Optical member, optical system, and spectroscopic device

Abstract

To solve the problem in which: there has been a demand for an optical member for a spectroscopic device with a simple configuration that can pass a light beam traveling on a predetermined optical path and can prevent passage of light traveling outside the predetermined optical path, so-called stray light.SOLUTION: An optical member comprises a through hole penetrating from a first opening to a second opening and emits, from the second opening, a light beam of observation light incident from the first opening. The through hole includes an inclined wall surface inclined with respect to an optical axis of the light beam so as to arrange a portion with an inner diameter smaller than that of the first opening between the first opening and the second opening. The inclined wall surface reflects stray light incident on the first opening from a direction different from the optical axis of the light beam of the observation light, toward the second opening at least once.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical member that allows a light beam traveling along a predetermined optical path to pass, but suppresses the passage of so-called stray light that deviates from the predetermined optical path. [Background technology]

[0002] 2. Description of the Related Art Conventionally, spectroscopic devices have been used in various fields such as astronomical observation and material analysis to disperse light into wavelengths, receive the light with a detector, and measure its intensity.

[0003] Patent Document 1 proposes an optical element for a spectroscopic device used in fields such as astronomical observation. The proposed optical element is useful for constructing a surface-division optical system when simultaneously performing spectral observation of two-dimensional spatial information acquired with a single exposure.

[0004] Patent Document 2 proposes an area spectroscopic device that includes a reflecting section that splits a light beam incident from the object surface side into multiple light beams and reflects them to different positions, an imaging mirror, a spectroscopic element such as a diffraction grating, and a detecting section.

[0005] Patent Document 3 describes the provision of a detachable light trapping member in a spectroscope with a variable F-number of the emitted light beam. The light trapping member has multiple protrusions protruding toward the optical axis, and is structured to guide and trap intruding stray light into recessed spaces between the multiple protrusions, preventing the stray light from escaping. The length of the protrusions protruding toward the optical axis is configured so that the protrusions on the exit side of the light are longer than the protrusions on the entrance side of the light. Furthermore, the length of the protrusions differs for each light trapping member, and an appropriate light trapping member is selected and attached to the spectroscope depending on the desired F-number. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-21057 [Patent Document 2] Japanese Patent Publication No. 2022-96461 [Patent Document 3] Japanese Patent Application Laid-Open No. 2008-185525 Summary of the Invention [Problem to be solved by the invention]

[0007] In a spectrometer equipped with a surface-splitting optical system, numerous optical elements (e.g., reflective elements, refractive elements, diffractive elements) are arranged to split the observation light incident from the object surface side into multiple beams and guide them to the detector. In the process of splitting the beam and guiding it to the detector, so-called stray light may be generated, for example, when part of the beam is scattered by the edge of a mirror and propagates in an unintended direction. When stray light reaches and is detected by the detector, it becomes noise, which reduces the spectroscopic accuracy of the spectrometer.

[0008] The light trapping member described in Patent Document 3 has a complex structure of the recess that traps stray light, and its size in the direction perpendicular to the optical axis is large, making it difficult to apply to the optical paths of each light beam in a surface-dividing optical system that handles a large number of light beams.

[0009] Therefore, there has been a demand for an optical element for a spectroscopic device with a simple structure that allows a light beam traveling along a predetermined optical path to pass while suppressing the passage of so-called stray light that deviates from the predetermined optical path.There has also been a demand for a spectroscopic device with a surface-division optical system that has high spectroscopic accuracy and suppresses noise caused by stray light. [Means for solving the problem]

[0010] A first aspect of the present invention is an optical element having a through hole extending from a first opening to a second opening, and emitting a beam of observation light incident from the first opening from the second opening, wherein the through hole has an inclined wall surface inclined with respect to the optical axis of the beam of light so that a portion having an inner diameter smaller than that of the first opening is located between the first opening and the second opening, and the inclined wall surface reflects stray light incident on the first opening from a direction different from the optical axis of the beam of observation light at least once toward the second opening.

[0011] A second aspect of the present invention is an optical element having a plurality of through holes penetrating from a first opening to a second opening, and emitting a beam of observation light incident from the first opening from the second opening, characterized in that the plurality of through holes have inclined wall surfaces inclined with respect to the optical axis of the beam of light so that a portion having an inner diameter smaller than that of the first opening is positioned between the first opening and the second opening. [Effects of the Invention]

[0012] According to the present invention, an optical element for a spectroscopic device having a simple structure can be provided, which allows a light beam traveling along a predetermined optical path to pass while suppressing the passage of so-called stray light that deviates from the predetermined optical path.Furthermore, according to the present invention, a spectroscopic device having a surface-division optical system and high spectroscopic accuracy in which noise due to stray light is suppressed can be provided. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic cross-sectional view for explaining the configuration of a spectroscopic device according to a first embodiment. [Figure 2] FIG. 3 is a partial cross-sectional view of a spectroscopic device for explaining the cause of stray light and the function of a stray light suppression member. [Figure 3] FIG. 10 is an external perspective view of an optical member in which a stray light suppression member and a light dividing mirror are integrated. [Figure 4] 5 is a schematic diagram showing a state in which a luminous flux of observation light passes through a through-hole provided in a stray light suppression member. [Figure 5]FIG. 4 is a partial cross-sectional view illustrating one of the through holes provided in the stray light suppression member according to the embodiment. [Figure 6] FIG. 10 is a partial cross-sectional view showing one of the through holes provided in the member according to the reference embodiment. [Figure 7] A diagram showing a so-called aperture or slit. [Figure 8] FIG. 10 is a diagram schematically showing a state in which stray light is incident on an inclined surface of a stray light suppression member. [Figure 9] (a) A diagram showing a through hole of a modified example, (b) A diagram showing a through hole of another modified example, (c) A diagram showing a through hole of another modified example, (d) A diagram showing a through hole of another modified example, and (e) A diagram showing a through hole of another modified example. [Figure 10] (a) An example where the through hole is circular. (b) An example where the through hole is elliptical. (c) An example where the through hole is rectangular. (d) An example where the through hole is rectangular with rounded corners. (e) An example where the through hole is diamond-shaped. (f) An example where the through hole is trapezoidal. (g) An example where the through hole is triangular. [Figure 11] FIG. 10 is an external perspective view of a stray light suppression member used in the spectroscopic device according to the second embodiment. [Figure 12] FIG. 10 is a partial cross-sectional view of a spectroscopic device according to a second embodiment. [Figure 13] FIG. 10 is a schematic diagram of an area spectroscopic device according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] The following describes optical members, spectroscopic devices, and the like according to embodiments of the present invention with reference to the drawings. Note that the embodiments shown below are merely examples, and those skilled in the art can appropriately modify and implement the detailed configurations, for example, without departing from the spirit and scope of the present invention.

