An ultra-low reflectivity optical antireflection film

Abstract

The present invention discloses an ultra-low reflectivity optical anti-reflection film, wherein the ultra-low residual reflectivity optical anti-reflection film comprises an anti-reflection film body for fixing to optical glass, wherein the anti-reflection film body has a proximal end for fixing to the optical glass, and a distal end away from the optical glass; the anti-reflection film body comprises thirteen film layers, wherein the thirteen film layers comprise seven magnesium fluoride film layers and six lanthanum titanate film layers, wherein the magnesium fluoride film layers and the lanthanum titanate film layers are alternately stacked from proximal to distal. A 13-layer film design is adopted, wherein two high and low refractive index film layers, the lanthanum titanate film layer and the magnesium fluoride film layer, are alternately distributed. The anti-reflection film body has the advantages of low residual reflectivity, low film layer sensitivity, no thin layer, and good film system process stability.

Description

Technical Field

[0001] The present invention relates to the technical field of optical anti-reflection films, and in particular to an optical anti-reflection film with ultra-low reflectivity. Background Art

[0002] Light is an electromagnetic wave. When an electromagnetic wave propagates from one medium to another, the energy of the electromagnetic field will be redistributed at the interface due to the different physical properties of the media. The role of the antireflection film is to change the boundary conditions of the interface between optical glass and air, affecting the energy distribution during light propagation, thereby achieving the effect of enhancing the transmitted light.

[0003] Ordinary optical glass, without surface coating, has a reflectivity of over 4%. As optical system performance requirements become increasingly demanding, a zoom optical system may require up to 20 optical lenses. Without an anti-reflection coating, the system's energy transmittance is reduced to only 20%. Furthermore, this 4% of reflected light will be refracted and reflected multiple times within the optical system, forming stray light, all of which will severely impact the system's actual performance. Currently, the residual reflectivity of mainstream optical anti-reflection coatings is approximately 0.5%, resulting in an optical system with 20 lenses having an energy transmittance of approximately 82%. This is a result that only considers surface reflections. If factors such as the absorption rate of the optical material, the absorption rate of the coating, and optical system vignetting are taken into account, the overall system transmittance will be even lower. If the residual reflectivity of an optical anti-reflection coating can be controlled below 0.1%, the theoretical energy transmittance of an optical system with 20 lenses can reach 96%, a significant improvement compared to a residual reflectivity of 0.5%. From the above analysis, it can be seen that further reducing the residual reflectivity of the optical anti-reflection film can not only effectively suppress the system stray light caused by the residual reflected light, but also help to ensure the transmittance performance of the optical system, and will significantly improve the imaging capability of the optical system in low-light and even night environments. Summary of the Invention

[0004] The main purpose of the present invention is to provide an optical antireflection film with ultra-low reflectivity, aiming to improve the technical problem of excessively high residual reflectivity of optical antireflection film technology in the prior art.

[0005] To achieve the above objectives, the present invention provides an ultra-low reflectivity optical anti-reflection film for application on optical glass. The ultra-low residual reflectivity optical anti-reflection film comprises an anti-reflection film body for fixing to the optical glass, the anti-reflection film body having a proximal end for fixing to the optical glass and a distal end away from the optical glass.

[0006] The antireflection film body includes thirteen film layers, including seven magnesium fluoride film layers and six lanthanum titanate film layers. The magnesium fluoride film layers and the lanthanum titanate film layers are alternately stacked from near to far.

[0007] Optionally, the thickness of each of the thirteen film layers is greater than 10 nm.

[0008] Optionally, the seven magnesium fluoride film layers are, from near to far, respectively a first magnesium fluoride film layer, a second magnesium fluoride film layer, a third magnesium fluoride film layer, a fourth magnesium fluoride film layer, a fifth magnesium fluoride film layer, a sixth magnesium fluoride film layer, and a seventh magnesium fluoride film layer;

[0009] The first magnesium fluoride film layer has a thickness of 26.85 nm to 27.05 nm; and / or,

[0010] The second magnesium fluoride film layer has a thickness of 204.04 nm to 204.24 nm; and / or,

[0011] The third magnesium fluoride film layer has a thickness of 15.90 nm to 16.10 nm; and / or,

[0012] The fourth magnesium fluoride film layer has a thickness of 54.66 nm to 54.86 nm; and / or,

[0013] The fifth magnesium fluoride film layer has a thickness of 83.14 nm to 83.34 nm; and / or

[0014] The sixth magnesium fluoride film layer has a thickness of 14.90 nm to 15.20 nm; and / or,

[0015] The seventh magnesium fluoride film layer has a thickness of 97.41 nm to 97.61 nm.

