Abstract
An optical measuring device determines a concentration of measurement gas in a sample gas by light absorption. The optical measuring device includes a light source, a deflecting mirror, a primary mirror, a secondary mirror and a radiation detector. A section between the light source and the deflecting mirror is configured to receive the sample gas. The light source is configured to emit light in the direction of the deflecting mirror. The deflecting mirror is configured to act as a collimator for incident light and to deflect the incident light in the direction of the primary mirror. The primary mirror and the secondary mirror are configured to direct the light deflected by the deflecting mirror onto the radiation detector.
Claims
1. An optical measuring device for determining the concentration of measurement gas in a sample gas by light absorption, the optical measuring device comprising: a light source; a deflecting mirror; a primary mirror; a secondary mirror; a radiation detector; and a housing, wherein a section between the light source and the deflecting mirror is arranged and configured to receive the sample gas, wherein the light source is arranged and configured to emit light in a direction of the deflecting mirror, wherein the deflecting mirror is arranged and configured to act as a collimator for incident light and to deflect incident light in a direction of the primary mirror, wherein the primary mirror and the secondary mirror are arranged and configured to direct light deflected by the deflecting mirror onto the radiation detector, wherein respective optical axes of the light source, deflecting mirror, primary mirror and secondary mirror are collinear to each other, wherein the light source, the primary mirror, the secondary mirror and the radiation detector are arranged in the housing, wherein the deflecting mirror is arranged outside the housing, and wherein the housing comprises a translucent window which is arranged in a light beam path between the light source and the deflecting mirror.
2. An optical measuring device according to claim 1, wherein the radiation detector is located on the optical axis of the primary mirror and secondary mirror.
3. An optical measuring device according to claim 1, wherein a distance between the light source and the deflecting mirror is variable along the optical axis of the deflecting mirror, whereby an absorption length is adjustable.
4. An optical measuring device according to claim 1, wherein the primary mirror and the secondary mirror are configured as a Cassegrain telescope arrangement.
5. An optical measuring device according to claim 4, wherein the Cassegrain telescope arrangement has no optical elements other than the primary mirror and the secondary mirror.
6. An optical measuring device according to claim 5, wherein the primary mirror has a central recess configured to direct light deflected by the secondary mirror through the central recess onto the radiation detector.
7. An optical measuring device according to claim 1, further comprising a second light source configured to emit a second light in a direction of the radiation detector.
8. An optical measuring device according to claim 1, further comprising: a second radiation detector; and a beam splitter, wherein the beam splitter is arranged in the light beam path in front of the radiation detector and is configured to guide a part of the light in the direction of the radiation detector and to guide another part of the light in a direction of the second radiation detector.
9. An optical measuring device according to claim 8, wherein the radiation detector and/or the second radiation detector is a multi-channel detector.
10. An optical measuring device according to claim 8, wherein an optical surface of the secondary mirror and/or an optical surface of the primary mirror comprises structured portions configured to enlarge a radiation distribution on the radiation detector and/or to enlarge a radiation distribution on the second radiation detector.
11. An optical measuring device according to claim 1, wherein the radiation detector is a multi-channel detector.
12. An optical measuring device according to claim 1, wherein an optical surface of the secondary mirror and/or an optical surface of the primary mirror comprises structured portions configured to enlarge a radiation distribution on the radiation detector.
13. An optical measuring device according to claim 11, wherein the structured sections are spherical, hyperbolic or parabolic.
14. An optical measuring device according to claim 11, wherein the structured sections are configured as facets and/or as grooves.
15. An optical measuring device according to claim 14, wherein the facets are configured as a hexagonal elevation or recess, wherein a facet surface bounded by edges of the facet is convex, concave and/or flat.
