A Thermopile Sensor for Micro Laser Power

Abstract

The invention discloses a micro-laser power thermopile sensor, comprising an aluminum alloy substrate, a low thermal conductivity film, a copper plating layer, an insulating layer, a thermopile sensitive layer, an absorber and a copper pressing ring; the aluminum alloy substrate is a circular step structure, the low thermal conductivity film and the aluminum alloy substrate form concentric circles, the copper plating layer is arranged on the upper part of the low thermal conductivity film, the insulating layer is arranged on the upper part of the copper plating layer in a disc shape, the thermopile sensitive layer is arranged on the upper part of the insulating layer, the absorber is arranged in the middle of the thermopile sensitive layer, and the copper pressing ring is arranged on the upper part of the insulating layer; the film pressing ring structure adopted in the invention reduces the processing difficulty; at the same time, due to the adoption of the low thermal conductivity film material, most of the heat is concentrated on the thermopile sensitive layer, the temperature difference between the cold end and the hot end of the thermopile is increased, so that the output voltage signal is increased, and the sensitivity of the sensor when measuring micro power is improved.

Description

Technical Field

[0001] The invention relates to the technical field of laser power measurement, and in particular to a micro laser power thermopile sensor. Background Art

[0002] With the widespread application of lasers, accurately measuring laser power is crucial in industry, medicine, communications and military fields.

[0003] In the prior art, laser power meters are usually used to measure the power of lasers. Laser power meters are generally composed of a power probe with a built-in sensor and a display component. According to different principles, sensors can be divided into photoelectric sensors and thermoelectric sensors. The principle of photoelectric sensors is to directly convert light energy into current or voltage signals through photodiodes to characterize the size of laser power. Although photoelectric sensors have a shorter response time and a higher response frequency, their applicable wavelengths are limited. Thermoelectric sensors usually use a symmetrically arranged thermopile to measure the temperature gradient formed in the matrix by the laser energy absorbed by the absorber, thereby outputting an electrical signal for measurement. The response time of thermoelectric probes is relatively long, but the spectral measurement range is wide, and can be used from ultraviolet to far infrared bands, so they are more widely used.

[0004] Existing thermopile sensors are usually composed of an aluminum alloy substrate, an absorber, an insulating layer, a sensitive layer, and a terminal. The thermopile sensitive layer is located on the back of the absorber. When existing thermoelectric sensors are used for micro-power measurements, in order to improve the response and output voltage, the aluminum alloy substrate of the absorber part in the middle of the substrate needs to be processed to 0.3 mm or even thinner. In order to accurately measure, the overall dimensional error of the middle part must be controlled within a very small range, and the processing is difficult. In addition, the material of the middle part is also aluminum alloy. The temperature gradient generated by the micro-power laser energy is very small, and it is difficult to output a large electrical signal. Therefore, when measuring a small power, the signal needs to be amplified by a very large multiple, which is prone to distortion and affects the measurement accuracy.

[0005] Therefore, a tiny laser power thermopile sensor has become an urgent problem to be solved. Summary of the invention

[0006] The technical problem to be solved by the present invention is that the thermopile sensor in the prior art is difficult to process, has a small output voltage signal, and has low measurement accuracy when measuring tiny power.

[0007] In order to solve the above technical problems, the technical solution provided by the present invention is: a micro laser power thermopile sensor, comprising an aluminum alloy substrate, a low thermal conductivity film, a copper plating layer, an insulating layer, a thermopile sensitive layer, an absorber and a copper pressing ring;

[0008] The aluminum alloy substrate is a circular step structure, the aluminum alloy substrate includes a first step and a second step, the first step and the second step have the same outer diameter, and the second step has an inner diameter greater than the first step; the low thermal conductivity film is in the shape of a disc and has a diameter slightly smaller than the inner diameter of the second step, the low thermal conductivity film is placed on the first step and forms a concentric circle with the aluminum alloy substrate, the outer circle of the copper plating layer is in the shape of a circular ring, the center is in the shape of a disc, the diameter of the center disc is slightly greater than the diameter of the absorber, the copper plating layer is arranged on the upper part of the low thermal conductivity film, the insulating layer is in the shape of a disc and arranged on the upper part of the copper plating layer, the thermopile sensitive layer is arranged on the upper part of the insulating layer, the two ends of the thermopile sensitive layer are located at the outer circle and inner circle of the copper plating layer, above the insulating layer, the absorber is arranged in the middle of the thermopile sensitive layer, the copper pressing ring is arranged on the upper part of the insulating layer, the inner diameter of the copper pressing ring is greater than the outer diameter of the sensitive layer, the copper pressing ring does not contact the sensitive layer, and the copper pressing ring and the aluminum alloy substrate adopt an interference fit.