[0016] Optionally, the thickness of the first magnesium fluoride film layer is 26.95 nm, the thickness of the second magnesium fluoride film layer is 204.14 nm, the thickness of the third magnesium fluoride film layer is 16.00 nm, the thickness of the fourth magnesium fluoride film layer is 54.76 nm, the thickness of the fifth magnesium fluoride film layer is 83.24 nm, the thickness of the sixth magnesium fluoride film layer is 15.00 nm, and the thickness of the seventh magnesium fluoride film layer is 97.51 nm.

[0017] Optionally, the six lanthanum titanate film layers are, from near to far, a first lanthanum titanate film layer, a second lanthanum titanate film layer, a third lanthanum titanate film layer, a fourth lanthanum titanate film layer, a fifth lanthanum titanate film layer, and a sixth lanthanum titanate film layer;

[0018] The first lanthanum titanate film layer has a thickness of 14.98 nm to 15.18 nm; and / or,

[0019] The second lanthanum titanate film layer has a thickness of 17.91 nm to 18.11 nm; and / or,

[0020] The third lanthanum titanate film layer has a thickness of 112.53 nm to 112.73 nm; and / or,

[0021] The fourth lanthanum titanate film layer has a thickness of 14.90 nm to 15.10 nm; and / or,

[0022] The fifth lanthanum titanate film layer has a thickness of 43.36 nm to 43.56 nm; and / or,

[0023] The sixth lanthanum titanate film layer has a thickness of 61.39 nm to 61.59 nm.

[0024] Optionally, the thickness of the first lanthanum titanate film layer is 15.08 nm, the thickness of the second lanthanum titanate film layer is 18.01 nm, the thickness of the third lanthanum titanate film layer is 112.63 nm, the thickness of the fourth lanthanum titanate film layer is 15.00 nm, the thickness of the fifth lanthanum titanate film layer is 43.46 nm, and the thickness of the sixth lanthanum titanate film layer is 61.49 nm.

[0025] Optionally, the refractive index of the magnesium fluoride film layer is 1.364-1.384.

[0026] Optionally, the refractive index of the magnesium fluoride film layer is 1.374.

[0027] Optionally, the refractive index of the lanthanum titanate film layer is 2.054-2.074.

[0028] Optionally, the refractive index of the lanthanum titanate film layer is 2.064.

[0029] The technical solution provided by this invention utilizes a 13-layer design, with alternating layers of high and low refractive index films, MGF2 and H4. This high-quality, low-residual-reflectivity optical antireflection film exhibits a residual reflectivity of less than 0.1% over an ultra-wide wavelength range of 410 nm to 740 nm, and a flat reflectivity curve with no distinct reflection peaks. This invention not only effectively reduces the residual reflectivity on the lens surface and suppresses system stray light, but also helps maintain the transmittance performance of the optical system and significantly enhances the imaging capabilities of the optical system in low-light and even nighttime environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. 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 the structures shown in these drawings without paying any creative work.

[0031] Figure 1 A schematic structural diagram of an embodiment of an ultra-low reflectivity optical antireflection film provided by the present invention;

[0032] Figure 2 for Figure 1 Residual reflectivity curve of optical antireflection coating with medium and ultra-low reflectivity;

[0033] Figure 3 Figure 1 Schematic diagram of the sensitivity of each layer of an ultra-low reflectivity optical anti-reflection coating.

[0034] Description of Figure Numbers:

[0035] Label name Label name 100 Ultra-low reflectivity optical anti-reflection coating 101 optical glass

[0036] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0038] It should be noted that if a directional indication is involved in an embodiment of the present invention, the directional indication is only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0039] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the meaning of "and / or" appearing throughout the text includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme in which A and B are satisfied at the same time. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement it. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0040] Light is an electromagnetic wave. When an electromagnetic wave propagates from one medium to another, the energy of the electromagnetic field will be redistributed at the interface due to the different physical properties of the media. The role of the antireflection film is to change the boundary conditions of the interface between optical glass and air, affecting the energy distribution during light propagation, thereby achieving the effect of enhancing the transmitted light.

