JP4839845B2 - Spectrometer - Google Patents

Description

  The present invention relates to a spectroscopic device that splits light to be measured using a wavelength dispersion element such as a diffraction grating.

  2. Description of the Related Art Conventionally, a double-pass spectroscopic device has been developed that improves the resolution and expands the dynamic range by reciprocating light to be measured with respect to a wavelength dispersion element. FIG. 10 is a perspective view showing the configuration of a conventional double-pass spectroscopic device. The spectroscopic device shown in FIG. 10 is a double-pass spectroscopic device having a Czerny-Turner type optical system. As shown in FIG. 10, the spectroscopic device 100 includes an entrance slit 101, a concave mirror 102, a diffraction grating 103, a concave mirror 104, a reflection optical system 105, and an exit slit 106.

  The light to be measured that has entered the spectroscopic device 100 travels back and forth within the spectroscopic device 100 and is emitted to the outside. In other words, the measured light incident from the entrance slit 101 enters the reflective optical system 105 sequentially through the concave mirror 102, the diffraction grating 103, and the concave mirror 104 in the forward path, and is measured from the reflective optical system 105 in the backward path. Light is emitted from the exit slit 106 through the concave mirror 104, the diffraction grating 103, and the concave mirror 102 in this order.

  The entrance slit 101 limits the intensity of the light to be measured that enters the spectroscopic device 100. The concave mirror 102 converts the light to be measured traveling from the entrance slit 101 and traveling along the forward path into parallel light and enters the diffraction grating 103, and condenses the light to be measured that travels the backward path diffracted by the diffraction grating 103 onto the exit slit 106. To do. The diffraction grating 103 has a diffractive surface 103a in which a large number of grooves are formed, and diffracts parallel light traveling on the forward path from the concave mirror 102 and parallel light traveling on the return path from the concave mirror 104 at different angles for each wavelength.

  The diffraction grating 103 is configured to be rotatable around a rotation axis RX included in the diffraction surface 103a. This makes it possible to vary the wavelength of the measured light that travels in the forward path diffracted by the diffraction grating 103 and enters the concave mirror 104 and the measured light that travels in the backward path diffracted by the diffraction grating 103 and incident on the concave mirror 102. Can do.

  The concave mirror 104 condenses only the light to be measured incident on the concave mirror 104 out of the light to be measured diffracted by the diffraction grating 103 on the reflection optical system 105 and also returns the return path emitted from the reflection optical system 105. The traveling light to be measured is converted into parallel light and is incident on the diffraction grating 103. The reflective optical system 105 makes the dispersion direction of the light to be measured from the concave mirror 104 reverse (inverted) and makes it incident on the concave mirror 104 again. The exit slit 106 limits the wavelength band of the light to be measured that travels on the return path collected by the concave mirror 102.

  Next, the reflection optical system 105 will be described. 11 is an enlarged perspective view of the reflective optical system 105, and FIG. 12 is a plan view of the reflective optical system 105. As shown in FIG. As shown in FIGS. 11 and 12, the reflection optical system 105 includes a first plane mirror 110, a second plane mirror 111, a third plane mirror 112, an intermediate slit 113, a reflector 114, and a fourth plane mirror 115. Then, the light to be measured incident on the reflection optical system 105 is emitted from the reflection optical system 105 through these optical members in order.

  As shown in FIG. 12, when the reflective optical system 105 is viewed in a plan view, the reflective optical system 105 is configured substantially symmetrically. That is, when the reflection optical system 105 is viewed in plan, the intermediate slit 113 is disposed on the extension line of the optical axis OX of the light to be measured reflected by the first plane mirror 110 (fourth plane mirror 115), and The second plane mirror 111 and the fourth plane mirror 115 are arranged symmetrically with respect to the optical axis OX, and the third plane mirror 112 and the reflector 114 are arranged symmetrically with respect to the optical axis OX. In the reflection optical system 105, each optical member is arranged so that the focal position of the concave mirror 104 shown in FIG. The reflector 114 is provided to shift (shift) the optical path of the light to be measured that has passed through the intermediate slit 113 upward.

