Optical filter and manufacturing method and application thereof

Abstract

The invention belongs to the field of optical films. The invention provides an optical filter and a manufacturing method and application thereof, the optical filter is sequentially provided with an anti-back-reflection film stack, a high-transmittance film stack and an anti-reflection film stack which are formed according to different stacking structures on a substrate, and the three film stacks are respectively used for reducing the reflection of the substrate surface, so that the high transmittance of a laser radar in a working wavelength range is ensured; and the reflection of the thin film surface is reduced, so that the obtained near-infrared optical filter is double-sided black. When the anti-reflection film is used as a laser radome, the external observation is black, and the anti-reflection film stack in the radome has low reflectivity and low transmittance for a visible light area, namely stray light, and has high transmittance for a near-infrared area, so that the normal work of a radar optical system can be ensured, and the anti-reflection film stack can be applied to the laser radome. And the influence of internal stray light on a radar system is effectively filtered.

Description

Technical Field

[0001] The invention belongs to the technical field of optical films and relates to a filter and a manufacturing method and application thereof. Background Art

[0002] With the rapid development of autonomous driving technology in the automotive industry, the application of LiDAR used in adaptive cruise control is becoming more and more widespread. Among them, the importance of the radome installed in front of the LiDAR for protection is gradually becoming more prominent. In addition to protecting the radar, the radome needs to be as black as possible to cover the functional components. On the other hand, it also has to play a filtering role to prevent too much stray light outside the working band of the LiDAR from entering the radar system, thereby ensuring the overall performance of the radar system.

[0003] Generally, multiple functional film layers are set on the radome to enhance the performance of the lidar system; for example, a multilayer film containing hydrogenated silicon and silicon oxide can be set to achieve high transmittance in the near-infrared band and low reflectivity in the visible light band, thereby ensuring that the light in the working band of the lidar can smoothly enter the radar system. At the same time, when the radome is observed from the outside, the radome appears black. However, in the prior art, the radar system is often interfered by stray light from the non-working band inside and outside the radome, resulting in performance degradation. Therefore, it is necessary to develop a new filter structure; when applied to the radome, it can effectively filter the stray light from the inside and outside of the radome to reduce the interference signal reaching the radar system and improve the performance of the radar system. Summary of the invention

[0004] In view of the problems existing in the prior art, the purpose of the present invention is to provide a filter and a method for manufacturing the same and an application thereof, wherein the filter is provided with an anti-reflection film stack, a high-transmittance film stack and an anti-reflection film stack formed in different stacking structures on a substrate in sequence. The present invention adds an anti-reflection film stack with a new stacking structure to make the obtained near-infrared filter double-sided black. When it is used as a laser radar cover, it is not only black when observed from the outside, but also because the anti-reflection film stack has low reflectivity and low transmittance in the visible light region, that is, stray light, and high transmittance in the near-infrared region inside the radar cover, it can also ensure the normal operation of the radar optical system while effectively filtering the influence of internal stray light on the radar system.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides an optical filter, comprising a substrate, and an optical film layer structure disposed on the substrate; the optical film layer structure comprises an anti-back reflection film stack, a high-transmittance film stack and an anti-reflection film stack stacked in sequence on the substrate; each film stack is formed by at least three dielectric film layers with different refractive indices according to different preset stacking structures, and the refractive indices of two adjacent dielectric film layers are different from each other;

[0007] The anti-reflection film stack is formed in a first preset stacking structure, and the first preset stacking structure includes (HL) a ML, where L, M and H are dielectric film layers of different materials with increasing refractive index, the lowercase English letters in the superscripts are the number of repetition periods of the sub-film stack in the corresponding brackets, and a is an integer.

[0008] In some specific embodiments, 4≤a≤8, for example, a can be 4, 5, 6, 7 or 8.

[0009] In some specific embodiments, the present invention provides an optical filter, comprising a substrate, and an optical film layer structure disposed on the substrate; the optical film layer structure comprises an anti-back reflection film stack, a high-transmittance film stack, and an anti-reflection film stack stacked in sequence on the substrate; each film stack is formed by at least three dielectric film layers with different refractive indices according to different preset stacking structures, and the refractive indices of two adjacent dielectric film layers are different from each other;

[0010] The anti-reflection film stack is formed in a first preset stacking structure, and the first preset stacking structure includes (HL) a ML, where L, M and H are dielectric film layers of different materials with increasing refractive index, the lowercase English letters in the superscripts are the number of repetition periods of the sub-film stack in the corresponding brackets, and 4≤a≤6, and a is an integer.