[0015] In the drawings referred to in the following description of the embodiments, elements denoted by the same reference numerals have the same functions unless otherwise specified. When a plurality of identical elements are arranged in a drawing, the reference numerals and their descriptions may be omitted.

[0016] In addition, because the drawings may be represented schematically for the convenience of illustration and explanation, the shape, size, and arrangement of elements depicted in the drawings may not strictly correspond to the actual objects. Furthermore, the descriptions "XX or more and YY or less" and "XX to YY" that represent a numerical range mean a numerical range including the endpoints XX (lower limit) and YY (upper limit), unless otherwise specified. When a numerical range is described in stages, the upper and lower limits of each numerical range can be arbitrarily combined.

[0017] In the following description, for example, when "X plus direction" is written, it refers to the same direction as the X axis arrow in the coordinate system shown, and when "X minus direction" is written, it refers to the direction 180 degrees opposite to the direction of the X axis arrow in the coordinate system shown. Also, when simply written as "X direction," it refers to the direction parallel to the X axis, regardless of whether it is different from the direction of the X axis arrow in the drawings. The same applies to directions other than X.

[0018] [Embodiment 1] (Overall composition) FIG. 1 is a schematic cross-sectional view illustrating the configuration of a spectroscopic device according to a first embodiment. The spectroscopic device includes optical elements 1, 2, 3, and 4, and a light-receiving sensor 5. An optical system including optical elements 1, 2, 3, and 4 may also be referred to as a spectroscopic optical system 501. Optical element 1 is an optical element that integrates a light-splitting mirror M1, which serves as a first mirror, with a stray light suppression member 7. Optical element 2 is an optical element that includes a light-transmitting portion that transmits incident light 6 and multiple second mirrors M2. The light-transmitting portion may be formed of an aperture or a light-transmitting member, but FIG. 1 shows an example in which an aperture is provided. Optical element 3 is an optical element that includes multiple third mirrors M3. In this embodiment, a reflective diffraction grating may be used as the third mirror M3. Optical element 4 is an optical element that includes multiple fourth mirrors M4.

[0019] Incident light 6, which is the object of observation, travels in the positive X direction and enters the light dividing mirror M1 inside the device through the light transmitting portion of optical member 2. The reflecting surface of light dividing mirror M1 is configured so that incident light 6 is divided into multiple light beams 6a and reflected in different directions. Optical members 1 and 2 are configured so that each of the light beams 6a reflected in different directions is directed toward one of multiple second mirrors M2 that are dispersedly arranged. The multiple second mirrors M2 are arranged along a curved surface centered on the optical axis of incident light 6. The number of divisions of light dividing mirror M1 is the same as the number of second mirrors M2.

[0020] Each of the light beams 6a reflected in different directions by the light splitting mirror M1 is incident on one of the multiple second mirrors M2 and reflected by the second mirror M2 as light beams 6b. The optical axis of each light beam 6b is parallel to the positive X direction, and each light beam 6b passes through one of the multiple through-holes in the stray light suppression member 7 and is incident on one of the multiple third mirrors M3. Each of the multiple second mirrors M2 is a concave mirror, and its reflecting surface shape is set so that the light beams 6b are condensed within the through-hole of the stray light suppression member 7. The same number of third mirrors M3 as the number of second mirrors M2 are provided corresponding to the second mirrors M2. The configuration and operation of the stray light suppression member 7 will be described in detail later.

[0021] A reflective diffraction grating is provided on the reflective surface of each of the multiple third mirrors M3, and is configured to reflect (diffract) a predetermined wavelength component of the incident light beam 6b toward one of the multiple fourth mirrors M4. The multiple fourth mirrors M4 are arranged at intervals so as not to block the optical path of the light beam 6b that has passed through the stray light suppression member 7 until it is incident on the third mirror M3. When the multiple fourth mirrors M4 are integrated into the optical member 4, an opening is provided in the optical member 4 to allow the light beam 6b that has passed through the stray light suppression member 7 to pass through. The same number of fourth mirrors M4 as the number of third mirrors M3 are provided corresponding to the third mirrors M3.

[0022] The reflecting surfaces of the multiple fourth mirrors M4 are arranged to reflect the light beam of a predetermined wavelength component incident from the third mirror M3 toward the light-receiving surface of the light-receiving sensor 5. The light reflected by the fourth mirror M4 travels as a parallel light beam in the positive X direction and illuminates the light-receiving surface of the light-receiving sensor 5. The multiple third mirrors M3 are arranged at intervals so as not to block the optical path of the measurement light reflected by the fourth mirror M4 until it enters the light-receiving sensor 5. When the multiple third mirrors M3 are integrated into the optical member 3, an opening is provided in the optical member 3 to allow the measurement light reflected by the fourth mirror M4 to pass through.

[0023] The light-receiving sensor 5 is a sensor in which pixels sensitive to the wavelength of the incident measurement light are arranged two-dimensionally, and for example, a CMOS sensor or a CCD sensor is used. An information processing unit (not shown) acquires spectral image data of the incident light 6 based on the output signal of the light-receiving sensor 5, and can perform information processing such as storing the data in a storage unit, transmitting the data to an external computer via a network, analyzing the object to be observed by image processing, and displaying the analytical image.

[0024] (stray light suppression material) Next, we will explain the stray light suppression member 7. Figure 2 is a partial cross-sectional view of the spectroscopic device for explaining the cause of stray light and the function of the stray light suppression member 7.

