Optical systems and optical measuring instruments

Abstract

SOLUTION: An optical system includes: a reflection type first linear polarizer for receiving linearly polarized light transmitted through a sample; and a switching section for controlling a polarization direction of the first linear polarizer so as to switch between transmission and reflection of the linearly polarized light received by the first linear polarizer. In the optical system, the transmission frequency of the light transmitted through the first linear polarizer through the sample before reaching an optical receiver is different from the transmission frequency of the light reflected against the first linear polarizer through the sample before reaching the optical receiver.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to optical systems and optical measuring instruments. [Background technology]

[0002] Patent documents 1 to 3 describe the following: "The variable optical path length cell 1 has a protective member 20a into which a transmissive member 20b is inserted, and a position-adjusting male screw portion 23 is formed on the protective member 20a for adjusting the optical path length based on the sample M to be measured. By moving the protective member 20a in a predetermined direction based on the sample M to be measured and adjusting its position, the optical path length can be adjusted to the optimal length." (Paragraph 0032 of Reference Document 1). [Prior art document] [Patent] [Patent Document 1] Japanese Unexamined Patent Publication No. 2009-180665 [Patent Document 2] Japanese Patent Application Laid-Open No. 9-218149 [Patent Document 3] Japanese Unexamined Patent Publication No. 2005-91093 [Overview of the project]

[0003] In a first embodiment of the present invention, an optical system is provided comprising: a reflective first linear polarizer that receives linearly polarized light transmitted through a sample; and a switching unit that controls the polarization direction of the first linear polarizer to switch between transmitting or reflecting the linearly polarized light received by the first linear polarizer, wherein the number of times the light transmitted through the first linear polarizer passes through the sample before reaching the photodetector is different from the number of times the light reflected by the first linear polarizer passes through the sample before reaching the photodetector.

[0004] The optical system described above further includes a reflective member that reflects linearly polarized light transmitted through the sample in the opposite direction and transmits it back through the sample, causing it to be incident on the first linear polarizer, and the reflective member may reverse the polarization direction of the light emitted from the reflective member in at least one direction perpendicular to the optical axis direction with respect to the polarization direction of the light incident on the reflective member.

[0005] In the optical system described above, the reflective member may have at least one roof mirror that reflects the incident light twice and emits it in opposite directions.

[0006] In the optical system described above, the reflective member comprises n roof mirrors, numbered from the first to the nth (where n is an odd number of 3 or more), arranged sequentially along the optical path. Each of the n roof mirrors, from the first to the (n-1th), reflects the light transmitted through the sample and transmits it back through the sample, causing it to be incident on the next roof mirror in the optical path. The nth roof mirror transmits the emitted light through the sample and causes it to be incident on the first linear polarizer.

[0007] In any of the optical systems having the reflective member, the first linear polarizer is positioned opposite the reflective member with the sample in between, and transmits linearly polarized light from the light source, with the transmission axis direction of the first linear polarizer as the polarization direction, transmits the light through the sample, and causes it to enter the reflective member, while also receiving the light that has been reflected by the reflective member and transmitted through the sample.

[0008] In the optical system described above, the transmission axis and reflection axis of the first linear polarizer are orthogonal to each other, and the reflecting member reverses the polarization direction of the light emitted from the reflecting member in a direction orthogonal to the optical axis direction with respect to the polarization direction of the light incident on the reflecting member, and maintains this in the optical axis direction and the reference axis direction orthogonal to that direction, and the switching unit may rotate the first linear polarizer while maintaining its orientation so that the transmission axis is directed in a direction orthogonal to the reference axis direction and in a direction that makes an angle of ±45 degrees or ±135 degrees with respect to the reference axis direction.

[0009] In the optical system described above, a half-mirror is provided that transmits a portion of the light emitted from the light source to the first linear polarizer and reflects a portion of the light from the first linear polarizer toward the light source toward the photodetector, and a second linear polarizer is provided on the optical path between the half-mirror and the photodetector. The switching unit may rotate the second linear polarizer while maintaining its orientation, so that the angle between the transmission axis of the second linear polarizer and the reference axis is the same as the angle between the transmission axis of the first linear polarizer and the reference axis.

[0010] In any of the optical systems having the reflective member, a third linear polarizer may be further provided, which is positioned in the optical path between the light source and the reflective member.

[0011] In the optical system described above, a half-mirror is further provided that transmits a portion of the light emitted from the light source and directs it onto the third linear polarizer, and reflects a portion of the light from the third linear polarizer toward the light source toward the photodetector, wherein the third linear polarizer transmits linearly polarized light that has been reflected by the first linear polarizer, transmitted through the sample, and further reflected by the reflective member and transmitted through the sample.

[0012] In the optical system described above, a reflective fourth linear polarizer is further provided, which is positioned in the optical path between the half mirror and the photodetector, and in the optical path between the first linear polarizer and the photodetector. The reflective member reverses the polarization direction of the light emitted from the reflective member in a direction perpendicular to the optical axis direction with respect to the polarization direction of the light incident on the reflective member, and maintains this in the optical axis direction and a reference axis direction perpendicular to that direction. The transmission axes of the third linear polarizer and the fourth linear polarizer are at an angle θ other than ±90 degrees with respect to the reference axis direction. The switching unit rotates the first linear polarizer while maintaining its orientation, and the transmission axis of the first linear polarizer may be directed in a direction that forms an angle (-θ) with respect to the reference axis direction and in a direction that forms an angle θ with respect to the reference axis direction.

[0013] In the optical system described above, the transmission axis and reflection axis of the first linear polarizer and the fourth linear polarizer are orthogonal to each other, and the angle θ may be either ±45 degrees or ±135 degrees.

[0014] In any of the optical systems having the reflective member, a reflective fifth linear polarizer is further provided which transmits linearly polarized light from the light source, with the transmission axis direction as the polarization direction, and guides it through the sample to an optical path from the reflective member toward the first linear polarizer, and which reflects the light reflected by the first linear polarizer and guides it toward the optical path, wherein the reflective member reverses the polarization direction of the light emitted from the reflective member in a direction perpendicular to the optical axis direction with respect to the polarization direction of the light incident on the reflective member, and maintains this in the optical axis direction and a reference axis direction perpendicular to that direction, and the switching unit rotates the first linear polarizer and the fifth linear polarizer while maintaining their orientation, and the transmission axes of the first linear polarizer and the fifth linear polarizer may be directed toward a first direction parallel or perpendicular to the reference axis direction and a second direction that is at the same angle with respect to the reference axis direction and is not parallel or perpendicular to the reference axis direction, respectively.

[0015] In the optical system described above, the transmission axis and reflection axis of the first linear polarizer and the fifth linear polarizer are orthogonal to each other, and the second direction may be at an angle of ±45 degrees or ±135 degrees with respect to the reference axis direction.

[0016] In the optical system described above, the first linear polarizer and the fifth linear polarizer are arranged with their optical surfaces facing each other across the reference axis direction such that the internal angle is 90 degrees, and the optical system further comprises an image rotator positioned on the optical path between the first linear polarizer and the fifth linear polarizer, and the image rotator may invert the polarization direction of the light emitted from the image rotator in the direction perpendicular to the optical axis direction and the reference axis direction, while maintaining the polarization direction of the light incident on the image rotator in the direction perpendicular to the reference axis direction.

[0017] In any of the optical systems described above, light may be incident perpendicularly to the sample.

[0018] In any of the optical systems described above, the first linear polarizer may be a wire grid polarizer.

[0019] In a second aspect of the present invention, an optical measuring instrument is provided, comprising any optical system of the first aspect, a light source that emits light into the optical system, and a light receiver that receives the light emitted from the optical system.

[0020] In the optical measuring instrument described above, the sample may be a fluid flowing through a light-transmitting flow cell.

[0021] It should be noted that the above summary of the invention does not enumerate all the necessary features of the present invention. Furthermore, subcombinations of these features may also constitute an invention. [Brief explanation of the drawing]

[0022] [Figure 1] This embodiment shows the optical measuring instrument 1. [Figure 2] This shows the optical path when the transmission axes of linear polarizers 22 and 24 are oriented at an angle of -45 degrees with respect to the reference axis direction. [Figure 3] An optical measuring instrument 1A according to the second embodiment is shown. [Figure 4] This shows the optical path when the transmission axis of the linear polarizer 35 is oriented in the second direction. [Figure 5] An optical measuring instrument 1B according to the third embodiment is shown. [Figure 6] This shows the optical path when the transmission axes of the linear polarizers 41 and 43 are oriented in the second direction. [Figure 7] This shows the polarization direction of light Li4_45deg. [Figure 8] This shows the polarization direction of light Li5⁻⁴⁵deg. [Figure 9] This shows the polarization direction of light Li6_45deg. [Figure 10]This shows the polarization direction of light Li7_45deg. [Modes for carrying out the invention]

[0023] The present invention will be described below through embodiments of the invention, but these embodiments are not intended to limit the invention as defined in the claims. Furthermore, not all combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0024] <First Embodiment> (Configuration of Optical Measuring Instrument 1) Figure 1 shows an optical measuring instrument 1 according to this embodiment. The optical measuring instrument 1 comprises a flow cell 10, a light source 11, an optical system 2, a photodetector 14, and a computing device 15. In the figure, the X-axis direction is from the back side to the front side of the paper, the Y-axis direction is from the right side to the left side, and the Z-axis direction is from the top side to the bottom side. The X-axis, Y-axis, and Z-axis directions may be orthogonal to each other.

[0025] ((Flow Cell 10)) The flow cell 10 may be a hollow member that houses the sample 100 inside. In this embodiment, for example, the flow cell 10 may have the sample 100 flowing through it, and at least a portion of the region through which light passes by the optical system 2 may be translucent. The sample 100 may be a fluid flowing inside the flow cell 10, and may be a liquid or a gas. A flow synthesis device (not shown) may be connected to the flow cell 10 to mix multiple components and flow them into the flow cell 10 as the sample 100.

[0026] ((light source 11)) The light source 11 emits light into the optical system 2. The light source 11 may emit unpolarized light in the Z-axis direction. The light emitted from the light source 11 may be ultraviolet light, visible light, near-infrared light, infrared light, or terahertz light, or light of other wavelengths. The light source 11 may be a laser light source such as an Ar laser, or it may be an LED or a tungsten lamp, for example.

