Linearly graded filter film structure and method of making same

Abstract

The application relates to the technical field of spectral optical elements, and provides a linear gradient filter film structure and a preparation method thereof.The linear gradient filter film structure comprises a quartz glass substrate, a first near-infrared region layer plated on the quartz glass substrate, a first transition film layer deposited on the first near-infrared region layer, a second near-infrared region layer plated on the first transition film layer, a second transition film layer deposited on the second near-infrared region layer, a third near-infrared region layer plated on the second transition film layer, a separation layer deposited on the third near-infrared region layer, and an anti-scratch layer deposited on the separation layer; the quartz glass substrate, the first near-infrared region layer, the first transition film layer and the second near-infrared region layer have equal widths; the second transition film layer, the third near-infrared region layer, the separation layer and the anti-scratch layer have equal widths; and the width of the second near-infrared region layer is smaller than the width of the second transition film layer to form a stepped structure.The application realizes full coverage and stability of spectral detection in the 900nm-2500nm wave band.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of spectral optical elements, and particularly relates to a linear variable filter diaphragm structure and a preparation method thereof. BACKGROUND

[0002] As a kind of spectral element that spectrum varies linearly with position, linear variable filter (LVF) has become a key device for obtaining spectral information in the field of multispectral imaging due to its inherent characteristics of lightweight and continuous spectral splitting. In recent years, with the application of short-wave infrared band (900nm~2500nm) spectral detection technology in the fields of agriculture, environment, food detection and medical diagnosis, etc.

[0003] However, the current near-infrared LVF diaphragm mainly focuses on the 1000-1800nm band, and there are three major bottlenecks: the existing LVF adopts "single film system + fixed thickness gradient", which can only cover 900-2000nm, and cannot be extended to the 2000-2500nm near-infrared region; because the region has high requirements on the infrared transmittance of the film system material (≥85%), the transmittance of the traditional SiO2 / TiO2 film system drops sharply (<60%) above 2000nm, which cannot meet the spectral splitting requirements.

[0004] Therefore, the current near-infrared LVF diaphragm has small covered band, low transmittance and poor uniformity. SUMMARY

[0005] In view of the above problems of the prior art, the present application provides a linear variable filter diaphragm structure to solve the problems of small covered band, low transmittance and poor uniformity of the existing linear variable filter diaphragm structure.

[0006] To solve the above technical problems, the present application adopts the following technical solutions:

[0007] In a first aspect, an embodiment of the present application provides a linearly graded filter film structure, which comprises a quartz glass substrate, a first near-infrared region layer formed by coating on the quartz glass substrate, a first transition film layer deposited on the first near-infrared region layer, a second near-infrared region layer formed by coating on the first transition film layer, a second transition film layer deposited on the second near-infrared region layer, a third near-infrared region layer formed by coating on the second transition film layer, a separation layer deposited on the third near-infrared region layer, and a scratch-resistant layer deposited on the separation layer; the quartz glass substrate, the first near-infrared region layer, the first transition film layer, and the second near-infrared region layer have equal widths; the second transition film layer, the third near-infrared region layer, the separation layer, and the scratch-resistant layer have equal widths; the width of the second near-infrared region layer is less than the width of the second transition film layer to form a stepped structure.

[0008] The quartz glass substrate is used to support the first near-infrared region layer.

[0009] The first near-infrared region layer is used to transmit incident light sources with wavelengths of 900 nm to 1400 nm.

[0010] The first transition film layer is used to realize fixed connection between the first near-infrared region layer and the second near-infrared region layer.

[0011] The second near-infrared region layer is used to transmit incident light sources with wavelengths of 1400 nm to 2000 nm.

[0012] The second transition film layer is used to realize fixed connection between the second near-infrared region layer and the third near-infrared region layer.

[0013] The third near-infrared region layer is used to transmit incident light sources with wavelengths of 2000 nm to 2500 nm.

[0014] The separation layer is used to realize regional optical isolation of the first near-infrared region layer, the second near-infrared region layer, and the third near-infrared region layer.

[0015] The scratch-resistant layer is used to protect the separation layer.

[0016] Preferably, the first near-infrared region layer is formed by alternately stacking silica and zinc sulfide materials; the second near-infrared region layer is formed by alternately stacking silica and germanium materials; and the third near-infrared region layer is formed by alternately stacking aluminum oxide and germanium materials.

