Gas concentration detection device and gas concentration detection apparatus

Abstract

The utility model discloses a kind of gas concentration detection device and gas concentration detection equipment, it is related to gas detection technical field, the device disclosed has test casing, test cavity is formed in casing, first arc reflection surface and second arc reflection surface are provided in test cavity, first arc reflection surface is equipped with incident hole, second arc reflection surface is equipped with exit hole, first arc reflection surface and second arc reflection surface are all non-spherical curved surface reflection surface;Non-spherical curved surface reflection surface is used to adjust the interference phenomenon of laser light wave.Compared with the prior art, the utility model uses two pieces of non-spherical curved surface reflection surface as arc reflection surface, which can reduce the interference phenomenon of laser light wave.

Description

Technical Field

[0001] This utility model relates to the field of gas detection technology, and in particular to a gas concentration detection device and gas concentration detection equipment. Background Technology

[0002] Currently, most existing gas concentration detection devices (such as Herriott chambers) employ two spherical reflective mirrors. While this allows for multiple reflections, it results in significant design aberrations and severe laser light interference, leading to substantial measurement errors when measuring gases such as carbon dioxide. Utility Model Content

[0003] The main purpose of this utility model is to provide a gas concentration detection device and a gas concentration detection equipment, which aims to solve the technical problem that the existing gas concentration detection device has a large measurement error due to the laser light wave interference phenomenon.

[0004] To achieve the above objectives, this utility model proposes a gas concentration detection device. The device has a test housing, and a test cavity is formed inside the housing. A first arc-shaped reflective surface and a second arc-shaped reflective surface are arranged opposite to each other in the test cavity. An entrance hole is provided on the first arc-shaped reflective surface, and an exit hole is provided on the second arc-shaped reflective surface. Both the first arc-shaped reflective surface and the second arc-shaped reflective surface are non-spherical curved surface reflective surfaces. The non-spherical curved reflective surface is used to adjust the interference phenomenon of laser light waves.

[0005] In one embodiment, the entrance aperture is provided with an adjustment device and a laser, and the adjustment device is connected to the inner wall of the entrance aperture; The laser is connected to the adjustment device and is used to emit the laser light wave into the test cavity.

[0006] In one embodiment, the adjusting device includes a mounting cylinder and a plurality of adjusting screws. The mounting cylinder is fixedly connected to the inner wall of the inlet hole, and the plurality of adjusting screws are movably inserted through the mounting cylinder along the circumference of the mounting cylinder. The laser is disposed inside the mounting cylinder and connected to a plurality of adjusting screws, so that the laser can adjust the emission position of the laser light wave through the mounting cylinder and the plurality of adjusting screws.

[0007] In one embodiment, the laser emission port of the laser is provided with an aspherical self-focusing lens. The laser also contains a circuit board, on which thermocouples and thermistors are mounted for collecting the temperature of the laser. A heat sink is provided at the bottom of the laser for dissipating heat from the laser.

[0008] In one embodiment, a curved aspherical lens is provided in the exit aperture to optimize the aberration of the laser light wave, so as to make the laser light wave uniform and stable and reduce the interference of the laser light wave.

[0009] In one embodiment, a photodetector is further provided on the first arc-shaped reflective surface to convert the optical signal corresponding to the laser light wave in the test cavity into an electrical signal.

[0010] In one embodiment, the top of the housing of the photodetector is an aspherical focusing lens, and the surface of the aspherical focusing lens is coated with a dielectric antireflection film, a waterproof film, and an anti-interference film layer. The dielectric antireflection film is used to improve the transmittance of the laser light wave; The waterproof membrane is used to prevent water vapor around the photodetector from condensing into water droplets on the aspherical focusing lens; The anti-interference film layer is used to prevent the laser light wave from forming interference fringe signals on the surface of the aspherical focusing lens, which would affect the normal measurement of the photodetector.

[0011] In one embodiment, the non-spherical curved reflective surface is made of ultraviolet fused silica material and is gold-plated on the surface of the ultraviolet fused silica to prevent the non-spherical curved reflective surface from being damaged by the laser light wave.

[0012] In one embodiment, the housing is made of 314 stainless steel to prevent deformation caused by external temperature changes or external impacts.

[0013] In addition, to achieve the above objectives, this utility model also proposes a gas concentration detection device, which includes the gas concentration detection apparatus as described above.