[0027] ((Optical system 2)) The optical system 2 guides light from the light source 11 through the sample 100 to the photodetector 14. In this embodiment, the optical system 2 may have light incident perpendicular to the sample 100, and the light may be incident perpendicular to the sample 100 each time light passes through the sample 100. The optical system 2 includes a half mirror 21, a linear polarizer 22, a reflective member 23, a linear polarizer 24, and a switching unit 25. Of these, the half mirror 21, the linear polarizer 22, and the reflective member 23 are arranged in the Z-axis direction together with the light source 11. The half mirror 21 and the linear polarizer 24 are arranged in the Y-axis direction together with the photodetector 14, which will be described later.

[0028] (((Half Mirror 21))) The half mirror 21 transmits a portion of the received light and reflects the other portion. The half mirror 21 may transmit a portion of the light emitted from the light source 11 and allow it to enter the linear polarizer 22. The half mirror 21 may also reflect a portion of the light from the linear polarizer 22 toward the light source 11 toward the linear polarizer 24. The half mirror 21 may be positioned at an angle to the optical axis between the light source 11 and the reflective member 23, and in this embodiment, as an example, it may be positioned at a 45-degree angle to the Z-axis direction.

[0029] (((Linear polarizer 22))) The linear polarizer 22 is an example of a first linear polarizer. The linear polarizer 22 may be positioned opposite the reflective member 23 with the sample 100 in between, and in this embodiment, as an example, it may be positioned opposite the reflective member 23 with the flow cell 10 containing the sample 100 in between. The linear polarizer 22 may be positioned perpendicular to the optical axis between the light source 11 and the reflective member 23. The linear polarizer 22 may be positioned at a distance from the flow cell 10, or it may be positioned in contact with the flow cell 10.

[0030] The linear polarizer 22 may be a reflective polarizer and may have a transmission axis, which is the polarization direction of the transmitted light, and a reflection axis, which is the polarization direction of the reflected light. The transmission axis and reflection axis of the linear polarizer 22 may intersect each other, and in this embodiment, they are orthogonal as an example. In this embodiment, as an example, the linear polarizer 22 may be a wire grid polarizer, which may be composed of a plurality of parallel metal wires sandwiched between a transparent substrate such as glass. The transmission axis of the wire grid polarizer may be perpendicular to the direction in which the wires extend, or parallel to the direction in which the wires are arranged. The reflection axis of the wire grid polarizer may be parallel to the direction in which the wires extend.

[0031] The linear polarizer 22 may transmit linearly polarized light emitted from the light source 11, where the polarization direction is along the transmission axis of the linear polarizer 22 (i.e., linearly polarized light that vibrates along the transmission axis), allowing it to pass through the sample 100 and into the reflecting member 23. Alternatively, the linear polarizer 22 may reflect linearly polarized light emitted from the light source 11, where the polarization direction is along the reflection axis, and allow it to be incident on the half mirror 21.

[0032] The linear polarizer 22 may receive linearly polarized light that has passed through the sample 100, and in this embodiment, as an example, it may receive light that has been reflected by the reflective member 23 and passed through the sample 100. As will be described in detail later, the linear polarizer 22 may reflect or transmit the light depending on the polarization direction of the light that has passed through the linear polarizer 22 and been reflected by the reflective member 23.

[0033] The linear polarizer 22 may be held by a holding member 220. The holding member 220 may hold the linear polarizer 22 so that it can be rotated while maintaining its orientation. Rotating the linear polarizer 22 while maintaining its orientation means rotating the linear polarizer 22 without changing the orientation of its optical surface.

[0034] (((Reflective member 23))) The reflective member 23 reflects the linearly polarized light that passes through the sample 100 in the opposite direction, transmits it back through the sample 100, and directs it onto the linear polarizer 22. In this embodiment, as an example, the reflective member 23 may receive light traveling in a straight line in the positive Z-axis direction and reflect the light in the negative Z-axis direction.

[0035] The reflective member 23 may invert the polarization direction of the light emitted from the reflective member 23 in at least one direction perpendicular to the optical axis direction (in this embodiment, for example, the Z axis direction) with respect to the polarization direction of the light incident on the reflective member 23. For example, the reflective member 23 may invert the polarization direction of the emitted light in one direction perpendicular to the optical axis direction (in this embodiment, for example, the Y axis direction) with respect to the polarization direction of the incident light, and maintain it in the optical axis direction and a reference axis direction perpendicular to that one direction (in this embodiment, for example, the X axis direction).

[0036] The reflective member 23 may have at least one roof mirror 230 that reflects incident light twice and emits it in opposite directions, and in this embodiment, as an example, it has a single roof mirror 230. The roof mirror 230 may be formed by facing two reflective planes along the reference axis direction (in this embodiment, as an example, the X axis direction) so that the interior angle is 90 degrees. The two reflective planes may be in contact with each other along the reference axis direction. In this embodiment, as an example, the roof mirror 230 may be a right-angle prism, but it may also be formed by bringing two plane mirrors into contact. The roof mirror 230 may be positioned at a distance from the flow cell 10, in contact with the flow cell 10, or as part of the window member of the flow cell 10.

[0037] (((Linear polarizer 24))) The linear polarizer 24 is an example of a second linear polarizer and is positioned in the optical path between the half mirror 21 and the photodetector 14. The linear polarizer 24 may be either an absorptive or reflective type, but in this embodiment it is a reflective type as an example and has a transmission axis and a reflection axis. The transmission axis and reflection axis of the linear polarizer 24 may intersect each other, and in this embodiment they are orthogonal as an example. In this embodiment, the linear polarizer 24 may be a wire grid polarizer as an example.

[0038] The linear polarizer 24 may be positioned at an angle to the optical axis between the half mirror 21 and the photodetector 14. In this embodiment, for example, it may be positioned at a 45-degree angle to the Y-axis. As will be described in detail later, the linear polarizer 24 may either reflect and remove the light emitted from the half mirror 21 toward the photodetector 14, or transmit the light and allow it to enter the photodetector 14, depending on the polarization direction of the light.

[0039] The linear polarizer 24 may be held by a holding member 240. The holding member 240 may hold the linear polarizer 24 so that it can rotate while maintaining its orientation.

[0040] (((Switching section 25))) The switching unit 25 controls the polarization direction of the linear polarizer 22 to switch between transmitting or reflecting the linearly polarized light received by the linear polarizer 22. As a result, the optical path of the light emitted from the linear polarizer 22 may be switched between an optical path toward the photodetector 14 and an optical path that further transmits through the sample 100 before reaching the photodetector 14. In other words, the number of times the light transmitted through the linear polarizer 22 passes through the sample 100 before reaching the photodetector 14 may be different from the number of times the light reflected by the linear polarizer 22 passes through the sample 100 before reaching the photodetector 14.

[0041] The switching unit 25 may control the polarization direction by rotating the linear polarizer 22 while maintaining its orientation. The switching unit 25 may rotate the linear polarizer 22 via the holding member 220. The switching unit 25 may orient the transmission axis of the linear polarizer 22 in a direction perpendicular to the reference axis direction (in this embodiment, for example, the X axis direction) (in this embodiment, for example, the Y axis direction) and in a direction that makes an angle of ±45 degrees or ±135 degrees with respect to the reference axis direction.

[0042] The switching unit 25 may further control the polarization direction of the linear polarizer 24 to switch between transmitting or reflecting the linearly polarized light received by the linear polarizer 24. The switching unit 25 may rotate the linear polarizer 24 while maintaining its orientation. The switching unit may rotate the linear polarizer 24 via the holding member 240. The switching unit 25 may make the angle that the transmission axis of the linear polarizer 24 makes with respect to the reference axis direction (in this embodiment, for example, the X-axis direction) match the angle that the transmission axis of the linear polarizer 22 makes with respect to the reference axis direction. For example, if the switching unit 25 directs the transmission axis of the linear polarizer 22 to 45 degrees with respect to the X-axis direction, the transmission axis of the linear polarizer 24 may be directed to 45 degrees with respect to the X-axis direction. Note that 135 degrees with respect to the X-axis direction may be the same as -45 degrees with respect to the X-axis direction, and -135 degrees with respect to the X-axis direction may be the same as 45 degrees with respect to the X-axis direction.

[0043] (((Receiver 14))) The photodetector 14 receives light emitted from the optical system. The photodetector 14 may measure the intensity and spectrum of the light. For example, the photodetector 14 may be a photodiode or a phototransistor. The photodetector 14 may supply a signal corresponding to the received light (for example, a signal indicating the intensity of the light or a signal indicating the spectrum of the light) to the computing unit 15.

[0044] (((Arithmetic unit 15))) The arithmetic unit 15 calculates the results of measurement or analysis of the sample 100 based on the signal supplied from the light receiver 14. When the optical measuring device 1 is an absorptiometer, the arithmetic unit 15 may calculate the absorbance or transmittance of the sample 100 by absorptiometry. When the optical measuring device 1 is a spectroscope, the arithmetic unit 15 may calculate the results of qualitative or quantitative analysis of the components of the sample 100 by spectroscopy. The arithmetic unit 15 may also calculate the component concentration in the sample 100 or the like by the differential absorption spectrum method using the difference between spectra (also referred to as an absorbance difference spectrum) obtained by switching the optical path.

[0045] ((Operation)) Next, the operation of the optical system 2 according to this embodiment will be described. In the following description, angles such as "90 deg" appended to symbols such as the linear polarizers 22 and 24 indicate the angle of the transmission axis with respect to the reference axis direction (in this embodiment, the X-axis direction as an example). Also, for the light L a1 , L b1 angles such as "90 deg" appended to symbols indicate the angle of the polarization direction with respect to the reference axis direction.

[0046] (((When the transmission axes of the linear polarizer 22 and the linear polarizer 24 are orthogonal to the reference axis direction))) FIG. 1 shows the optical path when the transmission axes of the linear polarizer 22 and the linear polarizer 24 are directed in a direction orthogonal to the reference axis direction. When the transmission axes of the linear polarizer 22 and the linear polarizer 24 are orthogonal to the reference axis direction, a part of the unpolarized light L0 emitted from the light source 11 passes through the half mirror 21 and enters the linear polarizer 22 _90deg .

