Preparation method of 3.7-4.8 [mu] m ultra-low reflective film system with germanium substrate

Abstract

The invention relates to a preparation method of a germanium substrate 3.7-4.8 [mu] m ultra-low reflective film system. The preparation method comprises the following steps: S1, cleaning accompanying plating sheets serving as germanium substrates of lenses and the surface of a product, wherein the accompanying plating sheets are circular sheets with the same thickness and wedge-shaped sheets of which the first surfaces are polished planes and the second surfaces are inclined planes with rough surfaces; s2, the treated lens is loaded into a tool clamp, the tool clamp is hung into a cavity of a vacuum coating machine, and the temperature of the cavity is set to be 150 DEG C; s3, the vacuum coating machine is vacuumized, and a Hall ion source is turned on for cleaning; s4, on the first surface of the lens, forming a five-layer film system according to five film materials including SiO, Ge, ZnS, YF3 and Y2O3; s5, after the first surface of the lens is plated with the film system, the cavity is naturally cooled to 60 DEG C or below, and the tool clamp and the lens are taken out; and S6, the step S1 to the step S5 are repeated, the second face of the lens is plated with the same film system, the wedge-shaped piece is not cleaned when the step S1 is repeated, and the wedge-shaped piece is not placed into the tool clamp when the step S2 is repeated.

Description

Technical Field

[0001] The present disclosure relates to the field of infrared coatings, and more specifically to a method for preparing a 3.7-4.8 μm ultra-low reflection film system on a germanium substrate. Background Art

[0002] Germanium is a commonly used material in infrared optics due to its excellent transmittance in the infrared band. In infrared imaging systems (such as infrared thermal imagers), germanium-based ultra-low-reflection films can significantly reduce reflections from component surfaces, improving the system's luminous flux and imaging contrast. This allows the thermal imager to more clearly capture the target's thermal radiation information. Germanium is widely used in security monitoring, industrial inspection, medical diagnosis, and military applications for night vision and target detection. In infrared guidance systems, germanium-based ultra-low-reflection films can enhance the optical system's ability to collect target infrared radiation, improving guidance accuracy. Therefore, further research and development of germanium-based ultra-low-reflection films is needed to minimize reflectivity. Furthermore, improving the environmental adaptability of products using germanium substrates is also a key development direction. Summary of the Invention

[0003] In view of the problems existing in the background technology, an object of the present disclosure is to provide a method for preparing a 3.7-4.8μm ultra-low reflection film system on a germanium substrate, wherein the prepared germanium substrate together with the film system on both sides can obtain ultra-low reflectivity in the 3.7-4.8μm band.

[0004] Another object of the present disclosure is to provide a method for preparing a 3.7-4.8μm ultra-low reflection film system on a germanium substrate, which can pass a total of eight tests including a water bubble test, a salt spray test, an adhesion test, a hot and cold shock test, a constant temperature and humidity test, a friction resistance test, a low temperature test, and a high temperature test, thereby improving the various environmental adaptability of products after coating on both sides of the germanium substrate.

