Optical analyzer

Abstract

To change an optical path length with a simple configuration.SOLUTION: An optical analyzer comprises: a light source 3 that emits light L1 with which a cell 2 accommodating a sample is irradiated; a plurality of reflecting parts 4 that reflect the light from the light source 3 multiple times in the cell 2; a photodetector 5 that detects light L2 reflected multiple times by the plurality of reflecting parts 4 and output from the cell 2; and an optical path length changing mechanism 7 that changes the incident angle of the light L1 from the light source 3 relative to the plurality of reflecting parts 4 to change the number of times of reflection by the plurality of reflecting parts 4 and change an optical path length. The optical path length changing mechanism 7 has an incident-side condensation part 71, and changes the incident position or the incident angle of the light L1 from the light source 3 relative to the incident-side condensation part 71 to change the incident angle of the light L1 from the light source 3 relative to the plurality of reflecting parts 4.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an optical analysis device.

Background Art

[0002] Conventionally, as an optical analysis device, as shown in Patent Document 1, there has been considered one that changes the incident angle of laser light with respect to the incident hole of a multiple reflection cell to adjust the optical path length of the laser light in the multiple reflection cell. Specifically, in this device, the attitude, position, etc. of a light source, an angle-variable mirror, or a multiple reflection cell are adjusted by a driving device to change the incident angle of the laser light with respect to the incident hole of the multiple reflection cell.

[0003] However, when adjusting the light source or the multiple reflection cell, it is necessary to rotate the light source or the multiple reflection cell. Further, when adjusting the angle-variable mirror, it is necessary to adjust its position while rotating the angle-variable mirror, and in some cases, adjustments such as rotating the light source or the multiple reflection cell are also required along with the adjustment of the angle-variable mirror. Thus, in the above device, not only does the driving device for the light source, the angle-variable mirror, or the multiple reflection cell for adjusting the optical path length of the laser light in the multiple reflection cell become large-scale, but also the adjustment work for changing the incident angle becomes complicated.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Therefore, the present invention has been made in view of the above-described problems, and its main problem is to change the optical path length with a simple configuration.

Means for Solving the Problems

[0006] That is, the optical analysis apparatus according to the present invention includes a light source that emits light irradiated onto a cell containing a sample, a plurality of reflecting portions that reflect the light from the light source a plurality of times in the cell, a photodetector that detects the light that has been reflected a plurality of times by the plurality of reflecting portions and exits the cell, and an optical path length changing mechanism that changes the number of reflections by the plurality of reflecting portions and thus changes the optical path length by changing the incident angle of the light from the light source with respect to the plurality of reflecting portions. The optical path length changing mechanism has an incident-side condenser, and is characterized in that the incident angle of the light from the light source with respect to the plurality of reflecting portions is changed by changing the incident position or incident angle of the light from the light source with respect to the incident-side condenser.

[0007] With such an optical analysis apparatus, by changing the incident position or incident angle of the light from the light source with respect to the incident-side condenser, the number of reflections by the plurality of reflecting portions can be changed to change the optical path length, so that the optical path length can be changed with a simple configuration. As a result, when the sample has a low concentration, the concentration of the sample can be accurately measured by increasing the optical path length. In particular, if the configuration is such that the incident position of the light from the light source with respect to the incident-side condenser is changed, it becomes possible by linearly moving the incident-side condenser or other optical systems, eliminating the need for a rotation mechanism and enabling a simple configuration.

[0008] The optical path length changing mechanism further has a reflecting member that reflects the light from the light source toward the incident-side condenser, and it is desirable to change the incident position or incident angle of the light from the light source with respect to the incident-side condenser by moving the reflecting member. With this configuration, the incident position or incident angle of the light from the light source with respect to the incident-side condenser can be changed without moving the light source, so that the configuration for changing the optical path length can be simplified.

