a plane including position P1 along central axis CA. In cross-sectional view L2, multiple reflecting mirror 20 is cut along a plane including position P2 along central axis CA. That is, in cross-sectional view L2, multiple reflecting mirror 20 is cut along central axis CA and lines Aa and Aa1.

[0022] The concave mirror 21 has a paraboloid having a focal point F on the central axis CA, and the first reflecting member 23 has a first reflecting surface disposed at the focal point F. The one or more second reflecting members 24a-24c have second reflecting surfaces directed toward a third position P21 on the concave mirror 21 that is symmetrical to the second position P2 with respect to the central axis CA.

[0023] Here, the light beam LBi is assumed to be parallel light along the central axis CA. As shown in the cross-sectional view L1, the first light L1i incident on the first position P1 of the multiple reflecting mirror 20 is reflected by the concave mirror 21, incident on the first reflecting member 23, reflected by the first reflecting member 23, incident on the concave mirror 21, reflected by the concave mirror 21, and emitted from the multiple reflecting mirror 20. More specifically, the light L1i incident parallel to the central axis CA is reflected by the concave mirror 21 at the position P1, collected at the focal point F, reflected by the first reflecting member 23 at the focal point F, reaches the third position P11 symmetrical to the first position P1 with respect to the center C, reflected by the concave mirror 21 at the third position P11, and emitted from the multiple reflecting mirror 20. In this way, the light L1i incident on the position P1 is reflected three times within the multiple reflecting mirror 20 (n1=3) and is emitted from within the multiple reflecting mirror 20.

[0024] As shown in cross-sectional view L2, the second light L2i incident on the second position P2 of the multiple reflecting mirror 20 is reflected by the concave mirror 21, enters the first reflecting member 23, is reflected by the first reflecting member 23, enters the concave mirror 21, is reflected by the concave mirror 21, enters the second reflecting member 24a, is reflected by the second reflecting member 24a, enters the concave mirror 21, is reflected by the concave mirror 21, enters the first reflecting member 23, is reflected by the first reflecting member, enters the concave mirror 21, is reflected by the concave mirror 21, and is emitted from the multiple reflecting mirror 20. More specifically, the light L2i incident parallel to the central axis CA is reflected by the concave mirror 21 at position P2, collected at the focal point F, reflected by the first reflecting member 23 at the focal point F, reaches a position P21 symmetrical to position P2 with respect to the center C, is reflected by the concave mirror 21 at position P21, and enters the second reflecting member 24a. The light L2i is then reflected by the second reflecting member 24a, travels along the reverse path, reaches position P2, is reflected by the concave mirror 21 at position P2, and is emitted from the multiple reflecting mirror 20. In this way, the light L2i incident at position P2 is reflected seven times (n2=7) within the multiple reflecting mirror 20, and is emitted from the multiple reflecting mirror 20.

[0025] Fig. 5 is a flow diagram showing an example of a measurement method according to the first embodiment of the present invention. As shown in Fig. 5, the measurement method S10 according to the first embodiment of the present invention includes a measurement process S11 and a calculation process S12. Hereinafter, the measurement process S11 and the calculation process S12 will be described with reference to Fig. 1 again.

[0026] (1) Measurement process S11 The light source LS causes a light flux LBi including the first and second lights L1i and L2i to be incident on the multi-reflection mirror 20 (incident process). The light flux LBi emitted from the light source LS is split into a transmitted light and a reflected light by the beam splitter BS. This transmitted light passes through the object to be measured OB and is incident on the multi-reflection mirror 20.

[0027] The first light L1i and the second light L2i are reflected within the multi-reflecting mirror 20 a first number n1 and a second number n2 (here, 3 times and 7 times), respectively, and exit from the multi-reflecting mirror 20 as the first light L1o and the second light L2o.

[0028] The first light L1o and the second light L2o again pass through the measurement object OB and enter the beam splitter BS. The beam splitter BS separates the incident light into transmitted light and reflected light. The reflected light of the first light L1o and the second light L2o enters the photodetector LD. As a result, the intensities of the first and second lights L1o and L2o contained in the light beam LBo are measured. That is, the following first measurement process and second measurement process are executed.

