Design method and preparation method of germanium substrate 2-5.9 mu m wave band cut-off 6.3-14 mu m high-transmittance optical filter film

Abstract

A design method and a preparation method of a germanium substrate 2-5.9 μm wave band cut 6.3-14 μm high-transmittance optical filter film are provided. The design method comprises the following steps: taking 550 nm as a reference wavelength of 1 / 4 wavelength thickness of optical film design, using: Sub / S1 surface 2.1(L2HL)^10, 2.8(L2HL)^10, 3.6(L2HL)^9, 4.5(L2HL)^9 / S2 surface.42(L2HLKL)^3,.59(K2LK)^1AIR, Sub is a germanium substrate, AIR represents air, H represents Ge, L represents ZnSe, and K represents YbF3; generating 75 layers of S1 surface and 12 layers of S2 surface, the S1 surface is bottomed with ZnSe, the outermost is ZnSe, and the intermediate is Ge and ZnSe alternately, and the S2 surface is Ge / ZnSe / Ge / ZnSe / Ge / ZnSe / YbF3 / ZnSe / Ge / ZnSe / YbF3 / ZnSe; optimization is performed to obtain the best film layer thickness; and a coating machine is input.

Description

Technical Field

[0001] This disclosure relates to the field of infrared optical thin film technology, and more specifically to a design and preparation method of a germanium substrate high-transmittance filter film with a wavelength cutoff of 6.3-14μm in the 2-5.9μm band. Background Technology

[0002] Germanium, as an infrared lens material, not only has excellent imaging performance in high and low temperature environments, but also has become increasingly widely used in germanium detectors with the development of the times. Germanium substrate filters are also advancing rapidly with various processing technologies, and market demand is constantly increasing. Due to the complex stress performance of germanium sheets, the film layer has poor durability, which forces continuous updates and improvements to the process. Compared with traditional germanium substrate film system designs, the same germanium substrate in the 2-14.5μm band generally fails to achieve optimal light transmission and interference capabilities due to differences in film layer design methods, and the film layer durability is also insufficient. Summary of the Invention

[0003] In view of the problems existing in the background art, one object of this disclosure is to provide a design method and a preparation method for a germanium substrate high transmittance filter film with a cutoff of 6.3-14μm in the 2-5.9μm band. This method enables the designed and prepared germanium substrate and the film system on both sides to achieve the target transmittance in the 2-5.9μm band and the 6.3-14μm band, and to pass the water immersion test and adhesion test.

[0004] Therefore, a design method for a germanium-based high-transmittance filter film with a cutoff of 6.3-14μm in the 2-5.9μm band includes the following steps: Sa, the film system design uses 550nm as the reference wavelength for 1 / 4 wavelength thickness in the optical film design, using the film stack expression: Sub / S1 film stack 2.1(L2HL)^10, 2.8(L2HL)^10, 3.6(L2HL)^9, 4.5(L2HL)^9 / S2 film stack .42(L2HLKL)^3, .59(K2LK)^1AIR, where Sub is the germanium substrate, AIR represents air, and in the film stack expression: H represents 1 / 4 wavelength thickness of high refractive index material Ge (germanium); L represents 1 / 4 wavelength thickness of low refractive index material ZnSe ( Zinc selenide); K represents YbF3 (ytterbium fluoride), a low-refractive-index material with a thickness of 1 / 4 wavelength; Sb, using the input film stack formula, generates a film structure with 75 layers on the S1 side and 12 layers on the S2 side. The S1 side consists of a base ZnSe, an outermost protective ZnSe layer, and alternating layers of Ge and ZnSe in the middle. The S2 side consists of Ge / ZnSe / Ge / ZnSe / Ge / ZnSe / YbF3 / ZnSe / Ge / ZnSe / YbF3 / ZnSe; Sc, using thin film design software, optimizes the film thickness to obtain the optimal film thickness. The optimized film structure achieves the target transmittance in the 2-5.9μm wavelength range with a cutoff of 6.3-14μm; Sd, inputs the optimized film thickness into the control computer of the coating machine.

