Measuring device for measuring the concentration of a gas by means of raman spectroscopy

Abstract

The invention relates to a Raman spectroscopy device (30) for measuring the concentration of a gas (22). The essence of the invention is that the Raman spectroscopy device (30) has a carrier element (72) and a mounting plate (73), wherein the carrier element (72) has a connection portion (74) and a laser portion (75), wherein in the laser portion (75) the carrier element (72) has holes (76) via which the housing (70) of the laser diode (16) and the mounting plate (73) are connected to the carrier element (72) by means of the pins (71), wherein in the connection portion (74) the carrier element (72) has holes (76) via which connection pins (77) can be passed, wherein the carrier element (72) is connected to the Raman spectroscopy device (30) by means of the connection pins (77).

Description

[0001] R. 415166

[0002] - 1 -

[0003] Measuring device for measuring the concentration of a gas using Raman spectroscopy

[0004] Technical field

[0005] The invention relates to a measuring device for concentration measurement and / or quantitative concentration evaluation of a gas or a gas mixture by means of Raman spectroscopy, with at least one gas measurement chamber for the gas or the gas mixture.

[0006] State of the art

[0007] From the prior art, e.g., from “A. Stratmann and G. Schweiger, Fluid Phase Equilibria of Ethanol and Carbon Dioxide Mixtures with Concentration Measurements by Raman Spectroscopy, Appl. Spectrosc. 56 (6) 2002, 783-788), it is known that the particle concentration (N / V) and thus the gas density p can be determined locally at the Raman measurement volume V using Raman spectroscopy. A prerequisite for measurement using Raman spectroscopy is a powerful, compact light source that illuminates the sample gas and thus excites it. For this purpose, a high-power light source, e.g., with a wavelength of 440 nm in the form of a diode laser, can be used.

[0008] From DE102021107229.8, DE102009026744A1 and EP3748339A2, measuring devices for the concentration measurement of a gas are known, in which powerful diode lasers are used to excite the gas to be measured. R. 415166

[0009] - 2 -

[0010] Description of the invention

[0011] The inventors recognized that a laser diode generates waste heat, which must be dissipated in a controlled manner to prevent thermal failure of the laser diode. Furthermore, in Raman spectroscopy, it is essential to maintain the laser diode at a constant temperature to prevent the emitting laser diode wavelength from drifting. Maintaining a constant temperature is also crucial to keeping the emitting optical power of the laser diode constant. Both a changing wavelength and a changing optical power would distort the measurement result, as the gas being measured would be illuminated with these altered values ​​during the measurement, and the Stokes response would be correspondingly different. The proposed solution dynamically dissipates the operating heat of the laser diode used as the light source for Raman spectroscopy.This ensures thermally stable operation of the light source, while at the same time the laser diode does not need to be throttled down during operation to protect it from overheating, which in turn would impair the productivity of the Raman spectroscopy device.

[0012] The invention relates to a Raman spectroscopy device for measuring the concentration of a gas, comprising a gas measurement chamber for the gas, which has one or more optical inlets and one or more optical outlets, and a gas supply line for supplying the gas to the gas measurement chamber during the concentration measurement. The Raman spectroscopy device includes a high-power laser, wherein the high-power laser comprises a laser diode configured as a light source for excitation of the high-power laser, the laser diode being arranged in a housing, and the laser diode being electrically contactable via pins. The Raman spectroscopy device comprises a collecting optical system with at least one filter and at least one aperture, and a spectral analysis unit. The Raman spectroscopy device captures Raman scattered light through the collecting optical system. R. 415166

[0013] - 3 -

[0014] system with at least one filter and at least one aperture of the spectral analysis unit.

[0015] The core of the invention is that the Raman spectroscopy device comprises a support element and a circuit board, the support element having a connection area and a laser area. The laser area of ​​the support element has bores through which the housing of the laser diode and the circuit board are connected to the support element by means of pins. It is conceivable that the connection area is cuboid and the laser area is circular. It is also conceivable that the laser diode and circuit board, on the one hand, and the support element, on the other, are floatingly mounted, i.e., not rigidly connected to each other. The support element can be designed as a whole in the form of a disk with a thickness between 0.2 and 8.0 mm.

[0016] It is conceivable that the support element has bores in the connection area through which connection pins can be guided, with the support element being connected to the Raman spectroscopy device by means of the connection pins.

[0017] It can be advantageous to solder the housing containing the laser diode to the circuit board. This is beneficial because it creates a stable connection between the laser diode and the circuit board, which also offers high temperature resistance, a particular advantage in laser technology.