  The reflection optical system 105 having the above configuration reverses the dispersion direction of the light to be measured from the concave mirror 104. Here, as shown in FIG. 11 and FIG. 12, the dispersion direction of the light to be measured incident from the concave mirror 104 to the reflective optical system 105 is indicated by an arrow with a symbol D11. Here, it is assumed that the tip side of the arrow labeled D11 has a short wavelength and the base side of the arrow has a long wavelength. When this light to be measured enters the reflection optical system 105, it is sequentially reflected by the first plane mirror 110, the second plane mirror 111, and the third plane mirror 112 and then enters the intermediate slit 113. Here, the wavelength of light to be measured is selected according to the slit width of the intermediate slit 113.

  The light to be measured that has passed through the intermediate slit 113 is reflected upward by the reflector 114, is then reflected by the fourth flat mirror 115 and the first flat mirror 110, and is emitted from the reflective optical system 105. Here, the dispersion direction of the light to be measured emitted from the reflection optical system 105 is opposite to the dispersion direction of the light to be measured incident on the reflection optical system 105 as indicated by an arrow with a symbol D12. By making the dispersion direction of the measurement light traveling in the backward path opposite to the dispersion direction of the measurement light traveling in the forward path by the reflection optical system 105, the measurement light traveling in the backward path is further diffracted by the diffraction grating 103. The resolution of the wavelength can be improved.

  Next, another example of a conventional spectroscopic device will be described. FIG. 13 is a perspective view showing another configuration of a conventional double-pass spectroscopic device. In FIG. 13, the same reference numerals are given to the components corresponding to those shown in FIG. 10, and description thereof will be omitted. A spectroscopic device 120 illustrated in FIG. 13 includes a reflective optical system 125 instead of the reflective optical system 105 included in the spectroscopic device 100 illustrated in FIG. 10. Similar to the reflective optical system 105, the reflective optical system 125 reverses the dispersion direction of the light to be measured from the concave mirror 104.

  FIG. 14 is an enlarged perspective view of the reflective optical system 125. As shown in FIG. 14, the reflective optical system 125 includes a slit 131, a lens group 132, and a plane mirror 133. The slit 131 and the plane mirror 133 are arranged so that the centers thereof are located on the optical axis of the lens group 132. The slit 131 is disposed at the focal position of the concave mirror 104. The slit 131 is arranged so that the light to be measured from the concave mirror 104 is condensed at the lower part of the slit opening. The lens group 132 converts the light to be measured via the slit 131 into parallel light and condenses the parallel light reflected by the plane mirror 133 on the slit 131. The plane mirror 133 reflects the parallel light from the lens group 132 and makes it incident on the lens group 132.

  In the above configuration, of the light to be measured collected at the lower portion of the slit opening of the slit 131, the light to be measured that has passed through the slit 131 passes through a portion below the optical axis of the lens group 132 and passes through the lens group. 132 is emitted as parallel light. Here, the parallel light emitted from the lens group 132 is emitted upward at an angle. The parallel light emitted from the lens group 132 is reflected upward by the plane mirror 133, enters the upper part of the lens group 132, passes through a portion above the optical axis of the lens group 132, and is emitted from the lens group 132. The light is condensed on the upper part of the slit opening of the slit 131. In the reflection optical system 125 shown in FIG. 14, the dispersion direction of the light to be measured is reversed before and after the light to be measured is reflected by the flat mirror 133. Therefore, the wavelength resolution can be improved also in the spectroscopic device 120.

For details of the conventional technology described above, refer to Patent Documents 1 to 3 below.
JP 2000-88647 A JP-A-6-221922 JP 2003-139610 A

  By the way, in the spectroscopic device 100 described with reference to FIGS. 10 to 12, the reflection optical system 105 includes four plane mirrors and one reflector, and there are many optical members constituting the reflection optical system 105. Therefore, there is a problem that it is difficult to reduce the size and make assembly adjustment difficult. In the spectroscopic device 120 described with reference to FIGS. 13 and 14, since the lens group 132 is used in the reflective optical system 125, wavelength dispersion occurs, and a wavelength range in which sufficient performance of the spectroscopic device 120 can be obtained is obtained. There is a problem of being limited. Here, it is conceivable to use a lens (achromatic lens) having a small wavelength dispersion, but since such a lens is expensive, there is a problem that the cost of the spectroscopic device 120 is increased.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a spectroscopic device that can be reduced in size, is inexpensive, and can be easily assembled and adjusted.