[0017] Preferably, the initial film thickness of the first near-infrared region layer is 100-150 nm, the gradient increment is 10-18 nm, and the number of film layers is 6-8 pairs; wherein the number of film layers is the number of repetitions of the alternately stacked silicon dioxide and zinc sulfide materials.

[0018] Preferably, the initial film thickness of the second near-infrared region layer is 150-200 nm, the gradient increment is 20-25 nm, and the number of film layers is 8-10 pairs; wherein the number of film layers is the number of repetitions of the alternately stacked silicon dioxide and germanium materials.

[0019] Preferably, the initial film thickness of the third near-infrared region layer is 250-280 nm, the gradient increment is 28-32 nm, and the number of film layers is 10-12 pairs; wherein the number of film layers is the number of repetitions of the alternately stacked aluminum oxide and germanium materials.

[0020] Preferably, the thickness of the first transition film layer is 50-60 nm, and the roughness is ≤0.4 nm.

[0021] Preferably, the thickness of the second transition film layer is 50-60 nm, and the roughness is ≤0.4 nm.

[0022] Preferably, the film plating is performed by electron beam evaporation and ion-assisted deposition.

[0023] Preferably, among the quartz glass substrate, the first near-infrared region layer, the first transition film layer, the second near-infrared region layer, the second transition film layer, the third near-infrared region layer, the separation layer, and the scratch-resistant layer, the thickness of each film increases linearly in the direction from the quartz glass substrate to the scratch-resistant layer, and when the incident light source passes through different thickness film layers, the following relationship is satisfied:

[0024] 2nd = (m+1 / 2)λ;

[0025] wherein n is the refractive index of the current film layer, d is the film thickness of the current film layer, m is an integer, and λ is the wavelength of the current film layer.

[0026] In a second aspect, an embodiment of the present application provides a preparation method of the linearly graded filter film structure as described above, which comprises the following steps:

[0027] The quartz glass substrate is sequentially subjected to cleaning, plasma activation treatment, and silane coupling agent coating treatment; wherein the cleaning is performed by ultrasonic cleaning or ethanol and deionized water cleaning, and the cleaning time is 10-20 min; the plasma activation treatment is performed at a power of 200-300 W for 2-10 min; the concentration of the silane coupling agent is 1%-5%, and the drying temperature after coating is 70°C-100°C.

[0028] A first near-infrared region layer is deposited on the quartz glass substrate by electron beam evaporation, wherein the vacuum degree of the electron beam evaporation is ≤5*10 -4 The 8 logarithmic film layers are deposited at an evaporation rate of 0.5-1 nm / s, an initial film thickness of 150 nm, and a gradient increment of 18 nm;

[0029] A first transition film layer is deposited on the first near-infrared region layer by ion-assisted deposition, wherein the power of the ion-assisted deposition is 80-100 W, and the roughness is ≤0.3 nm;

[0030] A second near-infrared region layer is deposited on the first transition film layer by the electron beam evaporation, wherein the 10 logarithmic film layers are deposited at an initial film thickness of 200 nm and a gradient increment of 25 nm;

[0031] A second transition film layer is deposited on the second near-infrared region layer by the ion-assisted deposition, wherein the power of the ion-assisted deposition is 80-100 W, and the roughness is ≤0.4 nm;

[0032] A third near-infrared region layer is deposited on the second transition film layer by the electron beam evaporation, wherein the 12 logarithmic film layers are deposited at an initial film thickness of 280 nm and a gradient increment of 32 nm;

[0033] A separation layer is deposited on the third near-infrared region layer;

[0034] A scratch-resistant layer is coated on the separation layer, and a stress relief annealing treatment is performed to obtain the linearly graded filter film structure.