[0025] As described above, the incident light 6 to be observed passes through the light-transmitting portion of the optical member 2 and enters the light-splitting mirror M1 inside the device, where it is split into multiple light beams 6a and reflected in different directions. The light-splitting mirror M1 is configured as a polyhedron made up of a combination of reflecting surfaces with different orientations in order to split the incident light 6 into multiple light beams 6a and reflect them in different directions. The boundaries between the reflecting surfaces with different orientations (the edges of the reflecting surfaces) are not geometrically ideal lines with infinitesimal widths, but rather have curved shapes that correspond to the precision of realistic processing techniques. As a result, the incident light 6 is scattered in various directions at the edges, becoming scattered light (stray light SL).

[0026] Furthermore, each of the light beams 6a reflected by the light splitting mirror M1 is incident on the second mirror M2 and reflected as a light beam 6b whose optical axis is parallel to the positive X direction. Because the outer edge of the second mirror M2 is not a geometrically ideal infinitesimal corner but has a curved shape that corresponds to the precision of realistic processing technology, the light beams 6a are scattered in various directions by the edge and become scattered light (stray light SL).

[0027] Such scattered light (stray light SL) travels in a direction different from the optical path that the observation light should travel, and becomes stray light when it is reflected by components inside the spectrometer, etc. When the stray light reaches and is detected by the light-receiving sensor 5, it becomes noise, which leads to a decrease in the spectroscopic accuracy of the spectrometer. The spectroscopic device according to this embodiment is provided with a compact stray light suppression member 7 that transmits observation light but attenuates stray light by multiple reflection.

[0028] Fig. 3 is an external perspective view of the optical member 1 in which the stray light suppression member 7 and the light dividing mirror M1 are integrated. In this embodiment, to enable the stray light suppression member 7 to be easily installed with high relative positional accuracy with respect to other optical members, the light dividing mirror M1 and the stray light suppression member 7 are fixed to the housing C1 of the optical member 1, as shown in Fig. 3. As long as the stray light suppression member 7 can be fixed in an appropriate position in the optical system of the spectroscopic device, a different structure may be used for installation.

[0029] Fig. 4 is a schematic diagram showing how the observation light beam 6b passes through the through-holes 7a provided in the stray light suppression member 7. As shown in Fig. 4, the stray light suppression member 7 has multiple through-holes 7a for individually passing through the light beams 6b reflected from each second mirror M2. The stray light suppression member 7 is installed so that the position where the light beams 6b reflected by the second mirror M2, which is a concave mirror, are focused is located within the through-holes 7a.

[0030] The base of the stray light suppression member 7 can be made of metals such as invar, aluminum, or stainless steel, or ceramics such as silicon nitride. The outer surface of the stray light suppression member 7 and the wall surfaces of the through holes 7a are blackened to absorb (attenuate) light. An appropriate blackening method can be selected depending on the wavelength band of the observation light and the material of the stray light suppression member. For example, nickel or chrome can be blackened, black anodized aluminum can be used, or a black surface treatment using electroless plating can be used.

[0031] FIG. 5 is a partial cross-sectional view of one of the through holes 7a included in the stray light suppression member 7 according to this embodiment, illustrating the behavior of the light beam 6b (observation light) and stray light SL incident within the through hole 7a. The through hole 7a has an inner diameter large enough to prevent interference with the light beam 6b at any position in the X direction. However, the through hole 7a does not define a cylindrical space with a constant inner diameter. The inner wall defining the space of the through hole 7a is an inclined surface inclined with respect to the optical axis direction of the light beam 6b (i.e., the X direction). When the diameter of the entrance through which the light beam 6b enters is d1 and the diameter of the exit through which the light beam 6b exits is d3, the inner diameter of the through hole 7a, as viewed along the X direction, gradually decreases from d1 to d2 (d1>d2) and then gradually increases from d2 to d3 (d3>d2).

[0032] FIG. 6 shows, as a reference embodiment, a member in which a cylindrical space having a constant inner diameter at any position in the X direction is defined as a through-hole 7a'.

[0033] 5 and 6, stray light SL enters the through-hole from a direction different from the X direction, which is the optical axis direction of the light beam 6b (observation light). Generally, on a surface that has been painted black, the reflectivity increases as the angle of incidence of light increases, that is, as the angle of incidence of light approaches parallel to the reflecting surface.

[0034] In the case of the reference embodiment of FIG. 6, stray light SL that enters the through hole 7a' at a large incident angle θ3 is reflected with a relatively high reflectance when it hits the wall surface. It then re-enters the wall surface at an incident angle θ3 and is reflected with a relatively high reflectance. This process is repeated within the through hole 7a', but the stray light SL that enters at a large incident angle θ3 is reflected with a relatively high reflectance and is therefore less likely to be attenuated. Furthermore, because the incident angle θ when reflected from the wall surface remains the same, in the example of FIG. 6, it takes three reflections to reach the exit of the through hole 7a'. Therefore, the stray light SL exits the exit of the through hole 7a' as stray light SL' without its intensity being sufficiently attenuated.

[0035] In contrast, the stray light suppression member 7 according to this embodiment of FIG. 5 is configured such that the wall surface of the through hole 7a is inclined with respect to the optical axis of the light beam 6b (observation light). When stray light SL enters the through hole from the same direction as in the reference embodiment, the angle of incidence θ1 with respect to the wall surface can be made smaller in this embodiment than the angle of incidence θ3 in the reference embodiment (θ1<θ3). Furthermore, in this embodiment, the angle between the traveling direction of the stray light SL and the optical axis of the light beam 6b changes each time it is reflected. Therefore, even if the length H of the member along the optical axis direction of the light beam 6b (observation light) is the same, this embodiment can increase the number of times the stray light SL is reflected by the wall surface of the through hole compared to the reference embodiment. In the example of FIG. 5, the stray light SL is reflected seven times by the wall surface before reaching the exit of the through hole 7a. Furthermore, the angle of incidence θ2 in the second reflection can be made smaller than the angle of incidence θ1 in the first reflection (θ2<θ1). This allows the reflectance in the second reflection to be smaller than the reflectance in the first reflection.

[0036] As described above, according to this embodiment, the angle of incidence of stray light SL with respect to the wall surface inside the through hole 7a can be reduced and the number of reflections within the through hole 7a can be increased, so that the intensity of stray light SL' reaching the exit of the through hole 7a is sufficiently attenuated.

