A broadband linear filter

Abstract

This invention discloses a broadband linear graded filter for spectral imaging, possessing high transmittance and excellent stray light suppression performance. The filter employs a multilayer thin-film structure, including an interference cutoff film system above a substrate and a narrowband filter film system below. The narrowband filter film system achieves high transmittance in the 500-800 nm wavelength range through an optimized design using multiple alternating combinations of high and low refractive index materials. The interference cutoff film system effectively suppresses stray light through its long-pass and short-pass design.

Description

Technical Field

[0001] This utility model relates to the field of optical thin film design technology, and in particular to the design of a broadband linear filter. Background Technology

[0002] With the development of technological theory and the advancement of imaging technology, people began to study the combination of spectral analysis and imaging technology to obtain spectral information of objects at multiple wavelengths, and spectral imaging technology gradually emerged.

[0003] Linear graded filters stand out due to their high integration, light weight, and stable, compact structure. Their precise design allows them to occupy a small footprint within an optical system while maintaining overall equipment stability and reliability, making them suitable for applications in various complex environments and conditions. As a highly integrated beam-splitting device, linear graded filters are leading the development of imaging technology. In recent years, their applications in aerospace, biomedicine, environmental monitoring, and other fields have become increasingly widespread, and their importance continues to grow. Summary of the Invention

[0004] The purpose of this invention is to provide a wide-spectrum linear filter that has a wide spectral range, high transmittance in the working band, and low transmittance in the non-working band, thus ensuring the performance stability and anti-interference of the filter. To achieve the above objectives, the solution of this utility model is: a broadband linear filter, characterized in that it includes a substrate, a first film stack, and a second film stack. The first film stack is an interference cutoff film system deposited on the upper surface of the substrate, and its structure, from the side closest to the substrate to the air side, is as follows: 0.7185H 0.5871L 0.5691H 0.8087L 0.7490H 0.7540L 0.6878H 0.5385L 0.6240H 0.6856L 0.5649H 0.4486L 0.6627H 0.8362L 0.8090H 0.6661L 0.5519H 0.7209L 0.8280H 0.9860L 1.1647H 0.2128L 0.7158H. 0.9387L 0.7636H 0.8026L 1.0076H 0.2011L 0.6343H 1.3744L 0.8048H1.4480L 1.7920H 0.9787L 1.1192H 1.6497L 1.2870H 3.3403L 1.2903H 1.6080L1.2119H 1.1241L 1.7322H 1.2054L 1.8660H 1.9613L 1.3980H 1.6883L 1.1872H1.3143L 1.6700H 1.3981L 2.1605H 1.7928L The first film stack consists of 1.6290H, 1.2660L, 1.6014H, and 0.6000L, where H is a high-refractive-index material layer with a thickness of 1 / 4 of the center wavelength, and L is a low-refractive-index material layer with a thickness of 1 / 4 of the center wavelength. The second film stack is a narrow-band filter film system deposited on the lower surface of the substrate. From the side closest to the substrate to the air side, the structure is sequentially 0.7356H, 0.8506L, 1.1479HL, and 2H(LH). 2 L(HL) 2 2H(LH) 2 L(HL) 2 2H(LH) 1.2098L 0.8054H1.3691L, where (LH) represents a combination consisting of L layers and H layers. 2 (HL) indicates that the LH combination is repeated twice, and (HL) indicates a combination consisting of H layers and L layers. 2 The HL combination is repeated twice, where H is a high-refractive-index material layer with a thickness of 1 / 4 of the center wavelength, and L is a low-refractive-index material layer with a thickness of 1 / 4 of the center wavelength.

[0005] Furthermore, the substrate is a B270 glass substrate.

[0006] Furthermore, the most preferred high-refractive-index material layer is TiO2, and the most preferred low-refractive-index material layer is SiO2.