[0035] Compared with the related art, in the embodiment of the present application, by sequentially stacking the first near-infrared region layer, the first transition film layer, the second near-infrared region layer, the second transition film layer, the third near-infrared region layer, the separation layer and the scratch-resistant layer on the quartz glass substrate, the widths of the quartz glass substrate, the first near-infrared region layer, the first transition film layer and the second near-infrared region layer are equal; the widths of the second transition film layer, the third near-infrared region layer, the separation layer and the scratch-resistant layer are equal; the width of the second near-infrared region layer is smaller than the width of the second transition film layer to form a stepped structure; the first near-infrared region layer is used for transmitting an incident light source with a wavelength of 900-1400 nm; the first transition film layer is used to realize fixed connection between the first near-infrared region layer and the second near-infrared region layer; the second near-infrared region layer is used for transmitting an incident light source with a wavelength of 1400-2000 nm; the second transition film layer is used to realize fixed connection between the second near-infrared region layer and the third near-infrared region layer; the third near-infrared region layer is used for transmitting an incident light source with a wavelength of 2000-2500 nm; the separation layer is used to realize regional optical isolation of the first near-infrared region layer, the second near-infrared region layer and the third near-infrared region layer; and the scratch-resistant layer is used to protect the separation layer. In this way, 900-2500 nm full-band coverage can be realized, covering the first to third near-infrared regions, without missing any band, and adapting to the spectral detection requirements of multiple scenes; the full-band transmittance is greater than or equal to 90%, the transmittance fluctuation in the same band is less than or equal to 5%, the spectral signal intensity is stable, and the transmittance and uniformity are improved; the spectral drift is less than or equal to 0.3 nm / ℃ within the range of-20-60℃, the film layer adhesion grade is greater than or equal to 2B, the grid test has no falling off, the temperature drift is reduced, and the stability is improved; the roughness is less than or equal to 0.4 nm, the separation layer can reduce spectral crosstalk, and the spectral purity is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0036] The present application will be described in detail below with reference to the accompanying drawings. The above or other aspects of the present application will become more apparent and more readily appreciated by referring to the following detailed description, taken in conjunction with the accompanying drawings. In the drawings:

[0037] Figure 1 A perspective structural schematic diagram of a linear gradient filter film structure provided by the embodiment of the present application;

[0038] Figure 2 A flowchart of a preparation method of a linear gradient filter film structure provided by the embodiment of the present application.

[0039] In the drawings: 100, linear gradient filter film structure, 1, quartz glass substrate, 2, first near-infrared region layer, 3, first transition film layer, 4, second near-infrared region layer, 5, second transition film layer, 6, third near-infrared region layer, 7, separation layer, 8, scratch-resistant layer. DETAILED DESCRIPTION

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting upon the application; the description herein and the claims and the above description of the drawings are not intended to be limiting upon the application; the terms "comprising," "having," and "including" and any variations thereof used in the specification and in the claims are intended to cover not exclusive inclusions; the terms "first," "second," and the like used in the specification and the claims are not intended to denote a particular order or sequence.

[0041] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase that in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. As will be apparent to those of ordinary skill in the art upon reading this description, the embodiments described herein can be combinable with other embodiments.

[0042] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without any creative effort belong to the scope of protection of the present application.

[0043] Embodiment one

[0044] Please refer to Figure 1As shown, the embodiment of the present application provides a linear gradient filter film structure 100, which comprises a quartz glass substrate 1, a first near-infrared region layer 2 formed by coating on the quartz glass substrate 1, a first transition film layer 3 deposited on the first near-infrared region layer 2, a second near-infrared region layer 4 formed by coating on the first transition film layer 3, a second transition film layer 5 deposited on the second near-infrared region layer 4, a third near-infrared region layer 6 formed by coating on the second transition film layer 5, a separation layer 7 deposited on the third near-infrared region layer 6, and a scratch-resistant layer 8 deposited on the separation layer 7; the quartz glass substrate 1, the first near-infrared region layer 2, the first transition film layer 3 and the second near-infrared region layer 4 have equal widths; the second transition film layer 5, the third near-infrared region layer 6, the separation layer 7 and the scratch-resistant layer 8 have equal widths; the width of the second near-infrared region layer 4 is less than the width of the second transition film layer 5 to form a stepped structure. The quartz glass substrate 1 is selected from high-purity quartz glass (thickness 0.3 mm, transmittance ≥93% at 900-2500 nm), which ensures that the substrate has no absorption. Optionally, the length direction of the quartz glass substrate 1 is the X axis, the width direction is the Y axis, and the thickness direction is the Z axis. The thickness of each film layer of the linear gradient filter film structure 100 increases linearly along the Z axis direction.

