A high cut-off depth filter and its preparation method and application

Abstract

The invention discloses a high cut-off depth filter and a preparation method and application thereof, and relates to the technical field of filters. The high cut-off depth filter comprises, from top to bottom, a narrow-band filter film, a substrate and a high-isolation cut-off film. The high cut-off depth filter has a high transmittance to the pass band, and the peak transmittance is greater than 95%; the cut-off rate of the cut-off band is deep, and the transmittance is less than 2%, which can effectively filter out stray light; the half-bandwidth of the pass band is narrow, the angle effect is small, the isolation is high, the light output power is high, the power attenuation is less than 5%, and the anti-laser damage threshold is high.

Description

Technical Field

[0001] The present invention relates to the technical field of optical filters, and in particular to an optical filter with a high cut-off depth, and a preparation method and application thereof. Background Art

[0002] Optical filters are optical components used to change the spectral intensity distribution or polarization characteristics of incident light. Filters play an important role in many fields such as photographic equipment, spectral instruments, fiber optic communications, optical sensors, space remote sensing, laser systems, optoelectronic displays, etc. Optical thin film filters refer to optical components that use multi-layer thin films with a film thickness equivalent to the wavelength to allow light within a specific spectral range to pass through while filtering out unnecessary wavelengths. According to the different suppression and transmission wavelength ranges, they can be divided into bandpass filters, long-wavepass filters, short-wavepass filters, etc.

[0003] The transmittance of the existing filters used in biomedical detection instruments is low (about 80%) in the light band, which affects the clarity of the image; the cutoff depth of the cutoff band is not enough, the transmittance is about 0.1%, and the stray light cannot be effectively filtered out, which in turn interferes with CCD / CMOS imaging; the half-bandwidth of the light band is too wide, about 20nm, and more stray light will pass through, which in turn affects the resolution and color reproduction of the image; the angle effect is large, and the wavelength shift is serious at 0° to 30°, about 30nm; the isolation is low, the light output power is seriously attenuated, and the power attenuation is more than 20%; the ability to resist laser damage is low, and the filter film layer is 2J / cm 2 It is easy to burn after laser energy irradiation and has a short service life.

[0004] Therefore, it is necessary to provide a filter with high transmittance, high cut-off depth, small angle effect, and high laser damage resistance threshold. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a high cut-off depth filter, which has high transmittance, high cut-off depth, small angle effect, and high resistance to laser damage.

[0006] The present invention also provides a method for preparing the high cut-off depth filter.

[0007] The present invention also provides application of the high cut-off depth filter.

[0008] The term "narrow-band filter" refers to a single-wavelength filter that cuts off light in other wavelengths and only passes light of a specific wavelength.

[0009] The term "high isolation cut-off film" refers to a filter film that can efficiently block and filter light in the cut-off band.

[0010] The high cut-off depth filter according to the first aspect of the present invention comprises, from top to bottom:

[0011] Narrow band filter films, substrates and high isolation cut-off films;

[0012] The narrow band filter film comprises a first SiO 2 Film layer and first Ta 2 O 5 The film layers are alternately stacked on one side of the substrate, wherein the number of alternations is 22 to 26 times; the first SiO2 film directly attached to the substrate 2 The optical thickness of the film layer is 0.5A to 0.6A, and the rest of the first SiO 2 The optical thickness of the film layer is 1A to 6A; the first Ta closest to the substrate 2 O 5 The thickness of the film layer is 0.7A-0.8A, and the rest of the first Ta 2 O 5 The optical thickness of the film layer is 1A to 3A;

[0013] The high isolation cut-off film includes a second Ta layer formed on the other side surface of the substrate 2 O 5 Film layer and second SiO 2 The film layer, wherein: the number of alternations is 160 to 164 times; the second Ta layer directly attached to the substrate 2 O 5 The optical thickness of the film layer is 0.2A~0.3A, and the rest of the second Ta 2 O 5 The optical thickness of the film layer is 0.4A to 1.2A; the second SiO 2 The thickness of the film layer is 0.5A~1.2A;

[0014] Wherein, A represents 1 / 4 design wavelength.