[0047] Linear polarizer 22 _90deg Of the unpolarized light L0 incident on the linear polarizer 22, the linearly polarized component with the reflection axis direction (here, the X-axis direction) of the linear polarizer 22 as the polarization direction is reflected by the linear polarizer 22 _90deg and becomes linearly polarized light L _90deg and enters the half mirror 21. A part of the linearly polarized light L b1_0deg incident on the half mirror 21 is reflected and becomes light L b1_0deg and a part of it is reflected to become light L b2_0degAfter that, the linear polarizer 24 _90deg The light is then reflected further. b3_0deg And so it is removed.

[0048] Meanwhile, the linear polarizer 22 _90deg Of the unpolarized light L0 incident on the device, the linear polarizer 22 _90deg The component of linearly polarized light with the transmission axis direction (in this case, the Y-axis direction) is the linear polarizer 22 _90deg Linearly polarized light L passes through a1_90deg As a result, linearly polarized light L is transmitted through the sample 100, reflected by the reflective member 23 (in this embodiment, a roof mirror 230 as an example), and its polarization direction is reversed in the Y-axis direction. a2_-90deg Thus, the linear polarizer 22 _90deg When the transmission axis direction is perpendicular to the reference axis direction, linearly polarized light L has the transmission axis direction as its polarization direction. a1_90deg The light L is incident on the roof mirror 230 and reflected, and linearly polarized light with the direction of the transmission axis as the polarization direction. a2_-90deg The light L emitted from the roof mirror 230 is therefore linearly polarized light L emitted from the roof mirror 230. a2_-90deg This is sample 100 and linear polarizer 22 _90deg The light L passes through and enters the half mirror 21. Then, the linearly polarized light L that enters the half mirror 21 a2_-90deg Some of it is reflected and becomes light L a3_-90deg And so, linear polarizer 24 _90deg The light passes through and enters the light receiver 14.

[0049] Therefore, when the transmission axis directions of the linear polarizers 22 and 24 are perpendicular to the reference axis direction, the linear polarizer 22 is transmitted from the roof mirror 230. _90deg Light L incident on a2_-90deg The light is guided through the linear polarizer 22 into an optical path leading to the photodetector 14, and the light emitted from the light source 11 passes through the sample 100 a total of two times before entering the photodetector 14. The above operation is the same whether the transmission axes of the linear polarizers 22 and 24 are at -90 degrees, ±270 degrees, 0 degrees, or ±180 degrees with respect to the reference axis direction.

[0050] (((When the transmission axes of linear polarizers 22 and 24 form an angle of -45 degrees with respect to the reference axis direction))) Figure 2 shows the optical path when the transmission axes of linear polarizers 22 and 24 are oriented at -45 degrees from the reference axis. When the transmission axes of linear polarizers 22 and 24 are at an angle of -45 degrees from the reference axis, a portion of the unpolarized light L0 emitted from the light source 11 passes through the half mirror 21 and into the linear polarizer 22 _-45deg It is incident on.

[0051] Linear polarizer 22 _-45deg Of the unpolarized light L0 incident on the device, the linear polarizer 22 _-45deg The linearly polarized component whose polarization direction is the reflection axis direction (here, the direction that is 45 degrees with respect to the X-axis direction) is linearly polarized by 22 _-45deg The linearly polarized light L is reflected by the surface. d1_45deg The light L incident on the half mirror 21 then enters the half mirror 21. d1_45deg Some of it is reflected, and linearly polarized light L d2_45deg After that, a linear polarizer 24 _-45deg The light is reflected by L d3_45deg And so it is removed.

[0052] Meanwhile, the linear polarizer 22 _-45deg Of the unpolarized light L0 incident on the device, the linear polarizer 22 _-45deg The linearly polarized component, whose polarization direction is the transmission axis direction (here, the direction at -45 degrees with respect to the X-axis direction), is obtained by the linear polarizer 22 _-45deg Light L passes through c1_-45deg As a result, linearly polarized light L is transmitted through sample 100, reflected by roof mirror 230, and its polarization direction is reversed in the Y-axis direction. c2_45deg This is the result. When the transmission axis direction of the linear polarizer 22 is at an angle of -45 degrees with the reference axis direction, the polarization direction changes by 90 degrees before and after reflection by the roof mirror 230. As a result, the linearly polarized light L whose polarization direction is the transmission axis direction of the linear polarizer 22 c1_-45deg The light L is incident on the roof mirror 230 and reflected, and its polarization direction is perpendicular to the transmission axis of the linear polarizer 22, i.e., the reflection axis. c2_45degThe light L emitted from the roof mirror 230 is therefore linearly polarized light L emitted from the roof mirror 230. c2_45deg The linear polarizer 22 passes through the sample 100. _-45deg The linearly polarized light L is reflected by the surface. c3_45deg After that, the sample 100 is passed through and reflected again by the roof mirror 230.

[0053] Linearly polarized light L reflected again by the roof mirror 230 c3_45deg This is linearly polarized light L, whose polarization direction is reversed in the Y-axis direction. c4_-45deg As a result, the polarization direction changes by 90 degrees before and after reflection by the roof mirror 230. This causes the linearly polarized light L to have the reflection axis of the linear polarizer 22 as its polarization direction. c3_45deg The light L is incident on the roof mirror 230 and reflected, and the linearly polarized light L has the direction of polarization as the transmission axis of the linear polarizer 22. c4_-45deg The light L is emitted from the roof mirror 230. c4_-45deg This is sample 100 and linear polarizer 22 _-45deg The light L passes through and enters the half mirror 21. Then, the linearly polarized light L that enters the half mirror 21 c4_-45deg Some of it is reflected and becomes light L c5_-45deg And so, linear polarizer 24 _-45deg The light passes through and enters the light receiver 14.

[0054] Therefore, when the transmission axes of the linear polarizers 22 and 24 are at a -45 degree angle with the reference axis, the linear polarizer 22 _-45deg Light L incident on c2_45deg The light is reflected by the linear polarizer 22, passes through the sample 100 again, and is reflected by the reflective member 23, and the linear polarizer 22 _-45deg The light emitted from the light source 11 is guided into the optical path into which it enters the light receiver 14, and passes through the sample 100 a total of four times before entering the light receiver 14. The above operation is the same even when the transmission axes of the linear polarizers 22 and 24 are at 45 degrees, 135 degrees, or -135 degrees with respect to the reference axis.

[0055] According to the optical measuring instrument 1 described above, the polarization direction of the linear polarizer 22 is controlled, and the linear polarizer 22 can switch between transmitting or reflecting the linearly polarized light it receives. The number of times the light transmitted through the linear polarizer 22 passes through the sample 100 before reaching the photodetector 14 is different from the number of times the light reflected by the linear polarizer 22 passes through the sample 100 before reaching the photodetector 14. Therefore, by controlling the polarization direction of the linear polarizer 22, the optical path length passing through the sample 100 can be switched. Thus, unlike the case where the thickness of the sample 100 is changed by changing the thickness of the flow cell 10, the optical path length passing through the sample 100 can be switched while preventing changes in the pressure applied to the sample 100.

[0056] Furthermore, the reflective member 23, which reflects linearly polarized light and directs it onto the linear polarizer 22, reverses the polarization direction of the emitted light in at least one direction perpendicular to the optical axis with respect to the polarization direction of the incident light. Therefore, by reflecting light with the reflective member 23, the polarization direction can be controlled to a predetermined direction. In addition, since linearly polarized light is transmitted through the sample 100 before and after reflection by the reflective member 23, the optical path length within the sample 100 can be increased.

[0057] Furthermore, since the reflective member 23 is equipped with at least one roof mirror 230 that reflects incident light twice and emits it in the opposite direction, the polarization direction of the emitted light can be reversed with respect to the polarization direction of the incident light of the reflective member 23 with a simple configuration.

[0058] Furthermore, the linear polarizer 22 is positioned opposite the reflective member 23 with the sample 100 in between, and transmits linearly polarized light from the light source 11, with the transmission axis direction as the polarization direction, to the reflective member 23 via the sample 100, and receives the light that has been reflected by the reflective member 23 and transmitted through the sample 100.Therefore, by controlling the polarization direction of the linear polarizer 22, it is possible to switch between guiding the light incident on the linear polarizer 22 from the reflective member 23 through the linear polarizer 22 to an optical path toward the photodetector 14, or guiding the light reflected by the linear polarizer 22, again passing through the sample 100, being reflected by the reflective member 23, and then guiding it to an optical path incident on the linear polarizer 22.

[0059] Furthermore, the transmission axis and reflection axis of the linear polarizer 22 are orthogonal to each other, and the reflective member 23 reverses the polarization direction of the emitted light in the Y-axis direction, which is orthogonal to the optical axis direction, relative to the polarization direction of the incident light, and maintains it in the X-axis direction. The switching unit 25 rotates the linear polarizer 22 while maintaining its orientation so that the transmission axis is directed in the Y-axis direction and in a direction that makes an angle of ±45 degrees or ±135 degrees with respect to the X-axis direction. Therefore, by directing the transmission axis of the linear polarizer 22 in the Y-axis direction, the light emitted from the light source 11 can be transmitted through the sample 100 twice before passing through the linear polarizer 22 and being incident on the photodetector 14. Alternatively, by directing the transmission axis of the linear polarizer 22 in a direction that makes an angle of ±45 degrees or ±135 degrees with respect to the X-axis direction, the light emitted from the light source 11 can be transmitted through the sample 100 four times before passing through the linear polarizer 22 and being incident on the photodetector 14. Therefore, by rotating the linear polarizer 22, the optical path length passing through the sample 100 can be switched.

[0060] Furthermore, the half-mirror 21 transmits a portion of the light emitted from the light source 11 and directs it to the linear polarizer 22, while also reflecting a portion of the light from the linear polarizer 22 toward the light source 11 toward the photodetector 14. The switching unit 25 rotates the linear polarizer 24 so that the angle between the transmission axis of the linear polarizer 24 and the reference axis matches the angle between the transmission axis of the linear polarizer 22 and the reference axis. Therefore, after passing through the sample 100, the linearly polarized light that passes through the linear polarizer 22 toward the light source 11 is at least partially reflected by the half-mirror 21, passes through the linear polarizer 24, and is incident on the photodetector 14. Thus, the light that has passed through the sample 100 and the linear polarizer 22 can be reliably incident on the photodetector 14.