[0014] This utility model proposes a gas concentration detection device, which has a test housing and a test cavity formed inside the housing. The test cavity is provided with a first arc-shaped reflective surface and a second arc-shaped reflective surface arranged opposite to each other. The first arc-shaped reflective surface is provided with an entrance hole, and the second arc-shaped reflective surface is provided with an exit hole. Both the first arc-shaped reflective surface and the second arc-shaped reflective surface are non-spherical curved surface reflective surfaces. The non-spherical curved surface reflective surface is used to adjust the interference phenomenon of laser light waves.

[0015] Because this invention includes a test housing in the gas concentration detection device, and a first arc-shaped reflective surface and a second arc-shaped reflective surface arranged opposite each other within the test chamber, with an entrance hole on the first arc-shaped reflective surface and an exit hole on the second arc-shaped reflective surface, both the first and second arc-shaped reflective surfaces are non-spherical curved surface reflective surfaces. These non-spherical curved surface reflective surfaces are used to adjust the interference phenomenon of laser light waves. Compared to existing methods, this invention uses two non-spherical curved surface reflective surfaces as arc-shaped reflective surfaces, which can reduce the interference phenomenon of laser light waves. Attached Figure Description

[0016] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the present invention and, together with the description, serve to explain the principles of the present invention.

[0017] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of the first embodiment of the gas concentration detection device proposed in this utility model. Figure 2 This is a schematic diagram of the second embodiment of the gas concentration detection device proposed in this utility model. Figure 3 This is a top view of the adjustment device and laser in the second embodiment of the gas concentration detection device proposed in this utility model. Figure 4 This is a schematic diagram of the laser and heat sink in the second embodiment of the gas concentration detection device proposed in this utility model. Figure 5 This is a schematic diagram of the outlet aperture with a curved aspherical lens in the third embodiment of the gas concentration detection device proposed in this utility model. Figure 6 This is a schematic diagram showing the positions of the laser and photodetector in the third embodiment of the gas concentration detection device proposed in this utility model. Figure 7 This is a schematic diagram of the photodetector in the third embodiment of the gas concentration detection device proposed in this utility model.

[0019] Explanation of icon numbers:

[0020] The purpose, features, and advantages of this utility model will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0021] It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0022] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0023] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in this utility model embodiment are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0024] Furthermore, the use of terms such as "first" and "second" in this utility model is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this utility model.

[0025] It should be noted that currently, most existing gas concentration detection devices (such as Herriott chambers) use two spherical reflective mirrors. While this allows for multiple reflections, it results in significant design aberrations and severe laser light interference, leading to substantial measurement errors when measuring gases (such as carbon dioxide).

[0026] To address the aforementioned technical problems, this embodiment provides a gas concentration detection device. This device includes a test housing, and within the test chamber are two opposing arc-shaped reflective surfaces: a first arc-shaped reflective surface and a second arc-shaped reflective surface. The first arc-shaped reflective surface has an entrance aperture, and the second arc-shaped reflective surface has an exit aperture. Both the first and second arc-shaped reflective surfaces are non-spherical curved surfaces. These non-spherical curved surfaces are used to adjust the interference phenomenon of laser light waves. Compared to existing methods, this embodiment uses two non-spherical curved reflective surfaces as arc-shaped reflective surfaces, which can reduce the interference phenomenon of laser light waves.

[0027] For ease of understanding, the following is combined with Figures 1 to 7 The gas concentration detection device provided in the embodiments of this utility model will be described in detail.

[0028] Reference Figure 1 , Figure 1 This is a schematic diagram of the first embodiment of the gas concentration detection device proposed in this utility model.

[0029] like Figure 1 As shown, in this embodiment, the gas concentration detection device has a test housing, and a test cavity is formed inside the test housing 1. A first arc-shaped reflective surface 12 and a second arc-shaped reflective surface 13 are disposed opposite to each other in the test cavity 11. An entrance hole is provided on the first arc-shaped reflective surface 12, and an exit hole is provided on the second arc-shaped reflective surface 13. Both the first arc-shaped reflective surface 12 and the second arc-shaped reflective surface 13 are non-spherical curved surface reflective surfaces. The non-spherical curved surface reflective surfaces are used to adjust the interference phenomenon of laser light waves.

[0030] It should be noted that the aforementioned test housing 1 can be a mechanical structure providing a sealed or semi-sealed optical environment, typically composed of materials with an absorption coefficient ≤0.1cm² for the target wavelength laser. -1 It is made of metal (such as 6061-T6 aluminum alloy) or engineering plastic (such as PEEK), and the inner wall is treated with black oxide or nickel plating to reduce stray reflection.