[0015] "Alternation times" refers to: the first SiO 2 Film layer and first Ta 2 O 5 Film layer (or second Ta 2 O 5 Film layer and second SiO 2 The number of alternations is 1 when the film layers are alternately stacked once.

[0016] The high cut-off depth filter according to the embodiment of the present invention has at least the following beneficial effects:

[0017] The high cut-off depth filter of the embodiment has high transmittance for the light-passing band, the transmittance is greater than 95%, and the imaging clarity is high; the cut-off band has a deep cut-off rate, the transmittance is less than 0.001%, and the stray light can be effectively filtered out, and the CCD / CMOS imaging is not interfered by the stray light; the half-bandwidth of the light-passing band is narrow, the bandwidth is 8nm to 10nm, and the specific wavelength can be effectively passed, the imaging resolution is high, and the color reproduction is good; the angle effect is small, and the wavelength deviation is less than 15nm when 0° to 30°; the isolation is high, the light output power is high, and the power attenuation is less than 5%; the anti-laser damage threshold is high, greater than 5J / cm 2 The above laser energy irradiation does not damage or destroy the film layer, and the service life of the film layer reaches more than 3 years. The high cut-off depth filter of the embodiment has stable and reliable performance and strong practicality, and can be widely used in biomedical detection instruments, laser radars, etc.

[0018] According to some embodiments of the present invention, the structure of the narrow band filter film is: Air / HLHL H2LHLHLHLHL3HL H4LH 3LHLHL HL3HL H6LH 3LHLHLHLHL H2LH LHL0.7806H0.5284L / Sub;

[0019] The structure of the high isolation cut-off film is: Sub / 0.52(0.5HL0.5H)^20, 0.65(0.5HL0.5H)^20, 0.8(0.5HL0.5H)^20, 1.15(0.5LH0.5L)^20 / Air;

[0020] Where Air represents air; Sub represents substrate; H represents the optical thickness of Ta which is 1 / 4 of the design wavelength thickness. 2 O 5 Film layer; L represents the optical thickness of SiO2 with a thickness of 1 / 4 the design wavelength. 2 Film layer; the number before H or L is the optical thickness proportional coefficient of the corresponding film layer, and ^20 indicates the number of repetitions of the film layer structure in brackets.

[0021] According to some embodiments of the present invention, the design wavelength is 905 nm and the light transmission range is 905±10 nm.

[0022] According to some embodiments of the present invention, the peak transmittance of the high cut-off depth filter is greater than 95%.

[0023] According to some embodiments of the present invention, the half bandwidth of the high cut-off depth filter does not exceed 10 nm.

[0024] According to some embodiments of the present invention, the transmittance of the high cut-off depth filter in the cut-off regions of 400 nm to 895 nm and 915 nm to 1100 nm is less than 2%.

[0025] According to some embodiments of the present invention, the transmittance of the high cut-off depth filter in the cut-off regions of 400 nm to 894 nm and 916 nm to 1100 nm is less than 1%.

[0026] According to some embodiments of the present invention, the transmittance of the high cut-off depth filter in the cut-off regions of 400 nm to 890 nm and 921 nm to 1100 nm is less than 0.1%.

[0027] According to some embodiments of the present invention, the transmittance of the high cut-off depth filter in the cut-off regions of 400 nm to 875 nm and 939 nm to 1100 nm is less than 0.001%.

[0028] According to some embodiments of the present invention, the substrate comprises optical glass.

[0029] According to some embodiments of the present invention, the thickness of the substrate is 1 mm to 3 mm.

[0030] According to some embodiments of the present invention, the thickness of the substrate is 1 mm.

[0031] According to some embodiments of the present invention, the thickness of the narrow-band filter film is 9 μm to 15 μm.

[0032] According to some embodiments of the present invention, the thickness of the narrow-band filter film is 9 μm to 11 μm.

[0033] According to some embodiments of the present invention, the thickness of the narrow-band filter film is 10 μm.

[0034] According to some embodiments of the present invention, the high isolation cut-off film has a thickness of 15 μm to 20 μm.

[0035] According to some embodiments of the present invention, the high isolation cut-off film has a thickness of 15 μm to 17 μm.

[0036] According to some embodiments of the present invention, the transmittance of the high cut-off depth filter to light outside the design wavelength ±10 nm is less than 2%.