[0061] Furthermore, since the light is incident perpendicularly to the sample 100, it is possible to prevent the optical path from changing due to the refractive index of the sample 100. Therefore, it is possible to prevent a decrease in the accuracy of measurements using the light received by the photodetector 14.

[0062] Furthermore, since the linear polarizers 22 and 24 are wire grid polarizers, they can reliably reflect and transmit linearly polarized light by rotating them while maintaining their orientation.

[0063] Furthermore, since the light emitted from the optical system 2 is received by the photodetector 14, measurements can be performed on the sample 100 by analyzing the received light.

[0064] Furthermore, since the sample 100 is a fluid flowing within a light-transmitting flow cell 10, measurements can be performed on the fluid sample.

[0065] <Second Embodiment> (Configuration of Optical Measuring Instrument 1A) Figure 3 shows an optical measuring instrument 1A according to the second embodiment. The optical measuring instrument 1A includes an optical system 3. In the second embodiment and the third embodiment described later, components that are substantially the same as those shown in Figure 1 are given the same reference numerals, and their descriptions are omitted.

[0066] ((Optical system 3)) The optical system 3 guides light from the light source 11 through the sample 100 to the photodetector 14. In this embodiment, the optical system 3 may have light incident perpendicularly on the sample 100. The optical system 3 includes a half mirror 31, a linear polarizer 32, a reflective member 33, linear polarizers 34 and 35, and a switching unit 36. Of these, the half mirror 31, the linear polarizer 32, and a part of the reflective member 33 are arranged in the Z-axis direction together with the light source 11, while another part of the reflective member 33 and the linear polarizers 34 and 35 are arranged in the Z-axis direction parallel to these. The half mirror 31 and the linear polarizer 34 are also arranged in the Y-axis direction together with the photodetector 14.

[0067] (((Half Mirror 31))) The half mirror 31 transmits a portion of the received light and reflects the other portion. The half mirror 31 may transmit a portion of the light emitted from the light source 11 and allow it to enter the linear polarizer 32. The half mirror 31 may also reflect a portion of the light from the linear polarizer 32 toward the light source 11 toward the linear polarizer 34. The half mirror 31 may be positioned at an angle to the optical axis between the light source 11 and the reflective member 33, and in this embodiment, as an example, it may be positioned at a 45-degree angle to the Z-axis direction.

[0068] (((Linear polarizer 32))) The linear polarizer 32 is an example of a third linear polarizer and is positioned in the optical path between the light source 11 and the reflective member 33. The linear polarizer 32 may be positioned opposite a part of the reflective member 33 with the sample 100 in between, and in this embodiment, as an example, it may be positioned opposite the roof mirror 330(1) on the reflective member 33, described later, with the flow cell 10 containing the sample 100 in between. The linear polarizer 32 may be positioned perpendicular to the optical axis between the light source 11 and the reflective member 33. The linear polarizer 32 may be positioned at a distance from the flow cell 10, or it may be positioned in contact with the flow cell 10.

[0069] The linear polarizer 32 may be either an absorptive or reflective type, but in this embodiment, it is a reflective type as an example and has a transmission axis and a reflection axis. The transmission axis and reflection axis of the linear polarizer 32 may intersect each other, and in this embodiment, they are orthogonal as an example. In this embodiment, the linear polarizer 32 may be a wire grid polarizer as an example.

[0070] The transmission axis of the linear polarizer 32 may be fixed and make an angle θ other than 90 degrees (for example, -45 degrees in this embodiment) with respect to the reference axis direction (for example, the X-axis direction in this embodiment). The angle θ may be either ±45 degrees or ±135 degrees, and for example, in this embodiment it is -45 degrees.

[0071] The linear polarizer 32 may transmit linearly polarized light emitted from the light source 11, whose polarization direction is along the transmission axis (in this embodiment, for example, a direction at a 45-degree angle to the X-axis), and allow it to pass through the sample 100 and into the reflecting member 33. Alternatively, the linear polarizer 32 may reflect linearly polarized light emitted from the light source 11, whose polarization direction is along the reflection axis (in this embodiment, for example, a direction at a 45-degree angle to the X-axis), and allow it to be incident on the half mirror 31.

[0072] The linear polarizer 32 may receive linearly polarized light that has passed through the sample 100. In this embodiment, for example, the linear polarizer 32 may receive linearly polarized light that has been reflected by the linear polarizer 35, passed through the sample 100, and then further reflected by the reflective member 33 and passed through the sample 100. As will be described in detail later, the linearly polarized light may pass through the linear polarizer 32 because its polarization direction is along the transmission axis of the linear polarizer 32.

[0073] (((Reflective member 33))) The reflective member 33 reflects the linearly polarized light that passes through the sample 100 in the opposite direction, transmits it back through the sample 100, and directs it onto the linear polarizer 35. In this embodiment, as an example, the reflective member 33 may receive light in the positive Z-axis direction and reflect light in the negative Z-axis direction.

[0074] Similar to the reflective member 23 in the first embodiment, the reflective member 33 may reverse the polarization direction of the light emitted from the reflective member 33 in at least one direction perpendicular to the optical axis direction (in this embodiment, for example, the Z axis direction) with respect to the polarization direction of the light incident on the reflective member 33. For example, the reflective member 33 may reverse the polarization direction of the emitted light in one direction perpendicular to the optical axis direction (in this embodiment, for example, the Y axis direction) with respect to the polarization direction of the incident light, and maintain it in the optical axis direction and a reference axis direction perpendicular to that one direction (in this embodiment, for example, the X axis direction).

[0075] The reflective member 33 may have at least one roof mirror 330 that reflects incident light twice and emits it in opposite directions. For example, it may have n roof mirrors 330 from the first to the nth (where n is an odd number of 3 or more) arranged in sequence along the optical path. Of these, the first to the (n-1)th roof mirrors 330 may fold back the light that has passed through the sample 100 and transmit it back through the sample 100 to the next roof mirror 330 in the optical path, while the nth roof mirror 330 may transmit the emitted light back through the sample 100 to the linear polarizer 35.

[0076] In this embodiment, as an example, the reflective member 33 has first to third roof mirrors 330 (also referred to as roof mirrors 330(1) to 330(3)). Of these, the odd-numbered first and third roof mirrors 330(1) and 330(3) may be positioned on the side of the flow cell 10 opposite to the light source 11, and may face the linear polarizers 32 and 35 with the sample 100 in between. The even-numbered second roof mirror 330(2) may be positioned on the side of the flow cell 10 toward the light source 11. Light emitted from the linear polarizer 32 and incident on the first roof mirror 330(1) may be emitted from the third roof mirror 330(3) and incident on the linear polarizer 35, and light emitted from the linear polarizer 35 and incident on the third roof mirror 330(3) may be emitted from the first roof mirror 230 and incident on the linear polarizer 32. Each roof mirror 330 may be formed with two reflective planes facing each other in the reference axis direction (in this embodiment, for example, the X-axis direction) so that the interior angle is 90 degrees, similar to the roof mirror 230 in the first embodiment. Each roof mirror 330 may be positioned at a distance from the flow cell 10, in contact with the flow cell 10, or as part of the window member of the flow cell 10.

[0077] (((Linear polarizer 34))) The linear polarizer 34 is an example of a fourth linear polarizer and is positioned in the optical path between the half mirror 31 and the photodetector 14, and in the optical path between the linear polarizer 35 and the photodetector 14. The linear polarizer 34 may be a reflective polarizer and has a transmission axis and a reflection axis. The transmission axis and reflection axis of the linear polarizer 34 may intersect each other, and in this embodiment, they are orthogonal as an example. In this embodiment, the linear polarizer 34 may be a wire grid polarizer as an example. The transmission axis of the linear polarizer 34 may be fixed and, similar to the linear polarizer 32, forms an angle θ with respect to the reference axis direction (in this embodiment, -45 degrees with respect to the X axis as an example).

[0078] The linear polarizer 34 may be positioned at an angle to the optical axis between the half mirror 31 and the photodetector 14. In this embodiment, for example, it may be positioned at a 45-degree angle to the Y-axis. As will be described in detail later, the linear polarizer 34 may either reflect and remove the light emitted from the half mirror 31 toward the photodetector 14, or transmit the light and allow it to enter the photodetector 14, depending on the polarization direction of the light.

[0079] (((Linear polarizer 35))) The linear polarizer 35 is an example of a first linear polarizer and may be positioned opposite a part of the reflective member 33 with the sample 100 in between. In this embodiment, for example, it may be positioned opposite the roof mirror 330(3) on the reflective member 33 with the flow cell 10 containing the sample 100 in between. The linear polarizer 35 may be positioned perpendicular to the optical axis between the reflective member 33 and the linear polarizer 34. The linear polarizer 35 may be positioned at a distance from the flow cell 10 or in contact with the flow cell 10.

[0080] The linear polarizer 35 may be a reflective polarizer and may have a transmission axis and a reflection axis. The transmission axis and reflection axis of the linear polarizer 35 may intersect each other, and in this embodiment, they are orthogonal as an example. In this embodiment, the linear polarizer 35 may be a wire grid polarizer as an example.

[0081] The linear polarizer 35 may receive linearly polarized light that has passed through the sample 100. In this embodiment, as an example, it may receive light that has been emitted from the reflecting member 33 and passed through the sample 100. The linear polarizer 35 may transmit linearly polarized light whose polarization direction is in the direction of the transmission axis and allow it to be incident on the linear polarizer 34, and may reflect linearly polarized light whose polarization direction is in the direction of the reflection axis, allow it to pass through the sample 100 and allow it to be incident on the reflecting member 33.

[0082] The linear polarizer 35 may be held by a holding member 350. The holding member 350 may hold the linear polarizer 35 so that it can rotate while maintaining its orientation.

[0083] (((Switching section 36))) The switching unit 36 ​​controls the polarization direction of the linear polarizer 35 to switch between transmitting or reflecting the linearly polarized light received by the linear polarizer 35. As a result, the number of times the light transmitted through the linear polarizer 35 passes through the sample 100 before reaching the photodetector 14 may be different from the number of times the light reflected by the linear polarizer 35 passes through the sample 100 before reaching the photodetector 14.