16. An optical measuring device according to claim 1, further comprising an optical waveguide arranged in a light beam path in front of the radiation detector.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0095] In the drawings:
[0096] FIG. 1 is a schematic view showing an example of an optical measuring device according to the invention;
[0097] FIG. 2 is a schematic view showing an example of an optical measuring device according to the invention;
[0098] FIG. 3 is a schematic view showing an example of an optical measuring device according to the invention;
[0099] FIG. 4 is a schematic detailed view showing aspects of an embodiment of an optical measuring device according to the invention with an optical waveguide;
[0100] FIG. 5 is a schematic detailed view of an embodiment of an optical measuring device according to the invention with a secondary mirror with structured sections;
[0101] FIG. 6 is a perspective view of a secondary mirror according to the invention with structured sections;
[0102] FIG. 7a is a schematic detailed top view of a radiation detector according to the invention;
[0103] FIG. 7b is a schematic detailed top view of a radiation detector according to the invention;
[0104] FIG. 7c is a schematic detailed top view of a multi-channel detector according to the invention;
[0105] FIG. 8 is a schematic detailed view of a primary mirror according to the invention and a secondary mirror according to the invention, each with structured sections;
[0106] FIG. 9a is a schematic detailed front view of a radiation detector according to the invention;
[0107] FIG. 9b is a schematic detailed front view of a radiation detector according to the invention;
[0108] FIG. 9c is a schematic detailed front view of a multi-channel detector according to the invention;
[0109] FIG. 10 is a schematic detailed view of an embodiment of an optical measuring device according to the invention with a beam splitter and a second radiation detector.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0110] Referring to the drawings, FIGS. 1, 2, 3, 4, 5 and 10 show optical measuring devices 1 according to the invention or detailed views of optical measuring devices 1 according to the invention.
[0111] The optical measuring device 1 according to the invention is used to determine the concentration of measurement gas in a sample gas by light absorption.
[0112] As shown schematically in FIGS. 1, 2, 3, 4, 5 and 10, the optical measuring device 1 according to the invention comprises a light source 10, a deflecting mirror 20, a primary mirror 31, a secondary mirror 32 and a radiation detector 40.
[0113] The light source 10 is configured to emit light in the direction of the deflecting mirror 20. For example, the light source 10 can be an incandescent lamp or a light-emitting diode and can also have a reflector 11. As shown in FIGS. 1 and 2, the reflector 11 can be an elliptical reflector 11 or, as shown in FIG. 3, an approximately spherical reflector 11. The optional reflector 11 is used to focus the light in the direction of the deflecting mirror 20.
[0114] The light emitted by the light source 10 in the direction of the deflecting mirror 20 and possibly bundled with the aid of the reflector 11 is shown in FIGS. 1, 2, 3 as a schematic beam S1.
[0115] A section A between the light source 10 and the deflecting mirror 20 is configured to receive the sample gas. Section A can be provided, for example, by a measuring cuvette or by an open measuring system as described above. Since the light advantageously passes through section A twice, it has an optical path length 2*L, where L indicates the length of section A. The optical path length 2*L is also referred to as the absorption length.
[0116] The deflecting mirror 20 is configured to act as a collimator for incident light, for example for the schematic beam S1, and to reflect the incident light, for example the schematic beam S1, deflected in the direction of the primary mirror 31. The light deflected in this way is shown in FIGS. 1, 2, 3, 4 and 5 as schematic beam S2. As shown in these figures, the light deflected in the direction of the primary mirror 31 is reflected essentially parallel to an optical axis X of the deflecting mirror 20 due to the effect of the deflecting mirror 20 as a collimator.
[0117] The primary mirror 31 and the secondary mirror 32 are configured to direct the light deflected by the deflecting mirror 20, for example the schematic beam S2, onto the radiation detector 40.
[0118] By providing the primary mirror 31 and the secondary mirror 32 and thus by providing a telescope arrangement, a compact design of the optical measuring device 1 can be achieved with a high focal length at the same time.
[0119] In the embodiments shown in FIGS. 1, 2, 3, 4, 5 and 10, the respective optical axes X of light source 10, deflecting mirror 20, primary mirror 31 and secondary mirror 32 are collinear to each other.
[0120] As described above, this leads to a folding of the beam path into itself. This can be seen in the schematic beam path in FIGS. 1, 2, 3, 4, 5 and 10. The light deflected by the deflecting mirror 20, shown schematically as beam S2, falls on the primary mirror 31, which reflects the beam S2, for example as beam S3, in the direction of the secondary mirror 32. Secondary mirror 32 in turn reflects beam S3, for example as beam S4, in the direction of radiation detector 40. Beams S2, S3 and S4 are folded into themselves, as can be seen in the figures mentioned. In this way, a symmetrical angle of incidence distribution can be advantageously generated with a compact configuration and long focal length.