In order to solve the above-described problems, the spectroscopic device of the present invention includes a wavelength dispersion element (13) and a dispersion direction opposite to each other before and after reflection of light obtained by making light to be measured enter the wavelength dispersion element. provided so as reflected reflecting optical system and a (15, 35), wherein in said light reflected by the reflecting optical system is incident again on the wavelength dispersion element spectroscope for dispersing the light to be measured (10), wherein The reflective optical system includes a convex mirror (23, 26, 27, 43 ) and a concave mirror (22, 42) that are concentrically arranged and have a radius of curvature ratio of n to n + 1 (n is a positive integer ) and a concave mirror (22, 42). The light obtained by making the measurement light incident on the wavelength dispersion element is reflected n times by the convex mirror , and reflected by the concave mirror n + 1 times to reverse the dispersion direction .
According to this invention, the light obtained by making the light to be measured incident on the wavelength dispersion element is reflected n times by the convex mirror provided in the reflective optical system, and is reflected n + 1 times by the concave mirror and emitted from the reflective optical system. Then, it enters the wavelength dispersion element again .
In the spectroscopic device of the present invention, the reflection optical system reflects the light reflected a plurality of times between the convex mirror and the concave mirror and again reflects the light a plurality of times between the convex mirror and the concave mirror. It is provided with a member (44) .
Here, the total number of reflections by the convex mirror is 2n times, and the total number of reflections by the concave mirror is 2 (n + 1) times.

  According to the present invention, the light obtained by causing the light to be measured to be incident on the wavelength dispersion element is reflected by reflecting the light multiple times between the convex mirror and the concave mirror included in the reflective optical system. Can be reduced in size and can be made inexpensive, and further, assembly adjustment can be easily performed.

  Hereinafter, a spectroscopic device according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view showing a configuration of a spectroscopic device according to an embodiment of the present invention. The spectroscopic device shown in FIG. 1 is a double-pass spectroscopic device having a Czerny-Turner type optical system. As shown in FIG. 1, the spectroscopic device 10 of this embodiment includes an entrance slit 11, a concave mirror 12, a diffraction grating 13 as a wavelength dispersion element, a concave mirror 14, a reflection optical system 15, and an exit slit 16.

  The light to be measured that has entered the spectroscopic device 10 travels back and forth within the spectroscopic device 10 and is emitted to the outside. That is, in the forward path, the light to be measured that has entered from the entrance slit 11 enters the reflective optical system 15 through the concave mirror 12, the diffraction grating 13, and the concave mirror 14 in this order, and the measured light that has exited from the reflective optical system 15 in the backward path. Light is emitted from the exit slit 16 through the concave mirror 14, the diffraction grating 13, and the concave mirror 12 in this order.

  The entrance slit 11 limits the intensity of the light to be measured that enters the spectroscopic device 10. The concave mirror 12 converts the light to be measured, which travels from the entrance slit 11 and travels in the forward path, into parallel light and enters the diffraction grating 13, and condenses the light to be measured that travels the backward path diffracted by the diffraction grating 13 to the exit slit 16. To do. The diffraction grating 13 has a diffractive surface 13a in which a large number of grooves are formed, and diffracts parallel light traveling on the forward path from the concave mirror 12 and parallel light traveling on the return path from the concave mirror 14 at different angles for each wavelength.

  The diffraction grating 13 is configured to be rotatable around a rotation axis RX included in the diffraction surface 13a. Accordingly, the wavelength of the measured light that travels in the forward path diffracted by the diffraction grating 13 and enters the concave mirror 14 and the wavelength of the measured light that travels in the backward path diffracted by the diffraction grating 13 and incident on the concave mirror 12 are varied. Can do.

  The concave mirror 14 condenses only the measured light that has entered the concave mirror 14 among the measured light that travels on the forward path diffracted by the diffraction grating 13 and condenses the return path emitted from the reflective optical system 15. The traveling light to be measured is converted into parallel light and is incident on the diffraction grating 13. The reflecting optical system 15 makes the dispersion direction of the light to be measured from the concave mirror 14 reverse (inverted) and makes it incident on the concave mirror 14 again. The exit slit 16 limits the wavelength band of the light to be measured that travels on the return path collected by the concave mirror 12.