[0031] It should also be noted that the aforementioned test cavity 11 can be any spatial cavity for storing gas (e.g., carbon dioxide). Understandably, the aforementioned test cavity 11 can be a cavity region machined inside the aforementioned test housing 1, whose geometric volume V_cavity and the flow rate Q of the gas to be measured satisfy τ_residence=V_cavity / Q≥3s, ensuring sufficient interaction between gas molecules and the laser.

[0032] It should also be noted that the aforementioned first arc-shaped reflecting surface 12 and the aforementioned second arc-shaped reflecting surface 13 can be reflecting surfaces composed of the aforementioned non-spherical curved reflecting surfaces. It is understood that the aforementioned first arc-shaped reflecting surface 12 and the aforementioned second arc-shaped reflecting surface 13 are mirror-symmetrical, but each has a non-spherical curvature and is a high-reflectivity mirror surface. Their surface shape is given by the non-spherical equation: z(r)=r 2 / (R(1+√(1 (1+k)r 2 / R 2 )))+ΣA_ir^(2i); Where R is the vertex radius of curvature, k is the conic constant, and A_i is the higher-order aspherical coefficient.

[0033] It should also be noted that the aforementioned non-spherical curved reflective surface can have a radius of curvature that varies with the aperture height r, i.e., R(r) ≠ constant. Within the meridional plane, the angle θ(r) between the surface normal and the optical axis satisfies dθ / dr ≠ 0, which can simultaneously correct on-axis and off-axis aberrations.

[0034] In the specific implementation, by changing the spherical curved surface reflector to the aforementioned non-spherical curved surface reflector, the "fixed cavity length" corresponding to the spherical curved surface reflector is transformed into the "continuously distributed cavity length" corresponding to the aforementioned non-spherical curved surface reflector. This "broadens" the sharp interference oscillations into monotonic intensity changes. Without increasing the mechanical scanning components, the gas concentration detection sensitivity is improved by ≥8 times. At the same time, the disturbance of interference fringes by temperature drift and mechanical vibration is suppressed, achieving highly stable and highly linear gas concentration detection.

[0035] Furthermore, in order to prevent the aforementioned non-spherical curved reflective surface from being damaged, in this embodiment, the aforementioned non-spherical curved reflective surface is made of ultraviolet fused silica material, and gold is plated on the surface of the aforementioned ultraviolet fused silica to prevent the aforementioned non-spherical curved reflective surface from being damaged by the laser light wave.

[0036] Understandably, the aforementioned ultraviolet fused silica material is an amorphous glass made by electrofusion or gas melting of high-purity SiO2 (>99.995%) at temperatures above 2000°C, with an absorption coefficient α ≤ 0.001 cm⁻¹ in the 190–2500 nm wavelength range. -1 The coefficient of thermal expansion, CTE, is approximately 5.5 × 10⁻⁶. -7 K -1 (20°C), approximately 1 / 30 the temperature of ordinary optical glass, with a thermal shock resistance parameter M≈800Wm. -1 It belongs to the substrate material of "low temperature drift and high laser damage threshold".

[0037] It is also understood that the aforementioned gold plating can be achieved by growing a thin film of metallic gold on the surface of the aforementioned ultraviolet fused silica material substrate through physical vapor deposition (PVD) or chemical vapor deposition (CVD), with a typical thickness of 100–300 nm, a reflectivity of R≥98% in the infrared band (1–5 µm), and chemical inertness (standard electrode potential +1.5 V), which can block the laser-induced erosion of the substrate surface by oxygen and water molecules.