[0018] Furthermore, the circuit board may be designed to be multilayered and include a temperature-measuring component that is thermally connected to the substrate, in particular an SMD or THT component, an NTC element, and / or a Pt100 or a quartz crystal / oscillator. This is advantageous because a constant temperature is crucial in laser technology to ensure consistent processing parameters and thus accurate measurement results. Using such a component for temperature measurement significantly reduces the influence of the thermal inertia of masses not belonging to the laser diode. The result is a direct and fast temperature measurement. R. 415166

[0019] - 4 -

[0020] Temperature control of the laser diode from ±0.01 °C to ±1 °C. Using a quartz crystal oscillator is advantageous because it can perform additional functions, such as pressure / force monitoring, i.e., monitoring the contact force of the laser diode against the substrate. If an SMD or THT component is used, it is ideally mounted at the point where the heat generation of the laser diode is at its maximum, i.e., where most of the heat is generated and dissipated. It is conceivable that the circuit board is single-layered if no temperature measurement component is integrated on the board.

[0021] In a further embodiment of the invention, a thermally conductive material is arranged between the support element and the laser diode. It is conceivable that the thermally conductive material is a thermal paste or that the support element and / or the housing of the laser diode are coated with a thermally conductive material. This is advantageous because it ensures better heat transfer between the support element and the laser diode.

[0022] Furthermore, it can be provided that the support element consists of a material that has a thermal conductivity of >90 W / mK, preferably >180 W / mK, and particularly preferably >390 W / mK.

[0023] Furthermore, the support element may be made of aluminum, copper, silver, gold, or an alloy containing at least one or more of these metals. It is conceivable that the support element contains at least 50 wt% of one of the metals described above.

[0024] Alternatively, the support element may be made of a composite material containing diamond, graphene, graphite or boron nitride, or the support element may have a coating made of a composite material containing diamond, graphene, graphite or boron nitride.

[0025] It is still conceivable that the support element is made of copper R. 415166

[0026] - 5 -

[0027] In a further embodiment of the solution according to the invention, it can be provided that the laser diode has a power consumption between 0.5 and 10 W and an operating temperature in the range of 0 to 75°C.

[0028] It can be advantageously provided that the laser area of ​​the support element has centering elements and that the laser diode has a heat-emitting surface and the laser area of ​​the support element has a heat-absorbing surface. The centering elements are designed such that the heat-emitting surface of the laser diode is completely and thermally conductively connected to the heat-absorbing surface of the laser area of ​​the support element, with the heat-emitting surface of the laser diode being arranged concentrically to the laser area of ​​the support element by the centering elements. This is advantageous because it enables improved heat dissipation. Furthermore, it is advantageous that the centering elements facilitate simplified assembly.For example, a further bore with a centering pin inserted into the bore or a recess in the support element, designed to be complementary to the housing of the laser diode and into which the laser diode engages during assembly, can be provided as a centering element.

[0029] Brief description of the drawing

[0030] Embodiments of the invention are explained in more detail with reference to the drawings and the following description.

[0031] They show:

[0032] Figure 1 shows a measuring device according to the prior art,

[0033] Figure 2 shows a support element according to the invention,

[0034] Figure 3 shows a support element according to the invention with laser diode and connection pins,

[0035] Figure 4 shows a support element according to the invention with circuit board and connection pins. R. 415166

[0036] - 6 -

[0037] Embodiments of the invention

[0038] Fig. 1 schematically illustrates the setup of a Raman spectroscopy device 10 according to the prior art. This device comprises a high-power laser 14, in particular at least one laser diode 16, as the radiation source 12. This laser is operated within the visible spectral range, particularly within the blue spectral range. A focusing optic 18, shown only schematically here, is connected downstream of the radiation source 12 as depicted in Fig. 1. This optic focuses the laser radiation generated by the at least one laser diode 16 onto a portion of a gas measurement chamber 20. The gas measurement chamber 20 contains a gas 22 or a gas mixture 24. The gas measurement chamber 20 can be part of a bypass line 26 through which a gas flow 66 passes.

[0039] The gas measurement room 20 includes at least one optical access 28 and at least one optical output 30 for the laser radiation generated by the at least one laser diode 16.

[0040] The illustration in Fig. 1 further shows that laser radiation exiting from the at least one optical output 30 enters a radiation absorber 32 in order to avoid scattered light influences.

[0041] From the gas measurement chamber 20, Raman scattered light 34 enters a Raman scattering intensity-enhancing optic 36, which is part of a spectral analysis unit 38. This unit comprises a spectrograph that includes at least one dispersing element, which can be configured, for example, as a grating and at least one prism. Multiple gratings and multiple prisms, as well as combinations of gratings and prisms, can also be provided. The spectral analysis unit 38 also includes a light detector 48, for example, in the form of a CCD camera 50 or a CMOS device and / or a number of receiver diodes. Furthermore, receiver diodes can be arranged within the light detector 48 at the positions corresponding to the Raman wavelengths of the gas(es) under investigation.

[0042] - 7 - are. By means of a suitable design of the bypass 26 or the use of optical windows in the gas measurement room 20, gases 22 or gas mixtures 24 can also be measured in different pressure and temperature ranges.