[0037] The shape of the through-hole can be set, for example, according to the following guidelines: Here, the expected incident angle of stray light is θ, the reflectance of the stray light suppression member at the observation wavelength for the incident angle θ is K, the desired attenuation rate of stray light is A%, and the required number of reflections is n. The required number of reflections on the wall surface can be calculated using the following approximate formula, shown as Equation 1. K n ≦A...(Formula 1)

[0038] In reality, the angle of incidence decreases with each reflection on the wall surface, and the reflectance of stray light decreases little by little, so the number of reflections n defined by Equation 1 provides a sufficient attenuation effect.

[0039] The number of reflections n required on the wall surface can be determined as a function of the entrance opening diameter of the through hole d1, the narrowest diameter d2, the exit opening diameter d3, and the thickness of the stray light suppression member H. n=f(θ,d1,d2,d3,H) (Formula 2)

[0040] Here, the attenuation rate of stray light in the embodiment and the reference embodiment will be described using specific examples. Assume that the wavelength band of light to be observed is in the infrared region (wavelength 800 nm to 2500 nm), the diameter of the observation light incident on the stray light suppression member is 0.2 mm, and the angle of incidence of the stray light into the stray light suppression member (the angle formed with the optical axis of the observation light) is 7 degrees. Also assume that the reflectance of the inner wall surface of the stray light suppression member, which has been black anodized, is 40% under the condition of an incident angle of 83 degrees.

[0041] If it is desired to attenuate stray light to 1% or less in the stray light suppression member, then from equation 1, the number of reflections required on the wall surface is n=6 or more.

[0042] In order to set the number of reflections on the wall surface to n=6 or more, in the embodiment, the dimensions of each portion of the through hole 7a of the stray light suppression member 7 can be set as follows: d1=0.3 [mm], d2=0.1 [mm], d3=0.3 [mm], and H=8.0 [mm], for example. In this case, the number of reflections of the stray light SL inside the through hole 7a is 7, as shown in Fig. 5, and the attenuation rate of the stray light SL' exiting from the outlet relative to the stray light SL entering from the inlet is 0.16% according to Equation 1.

[0043] On the other hand, in the reference embodiment of FIG. 6, when H=8 [mm] and d1=0.3 [mm], the number of reflections of the stray light SL in the through-hole is three as shown in FIG. 6, and the attenuation rate is only 6.4%.

[0044] As described above, the stray light suppression member according to the embodiment has a significantly higher effect of attenuating stray light than the reference embodiment having the same thickness and the same opening diameter, and therefore it is possible to provide a compact spectroscopic device that suppresses noise caused by stray light, has high spectroscopic accuracy, and is also compact.

[0045] This embodiment is configured to reflect stray light SL incident from the first opening toward the second opening at least once on the wall surface within the through hole, preferably by reflecting the stray light SL multiple times on the wall surface within the through hole to attenuate it. Therefore, shapes with a small h, such as those shown in FIG. 7, such as so-called apertures or slits, are outside the scope of this embodiment. This is because the shape of FIG. 7 allows stray light SL to pass through the opening without being reflected multiple times on the inner wall surface of the through hole, even if it has an inclined wall surface. In this regard, this embodiment satisfies H>d1 and H>d3, for example, as shown in FIG. 5.

[0046] Furthermore, when providing a wall surface inclined with respect to the optical axis direction of the observation light within the through-hole, it is undesirable to incline the wall surface so as to reflect the incident stray light in an undesired direction. Figure 8 shows a schematic diagram of stray light SL incident on the inclined surface of the stray light suppression member 7. The stray light SL is incident at an angle α with respect to the optical axis of the observation light beam 6b. If the angle γ of the wall surface of the through-hole with respect to the optical axis of the observation light beam 6b is defined as the inclination angle, it is desirable to set the inclination angle γ to be less than 90°-α (γ<90°-α). If the inclination angle γ of the wall surface is greater than 90°-α, as shown in Figure 8, the stray light SL is reflected by the wall surface in the direction of the dotted line, becoming stray light SLR. This stray light returns toward the second mirror M2 (Figure 1), potentially generating additional stray light and reducing the spectral accuracy. Furthermore, in order to prevent interference between the observation light beam 6b and the wall surface of the through-hole, when the convergence angle of the light beam 6b is β, the inclination angle γ of the wall surface is preferably set to β or more (γ≧β).

[0047] (Manufacturing method) Next, a method for manufacturing the stray light suppression member 7 will be described. For example, an aluminum material (A5052) with a plate thickness of H is prepared, and through holes of a predetermined shape are formed at predetermined positions by wire-cut discharge, followed by black anodizing to produce the stray light suppression member 7. The completed stray light suppression member 7 is fixed to the housing C1 of the optical member 1 shown in FIG. 3 by, for example, set screws.

[0048] The material of the stray light suppression member is not limited to aluminum, and may be, for example, metal such as invar or SUS, or ceramic. Furthermore, the method of forming the through holes is not limited to wire-cut discharge. Depending on the shape and size of the through holes, they may be cut through the substrate from both the front and back sides using a cutting tool such as an end mill. The blackening treatment for enhancing the light absorption effect may be other than black anodizing, and may be, for example, paint coating.

[0049] (Variation) Next, modified examples of the stray light suppression member 7 according to the embodiment will be described. Figures 9(a) to 9(e) show partial cross-sectional views of one of the through holes 7a included in different modified examples of the stray light suppression member 7. As with Figure 5, the behavior of the light beam 6b (observation light) and stray light SL incident on the through hole 7a is shown.

[0050] The modified examples shown in FIGS. 9(a) to 9(e) are optical elements (stray light suppression elements) that, like the embodiment shown in FIG. 5, have a through hole that penetrates from a first opening to a second opening, and allow observation light beam 6b to enter through the first opening so as to be condensed within the through hole and exit through the second opening. In each case, the inner wall surface of the through hole has an inclined wall surface that is inclined with respect to the optical axis (X-axis) of the light beam 6b so that a portion with a smaller inner diameter than the first opening is disposed between the first and second openings. The inclined wall surface does not interfere with the observation light beam 6b that is condensed within the through hole, and attenuates stray light SL that enters the first opening from a direction different from the optical axis (X-axis) of the observation light beam 6b by reflecting it at least multiple times before reaching the second opening.