[0005] A method for preparing a high-transmittance filter film with a germanium substrate and a wavelength cutoff of 6.3-14μm in the 2-5.9μm band includes the following steps: Step 1, cleaning the germanium substrate (used as a lens) and the accompanying coating material before deposition, and preparing three film materials: ZnSe, Ge, and YbF3; Step 2, configuring the deposition process conditions and process documents, including deposition temperature, pre-deposition base vacuum, film thickness, vapor deposition mode of the film material, deposition rate of the film material, and the use and parameters of ion source-assisted deposition, wherein the film thickness is based on the aforementioned germanium substrate with a wavelength cutoff of 6.3-14μm in the 2-5.9μm band. The design method for high-transmittance filter films includes the following steps: Step 3: The cleaned lens is placed into a fixture, which is then hung inside the coating machine cavity. The door is closed, and a vacuum is applied for heating. Step 4: The film material is pre-melted. Step 5: Ion source cleaning. Step 6: Film deposition and monitoring. The coating process conditions and process documents from Step 2 are used to deposit the film on the S2 surface of the lens. Step 7: The coating is kept at a constant temperature after deposition. Step 8: The part is cooled and removed. Step 9: Steps 1 to 8 are repeated to deposit the film on the S2 surface of the lens.

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

[0007] In the design method of the germanium substrate high transmittance filter film with a cutoff of 6.3-14μm in the 2-5.9μm band according to the present disclosure, through steps Sa to Sd, not only does the transmittance of the film structure in the 2-5.9μm band cutoff to the 6.3-14μm band reach the target, but also takes into account the testing process of the two-sided film system through water immersion test and adhesion test.

[0008] In the method for preparing a germanium substrate high-transmittance filter film with a cutoff of 6.3-14μm in the 2-5.9μm band according to the present disclosure, based on steps one to nine and the aforementioned design method for a germanium substrate high-transmittance filter film with a cutoff of 6.3-14μm in the 2-5.9μm band, the optimal film thickness stored in the control computer of the coating machine, as verified by testing, enables the prepared germanium substrate and the film system on both sides to achieve the target transmittance in the 2-5.9μm band cutoff to the 6.3-14μm band, and simultaneously passes the immersion test and adhesion test. Attached Figure Description

[0009] Figure 1 The transmittance curve is designed using the design method of the germanium substrate high transmittance filter film with a cutoff of 6.3-14μm in the 2-5.9μm band and a germanium substrate in Example 1.

[0010] Figure 2 This is a transmittance curve of the co-coated film and the film system on both sides after the preparation method of the germanium substrate high transmittance filter film with a wavelength cutoff of 6.3-14μm in the 2-5.9μm band of Example 1 is completed.

[0011] Figure 3 The images show the preparation method of the germanium substrate high-transmittance filter film with a wavelength cutoff of 6.3-14μm in the 2-5.9μm band of Example 1, and the photos of the substrate before and after the adhesion test and the water immersion test after the coating is completed. Detailed Implementation

[0012] It is understood that the disclosed embodiments are merely examples of this disclosure, which can be implemented in various forms. Therefore, the specific details disclosed herein should not be construed as limiting, but are intended only as the basis for the claims and as an illustrative basis to teach those skilled in the art how to implement this disclosure in various ways.