  Next, the reflection optical system 15 will be described. 2 is an enlarged perspective view of the reflective optical system 15, FIG. 3 is a plan view of the reflective optical system 15, and FIG. 4 is a side view of the reflective optical system 15. FIG. 2 shows a state in which the measured light traveling on the forward path from the concave mirror 14 is viewed from the side where it enters the reflecting optical system 15. As shown in FIGS. 2 to 4, the reflective optical system 15 includes a slit 21, a concave mirror 22, and a convex mirror 23, and the light to be measured incident on the reflective optical system 15 passes through these optical members in order. The light is emitted from the reflection optical system 15.

  The slit 21 is disposed at the focal position of the concave mirror 14. Therefore, the light to be measured traveling on the forward path collected by the concave mirror 14 is collected at the position of the slit opening of the slit 21. As shown in FIG. 3, when the reflection optical system 15 is viewed in a plan view, the slit 21, the concave mirror 22, and the convex mirror 23 are arranged on the same straight line. On the other hand, as shown in FIG. 4, when the reflective optical system 15 is viewed from the side, the slit 21, the concave mirror 22, and the convex mirror 23 are arranged so that the optical path in the reflective optical system 15 is vertically symmetrical. That is, each optical member constituting the reflection optical system 15 has an incident position P1 of the measurement light with respect to the reflection optical system 15 (a position of the slit opening of the slit 21) and an emission position P2 of the measurement light from the reflection optical system 15. The concave mirror 22 and the convex mirror 23 are arranged so as to be symmetric with respect to the center line passing through the centers thereof.

  The concave mirror 22 and the convex mirror 23 are arranged concentrically, and their centers of curvature are set on a straight line passing through the measurement light incident position P1 (slit 21) and the measurement light emission position P2. That is, the centers of curvature of the concave mirror 22 and the convex mirror 23 are set at the intersection of a center line passing through the centers of the concave mirror 22 and the convex mirror 23 and a straight line passing through the incident position P1 of the measured light and the emission position P2 of the measured light. Yes. In the example shown in FIGS. 3 and 4, the ratio of the radius of curvature between the concave mirror 22 and the convex mirror 23 is set to 2: 1.

  In the above configuration, the light to be measured collected on the slit 21 by the concave mirror 14 enters the slit 21. Here, the wavelength of the light to be measured is selected according to the slit width of the slit 21. The light to be measured that has passed through the slit opening of the slit 21 first enters the concave mirror 22. The measured light is reflected by the concave mirror 22 and then enters the convex mirror 23. The light to be measured that has entered the convex mirror 23 is reflected by the convex mirror 23 and then enters the concave mirror 22 again. However, the light is incident on a position different from the position where the light is incident first. The light to be measured that has entered the concave mirror 22 again is reflected by the concave mirror 22, condensed at the emission position P <b> 2, and emitted from the reflective optical system 15.

  As described above, in the configuration shown in FIGS. 3 and 4, the light to be measured that has passed through the slit 21 is reflected twice by the concave mirror 22 and once by the convex mirror 23, and is totaled between the concave mirror 22 and the convex mirror 23. Reflected 3 times. Therefore, the ratio of the number of reflections at the concave mirror 22 and the number of reflections at the convex mirror 23 is 2: 1, which is the same as the ratio of the curvature radii of the concave mirror 22 and the convex mirror 23.

  The reflecting optical system 15 reflects the measured light an odd number of times between the concave mirror 22 and the convex mirror 23 to reverse the direction of dispersion of the measured light from the concave mirror 14. Here, as shown in FIG. 2, the dispersion direction of the light to be measured incident on the reflecting optical system 15 from the concave mirror 14 is indicated by an arrow with a symbol D <b> 1. Here, it is assumed that the tip side of the arrow labeled D1 has a short wavelength and the base side of the arrow has a long wavelength. When the light to be measured is incident on the reflection optical system 15, as described above, the light to be measured is emitted from the reflection optical system 15 after being reflected between the concave mirror 22 and the convex mirror 23 an odd number of times.