[0084] The switching unit 36 ​​may control the polarization direction by rotating the linear polarizer 35. The switching unit 36 ​​may rotate the linear polarizer 35 via the holding member 350. The switching unit 36 ​​may orient the transmission axis of the linear polarizer 35 in a direction that makes an angle (-θ) with respect to the reference axis direction (in this embodiment, for example, the X-axis direction) (referred to as the first direction) and in a direction that makes an angle θ with respect to the reference axis direction (referred to as the second direction). In this embodiment, for example, the first direction may be 45 degrees with respect to the X-axis direction, and the second direction may be -45 degrees with respect to the X-axis direction.

[0085] ((action)) Next, the operation of the optical system 3 according to this embodiment will be described.

[0086] (((When the transmission axis of the linear polarizer 35 is oriented in the first direction))) Figure 3 shows the optical path when the transmission axis of the linear polarizer 35 is oriented in the first direction (i.e., the direction at a 45-degree angle with respect to the reference axis). When the transmission axis of the linear polarizer 35 is oriented in the first direction, a portion of the unpolarized light L0 emitted from the light source 11 passes through the half mirror 31 and into the linear polarizer 32 _-45deg It is incident on.

[0087] Linear polarizer 32 _-45deg Of the unpolarized light L0 incident on it, the linear polarizer 32 _-45deg The linearly polarized component whose polarization direction is the reflection axis direction (here, the direction that is 45 degrees with respect to the X axis direction) is linearly polarized by 32 _-45deg The linearly polarized light L is reflected by the surface. f1_45deg The light L incident on the half mirror 31 then enters the half mirror 31. f1_45deg Some of it is reflected, and linearly polarized light L f2_45deg After that, a linear polarizer 34 _-45deg The light is reflected by L f3_45deg And so it is removed.

[0088] Meanwhile, the linear polarizer 32 _-45deg Of the unpolarized light L0 incident on it, the linear polarizer 32 _-45deg The linearly polarized component, whose polarization direction is the transmission axis direction (here, the direction at -45 degrees to the X-axis direction), is obtained by the linear polarizer 32 _-45deg Linearly polarized light L passes through e1_-45deg The light L passes through the sample 100 and enters the roof mirror 330(1). e1_-45deg Each time the light is reflected by the roof mirrors 330(1) to 330A(3), the polarization direction is reversed in the Y-axis direction, resulting in linearly polarized light L e2_45deg ,L e3_-45deg ,L e4_45deg As a result, the light passes through sample 100, and the linear polarizer 35 _45deg It is incident on the light source 11. Thus, in this embodiment, of the light emitted from the light source 11 and transmitted through the half mirror 31, linearly polarized light whose polarization direction is at an angle θ (in this embodiment, -45 degrees) with respect to the reference axis direction is incident on the linear polarizer 32. _-45degand passes through the sample 100 and is reflected by the reflection member 33, and is in the first direction forming an angle (-θ) (in this embodiment, 45 degrees as an example) with respect to the reference axis direction, that is, the linearly polarized light having the transmission axis direction of the linear polarizer 35 _45deg enters the linear polarizer 35 as linearly polarized light whose polarization direction is the transmission axis direction of the linear polarizer 35. Therefore, the linearly polarized light L e4_45deg that exits from the roof mirror 330(3) and passes through the sample 100 _45deg passes through the linear polarizer 35 _-45deg and enters the linear polarizer 34 e4_45deg . Then, the linearly polarized light L _-45deg is reflected by the linear polarizer 34 e5_45deg and becomes the linearly polarized light L

[0089] and enters the light receiver 14. In this way, when the transmission axis of the linear polarizer 35 is directed in the first direction, the light emitted from the light source 11 passes through the sample 100 four times in total and enters the light receiver 14. FIG. 4 shows the optical path when the transmission axis of the linear polarizer 35 is directed in the second direction. When the transmission axis of the linear polarizer 35 is directed in the second direction, a part of the unpolarized light L0 emitted from the light source 11 passes through the half mirror 31 and enters the linear polarizer 32 _-45deg .

[0090] Among the unpolarized light L0 incident on the linear polarizer 32 _-45deg , the component of the linearly polarized light whose polarization direction is the reflection axis direction of the linear polarizer 32 _-45deg (here, the direction forming 45 degrees with respect to the X-axis direction) is reflected in sequence by the linear polarizer 32 _45deg , the half mirror 31, and the linear polarizer 34 _-45deg and becomes the linearly polarized light L f1_-45deg , L f2_-45deg , L f3_45deg and is removed.

[0091] On the other hand, among the unpolarized light L0 incident on the linear polarizer 32 _-45deg , among the unpolarized light L0 incident on the linear polarizer 32 _-45degThe component of linearly polarized light with the polarization axis direction (the direction making -45 degrees with the X-axis direction here) is, as described above, the linearly polarized light L _-45deg that passes through the linear polarizer 32 e1_-45deg and becomes linearly polarized light L e2_45deg , L e3_-45deg , L e4_45deg after passing through the sample 100, and each time it is reflected by the roof mirrors 330(1) to 330A(3), the polarization direction is reversed in the Y-axis direction and becomes linearly polarized light L _-45deg and enters the linear polarizer 35. However, when the transmission axis of the linear polarizer 35 is directed in the second direction, the linearly polarized light L e4_45deg entering the linear polarizer 35 has the polarization direction along the reflection axis direction of the linear polarizer 35.

[0092] Therefore, the linearly polarized light L _-45deg entering the linear polarizer 35 e4_45deg is reflected by the linear polarizer 35 _-45deg and becomes linearly polarized light L g5_45deg and enters the roof mirror 330(3) after passing through the sample 100. The linearly polarized light L g5_45deg entering the roof mirror 330(3) has the polarization direction reversed in the Y-axis direction each time it is reflected by the roof mirrors 330(3) to 330(1) and becomes linearly polarized light L g6_-45deg , L g7_45deg , L g8_-45deg and passes through the sample 100. The linearly polarized light L g8_-45deg emitted from the roof mirror 330(1) and passing through the sample 100 _-45deg passes through the linear polarizer 32 g8_-45deg and enters the half mirror 31. And a part of the linearly polarized light L g9_-45deg entering the half mirror 31 is reflected and becomes linearly polarized light L _-45deg and then passes through the linear polarizer 34

[0093] and enters the light receiver 14. Thus, when the transmission axis of the linear polarizer 35 is directed in the second direction, the light emitted from the light source 11 passes through the sample 100 eight times in total and enters the light receiver 14. Note that the above operations are the same when the angle θ is either of 45 degrees and ±135 degrees.According to the optical measuring instrument 1A described above, the polarization direction of the linear polarizer 35 is controlled, and the linear polarizer 35 can switch between transmitting or reflecting the linearly polarized light it receives. The number of times the light transmitted through the linear polarizer 35 passes through the sample 100 before reaching the receiver 14 is different from the number of times the light reflected by the linear polarizer 35 passes through the sample 100 before reaching the receiver 14. Therefore, by controlling the polarization direction of the linear polarizer 35, the optical path length passing through the sample 100 can be switched. Thus, unlike the case where the thickness of the sample 100 is changed by changing the thickness of the flow cell 10, the optical path length passing through the sample 100 can be switched while preventing changes in the pressure applied to the sample 100.

[0094] Furthermore, the reflective member 33 is equipped with three roof mirrors 330 arranged sequentially along the optical path. The first and second roof mirrors 330(1) and 330(2) each fold back the light that has passed through the sample 100 and transmit it back through the sample 100, causing it to incident on the next roof mirrors 330(2) and 330(3) in the optical path. The third roof mirror 330(3) transmits the emitted light back through the sample 100 and causes it to incident on the linear polarizer 35. Therefore, by causing light to be incident on the first roof mirror 330(1) via the sample 100, the light can be transmitted through the sample 100 four times and then incident on the linear polarizer 35.

[0095] Furthermore, since the linear polarizer 32 is positioned in the optical path between the light source 11 and the reflecting member 33, linearly polarized light from the light source 11, with the polarization direction being the same as the transmission axis of the linear polarizer 32, can be incident on the reflecting member 33.

[0096] Furthermore, a portion of the light emitted from the light source 11 passes through the half mirror 31 and is incident on the linear polarizer 32, guided into an optical path toward the linear polarizer 35. The light reflected by the linear polarizer 35 is further reflected by the reflecting member 33, passes through the linear polarizer 32 toward the light source 11, and is reflected by the half mirror 31 toward the photodetector 14. Therefore, the light that has passed through the sample 100 can be reliably incident on the photodetector 14.

[0097] Furthermore, the reflective member 33 maintains the polarization direction of the emitted light in the reference axis direction while reversing the polarization direction of the incident light in one direction (reverse direction), and the switching unit 36 ​​rotates the linear polarizer 35 so that it is oriented in a first direction that forms an angle (-θ) with respect to the reference axis direction, and in a second direction that forms an angle θ with respect to the reference axis direction. In addition, the transmission axes of the linear polarizer 32, which is positioned in the optical path between the light source 11 and the reflective member 33, and the reflective linear polarizer 34, which is positioned at an angle in the optical path between the half mirror 31 and the photodetector 14, and in the optical path between the linear polarizer 35 and the photodetector 14, each form an angle θ with respect to the reference axis direction.Therefore, by oriented the transmission axis of the linear polarizer 35 in the first direction, the light emitted from the light source 11 can be transmitted through the sample 100 four times before being incident on the photodetector 14. Furthermore, by orienting the transmission axis of the linear polarizer 35 in the second direction, the light emitted from the light source 11 can be transmitted through the sample 100 eight times before being incident on the photodetector 14. Therefore, by rotating the linear polarizer 35, the optical path length passing through the sample 100 can be switched.

[0098] Furthermore, since the transmission axis and reflection axis of the linear polarizer 35 and linear polarizer 34 are orthogonal to each other, and the angle θ of the transmission axis with respect to the reference axis axis is either ±45 degrees or ±135 degrees, when the transmission axis of the linear polarizer 35 is oriented in the first direction, linearly polarized light that passes through the linear polarizer 32 and heads from the reflecting member 33 to the linear polarizer 35 is reliably transmitted to the linear polarizer 35, reflected by the linear polarizer 34, and incident on the photodetector 14. Also, when the transmission axis of the linear polarizer 35 is oriented in the second direction, linearly polarized light that passes through the linear polarizer 32 and heads from the reflecting member 33 to the linear polarizer 35 is reliably reflected by the linear polarizer 35, passes through the sample 100, is further reflected by the reflecting member 33, then passes through the linear polarizer 32 and linear polarizer 34, and incident on the photodetector 14.