[0009] When the incident position or incident angle to the incident-side condenser is changed by the reflecting member, the incident position of light with respect to the plurality of reflecting portions or cells changes. In order to adjust the incident position of light with respect to the plurality of reflecting portions, it is desirable that the optical path length changing mechanism further includes an adjusting portion that adjusts the distance between the incident-side condenser and the plurality of reflecting portions in accordance with the movement of the reflecting member. With this configuration, since the incident position of light with respect to the plurality of reflecting portions or cells can be adjusted, the optical windows formed in the reflecting portions or measurement cells can be made common.

[0010] It is desirable that the optical path length changing mechanism further includes an exit-side condenser. With this configuration, since the light emitted from the cell can be made parallel to the light incident on the plurality of reflecting portions, even when the optical path length is changed, the rotation of the detection optical system such as a photodetector can be made unnecessary.

[0011] In order to simplify the optical configuration of the optical path length changing mechanism, it is desirable that the incident-side condenser and the exit-side condenser are constituted by a common condenser element.

[0012] It is desirable that the reflecting member has an incident-side reflecting surface that reflects the light from the light source toward the incident-side condenser, and an exit-side reflecting surface that reflects the light condensed by the exit-side condenser toward the photodetector. Here, it is desirable that the incident-side reflecting surface and the exit-side reflecting surface are arranged at right angles. With this configuration, the optical path length can be changed while the positions of the light source and the photodetector are fixed. For example, in the case of a reflecting member in which the incident-side reflecting surface and the exit-side reflecting surface are arranged at right angles, the optical path of the light from the light source and the optical path of the light incident on the photodetector are arranged on the same straight line, and the reflecting member is linearly moved in a direction perpendicular to the optical path, whereby the optical path length can be changed.

[0013] In order to expand the range of changeable incident angles with respect to the plurality of reflecting portions and thus expand the range of changeable number of reflections by the plurality of reflecting portions, that is, the range of changeable optical path length, it is desirable that the incident-side condenser be a combined lens.

[0014] It is desirable that the plurality of reflecting portions have planar reflecting surfaces. If it has a planar reflecting surface in this way, a reflecting member with good reflectivity can be used even for light in the ultraviolet region or the like, and the optical analysis apparatus of the present invention can be suitably used for ultraviolet absorption spectroscopy.

[0015] Further, in the optical analysis apparatus of the present invention, it is desirable that the cell be light-transmissive and contain a liquid sample, and further include a concentration calculation unit that calculates the concentration of the liquid sample based on the absorbance of the light detected by the photodetector. With this configuration, even for a trace component (for example, on the order of ppb) in a liquid sample, sufficient absorbance for concentration calculation can be obtained, and the concentration of the trace component can be measured.

Advantages of the Invention

[0016] According to the present invention described above, by changing the incident position or incident angle of the light from the light source with respect to the incident-side condenser, the number of reflections by the plurality of reflecting portions can be changed to change the optical path length. Therefore, the optical path length can be changed with a simple configuration.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

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Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0018] <One Embodiment of the Present Invention> Hereinafter, an embodiment of an optical analyzer according to the present invention will be described with reference to the drawings. Note that, for all the figures shown below, for the sake of clarity, they are schematically drawn with appropriate omissions or exaggerations. For the same components, the same reference numerals are given and the description is omitted as appropriate.

[0019] <Basic Configuration of the Optical Analyzer 100> The optical analyzer 100 of the present embodiment is an absorption analyzer that measures the concentration of components contained in a liquid sample such as water. The optical analyzer 100 of the present embodiment uses ultraviolet absorption spectroscopy, but it may use other absorption spectroscopy methods.

[0020] Specifically, as shown in FIG. 1, the optical analyzer 100 includes a light source 3 that emits light irradiated to a cell 2 containing a liquid sample, a plurality of reflecting portions 4 that reflect the light from the light source 3 a plurality of times in the cell 2, a photodetector 5 that detects the light that has been reflected a plurality of times by the plurality of reflecting portions 4 and exits from the cell 2, and a concentration calculation unit 6 that calculates the concentration of the liquid sample based on the absorbance of the light detected by the photodetector 5.

