Optical filter and preparation method thereof

Abstract

The present invention relates to an optical filter and a preparation method thereof. The optical filter comprises a substrate (1) and a bandpass film (2) and an anti-reflection film (3) arranged on both sides of the substrate (1). The bandpass film (2) and the anti-reflection film (3) are both formed by alternating high and low refractive index film layers. The optical filter has a transmittance of more than 95% in a wavelength band of 1000nm to 2000nm at an incident angle of 0° to 50°. The optical filter of the present invention can achieve a high transmittance in the wavelength band of 1000nm to 2000nm at an incident angle of 0° to 50°.

Description

Technical Field

[0001] The invention relates to a filter and a preparation method thereof. Background Art

[0002] With the development of science and technology, laser detection technology has been widely used in distance detection, biometrics, and various industrial production. Therefore, the requirements for laser anti-interference capabilities are becoming increasingly higher. According to the principle of laser detection, as the laser detection wavelength redshifts, the laser's anti-interference ability can be effectively improved. However, in the existing technology, infrared laser products near the 940nm band cannot meet the requirements of high anti-interference capabilities. In addition, the long shift of the laser band will inevitably lead to an increase in film thickness, which will in turn cause greater stress in the film layer, making the lens surface more susceptible to distortion. When light passes through a distorted surface, reflection loss will occur. The energy value of the reflection loss is closely related to the amount of surface distortion. That is, the greater the distortion, the greater the energy loss, which will seriously reduce the transmittance of the product. It can be seen that the above-mentioned defects of the existing technology have placed higher requirements on infrared laser products with longer wavelengths. Summary of the Invention

[0003] The object of the present invention is to provide a filter and a preparation method thereof.

[0004] To achieve the above-mentioned purpose of the invention, the present invention provides a filter and a preparation method thereof. The filter includes a substrate and a bandpass film and an anti-reflection film arranged on both sides of the substrate. The bandpass film and the anti-reflection film are both formed by alternating high and low refractive index film layers.

[0005] According to one aspect of the present invention, the refractive index of the material of the high refractive index film layer is greater than 2.0, and the refractive index of the material of the low refractive index film layer is less than 2.0.

[0006] According to one aspect of the present invention, the material of the high refractive index film layer in the bandpass film includes germanium oxide, titanium oxide, niobium oxide, tantalum oxide, lanthanum oxide, silicon hydride, titanium hydride, germanium hydride, niobium hydride, tantalum hydride, lanthanum hydride, silicon nitride, germanium nitride, titanium nitride, niobium nitride, tantalum nitride, lanthanum nitride, hydrogenated silicon nitride, hydrogenated germanium nitride, hydrogenated titanium nitride, hydrogenated niobium nitride, hydrogenated tantalum nitride, and hydrogenated lanthanum nitride;

[0007] The material of the low refractive index film layer in the bandpass film includes silicon oxide, magnesium fluoride, and cryolite.

[0008] According to one aspect of the present invention, the material of the high refractive index film layer in the antireflection film includes titanium oxide, niobium oxide, tantalum oxide, lanthanum oxide, hafnium oxide, zirconium oxide, and germanium oxide;

[0009] The material of the low refractive index film layer in the antireflection film includes aluminum oxide, magnesium oxide, silicon oxide, magnesium fluoride, lanthanum fluoride, and aluminum fluoride.

[0010] According to one aspect of the present invention, the thickness of the bandpass film is between 10,000 nm and 20,000 nm, and the thickness of the antireflection film is between 10,000 nm and 20,000 nm.

[0011] According to one aspect of the present invention, the ratio of the thickness of the bandpass film to the thickness of the antireflection film is between 1:1 and 1:1.8.

[0012] According to one aspect of the present invention, the bandpass film has 15-30 pairs of high and low refractive index film layers;

[0013] The antireflection film has 20-50 pairs of high and low refractive index film layers.

[0014] According to one aspect of the present invention, the transmittance of the filter in the wavelength range of 1000nm-2000nm is above 95% at an incident angle of 0°-50°.

[0015] According to one aspect of the present invention, the surface PV value of the filter is less than 20 microns within a diameter of 17 mm.

[0016] A method for preparing an optical filter comprises sequentially coating a bandpass film and an anti-reflection film on a substrate, wherein the anti-reflection film is coated in an environment above 150°C. The first layer must be made of silicon dioxide material, and the coating ion source power is higher than that of the remaining silicon dioxide layers, being 1.5 times that of the remaining layers; and the coating rate is lower than that of the remaining silicon dioxide layers, being approximately 0.8 times that of the remaining layers.