[0013] [Design method for high-transmittance filter films with a cutoff of 6.3-14μm in the 2-5.9μm band on germanium substrate]

[0014] The design method for a high-transmittance filter film with a wavelength cutoff of 6.3-14μm in the 2-5.9μm band on a germanium substrate, according to this disclosure, includes the following steps:

[0015] Sa, the film system design uses 550nm as the reference wavelength for 1 / 4 wavelength thickness in optical thin film design, using the film stack expression: Sub / S1 film stack 2.1(L2HL)^10, 2.8(L2HL)^10, 3.6(L2HL)^9, 4.5(L2HL)^9 / S2 film stack .42(L2HLKL)^3, .59(K2LK)^1AIR, where Sub is the germanium substrate, and AIR represents air. In the film stack expression:

[0016] H represents Ge (germanium), a high-refractive-index material with a thickness of 1 / 4 wavelength;

[0017] L represents ZnSe (zinc selenide), a low-refractive-index material with a thickness of 1 / 4 wavelength;

[0018] K represents YbF3 (ytterbium fluoride), a low-refractive-index material with a thickness of 1 / 4 wavelength;

[0019] Sb, through the input film stack formula, generates a film structure with 75 layers on the S1 side and 12 layers on the S2 side. The S1 side has a base ZnSe, an outermost protective ZnSe, and alternating layers of Ge and ZnSe in the middle. The S2 side has Ge / ZnSe / Ge / ZnSe / Ge / ZnSe / YbF3 / ZnSe / Ge / ZnSe / YbF3 / ZnSe.

[0020] Sc, by optimizing the film thickness using thin film design software, obtained the optimal film thickness. The optimized film structure has a cutoff of 6.3-14μm in the 2-5.9μm wavelength range, and the transmittance in the 2-5.9μm wavelength range reaches the target.

[0021] Sd inputs the optimized film thickness into the control computer of the coating machine.

[0022] In the design method of the germanium substrate high transmittance filter film with a cutoff of 6.3-14μm in the 2-5.9μm band according to the present disclosure, through steps Sa to Sd, not only does the transmittance of the film structure in the 2-5.9μm band cutoff and 6.3-14μm band reach the target, but also takes into account the water immersion test and adhesion test in the subsequent testing process of the two film systems.

[0023] In one example, in step Sc, the optimal film thicknesses for surfaces S1 and S2 are as follows:

[0024]

[0025]

[0026] In one example, in step Sc, the optimized film structure has an average transmittance of less than 1% in the 2-5.9 μm band and an average transmittance of greater than 88% in the 6.3-14 μm band.

[0027] In one example, in steps Sa to Sd, the software is designed as TFCalc or Essential Macleod.

[0028] [Preparation method of high-transmittance filter film with cutoff of 6.3-14μm in the 2-5.9μm band on germanium substrate]

[0029] The method for preparing a high-transmittance filter film with a wavelength cutoff of 6.3-14 μm in the 2-5.9 μm band on a germanium substrate according to this disclosure includes the following steps:

[0030] Step 1: Cleaning of the germanium substrate and the coating material used as the lens before plating, and preparation of the three coating materials: ZnSe, Ge, and YbF3.

[0031] Step 2, configuration of coating process conditions and process documents. The configuration of coating process conditions and process documents includes coating temperature, pre-coating base vacuum, film thickness, vapor deposition mode of film material, deposition rate of film material, use and parameters of ion source assisted deposition. Among them, the film thickness is based on the optimal film thickness stored in the control computer of the coating machine as described in the aforementioned design method of germanium substrate 2-5.9μm band cutoff 6.3-14μm high transmittance filter film.

[0032] Step 3: Place the cleaned lenses into the tooling fixture, hang the tooling fixture with the lenses in it into the cavity of the coating machine, close the door, and evacuate and heat.

[0033] Step 4: Pre-melting of the film material;

[0034] Step 5: Ion source cleaning;

[0035] Step 6, Coating and Monitoring: Coating is performed on the S2 surface of the lens according to the coating process conditions and process documents in Step 2.

[0036] Step 7: Maintain constant temperature after coating is completed;

[0037] Step 8: Cool down and remove the item;

[0038] Step nine: Repeat steps one through eight to apply a coating to the S2 surface of the lens.