[0011] The influence of stray light is not eliminated inside the traditional laser radar cover. To solve this problem, the present invention proposes a new optical film layer structure. The optical film layer structure is set as an anti-back reflection film stack, a high-transmittance film stack and an anti-reflection film stack, so that the three are used to reduce the back reflection (Back Reflectance) of the substrate surface, ensure high transmittance in the near-infrared band such as the laser radar working wavelength range of 900-1000nm, and reduce the reflectivity (Reflectance) of the film layer surface in at least most of the visible light band; there are at least three dielectric film layers with different refractive indices in the three film stacks, preferably low refractive index (L), medium refractive index (M), and high refractive index (H) dielectric film layers, and the film stacks are formed according to different dielectric film layer stacking methods to achieve corresponding effects.

[0012] Compared with the traditional single-sided black filter or laser radar cover, the present invention adopts a new stacking structure and adds an anti-reflection film stack, so that the obtained near-infrared filter can be double-sided black. When it is used as a laser radar cover, on the one hand, it is black when observed from the outside; on the other hand, because the near-infrared filter with the anti-reflection film stack has low reflectivity and low transmittance for at least most of the light in the visible light region, that is, stray light, inside the radar cover, and has high transmittance for light in the near-infrared region of the working band, it can ensure the normal operation of the radar optical system while effectively filtering the influence of internal stray light on the radar system, that is, from the perspective of the radar optical system, it is also black in most of the visible light region.

[0013] The following are preferred technical solutions of the present invention, but are not intended to be limitations of the technical solutions provided by the present invention. Through the following technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0014] In some specific embodiments, the high-transmittance film stack is formed in a second preset stacking structure, and the second preset stacking structure includes LH (MH) b (LH) c LML, and 1≤b≤3, 5≤c≤12, b and c are both integers, for example, b can be 1, 2 or 3, and c can be 5, 6, 7, 8, 9, 10, 11 or 12.

[0015] As a preferred technical solution of the present invention, the high-transmittance film stack is formed with a second preset stacking structure, and the second preset stacking structure includes LH (MH) b (LH) c LML, and 1≤b≤3, 6≤c≤9, b and c are both integers, for example, b can be 1, 2 or 3, and c can be 6, 7, 8 or 9.

[0016] In some specific embodiments, the anti-reflection film stack is formed in a third preset stacking structure, and the third preset stacking structure includes LM (LH) d , and 4≤d≤8, and d is an integer, for example, d can be 4, 5, 6, 7 or 8.

[0017] Preferably, the anti-reflection film stack is formed in a third preset stacking structure, and the third preset stacking structure includes LM (LH) d , and 4≤d≤6, and d is an integer, for example, d can be 4, 5 or 6.

[0018] The anti-reflection film stack is preferably (LH) a ML, preferably a=5; the high permeability membrane stack is preferably LH (MH) b (LH) cThe anti-reflection film stack is preferably LM (LH) d , and preferably d=5.

[0019] As a preferred technical solution of the present invention, the thickness of the L dielectric film layer and the M dielectric film layer are independently selected from 5 to 100 nm, for example, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 13 nm, 15 nm, 17 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm or 100 nm, and the thickness of the H dielectric film layer is 5 to 240 nm, for example, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 13 nm, 15 nm, 17 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm or 100 nm. 0nm, 13nm, 15nm, 17nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 110nm, 120nm, 130nm, 140nm, 150nm, 160nm, 170nm, 180nm, 190nm, 200nm, 210nm, 220nm, 225nm, 230nm, 230nm or 240nm, but are not limited to the listed values, and other values ​​not listed within the above numerical range are equally applicable.

