Raman Spectrometer

Abstract

Raman spectrometer with a high-power laser diode (16) for emitting laser light (31), with a measuring chamber (20) through which a gas (22) flows, with first focusing means (18) for focusing the laser light (31) into the measuring chamber (20) and with a spectrally resolving detector (70) and with second focusing means (21) for imaging Raman scattered light (34) generated in the measuring chamber (20) into the spectrally resolving detector (70), with a temperature sensor (55) for measuring the temperature of the high-power laser diode (16), with an active electrical temperature control element (50) for temperature control of the high-power laser diode (16), with a first power supply (131) for supplying current to the high-power laser diode (16), with a second power supply (132) for supplying current to the temperature control element and with a monitoring unit (140) for monitoring the temperature of the high-power laser diode (16).

Description

State of the art

[0001] Raman spectrometers are already known from the prior art, for example from DE 10 2021 107 229 A1 or EP 3 748 339 B1. They are based on the principle that focused laser light is inelastically scattered by the molecules of a gas in a measuring cell, producing so-called Raman scattered light. They further rely on the spectrally resolved detection of this Raman scattered light. In this way, properties of the gas in the measuring cell can be determined. Disclosure of the invention

[0002] The invention relates to a Raman spectrometer with a high-power laser diode for emitting laser light, with a measuring chamber through which a gas flows, with first focusing means for focusing the laser light into the measuring chamber and with a spectrally resolving detector, and with second focusing means for imaging Raman scattered light generated in the measuring chamber into the spectrally resolving detector, with a temperature sensor for measuring the temperature of the high-power laser diode, with an active electrical temperature control element for temperature control of the high-power laser diode, with a first power supply for supplying the high-power laser diode with current, and with a second power supply for supplying the temperature control element with current.

[0003] The invention provides that the Raman spectrometer also includes a monitoring unit for monitoring the temperature of the high-power laser diode. For example, the monitoring unit may include a comparator configured to detect a temperature signal from the temperature sensor for measuring the temperature of the high-power laser diode, compare it with a predetermined laser temperature threshold, and interrupt the power supply to the high-power laser diode as soon as its temperature exceeds the predetermined laser temperature threshold.

[0004] This protects the high-power laser diode from damage even if a malfunction occurs, for example of the temperature control element, or if the Raman spectrometer is operated outside its permissible operating conditions, for example at an impermissibly high ambient temperature, so that the temperature control element is unable to keep the temperature of the high-power laser diode within the intended temperature limits.

[0005] A high-power laser diode can be a laser diode capable of emitting light with an optical power of at least one watt. For example, a high-power laser diode could be one that emits light with a central wavelength in the blue spectral range, such as between 380 nm and 550 nm, particularly between 440 nm and 460 nm.

[0006] The high-power laser diode can in particular be a "free-running" laser diode, meaning that measures to stabilize the wavelength of its emission, such as frequency-selective feedback to external components, visual Bragg grating, master-slave operation or similar, can be dispensed with.

[0007] The temperature sensor in this case could be an NTC element (negative temperature coefficient element). The active electrical temperature control element for the high-power laser diode could be a Peltier element.

[0008] It has proven advantageous to further develop the invention by integrating the first power supply for the high-power laser diode, the second power supply for the temperature control element, and the monitoring unit for monitoring the temperature of the high-power laser diode into a single driver unit. The driver unit can be an assembly enclosed in a driver unit housing, which, for example, is itself arranged within a housing of the Raman spectrometer, which may differ at least partially from the driver unit housing.

[0009] Alternatively or additionally, it is also possible to integrate the first power supply for the high-power laser diode, the second power supply for the temperature control element, and the monitoring unit for monitoring the temperature of the high-power laser diode onto a single circuit board. This circuit board can be located within the driver unit described above. However, it can also directly constitute the driver unit itself.

[0010] In a further development of the invention, the first power supply for the high-power laser diode and / or the second power supply for the temperature control element may include a transistor for providing current. The transistor may, for example, be a MOSFET (metal-oxide-semiconductor field-effect transistor), although other types of transistors are also suitable. Within the scope of the present invention, the transistor / MOSFET may, for example, be suitable for providing currents of, for example, 4 amperes at, for example, 20 volts. Of course, several transistors / MOSFETs may also be provided for this purpose.