[0005] Thus, a method for preparing a 3.7-4.8 μm ultra-low reflection film system on a germanium substrate includes the following steps: S1, cleaning the surfaces of a germanium substrate and a product, wherein the accompanying coating sheet is a circular sheet of uniform thickness and a wedge-shaped sheet with a polished first surface and a roughened second surface; S2, loading the processed lens into a fixture, and hanging the fixture with the lens into the cavity of a vacuum coating machine, wherein the temperature of the cavity is set to 150°C; S3, starting the vacuum coating machine to evacuate the film, and the vacuum degree reaches 1.0×10 -3Pa, the Hall ion source of the vacuum coating machine was turned on for cleaning, the cleaning time was 6 minutes, and the parameters of the Hall ion source were: anode voltage of 220V, anode current of 1.2A, neutralization current of 1.5A, neutralization gas flow rate of 10sccm, and argon gas flow rate of 100%; S4, on the first side of the lens, a five-layer film system consisting of five film materials of SiO, Ge, ZnS, YF3 and Y2O3 was prepared, with a thickness of 142.88nmSiO / 61.85nmGe / 10 9.65nmZnS / 656.45nmYF3 / 15nmY2O3, the film layers are deposited in sequence, where the numbers in nm before SiO, Ge, ZnS, YF3 and Y2O3 are the film thicknesses of the corresponding films. The SiO film, Ge film and Y2O3 film are evaporated by electron beam heating, while the ZnS film and YF3 film are evaporated by resistance heating. The deposition rate of the SiO film is 0.6nm / s, the deposition rate of the Ge film is 0.3nm / s, and the deposition rate of the ZnS film is 0.6nm / s. The deposition rate of the S film layer is 0.8 nm / s, the deposition rate of the YF3 film layer is 0.3 nm / s, and the deposition rate of the Y2O3 film layer is 0.4 nm / s. Each film layer is deposited with the assistance of an ion source, and each film layer is deposited at a chamber temperature of 150°C; S5, after the film system is coated on the first side of the lens, the chamber is naturally cooled to below 60°C, and the fixture is taken out together with the lens; S6, repeat steps S1 to S5, and coat the same film system on the second side of the lens, wherein the wedge is not cleaned when repeating step S1 and the fixture is not placed when repeating step S2.

[0006] The beneficial effects of the present disclosure are as follows.

[0007] In the method for preparing a 3.7-4.8μm ultra-low reflection film system on a germanium substrate according to the present disclosure, the same Sub (germanium substrate) SiO / Ge / ZnS / YF3 / Y2O3 / Air (air) five-layer film system is plated on both sides of the germanium substrate through steps S1 to S6. The prepared germanium substrate together with the film system on both sides can obtain an ultra-low reflectivity in the 3.7-4.8μm band. As verified by the test process, the reflectivity can reach below 0.3%. In addition, as verified by the test process, the prepared germanium substrate together with the film system on both sides can pass a total of eight tests including a water bubble test, a salt spray test, an adhesion test, a hot and cold shock test, a constant temperature and humidity test, a friction resistance test, a low temperature test, and a high temperature test, thereby improving the various environmental adaptability of the product after the germanium substrate is plated on both sides. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a schematic structural diagram of a germanium substrate and the film systems on both sides prepared according to the method for preparing a 3.7-4.8 μm ultra-low reflection film system on a germanium substrate disclosed in the present invention.

[0009] Figure 2 This is a photo of the wedge-shaped piece in the accompanying plating film.

[0010] Figure 3 It is a curve diagram of the reflectivity of the wedge-shaped plate in the accompanying coating plate of Example 1 and the film system corresponding to the first surface. DETAILED DESCRIPTION

[0011] The accompanying drawings show embodiments of the present disclosure, and it will be understood that the disclosed embodiments are merely examples of the present disclosure, which can be implemented in various forms. Therefore, the specific details disclosed herein should not be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one of ordinary skill in the art to implement the present disclosure in various ways.

[0012] [Preparation method of 3.7-4.8μm ultra-low reflection film system on germanium substrate]

[0013] Reference Figure 1 and Figure 2 According to the present disclosure, the method for preparing a 3.7-4.8 μm ultra-low reflection film system on a germanium substrate comprises the following steps:

[0014] S1, cleaning the surfaces of the accompanying plated sheet and the product as the germanium substrate of the lens, wherein the accompanying plated sheet is a circular sheet of uniform thickness and a wedge-shaped sheet with a polished flat surface on the first side and a roughened, matte surface on the second side;

[0015] S2, the processed lens is loaded into the fixture, and the fixture with the lens is hung in the vacuum coating machine cavity, and the cavity temperature is set to 150 ° C;

[0016] S3, vacuum coating machine starts to evacuate, and the vacuum degree reaches 1.0×10 -3 Pa, open the Hall ion source of the vacuum coating machine for cleaning, the cleaning time is 6 minutes, the parameters of the Hall ion source are: anode voltage 220V, anode current 1.2A, neutralization current 1.5A, neutralization gas flow rate 10sccm, and argon gas flow rate ratio 100%;

