Method for preparing medium-wave infrared bandpass filter

Abstract

The invention discloses a method for preparing a medium-wave infrared bandpass filter, the method comprising the following steps: placing a substrate in a vacuum chamber of a coating machine to heat the substrate; evacuating to below 2×10E‑3Pa; alternately stacking 22 layers of high refractive index film layers and low refractive index film layers on both sides of the substrate to form a main film system and 40 layers of high refractive index film layers and low refractive index film layers to form a secondary film system by a physical vapor deposition method; after forming the main film system and the secondary film system, annealing is performed to complete the preparation of the medium-wave infrared bandpass filter; wherein the medium-wave infrared bandpass filter has a light transmission effect in the wavelength range of 4.5 to 5.0 μm, with an average transmittance of more than 92%, and is highly cut off in the 1 to 4.2 μm and 5.3 to 7.5 μm bands, with an average transmittance of less than 1%. The signal-to-noise ratio can be well improved, the signal strength can be enhanced, and the detector response rate can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of filter preparation, and in particular to a method for preparing a medium-wave infrared bandpass filter. Background Art

[0002] Optical bandpass filters are very important optical equipment components. Their main function is to divide the spectrum within a certain range into two parts. One part that does not allow light to pass through is called the cutoff area, and the other part that requires light to pass through fully is called the bandpass area. Bandpass filters play a very important role in various optical systems. Infrared bandpass filters are mainly used in infrared spectrum detection systems. They have the function of filtering out background clutter and are of great significance for improving the signal-to-noise ratio and improving the performance of optical systems. For example, medium-wave infrared bandpass filters have very important applications in aerospace and military fields. However, in the prior art, infrared detection products in the 4.5-5.0μm band cannot meet the requirements of high anti-interference capabilities, and there is a lack of filters in the 4.5-5.0μm band and methods for making the filters. Summary of the invention

[0003] In view of the above-mentioned shortcomings, the present invention provides a method for preparing a medium-wave infrared bandpass filter. The prepared medium-wave infrared bandpass filter can have a good light transmittance effect in the wavelength range of 4.5 to 5.0 μm, with an average transmittance of >92%, and has a high cutoff effect in the 1 to 4.2 μm and 5.3 to 7.5 μm bands, with an average transmittance of <1%.

[0004] To achieve the above object, the embodiments of the present invention adopt the following technical solutions:

[0005] A method for preparing a medium-wave infrared bandpass filter, the method comprising the following steps:

[0006] Placing the substrate into a vacuum chamber of a coating machine to heat the substrate;

[0007] Evacuate to below 2×10E-3Pa;

[0008] By means of physical vapor deposition, 22 layers of high-refractive-index film layers and low-refractive-index film layers with preset film thicknesses are alternately deposited outward on one side of the substrate to form a main film system;

[0009] By physical vapor deposition, 40 layers of high-refractive-index film layers and low-refractive-index film layers with preset film thicknesses are alternately deposited outward on the other side of the substrate to form a secondary film system;

[0010] After the main film system and the secondary film system are formed, annealing is performed to complete the preparation of the medium-wave infrared bandpass filter;

[0011] The medium-wave infrared bandpass filter has a light-transmitting effect in the wavelength range of 4.5 to 5.0 μm, with an average transmittance of more than 92%, and is highly cut off in the wavelength ranges of 1 to 4.2 μm and 5.3 to 7.5 μm, with an average transmittance of less than 1%.

[0012] According to one aspect of the present invention, the film system structure of the main film system is: substrate / 100nmH, 981.15nmL, 260.54nmH, 818.82nmL, 423.4nmH, 538.62nmL, 400.43nmH, 781.62nmL, 298.85nmH, 694.75nmL, 403.62nmH, 667.75nmL, 347.66nmH, 731.58nmL, 382.17nmH, 625.62nmL, 452.13nmH, 674.99nmL, 595.49nmH, 1098.45nmL, 286.06nmH, 496.05nmL / air; wherein H represents a high refractive index film layer, L represents a low refractive index film layer, and the numbers before H and L are the thickness of the film layer.