[0045] The quartz glass substrate 1 is used to support the first near-infrared region layer 2.

[0046] The first near-infrared region layer 2 is used to transmit incident light sources with wavelengths of 900-1400 nm. The transmittance is ≥93%.

[0047] The first transition film layer 3 is used to realize the fixed connection between the first near-infrared region layer 2 and the second near-infrared region layer 4.

[0048] The second near-infrared region layer 4 is used to transmit incident light sources with wavelengths of 1400-2000 nm. The transmittance is ≥88%, and the refractive index is high (4.0), which enhances the contrast of light splitting.

[0049] The second transition film layer 5 is used to realize the fixed connection between the second near-infrared region layer 4 and the third near-infrared region layer 6.

[0050] The third near-infrared region layer 6 is used to transmit incident light sources with wavelengths of 2000-2500 nm. The transmittance is ≥92%.

[0051] The separation layer 7 is used to realize regional optical isolation of the first near-infrared region layer 2, the second near-infrared region layer 4 and the third near-infrared region layer 6. The scratch-resistant layer 8 is used to protect the separation layer 7. By being divided into three independent sub-band regions along the length direction of the film, such as the first near-infrared region layer 2, the second near-infrared region layer 4 and the third near-infrared region layer 6, each region uses different film system materials and thickness gradient to realize continuous light splitting of 900-2500nm, and the regions are connected through the corresponding first transition film layer 3 and the connection to avoid band breakage. The scratch-resistant layer 8 protects the film system, the quartz glass substrate 1 ensures the support strength, and the overall structure is suitable for small-sized installation.

[0052] Specifically, this can realize 900-2500nm full-band coverage, covering the first near-infrared region layer 2 to the third near-infrared region layer 6, without band loss, and adapt to multi-scene spectral detection requirements; the full-band transmittance is ≥90%, the transmittance fluctuation in the same band is ≤5%, which ensures the stability of the spectral signal intensity and improves the transmittance and uniformity; the spectral drift is ≤0.3nm / ℃ within the range of-20~60℃, the film layer adhesion grade is ≥2B, the grid test has no falling, and the temperature drift is reduced and the stability is improved; the separation layer can reduce spectral crosstalk and ensure the purity of light splitting.

[0053] In the embodiment, the first near-infrared region layer 2 is formed by alternately stacking silica (SiO2) and zinc sulfide (ZnS) materials; the second near-infrared region layer 4 is formed by alternately stacking silica and germanium (Ge) materials; and the third near-infrared region layer 6 is formed by alternately stacking aluminum oxide (Al2O3) and germanium materials. Optionally, the first transition film layer 3 is made of silica material, and the second transition film layer 5 is made of aluminum oxide material. The separation layer 7 and the scratch-resistant layer 8 are both made of silica, and the thickness is 30nm.

[0054] Among them, the low refractive index material: SiO2(n=1.46, 900~2500nm transmittance ≥95%), Al2O3(n=1.76, 2000~2500nm transmittance ≥92%). High refractive index material: Ge (n=4.0, 1400-2500nm transmittance ≥88%), ZnS (n=2.35, 900~1800nm transmittance ≥93%). Wherein, n is the refractive index.

[0055] Among them, the material with matching thermal expansion coefficient (SiO2 thermal expansion coefficient 5.5×10 -7 / ℃, Ge 6.1×10 -6 / ℃) is selected, the influence of thermal expansion and contraction is offset by film system combination, so as to realize temperature drift control.

[0056] In this embodiment, the initial film thickness of the first near-infrared region layer 2 is 100-150 nm, the gradient increment is 10-18 nm, and the film layer pair number is 6-8 pairs; wherein the film layer pair number is the number of repetitions of the alternately stacked silicon dioxide and zinc sulfide materials.

[0057] Specifically, the initial film thickness t0 of the first near-infrared region layer 2 is 150 nm, the gradient increment Δt1 is 10-18 nm, and the film layer pair number is 8 pairs. Optionally, the gradient increment unit "nm" directly reflects that "for every 1 mm of spatial distance, the film thickness increases by 18 nm"; the initial film thickness refers to the reference thickness when the first functional film (here, SiO2 or ZnS) in the film system starts to deposit, which is the starting point for subsequent film thickness adjustment.