[0021] In the present embodiment, as the plurality of reflecting portions 4, there are two reflecting mirrors 4a and 4b, and the light from the light source 3 is reflected a plurality of times between the two reflecting mirrors 4a and 4b. Both of these two reflecting mirrors 4a and 4b have planar reflecting surfaces, and these reflecting surfaces are arranged so as to face each other. The cell 2 is installed between these two reflecting mirrors 4a and 4b.

[0022] Further, the light source 3 may be a light source element such as an LED or a laser that irradiates light of a specific wavelength, or may be configured to irradiate light including a specific wavelength after being split by a spectroscope. Similarly, the photodetector 5 may be a detection element that detects light of a specific wavelength, or may be configured to detect light of a specific wavelength split by a spectroscope.

[0023] The concentration calculation unit 6 calculates the absorbance of the liquid sample based on the light intensity signal obtained by the photodetector 5, and calculates the concentration of the component based on the absorbance.

[0024] Here, the component concentration of the liquid sample can be obtained from the Lambert-Beer's formula shown below.

[0025]

Equation

[0026] However, depending on the components of the liquid sample, there are some with a small extinction coefficient ε, and there are some where sufficient light absorption cannot be observed near the target concentration. Then, as shown in FIG. 2, at low absorbance, there is no significant light intensity difference between the incident light and the outgoing light, and the concentration may not be accurately measured.

[0027] <Optical path length changing mechanism 7> Therefore, the optical analyzer 100 of the present embodiment is configured to be able to accurately measure the concentration even for components with a small extinction coefficient ε by changing the optical path length.

[0028] That is, as shown in FIG. 1, the optical analysis apparatus 100 includes an optical path length changing mechanism 7 that changes the number of reflections by the plurality of reflection parts 4 by changing the incident angle of the light from the light source 3 with respect to the plurality of reflection parts 4, thereby changing the optical path length. The optical path length changing mechanism 7 of the present embodiment changes the optical path length without changing the positions and postures of the light source 3 and the photodetector 5.

[0029] Specifically, the optical path length changing mechanism 7 has an incident side condenser 71, and changes the incident angle of the light from the light source 3 with respect to the plurality of reflection parts 4 by changing the incident position or incident angle of the light L1 from the light source 3 with respect to the incident side condenser 71. Further, the optical path length changing mechanism 7 has an exit side condenser 72.

[0030] The incident side condenser 71 is composed of a convex lens as a condensing element, and the incident position or incident angle of the light L1 from the light source is changed at a position away from the optical axis Lx of the convex lens.

[0031] The exit side condenser 72 is, like the incident side condenser 71, composed of a convex lens as a condensing element, and is configured such that the light L2 exiting from the cell 2 is incident at a position away from the optical axis Lx of the convex lens.

[0032] Here, the incident side condenser 71 and the exit side condenser 72 are composed of a convex lens as a common condensing element, and in the common convex lens, the position where the light L1 from the light source 3 is incident and the position where the light L2 exiting from the cell 2 is incident are configured to be symmetric positions with respect to the optical axis Lx of the convex lens. Here, as the convex lens, a biconvex lens, a plano-convex lens, a convex meniscus lens, or the like can be used.

[0033] Further, the optical path length changing mechanism 7 further has a reflecting member 73 that reflects the light from the light source 3 toward the incident side condenser 71. In the present embodiment, the reflecting member 73 includes a first reflecting member 73a and a second reflecting member 73b.

[0034] The first reflecting member 73a and the second reflecting member 73b not only reflect the light L1 from the light source 3 toward the incident-side condenser 71, but also reflect the light L2 emitted from the cell 2 toward the photodetector 5.