[0013] According to one aspect of the present invention, the film structure of the secondary film is: substrate / 100nmH, 169.81nmL, 154.76nmH, 259.89nmL, 95.34nmH, 206.72nmL, 134.06nmH, 206.41nmL, 135.87nmH, 254.68nmL, 127.89nmH, 75.57nmL, 87.07nmH, 252.36nmL, 155.39nmH, 257.11nmL, 136.54nmH, 267.54nmL, 182.39nmH, 311.22nmL, 136.12nm H, 252.39nmL, 173.42nmH, 344.56nmL, 187.76nmH, 483.27nmL, 165.85nmH, 380.84nmL, 307.22nmH, 404.6nmL, 143.22nmH, 511.18nmL, 197.25nmH, 389.52nmL, 350.9nmH, 211.97nmL, 209.51nmH, 361.78nmL, 347.58nmH, 595.17nmL / air; wherein H represents a high refractive index film layer, L represents a low refractive index film layer, and the numbers before H and L are the thickness of the film layer.

[0014] According to one aspect of the present invention, the substrate is a germanium substrate.

[0015] According to one aspect of the present invention, the high refractive index film layer is a germanium film layer, and the low refractive index film layer is a zinc sulfide film layer.

[0016] According to one aspect of the present invention, the germanium material used in the germanium film layer is evaporated by electron gun evaporation; the zinc sulfide material used in the zinc sulfide film layer is evaporated by resistance boat thermal evaporation.

[0017] According to one aspect of the present invention, the evaporation rate of the germanium material is controlled within 10 A / s; the evaporation rate of the zinc sulfide material is controlled within 10 A / s.

[0018] According to one aspect of the present invention, placing the substrate in a vacuum chamber of a coating machine to heat the substrate includes: placing the substrate in a vacuum chamber of the coating machine to bake and heat the substrate, and the baking temperature is set to 160°C.

[0019] According to one aspect of the present invention, the method further comprises: using an ion source to assist in cleaning the substrate surface before coating.

[0020] According to one aspect of the present invention, the method further comprises: during film deposition, using a quartz crystal oscillator to monitor film thickness.

[0021] The advantages of the implementation of the present invention are as follows: 22 layers of high refractive index film layers and low refractive index film layers are alternately stacked on one side of a substrate by physical vapor deposition to form a main film system, and 40 layers of high refractive index film layers and low refractive index film layers are alternately stacked on the other side of the substrate by physical vapor deposition to form a secondary film system, so as to prepare a medium-wave infrared bandpass filter; the prepared medium-wave infrared bandpass filter has a bandpass spectral range of 4.5-5.0 μm and an average transmittance of more than 92%; a cut-off spectral range of 1-4.2 μm and 5.3-7.5 μm, and an average transmittance of less than 1%, which can well improve the signal-to-noise ratio, enhance the signal strength, and improve the detector response rate; and can be used in various infrared optical detection systems to reduce the influence of background clutter, enhance the signal strength, and improve the detector response and resolution. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 This is a schematic diagram of the structure of the medium-wave infrared bandpass filter of the present invention;

[0024] Figure 2 This is the spectral transmittance curve of the germanium substrate.

[0025] Figure 3 This is the spectral transmittance curve of the main film system of the medium-wave infrared bandpass filter.

[0026] Figure 4 This is the spectral transmittance curve of the mid-wave infrared bandpass filter sub-film system.

[0027] Figure 5 It is the spectral transmittance curve of the medium-wave infrared bandpass filter. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Embodiment 1

[0030] like Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 As shown, a medium-wave infrared bandpass filter, the working band range is 4.5-5.0 μm, including a substrate 2, a main film system 1 and a secondary film system 3, the main film system is located on the first side of the substrate, the secondary film system is located on the second side of the substrate, the second side is opposite to the first side, the main film system and the secondary film system described in this embodiment are multi-layer film irregular film system structures, the main film system includes high refractive index film layers and low refractive index film layers alternately stacked from the substrate to the outside according to the main film system structure, a total of 22 layers, the main film system structure is:

[0031] substrate / 100 nmH, 981.15 nmL, 260.54 nmH, 818.82 nmL, 423.4 nmH, 538.62 nmL, 400.43 nmH, 781.62 nmL, 298.85 nmH, 694.75 nmL, 403.62 nmH, 667.75 nmL, 347.66 nmH, 731.58 nmL, 382.17 nmH, 625.62 nmL, 452.13 nmH, 674.99 nmL, 595.49 nmH, 1098.45 nmL, 286.06 nmH, 496.05 nmL / air;

[0032] The secondary film system includes high refractive index film layers and low refractive index film layers alternately stacked from the base to the outside according to the secondary film system structure, totaling 40 layers. The secondary film system structure is:

[0033] Base / 100nmH, 169.81nmL, 154.76nmH, 259.89nmL, 95.34nmH, 206.72nmL, 134.06nmH, 206.41nmL, 135.87nmH, 254.68nmL, 127.89nmH, 75.57nmL, 87.07nmH, 252.36nmL, 155.39nmH, 257.11nmL, 136.54nmH, 267.54nmL, 182.39nmH, 311.22nmL, 13 6.12 nmH, 252.39 nmL, 173.42 nmH, 344.56 nmL, 187.76 nmH, 483.27 nmL, 165.85 nmH, 380.84 nmL, 307.22 nmH, 404.6 nmL, 143.22 nmH, 511.18 nmL, 197.25 nmH, 389.52 nmL, 350.9 nmH, 211.97 nmL, 209.51 nmH, 361.78 nmL, 347.58 nmH, 595.17 nmL / air;

[0034] Among them, H represents a high refractive index film layer, L represents a low refractive index film layer, and the numbers before H and L are the thickness of the film layer. In practical applications, the substrate can be a transparent film, including but not limited to a silicon substrate, a germanium substrate, and the like.

[0035] A method for preparing a medium-wave infrared bandpass filter, used for preparing the above-mentioned medium-wave infrared bandpass filter, the method comprising the following steps:

[0036] First, the substrate is cleaned; this step first ultrasonically cleans the surface of the substrate. For example, the surface finish of the germanium substrate must meet the 40 / 20 standard. The 40 / 20 standard refers to the US military standard MIL-PRF-13830B. The finish of 40 / 20 indicates the limit level of surface defects. 40 represents the limit number of scratch size, and 20 represents the limit number of pit size.

[0037] Place the substrate in the vacuum chamber of the coating machine to heat the substrate; put the ultrasonically cleaned substrate into the coating fixture, and transfer it to a clean low vacuum chamber and evacuate it to below 5.0E-0Pa, bake and heat the substrate, and the baking temperature is set to 160°C for more than 60 minutes.

[0038] The vacuum is evacuated to below 2×10E-3Pa, and the two coating materials are pre-melted;

[0039] In practical applications, an ion source is used to assist in cleaning the substrate surface before coating; specifically, a Hall ion source can be used to bombard the surface of one side of the substrate; specifically: a Hall ion source is used to bombard the surface of one side of the substrate for 6 to 10 minutes, the power is 0.5 to 1.5 kw, the working gas is Ar gas, and the Ar gas flow rate is 10 to 100 sccm.

[0040] By physical vapor deposition, 22 layers of high refractive index film layers and low refractive index film layers with preset film thicknesses are alternately deposited on one side of the substrate to form a main film system; the film system structure of the main film system is: substrate / 100nmH, 981.15nmL, 260.54nmH, 818.82nmL, 423.4nmH, 538.62nmL, 400.43nmH, 781.62nmL, 298.85nmH, 694.75nmL mL, 403.62nmH, 667.75nmL, 347.66nmH, 731.58nmL, 382.17nmH, 625.62nmL, 452.13nmH, 674.99nmL, 595.49nmH, 1098.45nmL, 286.06nmH, 496.05nmL / air; wherein, H represents a high refractive index film layer, L represents a low refractive index film layer, and the numbers before H and L are the thickness of the film layer.

[0041] After the main film system structure is plated, the infrared filter is annealed at a temperature of 160°C, a constant temperature time of 1 hour, a cooling rate of 1-2°C / min, and then cooled to 60°C, vented, and taken out;

[0042] Clean the coated front substrate again and put it into the coating fixture, with the coated side facing up and the non-film side facing down. Put the assembled product fixture on the sample rack of the vacuum coating machine and bake it under vacuum conditions. The temperature is set to 160℃ and the constant temperature time is greater than 60min.