[0037] According to some embodiments of the present invention, the half bandwidth of the high cut-off depth filter is 8 nm to 15 nm.

[0038] According to some embodiments of the present invention, the half bandwidth of the high cut-off depth filter is 8 nm to 12 nm.

[0039] According to some embodiments of the present invention, when the high cut-off depth filter is in the range of 0° to 30°, the wavelength shift is less than 15 nm.

[0040] The preparation method according to the second aspect of the present invention comprises the following steps: using electron beam evaporation and ion source assisted deposition to alternately plate a first SiO 2 Film layer and first Ta 2 O 5 The narrow-band filter film is obtained by alternately coating the second Ta on the other side of the substrate. 2 O 5 Film layer, second SiO 2 The film layer is used to obtain the high isolation cut-off film. The RF ion source is used to assist the film layer filling density of the high cut-off depth filter to be high, the film layer is firm, and the temperature drift effect is small.

[0041] According to some embodiments of the present invention, in the plating conditions, the working temperature is 180° C. to 200° C. If the working temperature is not within this range, the filling density of the material will be reduced, the adhesion of the film layer will be reduced, and the hardness of the film layer will be reduced.

[0042] According to some embodiments of the present invention, in the plating condition, the working temperature is 200°C.

[0043] According to some embodiments of the present invention, in the plating conditions, the working pressure is 7.0×10 -4 Pa~9.0×10 -4 Pa. As a result, there are fewer impurities and residual gases in the environment, which is beneficial to improving the surface smoothness and film density of high cut-off depth filters.

[0044] According to some embodiments of the present invention, in the plating conditions, the working pressure is 8.0×10 -4 Pa.

[0045] According to some embodiments of the present invention, in the plating conditions, the working gas is oxygen.

[0046] According to some embodiments of the present invention, in the plating conditions, the gas flow rate is 55 sccm to 75 sccm. If the gas flow rate is not within this range, the material molecules will lose oxygen, causing film absorption, resulting in reduced transmittance of the high cut-off depth filter.

[0047] According to some embodiments of the present invention, in the plating condition, the gas flow rate is 65 sccm.

[0048] According to some embodiments of the present invention, in the plating conditions, the Ta 2 O 5 Evaporation rate: 0.20nm / sec ~ 0.30nm / sec. If the evaporation rate is not within this range, it will cause material splashing, resulting in poor surface finish of the high cut-off depth filter and pitting on the surface.

[0049] According to some embodiments of the present invention, in the plating conditions, the Ta 2 O 5 Evaporation rate: 0.25 nm / sec.

[0050] According to some embodiments of the present invention, in the plating conditions, the SiO 2 Evaporation rate: 0.6nm / sec~1nm / sec. If the evaporation rate is not within this range, it will cause material splashing, resulting in poor surface finish of the high cut-off depth filter and pitting on the surface.

[0051] According to some embodiments of the present invention, in the plating conditions, the SiO 2 Evaporation rate: 0.8 nm / sec.

[0052] The application of the third aspect of the present invention is specifically the application of the high cut-off depth filter of the first aspect in biomedical detection instruments, optical instruments, laser radar or optical detection. Since all the technical solutions of the high cut-off depth filter of the above embodiment are adopted, at least all the beneficial effects brought by the technical solutions of the above embodiment are obtained.

[0053] According to some embodiments of the present invention, the biomedical detection instrument includes a blood oximeter.

[0054] According to some embodiments of the invention, the optical instrument comprises an infrared detector.

[0055] According to some embodiments of the present invention, the application of the high cut-off depth filter in a laser radar specifically includes an application in a laser radar sensor.

[0056] According to some embodiments of the present invention, the application of the high cut-off depth filter in optical detection specifically includes application in vehicle-mounted laser radar, robots, and drones.

[0057] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0059] Figure 1 is a schematic structural diagram of a high cut-off depth filter according to an embodiment of the present invention;

[0060] Figure 2 is a transmittance spectrum diagram of a high cut-off depth filter according to an embodiment of the present invention;

[0061] Figure 3 is a partial enlarged view of the transmittance spectrum of the high cut-off depth filter of the embodiment of the present invention;

[0062] Figure 4 It is a comparison diagram of the transmittance spectra of the high cut-off depth filter of the embodiment of the present invention at 0° and 30°.