[0051] Among the modified examples shown in Figures 9(a) to 9(e), the modified example shown in Figures 9(a) to 9(d) has a portion in the middle of the through hole that has an inner diameter smaller than the first opening and also smaller than the second opening.

[0052] In the modified example shown in FIG. 9(a), a region with a constant aperture diameter, i.e., a region whose inner wall surface is parallel to the optical axis (X-axis) of the beam 6b, is disposed on both the first aperture side where the beam 6b of observation light enters and the second aperture side where the beam 6b exits. Between these two regions, an inclined wall surface is provided that is inclined with respect to the optical axis (X-axis) of the beam 6b. A portion is disposed midway through the through hole whose inner diameter is smaller than both the first aperture and the second aperture. In this modified example, the inner wall surface of the through hole does not interfere with the beam 6b of observation light that is focused within the through hole. Stray light SL that enters the first aperture from a direction different from the optical axis (X-axis) of the beam 6b of observation light is reflected multiple times and attenuated before reaching the second aperture.

[0053] In the modified example shown in FIG. 9(b), a region with a constant aperture diameter, i.e., a region where the inner wall surface is parallel to the optical axis (X-axis) of the beam 6b of observation light, is provided only on the side of the first aperture onto which the beam 6b of observation light is incident. Furthermore, an inclined wall surface inclined with respect to the optical axis (X-axis) of the beam 6b is provided in the remaining region. A portion is provided midway through the through hole whose inner diameter is smaller than both the first aperture and the second aperture. Even in this modified example, the inner wall surface of the through hole does not interfere with the beam 6b of observation light that is condensed within the through hole. Stray light SL that enters the first aperture from a direction different from the optical axis (X-axis) of the beam 6b of observation light is reflected multiple times and attenuated before reaching the second aperture.

[0054] In the modified example shown in FIG. 9(c), similar to the modified example shown in FIG. 9(a), a region with a constant aperture diameter, i.e., a region whose inner wall surface is parallel to the optical axis (X-axis) of the luminous flux 6b, is disposed on both the first aperture side where the luminous flux 6b of the observation light enters and the second aperture side where the luminous flux 6b exits. Between these two regions, an inclined wall surface is provided that is inclined with respect to the optical axis (X-axis) of the luminous flux 6b. A portion is disposed midway through the through hole whose inner diameter is smaller than both the first aperture and the second aperture. In the modified example shown in FIG. 9(a), the position where the inner diameter of the through hole is smallest when viewed along the optical axis of the luminous flux 6b coincides with the position where the luminous flux 6b is focused. In contrast, in the modified example shown in FIG. 9(c), the position where the luminous flux 6b is focused is located closer to the first aperture than the position where the inner diameter of the through hole is smallest. In some cases, the layout may be such that the position where the light beam 6b is focused is closer to the second opening than the position where the inner diameter of the through-hole is smallest. Even in this modification, the inner wall surface of the through-hole does not interfere with the light beam 6b of the observation light that is focused inside the through-hole, and stray light SL that enters the first opening from a direction different from the optical axis (X-axis) of the light beam 6b of the observation light is reflected multiple times and attenuated before reaching the second opening.

[0055] In the modified example shown in FIG. 9(d), similar to the embodiment shown in FIG. 5, the inner wall surface of the through hole has an inclined wall surface inclined with respect to the optical axis of the light beam 6b so that a portion having a smaller inner diameter than the first and second openings is located between the first and second openings. In the embodiment shown in FIG. 5, the portion of the through hole where the inner diameter is smallest is located at the center between the first and second openings in the direction of the optical axis of the light beam 6b. In contrast, in the modified example shown in FIG. 9(d), the portion of the through hole where the inner diameter is smallest is located closer to the second opening than the first opening. Note that, in some cases, the portion of the through hole where the inner diameter is smallest may be located closer to the first opening than the second opening. In this modified example, the inner wall surface of the through hole does not interfere with the light beam 6b of the observation light that is condensed within the through hole. However, stray light SL that enters the first opening from a direction different from the optical axis (X-axis) of the light beam 6b of the observation light is reflected multiple times and attenuated before reaching the second opening.

[0056] In the modified example shown in FIG. 9(e), the inner wall surface of the through hole has an inclined wall surface inclined with respect to the optical axis of the light beam 6b so that a portion with a smaller inner diameter than the first opening is disposed between the first and second openings. The stray light suppression member 7 in FIG. 9(e) is composed of two members 7A each having a tapered through hole (inclined wall surface). The stray light suppression member 7 can be easily fabricated by stacking two members 7A each having a tapered through hole (inclined wall surface). The number of stacked members is not limited to two, and more members may be stacked. In this modified example, the inner wall surface of the through hole does not interfere with the observation light beam 6b that is condensed within the through hole. However, stray light SL that enters the first opening from a direction different from the optical axis (X-axis) of the observation light beam 6b is reflected multiple times before reaching the second opening, thereby being attenuated.

[0057] Next, several examples of the shape of the through hole 7a in the direction perpendicular to the optical axis of the light beam 6b will be described. The cross-sectional shape of the through hole when the stray light suppression member is cut on a plane perpendicular to the optical axis of the light beam 6b from the first opening through which the observation light beam 6b enters to the second opening through which it exits can be configured so that the cross-sectional shape is similar no matter where the cut is made. Figures 10(a) to 10(g) show examples of the shape of the through hole in the direction perpendicular to the optical axis of the light beam 6b. The illustrated shapes can be the shape of the first opening (entrance side), the shape of the portion of the through hole where the inner diameter is smallest, or the shape of the second opening (exit side).

[0058] Fig. 10(a) is a circle, Fig. 10(b) is an ellipse, Fig. 10(c) is a rectangle, Fig. 10(d) is a rectangle with rounded corners, Fig. 10(e) is a rhombus, Fig. 10(f) is a trapezoid, and Fig. 10(g) is a triangle. The shape of the through-hole can be set appropriately depending on the cross-sectional shape of the observation light beam 6b cut in a direction perpendicular to the optical axis, the collection angle of the beam 6b, the angle at which stray light SL enters the through-hole, etc.