  Here, the dispersion direction of the light to be measured emitted from the reflection optical system 15 is opposite to the dispersion direction of the light to be measured incident on the reflection optical system 15 as indicated by an arrow with a symbol D2. By making the dispersion direction of the measurement light traveling on the return path opposite to the dispersion direction of the measurement light traveling on the forward path by the reflection optical system 15, the measurement light traveling on the return path is further diffracted by the diffraction grating 13. The resolution of the wavelength can be improved.

  Next, a modified example of the reflection optical system 15 will be described. FIG. 5 is a side view showing a first modification of the reflective optical system 15. In FIG. 5, the same components as those of the optical member shown in FIG. As shown in FIG. 5, the reflective optical system 15 according to the first modified example includes a slit 21, a concave mirror 22, and a convex mirror 26, and the light to be measured incident on the reflective optical system 15 is the optical member. Are sequentially emitted from the reflecting optical system 15.

  The reflective optical system 15 according to the first modification shown in FIG. 5 is provided with a convex mirror 26 having a different radius of curvature in place of the convex mirror 23 shown in FIG. 4, and the measurement light incident position P1 and the measurement light The difference is that the distance from the injection position P2 is widened. In the reflective optical system 15 according to the first modification shown in FIG. 5, the concave mirror 22 and the convex mirror 26 are arranged concentrically, similarly to the reflective optical system 15 shown in FIG. Are set on a straight line passing through the incident position P1 (slit 21) and the emission position P2 of the light to be measured. However, the reflective optical system 15 according to the first modification shown in FIG. 5 is different in that the ratio of the radius of curvature of the concave mirror 22 and the convex mirror 26 is set to 3: 2. In accordance with this difference, the interval between the incident position P1 of the measured light and the emission position P2 of the measured light is widened.

  In the reflective optical system 15 according to the first modification having the above-described configuration, the light to be measured that has passed through the slit 21 is reflected three times by the concave mirror 22 and twice by the convex mirror 26, and between the concave mirror 22 and the convex mirror 26. Reflected a total of 5 times. Therefore, the ratio of the number of reflections at the concave mirror 22 and the number of reflections at the convex mirror 26 is 3: 2, which is the same as the ratio of the curvature radii of the concave mirror 22 and the convex mirror 26. As described above, also in the reflective optical system 15 according to the first modification, the measured light is reflected an odd number of times between the concave mirror 22 and the convex mirror 26, and the dispersion direction of the measured light from the concave mirror 14 is reversed. Therefore, the resolution of the wavelength can be improved.

  FIG. 6 is a side view showing a second modification of the reflective optical system 15. In FIG. 6 as well, the same components as those of the optical member shown in FIG. As shown in FIG. 6, the reflective optical system 15 according to the second modified example includes a slit 21, a concave mirror 22, and a convex mirror 27, and the light to be measured incident on the reflective optical system 15 is an optical member of these. Are sequentially emitted from the reflecting optical system 15.

  The reflective optical system 15 according to the second modification shown in FIG. 6 is provided with a convex mirror 27 having a different radius of curvature instead of the convex mirror 23 shown in FIG. 4, and the incident position P1 of the measured light and the measured light The difference is that the distance from the injection position P2 is widened. In the reflective optical system 15 according to the second modification shown in FIG. 6, the concave mirror 22 and the convex mirror 26 are arranged concentrically like the reflective optical system 15 shown in FIG. 4, and the center of curvature of these is the light to be measured. Are set on a straight line passing through the incident position P1 (slit 21) and the emission position P2 of the light to be measured. However, the reflective optical system 15 according to the second modification shown in FIG. 6 is different in that the ratio of the radius of curvature of the concave mirror 22 and the convex mirror 27 is set to 4: 3. In accordance with this difference, the interval between the incident position P1 of the measured light and the emission position P2 of the measured light is widened.