[0020] As a preferred technical solution of the present invention, the thickness of the anti-reflection film stack and the thickness of the anti-reflection film stack are independently 25% to 35% of the thickness of the high-transmittance film stack, for example, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34% or 35%, etc., but are not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0021] As a preferred technical solution of the present invention, the thickness of the anti-reflection film stack and the thickness of the anti-reflection film stack are independently selected from 400-500nm, for example, 400nm, 405nm, 410nm, 415nm, 420nm, 425nm, 430nm, 435nm, 440nm, 445nm, 450nm, 455nm, 460nm, 465nm, 470nm, 475nm, 480nm, 485nm, 490nm, 495nm or 500nm, but are not limited to the listed values, and other unlisted values ​​within the above numerical range are equally applicable.

[0022] As a preferred technical solution of the present invention, from 380 to 1080 nm, the refractive index of the L dielectric film layer is gradually reduced from 1.5 to 1.4, specifically including 1.4, 1.41, 1.42, 1.43, 1.44, 1.45, 1.46, 1.47, 1.48, 1.49 or 1.5, etc.; the refractive index of the M dielectric film layer is gradually reduced from 2.4 to, specifically including 2, 2.02, 2.04, 2.06, 2.08, 2.1, 2.12, 2.14, 2.16, 2.18, 2.2, 2.22, 2.24, 2.26, 2.28, 2 .3, 2.32, 2.34, 2.36, 2.38 or 2.4, etc.; the refractive index of the H dielectric film layer decreases from 6.0 to 3.2, specifically including 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9 or 6.0, etc., but are not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0023] As a preferred technical solution of the present invention, the L dielectric film layer includes a silicon oxide film layer; the M dielectric film layer includes a silicon nitride film layer or an aluminum nitride film layer; and the H dielectric film layer includes a hydrogenated silicon film layer.

[0024] As a preferred technical solution of the present invention, the silicon oxide film layer is a SiO2 film layer; the silicon nitride film layer or the aluminum nitride film layer is a Si3N4 film layer or an AlN film layer respectively; and the hydrogenated silicon film layer is a Si:H film layer.

[0025] As a preferred technical solution of the present invention, the substrate includes a glass substrate.

[0026] Preferably, the glass substrate is a D263T glass substrate.

[0027] Preferably, the thickness of the substrate is 0.8-1.2 mm, for example, 0.8 mm, 0.85 mm, 0.9 mm, 0.95 mm, 1 mm, 1.05 mm, 1.1 mm, 1.15 mm or 1.2 mm, but is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0028] In a second aspect, the present invention provides a method for manufacturing the optical filter according to the first aspect, the manufacturing method comprising using a sputtering coating method to coat layers on a substrate, forming an anti-back reflection film stack, a high-transmittance film stack and an anti-reflection film stack from bottom to top in sequence, forming an optical film layer structure, and obtaining the optical filter.

[0029] Preferably, the sputtering coating includes using a Si target to react with plasma of O2, N2 and H2 respectively to produce a silicon oxide film layer as the L dielectric film layer, a silicon nitride film layer or an aluminum nitride film layer as the M dielectric film layer, and a hydrogenated silicon film layer as the H dielectric film layer.

[0030] In a third aspect, the present invention provides an application of the external optical filter described in the first aspect or the optical filter obtained by the manufacturing method described in the second aspect, wherein the application includes a laser radar cover.

[0031] Compared with the prior art solutions, the present invention has at least the following beneficial effects:

[0032] The present invention is respectively based on LM (LH) d 、LH(MH) b (LH) c LML and (HL) a ML uses three different dielectric film stacking methods to set the optical film layer structure as an anti-back reflection film stack, a high-transmittance film stack and an anti-reflection film stack, so that the three are used to reduce the reflection of the substrate surface, ensure high transmittance within the laser radar working wavelength range of 900-1000nm, and reduce the reflection of the film surface; the resulting double-sided black near-infrared filter not only appears black when observed from the outside, but also when used as a laser radar cover, it can ensure beauty while the transmittance and reflectivity of the film surface in the internal system are very low, effectively eliminating the influence of stray light in the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a schematic structural diagram of the optical filter of the present invention;

[0034] Figure 2 is a schematic diagram of the optical filter of the present invention when it is applied to a laser radar;

[0035] Among them, 1-substrate, 2-anti-reflection film stack, 3-high transmittance film stack, 4-anti-reflection film stack, 5-radar cover, 6-radar unit;