[0038] In the specific implementation, the process of preparing the above-mentioned non-spherical curved reflective surface using the aforementioned UV-fused silica substrate is as follows: A German Heraeus "Suprasil 300" blank with an OH content <1ppm and a bubble level of B / 0 (DIN58927) is used. A φ50mm×15mm cylindrical blank is machined into a "near-spherical" resin wheel with a grinding allowance of 50µm using a CNC milling machine. On a 5-axis airbag polishing machine (Zeeko IRP-200), iterative polishing with a polyurethane polishing pad and CeO2 slurry is performed until the surface shape error converges to PV≤0.15µm and the surface roughness Sa≤0.5nm (measured with a white light interferometer). The above gold plating process is as follows: acetone → IPA → deionized water, 10min each; nitrogen drying; surface contact angle θ>70° is used to determine cleanliness. The process is carried out under a vacuum of 5×10⁻⁶. -3 In the cavity of Pa, 800 eVAr + Bombardment for 2 minutes removes surface organic residues and enhances film-substrate adhesion. A 10nm Cr or NiCr layer is first deposited as a "base layer," followed by a 200nm Au layer; deposition rate is 0.3nms. -1 The substrate temperature was maintained at 150°C, and the film stress was controlled at... 50 MPa (compressive stress) was applied to prevent blistering during thermal cycling. Annealing in air at 150°C for 2 hours resulted in gold film grain size growth to 50–80 nm. Measured reflectivity at λ=1.57 µm showed R=98.7%, and the laser damage threshold (1-on-1, 10 ns, 1.57 µm) was ≥15 J / cm². -2 It is approximately 3 times better than conventional silver film.

[0039] Furthermore, in order to prevent the test housing 1 from being damaged, in this embodiment, the test housing 1 is made of 314 stainless steel to prevent deformation caused by external temperature changes or external impacts.

[0040] It is understood that the aforementioned 314 stainless steel can be austenitic Cr-Ni-Mo stainless steel with a nominal composition of C≤0.08%, Cr23–26%, Ni19–22%, Mo2.0–3.0%, room temperature yield strength σ0.2≥205MPa, and CTE≈14×10 -6 K -1 It is approximately 2 / 3 the strength of ordinary carbon steel; within the temperature range of 0–100°C, its elastic modulus E≈200GPa and thermal conductivity λ≈15Wm. -1 K -1 It combines the characteristics of "high rigidity, low thermal expansion, and corrosion resistance" and is commonly known as "high-stability austenitic steel".

[0041] In this embodiment, a test housing is provided in the gas concentration detection device. A first arc-shaped reflective surface and a second arc-shaped reflective surface are arranged opposite each other within the test chamber. An entrance hole is provided on the first arc-shaped reflective surface, and an exit hole is provided on the second arc-shaped reflective surface. Both the first and second arc-shaped reflective surfaces are non-spherical curved surface reflective surfaces. These non-spherical curved surface reflective surfaces are used to adjust the interference phenomenon of laser light waves. Compared to existing methods, this invention uses two non-spherical curved surface reflective surfaces as arc-shaped reflective surfaces, which can reduce the interference phenomenon of laser light waves.

[0042] Reference Figure 2 , Figure 2 This is a schematic diagram of the second embodiment of the gas concentration detection device proposed in this utility model.

[0043] Based on the above embodiments, a second embodiment of the present invention is proposed. In order to emit laser light waves, such as... Figure 2 As shown, in this embodiment, the entrance hole 121 is provided with an adjustment device 122 and a laser 123. The adjustment device 122 is connected to the inner wall of the entrance hole 121; the laser 123 is connected to the adjustment device 122 and is used to emit the laser light wave into the test cavity 11.

[0044] Understandably, the aforementioned entrance aperture 121 can be a light-transmitting aperture located at the apex region of the first arc-shaped reflecting surface, with a diameter D. a Typically, the beam waist ω0 is 10%–20% larger than the laser beam waist to ensure >99% energy transmission while maximizing the blocking of stray light. The inner wall of the hole is equipped with an "integrated positioning-adjustment countersink," whose geometric tolerances are machined according to ISO2768-mk, for use in the socket adjustment device.

[0045] It is also understandable that the aforementioned adjustment device 122 can be a "miniature multi-axis displacement-angle platform" integrated into the inner wall of the aforementioned entrance aperture 121, providing the following within a space of ≤5mm: XY two-dimensional translation: stroke ±0.3mm, resolution ≤0.5µm; θx-θy two-dimensional tilt: stroke ±2°, resolution ≤5µrad; Z-axis focal length fine adjustment: stroke ±0.2mm, used to correct the laser beam waist position and cavity mode matching. The driving method can be selected as "differential head + disc spring" or "piezoelectric ceramic + flexible hinge", and all materials are made of 316L stainless steel or titanium alloy to prevent dissimilar metal corrosion with the aforementioned test housing 1, which is made of 314 stainless steel.