[0063] Reference numerals:

[0064] Substrate 101, narrow-band filter film 102, high-isolation cut-off film 103. DETAILED DESCRIPTION

[0065] The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0066] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0067] In the description of the present invention, "a plurality" means more than two. If there is a description of "first" or "second", it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0068] In the description of the present invention, it should be understood that descriptions involving orientation, such as orientation or positional relationship indicated as up, down, etc., are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0069] Example 1

[0070] This embodiment provides a high cut-off depth filter, which includes, from top to bottom, a narrow-band filter film 102, a substrate 101, and a high-isolation cut-off film 103. Figure 1 The details are as follows:

[0071] The substrate 101 is optical glass with a thickness of 1.0 mm;

[0072] The structure of the narrow band filter film 102 is: Air / HLHL H2LH LHLHLHL3HL H4LH 3LHLHL HL3HLH6LH3LHLHLHLHL H2LH LHL0.7806H0.5284L / Sub, a total of 48 layers, with a thickness of 10 μm;

[0073] The structure of the high isolation cut-off film 103 is: Sub / 0.52(0.5HL0.5H)^20, 0.65(0.5HL0.5H)^20, 0.8(0.5HL0.5H)^20, 1.15(0.5LH0.5L)^20 / Air, a total of 162 layers, with a thickness of 16μm;

[0074] Air represents air; Sub represents substrate; H represents tantalum pentoxide (Ta) with a thickness of 1 / 4 the design wavelength. 2 O 5 ) film layer; L represents the silicon dioxide (SiO 2 ) film layer; the number before H or L is the optical thickness proportional coefficient of the corresponding film layer, and ^20 represents the number of repetitions of the film layer structure in brackets.

[0075] In the structure of the high isolation cut-off film 103, two adjacent layers of Ta 2 O 5 The film layer can be regarded as a layer of Ta 2 O 5 The film layer is for convenience. 2 The same applies to the membrane layer.

[0076] The design wavelength of the high cut-off depth filter is 905nm.

[0077] The specific thickness design is shown in Table 1 and Table 2.