[0043] The vacuum is evacuated to below 2×10E-3Pa, and the two coating materials are pre-melted;

[0044] In practical applications, an ion source is used to assist in cleaning the substrate surface before coating; specifically, a Hall ion source can be used to bombard the surface of one side of the substrate; specifically: a Hall ion source is used to bombard the surface of one side of the substrate for 6 to 10 minutes, the power is 0.5 to 1.5 kw, the working gas is Ar gas, and the Ar gas flow rate is 10 to 100 sccm.

[0045] By physical vapor deposition, 40 layers of high refractive index film layers and low refractive index film layers with preset film thicknesses are alternately deposited on the other side of the substrate to form a secondary film system; the film system structure of the secondary film system is: substrate / 100nmH, 169.81nmL, 154.76nmH, 259.89nmL, 95.34nmH, 206.72nmL, 134.06nmH, 206.41nmL, 135.87nmH, 254.68nmL, 127.89nmH, 75.57nmL, 87.07nmH, 252.36nmL, 155.39nmH, 257.11nmL, 136.54nmH, 267.54nmL, 182.39 nmH, 311.22nmL, 136.12nmH, 252.39nmL, 173.42nmH, 344.56nmL, 187.76nmH, 483.27nmL, 165.85nmH, 380.84nmL, 307.22nmH, 404.6nmL, 143.22nmH, 511.18nmL, 197.25nmH, 389.52nmL, 350.9nmH, 211.97nmL, 209.51nmH, 361.78nmL, 347.58nmH, 595.17nmL / air; wherein H represents a high refractive index film layer, L represents a low refractive index film layer, and the numbers before H and L are the thickness of the film layer.

[0046] After the main film system and the secondary film system are formed, annealing is performed to complete the preparation of the medium-wave infrared bandpass filter;

[0047] During coating, a quartz crystal oscillator is used to monitor the film thickness.

[0048] The optical properties of the prepared medium-wave infrared bandpass filter were measured using an infrared Fourier spectrometer. The spectral curve corresponding to the main film system on the front side can be found in Figure 3 , the spectral curve corresponding to the back secondary film system can be found in Figure 4 , the spectral curve of the filter after double-sided coating can be found in Figure 5 , achieving an average transmittance greater than 92% in the wavelength range of 4.5 to 5.0 μm; and an average transmittance less than 1% in the wavelength ranges of 1 to 4.2 μm and 5.3 to 7.5 μm.

[0049] A main film system is formed by coating 22 layers of high refractive index film layers and low refractive index film layers in an alternating manner on one side of a substrate by means of physical vapor deposition, and a secondary film system is formed by coating 40 layers of high refractive index film layers and low refractive index film layers in an alternating manner on the other side of the substrate by means of physical vapor deposition, so as to prepare a medium-wave infrared bandpass filter; the prepared medium-wave infrared bandpass filter has a bandpass spectral range of 4.5 to 5.0 μm and an average transmittance of more than 92%; a cutoff spectral range of 1 to 4.2 μm and 5.3 to 7.5 μm, and an average transmittance of less than 1%, which can well improve the signal-to-noise ratio, enhance the signal strength, and improve the detector response rate; and can be used in various infrared optical detection systems to reduce the influence of background clutter, enhance the signal strength, and improve the detector response and resolution.

[0050] Embodiment 2

[0051] like Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 As shown, a medium-wave infrared bandpass filter, with an operating band range of 4.5 to 5.0 μm, includes a germanium substrate, a main film system 1 and a secondary film system 3, wherein the main film system and the secondary film system are generated by a physical vapor deposition method, wherein the main film system is located on a first side of the germanium substrate, and the secondary film system is located on a second side of the germanium substrate, wherein the second side is opposite to the first side, and wherein the main film system includes germanium film layers and zinc sulfide film layers alternately stacked from the germanium substrate outward according to the main film system structure, totaling 22 layers, and the main film system structure is:

[0052] Germanium substrate / 100nmH, 981.15nmL, 260.54nmH, 818.82nmL, 423.4nmH, 538.62nmL, 400.43nmH, 781.62nmL, 298.85nmH, 694.75nmL, 403.62nmH, 667.75nmL, 347.66nmH, 731.58nmL, 382.17nmH, 625.62nmL, 452.13nmH, 674.99nmL, 595.49nmH, 1098.45nmL, 286.06nmH, 496.05nmL / air;

[0053] The sub-film system includes germanium film layers and zinc sulfide film layers alternately stacked from the germanium substrate outward according to the sub-film system structure, a total of 40 layers, and the sub-film system structure is:

[0054] Germanium substrate / 100nmH, 169.81nmL, 154.76nmH, 259.89nmL, 95.34nmH, 206.72nmL, 134.06nmH, 206.41nmL, 135.87nmH, 254.68nmL, 127.89nmH, 75.57nmL, 87.07nmH, 252.36nmL, 155.39nmH, 257.11nmL, 136.54nmH, 267.54nmL, 182.39nmH, 311.22nmL, 1 36.12 nmH, 252.39 nmL, 173.42 nmH, 344.56 nmL, 187.76 nmH, 483.27 nmL, 165.85 nmH, 380.84 nmL, 307.22 nmH, 404.6 nmL, 143.22 nmH, 511.18 nmL, 197.25 nmH, 389.52 nmL, 350.9 nmH, 211.97 nmL, 209.51 nmH, 361.78 nmL, 347.58 nmH, 595.17 nmL / air;

[0055] Among them, H represents the germanium film layer, L represents the zinc sulfide film layer, and the numbers before H and L are the thickness of the film layer.

[0056] A method for preparing a medium-wave infrared bandpass filter, used for preparing the above-mentioned medium-wave infrared bandpass filter, the method comprising the following steps:

[0057] First, the germanium substrate is cleaned; this step first performs ultrasonic cleaning on the surface of the germanium substrate. For example, the surface finish of the germanium substrate must meet the 40 / 20 standard. The 40 / 20 standard refers to the U.S. military standard MIL-PRF-13830B. The finish of 40 / 20 indicates the limit level of surface defects, 40 represents the limit number of scratch size, and 20 represents the limit number of pit size.

[0058] The germanium substrate is placed in the vacuum chamber of the coating machine to heat the germanium substrate; the ultrasonically cleaned germanium substrate is placed in a coating fixture, and transferred into a clean low vacuum chamber and evacuated to below 5.0E-0Pa, and the germanium substrate is baked and heated, the baking temperature is set to 160°C, and the constant temperature time is greater than 60 minutes.

[0059] The vacuum is evacuated to below 2×10E-3Pa, and the two coating materials are pre-melted;

[0060] In practical applications, an ion source is used to assist in cleaning the surface of the germanium substrate before coating; specifically, a Hall ion source can be used to bombard the surface of one side of the germanium substrate; specifically: the Hall ion source is used to bombard the surface of one side of the germanium substrate for 6 to 10 minutes, the power is 0.5 to 1.5 kw, the working gas is Ar gas, and the Ar gas flow rate is 10 to 100 sccm.

[0061] By physical vapor deposition, 22 layers of germanium film layers and zinc sulfide film layers with preset film thicknesses are alternately deposited on one side of a germanium substrate to form a main film system; the film system structure of the main film system is: germanium substrate / 100nmH, 981.15nmL, 260.54nmH, 818.82nmL, 423.4nmH, 538.62nmL, 400.43nmH, 781.62nmL, 298.85nmH, 694.75 nmL, 403.62nmH, 667.75nmL, 347.66nmH, 731.58nmL, 382.17nmH, 625.62nmL, 452.13nmH, 674.99nmL, 595.49nmH, 1098.45nmL, 286.06nmH, 496.05nmL / air; wherein H represents the germanium film layer, L represents the zinc sulfide film layer, and the numbers before H and L are the thickness of the film layer. The germanium material used in the germanium film layer is evaporated by electron gun evaporation; the zinc sulfide material used in the zinc sulfide film layer is evaporated by resistance boat thermal evaporation. The evaporation rate of the germanium material is controlled within 10A / s; the evaporation rate of the zinc sulfide material is controlled within 10A / s.