[0059] [Embodiment 2] The configuration of a spectroscopic device according to embodiment 2 will now be described. In the spectroscopic optical system 501 of embodiment 1 described with reference to Fig. 1, the stray light suppression member 7 was disposed at the same position as the light dividing mirror M1 in the direction of travel (X direction) of the light beam 6b reflected by the second mirror M2. The stray light suppression member according to the present invention does not have to be disposed at the same position as in embodiment 1, as long as it can reflect and attenuate stray light multiple times without interfering with the observation light.

[0060] In the second embodiment, a stray light suppression member 70 is disposed between the second mirror M2 and the light dividing mirror M1 in the direction of travel (X direction) of the light beam 6b reflected by the second mirror M2. Fig. 11 is an external perspective view of the stray light suppression member 70 used in the spectroscopic device according to the second embodiment, and Fig. 12 is a partial cross-sectional view of the spectroscopic device according to the second embodiment. Note that Fig. 12 corresponds to a partial cross-sectional view of the spectroscopic device taken along the dashed dotted line in Fig. 11 in parallel to the ZX plane. Descriptions of elements common to the first embodiment will be simplified or omitted.

[0061] The stray light suppression member 70 is fixed to the housing 8 that supports the optical members 1 and 2, and is fixed so as to have a predetermined positional relationship with the light dividing mirror M1 and the second mirror M2.

[0062] As shown in Fig. 11, the base of the stray light suppression member 70 has a recess that is recessed in the shape of a quadrangular pyramid in the X direction. As shown in Fig. 12, a light dividing mirror M1 is disposed at the bottom of the recess that is recessed in the shape of a quadrangular pyramid. The recess of the stray light suppression member 70 functions as an optical path space that allows the incident light 6 that travels toward the light dividing mirror M1 along the positive X direction and the multiple light beams 6a that travel from the light dividing mirror M1 toward the second mirror to pass through.

[0063] A plurality of through-holes 7a are provided in the base of the stray light suppression member 70 to allow passage of a plurality of light beams 6b that are reflected by the second mirror M2 and whose optical axes are parallel to the X direction. Each of the second mirrors M2 is a concave mirror, and the shape of the reflecting surface of the second mirror M2 is set so that the light beams 6b are condensed within the through-holes 7a of the stray light suppression member 70.

[0064] As described above, the base of the stray light suppression member 70 is formed with a quadrangular pyramidal recess in the X direction, and the length of the through-holes 7a formed in the base in the X direction is shorter the closer the through-hole is to the light dividing mirror M1. The size or shape of the first opening on the incident side may be different depending on which of the multiple light beams 6b the through-hole 7a is passing through. Because the light beams 6b are condensed as they travel in the X direction, for example, the diameter of the first opening may be smaller for through-holes closer to the light dividing mirror M1. On the other hand, it is desirable that the second openings on the exit side of each through-hole 7a have the same shape.

[0065] At least some of the plurality of through holes 7a have a portion between the first opening and the second opening that has a smaller inner diameter than the first opening. That is, the inner wall surfaces of at least some of the plurality of through holes 7a have inclined wall surfaces that are inclined with respect to the optical axis (X-axis) of the luminous flux 6b. The inclined wall surfaces do not interfere with the luminous flux 6b of the observation light that is condensed inside the through hole, and attenuate stray light SL that enters the first opening from a direction different from the optical axis (X-axis) of the luminous flux 6b of the observation light by reflecting it at least multiple times before it reaches the second opening.

[0066] It is desirable to provide inclined walls for all of the multiple through holes 7a so that a portion between the first and second openings has an inner diameter smaller than that of the first opening. However, in some cases, inclined walls may be provided only for some of the through holes. For example, in the example shown in FIG. 12, the through holes located near the beam splitter mirror M1 have inclined walls, while the through holes located farther from the beam splitter mirror M1 do not have inclined walls and are configured with only walls parallel to the optical axis of the light beam 6b. This is because the through holes located farther from the beam splitter mirror M1 are long in the X direction, and even without inclining the inner wall surface, stray light can be reflected from the inner wall surface a sufficient number of times to attenuate the light between the first opening and the second opening. On the other hand, the through holes located near the beam splitter mirror M1 are short in the X direction, and therefore have inclined inner wall surfaces to reflect stray light between the first opening and the second opening a sufficient number of times to attenuate the light between the first opening and the second opening.

[0067] For convenience of illustration, FIG. 12 shows only two different lengths of the through holes in the X direction. However, in reality, many through holes are formed along the Z and Y directions, resulting in more than two different lengths of the through holes in the X direction. In such a case, for example, inclined wall surfaces may be provided only on through holes whose X direction length is equal to or shorter than a predetermined length. Alternatively, the inclination angle and position of the inclined wall surfaces may be set according to the X direction length of each through hole, so that the incident stray light SL is reflected by the inner wall surfaces a sufficient number of times before reaching the second opening, thereby being attenuated. Of course, the inner wall surfaces of all through holes are configured so as not to interfere with the luminous flux 6b of the observation light focused within the through hole.

[0068] According to this embodiment, an optical element for a spectroscopic device having a simple structure can be provided, which allows a light beam traveling along a predetermined optical path to pass while suppressing the passage of so-called stray light that deviates from the predetermined optical path. Also, according to this embodiment, a compact spectroscopic device can be provided, which has a surface-division optical system, suppresses noise due to stray light, and has high spectroscopic accuracy.

[0069] [Embodiment 3] 13 is a schematic diagram of an area spectroscopic device 500 according to embodiment 3. In area spectroscopic device 500, observation light to be subjected to area spectroscopic analysis is incident on spectroscopic optical system 501 of the above embodiment (e.g., FIG. 1), rearranged by area division, and then passes through imaging mirror 502, spectroscopic element 503, and detection unit 504 (light-receiving sensor), thereby performing area spectroscopic analysis. The light to be spectroscopically analyzed is, for example, infrared light.

[0070] In the surface spectroscopic device 500, light from a spectroscopic optical system 501 is reflected onto a spectroscopic element 503 such as a diffraction grating using an imaging mirror 502 which is an off-axis parabolic mirror. The light beam dispersed by the spectroscopic element 503 and spread on the surface is diffracted and again incident on the imaging mirror 502 which is also a parabolic mirror, and forms an image on a detection unit 504 which has a two-dimensional detector. This makes it possible to obtain the result of the image surface being dispersed. Note that in the first embodiment, a reflective diffraction grating is used as the third mirror M3 of the spectroscopic optical system 501, but in this embodiment, a total reflection mirror may be used as the third mirror M3. To obtain the original image for each wavelength, the images of the desired wavelengths on the two-dimensional detector are rearranged according to a division rule to obtain the original spectral image.