[0041] Ordinary optical glass, without surface coating, has a reflectivity of over 4%. As optical system performance requirements become increasingly demanding, a zoom optical system may require up to 20 optical lenses. Without an anti-reflection coating, the system's energy transmittance is reduced to only 20%. Furthermore, this 4% of reflected light will be refracted and reflected multiple times within the optical system, forming stray light, all of which will severely impact the system's actual performance. Currently, the residual reflectivity of mainstream optical anti-reflection coatings is approximately 0.5%, resulting in an optical system with 20 lenses having an energy transmittance of approximately 82%. This is a result that only considers surface reflections. If factors such as the absorption rate of the optical material, the absorption rate of the coating, and optical system vignetting are taken into account, the overall system transmittance will be even lower. If the residual reflectivity of an optical anti-reflection coating can be controlled below 0.1%, the theoretical energy transmittance of an optical system with 20 lenses can reach 96%, a significant improvement compared to a residual reflectivity of 0.5%. From the above analysis, it can be seen that further reducing the residual reflectivity of the optical anti-reflection film can not only effectively suppress the system stray light caused by the residual reflected light, but also help to ensure the transmittance performance of the optical system, and will significantly improve the imaging capability of the optical system in low-light and even night environments.

[0042] In view of this, the present invention provides an ultra-low reflectivity optical anti-reflection film, which aims to improve the technical problem of excessively high residual reflectivity of optical anti-reflection film technology in the prior art. Figures 1 to 3 This is an embodiment of the ultra-low reflectivity optical antireflection film provided by the present invention.

[0043] This embodiment provides an ultra-low reflectivity optical anti-reflection film 100. The ultra-low residual reflectivity optical anti-reflection film 100 includes an anti-reflection film body for fixing to an optical glass 101. The anti-reflection film body has a proximal end for fixing to the optical glass and a distal end away from the optical glass. The anti-reflection film body includes thirteen film layers, the thirteen film layers including seven magnesium fluoride film layers and six lanthanum titanate film layers, and the magnesium fluoride film layers and the lanthanum titanate film layers are alternately stacked from proximal to distal. A 13-layer film design is adopted, with two high and low refractive index film layers, magnesium fluoride film layers (MGF2) and lanthanum titanate film layers (H4), alternately distributed. The optical anti-reflection film of the present invention has the advantages of low residual reflectivity, low film sensitivity, no thin layer, and good film system process stability. The biggest advantage is that its residual reflectivity in the ultra-wide wavelength range of 410nm to 740nm is less than 0.1%. Compared with ordinary anti-reflection coatings, it can not only effectively reduce the residual reflectivity of the lens surface and suppress the stray light of the system, but also is more conducive to ensuring the transmittance performance of the optical system and significantly improving the imaging capability of the corresponding optical system in low light and even night environments.

[0044] like Figure 1The figure shows a schematic structural diagram of a low residual reflectivity optical anti-reflection film 100 of the present invention, which comprises a total of 13 layers of film systems with alternating high and low refractive index layers. The base material of the film system is the commonly used optical glass 101H-ZF4A_SCHOTT, which has a refractive index of 1.733 at 550nm. The structure of the 13-layer film system is G|(LH)6L|A, where G represents the base optical glass 101H-ZF4A, L represents the low refractive index magnesium fluoride film layer (MGF2), H represents the high refractive index lanthanum titanate film layer (H4), and A represents air. The low refractive index film material is the magnesium fluoride film layer (MGF2) and the high refractive index lanthanum titanate film layer (H4). The two coating materials used in the above-mentioned low residual reflectivity optical anti-reflection film are both commonly used coating materials, which have the advantages of stable performance and small extinction coefficient, which is beneficial to the quality assurance of the film system.

[0045] Furthermore, in this embodiment, each of the thirteen layers is greater than 10 nm thick. Generally speaking, thin layers in an antireflection film system are sensitive, and the thinnest layer is generally required to be no less than 10 nm. The thinnest layer in the 13-layer film system is 15 nm thick, avoiding processing stability issues caused by excessively thin layers.

[0046] Furthermore, in this embodiment, the seven magnesium fluoride film layers are, from near to far, respectively: a first magnesium fluoride film layer, a second magnesium fluoride film layer, a third magnesium fluoride film layer, a fourth magnesium fluoride film layer, a fifth magnesium fluoride film layer, a sixth magnesium fluoride film layer, and a seventh magnesium fluoride film layer. The first magnesium fluoride film layer has a thickness of 26.85 nm to 27.05 nm; the second magnesium fluoride film layer has a thickness of 204.04 nm to 204.24 nm; the third magnesium fluoride film layer has a thickness of 15.90 nm to 16.10 nm; the fourth magnesium fluoride film layer has a thickness of 54.66 nm to 54.86 nm; the fifth magnesium fluoride film layer has a thickness of 83.14 nm to 83.34 nm; the sixth magnesium fluoride film layer has a thickness of 14.90 nm to 15.20 nm; and the seventh magnesium fluoride film layer has a thickness of 97.41 nm to 97.61 nm.