[0036] Figure 3-Figure 5 They are the optical constant curves of Si:H dielectric film layer, SiO2 dielectric film layer and Si3N4 dielectric film layer respectively;

[0037] Figure 6-Figure 8 They are respectively a graph of the transmittance and wavelength of the filter in Example 1, a graph of the reflectance and wavelength on the film layer side, and a graph of the reflectance and wavelength on the substrate side;

[0038] Figure 9-11 They are respectively a graph of the transmittance and wavelength of the filter in Example 2, a graph of the reflectance and wavelength on the film layer side, and a graph of the reflectance and wavelength on the substrate side;

[0039] Figure 12-14 They are respectively a graph of the transmittance and wavelength of the filter in Example 3, a graph of the reflectance and wavelength on the film layer side, and a graph of the reflectance and wavelength on the substrate side;

[0040] Figure 15-17 They are respectively a graph of the transmittance and wavelength of the filter in Example 4, a graph of the reflectance and wavelength on the film layer side, and a graph of the reflectance and wavelength on the substrate side;

[0041] Figure 18-Figure 20 They are respectively a graph of the transmittance and wavelength of the filter in Comparative Example 1, a graph of the reflectance and wavelength on the film layer side, and a graph of the reflectance and wavelength on the substrate side;

[0042] Figure 21-23 They are respectively a graph of the transmittance and wavelength of the filter in Comparative Example 2, a graph of the reflectance and wavelength on the film layer side, and a graph of the reflectance and wavelength on the substrate side;

[0043] Figure 24-26 They are respectively a graph of the transmittance and wavelength of the filter in Comparative Example 3, a graph of the reflectance and wavelength on the film layer side, and a graph of the reflectance and wavelength on the substrate side;

[0044] Figure 27-Figure 29 They are respectively a graph of the transmittance and wavelength of the filter in Example 5, a graph of the reflectance and wavelength on the film layer side, and a graph of the reflectance and wavelength on the substrate side;

[0045] Figure 30-Figure 32 They are respectively a graph of the transmittance and wavelength of the filter in Example 6, a graph of the reflectance and wavelength on the film layer side, and a graph of the reflectance and wavelength on the substrate side;

[0046] Figure 33-Figure 35 They are respectively a graph of the transmittance and wavelength of the filter in Example 7, a graph of the reflectance and wavelength on the film layer side, and a graph of the reflectance and wavelength on the substrate side;

[0047] Figure 36-Figure 38 They are respectively a graph of the transmittance and wavelength of the filter in Example 8, a graph of the reflectance and wavelength on the film layer side, and a graph of the reflectance and wavelength on the substrate side;

[0048] Figure 39-41 They are respectively a graph showing the relationship between the transmittance and wavelength of the filter in Example 9, a graph showing the relationship between the reflectance and wavelength on the film layer side, and a graph showing the relationship between the reflectance and wavelength on the substrate side. DETAILED DESCRIPTION

[0049] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0050] Figure 1 Schematic diagram of the structure of the optical filter of the present invention, the optical filter includes a substrate 1, and an optical film layer structure arranged on the substrate 1; the optical film layer structure includes an anti-back reflection film stack 2, a high-transmittance film stack 3 and an anti-reflection film stack 4 stacked in sequence on the substrate 1; each film stack is formed by at least three dielectric film layers with different refractive indices according to different preset stacking structures, and the refractive indices of two adjacent dielectric film layers are different from each other.

[0051] Figure 2 This is a schematic diagram of the optical filter of the present invention applied to a laser radar, wherein the substrate 1 in the optical filter is a radar cover 5, the optical film layer structure is arranged on the inner surface of the radar cover 5, and the anti-reflection film stack 4 faces the internal radar unit 6; in the optical filter, the reflection on the side of the substrate 1 (radome 5) toward the outside of the radar is called back reflection (Back Reflectance), and the reflection on the side of the film layer, that is, on the side of the anti-reflection film stack 4 toward the inside of the radar is called reflection (Reflectance).