[0046] It is also understandable that the aforementioned laser 123 could be a single-longitudinal-mode DFB laser with a center wavelength of 1573nm, a linewidth Δν ≤ 2MHz, and a continuous output power P = 10mW. The device uses a TO-60 standard metal package (φ5.6mm cap, total height 8.2mm, 3-pin TO-can structure), and integrates an aspherical microlens internally. The divergence angle θ is factory collimated. e ≈0.2mrad, output beam is TEM 00 The linear polarization extinction ratio is >100:1. The TO-60 package base directly mates with the inner ring of the adjustment device (φ5.6mmH7 / g6 transition fit), requiring no additional adapter flange. Maintains sealing and directional stability in environments ranging from 40°C to +85°C.

[0047] In practical implementation, through an integrated design of "entry aperture-adjustment device-laser," the following can be achieved within a tiny space of φ8mm×10mm: translational resolution ≤0.5µm, angular resolution ≤5µrad; spot offset after closed-loop control <±2µm, signal coupling efficiency ≥99%; laser replacement and realignment completed in <30s, reducing maintenance time by 90%; all-metal structure, allowing for... It can operate continuously at temperatures ranging from 40°C to +85°C, meeting the requirements of harsh environments such as vehicle and shipboard applications.

[0048] Furthermore, in order to integrate the laser 123 with the adjustment device 122, such as... Figure 3 As shown, Figure 3 This is a top view of the adjustment device and laser in the second embodiment of the gas concentration detection device proposed in this utility model. In this embodiment, the adjustment device 122 includes a mounting cylinder 1221 and a plurality of adjustment screws 1222. The mounting cylinder 1221 is fixedly connected to the inner wall of the entrance hole 121. The plurality of adjustment screws 1222 move circumferentially through the mounting cylinder 1221. The laser 123 is disposed inside the mounting cylinder 1221 and connected to the plurality of adjustment screws 1222, so that the laser 123 can adjust the emission position of the laser light wave through the mounting cylinder 1221 and the plurality of adjustment screws 1222.

[0049] Understandably, the aforementioned mounting sleeve 1221 can be a cylindrical sleeve made of 316L stainless steel, with an outer diameter D1 and an inner diameter of the injection hole using a slight interference fit of H7 / k6, a length L1=10mm, a wall thickness of 1mm, and an inner diameter D2=TO-60 package outer diameter + 0.05mm (i.e. 5.65mm), ensuring that the radial gap after the aforementioned laser 123 is inserted is <25µm, leaving a margin without causing obvious eccentricity.

[0050] It should be noted that the aforementioned adjusting screw 1222 can be a standard M1.6×0.35mm fine-pitch headless nut screw, with a ruby ​​ball glued to the front end (φ1mm, surface roughness Ra≤0.05µm), and a knurled rear end with a 0.9mm wide slotted groove, allowing it to be rotated with a precision screwdriver. The screw has a total length of 8mm, an effective stroke of 2.5mm, and a pitch of 0.35mm, corresponding to a forward movement of 97.5µm per revolution. Combined with a 0.25mm indexing plate, a displacement resolution of ≤2.5µm can be achieved.

[0051] It is also understandable that the three threaded holes are spaced 120°±0.1° apart along the circumference on the same cross section of the cylinder, forming a "three-point centering" kinematic constraint. Their geometric center coincides with the axis of the mounting cylinder, which can ensure that the center position of the laser 123 is not excessively constrained and avoid thermal stress deformation.

[0052] In the specific implementation, under the clamping of the aforementioned mounting cylinder 1221, three M1.6 threaded bottom holes are CNC milled with a positional accuracy ≤8µm. The threaded hole entrances are chamfered at 0.3×45° to prevent the ruby ​​ball at the screw tip from scratching the laser coating. The outer wall of the aforementioned laser 123 (TO-60) is fitted with a 0.1mm thick polyimide film "anti-scratch sleeve." Then, the mounting cylinder is inserted, and the three screws are pre-tightened until they just touch. They are then tightened with a 0.05N·m torque screwdriver to complete the "zero point" setting. For the fine-tuning mechanism (taking "upward offset +50µm" as an example), the front ends of the aforementioned adjusting screws 1222 all extend 1.00mm, aligning the laser center O0 with the cylinder axis. This allows the beam to be shifted upward by ΔY=+50µm. The top screw (S1) is turned counterclockwise by half a turn → the front end extends by 1.00 + 0.05 = 1.05 mm. The lower left screw (S2) and the lower right screw (S3) are each turned clockwise by 1 / 4 turn → the front end extends by 0.975 mm. The three points form a new plane, the laser is lifted by S1, the center moves upward by ΔY = 50µm, the lateral ΔX ≈ 0, and the tilt Δθ ≈ 0.02mrad (negligible). The entire process is completed within 30 seconds, and real-time readings are taken using a four-quadrant detector. The process stops when the Y offset is < ±2µm.