[0035] Specifically, the first reflecting member 73a has an incident-side reflecting surface 73a1 that reflects the light L1 from the light source 3 toward the incident-side condenser 71, and an exit-side reflecting surface 73a2 that reflects the light condensed by the exit-side condenser 72 toward the photodetector 5. Here, both the incident-side reflecting surface 73a1 and the exit-side reflecting surface 73a2 have planar reflecting surfaces, and they are arranged perpendicular to each other. The first reflecting member 73a of the present embodiment is a triangular prism. By this first reflecting member 73a, the optical path from the light source 3 incident on the first reflecting member 73a and the optical path exiting from the first reflecting member 73a to the photodetector 5 can be positioned on the same straight line. Also, the incident angle of the light L1 with respect to the incident-side reflecting surface 73a1 of this first reflecting member 73a is 45 degrees. Also, the incident angle of the light condensed by the exit-side condenser 72 with respect to the exit-side reflecting surface 73a2 is 45 degrees.

[0036] The second reflecting member 73b is provided intervening between the first reflecting member 73a, the incident-side condenser 71, and the exit-side condenser 72. The second reflecting member 73b of the present embodiment has a planar reflecting surface, reflects the light L1 reflected by the first reflecting member 73a toward the incident-side condenser 71, and reflects the light L2 condensed by the exit-side condenser 72 toward the first reflecting member 73a.

[0037] In the present embodiment, both the first reflecting member 73a and the second reflecting member 73b are arranged so as to reflect light at a right angle.

[0038] By linearly moving the first reflecting member 73a, the incident position of the light L1 with respect to the incident-side condenser 71 can be changed. Specifically, as shown in FIGS. 3 and 4, the first reflecting member 73a can change the incident position of the light L1 with respect to the incident-side condenser 71 by moving forward and backward with respect to the second reflecting member 73b. Note that the first reflecting member 73a can be moved by a guide mechanism (not shown) that moves linearly.

[0039] Further, the optical path length changing mechanism 7 further includes an adjusting unit 74 that adjusts the distance between the incident-side condenser 71 and the plurality of reflecting units 4 (or cells 2) in accordance with the movement of the first reflecting member 73a. Note that the adjusting unit 74 uses a guide mechanism that linearly moves the convex lens that is the incident-side condenser 71.

[0040] <Method for Changing Optical Path Length> Next, a method for changing the optical path length using the optical path length changing mechanism 7 will be described with reference to FIGS. 3 and 4.

[0041] As shown in FIG. 3, the first reflecting member 73a is moved in a direction approaching the second reflecting member 73b (downward in FIG. 3). Then, the light L1 from the light source 3 is reflected by the first reflecting member 73a and the second reflecting member 73b, and the incident position with respect to the incident-side condenser 71 moves in a direction away from the optical axis Lx. As a result, the light L1 is refracted by the incident-side condenser 71 toward the focal point, and the incident angle with respect to the reflecting unit 4 (mirror 4a) is changed in a direction of increasing. When the incident angle with respect to the reflecting unit 4 (mirror 4a) increases, the number of reflections by the plurality of reflecting units 4 decreases, and the optical path length becomes shorter.

[0042] Then, the light L1 reflected a plurality of times by the plurality of reflecting units 4 enters the exit-side condenser 72 after passing through the cell 2. The light L2 that has entered the exit-side condenser 72 is refracted by the exit-side condenser 72 and becomes parallel to the light L1 before entering the incident-side condenser 71. This light L2 is reflected by the second reflecting member 73b and the first reflecting member 73a and detected by the photodetector 4.

[0043] On the other hand, as shown in FIG. 4, the first reflecting member 73a is moved in a direction away from the second reflecting member 73b (upward in FIG. 4). Then, the light L1 from the light source 3 is reflected by the first reflecting member 73a and the second reflecting member 73b, and the incident position with respect to the incident-side condenser 71 moves in a direction approaching the optical axis Lx. As a result, the light L1 is refracted by the incident-side condenser 71 toward the focal point, and the incident angle with respect to the reflecting portion 4 (reflecting mirror 4a) is changed in a direction of decreasing. When the incident angle with respect to the reflecting portion 4 (reflecting mirror 4a) decreases, the number of reflections by the plurality of reflecting portions 4 increases, and the optical path length becomes longer.