[0029] In the first measurement process, a first intensity B1 is measured of a first light L1o that is incident on a first position P1 of the multiple reflecting mirror 20, is reflected a first number n1 between the concave mirror 21 and the reflector 22, and is emitted from the multiple reflecting mirror 20. In addition, in the second measurement process, a second intensity B2 is measured of a second light that is incident on a second position P2 different from the first position P1 of the multiple reflecting mirror 20, is reflected a second number n2 different from the first number n1 between the concave mirror 21 and the reflector 22, and is emitted from the multiple reflecting mirror 20.

[0030] That is, taking into consideration the measurement object OB, in the first measurement process, a first intensity B1 of a first light L1o is measured, which passes through the measurement object OB, enters the first position P1 of the multiple reflecting mirror 20, is reflected a first number n1 between the concave mirror 21 and the reflector 22, exits from the multiple reflecting mirror 20, and passes through the measurement object OB. In addition, in the second measurement process, a second intensity B2 of a second light is measured, which passes through the measurement object OB, enters the second position P2 different from the first position P1 of the multiple reflecting mirror 20, is reflected a second number n2 different from the first number n1 between the concave mirror 21 and the reflector 22, exits from the multiple reflecting mirror 20, and passes through the measurement object OB.

[0031] (2) Calculation process S12 The reflectance Rm of the multiple reflecting mirror 20 can be calculated by applying the first intensity B1, the second intensity B2, the number of reflections n1, and the number of reflections n2 to equation (3) described later. Furthermore, the transmittance T of the object to be measured OB can be calculated by applying the calculated reflectance Rm to equation (3) described later.

[0032] The following equations (1) and (2) hold. Here, the intensity of the light beam LBi is uniform, and therefore the intensities Bi of the first light L1i and the second light L2i are equal. Also, the reflectances Rm of the concave mirror 21, the first reflecting member 23, and the second reflecting member 24 are equal. The distances r between the center C and the positions P1 and P2 are equal.

[0033] B1(r,θ)=Rm n1 (r,θ * )·To 2 Tbs Rbs Bi … Equation (1) B2(r,θ * )=Rm n2 (r,θ * )·To 2 Tbs Rbs Bi … Equation (2) B1: Intensity (brightness) of the first light L1o incident on the photodetector LD B2: Intensity (brightness) of the second light L2o incident on the photodetector LD Bi: Intensity (brightness) of the first light L1i and the second light L2i emitted from the light source LS Rm: reflectance of the concave mirror 21 and the reflector 22 (the first reflecting member 23 and the second reflecting member 24) of the multiple reflecting mirror 20 To: Transmittance of the object to be measured Tbs: transmittance of beam splitter BS Rbs: reflectance of beam splitter BS (r, θ): Polar coordinates of position P1 based on center C of concave mirror 21 (r,θ * ): Polar coordinates of position P2 based on the center C of the concave mirror 21

[0034] Taking the ratio of equations (1) and (2), the following equation is established: That is, the reflectance Rm of the multiple reflecting mirror 20 can be calculated from the intensities B1 and B2 of the light L1o and L2o. Rm = [B2(r,θ * ) / B1(r,θ)] 1 / (n2-n1) ...Formula (3)

[0035] "B2(r,θ * )=B2(r,θ)", then the following equation (4) can be derived from equation (1). To = [B1(r,θ) / (Rm n1 Bi Tbs Rbs)] 1 / 2 ...Formula (4)

[0036] As described above, the reflectance Rm of light at the multiple reflecting mirror 20 can be calculated based on the first intensity B1, the second intensity B2, the first number of times n1, and the second number of times n2. Also, the transmittance To of light for the measurement object OB can be calculated based on the first intensity B1, the second intensity B2, the first number of times n1, and the second number of times n2. In this embodiment, by using multiple reflections with different numbers of times, it is possible to improve the efficiency of measuring the reflectance and transmittance. That is, the reflectance Rm of the multiple reflecting mirror 20 can be obtained without using a reference light. Also, the transmittance T of the measurement object OB can be obtained without separately measuring the reflectance Rm of the multiple reflecting mirror 20.

[0037] [Embodiment 2] 6 is a schematic diagram showing a measurement system 30 according to a second embodiment of the present invention. Here, a multiple reflecting mirror 20 is installed inside a container VC, making it possible to measure the transmittance of the atmosphere AT inside the container VC. When the inside of the container VC is, for example, a reduced pressure environment or a radiation environment, the transmittance To of the window material WD and the atmospheric gas AT inside the container VC can be measured without a human being entering the container VC.