[0053] Furthermore, in order to install the aforementioned laser 123, such as Figure 4 As shown, Figure 4 This is a schematic diagram of the laser and heat sink in the second embodiment of the gas concentration detection device proposed in this utility model. In this embodiment, the laser emission port of the laser 123 is provided with an aspherical self-focusing lens 1231, and a circuit board 1232 is also provided inside the laser 123. The circuit board 1232 is provided with a thermocouple TC and a thermistor R for collecting the temperature of the laser 123. A heat sink is provided at the bottom of the laser 123 for dissipating heat from the laser 123.

[0054] It is understood that the aforementioned emission port can be a sapphire window area with a central diameter of 1.8mm in the TO-60 package cap. The aforementioned aspherical self-focusing lens 1231 is coaxially mounted on the inner side of the window (i.e., inside the package) using UV adhesive. The optical axis of the lens is ≤5µm off-center from the chip's light-emitting point. The adhesive layer thickness is 5µm, and the shear strength after curing is >20MPa, which can withstand 5g of random vibration.

[0055] It is also understandable that the aforementioned aspherical self-focusing lens 1231 can be a second-order aspherical surface (conicconstantk≈ 0.6), the rear end face is flat, the overall diameter is 2.0 mm and the length is 2.5 mm, the material is thallium-doped gradient refractive index glass (GRIN, radial refractive index distribution n(r) = n0(1 Ar 2 / 2)). Aspherical curvature is used to eliminate spherical aberration of traditional GRIN lenses, enabling the 1573nm laser to be collimated within a length of 2.5mm, with an output beam waist ω0=0.5mm and a divergence angle θ. e ≤0.2mrad, coupling efficiency ≥95%.

[0056] It should be noted that the aforementioned circuit board 1232 can be a 0.5mm thick Al2O3 ceramic copper-clad laminate (DBC, 0.1mm Cu layer). The aforementioned thermocouple TC can be a type K (NiCr-NiSi) with a wire diameter of 25µm and a time constant τ < 10ms, used for real-time monitoring of the chip junction temperature Tj; its hot end is laser-spot-welded to the center of the chip's back electrode, and its cold end is soldered to the copper foil of the circuit board, forming a differential temperature measurement circuit with a temperature measurement accuracy of ±0.5°C. The aforementioned thermistor R can be a 0402 package, R... 25 =10kΩ, B=3950K, surface-mount glass encapsulation, response time 0.8s, mounted on the back of the circuit board near the heatsink, used to monitor the case temperature Tc; forming a "two-point temperature difference" criterion with the thermocouple, it can provide a 5s advance warning of thermal runaway. The aforementioned heatsink 124 can be made of C1100 oxygen-free copper, with an outer diameter of φ10mm×6mm, and 12 0.3mm fins milled on the top, with a total surface area of ​​4.5×10 -3 m 2 The bottom is polished to Ra≤0.1µm, coated with 10µm indium foil, and then laser-welded to the base of the laser 123. The interface thermal resistance Rint<0.05K / W.

[0057] In its implementation, the laser 123 achieves an output beam collimation quality M² < 1.05 through on-chip integration of an aspherical self-focusing lens, dual temperature sensors, and a copper fin heat sink, eliminating the need for an external lens. The laser 123's temperature is monitored in real-time with an accuracy of ±0.5°C, and shuts down within 5ms of overheating. Continuous operation at 10mW results in a temperature rise of < 3°C and a lifespan of > 100,000 hours.

[0058] refer to Figure 5 , Figure 5 This is a schematic diagram of the structure of the outlet aperture with a curved aspherical lens in the third embodiment of the gas concentration detection device proposed in this utility model.

[0059] Based on the above embodiments, a third embodiment of the present invention is proposed. To optimize the aberrations of the laser light wave, such as... Figure 5 As shown, in this embodiment, a curved aspherical lens 1251 is provided in the emission aperture 131 to optimize the aberration of the laser light wave, so as to make the laser light wave uniform and stable and reduce the interference of the laser light wave.