[0121] The radiation detector 40 is configured to detect light in the ultraviolet and/or infrared wavelength range, for which purpose the radiation detector 40 has at least one detector element 41, shown schematically in FIGS. 7a, 7b, 7c and 9a, 9b, 9c. In a preferred embodiment of the invention, the radiation detector 40 can be a multi-channel detector which has at least one further detector element 41 in addition to the detector element 41. Such a multi-channel detector is shown schematically in FIGS. 7c, 9c and in FIGS. 4, 5, 10.
[0122] Preferably, and as shown in FIGS. 1, 2, 3, 4, 5 and 10, the radiation detector 40 is arranged such that the detector element 41 and possibly the further detector element 41 lie in a focus or a focal plane of the beam path. This can be achieved by suitably spacing the radiation detector 40 from the secondary mirror 32. However, it is not necessary for the detector element 41 and possibly the further detector element 41 to lie in a focus or a focal plane of the beam path.
[0123] According to the invention and shown schematically in FIGS. 1, 2, and 3, the light source 10, the primary mirror 31, the secondary mirror 32 and the radiation detector 40 are arranged in a common housing 50, with the deflecting mirror 20 being arranged outside the housing 50. In this preferred embodiment, the housing 50 comprises a translucent window 60 which is arranged in the beam path between the light source 10 and the deflecting mirror 20 so as not to obstruct the beam path but to physically close off the housing from the outside. In the illustrated embodiments, the window 60 is consequently arranged to transmit the exemplary beams S1 and S2. Preferably, the housing 50 is encapsulated in a pressure-tight manner and the window 60 is sealed gas-tight with respect to the housing 50.
[0124] In all of the illustrated embodiments of the optical measuring device 1, a distance d (shown in FIGS. 1, 2, 3) between the light source 10 and the deflecting mirror 20 can be variable along the optical axis X of the deflecting mirror 20 in order to adjust the absorption length. This can be achieved, for example, by variable-length mounting of the deflecting mirror 20 relative to the housing 50, for example by linear guidance of the deflecting mirror 20 in a spacer (mounting spacer) on the housing side.
[0125] Preferably, the deflecting mirror 20 in the illustrated embodiments is variable in terms of its curvature, as described above.
[0126] In the embodiments shown in FIGS. 1, 2, 3, 4, 5 and 10, the primary mirror 31 and the secondary mirror 32 can be configured as a Cassegrain telescope arrangement, which enables a particularly high focal length in a compact design.
[0127] In the illustrated embodiments according to FIGS. 1, 2, 3, 4, 5 and 10, the primary mirror 31 also preferably has a central recess 33 to extend the focal length in order to direct the light deflected by the secondary mirror 32, for example the beam S4, through the central recess 33 onto the radiation detector 40.
[0128] FIG. 2 shows that the optical measuring device 1 can also preferably comprise a second light source 70, which is configured to emit a second light, shown schematically in FIG. 2 as beam S5, in the direction of the radiation detector 40. The provision of a second light source 70 advantageously allows the compensation of a drift of the radiation detector 40.
[0129] Particularly preferably, the second light source 70 is provided collinear to the radiation detector 40, as shown, so that the radiation detector 40 is irradiated substantially perpendicularly.
[0130] Preferably, and as shown in FIG. 10, the optical measuring device 1 can comprise a second radiation detector 80 and a beam splitter 90. The beam splitter 90 can be arranged in the beam path in front of the radiation detector 40 in order to guide part of the light, for example beam S4, in the direction of the radiation detector 40, for example as schematic beam S4, and to guide another part of the light in the direction of the second radiation detector 90, for example as schematic beam S4.
[0131] In FIG. 10, the beam splitter 90 is configured as a dichroic or trichroic beam splitter, for example.
[0132] FIGS. 6, 8 show examples of a primary mirror 31 and secondary mirror 32 according to the invention. As can be seen in these figures, primary mirrors 31 and secondary mirrors 32 can be produced, for example, as essentially cylindrical basic bodies which have an optical surface F1 and F2 respectively. However, primary mirror 31 and secondary mirror 32 can also be provided in any other way as long as they have an optical surface F1 and F2, respectively.