[0017] S4, on the first side of the lens, a five-layer film system consisting of five film materials: SiO, Ge, ZnS, YF3 and Y2O3

[0018] 142.88nmSiO / 61.85nmGe / 109.65nmZnS / 656.45nmYF3 / 15nmY2O3, sequentially depositing each film layer,

[0019] Among them, the numbers in nm before SiO, Ge, ZnS, YF3 and Y2O3 are the film thicknesses of the corresponding film layers. The SiO film layer, Ge film layer and Y2O3 film layer are evaporated by electron beam heating, and the ZnS film layer and YF3 film layer are evaporated by resistance heating. The deposition rate of the SiO film layer is 0.6 nm / s, the deposition rate of the Ge film layer is 0.3 nm / s, the deposition rate of the ZnS film layer is 0.8 nm / s, the deposition rate of the YF3 film layer is 0.3 nm / s, and the deposition rate of the Y2O3 film layer is 0.4 nm / s. All film layers are deposited by ion source assisted deposition, and the deposition of each film layer is completed at a chamber temperature of 150°C.

[0020] S5, after the coating system on the first side of the lens is completed, the chamber is cooled naturally to below 60°C, and the fixture and the lens are taken out;

[0021] S6, repeating steps S1 to S5, coating the same film system on the second surface of the lens, wherein the wedge is not cleaned when repeating step S1 and is not placed in a fixture when repeating step S2.

[0022] In the method for preparing a 3.7-4.8μm ultra-low reflection film system on a germanium substrate according to the present disclosure, the same Sub (germanium substrate) SiO / Ge / ZnS / YF3 / Y2O3 / Air (air) five-layer film system is plated on both sides of the germanium substrate through steps S1 to S6. The prepared germanium substrate together with the film system on both sides can obtain an ultra-low reflectivity in the 3.7-4.8μm band. As verified by the test process, the reflectivity can reach below 0.3%. In addition, as verified by the test process, the prepared germanium substrate together with the film system on both sides can pass a total of eight tests including a water bubble test, a salt spray test, an adhesion test, a hot and cold shock test, a constant temperature and humidity test, a friction resistance test, a low temperature test, and a high temperature test, thereby improving the various environmental adaptability of the product after the germanium substrate is plated on both sides.

[0023] The cleaning in step S1 helps improve the surface condition of each surface of the lens and helps enhance the bonding performance between the coatings on each surface and the corresponding surface of the lens. In step S1, for example, the lens surface is cleaned using ultrasound or manual rubbing. Specifically, in step S1, the ultrasonic cleaning of the lens surface involves polishing with an aluminum oxide polishing solution followed by ultrasonic pure water rinsing. For example, in step S1, the aluminum oxide polishing solution used is a 0.1μm polycrystalline diamond solution from Nanjing Henry Precision Optics Co., Ltd.

[0024] In step S1, for example, the product is a lens or a flat sheet. In step S1, for example, the thickness of the disc in the accompanying plating sheet is 2 mm.

[0025] The temperature setting of the vacuum coating machine in step S2 heats the lens through the cavity of the coating machine, which helps the growth of the film layer from the lens and reduces the film growth stress.

[0026] In step S3, a Hall ion source is used for cleaning, which will separate the impurities and oil molecules adsorbed on the surface of each surface of the lens from the substrate surface, thereby greatly improving the interface state and helping to improve the bonding performance between the film layer and the corresponding surface of the lens. At the same time, cleaning by the Hall ion source can heat the corresponding surface of the lens, which helps the film layer grow from the lens and reduces the film growth stress.