[0099] <Third Embodiment> (Configuration of Optical Measuring Instrument 1B) Figure 5 shows an optical measuring instrument 1B according to the third embodiment. The optical measuring instrument 1B includes an optical system 4.

[0100] ((Optical system 4)) The optical system 4 guides light from the light source 11 through the sample 100 to the photodetector 14. In this embodiment, the optical system 4 may have light incident perpendicularly to the sample 100. The optical system 4 includes a linear polarizer 41, a reflective member 42, a linear polarizer 43, an image rotator 44, and a switching unit 45. Of these, the linear polarizer 41 and a part of the reflective member 42 are arranged in the Z-axis direction together with the light source 11, while another part of the reflective member 42 and the linear polarizer 43 are arranged in the Z-axis direction parallel to these, together with the photodetector 14. The linear polarizer 41, the image rotator 44, and the linear polarizer 43 are arranged in the Y-axis direction. The linear polarizers 41 and 43 may be arranged with their optical surfaces facing each other in the reference axis direction (in this embodiment, for example, the X-axis direction) so that the internal angle is 90 degrees. The linear polarizers 41 and 43 may each be reflective polarizers.

[0101] (((Linear polarizer 41))) The linear polarizer 41 is an example of a fifth linear polarizer and is positioned in the optical path between the light source 11 and the reflecting member 42. The linear polarizer 41 may be positioned opposite a part of the reflecting member 42 with the sample 100 in between, and in this embodiment, as an example, it may be positioned opposite the roof mirror 420(1) of the reflecting member 42, described later, with the flow cell 10 containing the sample 100 in between. The linear polarizer 41 may be positioned at an angle to the optical axis between the light source 11 and the reflecting member 42, and in this embodiment, as an example, it may be positioned at a 45-degree angle to the Z-axis direction.

[0102] The linear polarizer 41 may have a transmission axis and a reflection axis. The transmission axis and reflection axis of the linear polarizer 41 may intersect each other, and in this embodiment, they are orthogonal as an example. In this embodiment, the linear polarizer 41 may be a wire grid polarizer as an example.

[0103] The linear polarizer 41 may transmit linearly polarized light from the light source 11, where the polarization direction is along the transmission axis of the linear polarizer 41, and guide it through the sample 100 to an optical path (also called a reference optical path) from the reflecting member 42 to the linear polarizer 43. The linear polarizer 41 may reflect and remove linearly polarized light from the light source 11, where the polarization direction is along the reflection axis.

[0104] The linear polarizer 41 may receive linearly polarized light that has passed through the sample 100, and in this embodiment, as an example, it may receive light that has passed through the sample 100 and been reflected by the linear polarizer 43. The linear polarizer 41 may further reflect the light reflected by the linear polarizer 43 and guide it to the above-mentioned reference optical path.

[0105] The linear polarizer 41 may be held by a holding member 410. The holding member 410 may hold the linear polarizer 41 so that it can rotate while maintaining its orientation.

[0106] (((Reflective member 42))) The reflective member 42 reflects the linearly polarized light that passes through the sample 100 in the opposite direction, transmits it back through the sample 100, and directs it onto the linear polarizer 43. In this embodiment, as an example, the reflective member 42 may receive light in the positive Z-axis direction and reflect light in the negative Z-axis direction.

[0107] Similar to the reflective member 33 in the second embodiment, the reflective member 42 may reverse the polarization direction of the light emitted from the reflective member 42 in at least one direction perpendicular to the optical axis direction (in this embodiment, for example, the Z axis direction) with respect to the polarization direction of the light incident on the reflective member 42. For example, the reflective member 42 may reverse the polarization direction of the emitted light in one direction perpendicular to the optical axis direction (in this embodiment, for example, the Y axis direction) with respect to the polarization direction of the incident light, and maintain it in the optical axis direction and a reference axis direction perpendicular to that one direction (in this embodiment, for example, the X axis direction).

[0108] The reflective member 42 may have at least one roof mirror 420 that reflects incident light twice and emits it in opposite directions. For example, it may have n roof mirrors 420 from the first to the nth (where n is an odd number of 3 or more) arranged in order along the optical path. Of these, the first to the (n-1)th roof mirrors 420 may fold back the light that has passed through the sample 100 and transmit it back through the sample 100 to the next roof mirror 420 in the optical path, while the nth roof mirror 420 may transmit the emitted light back through the sample 100 to the linear polarizer 43. In this embodiment, as an example, the reflective member 42 has a total of three roof mirrors 420 (also referred to as roof mirrors 420(1) to 420(3)) from the first to the third, similar to the reflective member 33 in the second embodiment described above. Of these, the odd-numbered first and third roof mirrors 420(1) and 420(3) may be positioned on the side of the flow cell 10 opposite to the light source 11, and may face the linear polarizers 41 and 43 with the sample 100 in between. The even-numbered second roof mirror 420(2) may be positioned on the side of the flow cell 10 toward the light source 11. Light emitted from the linear polarizer 41 and incident on the first roof mirror 420(1) may be emitted from the third roof mirror 420(3) and incident on the linear polarizer 43. Each roof mirror 420 may be formed with two reflective planes facing each other along the reference axis direction (in this embodiment, for example, the X-axis direction) so that the interior angle is 90 degrees, similar to the roof mirror 230 in the first embodiment. Each roof mirror 420 may be positioned spaced apart from the flow cell 10, in contact with the flow cell 10, or as part of the window member of the flow cell 10.

[0109] (((Linear polarizer 43))) The linear polarizer 43 is an example of a first linear polarizer and may be positioned opposite a part of the reflective member 42 with the sample 100 in between. In this embodiment, for example, it may be positioned opposite the roof mirror 420(3) on the reflective member 42 with the flow cell 10 containing the sample 100 in between. The linear polarizer 43 may be positioned at an angle to the optical axis between the reflective member 42 and the photodetector 14. In this embodiment, for example, it may be positioned at an angle of -45 degrees to the Z-axis.

[0110] The linear polarizer 43 may have a transmission axis and a reflection axis. The transmission axis and reflection axis of the linear polarizer 43 may intersect each other, and in this embodiment, they are orthogonal as an example. In this embodiment, the linear polarizer 43 may be a wire grid polarizer as an example.

[0111] The linear polarizer 43 may receive linearly polarized light that has passed through the sample 100. In this embodiment, for example, it may receive light that has been emitted from the reflecting member 42 and passed through the sample 100. The linear polarizer 43 may transmit linearly polarized light whose polarization direction is in the direction of the transmission axis and allow it to be incident on the light receiver 14, and may reflect linearly polarized light whose polarization direction is in the direction of the reflection axis and allow it to be incident on the linear polarizer 41 via the image rotator 44.

[0112] The linear polarizer 43 may be held by a holding member 430. The holding member 430 may hold the linear polarizer 43 so that it can rotate while maintaining its orientation.

[0113] (((Image Rotator 44))) The image rotator 44 is positioned on the optical path between the linear polarizers 41 and 43. The image rotator 44 maintains the polarization direction of the light emitted from the image rotator 44 in the direction of the reference axis (for example, the X axis in this embodiment) while reversing it in the direction of the optical axis (for example, the Y axis in this embodiment) and in a direction perpendicular to the reference axis (for example, the Z axis in this embodiment) with respect to the polarization direction of the light incident on the image rotator 44.

[0114] The image rotator 44 has two mirrors 441 and 443 positioned opposite to the linear polarizers 43 and 41, respectively, and a mirror 442 positioned opposite to each of these mirrors 441 and 443. The mirrors 441 and 443 may be positioned symmetrically with respect to the XZ plane, and their opposite surfaces may face each other across the reference axis direction (in this embodiment, for example, the X axis direction) such that the interior angle is 2α when the angle between the Y axis direction and the normal to the reflecting surface is α. Mirror 441 may be positioned with its reflecting surface facing the linear polarizer 43, and may reflect light incident from the linear polarizer 43 to mirror 441 and cause it to incident on mirror 442. Mirror 442 may be positioned perpendicular to the Z axis direction, and may reflect light incident from mirror 441 to mirror 442 and cause it to incident on mirror 443. Mirror 443 may be positioned with its reflective surface facing the linear polarizer 41, and may reflect light incident on mirror 443 from mirror 442 and direct it onto the linear polarizer 41. The image rotator 44 may have other configurations; for example, the image rotator 44 may have a dove prism instead of mirrors 441 and 443.

[0115] (((Switching section 45))) The switching unit 45 controls the polarization direction of the linear polarizers 41 and 43, switching between transmitting or reflecting the linearly polarized light received by the linear polarizers 41 and 43. As a result, the number of times the light transmitted through the linear polarizer 43 passes through the sample 100 before reaching the photodetector 14 may be different from the number of times the light reflected by the linear polarizer 43 passes through the sample 100 before reaching the photodetector 14.

[0116] The switching unit 45 may control the polarization direction by rotating each of the linear polarizers 41 and 43 while maintaining their orientation. The switching unit 45 may rotate the linear polarizer 41 via the holding member 410, and may rotate the linear polarizer 43 via the holding member 430. Note that in Figure 5, the connection between the switching unit 45 and the holding member 410 is omitted for the sake of simplicity in the illustration.

[0117] The switching unit 45 may direct the transmission axes of the linear polarizers 41 and 43 to a first direction parallel or perpendicular to the reference axis direction (in this embodiment, for example, the X axis direction), and to a second direction that is at the same angle with respect to the reference axis direction, but is neither parallel nor perpendicular to the reference axis direction. The second direction may be at an angle of ±45 degrees or ±135 degrees with respect to the reference axis direction, and in this embodiment, for example, it is -45 degrees.

[0118] ((action)) Next, the operation of the optical system 4 according to this embodiment will be described.

[0119] (((When the transmission axes of linear polarizers 41 and 43 are oriented in the first direction))) Figure 5 shows the optical path when the transmission axes of the linear polarizers 41 and 43 are oriented in the first direction. In this figure, the first direction is shown as the direction that is 0 degrees with respect to the X-axis. When the transmission axes of the linear polarizers 41 and 43 are oriented in the first direction, the unpolarized light L0 emitted from the light source 11 passes through the linear polarizer 41 _0deg It is incident on.