[0133] As shown in FIGS. 6, 8, an optical surface F2 of the secondary mirror 32 and/or an optical surface F1 of the primary mirror 32 can have structured sections 34, 35 in order to influence a radiation distributionshown schematically in FIGS. 7a, 7b, 7c and 9a, 9b, 9c as surfaces Va, Vb, Vc, Vdon the radiation detector 40 and/or the second radiation detector 80, in particular to increase the radiation distribution Va, Vb, Vc, Vd.
[0134] The structured sections 34, 35 can, for example, be configured as facets 34 and/or grooves 35.
[0135] In the example shown in FIG. 6, the optical surface F2 of the secondary mirror 32 has structured sections 34 in the form of facets 34.
[0136] In the example shown in FIG. 8, the primary mirror 31 has structured sections 35 in the form of grooves 35 which run parallel to each other in a first orientation and the secondary mirror 32 has structured sections 35 in the form of grooves 35 which run parallel to each other in a second orientation. As shown, the primary mirror 31 and the secondary mirror 32 may be oriented relative to each other such that the first orientation and the second orientation are substantially perpendicular (essentially perpendicular) to each other.
[0137] FIG. 7a schematically shows a radiation distribution Va as it is generated with an optical measuring device 1 in which neither primary mirror 31 nor secondary mirror 32 have structured sections 34, 35, 35. In this case, the radiation distribution Va is essentially circular.
[0138] FIGS. 7b, 7c show schematic radiation distributions Vb as generated with an optical measuring device 1 in which the primary mirror 31 and/or the secondary mirror 32 have structured sections 34 in the form of facets 34. In this case, the radiation distribution Vb is enlarged compared to the example shown in FIG. 7a. The radiation distribution Vb corresponds to a hexagon in the plane of the detector element 41, for example, in the event that only the primary mirror 31 or the secondary mirror 32 has structured sections 34 in the form of hexagonal facets 34.
[0139] In FIG. 5, a detailed view of an optical measuring device 1 schematically shows that the radiation distribution Va, Vb, Vc, Vd on the radiation detector 40 and/or the second radiation detector 80 can be influenced and, in particular, enlarged due to the structured sections 34, 35, 35. This is illustrated schematically by means of the beam S3 which, after reflection by the secondary mirror 32, falls on the radiation detector 40 as beams S41, S42.
[0140] FIG. 9a schematically shows a radiation distribution Vc as generated with an optical measuring device 1, in which either the primary mirror 31 or the secondary mirror 32 have structured sections 35, 35 in the form of grooves 35, 35. In this exemplary case, the radiation distribution Vc essentially corresponds to an elongated ellipse.
[0141] In the exemplary case shown in FIGS. 9b, 9c, the radiation distribution Vd essentially corresponds to a rectangle, for the case shown in FIG. 8 that both the primary mirror 31 and the secondary mirror 32 have the structured sections 35, 35 in the form of grooves 35, 35.
[0142] In an embodiment shown in FIG. 4, the optical measuring device 1 also has an optical waveguide 100, which is arranged in the beam path in front of the radiation detector 40. In the example shown in FIG. 4, the optical waveguide 100 is a waveguide. Multiple reflections of the incident light, for example of the schematic beam S4, occur within the optical waveguide 100 and thus advantageously lead to a homogenization of the light distribution on the beam detector 40 or its detector element 41 (or detector elements 41, 41).
[0143] It is not shown that the optical measuring device 1 can also comprise a second optical waveguide, which can be arranged in the beam path in front of the second radiation detector 80.
[0144] All of the features disclosed herein can be combined with each other as desired, insofar as this does not affect alternatives or is contradictory.
[0145] While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.
LIST OF REFERENCE CHARACTERS
[0146] 1 Optical measuring device [0147] 10 Light source [0148] 11 Reflector [0149] 20 Directional mirror [0150] 31 Primary mirror [0151] 32 Secondary mirror [0152] 33 Recess [0153] 34, 35, 35 Structured sections [0154] 40 Radiation detector [0155] 41, 41 Detector element [0156] 50 Housing [0157] 60 Window [0158] 70 Second light source [0159] 80 Second radiation detector [0160] 90 Beam splitter [0161] 100 Optical waveguide [0162] A Section [0163] d Distance [0164] F1, F2 Optical surface [0165] L Length of the section [0166] S1, S2, S3, [0167] S4, S4, S4, [0168] S5, S41, S42 Beam [0169] Va, Vb, Vc, Vd Radiation distribution [0170] X Optical axis