[0038] FIG. 6(a) shows a state in which the gas valve VL is closed and the container VC is evacuated (a vacuum pump or other vacuum mechanism is not shown). At this time, there is no atmospheric gas AT in the container VC. FIG. 6(b) shows a state in which the gas valve VL is opened and the atmospheric gas AT flows into the container VC. At this time, the inflow of the atmospheric gas AT from the valve VL and the outflow of the atmospheric gas AT due to the evacuation are balanced in the container VC. As a result, the pressure of the atmospheric gas AT in the container VC becomes stable over time.

[0039] As shown below, the transmittance To1 of the window material WD is measured when no atmospheric gas AT flows into the container VC (FIG. 6(a)), and the transmittance To1 is used to measure the transmittance To2 (gas concentration) of the atmospheric gas AT when the atmospheric gas AT flows into the container VC (FIG. 6(b)).

[0040] That is, as shown in FIG. 6(a), the light beam LBi from the light source LS passes through the beam splitter BS, passes through the window material WD, and enters the container VC. The light beam LBi enters the multi-reflection mirror 20 in the container VC, is multiply reflected therein, passes through the window material WD, is reflected by the beam splitter BS, and enters the photodetector LD as the light beam LBo. The photodetector LD can measure the intensity distribution IM of the incident light beam LBo. That is, as described in the first embodiment, the intensities B1 and B2 of the first light L1 and the second light L2 contained in the light beam LBi can be measured to calculate the transmittance To1 of the window material WD. At this time, as described above, it is not necessary to separately measure the reflectance Rm of the multi-reflection mirror 20.

[0041] On the other hand, as shown in FIG. 6(b), even when the atmospheric gas AT flows into the container VC, the path of the light flux LBi is the same, and the intensities B1 and B2 of the first light L1 and second light L2 contained in the light flux LBi are measured to calculate the transmittance Tx. The transmittance Tx calculated at this time is the sum of the transmittance To1 of the window material WD and the transmittance To2 of the atmospheric gas AT (Tx=To1*To2). In other words, the transmittance To2 (=Tx / To1) of the atmospheric gas AT can be calculated.

[0042] As described above, in this embodiment, by using multiple reflections with different numbers of times, it is possible to obtain the transmittance To1 of the window material WD and further the transmittance To2 of the atmospheric gas AT without separately measuring the reflectance Rm of the multiple reflecting mirror 20.

[0043] [Embodiment 3] 7 is a schematic diagram showing a measurement system 40 according to a third embodiment of the present invention. Here, a container VC has a window material WD that transmits light from inside the container VC. By disposing a multi-reflection mirror 20 inside the container VC so as to face the window material WD (disposition process), it becomes possible to measure the transmittance T of the window material WD.

[0044] Here, the container VC includes a moving mechanism DR that moves the multiple reflecting mirror 20 disposed in the main body (container main body) of the container VC to set the window material WD to a first state and a second state. The multiple reflecting mirror 20 is attached to the viewport shutter SH and can be moved by the moving mechanism DR. The first state and the second state are shown on the left and right of the figure as an open state OP-ST and a closed state CL-ST of the window material WD (viewport shutter SH). In the first state (open state OP-ST), the multiple reflecting mirror 20 does not face the window material WD, and as a result, light from inside the container VC passes through the window material WD and is emitted outside the container. In the second state (closed state CL-ST), the multiple reflecting mirror 20 faces the window material WD, and as a result, light from outside the container VC passes through the window material WD, is reflected by the multiple reflecting mirror 20, and is emitted outside the container VC. Here, in a first state (open state OP-ST), a spectrometer SD is shown which collects light emitted from a window material WD with a collector CL and performs spectroscopic measurement via an optical fiber OF.

[0045] After creating a vacuum inside the container VC, gas G is introduced and a voltage is applied between a pair of electrodes E to cause a discharge (generation of plasma PL) to process, for example, a semiconductor wafer WF. At this time, by setting the moving mechanism DR to a first state (open state OP-ST), the light emitted by this discharge can be measured by a spectrometer SD through the window material WD. By setting the moving mechanism DR to a second state (closed state CL-ST), the transmittance of the window material WD can be measured using the multi-reflection mirror 20.