[0043] In the Raman spectroscopy device 10 shown in Fig. 1, the gas 22 to be measured is illuminated by the laser diode 16, preferably in the visible blue spectral range, through a focusing optic 18. The Raman scattered light 34 is captured by the Raman scattering intensity-enhancing optic 36 and supplied to the spectral analysis unit 38.

[0044] Fig. 2 shows a support element 72 according to the invention with bores 76, wherein the support element 72 has a connection area 74 and a laser area 75.

[0045] As shown in Fig. 3, the laser diode 16 is arranged in a housing 70 and connected to the support element 72 in the laser area 75 through the bores 76 by means of pins 71 shown in Fig. 4. The circuit board 73 is also connected to the support element 72 via the bores 76 and by means of pins 71.

[0046] As shown in both Fig. 3 and Fig. 4, the support element 72 also has bores 76 in the connection area 74 through which connection pins 77 are guided, the support element 72 being connected to the schematically depicted Raman spectroscopy device 30 by means of the connection pins 77. The connection pins 77 can also be understood to be cables that function as connection pins.

[0047] Fig. 4 shows the circuit board 73 as it is connected to the carrier element 72 by means of the pins 71 and the connection pins 77.

[0048] As shown in Figs. 3 and 4, pins 71 connect the carrier element 72 to the housing 70 of the laser diode 16 and to the circuit board 73. Connection pins 77 connect the carrier element 72 to the Raman spectroscopy device 30 and the circuit board 73. The laser diode 16 can be electrically connected via pins 71.

Claims

R. 415166 - 8 - Claims 1. Raman spectroscopy device (30) for measuring the concentration of a gas (22) with a gas measurement chamber (20) for the gas (22), which has one or more optical inlets (28) and one or more optical outlets (80), with a gas supply line (4) for supplying the gas (22) into the gas measurement chamber (20, 56) during the concentration measurement, wherein the Raman spectroscopy device (30) comprises a high-power laser (14), in particular a laser diode (16), which is configured for focused illumination of the gas (22) in the gas measurement chamber (20, 56), wherein the laser diode (16) is arranged in a housing (70), wherein the laser diode (16) is electrically contactable via pins (71), wherein the Raman spectroscopy device (30) comprises a collecting optical system (36) with at least one filter and at least one aperture and a spectral analysis unit (38) comprising and wherein the Raman spectroscopy device (30) Raman scattered light (34,62) through the collecting optical system (36) with at least one filter and at least one aperture of the spectral analysis unit (38), characterized in that the Raman spectroscopy device (30) has a support element (72) and a circuit board (73), wherein the support element (72) has a connection area (74) and a laser area (75), wherein the support element (72) has bores (76) in the laser area (75) through which the housing (70) of the laser diode (16) and the circuit board (73) are connected to the support element (72) by means of the pins (71), wherein the support element (72) has bores (76) in the connection area (74) which serve to fasten the support element (72) in the Raman spectroscopy device (30). R. 415166 - 9 - 2. Measuring device according to claim 1, characterized in that the housing (70) in which the laser diode (16) is arranged is soldered to the circuit board (73).

3. Measuring device according to claim 1 or 2, characterized in that the circuit board (73) is multilayered, that the circuit board (73) has a component for temperature measurement which is thermally conductively connected to the carrier element (72), in particular an SMD or a THT component or an NTC element and / or a Pt100 or a quartz crystal / oscillator.

4. Measuring device according to one of the preceding claims, characterized in that a thermally conductive material is arranged between the support element (72) and the laser diode (16), wherein the thermally conductive material is a thermal paste or wherein the support element (72) and / or the housing (70) of the laser diode (16) are coated with a thermally conductive material.

5. Measuring device according to one of the preceding claims, characterized in that the support element (72) consists of a material having a thermal conductivity of >90 W / mK, preferably >180 W / mK, particularly preferably >390 W / mK.

6. Measuring device according to one of the preceding claims characterized in that the support element (72) is made of aluminium or copper or silver or gold or of an alloy comprising at least one or more of these metals.

7. Measuring device according to one of claims 1 to 5, characterized in that the support element (72) is formed from a composite material with proportions of diamond, graphene, graphite or boron nitride or that the support element (72) has a coating made of a composite material with proportions of diamond, graphene, graphite or boron nitride. R. 415166 - 10 - 8. Measuring device according to one of the preceding claims, characterized in that the support element (72) is made of copper.

9. Measuring device according to one of the preceding claims, characterized in that the laser diode (16) has a power consumption between 0.5 - 10 W and an operating temperature in the range of 0 - 75°C.

10. Measuring device according to one of the preceding claims, characterized in that the laser area (75) of the carrier element (72) has centering elements, that the laser diode (16) has a heat-emitting surface and the laser area (75) of the carrier element (72) has a heat-absorbing surface, that the centering elements are designed such that the heat-emitting surface of the laser diode (16) is completely and thermally conductively connected to the heat-absorbing surface of the laser area (75) of the carrier element (72), wherein the heat-emitting surface of the laser diode (16) is arranged concentrically to the laser area (75) of the carrier element (72) by the centering elements.

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