A kind of methane laser aspherical lens of preventing water vapor and its preparation method and application

Abstract

The application discloses a kind of methane laser aspherical lens of preventing water vapor and its preparation method and application, the methane laser aspherical lens includes aspherical lens and is set by the composite film of being made of aluminum oxide, magnesium fluoride and silicon dioxide in its surface.The preparation method includes providing aspherical lens, with the composite material of aluminum oxide, magnesium fluoride and silicon dioxide as target material, using magnetron sputtering process to deposit water vapor prevention film layer on the surface of aspherical lens.The methane laser aspherical lens of the application sets a layer of composite film made of aluminum oxide, magnesium fluoride and silicon dioxide on the surface of aspherical lens, with the advantages of good thermal stability, good light transmission, good hydrophilicity, long service life and the like, can effectively prevent the water mist of methane laser aspherical lens, and the duration of anti-fog is long, can be used to build laser methane sensor, can realize the stable, accurate detection of laser methane sensor, with high use value and good application prospect.

Description

Technical Field

[0001] This invention relates to an aspherical lens for methane lasers that prevents water vapor from entering, its preparation method, and its application. Background Technology

[0002] Laser methane sensors employ Tunable Laser Gas Absorption Spectroscopy (TDLAS) technology, incorporating an optical path structure, circuit design, and algorithm compensation. They offer high detection accuracy and are gradually replacing traditional detection methods like electrochemical catalytic combustion due to their excellent gas selectivity, lack of oxygen dependence, and long lifespan. However, in practical applications, downhole environments can cause fogging on the laser surface. Water vapor adhesion leads to diffuse reflection of light hitting tiny water droplets, reducing the laser's transmittance and decreasing the intensity received by the optical detector. Experiments have shown a decrease in light intensity exceeding half, resulting in reduced detection accuracy, false alarms, and monitoring failure. Over time, this can lead to significant safety hazards. In particular, the laser's packaging uses traditional TO56 or TO60 formats. This type of packaging requires an aspherical lens to converge the diverging beam into a beam. In rainy conditions during the rainy season, fogging on the lens surface causes the sensor's light intensity to attenuate to the detection limit, preventing normal detection function throughout the rainy season. Therefore, developing aspherical lenses with anti-condensation capabilities is crucial.

[0003] Currently, preparing a waterproof fog film on the surface of an aspherical lens is a feasible solution for preventing water vapor condensation. However, the waterproof fog film used in the prior art is mainly a TiO2 thin film coating. This film has good photocatalytic properties and exhibits high photocatalytic activity under ultraviolet light irradiation. It is also superhydrophilic and oleophilic. However, the laser of this product is placed in the well of a gas pipeline, and the service environment is not exposed to sunlight and ultraviolet radiation, so this method is not suitable. In addition, researchers have proposed a novel optical coating material with anti-fog properties, comprising the following components: 0-50% nano-silica, 0-10% zirconium dioxide, 0-5% zinc sulfide, 0-40% niobium pentoxide, and 0-20% yttrium oxide. However, the zirconium oxide used in this optical coating material increases the hardness of the film, making it difficult to stably load onto the surface of an aspherical lens. At the same time, the extensive use of rare elements such as zirconium dioxide, niobium pentoxide, and yttrium oxide makes its cost very high, hindering its widespread application. In particular, this optical coating material is difficult to enhance the thermal stability of the film, making it prone to detaching from the mirror surface under high and low temperature environments, especially from aspherical lenses, thus making it difficult to widely apply to achieve the anti-vapor condensation function of aspherical lenses for methane lasers. In addition, some researchers have proposed a long-lasting anti-fog and easy-to-clean lens for myopia. This involves sequentially applying a siliconized hardening film, a nano-alumina film, an anti-reflective coating, a nano-silica film, a nano-anti-fog modified film, and a protective film to the surface of the resin lens. While these layers improve scratch resistance during immersion, they also result in an excessively thick overall lens, making it unsuitable for aspherical lenses. Furthermore, the hydrophilic groups of the nano-modified film form a superhydrophilic water film between the resin lens and dirt. Although this prevents dirt from contacting the lens, it cannot effectively and promptly remove moisture from the lens surface. This leads to condensation of numerous small water droplets, exacerbating diffuse reflection and significantly reducing the transmittance of the laser emission. Consequently, the detection performance of the laser methane sensor deteriorates, and the presence of dirt may even block laser emission, causing the laser methane sensor to malfunction.