[0052] The relationship between the reflectivity and wavelength and the relationship between the transmittance and wavelength of the Si:H dielectric film layer, SiO2 dielectric film layer and Si3N4 dielectric film layer used in the embodiment are measured at an incident angle of 6°: Si:H single-layer film, SiO2 single-layer film and Si3N4 single-layer film are sputtered on the surface of a D263T glass substrate, and then the incident angle is controlled to be 6° to measure the reflectivity (recorded as 6°R) and transmittance (recorded as 6°T) of each single-layer film. Based on the above data, the optical constant curves of the Si:H dielectric film layer, SiO2 dielectric film layer and Si3N4 dielectric film layer are calculated by photometry. Figure 3-Figure 5 As shown in, within the wavelength range of 280 to 1080 nm, the refractive index of the SiO2 dielectric film layer is 1.4 to 1.5; the refractive index of the Si3N4 dielectric film layer is 2 to 2.4; and the refractive index of the Si:H dielectric film layer is 3.2 to 5.8, that is, the SiO2 dielectric film layer is a low refractive index (L) dielectric film layer, the Si3N4 dielectric film layer is a medium refractive index (M) dielectric film layer, and the Si:H dielectric film layer is a high refractive index (H) dielectric film layer.

[0053] The SiO2 dielectric film layer, Si3N4 dielectric film layer and Si:H dielectric film layer are subjected to a fully automatic sputtering coating process using the NSC-15 sputtering coating equipment manufactured by Optorun; the equipment includes 3 pairs of Si targets, the target power supply is a 40kHz medium frequency power supply, and a permanent magnet is embedded in the target. During sputtering coating, argon gas is introduced into the target, and the medium frequency power supply is used to excite the Ar argon molecules to ionize them into a plasma state. The alternating electric field of the target causes the argon ions to move in a directional manner (towards or away from the target surface). The moving argon ions are subjected to the Lorentz force in the magnetic field generated by the permanent magnet, bombarding the target surface, sputtering target atoms, and their movement direction is away from the target surface and deposited on the substrate surface. The substrate is set in a substrate fixture, and the substrate fixture is in a workpiece rotating mechanism. The substrate, substrate fixture, and workpiece rotating mechanism are relatively stationary. The workpiece rotating mechanism rotates at its rotation center at a rotation speed of 80 rpm, so that the workpiece rotating mechanism drives the substrate to rotate. The sputtered target Si atoms are transferred to the RF source along with the substrate, and oxygen, nitrogen or hydrogen is introduced into the RF source. Under the RF excitation, O2, N2 or H2 are ionized into plasma, completing the Si+O - →SiO2、Si+N 2- →Si3N4 and Si+H - →Si:H reaction process. Plasma can assist the deposition of the film layer to improve the density of the film layer, thereby producing SiO2 dielectric film layer, Si3N4 dielectric film layer and Si:H dielectric film layer on the substrate or on the previous film layer.

[0054] The specific process parameters are: when plating Si:H, each pair of targets is filled with 300sccm Ar, and a pair of ICPs uses a power of 3.5kw, and is filled with 220sccm Ar and 70sccm H2; when plating SiO2, each pair of targets is filled with 300sccm Ar, and a pair of ICPs uses a power of 3.5kw, and is filled with 220sccm Ar and 350sccm O2; when plating Si3N4, each pair of targets is filled with 300sccm Ar, and a pair of ICPs uses a power of 3.5kw, and is filled with 220sccm Ar and 300sccm N2; the process file designs the materials and thickness of the film system and alternately plates Si:H, SiO2, and Si3N4 to form an optical film layer structure.

[0055] Example 1

[0056] The present embodiment provides an optical filter, which includes a substrate and an optical film layer structure disposed on the substrate; the optical film layer structure includes an anti-back reflection film stack, a high-transmittance film stack and an anti-reflection film stack stacked in sequence on the substrate; each film stack is formed by three dielectric film layers with different refractive indices according to different preset stacking structures, namely, a low refractive index (L) SiO2 dielectric film layer, a medium refractive index (M) Si3N4 dielectric film layer and a high refractive index (H) Si:H dielectric film layer, and the refractive indices of two adjacent dielectric film layers are different from each other;

[0057] The high-transmittance film stack has a second preset stacking structure LH (MH) 2 (LH) 8 LML is formed, and the anti-reflection film stack has a third preset stacking structure LM (LH) 5 The anti-reflection film stack is formed in a first preset stacking structure (HL) 5 ML formation, all the superscript numbers represent the number of repetition cycles of the sub-film stack in brackets, and the thickness of each dielectric film layer is set according to Table 1;