[0078] Table 1. Narrowband filter film structure

[0079] layer number material optical thickness physical thickness(nm) layer number material optical thickness physical thickness(nm) 1 <![CDATA[Ta 2 THE 5 ]]> 1 / 4 min 108.61 25 <![CDATA[Ta 2 THE 5 ]]> 1 / 4 min 108.61 2 <![CDATA[SiO 2 ]]> 1 / 4 min 155.17 26 <![CDATA[SiO 2 ]]> 1 / 4 min 155.17 3 <![CDATA[Ta 2 THE 5 ]]> 1 / 4 min 108.61 27 <![CDATA[Ta 2 THE 5 ]]> 3 / 4 min 325.82 4 <![CDATA[SiO 2 ]]> 1 / 4 min 155.17 28 <![CDATA[SiO 2 ]]> 1 / 4 min 155.17 5 <![CDATA[Ta 2 THE 5 ]]> 1 / 4 min 108.61 29 <![CDATA[Ta 2 THE 5 ]]> 1 / 4 min 108.61 6 <![CDATA[SiO 2 ]]> 1 / 2 minute 310.34 30 <![CDATA[SiO 2 ]]> 1.5l 931.02 7 <![CDATA[Ta 2 THE 5 ]]> 1 / 4 min 108.61 31 <![CDATA[Ta 2 THE 5 ]]> 1 / 4 min 108.61 8 <![CDATA[SiO 2 ]]> 1 / 4 min 155.17 32 <![CDATA[SiO 2 ]]> 3 / 4 min 465.51 9 <![CDATA[Ta 2 THE 5 ]]> 1 / 4 min 108.61 33 <![CDATA[Ta 2 THE 5 ]]> 1 / 4 min 108.61 10 <![CDATA[SiO 2 ]]> 1 / 4 min 155.17 34 <![CDATA[SiO 2 ]]> 1 / 4 min 155.17 11 <![CDATA[Ta 2 THE 5 ]]> 1 / 4 min 108.61 35 <![CDATA[Ta 2 THE 5 ]]> 1 / 4 min 108.61 12 <![CDATA[SiO 2 ]]> 1 / 4 min 155.17 36 <![CDATA[SiO 2 ]]> 1 / 4 min 155.17 13 <![CDATA[Ta 2 THE 5 ]]> 1 / 4 min 108.61 37 <![CDATA[Ta 2 THE 5 ]]> 1 / 4 min 108.61 14 <![CDATA[SiO 2 ]]> 1 / 4 min 155.17 38 <![CDATA[SiO 2 ]]> 1 / 4 min 155.17 15 <![CDATA[Ta 2 THE 5 ]]> 3 / 4 min 325.82 39 <![CDATA[Ta 2 THE 5 ]]> 1 / 4 min 108.61 16 <![CDATA[SiO 2 ]]> 1 / 4 min 155.17 40 <![CDATA[SiO 2 ]]> 1 / 4 min 155.17 17 <![CDATA[Ta 2 THE 5 ]]> 1 / 4 min 108.61 41 <![CDATA[Ta 2 THE 5 ]]> 1 / 4 min 108.61 18 <![CDATA[SiO 2 ]]> l 620.68 42 <![CDATA[SiO 2 ]]> 1 / 2 minute 310.34 19 <![CDATA[Ta 2 THE 5 ]]> 1 / 4 min 108.61 43 <![CDATA[Ta 2 THE 5 ]]> 1 / 4 min 108.61 20 <![CDATA[SiO 2 ]]> 3 / 4 min 465.51 44 <![CDATA[SiO 2 ]]> 1 / 4 min 155.17 21 <![CDATA[Ta 2 THE 5 ]]> 1 / 4 min 108.61 45 <![CDATA[Ta 2 THE 5 ]]> 1 / 4 min 108.61 22 <![CDATA[SiO 2 ]]> 1 / 4 min 155.17 46 <![CDATA[SiO 2 ]]> 1 / 4 min 155.17 23 <![CDATA[Ta 2 THE 5 ]]> 1 / 4 min 108.61 47 <![CDATA[Ta 2 THE 5 ]]> 0.195l 84.78 24 <![CDATA[SiO 2 ]]> 1 / 4 min 155.17 48 <![CDATA[SiO 2 ]]> 0.132l 81.99

[0080] Table 2. High isolation cut-off membrane structure

[0081]

[0082]

[0083]

[0084]

[0085] Note: λ refers to the design wavelength. The error of optical thickness is ±0.1λ, and the error of physical thickness is ±500nm.

[0086] The method for preparing the high cut-off depth filter comprises the following steps:

[0087] Optical coating equipment is used to assist the coating with a high-energy RF (radio frequency) ion source. The working temperature is 200°C, the working gas is oxygen, the gas flow rate is 65sccm, and the working pressure is 8.0×10 -4 Pa, the tantalum pentoxide material and the silicon dioxide material are melted by the heat energy of the electron beam, and the two materials are evaporated alternately, and a narrow-band filter film and a high-isolation cut-off film are respectively plated on both sides of the optical glass according to the physical thicknesses shown in Tables 1 and 2.

[0088] Among them, the evaporation rate of tantalum pentoxide is 0.25nm / second; the evaporation rate of silicon dioxide is 0.8nm / second.

[0089] Test example

[0090] 1. Detect the transmittance spectrum of the high cut-off depth filter of Example 1. Figure 1 and 2 The transmittance data within the wavelength range of 870nm to 950nm is shown in Table 3.

[0091] Table 3. Transmittance of the high cut-off depth filter of Example 1 at 876nm to 935nm

[0092]

[0093]

[0094] The design wavelength is 905nm, and the transmittance of the high cut-off depth filter of Example 1 within the wavelength range of 900nm to 910nm is greater than 50%, the peak transmittance is greater than 95%, the transmittance of the light outside the wavelength range of 896nm to 914nm is less than 2%, and the transmittance of the light outside the wavelength range of 876nm to 938nm is less than 0.001%. After the light passes through the high cut-off depth filter of Example 1, most of the stray light is filtered out.

[0095] 2. Detect the transmittance spectra of the high cut-off depth filter of Example 1 at incident angles of 0° and 30°. At 0°, the transmittance of the high cut-off depth filter of Example 1 within the wavelength range of 900nm to 910nm is greater than 50%; at 30°, the transmittance of the high cut-off depth filter of Example 1 within the wavelength range of 887nm to 897nm is greater than 50%. Figure 3 shown.