[0071] [Other embodiments] The present invention is not limited to the above-described embodiments, and many modifications are possible within the technical spirit of the present invention. For example, the above-described different embodiments may be combined in whole or in part.

[0072] The location of the stray light suppression member is not limited to the examples shown in FIGS. 1 and 12, and it can be located at any position in a spectroscopic device equipped with a surface-division optical system. For example, in FIG. 1, the stray light suppression member may be located between the fourth mirror M4 and the third mirror M3, or between the third mirror M3 and the light-receiving sensor 5. That is, the stray light suppression member can be located in the optical path where the observation light beam is incident on either the second mirror M2, the fourth mirror M4, or the third mirror M3. It is desirable to locate the stray light suppression member at a position in the optical system where the observation light beam is focused, but it may also be located at a position where the observation light beam is a parallel beam that is not focused.

[0073] For example, in the embodiments shown in Figures 9(a) to 9(d), through-holes 7a may be formed by drilling holes from both sides of a single substrate to allow communication between them, or by stacking multiple members each having a tapered through-hole (inclined wall surface), as in the example of Figure 9(e). In the example of Figure 9(e), two members are stacked so that the inclined surfaces of the through-holes are repeated in the same direction, but the embodiments shown in Figures 9(a) to 9(d) can be produced by stacking two members facing each other so that the inclined surfaces of the through-holes are facing opposite directions.

[0074] In the first embodiment, an example is shown in which the incident light path and the reflected light path are arranged coaxially (on one axis), but the embodiment is not limited to this. For example, as described in International Publication WO2020 / 203976, even in a so-called off-axis optical system in which the incident light axis is tilted at an appropriate angle with respect to the mirror axis, a stray light suppression member can be arranged on the light path.

[0075] This specification discloses at least the following: [Item 1] a through hole extending from the first opening to the second opening; an optical member that causes a beam of observation light incident from the first opening to exit from the second opening, the through hole has an inclined wall surface inclined with respect to the optical axis of the light beam so that a portion having an inner diameter smaller than that of the first opening is disposed between the first opening and the second opening, the inclined wall surface reflects stray light incident on the first opening from a direction different from the optical axis of the beam of observation light at least once toward the second opening. An optical element characterized by: [Matter 2] the inclined wall surface does not interfere with the luminous flux of the observation light, and reflects the stray light multiple times before reaching the second opening. 2. The optical element according to item 1, [Matter 3] A beam of observation light incident from the first opening is condensed in the through hole. 3. The optical member according to item 1 or 2. [Matter 4] The through hole has a portion between the first opening and the second opening, the portion having an inner diameter smaller than both the first opening and the second opening. 4. The optical member according to any one of items 1 to 3, characterized in that: [Matter 5] The inclined wall surface is configured so that an incident angle of the stray light when the stray light is reflected on the inclined wall surface changes while the stray light is reflected multiple times on the inclined wall surface. 5. The optical member according to any one of items 1 to 4. [Matter 6] When the length from the first opening to the second opening of the through hole is H, the opening diameter of the first opening is d1, and the opening diameter of the second opening is d3, H>d1 and H>d3, 6. The optical member according to any one of items 1 to 5, characterized in that: [Matter 7] When the angle that the inclined wall surface makes with respect to the optical axis of the luminous flux of the observation light is defined as γ and the condensing angle at which the luminous flux of the observation light incident on the through hole is defined as β, γ≧β, 4. The optical element according to item 3, [Matter 8] When the angle that the inclined wall surface makes with respect to the optical axis of the luminous flux of the observation light is defined as γ and the angle that the stray light incident on the first opening makes with respect to the optical axis of the luminous flux of the observation light is defined as α, γ<90°-α, 8. The optical member according to any one of items 1 to 7, characterized in that: [Matter 9] In a cross section of the optical member taken along a direction perpendicular to the optical axis of the light beam, the cross-sectional shapes of the through holes are similar between the first opening and the second opening. 9. The optical member according to any one of items 1 to 8, characterized in that: [Matter 10] The shape of the first opening when viewed from the optical axis direction of the light beam is any one of a circle, an ellipse, a rectangle, a rectangle with rounded corners, a rhombus, a trapezoid, and a triangle. 10. The optical member according to any one of items 1 to 9, characterized in that: [Matter 11] In a cross section of the optical member cut along a plane passing through the optical axis of the light beam, the through hole has an inner wall surface parallel to the optical axis of the light beam between the inclined wall surface and the first opening. 11. The optical member according to any one of items 1 to 10. [Matter 12] In a cross section of the optical member cut along a plane passing through the optical axis of the light beam, the through hole has an inner wall surface parallel to the optical axis of the light beam between the inclined wall surface and the second opening. 12. The optical member according to any one of items 1 to 11. [Matter 13] a portion of the through hole having the smallest inner diameter is disposed at the center between the first opening and the second opening in the direction of the optical axis of the light beam; 13. The optical member according to any one of items 1 to 12. [Matter 14] a portion of the through hole having the smallest inner diameter is disposed at a position shifted from the center of the first opening and the second opening in the direction of the optical axis of the light beam; 13. The optical member according to any one of items 1 to 12. [Matter 15] the light beam is condensed at a portion of the through hole with the smallest inner diameter; 8. The optical member according to item 3 or 7, [Matter 16] the light beam is condensed at a position shifted from a portion of the through hole with the smallest inner diameter; 8. The optical member according to item 3 or 7, [Matter 17] a plurality of members each having a part of the through hole are stacked in the direction of the optical axis of the light beam; 17. The optical member according to any one of items 1 to 16, [Matter 18] The inner wall surface of the through hole is blackened. 18. The optical member according to any one of items 1 to 17, [Matter 19] a plurality of through holes extending from the first opening to the second opening; an optical member that causes a beam of observation light incident from the first opening to exit from the second opening, the plurality of through holes have inclined wall surfaces inclined with respect to the optical axis of the light beam so that a portion having an inner diameter smaller than that of the first opening is disposed between the first opening and the second opening; An optical element characterized by: [Matter 20] The optical element according to any one of items 1 to 19, a first mirror that splits the observation light into multiple beams and reflects them in different directions; a second mirror disposed in the optical path of each of the plurality of light beams reflected by the first mirror; a third mirror disposed in the optical path of each of the plurality of light beams reflected by the second mirror; a fourth mirror disposed in the optical path of each of the plurality of light beams reflected by the third mirror; Equipped with the optical member is disposed in the optical path of the plurality of light beams incident on the third mirror or the fourth mirror. An optical system characterized by: [Matter 21] the third mirror comprises a reflective diffraction grating; 21. The optical system according to item 20. [Matter 22] 21. An optical system according to item 20; a light-receiving sensor that receives the plurality of light beams reflected by the fourth mirror; A spectroscopic device characterized by: [Matter 23] 21. An optical system according to item 20; an imaging mirror that forms an image of the plurality of light beams reflected by the fourth mirror; a spectroscopic element; a light receiving sensor; A spectroscopic device characterized by: [Explanation of symbols]