[0046] That is, the light emitted from the plasma PL generated in the container VC can be measured through the window material WD to determine the state of the plasma PL. At this time, since the transmittance of the window material WD changes over time due to contamination (e.g., formation of a coating), it is preferable to measure the transmittance of the window material WD. In this embodiment, the change in the transmittance of the window material WD caused by contamination on the inside of the window material WD can be measured without returning the inside of the container VC to the atmosphere, and the cleanliness of the inside of the container VC is maintained.

[0047] [Embodiment 4] 8 is a schematic diagram showing a measurement system 50 according to a fourth embodiment of the present invention. Here, a plurality of multiple reflecting mirrors 20 are installed at a position PL at a distance L from a light source LS (installation process). That is, the measurement method in this case includes an installation process in which a plurality of multiple reflecting mirrors 20 having central axes CA in different directions are installed at a predetermined position P, an incidence process in which a light beam emitted from the light source LS is made incident on the plurality of multiple reflecting mirrors 20, and a measurement process in which the intensities of the first and second light beams emitted from at least any of the plurality of multiple reflecting mirrors 20 are measured.

[0048] The predetermined point P is not limited to being on the earth, and may be an extraterrestrial celestial body such as a satellite, a planet, a comet, etc. The transmittance can be measured by measuring, for example, a gaseous substance present between the light source LS and the predetermined point P0 as the measurement object OB.

[0049] 9 is a schematic diagram showing application examples SIT1 and SIT2 of the measurement system according to the fourth embodiment of the present invention. In application example SIT1, the gas concentration in the Earth's atmosphere can be analyzed, and in application example SIT2, the gas concentration of the planet PL or a satellite can be analyzed.

[0050] In application example SIT1, a light source LS, a beam splitter BS, a Cassegrain telescope TS, and a photodetector LD are installed on the ground, and a multiple reflector 20 is installed on an artificial satellite AS orbiting the Earth. The artificial satellite AS has a base BA on the surface facing the ground, on which multiple reflectors 20 are attached.

[0051] A light beam LB emitted from a light source LS and reflected by a beam splitter BS is guided to a Cassegrain telescope TS and emitted toward an artificial satellite AS through the atmosphere AM. This light beam LB is reflected by a multiple reflecting mirror 20 installed on the artificial satellite AS, and passes through the atmosphere AM, the Cassegrain telescope TS, and the beam splitter BS to enter a photodetector LD, where the intensities B1 and B2 of a first light L1o and a second light L2o contained in the light beam LB are measured.

[0052] As a result, the light transmittance To of the atmosphere AM can be obtained. Furthermore, by performing this measurement while changing the wavelength of the light contained in the light beam LB, the light transmission spectrum of the atmosphere AM can be obtained. The transmittance or transmission spectrum obtained in this way can be used to measure the concentration of gas components in the atmosphere AM.

[0053] In application example SIT2, a light beam LB is emitted, reflected, etc. between (1) an artificial satellite AS1 and a planet PL or a satellite (hereinafter collectively referred to as "planet PL"), and (2) between an artificial satellite AS2 away from the planet PL and an artificial satellite AS3 close to the planet PL. The artificial satellites AS1 and AS2 have a light source LS, a beam splitter BS, and a photodetector LD. A plurality of multi-reflecting mirrors 20 are installed on the planet PL and on the artificial satellite AS3. Between the artificial satellite AS1 and the planet PL, the light beam LB passes through atmospheric layers AM1 and AM2, and between the artificial satellites AS2 and AS3, the light beam LB passes through atmospheric layer AM2.

[0054] As a result, the transmittance of the entire atmospheric layers AM1 and AM2 is measured between the satellite AS1 and planet PL, and the transmittance of the atmospheric layer AM2 is measured between the satellites AS2 and AS3. In this way, by using the satellites AS2 and AS3, it is possible to measure the transmittance of a specific atmospheric layer, and further to analyze gas components and dust.

[0055] As described above, by installing the multiple reflector 20 on the artificial satellites AS, AS3, and planet PL, it is possible to obtain the light transmittance of the atmospheres AM, AM1, and AM2 without separately measuring the reflectance of the multiple reflector 20 itself. The reflectance of the multiple reflector 20 is not constant, but varies due to dust, for example. However, it is generally not easy to measure the reflectance of the multiple reflector 20 installed on the artificial satellite AS and planet PL. In this embodiment, this difficult measurement can be made easy.

[0056] [Modifications] In the above, it has been assumed that the light incident on the multiple reflecting mirror 20 is parallel light, and the concave mirror 21 is made to have a parabolic shape, thereby converging the light to the focal point F. However, let us consider using convergent light instead of parallel light.