[0004] Therefore, obtaining an aspherical lens for a methane laser with good thermal stability, good light transmittance, good hydrophilicity, and long service life is of great significance for achieving stable and accurate detection by laser methane sensors and promoting their widespread use. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a methane laser aspherical lens with good thermal stability, good light transmittance, good hydrophilicity, and long service life that prevents water vapor, as well as its preparation method and application.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A methane laser aspherical lens for preventing water vapor includes an aspherical lens with a water-vapor-proof film layer on its surface; the water-vapor-proof film layer is a composite film composed of aluminum oxide, magnesium fluoride and silicon dioxide.

[0008] In a further improvement of the aforementioned aspherical lens for a methane laser, the water-resistant vapor membrane layer contains 5%–10% aluminum oxide, 10%–20% magnesium fluoride, and 70%–80% silicon dioxide by mass.

[0009] In a further improvement to the aforementioned aspherical lens for a methane laser, the thickness of the waterproof vapor membrane layer is 200 nm to 230 nm.

[0010] The aforementioned aspherical lens for a methane laser is further improved by having a diameter of 3mm to 5mm.

[0011] As a general technical concept, the present invention also provides a method for fabricating an aspherical lens for a methane laser that prevents water vapor, comprising the following steps:

[0012] S1. Provides aspherical lenses;

[0013] S2. Using a composite material of alumina, magnesium fluoride and silicon dioxide as the target material, a waterproof vapor film layer is deposited on the surface of an aspherical lens by magnetron sputtering.

[0014] A further improvement to the above preparation method is that, in step S2, the preparation method of the composite material of alumina, magnesium fluoride, and silicon dioxide includes the following steps:

[0015] (1) Mix silicon dioxide powder, aluminum oxide powder and magnesium fluoride powder and pre-sinter;

[0016] (2) The material obtained after pre-sintering in step (1) is placed into a mold for secondary sintering to obtain a semi-finished product;

[0017] (3) The semi-finished product obtained in step (2) is surface processed to make all surfaces of the semi-finished product flat, so as to obtain a composite material of alumina, magnesium fluoride and silicon dioxide.

[0018] In a further improvement to the above preparation method, in step (1), the mass ratio of silica powder, alumina powder, and magnesium fluoride powder is 1-2:2-4:14-16; the silica powder is prepared by the following method: mixing silicate ester with anhydrous ethanol, stirring, adding deionized water, adjusting the pH of the solution, adding surfactant, aging, and obtaining a gel; calcining the gel to obtain silica powder; the particle size of the silica powder is nanoscale; the particle size of the alumina powder is 1μm-5μm; the particle size of the magnesium fluoride powder is 1μm-5μm; the pre-sintering is carried out at a temperature of 1000℃-1300℃; the pre-sintering time is 8 hours-12 hours.

[0019] In a further improvement to the above preparation method, in step (2), the secondary sintering is carried out under vacuum or inert atmosphere; the secondary sintering is carried out at a temperature of 1500℃; the pressure of the system is controlled to be maintained at 50MPa during the secondary sintering process; the composite material of alumina, magnesium fluoride and silicon dioxide is columnar with a diameter of 76.2mm and a height of 9mm.

[0020] In a further improvement to the above preparation method, in step S1, the diameter of the aspherical lens is 3mm to 5mm.

[0021] In a further improvement to the above preparation method, in step S2, the deposition process parameters of the waterproof vapor film layer are as follows: the magnetron sputtering power is controlled at 150W, the Ar inlet gas flow rate is 20 sccm, the outlet gas flow rate is 20 sccm, the sputtering vacuum degree is maintained at 0.4Pa, and the coating time is 2 h to 2.5 h.