[0060] It should be noted that the aforementioned curved aspherical lens 1311 can be a monolithic fused silica lens with a diameter of 4.0 mm, a center thickness of 1.2 mm, and a concave aspherical rear surface (conicconstantk≈ 0.8, with a quadratic curve supplemented with 4th and 6th order terms), the front surface is a slightly convex spherical surface (radius of curvature R = +15mm), and both surfaces are coated with a 1573nm antireflection coating (R ≤ 0.15%). This surface shape can correct the wavefront aberrations (mainly spherical aberration and coma) of a laser beam that has undergone 20 round trips with a cumulative optical path difference ΔL ≈ 1m from λ / 3 to within λ / 10, thus improving the beam quality factor M. 2 It decreased from 1.25 to ≤1.05.

[0061] In a specific implementation, by integrating the aforementioned curved aspherical lens 1311 into the exit aperture, this embodiment can achieve a micro-aperture of 4mm, reducing the error of the aforementioned laser light wave from λ / 3 to λ / 10, M²≤1.05, controlling the spot non-uniformity to ≤3%, and reducing the stripe contrast by 6 times.

[0062] Furthermore, in order to convert the optical signal corresponding to the aforementioned laser light wave into an electrical signal, a reference is made. Figure 6 , Figure 6 This is a schematic diagram showing the positions of the laser and photodetector in the third embodiment of the gas concentration detection device proposed in this utility model. In this embodiment, a photodetector 125 is also provided on the first arc-shaped reflective surface 12 to convert the optical signal corresponding to the laser light wave in the test cavity 11 into an electrical signal.

[0063] It should be noted that the aforementioned photodetector 125 can be a photodetector using an InGaAs PIN chip (model: Hamamatsu G12180-003), with a photosensitive surface φ0.8mm, a response wavelength of 1.0–1.65µm, a peak responsivity of 0.95A / W, and a dark current ≤0.1nA (25°C, VR=5V). The back of the chip is gold-plated and flush-soldered with the reflective surface to ensure that the original curved surface shape is not damaged (surface shape error increment PV<0.02λ).

[0064] In a specific implementation, the photodetector 125 is embedded in the first arc-shaped reflective surface 12 (e.g., Figure 6 As shown, it is spatially parallel to the laser 123 described above, does not occupy additional cavity space, and has an unobstructed optical path. The optical signal corresponding to the laser wave is monitored in real time, and the optical signal is converted into the electrical signal.

[0065] Furthermore, in order to protect the aforementioned photodetector 125, such as Figure 7 As shown, Figure 7 This is a schematic diagram of the photodetector structure in the third embodiment of the gas concentration detection device proposed in this utility model. In this embodiment, the top of the tube shell of the photodetector 125 is an aspherical focusing lens 1251. The surface of the aspherical focusing lens 1251 is coated with a dielectric antireflection film 1252, a waterproof film 1253, and an anti-interference film layer 1254. The dielectric antireflection film 1252 is used to improve the transmittance of the laser light wave. The waterproof film 1253 is used to prevent water vapor around the photodetector 125 from condensing into water droplets on the aspherical focusing lens 1251. The anti-interference film layer 1254 is used to prevent the laser light wave from forming interference fringe signals on the surface of the aspherical focusing lens 1251, which would affect the normal measurement of the photodetector 125.

[0066] It should be noted that the material of the aforementioned aspherical focusing lens 1251 can be ultraviolet fused silica, with a secondary aspherical front surface and a concave spherical rear surface. The aforementioned antireflective coating 1252 can be a four-layer Ta₂O₅ / SiO₂ quarter-wavelength stack, with a center wavelength λ₀ = 1573 nm, a spectral bandwidth of 80 nm, and a single-sided reflectance R ≤ 0.15% after double-sided coating, and an average transmittance T ≥ 99.4% (1570–1580 nm), improving signal amplitude by approximately 4% compared to the uncoated layer. The aforementioned waterproof membrane 1253 is located above the antireflective coating. The waterproof membrane 1253 can be a 20 nm thick RF sputtered polytetrafluoroethylene layer, with a water contact angle θ > 110° and a roll-off angle < 5°. When the ambient temperature drops sharply by ΔT = 10°C, the saturated water vapor pressure difference can be reduced from 12 mbar to 2 mbar, preventing the formation of >50 µm water droplets on the lens surface and avoiding light scattering loss > 5%. A 60nm amorphous magnesium fluoride (MgF2, n=1.38) micro-roughened layer (i.e. the above-mentioned anti-interference film layer 1254) is then deposited on the waterproof membrane. The surface RMS roughness is 15–20nm, forming an exponential refractive index gradient, which destroys the laser coherence and reduces the coherence length between the specular reflected light and the incident light from >10m to <0.3mm. This reduces the interference fringe contrast from 12% to ≤1%, effectively improving the detector output linearity by 6 times.