  In the reflective optical system 15 according to the second modification having the above-described configuration, the light to be measured that has passed through the slit 21 is reflected four times by the concave mirror 22 and three times by the convex mirror 26, and between the concave mirror 22 and the convex mirror 26. Reflected 7 times in total. Therefore, the ratio of the number of reflections at the concave mirror 22 and the number of reflections at the convex mirror 26 is 4: 3, which is the same as the ratio of the curvature radii of the concave mirror 22 and the convex mirror 26. Thus, also in the reflective optical system 15 according to the second modification, the measured light is reflected an odd number of times between the concave mirror 22 and the convex mirror 27, and the dispersion direction of the measured light from the concave mirror 14 is reversed. Therefore, the resolution of the wavelength can be improved.

As described above, the reflective optical system 1
As the combination of the convex mirror and the concave mirror, a convex mirror and a concave mirror that are concentric and the ratio of the curvature radii of the convex mirror and the concave mirror is n: n + 1 (n is a positive integer) can be used. When the convex mirror and the concave mirror having such a relationship are used, the light to be measured that has entered the reflective optical system 15 is reflected n + 1 times by the concave mirror and after being reflected n times by the convex mirror, and then from the reflective optical system 15. It is injected. By appropriately changing the value of n described above, the interval (offset) between the incident position P1 of the light to be measured and the emission position P2 of the light to be measured can be easily adjusted.

  Next, another configuration example of the reflection optical system provided in the spectroscopic device 10 will be described. FIG. 7 is a perspective view showing another configuration example of the reflection optical system. The reflection optical system shown in FIG. 7 shows a state viewed from the side where the light to be measured traveling from the concave mirror 14 enters the reflection optical system, similarly to the reflection optical system 15 shown in FIG. . 8 is a plan view of a reflective optical system according to another configuration example shown in FIG. 7, and FIG. 9 is a side view of the reflective optical system.

  As shown in FIGS. 7 to 9, the reflection optical system 35 includes a slit 41, a concave mirror 42, a convex mirror 43, and a reflector 44, and the light to be measured incident on the reflection optical system 35 uses these optical members. Through the reflection optical system 35. The slit 41 is disposed at the focal position of the concave mirror 14. Accordingly, the light to be measured traveling on the forward path collected by the concave mirror 14 is collected at the position of the slit opening of the slit 41. Moreover, the slit 41 is arrange | positioned in the position shifted | deviated from the centerline which passes along the center of the concave mirror 42 and the convex mirror 43, as shown in FIG.8, FIG.9.

  Further, the optical path in the reflection optical system 35 is almost symmetrical with respect to the center line passing through the centers of the concave mirror 42 and the convex mirror 43 regardless of whether the reflection optical system 35 is viewed in a plan view or a side view. A slit 41, a concave mirror 42, a convex mirror 43, and a reflector 44 are arranged so that The reflector 44 is disposed symmetrically with the slit 41 with respect to a center line passing through the centers of the concave mirror 42 and the convex mirror 43 when the reflection optical system 35 is viewed in a plan view. Further, as shown in FIG. 9, the reflector 44 includes reflecting surfaces 44 a and 44 b that are orthogonal to each other, and each of the reflecting surfaces 44 a and 44 b is 45 ° with respect to a center line passing through the centers of the concave mirror 42 and the convex mirror 43. It is arranged to make an angle.

  The concave mirror 42 and the convex mirror 43 included in the reflecting optical system 35 are arranged concentrically similarly to the concave mirror 22 and the convex mirror 23 described with reference to FIGS. 2 to 3, and the center of curvature of these is the incident position P1 of the light to be measured. It is set in a plane perpendicular to the center line passing through the centers of the concave mirror 42 and the convex mirror 43 through the (slit 41) and the emission position P2 of the light to be measured. 8 and 9, the case where the ratio of the curvature radii of the concave mirror 42 and the convex mirror 43 is set to 2: 1 is shown as an example, but FIGS. 5 and 6 are used. As in the case described above, other ratios are possible. The measurement light emission position P2 is set above the measurement light incidence position P1, as shown in FIGS.

  In the above configuration, the light to be measured collected on the slit 41 by the concave mirror 14 enters the slit 41. Here, the wavelength of the light to be measured is selected according to the slit width of the slit 41. The light to be measured that has passed through the slit opening of the slit 41 first enters the concave mirror 42. The measured light is reflected by the concave mirror 42 and then enters the convex mirror 43, and after being reflected by the convex mirror 43, it enters the concave mirror 42 again.