[0011] In a further development of the invention, it is provided that the Raman spectrometer includes a temperature sensor for measuring the temperature of the transistor and that the monitoring unit includes a second comparator which is configured to detect a temperature signal from the temperature sensor for measuring the temperature of the transistor, compare it with a predetermined limit value of the transistor temperature and interrupt the power supply to the high-power laser diode and / or interrupt the power supply to the temperature control element as soon as the temperature of the transistor exceeds the predetermined limit value of the transistor temperature.

[0012] This protects the transistor from damage caused by excessively high temperatures.

[0013] It may be stipulated that the transistor temperature limit is higher than the laser temperature limit. For example, the transistor temperature limit could be 70°C to 110°C, e.g., 90°C, and the laser temperature limit could be 30°C to 60°C, e.g., 45°C.

[0014] The transistor can be implemented as a component with pins protruding from a transistor package. Alternatively, the transistor can be implemented as a component with three pins protruding from a side face of a flat transistor package.

[0015] The transistor can be attached to the circuit board via its pins, for example, either laterally or when viewed from above. Alternatively, the transistor can be designed to protrude laterally beyond the circuit board and have its housing in contact with the housing of the Raman spectrometer for thermal coupling, particularly with the largest possible surface area of ​​the housing in contact with the housing of the Raman spectrometer. This ensures efficient passive cooling of the transistor.

[0016] In particular, to further improve passive cooling, the transistor is designed so that its housing rests against an inner side of the Raman spectrometer housing, while a heat sink with cooling fins is arranged opposite on the outer side of the Raman spectrometer housing to effectively dissipate the heat generated by the transistor and introduced into the Raman spectrometer housing to the environment of the Raman spectrometer.

[0017] To further simplify this, it can be provided that the circuit board has a lateral recess when viewed from above, and that the transistor is arranged at least partially, for example predominantly in relation to its area when viewed from above, in the lateral recess.

[0018] In further training, it is preferred that the Raman spectrometer has a main board that is different from the circuit board, and that there are electrical connections between the circuit board and the main board that are bundled in a single cable.

[0019] The invention also includes operating methods, software and associated computer programs related to the Raman spectrometer according to the invention.

[0020] For example, a standardized software enables simplifications in the operation of the Raman spectrometer according to the invention, as well as functional extensions and additional functions. For instance, setting up and operating the spectrometer, preparing the spectrometer, and operating and monitoring a measurement program are significantly simplified by a specific software architecture. Furthermore, monitoring of operating parameters of the Raman spectrometer, such as thermal stability and overheating protection, is enabled. In particular, the circuit board provides enhanced and differentiated overheating protection for the high-power laser diode and the detector.

[0021] In further training, overheating protection is possible, which, instead of or in addition to a complete interruption of the power supply, provides for operation with a reduced current under certain conditions.

[0022] In a further training course, it is conceivable to control multiple setpoints, for example, for the temperature of the high-power diode laser. These setpoints could be selected based on factors such as the ambient temperature. Furthermore, a correction function, for example, to compensate for the aging of the high-power laser diode and the detector, could be provided and activated via the circuit board. Individual evaluation algorithms could be assigned to the temperature setpoints of the high-power diode laser, allowing conclusions to be drawn about the properties of the gas from the spectra recorded by the detector.

[0023] The single figure in the application shows an exemplary embodiment of the present invention.

[0024] A Raman spectrometer 30 includes a high-power laser diode 16 for emitting laser light 31. The high-power laser diode 16 emits spatially divergent laser light 31. The spatial properties divergence and beam diameter of the laser light 31 typically differ in two beam profile directions perpendicular to the propagation direction of the laser light 31, which can be compensated for by suitable cylindrical optics, which will not be discussed further here.

[0025] The Raman spectrometer 30 has a measuring chamber 20 through which a gas 22 flows - perpendicular to the plane of the drawing in the figure.

[0026] The Raman spectrometer 30 has first focusing means 18 for focusing the laser light 31 into the measuring chamber 20. The first focusing means 18 include, for example, a first optic 18.1 that transforms the divergent beam into a collimated beam, which has, for example, an approximately round or approximately square beam profile. The first optic 18.1 of the first focusing means 18 can, for example, include the cylindrical optic mentioned above.

[0027] The first focusing means 18 include, for example, a second optical element 18.2 that transforms the collimated beam into a convergent beam which is focused in the measuring chamber 20. The second optical element 18.2 can, for example, be a spherical plano- or biconvex lens.