[0022] In a further improvement to the above preparation method, in step S2, the waterproof vapor membrane layer is a composite membrane composed of alumina, magnesium fluoride, and silicon dioxide; the mass percentage of alumina in the waterproof vapor membrane layer is 5%–10%, the mass percentage of magnesium fluoride is 10%–20%, and the mass percentage of silicon dioxide is 70%–80%; the thickness of the waterproof vapor membrane layer is 200 nm–230 nm.

[0023] As a general technical concept, the present invention also provides a laser methane sensor, which includes the above-described methane laser aspherical lens or the methane laser aspherical lens prepared by the above-described preparation method.

[0024] Compared with the prior art, the advantages of the present invention are as follows:

[0025] (1) This invention creatively provides an aspherical lens for methane lasers that prevents water vapor. By setting a composite film composed of aluminum oxide, magnesium fluoride and silicon dioxide on the surface of the aspherical lens, a waterproof vapor-proof film layer with good thermal stability, good light transmittance and good hydrophilicity can be formed on the surface of the aspherical lens. Specifically: under the action of aluminum oxide, the thermal stability adaptability between the waterproof vapor-proof film layer and the aspherical lens can be enhanced, and the film layer can be effectively prevented from peeling and cracking in high and low temperature environments; under the action of magnesium fluoride, the refractive index of the film layer can be reduced, and the light transmittance effect can be enhanced; under the action of silicon dioxide, the surface tension of the film layer can be enhanced, the diffuse reflection of the laser can be reduced, and the water contact angle can reach 13°. Moreover, experiments show that when the water contact angle is ≤25°, the film layer has anti-fogging performance. This invention relates to an aspherical lens for methane lasers, which has a composite film made of aluminum oxide, magnesium fluoride, and silicon dioxide on its surface. This film has advantages such as good thermal stability, good light transmittance, good hydrophilicity, and long service life. It can effectively prevent water fogging in the aspherical lens of the methane laser, and the anti-fogging effect lasts for a long time. It can be used to construct a laser methane sensor, enabling stable and accurate detection of laser methane. It has high practical value and good application prospects.

[0026] (2) In the aspherical lens of the methane laser of the present invention, by optimizing the mass percentage of aluminum oxide in the waterproof vapor membrane layer to 5% to 10%, the mass percentage of magnesium fluoride to 10% to 20%, and the mass percentage of silicon dioxide to 70% to 80%, the wear resistance and light transmittance of the membrane layer can be significantly improved, and the hydrophilicity of the membrane layer can be greatly improved, so that the laser can pass through the aspherical lens smoothly without refraction.

[0027] (3) In the aspherical lens of the methane laser of the present invention, by optimizing the thickness of the waterproof vapor membrane layer to 200 nm to 230 nm, the laser refraction can be significantly reduced. Attached Figure Description

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0029] Figure 1 This is a schematic diagram of the aspherical lens structure of the methane laser that prevents water vapor in Embodiment 1 of the present invention.

[0030] Figure 2 This is a schematic diagram of the water contact angle on the surface of the aspherical lens of the methane laser used in Embodiment 1 of the present invention to prevent water vapor.

[0031] Legend:

[0032] 1. Waterproof vapor membrane layer; 2. Aspherical lens. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0034] Example 1:

[0035] like Figure 1 As shown, a methane laser aspherical lens for preventing water vapor includes an aspherical lens 2, on the surface of which a water vapor-proof membrane layer 1 is provided, wherein the water vapor-proof membrane layer 1 is a composite film composed of aluminum oxide, magnesium fluoride and silicon dioxide.

[0036] In this embodiment, the water vapor membrane layer contains 7% aluminum oxide, 18% magnesium fluoride, and 75% silicon dioxide by mass.

[0037] In this embodiment, the thickness of the waterproof vapor membrane layer is 220 nm.

[0038] In this embodiment, the diameter of the aspherical lens is 3mm.