[0027] In step S4, in one example, the ion source adopts a Hall ion source. When the SiO film is deposited, the ion source parameters are: neutralization current of 0.5A, neutralization gas flow rate of 6-8sccm, anode voltage of 120V, anode current of 1.2A, argon flow rate of 30%, and oxygen flow rate of 70%; when the Ge film is deposited, the ion source parameters are: neutralization current of 0.5A, neutralization gas flow rate of 6-8sccm, anode voltage of 120V, anode current of 1.0A, and argon flow rate of 100%; when the ZnS film is deposited, the ion source parameters are: neutralization current of 0.5A, neutralization gas flow rate of 6-8sccm, anode voltage of 120V, anode current of 1.0A, and argon flow rate of 100%. A, the neutralization gas flow rate is 8 sccm, the anode voltage is 120 V, the anode current is 1.2 A, and the argon flow rate accounts for 100%; when depositing the YF3 film, the ion source parameters are: the neutralization current is 0.5 A, the neutralization gas flow rate is 10 sccm, the anode voltage is 120 V, the anode current is 1.2 A, and the argon flow rate accounts for 100%; when depositing the Y2O3 film, the ion source parameters are: the neutralization current is 0.5 A, the neutralization gas flow rate is 10 sccm, the anode voltage is 100 V, the anode current is 1.2 A, the argon flow rate accounts for 30%, and the oxygen flow rate accounts for 70%.

[0028] In step S4, in one example, argon gas is introduced and vacuum is drawn to maintain a constant flow vacuum when depositing each film layer. The constant flow vacuum is set to no less than 5.0×10 -3 Pa.

[0029] In step S4, in one example, the crystal oscillator method is used to monitor the film thickness using the corresponding crystal oscillator pieces of the multiple crystal oscillator pieces of the crystal controller. After the ion source is cleaned, the crystal controller controls the corresponding operation of the new crystal oscillator pieces among the multiple crystal oscillator pieces, and the crystal oscillator frequency is not less than 5.99 MHz.

[0030] After step S6 is completed, in one example, the wedge-shaped sheet in the accompanying plating sheet and the film corresponding to the first surface have an average reflectivity in the 3.7-4.8 μm band below 0.3%.

[0031] After step S6 is completed, in one example, the wafer in the accompanying plating sheet together with the films on both sides pass the blister test, salt spray test, adhesion test, hot and cold shock test, constant temperature and humidity test, friction resistance test, low temperature test, and high temperature test.

[0032] [test]

[0033] Example 1

[0034] The method for preparing the 3.7-4.8 μm ultra-low reflection film system on a germanium substrate of Example 1 comprises the following steps:

[0035] S1. Ultrasonic cleaning is performed on the surfaces of the accompanying plated sheet and the product, which serves as the germanium substrate of the lens. The accompanying plated sheet is a circular sheet of uniform thickness and a wedge-shaped sheet with a polished flat first surface and a roughened, beveled second surface. The thickness of the circular sheet in the accompanying plated sheet is 2 mm. The product is a lens. Ultrasonic cleaning of the lens surface is performed by polishing with an aluminum oxide polishing liquid, followed by ultrasonic pure water cleaning. The aluminum oxide polishing liquid is a 0.1 μm polycrystalline diamond liquid from Nanjing Henry Precision Optics Co., Ltd.

[0036] S2, loading the processed lens into a fixture, and then hanging the fixture with the lens into the chamber of a vacuum coating machine. The temperature of the chamber is set to 150°C. The vacuum coating machine is a vacuum coating machine equipped with a Hall ion source manufactured and sold by Chengdu Siwork Vacuum Technology Co., Ltd.

[0037] S3, vacuum coating machine starts to evacuate, and the vacuum degree reaches 1.0×10 -3 Pa, open the Hall ion source of the vacuum coating machine for cleaning, the cleaning time is 6 minutes, the parameters of the Hall ion source are: anode voltage 220V, anode current 1.2A, neutralization current 1.5A, neutralization gas flow rate 10sccm, and argon gas flow rate ratio 100%;

[0038] S4, on the first side of the lens, a five-layer film system consisting of five film materials: SiO, Ge, ZnS, YF3 and Y2O3

[0039] 142.88nmSiO / 61.85nmGe / 109.65nmZnS / 656.45nmYF3 / 15nmY2O3, sequentially depositing each film layer,