[0058] In this embodiment, the initial film thickness of the second near-infrared region layer 4 is 150-200 nm, the gradient increment is 20-25 nm, and the film layer pair number is 8-10 pairs; wherein the film layer pair number is the number of repetitions of the alternately stacked silicon dioxide and germanium materials.

[0059] Specifically, the initial film thickness t0 of the second near-infrared region layer 4 is 200 nm, the gradient increment Δt2 is 25 nm, and the film layer pair number is 10 pairs.

[0060] In this embodiment, the initial film thickness of the third near-infrared region layer 6 is 250-280 nm, the gradient increment is 28-32 nm, and the film layer pair number is 10-12 pairs; wherein the film layer pair number is the number of repetitions of the alternately stacked aluminum oxide and germanium materials. The film layer pair number refers to the number of repetitions of "low refractive index layer + high refractive index layer", and the more the number, the more stable the transmittance.

[0061] Specifically, the initial film thickness of the third near-infrared region layer 6 is 280 nm, the gradient increment Δt3 is 32 nm, and the film layer pair number is 12 pairs.

[0062] In this embodiment, the thickness of the first transition film layer 3 is 50-60 nm, and the roughness is ≤0.4 nm. Specifically, the thickness of the first transition film layer 3 is 50 nm, and the roughness is 0.3 nm. Covering 900-1400 nm wavelength.

[0063] In this embodiment, the thickness of the second transition film layer 5 is 50-60 nm, and the roughness is ≤0.4 nm. Specifically, the thickness of the second transition film layer 5 is 60 nm, and the roughness is 0.4 nm, covering 1400-2000 nm wavelength. The "thin high refractive index layer" design (Ge layer thickness ≤50 nm) is adopted to reduce the total thickness; the thickness of the first transition film layer 3 and the second transition film layer 5 is controlled to be 50-60 nm to avoid additional thickening.

[0064] Specifically, the transition film layer of adjacent regions is designed with a "gradual refractive index" (e.g., the refractive index of SiO2→Al2O3 is gradually changed from 1.46 to 1.76), so as to reduce the crosstalk caused by interface reflection.

[0065] In this embodiment, the film is plated by electron beam evaporation and ion-assisted deposition. Electron beam evaporation is a technology that uses high-energy electron beams to bombard the target material, causing it to evaporate and form a film on the substrate surface. The electron beam directly heats the target material, reducing impurities caused by the evaporation of crucible materials, and is suitable for optical films. It can improve the purity of the film layer. By controlling the electron beam scanning range and evaporation rate, a thin film with uniform thickness can be formed on a large-area substrate, ensuring film uniformity.

[0066] Ion-assisted deposition (IAD) is a composite technology that uses high-energy ions to bombard the growing thin film while evaporating the film. The specific workflow is as follows:

[0067] Based on electron beam evaporation (or resistance evaporation), an ion source is additionally added. The ion source generates inert gas ions (such as argon ions) or reactive ions (such as oxygen ions), which bombard the substrate surface and the newly formed thin film at high speed. The ion energy is usually several hundred to several thousand electron volts, and the bombardment angle and intensity can be adjusted, and the process is synchronized with the evaporation process. It can improve the density of the thin film, enhance the adhesion between the film and the substrate, and reduce the internal stress of the thin film.

[0068] By using the "electron beam evaporation + ion-assisted deposition" process, the film layer density is ≥98%, reducing light scattering caused by pores. The logarithmic optimization of each region film system balances the transmittance and thickness, allowing the overall transmittance to be improved.

[0069] In this embodiment, among the quartz glass substrate 1, the first near-infrared region layer 2, the first transition film layer 3, the second near-infrared region layer 4, the second transition film layer 5, the third near-infrared region layer 6, the separation layer 7, and the scratch-resistant layer 8, the thickness of each film increases linearly in the direction from the quartz glass substrate 1 to the scratch-resistant layer 8. When the incident light source passes through different thickness film layers, the following relationship is satisfied:

[0070] 2nd=(m+1 / 2)λ;

[0071] Where n is the refractive index of the current film layer, d is the film thickness of the current film layer, m is an integer, and λ is the wavelength of the current film layer.