[0047] Furthermore, in this embodiment, the thickness of the first magnesium fluoride film layer is 26.95 nm, the thickness of the second magnesium fluoride film layer is 204.14 nm, the thickness of the third magnesium fluoride film layer is 16.00 nm, the thickness of the fourth magnesium fluoride film layer is 54.76 nm, the thickness of the fifth magnesium fluoride film layer is 83.24 nm, the thickness of the sixth magnesium fluoride film layer is 15.00 nm, and the thickness of the seventh magnesium fluoride film layer is 97.51 nm.

[0048] Furthermore, in this embodiment, the six lanthanum titanate film layers are, from near to far, the first lanthanum titanate film layer, the second lanthanum titanate film layer, the third lanthanum titanate film layer, the fourth lanthanum titanate film layer, the fifth lanthanum titanate film layer, and the sixth lanthanum titanate film layer; the first lanthanum titanate film layer has a thickness of 14.98nm-15.18nm; the second lanthanum titanate film layer has a thickness of 17.91nm-18.11nm; the third lanthanum titanate film layer has a thickness of 112.53nm-112.73nm; the fourth lanthanum titanate film layer has a thickness of 14.90nm-15.10nm; the fifth lanthanum titanate film layer has a thickness of 43.36nm-43.56nm; and the sixth lanthanum titanate film layer has a thickness of 61.39nm-61.59nm.

[0049] Furthermore, in this embodiment, the thickness of the first lanthanum titanate film layer is 15.08 nm, the thickness of the second lanthanum titanate film layer is 18.01 nm, the thickness of the third lanthanum titanate film layer is 112.63 nm, the thickness of the fourth lanthanum titanate film layer is 15.00 nm, the thickness of the fifth lanthanum titanate film layer is 43.46 nm, and the thickness of the sixth lanthanum titanate film layer is 61.49 nm.

[0050] The residual reflectivity of this film system is less than 0.1% in a wide wavelength range of 410nm to 740nm, and the reflectivity curve is relatively flat without obvious reflection peak.

[0051] Furthermore, in this embodiment, the refractive index of the magnesium fluoride film layer is 1.364-1.384.

[0052] Specifically, the refractive index of the magnesium fluoride film is 1.374. The measured refractive index of the magnesium fluoride film during production on a coating machine is 1.374. The refractive index of the base optical glass 101 is 1.733, the test wavelength is 550 nm, and the incident angle of the light is 0°.

[0053] Furthermore, in this embodiment, the refractive index of the lanthanum titanate film layer is 2.054-2.074.

[0054] Specifically, the refractive index of the lanthanum titanate film is 2.064. The measured refractive index of the lanthanum titanate film during production on a coating machine is 2.064. The refractive index of the base optical glass is 1.733, the test wavelength is 550nm, and the light incident angle is 0°.

[0055] It adopts a 13-layer film structure, with the thickness of the first MGF2 film layer being 26.95nm; the thickness of the second H4 film layer being 15.08nm; the thickness of the third MGF2 film layer being 204.14nm; the thickness of the fourth H4 film layer being 18.01nm; the thickness of the fifth MGF2 film layer being 16.00nm; the thickness of the sixth H4 film layer being 112.63nm; the thickness of the seventh MGF2 film layer being 54.76nm; the thickness of the eighth H4 film layer being 15.00nm; the thickness of the ninth MGF2 film layer being 83.24nm; the thickness of the tenth H4 film layer being 43.46nm; the thickness of the eleventh MGF2 film layer being 15.00nm; the thickness of the twelfth H4 film layer being 61.49nm; and the thickness of the thirteenth MGF2 film layer being 97.51nm.

[0056] Figure 2 The figure shows the residual reflectivity curve of the optical antireflection film of the present invention. It can be seen that the present invention has the following advantages: the residual reflectivity curve is very flat, with the residual reflectivity being less than 0.1% within the ultra-wide wavelength range of 410nm to 740nm, and there is no obvious reflection peak. Therefore, this high-quality, low residual reflectivity optical antireflection film has no obvious film color. The above-mentioned optical antireflection film can not only effectively reduce the residual reflectivity of the lens surface and suppress the system's stray light, but also help to ensure the transmittance performance of the optical system. The residual reflectivity wavelength range constrained in the design is wider than the commonly used wavelength range of 420nm to 680nm. The main purpose is to leave a sufficient tolerance range for the film processing technology, and to fully ensure the performance of the lens edge film when the film system is applied to lenses with a smaller radius of curvature.