[0039] In the method for preparing a germanium substrate high-transmittance filter film with a cutoff of 6.3-14μm in the 2-5.9μm band according to the present disclosure, based on steps one to nine and the aforementioned design method for a germanium substrate high-transmittance filter film with a cutoff of 6.3-14μm in the 2-5.9μm band, the optimal film thickness stored in the control computer of the coating machine, as verified by the subsequent tests, enables the prepared germanium substrate and the film system on both sides to achieve the target transmittance in the 2-5.9μm band cutoff to the 6.3-14μm band, and simultaneously passes the immersion test and adhesion test.

[0040] In one example, in step one, the product of step one is a (50±0.1)mm×(10±0.1)mm disc, and the accompanying plate is a (25±0.1)mm×(2±0.1)mm disc.

[0041] The cleaning in step one ensures a clean lens surface, which is beneficial for the adhesion and bonding of the coating. In one example, the lens is polished with an alumina polishing slurry, followed by ultrasonic cleaning with pure water. For instance, the alumina polishing slurry used is a 0.1μm polycrystalline diamond slurry from Nanjing Hengrui Precision Optics Co., Ltd.

[0042] In one example, in step two, the coating temperature is 150±2℃; the pre-coating base vacuum is (1.5±0.1)×10⁻⁶. -3 Pa; the film thickness in the coating process conditions and process documentation configuration is based on the optimal film thickness stored in the control computer of the coating machine as described in the aforementioned design method for high-transmittance filter films with a 2-5.9μm band cutoff of 6.3-14μm on a germanium substrate; the evaporation mode of the film materials is: ZnSe and YbF3 are evaporated using resistance heating, and Ge is evaporated using electron beam heating; the deposition rate of the film materials is: the deposition rate of the ZnSe film is... The deposition rate of the YbF3 film is: The deposition rate of the Ge film is The use of ion source-assisted deposition is as follows: the ion source is turned on for ZnSe and YbF3 film deposition, but not for Ge film deposition. Specifically, in step two, the ion source is a Hall source, and the parameters of the ion source are: neutralization current 1±0.01A, neutralization gas flow rate 10±0.01sccm, anode voltage 120±2V, anode current 2±0.01A, no oxygen is supplied throughout the process, and argon accounts for 100% of the neutralization gas.

[0043] In one example, in step two, for instance, the coating machine is a Leybold ARES1350.

[0044] In one example, in step three, a vacuum is first drawn to 5 × 10⁻⁶. -2 Pa, then the cavity of the coating machine is heated to 150°C and then maintained for 40 minutes.

[0045] Step four involves pre-melting the membrane material to remove gas and impurities, ensuring the purity of the membrane material. In step four, when the vacuum reaches (4.0-5.0)×10⁻⁶... -3 Three types of film materials were pre-melted at Pa. After pre-melting, the temperature of the coating machine cavity reached 150℃ and was maintained at a constant temperature for 10 minutes. In step four, the pre-melting treatment used both electron beam heating and resistance heating. For ZnSe film material, the resistance heating current was 720-760mA; for Ge film material, the electron beam heating current was 260-290mA; and for YbF3 film material, the resistance heating current was 860-900mA.

[0046] Step five, ion source cleaning, utilizes ion bombardment to clean the surface microstructure of the lens, eliminating the surface oxide layer and resulting in a cleaner surface, which is beneficial for the strong adhesion and growth of the film. In one example, in step five, a vacuum is drawn to achieve a vacuum level of 5.0 × 10⁻⁶ in the cavity. -3 Pa, start ion source cleaning. The ion source is a Hall source. The parameters of the ion source are: neutralization current 1±0.01A, neutralization gas flow rate 10±0.01sccm, anode voltage 120±2V, anode current 2±0.01A, argon gas content in the neutralization gas is 100%, and cleaning time is 5min.