[0072] Specifically, the film thickness of each region linearly increases along the length direction (for example, the first near-infrared region layer 2 increases from 150 nm to 330 nm), and when the incident light passes through the film layers of different thicknesses, only specific wavelengths meet the interference constructive condition of "2nd=(m+1 / 2) lambda", realizing continuous light splitting of 900 nm-2500 nm, and the half-wave width is controlled within 20-30 nm, meeting the spectral resolution requirement. The interference constructive refers to the phenomenon that when two coherent waves are superimposed, the vibration directions are the same and the phase difference is constant, and finally the vibration is strengthened. When two coherent waves (same frequency, consistent vibration direction, constant phase difference) meet, if their vibration directions are the same at a certain point and the phase difference is an integer multiple (such as 0, 2pi, 4pi...) of 2pi, the combined vibration amplitude at the point will be equal to the sum of the amplitudes of the two waves, and this superposition effect is "interference constructive".

[0073] The beneficial effects of the present application are as follows:

[0074] Full-waveband coverage, strong scene adaptability: 900-2500 nm covers the first near-infrared region layer 2, the second near-infrared region layer 4 and the third near-infrared region layer 6, and there is no waveband missing, which can simultaneously meet the requirements of environmental monitoring (900-1700 nm), food detection (2000-2500 nm) and medical diagnosis (1400-2000 nm), and the scene is expanded by more than 3 times compared with the existing scheme (only covering <2000 nm).

[0075] High transmittance and uniformity: full-waveband transmittance is greater than or equal to 90% (region 1 is greater than or equal to 92%, region 2 is greater than or equal to 91%, and region 3 is greater than or equal to 90%), and the transmittance fluctuation in the same waveband is less than or equal to 5%, which is 15% higher in spectral signal intensity and 50% higher in stability compared with the existing scheme (transmittance <85%, fluctuation >10%).

[0076] Low temperature drift and high stability: the spectral drift is less than or equal to 0.3 nm / ℃ within the range of -20-60℃, the film layer adhesion grade is greater than or equal to 2B (no falling off in grid test), and it is suitable for complex environments such as outdoor and low temperature.

[0077] Small size integration advantage: the total thickness is less than or equal to 0.8 mm (substrate 0.3 mm + film layer 0.3-0.5 mm), which is 11% thinner than the existing LVF (thickness >0.9 mm) covering 1500-2000 nm, and can be directly integrated into small devices such as mobile spectrum modules and portable detectors.

[0078] Low crosstalk and high light splitting purity: the film layer interface roughness is less than or equal to 0.5 nm, and the adjacent waveband crosstalk rate is less than or equal to 3%, which avoids stray light interference with the detection result.

[0079] Controllable mass production cost: mature electron beam evaporation + ion assisted deposition process is adopted, the single piece preparation time is less than or equal to 2h, the mass production yield is greater than or equal to 90%, and the cost is reduced by 15%.

[0080] Embodiment Two

[0081] Referring to Figure 2 As shown in the above, the embodiment of the present application provides a preparation method of the linear gradient filter film structure 100, the preparation method comprising the following steps:

[0082] S1, the quartz glass substrate 1 is sequentially subjected to cleaning, plasma activation treatment and silane coupling agent coating treatment; wherein the cleaning mode is ultrasonic cleaning or ethanol and deionized water cleaning, and the cleaning time is 10-20 min; the power of the plasma activation treatment is 200-300 W, and the time is 2-10 min; the concentration of the silane coupling agent is 1%-5%, and the drying temperature after coating is 70-100 DEG C. Specifically, the ultrasonic cleaning or ethanol and deionized water cleaning is performed for 15 min; the power of the plasma activation treatment is 200 W, and the time is 5 min; the concentration of the silane coupling agent is 1%, and the drying temperature after coating is 80 DEG C.

[0083] S2, a first near-infrared region layer 2 is obtained by electron beam evaporation on the quartz glass substrate 1; wherein the vacuum degree of the electron beam evaporation is ≤5*10 -4 Pa, the evaporation rate is 0.5-1 nm / s, 8 film layer logs are deposited according to the initial film thickness of 150 nm and the gradient increment of 18 nm. Specifically, the evaporation rate of the electron beam evaporation is 1 nm / s, and 8 film layer logs are deposited according to the initial film thickness of 150 nm and the gradient increment of 18 nm.