[0028] In the collimated beam, i.e. between the first optics 18.1 and the second optics 18.2 of the first focusing means 18, a short-pass filter 19 is arranged in the beam path in the example.

[0029] In the measuring chamber 20, Raman scattering light 34, which has characteristic wavelengths, is produced by the inelastic interaction of the molecules of the gas 22 with the focused laser light 31.

[0030] The part of the laser light 31 that is not deflected by interaction with the molecules of the gas 22 is absorbed in the example in a beam absorber 32, which is arranged behind the measuring chamber 20 in the direction of propagation of the laser light 31.

[0031] The Raman spectrometer 30 comprises a detector 70 that is capable of quantitatively, spectrally resolved, and dynamically analyzing incident light. For example, it includes a grating spectrometer and a CCD detector.

[0032] The Raman spectrometer 30 further comprises second focusing means 21 for imaging Raman scattered light 34 generated in the measuring chamber 20 into the spectrally resolving detector 70. For example, the second focusing means 21 comprise a first optic 21.1, which collimates Raman scattered light 34 generated in the measuring chamber 20, and a second optic 21.2, which transforms the collimated light into a convergent beam and images it into the detector 70. The first and second optics 21.1, 21.2 of the second focusing means 21 can each be, for example, a spherical plano- or biconvex lens.

[0033] In the collimated beam, i.e. between the first optics 21.1 and the second optics 21.2 of the second focusing means 21, a long-pass filter 45 is arranged in the beam path in the example.

[0034] The Raman spectrometer further comprises a temperature sensor 55 for measuring the temperature of the high-power laser diode 16 and an active electrical temperature control element 50 (e.g., a Peltier element) for temperature control of the high-power laser diode 16. A control loop for regulating the temperature of the high-power laser diode 16 can be implemented with the temperature sensor 55 as the actual value sensor and with the temperature control element 50 as the actuator. A control algorithm can be implemented as a PI controller or as a PID controller, for example, as a digital controller, such as in a microprocessor 150, which is arranged on a main board 110 of the Raman spectrometer 30.

[0035] For controlling the Raman spectrometer 30, in addition to the main board 110, a board 120 is provided as a driver unit 121, which, together with all the aforementioned optical components, is arranged in a housing 100 of the Raman spectrometer 30. The board 120 is connected to the main board 110 via electrical connections 82, which can be combined in a single cable 84.

[0036] The circuit board 120 comprises a first power supply 131 for supplying current to the high-power laser diode 16, a second power supply 132 for supplying current to a temperature control element 50 (e.g., a Peltier element) associated with the high-power laser diode 16, and a monitoring unit 140 for monitoring the temperature of the high-power laser diode 16. For this purpose, the monitoring unit 140 includes a comparator 141, which is configured to detect a temperature signal from the temperature sensor 55 for measuring the temperature of the high-power laser diode 16, compare it with a predetermined limit value for the laser temperature, and control the first power supply 131 to interrupt the power supply to the high-power laser diode 16 as soon as the temperature of the high-power laser diode 16 exceeds the predetermined limit value for the laser temperature.

[0037] The circuit board 120 can have a recess 125 on its side when viewed from above, in which a transistor 123 (e.g., MOSFET) is at least partially arranged to provide power to the first power supply 131 and / or the second power supply 132. The transistor 123 is fixed to the circuit board 120 via its three pins 123.1, 123.2, and 123.3, for example, by a soldered connection. The housing 123.4 of the transistor 123 is located on the inside 100a of the housing 100 of the Raman spectrometer 30 for thermal coupling, while opposite, on the outside 100b of the housing 100 of the Raman spectrometer 30, a heat sink 80, which has cooling fins, is arranged to effectively dissipate the heat generated by the transistor 123 and introduced into the housing 100 of the Raman spectrometer 30 to the environment.