[0039] A method for fabricating the above-mentioned aspherical lens for preventing water vapor in a methane laser includes the following steps:

[0040] S1. Provide an aspherical lens, wherein the diameter of the aspherical lens is 3mm.

[0041] S2. Using a composite material of alumina, magnesium fluoride and silicon dioxide as the target material, a waterproof vapor film layer is deposited on the surface of an aspherical lens by magnetron sputtering. The deposition process parameters for the waterproof vapor film layer are as follows: the magnetron sputtering power is controlled at 150W, the Ar inlet gas flow rate is 20 sccm, the outlet gas flow rate is 20 sccm, the sputtering vacuum degree is maintained at 0.4Pa, and the coating time is 2 h.

[0042] In this embodiment, the preparation method of the composite material of alumina, magnesium fluoride, and silicon dioxide includes the following steps:

[0043] (1) The silicon dioxide powder, aluminum oxide powder and magnesium fluoride powder are mixed in a mass ratio of 7:18:85 and pre-sintered at 1200℃ for 10 hours.

[0044] (2) The material obtained after pre-sintering in step (1) is placed in a graphite mold, heated to 1500℃ and kept at 50MPa under an inert atmosphere, and then sintered for a second time to obtain a high-density sputtering target semi-finished product.

[0045] (3) The high-density sputtering target semi-finished product obtained in step (2) is surface processed to keep all surfaces of the semi-finished product flat, and a composite material of alumina, magnesium fluoride and silicon dioxide is obtained. The composite material of alumina, magnesium fluoride and silicon dioxide is columnar with a diameter of 76.2 mm and a height of 9 mm (including a 3 mm copper back plate).

[0046] In this embodiment, the silica powder is prepared by the following method: silicate ester is mixed with anhydrous ethanol, stirred, deionized water is added, the pH value of the solution is adjusted, a surfactant is added, and the mixture is aged to obtain a gel; the gel is then calcined to obtain silica powder.

[0047] In this embodiment, the particle size of the silica powder is in the nanometer range.

[0048] In this embodiment, the particle size of the alumina powder is 1μm to 5μm.

[0049] In this embodiment, the particle size of the magnesium fluoride powder is 1μm to 5μm.

[0050] Testing showed that the water contact angle of the aspherical lens for the methane laser prepared in this embodiment can reach 13°. Figure 2 As shown.

[0051] A laser methane sensor includes the aspherical lens of the methane laser prepared above.

[0052] In this embodiment, waterproof vapor membranes with different ratios of alumina, magnesium fluoride, and silica were also prepared. Under the same conditions, their water contact angles are shown in Table 1.

[0053] Table 1. Water contact angle of waterproof vapor membranes with different ratios of alumina, magnesium fluoride, and silica.

[0054]

[0055] As shown in Table 1, under different proportions of the three components in the composite membrane, the water contact angle of the composite membrane is the smallest at 13° when the mass fraction of alumina is 7%, magnesium fluoride is 18%, and silicon dioxide is 75%, which is the optimal proportion.

[0056] In this embodiment, waterproof vapor membrane layers of different thicknesses were also prepared, with other conditions being the same as in Example 1. Their water contact angles are shown in Table 2.

[0057] Table 2. Water contact angle of waterproof vapor membrane layers of different thicknesses

[0058]

[0059] As shown in Table 2, the waterproof vapor barrier exhibits good hydrophilicity when the thickness is between 200 nm and 230 nm. In particular, the water contact angle is smallest when the thickness is 220 nm, which is the optimal thickness for the membrane. Furthermore, a waterproof vapor barrier thickness of 200 nm to 230 nm can significantly reduce laser refraction.

[0060] As can be seen from the above results, compared with conventional aspherical lenses, the aspherical lens for methane lasers of the present invention, which has a composite film composed of aluminum oxide, magnesium fluoride and silicon dioxide on the surface of the aspherical lens, has the advantages of good thermal stability, good light transmittance, good hydrophilicity and long service life. It can effectively prevent water fog from forming on the aspherical lens of the methane laser, and the anti-fogging effect lasts for a long time. It can be used to construct laser methane sensors, enabling stable and accurate detection of laser methane. It has high practical value and good application prospects.