[0076] 1···Optical element / 2···Optical element / 3···Optical element / 4···Optical element / 5···Light receiving sensor / 6···Incoming light / 6a···Light beam / 6b···Light beam / 7···Stray light suppression element / 7a···Through hole / 70···Stray light suppression element / 8···Housing / 500···Area spectroscopic device / 501···Spectroscopic optical system / 502···Imaging mirror / 503···Spectroscopic element / 504···Detection unit / C1···Housing / M1···Light splitting mirror / M2···Second mirror / M3···Third mirror / M4···Fourth mirror / SL···Stray light

Claims

1. a through hole extending from the first opening to the second opening; an optical member that causes a light beam of observation light incident from the first opening to exit from the second opening, the through hole has an inclined wall surface inclined with respect to an optical axis of the light beam so that a portion having an inner diameter smaller than that of the first opening is disposed between the first opening and the second opening, the inclined wall surface reflects stray light, which enters the first opening from a direction different from the optical axis of the beam of observation light, at least once toward the second opening. An optical element characterized by:

2. the inclined wall surface does not interfere with the luminous flux of the observation light, and reflects the stray light multiple times before reaching the second opening. The optical member according to claim 1 .

3. a beam of observation light incident from the first opening is condensed in the through hole; The optical member according to claim 1 .

4. the through hole has a portion between the first opening and the second opening, the portion having an inner diameter smaller than both the first opening and the second opening; The optical member according to claim 1 .

5. The inclined wall surface is configured so that an incident angle of the stray light when the stray light is reflected on the inclined wall surface changes while the stray light is reflected multiple times on the inclined wall surface. The optical member according to claim 1 .

6. When the length from the first opening to the second opening of the through hole is H, the opening diameter of the first opening is d1, and the opening diameter of the second opening is d3, H>d1 and H>d3; The optical member according to claim 1 .

7. When the angle that the inclined wall surface makes with respect to the optical axis of the luminous flux of the observation light is defined as γ and the condensing angle at which the luminous flux of the observation light incident on the through hole is defined as β, γ≧β, The optical member according to claim 3 .

8. When the angle that the inclined wall surface makes with respect to the optical axis of the luminous flux of the observation light is defined as γ and the angle that the stray light incident on the first opening makes with respect to the optical axis of the luminous flux of the observation light is defined as α, γ<90°−α; The optical member according to claim 1 .

9. In a cross section of the optical member cut along a direction perpendicular to the optical axis of the light beam, the cross-sectional shapes of the through holes are similar between the first opening and the second opening. The optical member according to claim 1 .

10. The shape of the first opening when viewed from the optical axis direction of the light beam is any one of a circle, an ellipse, a rectangle, a rectangle with rounded corners, a rhombus, a trapezoid, and a triangle. The optical member according to claim 1 .

11. In a cross section of the optical member cut along a plane passing through the optical axis of the light beam, the through hole has an inner wall surface parallel to the optical axis of the light beam between the inclined wall surface and the first opening. The optical member according to claim 1 .

12. In a cross section of the optical member cut along a plane passing through the optical axis of the light beam, the through hole has an inner wall surface parallel to the optical axis of the light beam between the inclined wall surface and the second opening. The optical member according to claim 1 .

13. a portion of the through hole having the smallest inner diameter is disposed at a center between the first opening and the second opening in a direction of the optical axis of the light beam; The optical member according to claim 1 .

14. a portion of the through hole having the smallest inner diameter is disposed at a position shifted from the center between the first opening and the second opening in the direction of the optical axis of the light beam; The optical member according to claim 1 .

15. the light beam is condensed at a portion of the through hole with the smallest inner diameter; The optical member according to claim 3 .

16. the light beam is condensed at a position shifted from a portion of the through hole with the smallest inner diameter; The optical member according to claim 3 .

17. a plurality of members each having a part of the through hole are stacked in the direction of the optical axis of the light beam; The optical member according to claim 1 .

18. The inner wall surface of the through hole is blackened. The optical member according to claim 1 .

19. a plurality of through holes extending from the first opening to the second opening; an optical member that causes a light beam of observation light incident from the first opening to exit from the second opening, the plurality of through holes have inclined wall surfaces inclined with respect to the optical axis of the light beam so that a portion having an inner diameter smaller than that of the first opening is disposed between the first opening and the second opening; An optical element characterized by:

20. The optical member according to any one of claims 1 to 19, a first mirror that splits the observation light into a plurality of beams and reflects them in different directions; a second mirror disposed in the optical path of each of the plurality of light beams reflected by the first mirror; a third mirror disposed in the optical path of each of the plurality of light beams reflected by the second mirror; a fourth mirror disposed in the optical path of each of the plurality of light beams reflected by the third mirror, the optical member is disposed on an optical path of the plurality of light beams incident on the third mirror or the fourth mirror. An optical system characterized by:

21. the third mirror comprises a reflective diffraction grating; 21. The optical system of claim 20.

22. an optical system according to claim 20; a light-receiving sensor that receives the plurality of light beams reflected by the fourth mirror, A spectroscopic device characterized by:

23. an optical system according to claim 20; an imaging mirror that forms an image of the plurality of light beams reflected by the fourth mirror; a spectroscopic element; a light receiving sensor; A spectroscopic device characterized by:

Images