[0062] After the main film system structure is plated, the infrared filter is annealed at a temperature of 160°C, a constant temperature time of 1 hour, a cooling rate of 1-2°C / min, and then cooled to 60°C, vented, and taken out;

[0063] Clean the germanium substrate with the coated front side again and put it into the coating fixture, with the coated side facing up and the non-film side facing down. Put the assembled product fixture on the sample rack of the vacuum coating machine and bake it under vacuum conditions. The temperature is set to 160℃ and the constant temperature time is greater than 60min.

[0064] The vacuum is evacuated to below 2×10E-3Pa, and the two coating materials are pre-melted;

[0065] In practical applications, an ion source is used to assist in cleaning the surface of the germanium substrate before coating; specifically, a Hall ion source can be used to bombard the surface of one side of the germanium substrate; specifically: the Hall ion source is used to bombard the surface of one side of the germanium substrate for 6 to 10 minutes, the power is 0.5 to 1.5 kw, the working gas is Ar gas, and the Ar gas flow rate is 10 to 100 sccm.

[0066] 40 layers of germanium film layers and zinc sulfide film layers with preset film thicknesses are alternately deposited on the other side of the germanium substrate by a physical vapor deposition method to form a secondary film system; the film system structure of the secondary film system is: germanium substrate / 100nmH, 169.81nmL, 154.76nmH, 259.89nmL, 95.34nmH, 206.72nmL, 134.06nmH, 206.41nmL, 135.87nmH, 254.68nmL, 127.89nmH, 75.57nmL, 87.07nmH, 252.36nmL, 155.39nmH, 257.11nmL, 136.54nmH, 267.54nmL, 182.3 9nmH, 311.22nmL, 136.12nmH, 252.39nmL, 173.42nmH, 344.56nmL, 187.76nmH, 483.27nmL, 165.85nmH, 380.84nmL, 307.22nmH, 404.6nmL, 143.22nmH, 511.18nmL, 197.25nmH, 389.52nmL, 350.9nmH, 211.97nmL, 209.51nmH, 361.78nmL, 347.58nmH, 595.17nmL / air; wherein H represents germanium film layer, L represents zinc sulfide film layer, and the numbers before H and L are the thickness of the film layer. The germanium material used in the germanium film layer is evaporated by electron gun evaporation; the zinc sulfide material used in the zinc sulfide film layer is evaporated by resistance boat thermal evaporation. The evaporation rate of the germanium material is controlled within 10A / s; the evaporation rate of the zinc sulfide material is controlled within 10A / s.

[0067] After the main film system and the secondary film system are formed, annealing is performed to complete the preparation of the medium-wave infrared bandpass filter;

[0068] During coating, a quartz crystal oscillator is used to monitor the film thickness.

[0069] The optical properties of the prepared medium-wave infrared bandpass filter were measured using an infrared Fourier spectrometer. The spectral curve corresponding to the main film system on the front side can be found in Figure 3 , the spectral curve corresponding to the back secondary film system can be found in Figure 4 , the spectral curve of the filter after double-sided coating can be found in Figure 5 , achieving an average transmittance greater than 92% in the wavelength range of 4.5 to 5.0 μm; and an average transmittance less than 1% in the wavelength ranges of 1 to 4.2 μm and 5.3 to 7.5 μm.

[0070] A main film system is formed by coating 22 layers of germanium film layers and zinc sulfide film layers in an alternating manner on one side of a germanium substrate by physical vapor deposition, and a secondary film system is formed by coating 40 layers of germanium film layers and zinc sulfide film layers in an alternating manner on the other side of the germanium substrate by physical vapor deposition, so as to prepare a medium-wave infrared bandpass filter; the prepared medium-wave infrared bandpass filter has a bandpass spectral range of 4.5 to 5.0 μm and an average transmittance of more than 92%; a cutoff spectral range of 1 to 4.2 μm and 5.3 to 7.5 μm, and an average transmittance of less than 1%, which can well improve the signal-to-noise ratio, enhance the signal strength, and improve the detector response rate; and can be used in various infrared optical detection systems to reduce the influence of background clutter, enhance the signal strength, and improve the detector response and resolution.