[0084] S3, a first transition film layer 3 is deposited on the first near-infrared region layer 2 by ion assisted deposition; wherein the power of the ion assisted deposition is 80-100 W, and the roughness is ≤0.3 nm. Specifically, the power of the ion assisted deposition is 100 W.

[0085] S4, a second near-infrared region layer 4 is obtained by electron beam evaporation on the first transition film layer 3; wherein 10 film layer logs are deposited according to the initial film thickness of 200 nm and the gradient increment of 25 nm.

[0086] S5, a second transition film layer 5 is deposited on the second near-infrared region layer 4 by the ion assisted deposition; wherein the power of the ion assisted deposition is 80-100 W, and the roughness is ≤0.4 nm.

[0087] S6, a third near-infrared region layer 6 is obtained by electron beam evaporation on the second transition film layer 5; wherein 12 film layer logs are deposited according to the initial film thickness of 280 nm and the gradient increment of 32 nm.

[0088] S7, depositing a separation layer 7 on the third near-infrared region layer 6. The separation layer 7 is deposited by electron beam evaporation, vacuum degree ≤5×10 -4 Pa, evaporation rate 0.3-0.5 nm / s, thickness ≤30 nm

[0089] S8, coating an anti-scratch layer 8 on the separation layer 7 and performing stress relief annealing treatment to obtain the linearly graded filter film structure 100. Through annealing treatment (temperature 150℃, holding for 2h, slowly cooling to room temperature), the internal stress of the film layer is eliminated; the surface is coated with an anti-scratch layer 8 (SiO2, thickness 30 nm) to improve the wear resistance.

[0090] Specifically, through the above steps S1-S8, the present application can achieve 900-2500nm full-band coverage, covering the first to third near-infrared regions, without missing any waveband, and adapting to the spectral detection needs of multiple scenes; the full-band transmittance is ≥90% under perpendicular incidence, room temperature 23±2℃, relative humidity 45%-55%, the transmittance fluctuation in the same waveband is ≤5%, ensuring the stability of the spectral signal intensity and improving the transmittance and uniformity; the spectral drift is ≤0.3nm / ℃ within the range of-20-60℃, the film adhesion grade is ≥2B, and there is no peeling in the grid test, reducing the temperature drift and improving the stability; the separation layer 7 can reduce spectral crosstalk and ensure the purity of light splitting.

[0091] It should be noted that the above-described various embodiments with reference to the accompanying drawings are only used to illustrate the present application and not to limit the scope of the present application. Those skilled in the art should understand that the modifications or equivalent replacements made to the present application without departing from the spirit and scope of the present application should be covered within the scope of the present application. In addition, unless specifically stated, all or part of any embodiment can be used in combination with all or part of any other embodiment.

Claims

1. A linearly graded filter film structure, characterized by, The linear gradient filter film structure comprises a quartz glass substrate, a first near-infrared region layer formed by coating on the quartz glass substrate, a first transition film layer deposited on the first near-infrared region layer, a second near-infrared region layer formed by coating on the first transition film layer, a second transition film layer deposited on the second near-infrared region layer, a third near-infrared region layer formed by coating on the second transition film layer, a separation layer deposited on the third near-infrared region layer, and a scratch-resistant layer deposited on the separation layer; the quartz glass substrate, the first near-infrared region layer, the first transition film layer, and the second near-infrared region layer have equal widths; the second transition film layer, the third near-infrared region layer, the separation layer, and the scratch-resistant layer have equal widths; the width of the second near-infrared region layer is smaller than the width of the second transition film layer to form a stepped structure; The quartz glass substrate is used to support the first near-infrared region layer; The first near-infrared region layer is used to transmit incident light sources with wavelengths of 900-1400 nm; The first transition film layer is used to realize fixed connection between the first near-infrared region layer and the second near-infrared region layer; The second near-infrared region layer is used to transmit incident light sources with wavelengths of 1400-2000 nm; The second transition film layer is used to realize fixed connection between the second near-infrared region layer and the third near-infrared region layer; The third near-infrared region layer is used to transmit incident light sources with wavelengths of 2000-2500 nm; The separation layer is used to realize regional optical isolation of the first near-infrared region layer, the second near-infrared region layer, and the third near-infrared region layer; The scratch-resistant layer is used to protect the separation layer.