[0058] Table 1

[0059]

[0060]

[0061] Taking the optical filter of the present embodiment as an example, when the optical filter is completely manufactured, the D263T glass substrate is placed in the above-mentioned NSC-15 equipment-specific sample box, and the transport command is input, the sample is automatically moved into the process chamber, and the thickness of the dielectric film layer of each serial number is input into the NSC-15 equipment-specific process file. In the electronic spreadsheet of the process file, each layer occupies a row. After executing the sputtering coating command, the equipment enters the fully automatic coating process. The system scans the entire electronic spreadsheet line by line, first coating the first layer. After the first layer is completed, the second layer is coated until all 49 layers are completed. Then the move-out command is executed, and the sample is moved from the process chamber to the sample box, and the coating is completed to obtain the optical filter.

[0062] Figure 6-8 The relationship between the transmittance and reflectance of the filter obtained in this embodiment and the wavelength is shown in FIG. Figure 6 It can be seen that the filter maintains high transmittance in the near-infrared band of 900-1000nm and low transmittance in the visible light region, ensuring the filtering performance of the laser radar cover. Figure 7 Back reflection, low reflectivity in the visible light region between 400 and 700 nm (combined with Figure 6 Low transmittance in the visible light region) can ensure the appearance is black and play a decorative role; Figure 8 Film surface reflection, low reflectivity in the visible light region between 400 and 700 nm (combined with Figure 6 The interior of the radar cover is still black and has a low reflectivity, which prevents the reflection of stray light in the radar system from affecting the overall effect. That is, the resulting filter is a double-sided black infrared filter.

[0063] Example 2

[0064] This embodiment provides a filter, except that the second preset stacking structure of the high-transmittance film stack is LH (MH) 2 (LH) 8 LML adjusted to LH(MH) 2 (LH) 9 LML, other membrane stacks are the same as in Example 1.

[0065] Example 3

[0066] This embodiment provides a filter, except that the third preset stacking structure of the anti-back reflection film stack is composed of LM (LH) 5 Adjusted to LM(LH) 4 , other membrane stacks are the same as those in Example 1.

[0067] Example 4

[0068] This embodiment provides a filter, except that the third preset stacking structure of the anti-back reflection film stack is composed of LM (LH) 5 Adjusted to LM(LH) 6 , other membrane stacks are the same as those in Example 1.

[0069] Example 5

[0070] This embodiment provides a filter, except that the second preset stacking structure of the high-transmittance film stack is LH (MH) 2 (LH) 8 LML adjusted to LH(MH) 2 (LH) 5 LML, other membrane stacks are the same as in Example 1.

[0071] Example 6

[0072] This embodiment provides a filter, except that the second preset stacking structure of the high-transmittance film stack is LH (MH) 2 (LH) 8 LML adjusted to LH(MH) 2 (LH) 12 LML, other membrane stacks are the same as in Example 1.

[0073] Example 7

[0074] This embodiment provides a filter, except that the third preset stacking structure of the anti-back reflection film stack is composed of LM (LH) 5 Adjusted to LM(LH) 8 , other membrane stacks are the same as those in Example 1.

[0075] Example 8

[0076] This embodiment provides an optical filter, except that the first preset stacking structure of the anti-reflection film stack is (HL) 5 ML adjusted to (HL) 4 ML, other membrane stacks are the same as in Example 1.

[0077] Example 9

[0078] This embodiment provides an optical filter, except that the first preset stacking structure of the anti-reflection film stack is (HL) 5 ML adjusted to (HL) 8 ML, other membrane stacks are the same as in Example 1.

[0079] Comparative Example 1

[0080] This comparative example provides a filter, except that the second preset stacking structure of the high-transmittance film stack is LH (MH) 2 (LH) 8 LML adjusted to LH (LH) 8 LML, other membrane stacks are the same as in Example 1.

[0081] Comparative Example 2

[0082] This comparative example provides a filter, except that the second preset stacking structure of the high-transmittance film stack is LH (MH) 2 (LH) 8 LML adjusted to LH(MH) 2 (LH) 8 L, other membrane stacks are the same as in Example 1.