[0009] Furthermore, the thermopile sensitive layer includes a thermopile positive electrode layer and a thermopile negative electrode layer, and the thermopile negative electrode layer and the thermopile positive electrode layer are symmetrical to each other and closely connected.

[0010] Furthermore, a pure silver sheet is provided on the thermopile sensitive layer, and a terminal penetrating the aluminum alloy substrate is provided at the lower part of one end of the pure silver sheet, and the terminal comprises an insulating seat and a copper needle penetrating the insulating seat.

[0011] Furthermore, the copper plating layer and the low thermal conductivity film are provided with a first through hole that matches the insulating seat.

[0012] Furthermore, the insulating seat is a polytetrafluoroethylene insulating seat.

[0013] Furthermore, the low thermal conductivity film is made of nylon.

[0014] A laser power meter with a built-in thermopile sensor comprises an aluminum alloy front cover, an aluminum alloy body, a thermopile sensor and an aluminum alloy back cover, wherein the thermopile sensor is any of the above-mentioned micro laser power thermopile sensors; the aluminum alloy body is arranged on the upper part of the aluminum alloy back cover, a circular sink is provided on the upper part of the aluminum alloy body, the thermopile sensor is arranged inside the circular sink, a second through hole penetrating the aluminum alloy body is provided in the middle part of the aluminum alloy body, and the aluminum alloy front cover is arranged on the upper part of the aluminum alloy body and a light hole penetrating the aluminum alloy front cover is provided in the middle part.

[0015] Furthermore, the aluminum alloy front cover and the aluminum alloy rear cover are each provided with a plurality of third through holes penetrating therethrough, the aluminum alloy body is provided with threaded holes corresponding to the positions of the third through holes, countersunk screws are provided in the threaded holes, and the countersunk screws fix the aluminum alloy front cover, the aluminum alloy body, the thermopile sensor and the aluminum alloy rear cover into a whole.

[0016] Furthermore, the aluminum alloy body is provided with a top screw washer, an M4 hexagonal top screw used in conjunction with the top screw washer, and a shielding wire arranged on one side of the aluminum alloy body.

[0017] The advantages of the present invention over the prior art are as follows: the thin film pressing ring structure adopted in the present invention reduces the difficulty of processing; at the same time, due to the use of a thin film material with a low thermal conductivity coefficient, most of the heat is concentrated on the sensitive layer of the thermopile, thereby increasing the temperature difference between the cold end and the hot end of the thermopile, thereby increasing the output voltage signal and improving the sensitivity of the sensor when measuring small power. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of a micro laser power thermopile sensor of the present invention.

[0019] Figure 2 It is a partial enlarged view of a micro laser power thermopile sensor of the present invention.

[0020] Figure 3 It is a cross-sectional view of a micro laser power thermopile sensor of the present invention.

[0021] Figure 4 The present invention is a schematic structural diagram of a laser power meter with a built-in thermopile sensor.

[0022] Figure 5 The present invention is a schematic diagram of a shielding wire fixing structure of a laser power meter with a built-in thermopile sensor.

[0023] As shown in the figure: 1. Aluminum alloy substrate, 2. Low thermal conductivity film, 3. Copper plating, 4. Insulating layer, 5. Thermopile sensitive layer, 6. Absorber, 7. Copper pressure ring, 8. First step, 9. Second step, 10. Thermopile positive electrode layer, 11. Thermopile negative electrode layer, 12. Pure silver sheet, 13. Insulating seat, 14. Copper needle, 15. First through hole, 16. Aluminum alloy front cover, 17. Aluminum alloy body, 18. Thermopile sensor, 19. Aluminum alloy back cover, 20. Round sinker, 21. Second through hole, 22. Light hole, 23. Third through hole, 24. Threaded hole, 25. Countersunk screw, 26. Shielding wire, 27. Top screw washer, 28. M4 hexagonal top screw, 29. Terminal. DETAILED DESCRIPTION

[0024] A low-power laser thermopile sensor of the present invention is further described in detail below with reference to the accompanying drawings.