[0017] According to the present invention, through the rational selection of coating materials and film thickness, the filter achieves high transmittance within the 1000nm-2000nm wavelength range and at wide angles of incidence ranging from 0° to 50°. Furthermore, the PV value of the lens surface within a 17mm diameter range is guaranteed to be less than 20 microns.

[0018] According to the solution of the present invention, the ratio of the thickness of the bandpass film to the thickness of the antireflection film satisfies a certain relationship, thereby achieving better stress balance.

[0019] According to the solution of the present invention, when manufacturing the filter, the bandpass film with greater stress is deposited first, and then the anti-reflection film is deposited. The anti-reflection film is deposited in a high temperature environment, thereby effectively eliminating the stress of the film layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A diagram schematically showing the structure of an optical filter according to an embodiment of the present invention;

[0021] Figure 2Schematically showing the spectrum of the filter in the 1300nm band according to one embodiment of the present invention;

[0022] Figure 3 Schematic diagram showing the spectrum of a filter in the 1550 nm band according to one embodiment of the present invention;

[0023] Figure 4 The figure schematically shows the spectrum of the filter in the 1800nm band according to one embodiment of the present invention. DETAILED DESCRIPTION

[0024] 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 the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0025] When describing the embodiments of the present invention, the orientation or positional relationship expressed by the terms "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or positional relationship shown in the relevant drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.

[0026] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The embodiments cannot be described one by one here, but the embodiments of the present invention are not limited to the following embodiments.

[0027] See also Figure 1 The (bandpass) filter of the present invention comprises a substrate 1, and a bandpass film 2 and an antireflection film 3 disposed on either side of the substrate 1. Both the bandpass film 2 and the antireflection film 3 are formed by alternating high and low refractive index layers. The high refractive index layer has a refractive index greater than 2.0, while the low refractive index layer has a refractive index less than 2.0. In the present invention, the bandpass film 2 has 15-30 pairs of high and low refractive index layers, and the antireflection film 3 has 20-50 pairs of high and low refractive index layers.

[0028] In the present invention, the material of the high refractive index film layer in the bandpass film 2 can be a metal, a semiconductor, and all or part of its oxides, nitrides, hydrides, hydroxides, and oxynitrides. For example, the material can be one or more mixtures of germanium oxide, titanium oxide, niobium oxide, tantalum oxide, lanthanum oxide, silicon hydride, titanium hydride, germanium hydride, niobium hydride, tantalum hydride, lanthanum hydride, silicon nitride, germanium nitride, titanium nitride, niobium nitride, tantalum nitride, lanthanum nitride, hydrogenated silicon nitride, hydrogenated germanium nitride, hydrogenated titanium nitride, hydrogenated niobium nitride, tantalum nitride, and hydrogenated lanthanum nitride (for example, a mixture of titanium oxide and lanthanum oxide, or a mixture of lanthanum oxide and aluminum oxide). The material of the low refractive index film layer in the bandpass film 2 includes one or more mixtures of silicon oxide, magnesium fluoride, and cryolite. Therefore, the selection of these materials can enable the filter to achieve high transmittance under large-angle incidence within a certain wavelength band.

[0029] The high-refractive-index layer in the antireflection coating 3 is made of a metal oxide, such as titanium oxide, niobium oxide, tantalum oxide, lanthanum oxide, hafnium oxide, zirconium oxide, or germanium oxide, or a mixture thereof. The low-refractive-index layer in the antireflection coating 3 is made of aluminum oxide, magnesium oxide, silicon oxide, magnesium fluoride, lanthanum fluoride, or aluminum fluoride, or a mixture thereof. The aforementioned low-refractive-index layer materials can also be mixed with the high-refractive-index layer materials to form other mixtures.

[0030] Of course, in the bandpass film 2 and the anti-reflection film 3 , the materials of the high refractive index film layer and the low refractive index film layer are not limited to the one mentioned above, and film layers of multiple materials can also be selected to form various film systems.

[0031] In the present invention, the thickness of the bandpass film 2 is between 10,000 nm and 20,000 nm, and the thickness of the antireflection film 3 is between 10,000 nm and 20,000 nm. Furthermore, as the thickness of the antireflection film 3 increases, the stresses on both sides of the substrate 1 gradually become relatively balanced. Therefore, the present invention sets the thickness ratio of the bandpass film 2 to the antireflection film 3 between 1:1 and 1:1.8 to achieve stress balance.