[0038] Furthermore, a temperature sensor 56 is provided for measuring the temperature of the transistor 123, and the monitoring unit 140 is provided to include a second comparator 142, which is configured to detect a temperature signal from the temperature sensor 56 for measuring the temperature of the transistor 123, to compare it with a predetermined limit value of the transistor temperature, and to interrupt the power supply to the high-power laser diode 16 and / or to interrupt the power supply to the temperature control element 50 as soon as the temperature of the transistor 123 exceeds the predetermined limit value of the transistor temperature. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2021 107 229 A1

[0001] EP 3 748 339 B1

[0001]

Claims

[1] Raman spectrometer with a high-power laser diode (16) for emitting laser light (31), with a measuring chamber (20) through which a gas (22) flows, with first focusing means (18) for focusing the laser light (31) into the measuring chamber (20) and with a spectrally resolving detector (70) and with second focusing means (21) for imaging Raman scattered light (34) generated in the measuring chamber (20) into the spectrally resolving detector (70), with a temperature sensor (55) for measuring the temperature of the high-power laser diode (16), with an active electrical temperature control element (50) for temperature control of the high-power laser diode (16), with a first power supply (131) for supplying current to the high-power laser diode (16), with a second power supply (132) for supplying current to the temperature control element and with a monitoring unit (140) for monitoring the temperature of the High-power laser diode (16). [2] Raman spectrometer according to claim 1,characterized by , that the monitoring unit (140) includes a comparator (141) which is configured to detect a temperature signal from the temperature sensor (55) for measuring the temperature of the high-power laser diode (16), to compare it with a predetermined limit value of the laser temperature and to interrupt the power supply to the high-power laser diode (16) as soon as the temperature of the high-power laser diode (16) exceeds the predetermined limit value of the laser temperature. [3] Raman spectrometer according to claim 1 or 2, wherein the first power supply (131) for supplying the high-power laser diode (16) with current, the second power supply (132) for supplying the temperature control element with current and the monitoring unit (140) for monitoring the temperature of the high-power laser diode (16) are integrated in a single driver unit (121). [4] Raman spectrometer according to any one of the preceding claims, characterized by, that the first power supply (131) for supplying current to the high-power laser diode (16) and / or the second power supply (132) for supplying current to the temperature control element (50) includes a transistor (123) for providing current, that the Raman spectrometer (30) includes a temperature sensor (56) for measuring the temperature of the transistor (123), and that the monitoring unit (140) includes a second comparator (142) which is configured to detect a temperature signal from the temperature sensor (56) for measuring the temperature of the transistor (123), compare it with a predetermined limit value of the transistor temperature, and interrupt the power supply to the high-power laser diode (16) and / or interrupt the power supply to the temperature control element (50) as soon as the temperature of the transistor (123) exceeds the predetermined limit value of the transistor temperature. [5] Raman spectrometer according to claim 2 and simultaneously according to claim 4, characterized by , that the limit of the transistor temperature is higher than the limit of the laser temperature. [6] Raman spectrometer according to any one of the preceding claims, characterized by , that the first power supply (131) for supplying the high-power laser diode (16) with current, the second power supply (132) for supplying the temperature control element (50) with current and the monitoring unit (140) for monitoring the temperature of the high-power laser diode (16) are integrated on a single circuit board (120). [7] Raman spectrometer according to claim 4 or 5 and simultaneously according to claim 6, characterized by , that the transistor (123) is implemented as a component which is fixed to or on the circuit board (120) via its pins (123.1, 123.2, 123.3) and whose housing (123.4) is in contact with a housing (100) of the Raman spectrometer (30) for thermal coupling. [8] Raman spectrometer according to claim 7, characterized by , that the transistor (123) with its housing (123.4) is in contact with an inner side (100i) of the housing (100) of the Raman spectrometer (30), while opposite on the outer side (100a) of the housing of the Raman spectrometer (30) a heat sink (80) having cooling fins is arranged to effectively dissipate the heat generated by the transistor (123) and introduced into the housing (100) of the Raman spectrometer (30). [9] Raman spectrometer according to claim 7 or 8, characterized by , that the circuit board (120) has a lateral recess (125) in plan view and the transistor (123) is at least partially arranged in the lateral recess (125). [10] Raman spectrometer according to one of claims 7, 8 or 9, characterized by, that the housing (100) of the Raman spectrometer (30) contains the high-power laser diode (16), the measuring chamber (20), the first focusing means (18) and the second focusing means (21) and the detector (70), the first power supply (131), the second power supply (132) and the monitoring unit (140). [11] Raman spectrometer according to any one of the preceding claims, characterized by , that it has a main board (110) and that there are electrical connections (82) between the board (120) and the main board (110), which are grouped together in a single cable (84).

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