[0067] In its implementation, the photodetector 125 is integrated with an aspherical focusing lens and a three-layer functional film to increase its transmittance by 4%, increase its signal amplitude by 4%, prevent water droplet condensation at 80% RH, reduce long-term drift to <0.3%, increase interference fringe contrast to ≤1%, and reduce the concentration detection limit from 3 ppm to 0.5 ppm.

[0068] To achieve the above objectives, this utility model also proposes a gas concentration detection device, which includes the gas concentration detection apparatus as described above.

[0069] It should be noted that the specific implementation of the gas concentration detection device provided in this embodiment can refer to the above embodiments, and this embodiment will not elaborate on it further. Therefore, the effects achieved by the gas concentration detection device in this embodiment can also refer to the above embodiments, and this embodiment will not elaborate on them further.

[0070] The above are merely preferred embodiments of this utility model and do not limit the patent scope of this utility model. Any equivalent structural or procedural transformations made based on the description and drawings of this utility model, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this utility model.

Claims

1. A gas concentration detection device, characterized in that, The device has a test housing, and a test cavity is formed inside the housing. A first arc-shaped reflective surface and a second arc-shaped reflective surface are arranged opposite to each other in the test cavity. An entrance hole is provided on the first arc-shaped reflective surface, and an exit hole is provided on the second arc-shaped reflective surface. Both the first arc-shaped reflective surface and the second arc-shaped reflective surface are non-spherical curved surface reflective surfaces. The non-spherical curved reflective surface is used to adjust the interference phenomenon of laser light waves.

2. The gas concentration detection device as described in claim 1, characterized in that, The entrance aperture is equipped with an adjustment device and a laser, and the adjustment device is connected to the inner wall of the entrance aperture; The laser is connected to the adjustment device and is used to emit the laser light wave into the test cavity.

3. The gas concentration detection device as described in claim 2, characterized in that, The adjustment device includes a mounting cylinder and a plurality of adjusting screws. The mounting cylinder is fixedly connected to the inner wall of the inlet hole, and the plurality of adjusting screws are movably inserted through the mounting cylinder along the circumference of the mounting cylinder. The laser is disposed inside the mounting cylinder and connected to a plurality of adjusting screws, so that the laser can adjust the emission position of the laser light wave through the mounting cylinder and the plurality of adjusting screws.

4. The gas concentration detection device as described in claim 2, characterized in that, The laser's laser emission port is equipped with an aspherical self-focusing lens. The laser also contains a circuit board, on which thermocouples and thermistors are mounted for collecting the temperature of the laser. A heat sink is provided at the bottom of the laser for dissipating heat from the laser.

5. The gas concentration detection device as described in claim 1, characterized in that, A curved aspherical lens is provided inside the emission aperture to optimize the aberrations of the laser light wave, so as to make the laser light wave uniform and stable and reduce the interference of the laser light wave.

6. The gas concentration detection device as described in claim 2, characterized in that, A photodetector is also provided on the first arc-shaped reflective surface to convert the optical signal corresponding to the laser light wave in the test cavity into an electrical signal.

7. The gas concentration detection device as described in claim 6, characterized in that, The top of the photodetector's housing is an aspherical focusing lens, and the surface of the aspherical focusing lens is coated with a dielectric antireflection film, a waterproof film, and an anti-interference film layer. The dielectric antireflection film is used to improve the transmittance of the laser light wave; The waterproof membrane is used to prevent water vapor around the photodetector from condensing into water droplets on the aspherical focusing lens; The anti-interference film layer is used to prevent the laser light wave from forming interference fringe signals on the surface of the aspherical focusing lens, which would affect the normal measurement of the photodetector.

8. The gas concentration detection device as described in claim 1, characterized in that, The non-spherical curved reflective surface is made of ultraviolet fused silica material and is plated with gold to prevent the non-spherical curved reflective surface from being damaged by the laser light wave.

9. The gas concentration detection device as described in claim 1, characterized in that, The housing is made of 314 stainless steel to prevent deformation caused by external temperature changes or external impacts.

10. A gas concentration detection device, characterized in that, The gas concentration detection device includes the gas concentration detection apparatus according to any one of claims 1 to 9.

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