  Here, as shown in FIGS. 7 to 9, the optical axis of the light to be measured that has passed through the slit 41 is shifted obliquely downward from the center line passing through the centers of the concave mirror 42 and the convex mirror 43. For this reason, the light to be measured is reflected once by the concave mirror 42 and the convex mirror 43, so that the light to be measured is incident obliquely upward from the center of the concave mirror 42. More specifically, as described above, the optical path in the reflective optical system 35 is the same as that of the concave mirror 42 and the convex mirror 43 regardless of whether the reflective optical system 35 is viewed planarly or from the side. Since the first incident position and the second incident position with respect to the concave mirror 42 are set symmetrically with respect to the center line passing through the center, the first incident position and the second incident position are symmetrical with respect to the center line passing through the centers of the concave mirror 42 and the convex mirror 43. It is.

  The light to be measured that has entered the concave mirror 42 again enters the reflector 44 and is reflected downward, and then is reflected toward the concave mirror 42 and enters the concave mirror 42. Here, as shown in FIGS. 7 to 9, the light to be measured reflected by the reflector 44 is incident obliquely downward from the center of the concave mirror 42. More specifically, the measured light reflected by the reflector 44 is first incident on the concave mirror 42 with respect to a vertical plane including a center line passing through the centers of the concave mirror 42 and the convex mirror 43. The incident light is incident on a position symmetrical to the incident position.

  The measured light is reflected by the concave mirror 42 and then enters the convex mirror 43, and after being reflected by the convex mirror 43, it enters the concave mirror 42 again. That is, after passing through the slit 41, the light to be measured is incident on the concave mirror 42 again after the third reflection by the concave mirror 42 and the second reflection by the convex mirror 43 (fourth incidence). Here, as described above, since the optical path in the reflection optical system 35 is substantially symmetrical with respect to the center line passing through the centers of the concave mirror 42 and the convex mirror 43, the third incident position and the fourth incident position with respect to the concave mirror 42 Is symmetric with respect to a center line passing through the centers of the concave mirror 42 and the convex mirror 43. The light to be measured that has been reflected by the concave mirror 42 for the fourth time is condensed at the emission position P2 of the light to be measured and then emitted toward the concave mirror 14.

  As described above, the reflective optical system 35 according to the other configuration examples shown in FIGS. 7 to 9 reflects the light to be measured transmitted through the slit 41 twice by the concave mirror 42 and once by the convex mirror 43, and then By reflecting with the reflector 44, it is again reflected twice with the concave mirror 42 and once with the convex mirror 43. That is, the reflection optical system 35 reflects the measurement light by the concave mirror 42 a total of four times and reflects the measurement light by the convex mirror 4 a total of two times until the measurement light transmitted through the slit 41 reaches the emission position P2. And the convex mirror 43 are reflected a total of six times.

  Since the reflective optical system 35 reflects the light to be measured an even number of times between the concave mirror 42 and the convex mirror 43, the reflection optical system 35 changes the dispersion direction of the incident light to be measured as in the reflective optical system 15 shown in FIGS. The light is emitted without changing the direction in which the light to be measured is dispersed. The reflective optical system 35 does not improve the wavelength resolution because the dispersion direction is not reversed, but can improve the dynamic range.

  7 to 9, the combination of the convex mirror and the concave mirror of the reflective optical system 35 is also concentric, and the ratio of the radius of curvature of the convex mirror and the concave mirror is n: n + 1 (n is a positive value). Convex mirrors and concave mirrors that are integers of When a convex mirror and a concave mirror having such a relationship are used, the light to be measured that has entered the reflective optical system 35 is reflected 2 (n + 1) times by the concave mirror, and after being reflected 2n times by the convex mirror, the reflective optical system Injected from 35. By appropriately changing the value of n described above, the interval (offset) between the incident position P1 of the light to be measured and the emission position P2 of the light to be measured can be easily adjusted.

  The spectroscopic device according to the present embodiment described above can reduce the number of optical members of the reflection optical systems 15 and 35 as compared with the conventional reflection optical system. For this reason, the cost of the apparatus can be reduced and the size can be reduced. In addition, since the number of optical components is small and the offset can be adjusted by changing the number of reflections of the light to be measured between the concave mirror and the convex mirror, assembly adjustment can be easily performed.