[0057] (1) Variation 1 10 is a cross-sectional view showing multiple reflections of light within multiple reflecting mirror 20 according to Modification 1 of the present invention. In cross-sectional view L1a, multiple reflecting mirror 20 is cut along a plane including position P1 along central axis CA. In cross-sectional view L2a, multiple reflecting mirror 20 is cut along a plane including position P2 along central axis CA. Here, it is assumed that the light incident on multiple reflecting mirror 20 is convergent light.

[0058] The concave mirror 21 has an ellipsoidal surface, and the ellipsoidal surface has a first focal point F1 and a second focal point F2 on the central axis CA that is farther from the concave mirror 21 than the first focal point F1. The first reflecting member 23 has a first reflecting surface disposed at the first focal point F1. The one or more second reflecting members 24a-24c have second reflecting surfaces that are directed toward a third position P21 symmetrical to the second position P2 with respect to the central axis CA and are inclined at an angle θ with respect to the central axis CA.

[0059] That is, the concave mirror 21 is an ellipsoid and has two focal points F1 and F2. The convergent light is focused at the focal point F1. The convergent light passing through the focal point F1 is reflected by the ellipsoidal concave mirror 21 at the position P1, reaches the focal point F2, is reflected by the first reflecting member 23 at the focal point F2, reaches the position P11 which is point-symmetrical to the position P1 with respect to the center C, is reflected by the ellipsoidal concave mirror 21, and reaches the focal point F1 again. Meanwhile, the reflecting surface of the second reflecting member 24 is tilted by an angle θ so that the light reflected at the position P11 is perpendicularly incident on the reflecting surface of the second reflecting member 24. In this way, the light reflected by the second reflecting member 24 follows the original path and is focused at the focal point F1.

[0060] As described above, by making the concave mirror 21 an ellipsoid, focusing the convergent light on the focus F1 of the ellipsoid, and tilting the second reflecting member 24, the convergent light incident on the position P1 through the focus F1 is reflected three times in the multiple reflecting mirror 20, and the convergent light incident on the position P2 is reflected seven times in the multiple reflecting mirror 20. In this way, by using the concave mirror 21 with an ellipsoidal surface for the convergent light, it is possible to improve the efficiency of measuring the reflectance and transmittance. That is, even with the convergent light, the reflectance Rm of the multiple reflecting mirror 20 can be obtained without using a reference light. Also, the transmittance T of the measurement object OB can be obtained without separately measuring the reflectance Rm of the multiple reflecting mirror 20.

[0061] (2) Variation 2 11 is a cross-sectional view showing multiple reflections of light within multiple reflecting mirror 20 according to Modification 2 of the present invention. In cross-sectional view L1b, multiple reflecting mirror 20 is cut along a plane including position P1 along central axis CA. In cross-sectional view L2b, multiple reflecting mirror 20 is cut along a plane including position P2 along central axis CA. Here, it is assumed that light incident on multiple reflecting mirror 20 is convergent light.

[0062] The concave mirror 21 has a paraboloid, and the paraboloid has a focal point F on the central axis CA. The first reflecting member 23 has a first reflecting surface that is disposed farther from the center C of the paraboloid than the focal point F (at point F1b). The one or more second reflecting members 24a-24c are disposed to face a third position P21 that is symmetrical to the second position P2 with respect to the central axis CA. The first reflecting surface of the first reflecting member 23 has a convex shape, and the one or more second reflecting members 24a-24c have a second reflecting surface that is inclined with respect to the central axis CA.

[0063] That is, by making the concave mirror 21 a paraboloid and giving the reflecting surface of the first reflecting member 23 a convex curvature, the convergent light incident on the multiple reflecting mirror 20 can be converged to the convergence point F2b and to the point F1b. In this case as well, if the second reflecting surface of the second reflecting member 24 is tilted so that the light reflected by the first reflecting surface of the first reflecting member 23 and reflected by the concave mirror 21 is perpendicularly incident, the light reflected by the second reflecting member 24 will retrace its original path and be converged again to the convergence point F2b.