[0025] Combined with Figure 1-4 , the working principle of the present invention:

[0026] The substrate is made of aluminum alloy as a heat-conducting substrate, and a low thermal conductivity film 2 (such as nylon 66) is used in the middle as a support. It is fixed in the aluminum substrate through an interference fit with a copper pressure ring 7. When measuring slightly larger power, it can also be replaced with an aluminum foil film using the same structure. The copper layer is plated in the middle and outer rings of the nylon film using a vacuum coating process. The middle copper coating 3 can improve the surface uniformity of the absorber 6 and reduce the error caused by the light spot deviating from the center. The absorber 6 is sprayed on the middle copper coating 3 by a plasma spraying process, and its diameter is slightly smaller than the middle copper coating 3. The outer copper coating 3 and the copper pressure ring 7 are in close contact, which plays a role in heat transfer. The insulating layer 4 plays the role of insulation and improving the bonding force of the thermopile sensitive layer 5. The thermopile sensitive layer 5 is arranged on the insulating layer 4 and is arranged on the same surface as the absorber 6. Its cold end and hot end are located at the outer copper plating layer 3 and the inner copper plating layer 3 respectively. Since the middle support part adopts a nylon film with low thermal conductivity, the heat generated by the laser energy absorbed by the absorber 6 can only be conducted through the thermocouples themselves that make up the thermopile, which will generate a larger voltage signal than the existing design, making it more accurate when measuring tiny power. The thermopile sensitive layer 5 and the terminal 29 are connected by a pure silver sheet 12 through conductive silver glue. The pure silver sheet 12 is located on the same side of the sensitive layer, and a notch is set on the copper pressure ring 7 so that the pure silver sheet 12 can be connected to the bottom of the copper needle 14 in the terminal 29. The top of the copper needle 14 is on the back of the substrate and is connected to the high temperature resistant wire to output a voltage signal.

[0027] The aluminum alloy front cover 16 is mounted on the aluminum alloy body 17 by countersunk screws 25, the thermopile sensor 18 is pressed by the front cover on the circular sink 20 inside the body, the rear cover is also mounted on the body by countersunk screws 25, and the terminal 29 and the output shielding wire 26 are connected by high temperature resistant wires. By replacing different cooling components, such as larger heat sinks, fan cooling, and water cooling, power meters with different maximum measurement powers can be made. Depending on the usage scenario, a signal conditioning circuit can also be built in. The signal conditioning circuit includes: ultra-low noise power supply, pre-stage instrument amplifier, active low-pass filter, double-T notch filter, main amplifier, voltage follower, and calibration circuit.

[0028] The precision power supply provides the positive and negative power supplies required by the signal conditioning circuit. The pre-stage instrument amplifier amplifies the tiny electrical signal output by the sensor at a low multiple, and the amplification multiple is determined by a fixed precision resistor, which avoids the error caused by the change of the sensor internal resistance due to the change of the sensor substrate temperature. The active low-pass filter and double T notch filter can effectively filter high-frequency interference and 50Hz power frequency interference. The main amplifier amplifies the filtered signal and then outputs it through the follower and calibration circuit.

[0029] Combined with Figure 1-5 , the present invention is introduced in detail.

[0030] A micro laser power thermopile sensor, comprising an aluminum alloy substrate 1, a low thermal conductivity film 2, a copper plating layer 3, an insulating layer 4, a thermopile sensitive layer 5, an absorber 6 and a copper pressing ring 7;

[0031] The aluminum alloy substrate 1 is a circular step structure, and the aluminum alloy substrate 1 includes a first step 8 and a second step 9. The outer diameters of the first step 8 and the second step 9 are the same, and the inner diameter of the second step 9 is larger than the inner diameter of the first step 8. The low thermal conductivity film 2 is in the shape of a disc and its diameter is slightly smaller than the inner diameter of the second step 9. The low thermal conductivity film 2 is placed on the first step 8 and is concentric with the aluminum alloy substrate 1. The outer circle of the copper plating layer 3 is in the shape of a circular ring, and the center is in the shape of a disc. The diameter of the center disc is slightly larger than the diameter of the absorber 6. The copper plating layer 3 is arranged on the upper part of the low thermal conductivity film 2, the insulating layer 4 is arranged on the upper part of the copper plating layer 3 in the shape of a disc, the thermopile sensitive layer 5 is arranged on the upper part of the insulating layer 4, the two ends of the thermopile sensitive layer 5 are located at the outer circle and inner circle positions of the copper plating layer 3, above the insulating layer 4, the absorber 6 is arranged in the middle of the thermopile sensitive layer 5, the copper pressing ring 7 is arranged on the upper part of the insulating layer 4, the inner diameter of the copper pressing ring 7 is larger than the outer diameter of the sensitive layer, the copper pressing ring 7 does not contact the sensitive layer, and the copper pressing ring 7 and the aluminum alloy substrate 1 adopt an interference fit.