[0044] Then, the light L1 reflected a plurality of times by the reflecting portion 4 enters the exit-side condenser 72 after passing through the cell 2. The light L2 incident on the exit-side condenser 72 is refracted by the exit-side condenser 72 and becomes parallel to the light L1 before entering the incident-side condenser 71. This light L2 is reflected by the second reflecting member 73b and the first reflecting member 73a and detected by the photodetector 4. The optical path of the light L2 after being reflected by the first reflecting member 73a is the same before and after the change in the optical path length.

[0045] By changing the incident angle by the incident-side condenser 71 as described above, since the incident position of the light with respect to the reflecting portion 4 (reflecting mirror 4a) changes, the adjustment unit 74 adjusts the distance of the incident-side condenser 671 with respect to the reflecting portion 4 (reflecting mirror 4a) according to the movement of the first reflecting member 73a. Thereby, an optical window (not shown) formed in the reflecting portion 4 or the cell 2 or the like can be made common.

[0046] <Effects of the present embodiment> According to the analyzer 100 of the present embodiment configured as described above, by changing the incident position of the light L1 from the light source 3 with respect to the incident-side condenser 71, the number of reflections by the plurality of reflecting portions 4 can be changed to change the optical path length. Therefore, the optical path length can be changed with a simple configuration. As a result, when the sample has a low concentration, the concentration of the sample can be accurately measured by increasing the optical path length. Particularly, since it is configured to change the incident position of the light L1 from the light source 3 with respect to the incident-side condensing unit 71, it can be achieved by the linear driving of the incident-side condensing unit 71 or other optical systems (in this embodiment, the first reflecting member 73a), eliminating the need for a rotation mechanism and enabling a simple configuration.

[0047] <Other Embodiments> For example, in the above embodiment, the incident-side condensing unit 71 and the exit-side condensing unit 72 are constituted by a single convex lens. However, as shown in FIG. 5, the incident-side condensing unit 71 and the exit-side condensing unit 72 may be a combination of two or more lenses. In this case, by changing the distance between the combination lenses, the incident angle with respect to the reflecting unit 4 can be changed. For example, when constituted by two combination lenses, the incident angle with respect to the reflecting unit 4 can be changed by moving the lens on the cell 2 side.

[0048] Also, when the incident-side condensing unit 71 and the exit-side condensing unit 72 are constituted by separate condensing elements, at least one of the incident-side condensing unit 71 or the exit-side condensing unit 72 may be a combination of two or more lenses.

[0049] When using a combination lens in the incident-side condensing unit 71, at this time, the configuration is such that the incident angle of the light L1 with respect to the lens (condensing element) on the reflecting unit 4 side in the combination lens is changed.

[0050] In addition to changing the incident angle of the light L1 with respect to the lens (condensing element) on the reflecting unit side by the combination lens, a configuration may be adopted in which another optical element is used to change the incident angle of the light L1 with respect to the condensing element that is the incident-side condensing unit 71.

[0051] Furthermore, although the condensing element in the above embodiment is constituted by a convex lens, other condensing elements such as a condensing mirror may be used, or a combination of different condensing elements may be used.

[0052] Furthermore, in the above embodiment, the configuration includes the light collecting unit 72 on the emission side. However, it may also be configured without the light collecting unit 72 on the emission side. In this case, the light L2 emitted from the cell 2 may be directly detected by the photodetector 5, or the light L2 emitted from the cell 2 may be reflected by a reflecting member and then detected by the photodetector 5.

[0053] In addition, in the above embodiment, the first reflecting member 73a and the second reflecting member 73b are configured to reflect the light L1 from the light source 3 and the light L2 emitted from the cell. However, different reflecting members may be provided for the light L1 from the light source 3 and the light L2 emitted from the cell 2 respectively. Also, in the above embodiment, as shown in FIG. 6, it may be configured without the second reflecting member 73b.