[0120] Although not shown in the diagram, the linear polarizer 41 _0deg Of the unpolarized light L0 incident on the element, the linear polarizer 41 _0deg The component of linearly polarized light whose polarization direction is the reflection axis direction (in this case, the direction perpendicular to the X-axis direction) is the linear polarizer 41 _0deg It is then reflected and removed.

[0121] Meanwhile, the linear polarizer 41 _0deg Of the unpolarized light L0 incident on the element, the linear polarizer 41 _0deg The linearly polarized component, with the transmission axis direction (in this case, the X-axis direction) as the polarization direction, is obtained by the linear polarizer 41 _0deg Linearly polarized light L passes through h1_0deg The light L passes through the sample 100 and enters the roof mirror 420(1). h1_0deg Each time the light is reflected by the roof mirrors 420(1) to 420(3), the polarization direction is reversed in the Y-axis direction, resulting in linearly polarized light L h2_0deg ,L h3_0deg ,Lh4_0deg As a result, it passes through sample 100, and the linear polarizer 43 _0deg It is incident on. Thus, in this embodiment, of the light emitted from the light source 11, linearly polarized light L has a first direction parallel to the reference axis as its polarization direction. h1_0deg Linear polarizer 41 _0deg And linearly polarized light L that passes through the sample 100 and is reflected by the reflective member 42, with the first direction being the polarization direction. h4_0deg Therefore, it is incident on the linear polarizer 43. _0deg Linearly polarized light L incident on it h4_0deg is a linear polarizer 43 _0deg The light passes through the sample 100 and enters the photodetector 14. Therefore, when the transmission axes of the linear polarizers 41 and 43 are oriented in the first direction, the light emitted from the light source 11 passes through the sample 100 and enters the photodetector 14 a total of four times. The above operation is the same even when the angle between the transmission axes of the linear polarizers 41 and 43 and the reference axis is ±180 degrees, ±90 degrees, and ±270 degrees.

[0122] (((When the transmission axes of linear polarizers 41 and 43 are oriented in the second direction))) Figure 6 shows the optical path when the transmission axes of the linear polarizers 41 and 43 are oriented in the second direction. When the transmission axes of the linear polarizers 41 and 43 are oriented in the second direction, the unpolarized light L0 emitted from the light source 11 passes through the linear polarizer 41 _-45deg It is incident on.

[0123] Although not shown in the diagram, the linear polarizer 41 _-45deg Of the unpolarized light L0 incident on the element, the linear polarizer 41 _-45deg The linearly polarized component whose polarization direction is the reflection axis direction (here, the direction that is 45 degrees with respect to the X-axis direction) is the linear polarizer 41 _-45deg It is then reflected and removed.

[0124] Meanwhile, the linear polarizer 41 _-45deg Of the unpolarized light L0 incident on the element, the linear polarizer 41 _-45deg The linearly polarized component, whose polarization direction is the transmission axis direction (here, the direction at -45 degrees to the X-axis direction), is obtained by the linear polarizer 41. _-45deg Linearly polarized light L passes throughi1_-45deg As a result, after passing through sample 100, the polarization direction is reversed in the Y-axis direction each time it is reflected by roof mirrors 420(1) to 420(3), resulting in linearly polarized light L i2_45deg ,L i3_-45deg ,L i4_45deg As a result, it passes through sample 100, and the linear polarizer 43 _-45deg It is incident on. In this embodiment, the optical path from linear polarizer 41 to linear polarizer 43 may be a reference optical path. Here, linearly polarized light L i4_45deg is a linear polarizer 43 _-45deg The direction of the reflection axis is defined as the polarization direction.

[0125] Therefore, the linear polarizer 43 _-45deg Linearly polarized light L incident on it i4_45deg is a linear polarizer 43 _-45deg The linearly polarized light L is reflected by the surface. i5_-45deg The projectile then enters the image rotator 44.

[0126] Linearly polarized light L incident on the image rotator 44 i5_-45deg The polarization direction is reversed in the Z-axis direction, resulting in linearly polarized light L i6_45deg The image is then emitted from the image rotator 44 and the linear polarizer 41 _-45deg It is incident on the light source. Here, linearly polarized light L i6_45deg is a linear polarizer 41 _-45deg The direction of the reflection axis is defined as the polarization direction.

[0127] Therefore, the linear polarizer 41 _-45deg Linearly polarized light L incident on it i6_45deg is a linear polarizer 41 _-45deg The linearly polarized light L is reflected by the surface. i7_45deg As a result, after passing through sample 100, the polarization direction is reversed in the Y-axis direction each time it is reflected by roof mirrors 420(1) to 420(3), resulting in linearly polarized light L i8_-45deg ,L i9_45deg ,L i10_-45deg As a result, it passes through sample 100, and the linear polarizer 43 _-45deg It is incident on the linear polarizer 41. _-45degThe light emitted from is then guided again to the reference optical path from linear polarizer 41 to linear polarizer 43. Here, linearly polarized light L i10_-45deg is a linear polarizer 43 _-45deg The transmission axis direction is defined as the polarization direction.

[0128] Therefore, the linear polarizer 43 _-45deg Linearly polarized light L incident on it i10_-45deg is a linear polarizer 43 _-45deg The light passes through the sample 100 and enters the photodetector 14. In this way, when the transmission axes of the linear polarizers 41 and 43 are oriented in the second direction, the light emitted from the light source 11 passes through the sample 100 and enters the photodetector 14 a total of eight times. Note that the above operation is the same even when the angle between the transmission axes of the linear polarizers 41 and 43 and the reference axis is 45 degrees, 135 degrees, or -135 degrees.

[0129] ((((light L i4 ~L i7 Polarization direction)))) Figure 7 shows light L i4_45deg This indicates the polarization direction of light L. i4_45deg The polarization direction may be at a 45-degree angle to the X-axis direction (i.e., the reference axis direction) in the XY coordinate system. In the figure, the polarization direction is indicated by a thick arrow. Furthermore, the angle of the polarization direction with respect to the X-axis direction may be a positive angle in the first and third quadrants of the coordinate plane, and a negative angle in the second and fourth quadrants.

[0130] Figure 8 shows light L i5_-45deg This indicates the polarization direction of light L. i5_-45deg The polarization direction may be at an angle of -45 degrees to the X-axis in the XZ coordinate system.

[0131] Figure 9 shows the light L i6_45deg This indicates the polarization direction of light L. i6_45deg The polarization direction may be at a 45-degree angle to the X-axis in the XZ coordinate system.

[0132] Figure 10 shows light L i7_45deg This indicates the polarization direction of light L. i7_45deg The polarization direction may be at a 45-degree angle to the X-axis in the XY coordinate system.

[0133] According to the optical measuring instrument 1B described above, the polarization direction of the linear polarizer 43 is controlled, and the linear polarizer 43 can switch between transmitting or reflecting the linearly polarized light it receives. The number of times the light transmitted through the linear polarizer 43 passes through the sample 100 before reaching the photodetector 14 is different from the number of times the light reflected by the linear polarizer 43 passes through the sample 100 before reaching the photodetector 14. Therefore, by controlling the polarization direction of the linear polarizer 43, the optical path length passing through the sample 100 can be switched. Thus, unlike the case where the thickness of the sample 100 is changed by changing the thickness of the flow cell 10, the optical path length passing through the sample 100 can be switched while preventing changes in the pressure applied to the sample 100.

[0134] Furthermore, the linear polarizer 41 transmits linearly polarized light from the light source 11, whose polarization direction is the same as the transmission axis of the linear polarizer 41, and guides it through the sample 100 to a reference optical path from the reflecting member 42 to the linear polarizer 43, and also reflects the light reflected by the linear polarizer 43 and guides it to the same reference optical path. In addition, the reflecting member 42 reverses the polarization direction of the light emitted from the reflecting member 42 in one direction perpendicular to the optical axis, with respect to the polarization direction of the light incident on the reflecting member 42, and maintains this in the optical axis direction and the reference axis direction perpendicular to that one direction. Furthermore, the switching unit 45 rotates the linear polarizers 41 and 43 respectively, orienting the transmission axes of the linear polarizers 41 and 43 to a first direction parallel or perpendicular to the reference axis and a second direction at the same angle with respect to the reference axis, respectively. Therefore, by orienting the transmission axes of the linear polarizers 41 and 43 in the first direction, the light emitted from the light source 11 can be transmitted through the sample 100 four times before being incident on the photodetector 14. Also, by orienting the transmission axes of the linear polarizers 41 and 43 in the second direction, the light emitted from the light source 11 can be transmitted through the sample 100 eight times before being incident on the photodetector 14. Thus, by rotating the linear polarizers 41 and 43, the optical path length passing through the sample 100 can be switched.

[0135] Furthermore, the transmission axis and reflection axis of the linear polarizer 43 and linear polarizer 41 are orthogonal to each other, and the second direction is at an angle of either ±45 degrees or ±135 degrees with respect to the reference axis direction. By orienting the transmission axes of the linear polarizers 41 and 43 in the second direction, linearly polarized light that passes through the linear polarizer 41 and heads from the reflecting member 42 towards the linear polarizer 43 is reliably reflected by the linear polarizers 41 and 43, guided back to the reference optical path, and then transmitted through the linear polarizer 43 and incident on the photodetector 14.

[0136] Furthermore, the linear polarizers 41 and 43 are arranged with their optical surfaces facing each other along the reference axis so that the internal angle is 90 degrees. The image rotator 44, positioned on the optical path between the linear polarizers 41 and 43, inverts the polarization direction of the emitted light in the direction perpendicular to the optical axis and the reference axis, while maintaining the polarization direction of the emitted light along the reference axis relative to the polarization direction of the incident light. Therefore, the polarization direction of the light incident from the linear polarizer 43 to the linear polarizer 41 is reversed, and the light can be reliably reflected from the linear polarizer 41 toward the reflecting member 42.

[0137] <Variation> In the first to third embodiments described above, the optical measuring instruments 1, 1A, and 1B were described as being equipped with a flow cell 10, but they do not necessarily need to be equipped with a flow cell 10. Also, although the sample 100 was described as a fluid, it may be a translucent solid.