[0083] Comparative Example 3

[0084] This comparative example provides a common single-sided black near-infrared filter, wherein the anti-reflection film stack (HL) 5 ML was removed, and other membrane stacks were the same as in Example 1.

[0085] Figure 9-Figure 26 The relationship between the transmittance and reflectance of the filters in Examples 2-4 and Comparative Examples 1-3 and the wavelength is shown in Figure 1, where compared with Example 1:

[0086] In Example 2, since the high-transmittance film stack is adjusted from LH(MH)2(LH)8LML to LH(MH)2(LH)9LML, the transmittance at 900-1000nm is 95.8%, which is 0.3% lower than 96.1% in Example 1; the reflectivity of the coating surface at 400-700nm is 1.294%, which is not much different from 1.121% in Example 1; the reflectivity of the back reflection surface at 400-700nm is 0.461%, which is 0.46% lower than 0.921% in Example 1. Therefore, the transmittance of the filter obtained in Example 2 is reduced, but is generally close to that in Example 1.

[0087] In Example 3, the anti-back reflection film stack is adjusted from LM (LH) 5 to LM (LH) 4, and the transmittance at 900-1000nm is 96%, which is not much different from 96.1% in Example 1; the reflectivity of the coated surface at 400-700nm is 1.123%, which is not much different from 1.121% in Example 1; the reflectivity of the back reflection surface at 400-700nm is 0.925%, which is not much different from 0.921% in Example 1. Therefore, the overall filter obtained in Example 3 is close to that in Example 1.

[0088] In Example 4, the anti-back reflection film stack is adjusted from LM (LH) 5 to LM (LH) 6, and the transmittance at 900-1000nm is 95.9%, which is 0.2% lower than 96.1% in Example 1; the reflectivity of the coated surface at 400-700nm is 1.128%, which is not much different from 1.121% in Example 1; the reflectivity of the back reflection surface at 400-700nm is 3.674%, which is 2.753% higher than 0.921% in Example 1. Therefore, the back reflection of the filter obtained in Example 4 is higher than that in Example 1.

[0089] In Comparative Example 1, the high-transmittance film stack is adjusted from LH(MH)2(LH)8LML to LH(LH)8LML, and the transmittance at 900-1000nm is 88.8%, which is 7.3% lower than 96.1% in Example 1; the reflectivity of the coating surface at 400-700nm is 1.194%, which is not much different from 1.121% in Example 1; the reflectivity of the back reflection surface at 400-700nm is 1.551%, which is 0.63% higher than 0.921% in Example 1. Therefore, the back reflection and coating surface reflection of Comparative Example 1 are not much different from those of Example 1, but the transmittance is significantly reduced because the high-transmittance film stack lacks the (MH) layer.

[0090] In Comparative Example 2, the high-transmittance film stack is adjusted from LH(MH)2(LH)8LML to LH(MH)2(LH)8L, and the transmittance at 900-1000nm is 75.2%, which is 20.9% lower than 96.1% in Example 1; the reflectivity of the coating surface at 400-700nm is 1.398%, which is slightly different from 1.121% in Example 1; the reflectivity of the back reflection surface at 400-700nm is 0.932%, which is slightly different from 0.921% in Example 1. Therefore, compared with Example 1, the back reflection and coating surface reflection of Comparative Example 2 are not much different. However, since the high-transmittance film stack lacks the ML layer, the transmittance is significantly reduced.

[0091] In Comparative Example 3, the anti-reflection film stack is removed, and the transmittance at 900-1000nm is 96.6%, which is 0.5% higher than 96.1% in Example 1; the reflectivity of the coated surface at 400-700nm is 70.935%, which is 0.497% lower than 0.921% in Example 1; therefore, compared with Example 1, the back reflection and transmittance of Comparative Example 3 are not much different, but due to the lack of the anti-reflection film stack, the reflectivity of the coated surface is increased, and when it is applied to the radar cover, it cannot effectively filter the influence of internal stray light on the radar system.