[0047] In one example, in step six, when depositing each film layer, no gas is introduced from outside the coating machine into the cavity of the coating machine, and the cavity of the coating machine is kept evacuated, and the coating temperature is maintained at 150±2℃; each film layer is deposited at a temperature of 150±2℃ in the cavity of the coating machine; the film thickness is monitored by using the crystal oscillator method with the corresponding crystal oscillators of multiple crystal oscillators of the crystal controller; after ion source cleaning, the crystal controller controls the new crystal oscillator among the multiple crystal oscillators to work accordingly, and the crystal oscillator frequency is not less than 5850Hz.

[0048] In one example, in step seven, the cavity is kept at 150°C for 40 minutes after plating is completed.

[0049] In one example, in step eight, after step S7 is completed, the temperature is first lowered to 120°C at 1°C / min and held for 5 minutes, then lowered to 90°C at 1°C / min and held for 5 minutes, and then lowered to below 60°C at 1°C / min before the door is opened and the item is taken out.

[0050] [test]

[0051] Example 1

[0052] Part 1: Design Methods for High-Transmittance Filter Films with a Cutoff of 6.3-14μm in the 2-5.9μm Band on a Germanium Substrate

[0053] The design method for high-transmittance filter films with a wavelength cutoff of 6.3-14μm in the 2-5.9μm band on germanium substrates adopts the following steps:

[0054] Sa, the film system design uses 550nm as the reference wavelength for 1 / 4 wavelength thickness in optical thin film design. In TFCalc, the film stack expression is used: Sub / S1 film stack 2.1(L2HL)^10, 2.8(L2HL)^10, 3.6(L2HL)^9, 4.5(L2HL)^9 / S2 film stack .42(L2HLKL)^3, .59(K2LK)^1AIR, where Sub is the germanium substrate, and AIR represents air. In the film stack expression:

[0055] H represents Ge (germanium), a high-refractive-index material with a thickness of 1 / 4 wavelength;

[0056] L represents ZnSe (zinc selenide), a low-refractive-index material with a thickness of 1 / 4 wavelength;

[0057] K represents YbF3 (ytterbium fluoride), a low-refractive-index material with a thickness of 1 / 4 wavelength;

[0058] Sb, through the input film stack formula, generates a film structure with 75 layers on the S1 side and 12 layers on the S2 side. The S1 side has a base ZnSe, an outermost protective ZnSe, and alternating layers of Ge and ZnSe in the middle. The S2 side has Ge / ZnSe / Ge / ZnSe / Ge / ZnSe / YbF3 / ZnSe / Ge / ZnSe / YbF3 / ZnSe.

[0059] The film thickness was optimized using the thin film design software TFCalc to obtain the optimal film thickness. The optimized film structure achieved the target transmittance in the 2-5.9 μm wavelength range and the 6.3-14 μm wavelength range.

[0060] In step Sc, the film thicknesses of surfaces S1 and S2 are as follows:

[0061]

[0062]

[0063]

[0064] Sd inputs the optimized film thickness into the control computer of the coating machine, which is a Leybold ARES1350.

[0065] Part 2: Preparation method of high-transmittance filter films with a cutoff of 6.3-14μm in the 2-5.9μm band on germanium substrates

[0066] The preparation method of a germanium substrate high-transmittance filter film with a wavelength cutoff of 6.3-14μm in the 2-5.9μm band adopts the following steps:

[0067] Step 1: Cleaning of the germanium substrate and the accompanying coating for the lens before plating, and preparation of three types of film materials: ZnSe, Ge, and YbF3. The product is a 50mm×10mm disc, and the accompanying coating is a 25mm×2mm disc. The lens is polished with an alumina polishing solution and then ultrasonically cleaned with pure water. The alumina polishing solution used is 0.1μm polycrystalline diamond solution from Nanjing Hengrui Precision Optics Co., Ltd.