[0032] The thermopile sensitive layer 5 includes a thermopile positive electrode layer 10 and a thermopile negative electrode layer 11 . The thermopile negative electrode layer 11 and the thermopile positive electrode layer 10 are symmetrical to each other and closely connected.

[0033] A pure silver sheet 12 is disposed on the thermopile sensitive layer 5 . A terminal 29 penetrating the aluminum alloy substrate 1 is disposed at the lower part of one end of the pure silver sheet 12 . The terminal 29 includes an insulating seat 13 and a copper needle 14 penetrating the insulating seat 13 .

[0034] The copper plating layer 3 and the low thermal conductivity film 2 are provided with a first through hole 15 that matches the insulating seat 13 .

[0035] The insulating seat 13 is a polytetrafluoroethylene insulating seat 13 .

[0036] The low thermal conductivity film 2 is made of nylon.

[0037] A laser power meter with a built-in thermopile sensor comprises an aluminum alloy front cover 16, an aluminum alloy body 17, a thermopile sensor 18 and an aluminum alloy rear cover 19, wherein the thermopile sensor 18 is any of the above-mentioned small laser power thermopile sensors 18; the aluminum alloy body 17 is arranged on the upper part of the aluminum alloy rear cover 19, a circular sink 20 is provided on the upper part of the aluminum alloy body 17, the thermopile sensor 18 is arranged inside the circular sink 20, a second through hole 21 penetrating the aluminum alloy body 17 is provided in the middle part of the aluminum alloy body 17, the aluminum alloy front cover 16 is arranged on the upper part of the aluminum alloy body 17 and a light hole 22 penetrating the aluminum alloy front cover 16 is provided in the middle part.

[0038] The aluminum alloy front cover 16 and the aluminum alloy rear cover 19 are each provided with a plurality of third through holes 23 penetrating therethrough, and the aluminum alloy body 17 is provided with threaded holes 24 corresponding to the positions of the third through holes 23, and countersunk screws 25 are provided in the threaded holes 24, and the countersunk screws 25 fix the aluminum alloy front cover 16, the aluminum alloy body 17, the thermopile sensor 18 and the aluminum alloy rear cover 19 into a whole.

[0039] The aluminum alloy body 17 is provided with a top screw washer 27 , an M4 hexagonal top screw 28 used in conjunction with the top screw washer 27 , and a shielding wire 26 arranged on one side of the aluminum alloy body 17 .

[0040] The specific implementation process of a micro laser power thermopile sensor of the present invention is as follows:

[0041] Example 1: The specific implementation process of the thermopile sensor is as follows:

[0042] The aluminum alloy substrate 1 is a heat-conducting substrate, and a low thermal conductivity film 2 is used as a support in the middle. It is fixed in the aluminum alloy substrate 1 through an interference fit with a copper pressing ring 7. The copper layer is plated in the middle and outer ring of the nylon film by a vacuum coating process. The absorber 6 is sprayed on the middle copper plating layer 3 by a plasma spraying process, and its diameter is slightly smaller than the middle copper plating layer 3. The outer ring copper plating layer 3 and the copper pressing ring 7 are in close contact. The thermopile sensitive layer 5 is arranged on the insulating layer 4 and is arranged on the same surface as the absorber 6. Its cold end and hot end are respectively located at the positions of the outer ring copper plating layer 3 and the inner ring copper plating layer 3. The sensitive layer and the copper needle 14 are connected by a pure silver sheet 12 through conductive silver glue. The pure silver sheet 12 is located on the same side of the thermopile sensitive layer 5. A notch is set on the copper pressing ring 7 so that the pure silver sheet 12 can be connected to the bottom of the copper needle 14 in the terminal 29. The top of the copper needle 14 is on the back of the substrate and is connected to the high-temperature resistant wire to output a voltage signal.

[0043] Embodiment 2: The specific implementation process of the laser power meter is as follows:

[0044] The aluminum alloy front cover 16 is mounted on the aluminum alloy body 17 by countersunk screws 25, the thermopile sensor 18 is pressed by the aluminum alloy front cover 16 on the circular sink 20 inside the body, the aluminum alloy rear cover 19 is also mounted on the body by countersunk screws 25, and the copper needle 14 and the output shielding wire 26 are connected by high temperature resistant wires. By replacing different cooling components, such as larger heat sinks, fan cooling, and water cooling, power meters with different maximum measurement powers can be made. Depending on the usage scenario, a signal conditioning circuit can also be built in.