[0092] Figure 27-Figure 29 The graphs respectively show the relationship between the transmittance and reflectance of the filters in Examples 5-9 and the wavelength. It can be seen from the graphs that the obtained filters are all qualified when applied to the radome, that is, since the anti-reflection film stack inside the radome has sufficiently low reflectivity and low transmittance for the visible light region, that is, stray light, and has sufficiently high transmittance for the near-infrared region, therefore, it can maintain a relatively high transmittance within the operating wavelength range of the laser radar, allowing the radar to work normally, and can reduce the reflection of the film surface, thereby ensuring the normal operation of the radar optical system while effectively filtering the influence of internal stray light on the radar system.

[0093] The present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0094] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0095] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0096] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A filter, characterized in that: The invention comprises a substrate and an optical film layer structure arranged on the substrate; the optical film layer structure comprises an anti-back reflection film stack, a high-transmittance film stack and an anti-reflection film stack which are sequentially stacked on the substrate; each film stack is formed by at least three dielectric film layers with different refractive indices according to different preset stacking structures, and the refractive indices of two adjacent dielectric film layers are different from each other; The anti-reflection film stack is formed in a first preset stacking structure, and the first preset stacking structure includes (HL) a ML, where L, M and H are dielectric film layers of different materials with increasing refractive index, the lowercase English letters in the superscripts are the number of repetition periods of the sub-film stack in the corresponding brackets, and a is an integer.

2. The optical filter according to claim 1, characterized in that: 4≤a≤8, more preferably 4≤a≤6; Preferably, the high-transmittance film stack is formed in a second preset stacking structure, and the second preset stacking structure includes LH (MH) b (LH) c LML, and 1≤b≤3, 5≤c≤12, more preferably 6≤c≤9, b and c are both integers; Preferably, the anti-reflection film stack is formed in a third preset stacking structure, and the third preset stacking structure includes LM (LH) d , and 4≤d≤8, more preferably 4≤d≤6, and d is an integer.

3. The optical filter according to claim 1 or 2, characterized in that: The thickness of the L dielectric film layer and the M dielectric film layer are independently selected from 5 to 100 nm; the thickness of the H dielectric film layer is 5 to 240 nm.

4. The optical filter according to any one of claims 1 to 3, characterized in that: The thickness of the anti-back reflection film stack and the thickness of the anti-reflection film stack are both independently 25% to 35% of the thickness of the high-transmittance film stack.

5. The optical filter according to claim 4, characterized in that: The thickness of the anti-reflection film stack and the thickness of the anti-reflection film stack are independently selected from 400 to 500 nm.

6. The optical filter according to any one of claims 1 to 5, characterized in that: From 380 to 1080 nm, the refractive index of the L dielectric film layer gradually decreases from 1.5 to 1.4, the refractive index of the M dielectric film layer gradually decreases from 2.4 to 2, and the refractive index of the H dielectric film layer gradually decreases from 6.0 to 3.

2.

7. The optical filter according to any one of claims 1 to 6, characterized in that: The L dielectric film layer includes a silicon oxide film layer; the M dielectric film layer includes a silicon nitride film layer or an aluminum nitride AlN film layer; and the H dielectric film layer includes a hydrogenated silicon film layer; Preferably, the silicon oxide film layer is a SiO2 film layer; the silicon nitride film layer or the aluminum nitride film layer is a Si3N4 film layer or an AlN film layer respectively; and the hydrogenated silicon film layer is a Si:H film layer.

8. The optical filter according to any one of claims 1 to 7, characterized in that: The substrate comprises a glass substrate; Preferably, the glass substrate is a D263T glass substrate; Preferably, the thickness of the substrate is 0.8-1.2 mm.

9. The method for manufacturing the optical filter according to any one of claims 1 to 8, characterized in that: The manufacturing method includes using a sputtering coating method to coat films layer by layer on a substrate, forming an anti-back reflection film stack, a high-transmittance film stack and an anti-reflection film stack from bottom to top in order to form an optical film layer structure and obtain a filter; Preferably, the sputtering coating includes using a Si target to react with plasma of O2, N2 and H2 respectively to produce a silicon oxide film layer as the L dielectric film layer, a silicon nitride film layer or an aluminum nitride film layer as the M dielectric film layer, and a hydrogenated silicon film layer as the H dielectric film layer.

10. An application of the optical filter according to any one of claims 1 to 8 or the optical filter obtained by the manufacturing method according to claim 9, characterized in that: The applications include lidar radomes.

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