[0057] Figure 3 The first-order and second-order sensitivities of the film systems of the present invention are shown in the figure. The horizontal axis represents the different film layers, and the vertical axis represents the sensitivity of the film layer. The larger the sensitivity coefficient, the higher the sensitivity of the film layer. It can be seen that the sensitivity coefficients of all 13 film layers are on the order of 10-6, and the surface film layer sensitivity is relatively low. In other words, even if certain errors occur during actual processing, it will not significantly affect the performance of the film system. Therefore, the high-quality, low residual reflectivity optical antireflection film of the present invention has good stability and meets the requirements of large-scale mass production.

[0058] The above descriptions are merely optional embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present invention's description and drawings, or direct / indirect applications in other related technical fields, within the scope of the present invention are included in the patent protection scope of the present invention.

Claims

1. An optical antireflection film with ultra-low residual reflectivity, applied to optical glass, characterized in that: The ultra-low residual reflectivity optical anti-reflection film comprises an anti-reflection film body for fixing to the optical glass, wherein the anti-reflection film body has a proximal end for fixing to the optical glass and a distal end away from the optical glass; The antireflection film body includes thirteen film layers, the thirteen film layers include seven magnesium fluoride film layers and six lanthanum titanate film layers, and the magnesium fluoride film layers and the lanthanum titanate film layers are alternately stacked from near to far; Among them, the seven magnesium fluoride film layers are respectively the first magnesium fluoride film layer, the second magnesium fluoride film layer, the third magnesium fluoride film layer, the fourth magnesium fluoride film layer, the fifth magnesium fluoride film layer, the sixth magnesium fluoride film layer, and the seventh magnesium fluoride film layer from near to far; the first magnesium fluoride film layer has a thickness of 26.85nm-27.05nm; the second magnesium fluoride film layer has a thickness of 204.04nm-204.24nm; the third magnesium fluoride film layer has a thickness of 15.90nm-16.10nm; the fourth magnesium fluoride film layer has a thickness of 54.66nm-54.86nm; the fifth magnesium fluoride film layer has a thickness of 83.14nm-83.34nm; the sixth magnesium fluoride film layer has a thickness of 14.90nm-15.20nm; the seventh magnesium fluoride film layer has a thickness of 97.41nm-97.61nm; The six lanthanum titanate film layers are, from near to far, the first lanthanum titanate film layer, the second lanthanum titanate film layer, the third lanthanum titanate film layer, the fourth lanthanum titanate film layer, the fifth lanthanum titanate film layer, and the sixth lanthanum titanate film layer; the first lanthanum titanate film layer has a thickness of 14.98nm-15.18nm; the second lanthanum titanate film layer has a thickness of 17.91nm-18.11nm; the third lanthanum titanate film layer has a thickness of 112.53nm-112.73nm; the fourth lanthanum titanate film layer has a thickness of 14.90nm-15.10nm; the fifth lanthanum titanate film layer has a thickness of 43.36nm-43.56nm; the sixth lanthanum titanate film layer has a thickness of 61.39nm-61.59nm.

2. The ultra-low residual reflectivity optical antireflection film according to claim 1, characterized in that: The thickness of the first magnesium fluoride film layer is 26.95 nm, the thickness of the second magnesium fluoride film layer is 204.14 nm, the thickness of the third magnesium fluoride film layer is 16.00 nm, the thickness of the fourth magnesium fluoride film layer is 54.76 nm, the thickness of the fifth magnesium fluoride film layer is 83.24 nm, the thickness of the sixth magnesium fluoride film layer is 15.00 nm, and the thickness of the seventh magnesium fluoride film layer is 97.51 nm.

3. The ultra-low residual reflectivity optical antireflection film according to claim 1, characterized in that: The thickness of the first lanthanum titanate film layer is 15.08 nm, the thickness of the second lanthanum titanate film layer is 18.01 nm, the thickness of the third lanthanum titanate film layer is 112.63 nm, the thickness of the fourth lanthanum titanate film layer is 15.00 nm, the thickness of the fifth lanthanum titanate film layer is 43.46 nm, and the thickness of the sixth lanthanum titanate film layer is 61.49 nm.

4. The ultra-low residual reflectivity optical antireflection film according to claim 1, characterized in that: The refractive index of the magnesium fluoride film layer is 1.364-1.

384.

5. The ultra-low residual reflectivity optical antireflection film according to claim 4, characterized in that: The refractive index of the magnesium fluoride film layer is 1.

374.

6. The ultra-low residual reflectivity optical antireflection film according to claim 1, characterized in that: The refractive index of the lanthanum titanate film layer is 2.054-2.

074.

7. The ultra-low residual reflectivity optical antireflection film according to claim 6, characterized in that: The refractive index of the lanthanum titanate film layer is 2.064.

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