[0068] Step 2, configuration of coating process conditions and process documents. The configuration of coating process conditions and process documents includes coating temperature, pre-coating base vacuum, film thickness, vapor deposition mode of film material, deposition rate of film material, use and parameters of ion source assisted deposition. Among them, the film thickness is based on the optimal film thickness stored in the control computer of the coating machine as described in the design method of germanium substrate 2-5.9μm band cutoff 6.3-14μm high transmittance filter film in Part 1.

[0069] In step two,

[0070] The coating temperature is 150℃;

[0071] The base vacuum before plating is 1.5 × 10⁻⁶. -3 Pa;

[0072] The film thickness in the coating process conditions and process document configuration is based on the optimal film thickness stored in the control computer of the coating machine as described in the design method of the first part of the germanium substrate 2-5.9μm band cutoff 6.3-14μm high transmittance filter film;

[0073] The evaporation mode of the film material is as follows: ZnSe and YbF3 are evaporated using resistance heating, and Ge is evaporated using electron beam heating;

[0074] The deposition rate of the film material is: the deposition rate of the ZnSe film layer is The deposition rate of the YbF3 film is: The deposition rate of the Ge film is

[0075] The use of ion source-assisted deposition is as follows: the ion source is turned on for the vapor deposition of ZnSe and YbF3 films, but not for the vapor deposition of Ge films.

[0076] The ion source is a Hall source, and the parameters of the ion source are: neutralization current 1A, neutralization gas flow rate 10sccm, anode voltage 120V, anode current 2A, no oxygen is added throughout the process, and argon accounts for 100% of the neutralization gas.

[0077] Step 3: Place the cleaned lenses into the fixture, hang the fixture with the lenses inside the coating machine cavity, close the door, and first evacuate to 5×10. -2 Pa, then the cavity of the coating machine is heated to 150°C and then maintained for 40 minutes;

[0078] Step four, pre-melting of the film material, when the vacuum reaches 5.0×10 -3 Three types of film materials are pre-melted at Pa. After the film materials are pre-melted, the temperature of the cavity of the coating machine reaches 150℃ and is kept constant for 10 minutes.

[0079] In step four, the pre-melting process employs both electron beam heating and resistance heating.

[0080] For ZnSe film material, the resistance heating current is 740mA;

[0081] For Ge film materials, the electron beam heating current is 265mA;

[0082] For YbF3 film material, the resistance heating current is 880mA;

[0083] Step 5: Ion source cleaning, evacuation to achieve a vacuum level of 5.0 × 10⁻⁶ in the chamber. -3 Pa, start ion source cleaning. The ion source is a Hall source. The parameters of the ion source are: neutralization current 1A, neutralization gas flow rate 10sccm, anode voltage 120V, anode current 2A, argon gas content in the neutralization gas is 100%, and cleaning time is 5min.

[0084] Step Six: Coating and Monitoring. Following the coating process conditions and process documentation from Step Two, the coating is applied to the S2 surface of the lens.

[0085] In step six, when depositing each film layer, no gas is introduced from outside the coating machine into the cavity of the coating machine, and the cavity of the coating machine is kept evacuated, and the coating temperature is kept at 150°C.

[0086] Each film layer is deposited at a temperature of 150°C in the cavity of the coating machine;

[0087] The crystal oscillator method is used to monitor the film thickness by using the corresponding crystal oscillators of multiple crystal oscillators in the crystal controller. After cleaning with the ion source, the crystal controller controls the new crystal oscillator in the multiple crystal oscillators to work accordingly. The crystal oscillator frequency is 5990Hz.

[0088] Step 7: After plating is completed, keep the cavity at 150℃ for 40 minutes;

[0089] Step 8: After step S7 is completed, first lower the temperature to 120℃ at 1℃ / min and hold for 5 minutes, then lower the temperature to 90℃ at 1℃ / min and hold for 5 minutes, then lower the temperature to 60℃ at 1℃ / min and open the door to take out the part;

[0090] Step nine: Repeat steps one through eight to apply a coating to the S2 surface of the lens.