[0064] As described above, by giving the reflecting surface of the first reflecting member 23 a convex curvature and tilting the second reflecting member 24, the convergent light incident on position P1 through the convergence point FP is reflected three times within the multiple reflecting mirror 20, and the convergent light incident on position P2 is reflected seven times within the multiple reflecting mirror 20. In this way, it is possible to improve the efficiency of measuring the reflectance and transmittance even with convergent light. That is, the reflectance Rm of the multiple reflecting mirror 20 can be obtained without using a reference light. Also, the transmittance T of the measurement object OB can be obtained without separately measuring the reflectance Rm of the multiple reflecting mirror 20.

[0065] [summary] A method for measuring transmittance according to a first aspect of the present invention is a method for measuring the reflectance of a multiple reflecting mirror, the multiple reflecting mirror having a concave mirror and a reflector arranged opposite to the concave mirror, the method including a first measurement process for measuring a first intensity of a first light that is incident on a first position of the multiple reflecting mirror, reflected a first number of times between the concave mirror and the reflector, and emitted from the multiple reflecting mirror, a second measurement process for measuring a second intensity of a second light that is incident on a second position different from the first position of the multiple reflecting mirror, reflected a second number of times different from the first number of times between the concave mirror and the reflector, and emitted from the multiple reflecting mirror, and a calculation process for calculating the reflectance of the multiple reflecting mirror based on the first intensity, the second intensity, the first number of times, and the second number of times. This makes it possible to improve the efficiency of the measurement of the reflectance by using multiple reflections with different numbers. That is, the reflectance of the multiple reflecting mirror can be obtained without performing a measurement using a reference light.

[0066] A transmittance measurement method according to a second aspect of the present invention is a reflectance measurement method for measuring the transmittance of a measurement object using a multiple reflecting mirror, the multiple reflecting mirror having a concave mirror and a reflector arranged opposite the concave mirror, and the measurement method includes a first measurement process for measuring a first intensity of a first light that has passed through the measurement object, entered a first position of the multiple reflecting mirror, been reflected a first number of times between the concave mirror and the reflector, exited from the multiple reflecting mirror, and passed through the measurement object, a second measurement process for measuring a second intensity of a second light that has passed through the measurement object, entered a second position of the multiple reflecting mirror different from the first position, been reflected a second number of times between the concave mirror and the reflector different from the first number of times, exited from the multiple reflecting mirror, and passed through the measurement object, and a calculation process for calculating the transmittance of light for the measurement object based on the first intensity, the second intensity, the first number of times, and the second number of times. In this way, by using multiple reflections with different numbers of times, it is possible to improve the efficiency of the transmittance measurement, i.e., it is possible to obtain the transmittance of the measurement target without separately measuring the reflectance of the multiple reflecting mirror.

[0067] A measurement method according to a third aspect of the present invention is the same as that of the first or second aspect, in which the concave mirror has a central axis, and the reflector has a first reflecting member arranged on the central axis and one or more second reflecting members arranged to radiate from the central axis. With this, by using the first reflecting member arranged on the central axis and the one or more second reflecting members arranged to radiate from the central axis, multiple reflections of different numbers of times are facilitated between the concave mirror and the reflector.

[0068] A fourth aspect of the present invention relates to a measurement method according to the third aspect, wherein the concave mirror has a parabolic surface, the parabolic surface has a focal point on the central axis, the first reflecting member has a first reflecting surface disposed at the focal point, and the one or more second reflecting members have second reflecting surfaces oriented toward a third position on the concave mirror that is symmetrical to the second position with respect to the central axis. Thus, the use of a parabolic surface makes it easy to multiple-reflect parallel light different times.

[0069] A fifth aspect of the present invention relates to a measurement method according to the third aspect, wherein the concave mirror has a parabolic surface, the parabolic surface has a focal point on the central axis, the first reflecting member has a first reflecting surface disposed farther from the center of the parabolic surface than the focal point, the first reflecting surface of the first reflecting member has a convex shape, and the one or more second reflecting members have second reflecting surfaces inclined with respect to the central axis. Thus, the first reflecting member has a convex reflecting surface, which facilitates multiple reflections of the convergent light at different times.

[0070] A sixth aspect of the present invention relates to a measurement method according to the third aspect, wherein the concave mirror has an ellipsoidal surface, the ellipsoidal surface has a first focal point on the central axis and a second focal point farther from the concave mirror than the first focal point, the first reflecting member has a first reflecting surface disposed at the first focal point, and the one or more second reflecting members have second reflecting surfaces oriented to a third position symmetrical to the second position with respect to the central axis and inclined with respect to the central axis. Thus, the use of an ellipsoidal surface makes it easy to perform multiple reflections of the convergent light at different times.