[0040] Among them, the numbers with nm before SiO, Ge, ZnS, YF3 and Y2O3 are the film thicknesses of the corresponding films. The SiO film, Ge film and Y2O3 film are evaporated by electron beam heating, and the ZnS film and YF3 film are evaporated by resistance heating. The deposition rate of the SiO film is 0.6nm / s, the deposition rate of the Ge film is 0.3nm / s, the deposition rate of the ZnS film is 0.8nm / s, the deposition rate of the YF3 film is 0.3nm / s, and the deposition rate of the Y2O3 film is 0.4nm / s. Each film layer is deposited by ion source assisted deposition, and each film layer is deposited at a chamber temperature of 150°C.

[0041] The ion source adopts Hall ion source.

[0042] When depositing the SiO film, the ion source parameters are: neutralization current 0.5A, neutralization gas flow rate 7sccm, anode voltage 120V, anode current 1.2A, argon flow rate 30%, and oxygen flow rate 70%.

[0043] When depositing the Ge film, the ion source parameters are: neutralization current of 0.5 A, neutralization gas flow rate of 7 sccm, anode voltage of 120 V, anode current of 1.0 A, and argon gas flow rate of 100%;

[0044] When depositing the ZnS film, the ion source parameters are: neutralization current of 0.5 A, neutralization gas flow rate of 8 sccm, anode voltage of 120 V, anode current of 1.2 A, and argon gas flow rate of 100%;

[0045] When depositing the YF3 film, the ion source parameters are: neutralization current of 0.5 A, neutralization gas flow rate of 10 sccm, anode voltage of 120 V, anode current of 1.2 A, and argon gas flow rate of 100%;

[0046] When depositing the Y2O3 film, the ion source parameters are: neutralization current 0.5A, neutralization gas flow rate 10sccm, anode voltage 100V, anode current 1.2A, argon flow rate 30%, and oxygen flow rate 70%.

[0047] When depositing each film layer, argon gas was introduced and vacuum was drawn to maintain the flow constant vacuum. The flow constant vacuum was set to 5.0×10 -3 Pa;

[0048] The film thickness is monitored using the crystal oscillator method using the corresponding crystal oscillator of the multiple crystal oscillators of the crystal controller. After the ion source is cleaned, the crystal controller controls the corresponding operation of the new crystal oscillator among the multiple crystal oscillators, and the crystal oscillator frequency is not less than 5.99MHz;

[0049] S5, after the coating system on the first side of the lens is completed, the chamber is naturally cooled to 60°C, and the fixture and the lens are taken out;

[0050] S6, repeating steps S1 to S5, coating the same film system on the second surface of the lens, wherein the wedge is not cleaned when repeating step S1 and is not placed in a fixture when repeating step S2.

[0051] The wedge-shaped piece in the accompanying plating sheet of Example 1 is used to test the reflectivity. Figure 3 This is a graph showing the reflectivity of the wedge-shaped sheet in the accompanying coating sheet of Example 1 together with the film system corresponding to the first surface. Figure 3 It can be seen that the reflectivity of the wedge-shaped sheet in the accompanying plating sheet together with the film system corresponding to the first surface in the 3.7-4.8 μm band is less than 0.3% on average, specifically 0.26%.

[0052] The following tests were performed after coating on both sides of the disc in the accompanying coating sheet of Example 1.

[0053] Water bubble test: Take tap water to conduct a water bubble test for 2 hours to observe whether the film layers on each surface of the disc in the accompanying plating sheet fall off from the disc in the accompanying plating sheet, and observe whether the film layers on each surface of the disc in the accompanying plating sheet are cracked.

[0054] Salt spray test: neutral salt spray test for 48 hours, observe whether the film layer on each surface of the disc in the accompanying plating sheet falls off, and observe whether the film layer on each surface of the disc in the accompanying plating sheet cracks.

[0055] Adhesion test: Use hand to stick 3M tape on each side of the disc in the accompanying plating sheet and pull the tape in the direction opposite to the sticking end to observe whether the film layer is pulled up.