[0032] The following describes the filter of the present invention in detail using three different wavelength band implementations:

[0033] First implementation method

[0034] Combine Figure 2 The composition of the bandpass film 2 and the antireflection film 3 in the optical filter of this embodiment is shown in Table 1 below:

[0035]

[0036]

[0037]

[0038] Table 1

[0039] Second implementation method

[0040] Combine Figure 3 The composition of the bandpass film 2 and the antireflection film 3 in the optical filter of this embodiment is shown in Table 2 below:

[0041]

[0042]

[0043]

[0044] Table 2

[0045] Third implementation method

[0046] Combine Figure 4 The composition of the bandpass film 2 and the antireflection film 3 in the optical filter of this embodiment is shown in Table 3 below:

[0047]

[0048]

[0049] Table 3

[0050] In the optical filter manufacturing method of the present invention, a bandpass film 2 is first deposited on one side of a substrate 1, and then an antireflection film 3 is deposited on the other side of the substrate 1. Furthermore, the deposition of the antireflection film 3 should be performed at a high temperature of 150°C or higher. This allows the already formed bandpass film 2 to be baked simultaneously to release stress while the antireflection film 3 is being deposited, and the stress of the antireflection film 3 can be gradually balanced against that of the bandpass film 2. Furthermore, during deposition, the first layer must be made of silicon dioxide, and the ion source power for its deposition should be approximately 1.5 times higher than that of the remaining silicon dioxide layers, while the deposition rate should be approximately 0.8 times lower than that of the remaining silicon dioxide layers.

[0051] Meeting these requirements allows the filter to achieve a transmittance of over 95% within any near-infrared wavelength range of 1000nm to 2000nm at an incident angle of 0° to 50°. Combined with the filter's unique structural design, the filter's surface PV value can be reduced to less than 20 microns within a 17mm diameter.

[0052] The above description is merely one embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A filter, characterized in that: The invention comprises a substrate (1) and a bandpass film (2) and an antireflection film (3) arranged on both sides of the substrate (1); the bandpass film (2) and the antireflection film (3) are both formed by alternating high and low refractive index film layers; when coating, the bandpass film (2) is first coated on one side of the substrate (1), and then the antireflection film (3) is coated on the other side of the substrate (1); The filter has a transmittance of more than 95% in the 1000nm-2000nm band at an incident angle of 0°-50°; The ratio of the thickness of the bandpass film (2) to the thickness of the antireflection film (3) is between 1:1 and 1:1.8; The antireflection film (2) is plated in an environment above 150° C., and the first layer is made of silicon dioxide material, the ion source power of the coating is 1.5 times that of the remaining silicon dioxide layers, and the coating rate is 0.8 times that of the remaining silicon dioxide layers; The surface PV value of the filter is less than 20 microns within a diameter of 17 mm.

2. The optical filter according to claim 1, wherein The refractive index of the material of the high refractive index film layer is greater than 2.0, and the refractive index of the material of the low refractive index film layer is less than 2.

0.

3. The optical filter according to claim 2, wherein: The material of the high refractive index film layer in the bandpass film (2) includes germanium oxide, titanium oxide, niobium oxide, tantalum oxide, lanthanum oxide, silicon hydride, titanium hydride, germanium hydride, niobium hydride, tantalum hydride, lanthanum hydride, silicon nitride, germanium nitride, titanium nitride, niobium nitride, tantalum nitride, lanthanum nitride, hydrogenated silicon nitride, hydrogenated germanium nitride, hydrogenated titanium nitride, hydrogenated niobium nitride, hydrogenated tantalum nitride, and hydrogenated lanthanum nitride; The material of the low refractive index film layer in the bandpass film (2) includes silicon oxide, magnesium fluoride, and cryolite.

4. The optical filter according to claim 2, wherein: The material of the high refractive index film layer in the antireflection film (3) includes titanium oxide, niobium oxide, tantalum oxide, lanthanum oxide, hafnium oxide, zirconium oxide, and germanium oxide; The material of the low refractive index film layer in the antireflection film (3) includes aluminum oxide, magnesium oxide, silicon oxide, magnesium fluoride, lanthanum fluoride, and aluminum fluoride.

5. The optical filter according to claim 1, wherein: The thickness of the bandpass film (2) is between 10,000 nm and 20,000 nm, and the thickness of the antireflection film (3) is between 10,000 nm and 20,000 nm.

6. A method for preparing the optical filter according to claim 1-5, characterized in that: A bandpass film (2) and an anti-reflection film (3) are sequentially plated on a substrate (1), and the anti-reflection film (3) is plated in an environment above 150°C.

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