[0138] Furthermore, although it has been explained that the light source 11 emits unpolarized light, it may also emit linearly polarized light. For example, the light source 11 may emit light whose polarization direction is the same as the transmission axis direction of the linear polarizers 22, 32, and 41.

[0139] Furthermore, although the reflective member 23 has been described as having a single roof mirror 230, it may have multiple roof mirrors 230. For example, the reflective member 23 may have n roof mirrors 330, numbered from the first to the nth (where n is an odd number of 3 or more), arranged sequentially along the optical path, similar to the reflective members 33 and 42. In this case, each of the first to the (n-1)th roof mirrors 230 may fold back the light transmitted through the sample 100 and transmit it back through the sample 100 before it is incident on the next roof mirror 230 in the optical path, while the nth roof mirror 230 may transmit the emitted light back through the sample 100 before it is incident on the linear polarizer 22.

[0140] Furthermore, although it has been explained that the reflective members 33 and 42 have three or more odd-numbered roof mirrors 330 and 420, they may also have a single roof mirror 330 or 420, similar to the reflective member 23.

[0141] Furthermore, although the reflective members 23, 33, and 42 were described as inverting the polarization direction of the emitted light in one direction perpendicular to the optical axis (for example, the Y-axis direction) with respect to the polarization direction of the incident light, they may also be inverted in multiple directions perpendicular to the optical axis. For example, the reflective member 33 may have multiple roof mirrors 330, and at least two of these roof mirrors 330 may be formed with two reflective planes facing each other across separate directions perpendicular to the optical axis. The same applies to the reflective members 23 and 42.

[0142] Furthermore, although the linear polarizers 24 and 32 were described as reflective polarizers, they may also be absorptive polarizers. In this case, the transmission axis and the absorption axis may be orthogonal to each other.

[0143] Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various modifications or improvements can be made to the above embodiments. It will be clear from the claims that such modified or improved forms may also be included in the technical scope of the present invention.

[0144] It should be noted that the execution order of operations, procedures, steps, and stages in the apparatus, systems, programs, and methods shown in the claims, specifications, and drawings is not explicitly stated as "before," "prior to," etc., and that these can be implemented in any order unless the output of a previous process is used in a later process. Even if the operation flow in the claims, specifications, and drawings is described using phrases such as "first," "next," etc. for convenience, it does not mean that it is essential to perform the operations in that order. [Explanation of Symbols]

[0145] 1,1A,1B Optical measuring instrument 2~4 Optical system 10 flow cells 11 Light source 14 Receiver 15 Arithmetic unit 21 Half Mirror 22 Linear polarizer 23 Reflective material 24 Linear polarizers 25 Switching section 31 Half Mirror 32 Linear polarizers 33 Reflective material 34 Linear polarizer 35 Linear polarizer 36 Switching section 41 Linear polarizer 42 Reflective material 43 Linear polarizer 44 Image Rotator 45 Switching section 100 samples 220 Retaining member 230 Roof Mirror 240 Retaining member 330 Roof Mirror 350 Retaining member 410 Retaining member 420 Roof Mirror 430 Retaining member 441 Miller 442 Miller 443 Miller

Claims

1. A reflective first linear polarizer that receives linearly polarized light transmitted through the sample, A switching unit controls the polarization direction of the first linear polarizer to switch whether to transmit or reflect the linearly polarized light received by the first linear polarizer, thereby switching the optical path of the light emitted from the first linear polarizer between an optical path toward the light receiver and an optical path that further transmits through the sample before toward the light receiver. Equipped with, An optical system in which the number of times light transmitted through the first linear polarizer passes through the sample before reaching the photodetector is different from the number of times light reflected by the first linear polarizer passes through the sample before reaching the photodetector.

2. The device further comprises a reflective member that reflects the linearly polarized light that passes through the sample and is incident on it in the opposite direction, transmits it back to the sample, and directs it onto the first linear polarizer. The optical system according to claim 1, wherein the reflecting member reverses the polarization direction of the light emitted from the reflecting member in at least one direction perpendicular to the optical axis direction with respect to the polarization direction of the light incident on the reflecting member.

3. The optical system according to claim 2, wherein the reflective member has at least one roof mirror that reflects incident light twice and emits it in opposite directions.

4. The reflective member comprises n roof mirrors, numbered from the first to the nth (where n is an odd number of 3 or more), arranged in order along the optical path. Of the n roof mirrors, each of the first to (n-1) roof mirrors reflects the light that has passed through the sample, transmits it back through the sample, and causes it to incident on the next roof mirror in the optical path. The optical system according to claim 3, wherein the nth of the n roof mirrors transmits the emitted light through the sample and causes it to be incident on the first linear polarizer.

5. The first linear polarizer is, The aforementioned sample is positioned opposite the reflective member, Of the light emitted from the light source, linearly polarized light whose polarization direction is the same as the transmission axis of the first linear polarizer is transmitted, passes through the sample, and is incident on the reflective member, The optical system according to claim 2, wherein the optical system receives light that has been reflected by the reflective member and transmitted through the sample.

6. The transmission axis and reflection axis of the first linear polarizer are orthogonal to each other. The reflective member reverses the polarization direction of the light emitted from the reflective member in a direction perpendicular to the optical axis direction with respect to the polarization direction of the light incident on the reflective member, and maintains this in the optical axis direction and a reference axis direction perpendicular to that direction. The optical system according to claim 5, wherein the switching unit rotates the first linear polarizer while maintaining its orientation so that the transmission axis is directed in a direction perpendicular to the reference axis direction and in a direction that forms an angle of ±45 degrees or ±135 degrees with respect to the reference axis direction.

7. A half-mirror that transmits a portion of the light emitted from the light source and directs it onto the first linear polarizer, and reflects a portion of the light from the first linear polarizer toward the light source toward the photodetector, The system comprises a second linear polarizer positioned in the optical path between the half mirror and the photodetector, The optical system according to claim 6, wherein the switching unit rotates the second linear polarizer while maintaining its orientation, so that the angle that the transmission axis of the second linear polarizer makes with respect to the reference axis direction matches the angle that the transmission axis of the first linear polarizer makes with respect to the reference axis direction.

8. The optical system according to claim 2, further comprising a third linear polarizer disposed in the optical path between the light source and the reflective member.

9. The system further includes a half-mirror that transmits a portion of the light emitted from the light source and directs it onto the third linear polarizer, and reflects a portion of the light from the third linear polarizer toward the light source toward the photodetector. The optical system according to claim 8, wherein the third linear polarizer transmits linearly polarized light that has been reflected by the first linear polarizer, transmitted through the sample, and further reflected by the reflective member and transmitted through the sample.

10. The system further comprises a reflective fourth linear polarizer positioned in the optical path between the half mirror and the photodetector, and in the optical path between the first linear polarizer and the photodetector. The reflective member reverses the polarization direction of the light emitted from the reflective member in a direction perpendicular to the optical axis direction with respect to the polarization direction of the light incident on the reflective member, and maintains this in the optical axis direction and a reference axis direction perpendicular to that direction. The transmission axes of the third linear polarizer and the fourth linear polarizer are at an angle θ other than ±90 degrees with respect to the reference axis direction. The optical system according to claim 9, wherein the switching unit rotates the first linear polarizer while maintaining its orientation, and directs the transmission axis of the first linear polarizer to a direction that makes an angle (-θ) with respect to the reference axis direction and a direction that makes an angle θ with respect to the reference axis direction.

11. The reflective member reverses the polarization direction of the light emitted from the reflective member in a direction perpendicular to the optical axis direction with respect to the polarization direction of the light incident on the reflective member, and maintains this in the optical axis direction and a reference axis direction perpendicular to that direction. The transmission axis of the third linear polarizer has an angle θ other than ±90 degrees with respect to the reference axis direction. The optical system according to claim 9, wherein the switching unit rotates the first linear polarizer while maintaining its orientation, and directs the transmission axis of the first linear polarizer to a direction that makes an angle (-θ) with respect to the reference axis direction and a direction that makes an angle θ with respect to the reference axis direction.

12. The transmission axis and reflection axis of the first linear polarizer and the fourth linear polarizer are orthogonal to each other. The optical system according to claim 10, wherein the angle θ is either ±45 degrees or ±135 degrees.

13. The fifth linear polarizer is a reflective type that transmits linearly polarized light from the light source, whose polarization direction is along the transmission axis, and guides it through the sample into an optical path from the reflective member toward the first linear polarizer, and also reflects the light reflected by the first linear polarizer and guides it toward the optical path. The reflective member reverses the polarization direction of the light emitted from the reflective member in a direction perpendicular to the optical axis direction with respect to the polarization direction of the light incident on the reflective member, and maintains this in the optical axis direction and a reference axis direction perpendicular to that direction. The optical system according to claim 2, wherein the switching unit rotates the first linear polarizer and the fifth linear polarizer while maintaining their orientation, and directs the transmission axes of the first linear polarizer and the fifth linear polarizer to a first direction parallel or perpendicular to the reference axis direction and a second direction that is at the same angle with respect to the reference axis direction and is not parallel or perpendicular to the reference axis direction.

14. The transmission axis and reflection axis of the first linear polarizer and the fifth linear polarizer are orthogonal to each other. The optical system according to claim 13, wherein the second direction is at an angle of ±45 degrees or ±135 degrees with respect to the reference axis direction.

15. The first linear polarizer and the fifth linear polarizer are arranged with their optical surfaces facing each other in the direction of the reference axis such that the internal angle is 90 degrees. The optical system further comprises an image rotator positioned in the optical path between the first linear polarizer and the fifth linear polarizer, The optical system according to claim 14, wherein the image rotator reverses the polarization direction of the light emitted from the image rotator in the direction perpendicular to the optical axis and the reference axis, while maintaining the polarization direction of the light emitted from the image rotator in the direction of the reference axis, with respect to the polarization direction of the light incident on the image rotator.

16. The optical system according to claim 1, wherein light is incident perpendicularly on the sample.

17. The optical system according to claim 1, wherein the first linear polarizer is a wire grid polarizer.

18. The optical system according to claim 1, The optical system includes a light source that emits light, A photodetector that receives light emitted from the optical system, An optical measuring instrument equipped with the following features.

19. The optical measuring instrument according to claim 18, wherein the sample is a fluid flowing in a light-transmitting flow cell.

Images