  The spectroscopic device according to the embodiment of the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and can be freely changed within the scope of the present invention. For example, although the concave mirror and the convex mirror of the reflection optical systems 15 and 35 described above may be separate optical members, it is desirable to integrally form the concave mirror and the concave mirror in order to eliminate the positional adjustment. For example, if a cylindrical glass member has a concave top surface and a convex bottom surface, and a metal such as chromium (Cr) is deposited on the top and bottom surfaces, the top surface is a convex mirror and the bottom surface is a concave mirror. can do. Even when such an optical member is formed, it is necessary that the convex mirror and the concave mirror are concentric, and the ratio of the radius of curvature of the convex mirror and the concave mirror is n: n + 1 (n is a positive integer).

  Furthermore, it is desirable to integrate the slit in addition to the convex mirror and the concave mirror. In the case of integrating the slit, a slit is formed by vapor-depositing a metal such as chromium (Cr) on the top surface of the cylindrical glass member, and the bottom surface of the glass member and the optical member on which the convex mirror and the concave mirror are formed. If the upper surface is bonded, an optical member in which the slit, convex mirror, and concave mirror are integrally formed can be obtained. Further, in the case of the reflective optical system 35 shown in FIG. 7, the reflector 44 is bonded to the upper surface of the glass member having a slit formed on the upper surface, or a part of the upper surface of the glass member is formed into the shape of the reflector 44. Then, an optical member in which the slit, the convex mirror, the concave mirror, and the reflector are integrated can be obtained. In addition, although it is thought that the influence of the wavelength dependence of a refractive index arises by using a glass member, since the wavelength range which injects into a reflective optical system is restrict | limited by a slit, there is little influence by the wavelength dependence of a refractive index. If the spectroscopic device of the present embodiment described above is used, it is possible to measure the wavelength region over a wide range from the visible light region to the infrared light region used for optical communication.

It is a perspective view which shows the structure of the spectroscopic device by one Embodiment of this invention. 2 is an enlarged perspective view of a reflective optical system 15. FIG. 2 is a plan view of a reflective optical system 15. FIG. 3 is a side view of the reflective optical system 15. FIG. 6 is a side view showing a first modification of the reflective optical system 15. FIG. FIG. 10 is a side view showing a second modification of the reflective optical system 15. It is a perspective view which shows the other structural example of a reflective optical system. It is a top view of the reflective optical system which concerns on the other structural example shown in FIG. It is a side view of the reflective optical system which concerns on the other structural example shown in FIG. It is a perspective view which shows the structure of the conventional double pass type | mold spectroscopy apparatus. It is the perspective view which expanded the reflective optical system 105. FIG. 2 is a plan view of a reflective optical system 105. FIG. It is a perspective view which shows the other structure of the conventional double pass type | mold spectroscopy apparatus. It is the perspective view which expanded the reflective optical system 125. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Spectrometer 13 Diffraction grating 15 Reflective optical system 22 Concave mirror 23, 26, 27 Convex mirror 35 Reflective optical system 42 Concave mirror 43 Convex mirror 44 Reflector

Claims (3)

A wavelength dispersion element, and a reflection optical system that reflects light obtained by making the light to be measured incident on the wavelength dispersion element so that the dispersion direction is opposite before and after reflection, and is reflected by the reflection optical system In a spectroscopic device for allowing the measured light to enter the wavelength dispersion element again and split the measured light,
The reflective optical system includes a convex mirror and a concave mirror arranged concentrically and having a radius of curvature ratio of n to n + 1 (n is a positive integer), and is obtained by causing the light to be measured to enter the wavelength dispersion element. The spectroscopic apparatus is characterized in that the reflected light is reflected n times by the convex mirror and is reflected n + 1 times by the concave mirror to reverse the dispersion direction . The reflection optical system includes a reflecting member that reflects light reflected a plurality of times between the convex mirror and the concave mirror and reflects the light a plurality of times again between the convex mirror and the concave mirror. The spectroscopic device according to claim 1. 3. The spectroscopic apparatus according to claim 2, wherein the total number of reflections at the convex mirror is 2n, and the total number of reflections at the concave mirror is 2 (n + 1).

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