[0091] Figure 1 This is a transmittance curve designed using the design method of the germanium substrate high-transmittance filter film with a wavelength cutoff of 6.3-14μm in the 2-5.9μm band, as described in Example 1. From... Figure 1 It can be seen that the average transmittance of the germanium substrate and the film system on both sides is less than 1% in the 2-5.9μm band and greater than 88% in the 6.3-14μm band.

[0092] Figure 2 This is a transmittance curve of the substrate after coating is completed, showing the preparation method of the germanium substrate high-transmittance filter film with a wavelength cutoff of 6.3-14μm in the 2-5.9μm band of Example 1. Figure 1 It can be seen that the average transmittance of the substrate and the film system on both sides is less than 1% in the 2-5.9μm band and the average transmittance is 88.4% (i.e. greater than 88%) in the 6.3-14μm band.

[0093] The following overall performance test was conducted on the substrate of Example 1, along with the film system on both sides.

[0094] Water immersion test: Take tap water and conduct a water immersion test for 2 hours, and observe whether the film layer on each surface is peeled off or whether the film layer on each surface is cracked.

[0095] Adhesion test: Apply 3M tape by hand and pull the tape in the opposite direction to the adhesive end on each side to observe whether the film layer is pulled up.

[0096] The coating sheet of Example 1, along with the film system on both sides, passed the water immersion test and adhesion test.

[0097] Figure 3 The images show the preparation method of the germanium substrate high-transmittance filter film with a wavelength cutoff of 6.3-14μm in the 2-5.9μm band of Example 1, and the photos of the substrate and the film system on both sides before and after the adhesion test and the immersion test after the coating is completed.

[0098] Several exemplary embodiments have been described in detail above, but this document is not intended to limit itself to the explicitly disclosed combinations. Therefore, unless otherwise stated, the various features disclosed herein can be combined to form several other combinations, which are not shown for simplicity.

Claims

1. A method for preparing a high-transmittance filter film with a germanium substrate, having a wavelength cutoff of 6.3-14 μm in the 2-5.9 μm band, characterized in that, Including the following steps: Step 1: Cleaning of the germanium substrate and the coating material used as the lens before plating, and preparation of the three coating materials: ZnSe, Ge, and YbF3. Step two involves configuring the coating process conditions and documentation. This includes configuring the coating temperature, pre-coating vacuum, film thickness, vapor deposition mode of the coating material, deposition rate of the coating material, and the use and parameters of ion source-assisted deposition. The film thickness is based on the optimal film thickness stored in the coating machine's control computer. The optimal film thicknesses for the S1 and S2 planes of the membrane system are as follows: Step 3: Place the cleaned lenses into the tooling fixture, hang the tooling fixture with the lenses in it into the cavity of the coating machine, close the door, and evacuate and heat. Step 4: Pre-melting of the film material; Step 5: Ion source cleaning; Step 6, Coating and Monitoring: Coating is performed on the S2 surface of the lens according to the coating process conditions and process documents in Step 2. Step 7: Maintain constant temperature after coating is completed; Step 8: Cool down and remove the item; Step nine: Repeat steps one through eight to apply a coating to the S2 surface of the lens.

2. The method for preparing a germanium substrate high-transmittance filter film with a cutoff of 6.3-14μm in the 2-5.9μm band according to claim 1, characterized in that, In step one, The product is a (50±0.1)mm×(10±0.1)mm round piece, and the accompanying plate is a (25±0.1)mm×(2±0.1)mm round piece; The lenses are polished with aluminum oxide polishing solution and then ultrasonically cleaned with pure water. The alumina polishing slurry used is the 0.1μm polycrystalline diamond slurry from Nanjing Hengrui Precision Optics Co., Ltd.