[0045] The present invention and its embodiments are described above, which is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. In short, if ordinary technicians in the field are inspired by it and design structural methods and embodiments similar to the technical solution without creativity without departing from the purpose of the invention, they should all fall within the protection scope of the present invention.

Claims

1. A low-power laser thermopile sensor, characterized in that: The invention comprises an aluminum alloy substrate (1), a low thermal conductivity film (2), a copper plating layer (3), an insulating layer (4), a thermopile sensitive layer (5), an absorber (6) and a copper pressing ring (7); the aluminum alloy substrate (1) is a circular step structure, the aluminum alloy substrate (1) comprises a first step (8) and a second step (9), the first step (8) and the second step (9) have the same outer diameter, and the second step (9) has an inner diameter greater than the first step (8); the low thermal conductivity film (2) is in the shape of a disc and is straight. The diameter of the second step (9) is slightly smaller than the inner diameter of the second step (9), the low thermal conductivity film (2) is placed on the first step (8) and forms a concentric circle with the aluminum alloy substrate (1), the outer circle of the copper plating layer (3) is in the shape of a circular ring, the center is in the shape of a disc, the diameter of the central disc is slightly larger than the diameter of the absorber (6), the copper plating layer (3) is arranged on the upper part of the low thermal conductivity film (2), the insulating layer (4) is in the shape of a disc and is arranged on the upper part of the copper plating layer (3), the thermopile sensitive layer (5) is arranged on the upper part of the insulating layer (4), and both ends of the thermopile sensitive layer (5) are The absorber (6) is located at the outer circle and inner circle of the copper plating layer (3) and above the insulating layer (4). The absorber (6) is located in the middle of the thermopile sensitive layer (5). The copper pressing ring (7) is located on the upper part of the insulating layer (4). The inner diameter of the copper pressing ring (7) is larger than the outer diameter of the sensitive layer. The copper pressing ring (7) does not contact the sensitive layer. The copper pressing ring (7) and the aluminum alloy substrate (1) are in interference fit. The thermopile sensitive layer (5) includes a thermopile positive electrode layer (10) and a thermopile negative electrode layer (11). The thermopile negative electrode layer (11) and The positive electrode layers (10) of the thermopile are symmetrical and closely connected to each other. A pure silver sheet (12) is provided on the thermopile sensitive layer (5). A terminal (29) penetrating the aluminum alloy substrate (1) is provided at the lower part of one end of the pure silver sheet (12). The terminal (29) comprises an insulating seat (13) and a copper needle (14) penetrating the insulating seat (13). A first through hole (15) cooperating with the insulating seat (13) is provided on the copper plating layer (3) and the low thermal conductivity film (2). The insulating seat (13) is a polytetrafluoroethylene insulating seat (13).

2. A low-power laser thermopile sensor according to claim 1, characterized in that: The low thermal conductivity film (2) is made of nylon.

3. A laser power meter with a built-in thermopile sensor, comprising an aluminum alloy front cover (16), an aluminum alloy body (17), a thermopile sensor (18) and an aluminum alloy rear cover (19), characterized in that: The thermopile sensor (18) is a low-power laser thermopile sensor (18) as claimed in any one of claims 1 to 2; the aluminum alloy body (17) is arranged on the upper part of the aluminum alloy back cover (19); a circular sink (20) is provided on the upper part of the aluminum alloy body (17); the thermopile sensor (18) is arranged inside the circular sink (20); a second through hole (21) penetrating the aluminum alloy body (17) is provided in the middle part of the aluminum alloy body (17); the aluminum alloy front cover (16) is arranged on the upper part of the aluminum alloy body (17) and a light hole (22) penetrating the aluminum alloy front cover (16) is provided in the middle part.

4. The laser power meter with built-in thermopile sensor according to claim 3, characterized in that: The aluminum alloy front cover (16) and the aluminum alloy rear cover (19) are each provided with a plurality of third through holes (23) penetrating therethrough; the aluminum alloy body (17) is provided with threaded holes (24) corresponding to the positions of the third through holes (23); countersunk screws (25) are provided in the threaded holes (24); the countersunk screws (25) fix the aluminum alloy front cover (16), the aluminum alloy body (17), the thermopile sensor (18) and the aluminum alloy rear cover (19) into a whole.

5. The laser power meter with built-in thermopile sensor according to claim 4, characterized in that: The aluminum alloy body (17) is provided with a top screw washer (27), an M4 hexagonal top screw (28) used in conjunction with the top screw washer (27), and a shielding wire (26) arranged on one side of the aluminum alloy body (17).

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