[0054] In the above embodiment, a plurality of reflecting portions 4 are provided outside the cell 2. However, it may also be configured to provide a plurality of reflecting portions 4 inside the cell 2. Also, the inner wall surface or the outer wall surface of the cell 2 may be mirror-finished so that the inner wall surface or the outer wall surface of the cell 2 serves as the reflecting portion 4.

[0055] Also, in the above embodiment, it may be configured without the reflecting member 73. In this case, as shown in FIG. 7, the light source 3 may be linearly moved with respect to the light collecting unit 71 on the incident side to change the incident position or the incident angle. Also, in this case, the photodetector 5 is linearly moved with respect to the light collecting unit 72 on the emission side.

[0056] The sample in the above embodiment was a liquid, but the sample of the present invention may be a solid or a gas, and can be applied as long as it transmits incident light.

[0057] Furthermore, in addition to the configuration of the above embodiment, based on the light intensity signal obtained by the photodetector 5 or the concentration C obtained by the concentration calculation unit 6, the optical path length changing mechanism 7 may be automatically moved to change to an optimal optical path length. In this case, it is conceivable to configure to automatically move the first reflecting member 73 or the convex lenses of the light collecting unit 71 on the incident side and the light collecting unit 72 on the emission side based on the light intensity signal or the concentration C.

[0058] In addition, various modifications and combinations of the embodiments may be made as long as they do not depart from the spirit of the present invention.

Description of Reference Numerals

[0059] 100 ··· Optical analyzer 2 ··· Cell 3 ··· Light source 4(4a, 4b) ··· Reflecting part (mirror) 5 ··· Photodetector 6 ··· Concentration calculation unit 7 ··· Optical path length changing mechanism 71 ··· Incident side condensing part 72 ··· Exit side condensing part 73 ··· Reflecting member 74 ··· Adjusting part 73a1 ··· Incident side reflecting surface 73a2 ··· Exit side reflecting surface

Claims

1. A light source that emits light irradiated onto a cell containing a sample, A plurality of reflecting portions that reflect the light from the light source a plurality of times in the cell, A photodetector that detects the light that has been reflected a plurality of times by the plurality of reflecting portions and has exited the cell, An optical path length changing mechanism that changes the number of reflections by the plurality of reflecting portions and changes the optical path length by changing the incident angle of the light from the light source with respect to the plurality of reflecting portions, The optical path length changing mechanism has an incident side condenser, and changes the incident angle of the light from the light source with respect to the plurality of reflecting portions by changing the incident position or incident angle of the light from the light source with respect to the incident side condenser, an optical analysis device.

2. The optical path length changing mechanism further has a reflecting member that reflects the light from the light source toward the incident side condenser, and changes the incident position or incident angle of the light from the light source with respect to the incident side condenser by moving the reflecting member, the optical analysis device according to claim 1.

3. The optical path length changing mechanism further has an adjusting portion that adjusts the distance of the incident side condenser with respect to the plurality of reflecting portions in accordance with the movement of the reflecting member, the optical analysis device according to claim 2.

4. The optical path length changing mechanism further has an exit side condenser, the optical analysis device according to any one of claims 1 to 3.

5. The incident side condenser and the exit side condenser are constituted by a common condenser element, the optical analysis device according to claim 4.

6. The reflecting member, An incident side reflecting surface that reflects the light from the light source toward the incident side condenser, And an exit side reflecting surface that reflects the light condensed by the exit side condenser toward the photodetector, the optical analysis device according to claim 4 or 5.

7. The optical analysis device according to any one of claims 1 to 6, wherein the incident-side light condensing unit is a combined lens.

8. The optical analysis device according to any one of claims 1 to 7, wherein the plurality of reflecting portions have planar reflecting surfaces.

9. The cell has light transmissivity for accommodating a liquid sample, The optical analysis device according to any one of claims 1 to 8, further comprising a concentration calculation unit that calculates the concentration of the liquid sample based on the absorbance of the light detected by the photodetector.

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