3. The method for preparing a germanium substrate high-transmittance filter film with a wavelength cutoff of 6.3-14 μm in the 2-5.9 μm band according to claim 1, characterized in that, In step two, The coating temperature is 150±2°C; The base vacuum before plating was (1.5±0.1)×10 -3 Pa; The evaporation mode of the film material is as follows: ZnSe and YbF3 are evaporated using resistance heating, and Ge is evaporated using electron beam heating; The deposition rates of the films are as follows: the deposition rate of ZnSe film is 5 ± 0.2 Å / s, the deposition rate of YbF3 film is 3 ± 0.2 Å / s, and the deposition rate of Ge film is 3 ± 0.2 Å / s. The use of ion source-assisted deposition is as follows: the ion source is turned on for the vapor deposition of ZnSe and YbF3 films, but not for the vapor deposition of Ge films. The ion source is a Hall source, and the parameters of the ion source are: neutralization current 1±0.01A, neutralization gas flow rate 10±0.01sccm, anode voltage 120±2V, anode current 2±0.01A, no oxygen is supplied throughout the process, and argon accounts for 100% of the neutralization gas; The coating machine is a Leybold ARES1350.

4. The method for preparing a germanium substrate high-transmittance filter film with a cutoff of 6.3-14μm in the 2-5.9μm band according to claim 1, characterized in that, In step three, a vacuum is first drawn to 5×10. -2 Pa, then the cavity of the coating machine is heated to 150°C and then maintained for 40 minutes.

5. The method for preparing a germanium substrate high-transmittance filter film with a cutoff of 6.3-14μm in the 2-5.9μm band according to claim 1, characterized in that, In step four, when the vacuum reaches (4.0-5.0)×10 -3 Three types of film materials are pre-melted at Pa. After the film materials are pre-melted, the temperature of the cavity of the coating machine reaches 150°C and is kept constant for 10 minutes. In step four, the pre-melting process employs both electron beam heating and resistance heating. For ZnSe film material, the resistance heating current is 720-760mA; For Ge film materials, the electron beam heating current is 260-290mA; For YbF3 film material, the resistance heating current is 860-900mA.

6. The method for preparing a germanium substrate high-transmittance filter film with a cutoff of 6.3-14μm in the 2-5.9μm band according to claim 1, characterized in that, In step five, a vacuum is drawn to bring the vacuum level of the cavity to 5.0 × 10⁻⁶. -3 Pa, start ion source cleaning. The ion source is a Hall source. The parameters of the ion source are: neutralization current 1±0.01A, neutralization gas flow rate 10±0.01sccm, anode voltage 120±2V, anode current 2±0.01A, argon gas content in the neutralization gas is 100%, and cleaning time is 5min.

7. The method for preparing a germanium substrate high-transmittance filter film with a cutoff of 6.3-14μm in the 2-5.9μm band according to claim 1, characterized in that, In step six, When depositing each film layer, no gas is introduced from outside the coating machine into the cavity of the coating machine, and the cavity of the coating machine is kept evacuated, and the coating temperature is kept at 150±2°C. Each film layer is deposited at a temperature of 150±2°C in the cavity of the coating machine; The crystal oscillator method is used to monitor the film thickness by using the corresponding crystal oscillators of multiple crystal oscillators in the crystal controller. After cleaning with the ion source, the crystal controller controls the new crystal oscillator in the multiple crystal oscillators to work accordingly, and the crystal oscillator frequency is not less than 5850Hz.

8. The method for preparing a germanium substrate high-transmittance filter film with a cutoff of 6.3-14μm in the 2-5.9μm band according to claim 1, characterized in that, In step seven, after the plating is completed, the cavity is kept at 150°C for 40 minutes; In step eight, after step S7 is completed, the temperature is first lowered to 120°C at a rate of 1°C / min and held for 5 minutes, then lowered to 90°C at a rate of 1°C / min and held for 5 minutes, and then lowered to below 60°C at a rate of 1°C / min before the door is opened and the item is taken out.

Images