[0096] When the high cut-off depth filter of Example 1 is within the range of 0° to 30°, the wavelength shift is less than 15 nm.

[0097] 3. The high cut-off depth filter of Example 1 was treated with laser energy (pulsed laser, pulse bandwidth 20ns, power 5J / cm 2 ) After irradiation for 60 minutes, the film layer was not damaged or destroyed.

[0098] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. A high cut-off depth filter, It is characterized in that From top to bottom they include: Narrow band filter films, substrates and high isolation cut-off films; The narrow band filter film comprises a first SiO 2 Film layer and first Ta 2 O 5 The film layers are alternately stacked on one side of the substrate, wherein the number of alternations is 22 to 26 times; the first SiO2 film directly attached to the substrate 2 The optical thickness of the film layer is 0.5A~0.6A, and the rest of the first SiO 2 The optical thickness of the film layer is 1A~6A; the first Ta closest to the substrate 2 O 5 The thickness of the film layer is 0.7A-0.8A, and the rest of the first Ta 2 O 5 The optical thickness of the film layer is 1A~3A; The high isolation cut-off film includes a second Ta layer formed on the other side surface of the substrate 2 O 5 Film layer and second SiO 2 The film layer, wherein: the number of alternations is 81 times; the second Ta layer directly attached to the substrate 2 O 5 The optical thickness of the film layer is 0.2A~0.3A, and the rest of the second Ta 2 O 5 The optical thickness of the film layer is 0.4A~1.2A; the second SiO 2 The thickness of the film layer is 0.5A~1.2A; Wherein, A represents 1 / 4 design wavelength.

2. The high cut-off depth filter according to claim 1, It is characterized in that The structure of the high isolation cut-off film is: Sub / 0.52(0.5HL0.5H)^20, 0.65(0.5HL0.5H)^20, 0.8(0.5HL0.5H)^20, 1.15(0.5LH0.5L)^20 / Air; Where Air represents air; Sub represents substrate; H represents the optical thickness of Ta which is 1 / 4 of the design wavelength thickness. 2 O 5 Film layer; L represents the optical thickness of SiO2 with a thickness of 1 / 4 the design wavelength. 2 Film layer; the number before H or L is the optical thickness ratio coefficient of the corresponding film layer, and ^20 indicates the number of repetitions of the film layer structure in brackets; The structure of the narrow-band filter film is: Air / HLHL H2LH LHLHLHL3HL H4LH 3LHLHL HL3HL H6LH3LHLHLHLHL H2LH LHL0.7806H0.5284L / Sub.

3. The high cut-off depth filter according to claim 1, It is characterized in that The substrate comprises optical glass; the thickness of the substrate is 1 mm to 3 mm.

4. The high cut-off depth filter according to claim 1, It is characterized in that The thickness of the narrow-band filter film is 9 μm to 15 μm.

5. The high cut-off depth filter according to claim 1, It is characterized in that The thickness of the high isolation cut-off film is 15 μm-20 μm.

6. The high cut-off depth filter according to claim 1, It is characterized in that The design wavelength is 905 nm; the peak transmittance of the high cut-off depth filter is greater than 95%.

7. The high cut-off depth filter according to claim 1 or 6, It is characterized in that The half bandwidth of the high cut-off depth filter is 8 nm to 15 nm.

8. The high cut-off depth filter according to claim 1, It is characterized in that When the incident angle of the high cut-off depth filter is within the range of 0° to 30°, the wavelength shift is less than 15 nm.

9. A method for preparing a high cut-off depth filter according to any one of claims 1 to 8, It is characterized in that The following steps are involved: The first SiO2 is alternately plated on one side of the substrate by electron beam evaporation and ion source assisted deposition. 2 Film layer and first Ta 2 O 5 film layer to obtain the narrow-band filter film; The second Ta is alternately plated on the other side surface of the substrate 2 O 5 Film layer, second SiO 2 The high isolation cut-off film is obtained.

10. Use of the high cut-off depth filter according to any one of claims 1 to 8 in biomedical detection instruments or optical instruments.

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