[0056] Thermal shock test: In a high and low temperature box, perform thermal shock test in the range of -40℃ to 85℃ for 24 hours to observe whether the film layers on each surface of the discs in the accompanying plating sheet fall off or crack.

[0057] Constant temperature and humidity test: In a constant temperature and humidity chamber, at 50°C and 95% relative humidity for 48 hours, observe whether the film layers on each surface of the discs in the accompanying plating sheet fall off or crack.

[0058] Friction resistance test (moderate friction test): Wrap the rubber friction head of the friction machine with degreased cloth, apply a pressure of 4.9N on the film surface of the accompanying plating sheet and rub it 50 times (25 back and forth), and observe whether there are any signs of scratches or damage on the surface of the film layer.

[0059] Low temperature test: In a low temperature box, at -40℃ for 48 hours, observe whether the film layers on each surface of the discs in the accompanying plating sheet fall off, and observe whether the film layers on each surface of the discs in the accompanying plating sheet crack.

[0060] High temperature test: In a high temperature box, at 85℃ for 48h, observe whether the film layers on each surface of the discs in the accompanying plating sheet fall off, and observe whether the film layers on each surface of the discs in the accompanying plating sheet crack.

[0061] The film showed no signs of peeling or cracking in the blister test, salt spray test, thermal shock test, constant temperature and humidity test, low temperature test, and high temperature test. The film did not lift in the adhesion test, and showed no signs of scratch damage in the abrasion test, indicating moderate abrasion resistance. In other words, the disc and the films on both sides of the accompanying plating sheet of Example 1 passed eight tests: the blister test, salt spray test, adhesion test, thermal shock test, constant temperature and humidity test, abrasion test, low temperature test, and high temperature test.

[0062] The above detailed description is used to describe a number of exemplary embodiments, but this document is not intended to be limited to the explicitly disclosed combinations. Therefore, unless otherwise stated, the various features disclosed herein may be combined to form multiple additional combinations that are not shown for the sake of brevity.

Claims

1. A method for preparing a 3.7-4.8 μm ultra-low reflection film system on a germanium substrate, characterized in that: Including steps: S1, cleaning the surfaces of the accompanying plated sheet and the product as the germanium substrate of the lens, wherein the accompanying plated sheet is a circular sheet of uniform thickness and a wedge-shaped sheet with a polished flat surface on the first side and a roughened, matte surface on the second side; S2, the processed lens is loaded into the fixture, and the fixture with the lens is hung in the vacuum coating machine cavity, and the cavity temperature is set to 150 ° C; S3, vacuum coating machine starts to evacuate, and the vacuum degree reaches 1.0×10 -3 Pa, open the Hall ion source of the vacuum coating machine for cleaning, the cleaning time is 6 minutes, the parameters of the Hall ion source are: anode voltage 220V, anode current 1.2A, neutralization current 1.5A, neutralization gas flow rate 10sccm, and argon gas flow rate ratio 100%; S4, on the first side of the lens, a five-layer film system consisting of five film materials: SiO, Ge, ZnS, YF3 and Y2O3 142.88nmSiO / 61.85nmGe / 109.65nmZnS / 656.45nmYF3 / 15nmY2O3, sequentially depositing each film layer, Among them, the numbers in nm before SiO, Ge, ZnS, YF3 and Y2O3 are the film thicknesses of the corresponding film layers. The SiO film layer, Ge film layer and Y2O3 film layer are evaporated by electron beam heating, and the ZnS film layer and YF3 film layer are evaporated by resistance heating. The deposition rate of the SiO film layer is 0.6 nm / s, the deposition rate of the Ge film layer is 0.3 nm / s, the deposition rate of the ZnS film layer is 0.8 nm / s, the deposition rate of the YF3 film layer is 0.3 nm / s, and the deposition rate of the Y2O3 film layer is 0.4 nm / s. All film layers are deposited by ion source assisted deposition, and the deposition of each film layer is completed at a chamber temperature of 150°C. S5, after the coating system on the first side of the lens is completed, the chamber is cooled naturally to below 60°C, and the fixture and the lens are taken out; S6, repeating steps S1 to S5, coating the same film system on the second surface of the lens, wherein the wedge is not cleaned when repeating step S1 and is not placed in a fixture when repeating step S2.