2. The linearly-graded filter film structure of claim 1, wherein, The first near-infrared region layer is formed by alternately stacking silicon dioxide and zinc sulfide materials; the second near-infrared region layer is formed by alternately stacking silicon dioxide and germanium materials; and the third near-infrared region layer is formed by alternately stacking aluminum oxide and germanium materials.

3. The linearly-graded filter film structure of claim 2, wherein, The first near-infrared region layer has an initial film thickness of 100-150 nm, a gradient increment of 10-18 nm, and a film layer number of 6-8 pairs; wherein the film layer number is the number of repetitions of the alternately stacked silicon dioxide and zinc sulfide materials.

4. The linearly-graded filter film structure of claim 2, wherein, The second near-infrared region layer has an initial film thickness of 150-200 nm, a gradient increment of 20-25 nm, and a film layer number of 8-10 pairs; wherein the film layer number is the number of repetitions of the alternately stacked silicon dioxide and germanium materials.

5. The linearly-graded filter film structure of claim 2, wherein, The third near-infrared region layer has an initial film thickness of 250-280 nm, a gradient increment of 28-32 nm, and a film layer number of 10-12 pairs; wherein the film layer number is the number of repetitions of the alternately stacked aluminum oxide and germanium materials.

6. The linearly-graded filter film structure of claim 1, wherein, The first transition film layer has a thickness of 50-60 nm and a roughness of ≤0.4 nm.

7. The linearly-graded filter film structure of claim 1, wherein, The second transition film layer has a thickness of 50-60 nm and a roughness of ≤0.4 nm.

8. The linearly-graded filter film structure of claim 1, wherein, The coating is performed by electron beam evaporation and ion-assisted deposition.

9. The linearly-graded filter film structure of claim 1, wherein, The film thickness of each of the quartz glass substrate, the first near-infrared region layer, the first transition film layer, the second near-infrared region layer, the second transition film layer, the third near-infrared region layer, the separation layer and the scratch-resistant layer increases linearly in the direction from the quartz glass substrate to the scratch-resistant layer, and when the incident light source passes through the film layers with different thicknesses, the following relationship is satisfied: 2nd=(m+1 / 2)λ; wherein n is the refractive index of the current film layer, d is the film thickness of the current film layer, m is an integer, and λ is the wavelength of the current film layer.

10. A method of producing a linearly graded filter film structure as claimed in any one of claims 1 to 9, characterized in that, The preparation method comprises the following steps: The quartz glass substrate is sequentially subjected to cleaning, plasma activation treatment and silane coupling agent coating treatment; the cleaning is performed by ultrasonic cleaning or ethanol and deionized water cleaning, and the cleaning time is 10-20 min; the plasma activation treatment is performed at a power of 200-300 W for 2-10 min; the concentration of the silane coupling agent is 1%-5%, and the drying temperature after coating is 70-100 DEG C; A first near-infrared region layer is formed on the quartz glass substrate by electron beam evaporation, wherein a vacuum degree of the electron beam evaporation is ≤5×10 -4 Pa, an evaporation rate is 0.5-1 nm / s, 8 film layers are deposited with an initial film thickness of 150 nm and a gradient increment of 18 nm. A first transition film layer is deposited on the first near-infrared region layer by ion-assisted deposition; the power of the ion-assisted deposition is 80-100 W, and the roughness is less than or equal to 0.3 nm; A second near-infrared region layer is obtained by depositing a film on the first transition film layer by electron beam evaporation; wherein 10 film layer logs are deposited at an initial film thickness of 200 nm and a gradient increment of 25 nm; A second transition film layer is deposited on the second near-infrared region layer by ion-assisted deposition; the power of the ion-assisted deposition is 80-100 W, and the roughness is less than or equal to 0.4 nm; A third near-infrared region layer is obtained by depositing a film on the second transition film layer by electron beam evaporation; wherein 12 film layer logs are deposited at an initial film thickness of 280 nm and a gradient increment of 32 nm; A separation layer is deposited on the third near-infrared region layer; A scratch-resistant layer is coated on the separation layer, and a stress relief annealing treatment is performed to obtain the linearly graded filter film structure.

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