[0071] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the art within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A method for preparing a medium-wave infrared bandpass filter, characterized in that: The method comprises the following steps: Placing the substrate into a vacuum chamber of a coating machine to heat the substrate; Evacuate to below 2×10E-3Pa; By means of physical vapor deposition, 22 layers of high-refractive-index film layers and low-refractive-index film layers with preset film thicknesses are alternately deposited outward on one side of the substrate to form a main film system; By physical vapor deposition, 40 layers of high-refractive-index film layers and low-refractive-index film layers with preset film thicknesses are alternately deposited outward on the other side of the substrate to form a secondary film system; After the main film system and the secondary film system are formed, annealing is performed to complete the preparation of the medium-wave infrared bandpass filter; The medium-wave infrared bandpass filter has a light-transmitting effect in the wavelength range of 4.5 to 5.0 μm, with an average transmittance of more than 92%, and is highly cut off in the wavelength ranges of 1 to 4.2 μm and 5.3 to 7.5 μm, with an average transmittance of less than 1%.

2. The method for preparing a medium-wave infrared bandpass filter according to claim 1, characterized in that: The film system structure of the main film system is: substrate / 100nmH, 981.15nmL, 260.54nmH, 818.82nmL, 423.4nmH, 538.62nmL, 400.43nmH, 781.62nmL, 298.85nmH, 694.75nmL, 403.62nmH, 667.75nmL, 347.66nmH, 731.58nmL, 382.17nmH, 625.62nmL, 452.13nmH, 674.99nmL, 595.49nmH, 1098.45nmL, 286.06nmH, 496.05nmL / air; wherein H represents a high refractive index film layer, L represents a low refractive index film layer, and the numbers before H and L are the thickness of the film layer.

3. The method for preparing a medium-wave infrared bandpass filter according to claim 1, characterized in that: The membrane structure of the secondary membrane system is: substrate / 100nmH, 169.81nmL, 154.76nmH, 259.89nmL, 95.34nmH, 206.72nmL, 134.06nmH, 206.41nmL, 135.87nmH, 254.68nmL, 127.89nmH, 75.57nmL, 87.07nmH, 252.36nmL, 155.39nmH, 257.11nmL, 136.54nmH, 267.54nmL, 182.39nmH, 311.22nmL, 136.12nmH, 252. 39nmL, 173.42nmH, 344.56nmL, 187.76nmH, 483.27nmL, 165.85nmH, 380.84nmL, 307.22nmH, 404.6nmL, 143.22nmH, 511.18nmL, 197.25nmH, 389.52nmL, 350.9nmH, 211.97nmL, 209.51nmH, 361.78nmL, 347.58nmH, 595.17nmL / air; wherein H represents a high refractive index film layer, L represents a low refractive index film layer, and the numbers before H and L are the thickness of the film layer.

4. The method for preparing a medium-wave infrared bandpass filter according to claim 1, characterized in that: The substrate is a germanium substrate.

5. The method for preparing a medium-wave infrared bandpass filter according to claim 1, characterized in that: The high refractive index film layer is a germanium film layer, and the low refractive index film layer is a zinc sulfide film layer.

6. The method for preparing a medium-wave infrared bandpass filter according to claim 5, characterized in that: The germanium material used in the germanium film layer is evaporated by electron gun evaporation; the zinc sulfide material used in the zinc sulfide film layer is evaporated by resistance boat thermal evaporation.

7. The method for preparing a medium-wave infrared bandpass filter according to claim 6, characterized in that: The evaporation rate of the germanium material is controlled within 10A / s; the evaporation rate of the zinc sulfide material is controlled within 10A / s.

8. The method for preparing a medium-wave infrared bandpass filter according to any one of claims 1 to 7, characterized in that: Placing the substrate in a vacuum chamber of a coating machine to heat the substrate includes: placing the substrate in a vacuum chamber of a coating machine to bake and heat the substrate, and the baking temperature is set to 160°C.

9. The method for preparing a medium-wave infrared bandpass filter according to claim 8, characterized in that: The method further comprises: using an ion source to assist in cleaning the surface of the substrate before coating.

10. The method for preparing a medium-wave infrared bandpass filter according to claim 8, characterized in that: The method further comprises: during film coating, using a quartz crystal oscillator to monitor film thickness.

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