[0071] A measurement method according to a seventh aspect of the present invention is any one of aspects three to six, wherein the first light incident on the first position of the multiple reflecting mirror is reflected by the concave mirror, incident on the first reflecting member, reflected by the first reflecting member, incident on the concave mirror, reflected by the concave mirror, and exits from the multiple reflecting mirror, and the second light incident on the second position of the multiple reflecting mirror is reflected by the concave mirror, incident on the first reflecting member, reflected by the first reflecting member, incident on the concave mirror, reflected by the concave mirror, incident on the second reflecting member, reflected by the second reflecting member, incident on the concave mirror, reflected by the concave mirror, incident on the first reflecting member, reflected by the first reflecting member, incident on the concave mirror, reflected by the concave mirror, and exits from the multiple reflecting mirror. This makes it possible for a first light beam incident on a first position to be reflected three times within the multi-reflection mirror, and a second light beam incident on a second position to be reflected seven times within the multi-reflection mirror.

[0072] A measurement method according to an eighth aspect of the present invention is any one of the first to seventh aspects, and includes an incident process of making a light flux including the first light and the second light incident on the multiple reflecting mirror, thereby generating the first light and the second light that are multiple-reflected a different number of times using the light flux.

[0073] A measurement method according to a ninth aspect of the present invention is the same as in the eighth aspect, and includes an installation process of installing a plurality of the multiple reflecting mirrors having different axial directions at predetermined locations, the incidence process of causing the light beam emitted from a light source to be incident on at least one of the plurality of multiple reflecting mirrors, and the measurement process of measuring a first intensity of the first light and an intensity of the second light emitted from at least one of the plurality of multiple reflecting mirrors. This makes it possible to measure the transmittance of a measurement object placed between the predetermined location and a distant location.

[0074] A tenth aspect of the present invention relates to a measurement method according to the ninth aspect, wherein the measurement target is a gaseous substance present between the light source and the predetermined location. This makes it possible to measure the transmittance of a gaseous substance located between the light source and the distant predetermined location.

[0075] A method for measuring transmittance according to an eleventh aspect of the present invention is any one of the methods for measuring transmittance according to the second to seventh aspects, in which the measurement object is a window material provided in a container and transmits light from inside the container, and the method for measuring transmittance includes a step of arranging the multi-reflection mirror inside the container so as to face the window material. By arranging the multi-reflection mirror inside the container, the transmittance of the window material of the container can be measured.

[0076] A container for use in the transmittance measuring method according to aspect 12 of the present invention is a container for use in the measuring method according to aspect 11, comprising a container body, the window material provided in the container body and allowing light from inside the container body to pass through, the multiple reflecting mirror disposed in the container body, and a moving mechanism for moving the multiple reflecting mirror to set the window material to a first state and a second state, in which in the first state, the multiple reflecting mirror does not face the window material, and light from inside the container body passes through the window material and is emitted outside the container body, and in the second state, the multiple reflecting mirror faces the window material, and light from outside the container body passes through the window material, is reflected by the multiple reflecting mirror, and is emitted outside the container body. This allows the transmittance of the window material to be measured while the inside of the container is held by moving the multiple reflecting mirror with the moving mechanism.

[0077] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0078] 10, 30, 40, 50 measurement systems 20 Multiple reflector 21 concave mirror 23 First reflecting member 24a to 24c Second reflecting member 25 Foundation 26 Cylinder 27 Light incidence part LBi, LBo luminous flux S11 Measurement processing S12 Calculation process

Claims

1. A method for measuring the reflectance of a multiple reflector mirror, comprising the steps of: The multiple reflecting mirror is A concave mirror; A reflector disposed opposite the concave mirror; having The measurement method includes: a first measurement process for measuring a first intensity of a first light that is incident on a first position of the multiple reflecting mirror, is reflected a first number of times between the concave mirror and the reflector, and is then emitted from the multiple reflecting mirror; a second measurement process for measuring a second intensity of a second light beam that is incident on a second position of the multiple reflecting mirror that is different from the first position, is reflected between the concave mirror and the reflector a second number of times that is different from the first number of times, and is emitted from the multiple reflecting mirror; a calculation process of calculating a reflectance of light at the multiple reflecting mirror based on the first intensity, the second intensity, the first number of times, and the second number of times; A measurement method including:

2. A method for measuring the transmittance of a measurement object using a multiple reflecting mirror, comprising the steps of: The multiple reflecting mirror is A concave mirror; A reflector disposed opposite the concave mirror; having The measurement method includes: a first measurement process for measuring a first intensity of a first light that has passed through the measurement object, is incident on a first position of the multiple reflecting mirror, is reflected a first number of times between the concave mirror and the reflector, is emitted from the multiple reflecting mirror, and is passed through the measurement object; a second measurement process for measuring a second intensity of a second light that has passed through the object to be measured, is incident on a second position of the multiple reflecting mirror different from the first position, is reflected between the concave mirror and the reflector a second number of times different from the first number of times, is emitted from the multiple reflecting mirror, and is transmitted through the object to be measured; a calculation process of calculating a light transmittance for the measurement object based on the first intensity, the second intensity, the first number of times, and the second number of times; A measurement method including:

3. the concave mirror has a central axis; The reflector is A first reflecting member disposed on the central axis; one or more second reflecting members arranged to radiate from the central axis; The method according to claim 1 or 2, comprising:

4. the concave mirror has a parabolic surface; The paraboloid has a focus on the central axis, the first reflecting member has a first reflecting surface disposed at the focal point; The measurement method according to claim 3 , wherein the one or more second reflecting members have a second reflecting surface oriented toward a third position on the concave mirror symmetrical to the second position with respect to the central axis.

5. the concave mirror has a parabolic surface; The paraboloid has a focus on the central axis, the first reflecting member has a first reflecting surface disposed farther from the center of the paraboloid than the focal point; the first reflecting surface of the first reflecting member has a convex shape, The measurement method according to claim 3 , wherein the one or more second reflecting members have second reflecting surfaces inclined with respect to the central axis.

6. the concave mirror has an ellipsoidal surface; the ellipsoid has a first focus on the central axis and a second focus located farther away from the concave mirror than the first focus, the first reflecting member has a first reflecting surface disposed at the first focal point; The measurement method according to claim 3 , wherein the one or more second reflecting members are oriented in a third position symmetrical to the second position with respect to the central axis, and have a second reflecting surface inclined with respect to the central axis.

7. The first light incident on the first position of the multiple reflecting mirror is The light is reflected by the concave mirror and enters the first reflecting member, The light is reflected by the first reflecting member and enters the concave mirror, The light is reflected by the concave mirror and exits from the multiple reflecting mirror. The second light incident on the second position of the multiple reflecting mirror is The light is reflected by the concave mirror and enters the first reflecting member, The light is reflected by the first reflecting member and enters the concave mirror, The light is reflected by the concave mirror and enters the second reflecting member, The light is reflected by the second reflecting member and enters the concave mirror, The light is reflected by the concave mirror and enters the first reflecting member, The light is reflected by the first reflecting member and enters the concave mirror, The light is reflected by the concave mirror and exits from the multiple reflecting mirror. The measurement method according to claim 3.

8. The measurement method according to claim 1 , further comprising an incident process of causing a light flux including the first light and the second light to be incident on the multiple reflecting mirror.

9. A process of installing a plurality of the multiple reflecting mirrors having different axial directions at predetermined positions, In the incidence process, the light beam emitted from a light source is made incident on at least one of the plurality of multiple reflecting mirrors; 9. The method according to claim 8, wherein in the measurement process, a first intensity of the first light and an intensity of the second light emitted from at least one of the plurality of multiple reflecting mirrors are measured.

10. The measurement method according to claim 9 , wherein the measurement target is a gaseous substance present between the light source and the predetermined location.

11. the measurement target is a window material provided in a container and allowing light from inside the container to pass therethrough; The measurement method according to claim 2 , further comprising a step of arranging the multiple reflecting mirror inside the container so as to face the window material.

12. A container for use in the measurement method according to claim 11, A container body; the window material provided in the container body and allowing light from inside the container body to pass therethrough; The multiple reflecting mirror disposed within the container body; a moving mechanism that moves the multiple reflecting mirror to set the window material in a first state and a second state, In the first state, the multiple reflecting mirror does not face the window material, and light from inside the container body passes through the window material and is emitted to the outside of the container body, A container for use in a method for measuring transmittance, wherein in the second state, the multiple reflection mirror faces the window material, and light from outside the container body passes through the window material, is reflected by the multiple reflection mirror, and is emitted outside the container body.

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