2. The method for preparing a 3.7-4.8 μm ultra-low reflection film system on a germanium substrate according to claim 1, characterized in that: In step S1, the surface of the lens is cleaned by ultrasonic wave or hand wiping.

3. The method for preparing a 3.7-4.8 μm ultra-low reflection film system on a germanium substrate according to claim 2, characterized in that: In step S1, the surface of the lens is cleaned by ultrasonic wave by polishing with aluminum oxide polishing liquid and then cleaning with ultrasonic pure water.

4. The method for preparing a 3.7-4.8 μm ultra-low reflection film system on a germanium substrate according to claim 3, characterized in that: In step S1 , the aluminum oxide polishing liquid adopts a 0.1 μm polycrystalline diamond liquid produced by Nanjing Henry Precision Optics Co., Ltd.

5. The method for preparing a 3.7-4.8 μm ultra-low reflection film system on a germanium substrate according to claim 1, characterized in that: In step S1 , the product is a lens or a flat sheet.

6. The method for preparing a 3.7-4.8 μm ultra-low reflection film system on a germanium substrate according to claim 1, characterized in that: In step S1 , the thickness of the disc in the accompanying plating sheet is 2 mm.

7. The method for preparing a 3.7-4.8 μm ultra-low reflection film system on a germanium substrate according to claim 1, characterized in that: In step S4, The ion source adopts Hall ion source. When depositing the SiO film, the ion source parameters are: neutralization current 0.5A, neutralization gas flow rate 6-8sccm, anode voltage 120V, anode current 1.2A, argon flow rate 30%, and oxygen flow rate 70%. When depositing the Ge film, the ion source parameters are: neutralization current of 0.5 A, neutralization gas flow rate of 6-8 sccm, anode voltage of 120 V, anode current of 1.0 A, and argon gas flow rate of 100%; When depositing the ZnS film, the ion source parameters are: neutralization current of 0.5 A, neutralization gas flow rate of 8 sccm, anode voltage of 120 V, anode current of 1.2 A, and argon gas flow rate of 100%; When depositing the YF3 film, the ion source parameters are: neutralization current of 0.5 A, neutralization gas flow rate of 10 sccm, anode voltage of 120 V, anode current of 1.2 A, and argon gas flow rate of 100%; When depositing the Y2O3 film, the ion source parameters are: neutralization current of 0.5A, neutralization gas flow rate of 10sccm, anode voltage of 100V, anode current of 1.2A, argon flow rate of 30%, and oxygen flow rate of 70%.

8. The method for preparing a 3.7-4.8 μm ultra-low reflection film system on a germanium substrate according to claim 1, characterized in that: In step S4, When coating each film layer, argon gas is introduced and vacuum is drawn to maintain the flow constant vacuum. The flow constant vacuum setting is not less than 5.0×10 -3 Pa; The crystal oscillator method is used to monitor the film thickness using the corresponding crystal oscillator pieces of the multiple crystal oscillator pieces of the crystal controller. After the ion source is cleaned, the crystal controller controls the corresponding operation of the new crystal oscillator pieces among the multiple crystal oscillator pieces, and the crystal oscillator frequency is not less than 5.99MHz.

9. The method for preparing a 3.7-4.8 μm ultra-low reflection film system on a germanium substrate according to claim 1, characterized in that: After step S6 is completed, the wedge-shaped sheet in the accompanying coating sheet and the film system corresponding to the first surface have an average reflectivity of less than 0.3% in the 3.7-4.8 μm band; After step S6 is completed, the wafers in the accompanying plating sheet together with the films on both sides pass the blister test, salt spray test, adhesion test, hot and cold shock test, constant temperature and humidity test, friction resistance test, low temperature test, and high temperature test.

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