[0061] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. An aspherical lens for a methane laser that prevents water vapor buildup, characterized in that, The invention includes an aspherical lens, the surface of which is provided with a waterproof vapor film layer; the waterproof vapor film layer is a composite film composed of alumina, magnesium fluoride and silicon dioxide; the mass percentage of alumina in the waterproof vapor film layer is 5% to 10%, the mass percentage of magnesium fluoride is 10% to 20%, and the mass percentage of silicon dioxide is 70% to 80%; the thickness of the waterproof vapor film layer is 200 nm to 230 nm; the preparation method of the waterproof vapor film layer includes the following steps: mixing silicon dioxide powder, alumina powder and magnesium fluoride powder and sintering them to form a composite material; using the composite material as a target material for magnetron sputtering to form the waterproof vapor film layer.

2. The aspherical lens for a methane laser according to claim 1, characterized in that, The diameter of the aspherical lens is 3mm to 5mm.

3. A method for fabricating an aspherical lens for a methane laser that prevents water vapor buildup, characterized in that, Includes the following steps: S1. Provides aspherical lenses; S2. Using a composite material of alumina, magnesium fluoride, and silicon dioxide as the target material, a waterproof vapor film layer is deposited on the surface of an aspherical lens using a magnetron sputtering process; the waterproof vapor film layer is a composite film composed of alumina, magnesium fluoride, and silicon dioxide; the mass percentage of alumina in the waterproof vapor film layer is 5%–10%, the mass percentage of magnesium fluoride is 10%–20%, and the mass percentage of silicon dioxide is 70%–80%; the thickness of the waterproof vapor film layer is 200 nm–230 nm.

4. The preparation method according to claim 3, characterized in that, In step S2, the preparation method of the composite material of alumina, magnesium fluoride, and silicon dioxide includes the following steps: (1) Mix silicon dioxide powder, aluminum oxide powder and magnesium fluoride powder and pre-sinter; (2) The material obtained after pre-sintering in step (1) is placed into a mold for secondary sintering to obtain a semi-finished product; (3) The semi-finished product obtained in step (2) is surface processed to make all surfaces of the semi-finished product flat, so as to obtain a composite material of alumina, magnesium fluoride and silicon dioxide.

5. The preparation method according to claim 4, characterized in that, In step (1), the mass ratio of silica powder, alumina powder, and magnesium fluoride powder is 1-2:2-4:14-16; the silica powder is prepared by the following method: mixing silicate ester with anhydrous ethanol, stirring, adding deionized water, adjusting the pH of the solution, adding surfactant, aging, and obtaining a gel; calcining the gel to obtain silica powder; the particle size of the silica powder is nanoscale; the particle size of the alumina powder is 1μm-5μm; the particle size of the magnesium fluoride powder is 1μm-5μm; the pre-sintering is carried out at a temperature of 1000℃-1300℃; the pre-sintering time is 8 hours-12 hours; In step (2), the secondary sintering is carried out under vacuum or inert atmosphere; the secondary sintering is carried out at a temperature of 1500℃; the pressure of the system is controlled to be maintained at 50MPa during the secondary sintering process; the composite material of alumina, magnesium fluoride and silicon dioxide is columnar with a diameter of 76.2mm and a height of 9mm.

6. The preparation method according to any one of claims 3 to 5, characterized in that, In step S1, the diameter of the aspherical lens is 3mm to 5mm; In step S2, the deposition process parameters for the waterproof vapor film layer are as follows: the magnetron sputtering power is controlled at 150W, the Ar inlet gas flow rate is 20 sccm, the outlet gas flow rate is 20 sccm, the sputtering vacuum degree is maintained at 0.4Pa, and the coating time is 2 h to 2.5 h.

7. A laser-driven methane sensor, characterized in that, The laser methane sensor includes the aspherical lens of the methane laser as described in claim 1 or 2, or the aspherical lens of the methane laser prepared by any one of claims 3 to 6.

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