[0007] Furthermore, by adopting the above-mentioned scheme, the advantages of this utility model are as follows: using ultra-transparent low-iron glass (such as B270), its transmittance can reach more than 91.5%, and it has good chemical and physical stability. This filter can cover a wide spectral range of 500nm to 800nm, and is suitable for a variety of complex optical applications. Through the design of a multi-cavity FP resonant cavity, the narrowband filter film system significantly improves the light transmission effect of the filter in the working band, with a transmittance of more than 80%. The interference cutoff film system effectively reduces stray light interference in the non-working band, with a transmittance of less than 4%, ensuring the stability and anti-interference performance of the imaging system. Attached Figure Description

[0008] Figure 1 This is a structural diagram of the membrane system of this utility model;

[0009] Figure 2 This is a schematic diagram of the transmittance spectrum of the narrowband filter film system of this utility model;

[0010] Figure 3 This is a schematic diagram of the transmittance spectrum of the interference cutoff film system of this utility model;

[0011] Figure 4 This is a schematic diagram of the transmittance spectrum of this utility model; Detailed Implementation

[0012] The present invention will now be described in detail with reference to the accompanying drawings.

[0013] This invention provides a broadband linear filter, such as... Figure 1As shown, the structure includes a substrate, a first film stack, and a second film stack. The first film stack is an interference cutoff film system, designed using both long-pass and short-pass film systems. The performance of the cutoff band is optimized by adjusting the number of periods and the film thickness. It is deposited on the upper surface of the substrate, and its structure, from the substrate side to the air side, is as follows: 0.7185H 0.5871L 0.5691H 0.8087L 0.7490H 0.7540L 0.6878H 0.5385L 0.6240H 0.6856L 0.5649H 0.4486L 0.6627H 0.8362L 0.8090H 0.6661L 0.5519H 0.7209L 0.8280H 0.9860L 1.1647H 0.2128L. 0.7158H 0.9387L 0.7636H 0.8026L1.0076H 0.2011L 0.6343H 1.3744L 0.8048H 1.4480L 1.7920H 0.9787L 1.1192H1.6497L 1.2870H 3.3403L 1.2903H 1.6080L 1.2119H 1.1241L 1.7322H 1.2054L1.8660H 1.9613L 1.3980H 1.6883L 1.1872H 1.3143L 1.6700H 1.3981L The structure is 2.1605H 1.7928L 1.6290H 1.2660L 1.6014H 0.6000L, where H is a high-refractive-index material layer with a thickness of 1 / 4 of the center wavelength, and L is a low-refractive-index material layer with a thickness of 1 / 4 of the center wavelength. The second film stack is a narrowband filter system, designed with a three-cavity FP resonant cavity structure, in which high-refractive-index and low-refractive-index materials are alternately stacked and deposited on the lower surface of the substrate. Its structure from the substrate side to the air side is 0.7356H 0.8506L 1.1479HL 2H (LH). 2 L(HL) 2 2H(LH) 2 L(HL) 2 2H(LH) 1.2098L 0.8054H 1.3691L, where (LH) represents a combination consisting of L layers and H layers. 2 (HL) indicates a combination of H layers and L layers repeated twice; (HL) indicates a combination consisting of H layers and L layers. 2 The HL combination is repeated twice. Here, H is a high-refractive-index material layer with a thickness of 1 / 4 of the center wavelength, and L is a low-refractive-index material layer with a thickness of 1 / 4 of the center wavelength. The preferred high-refractive-index material layer H is TiO2, and the preferred low-refractive-index material layer L is SiO2.

[0014] Ultra-transparent low-iron glass (such as B270) is selected, with a light transmittance of over 91.5% and good chemical and physical stability.

[0015] The transmittance spectrum of the narrowband filter film system at a center wavelength of 800 nm is shown in the figure below. Figure 2 As shown, this film system significantly improves the transmittance at the center wavelength of 800 nm, and stray waves can be observed in the 500 nm-700 nm band; the transmittance spectrum of the interference cutoff film system is shown in the figure. Figure 3 As shown, this film system effectively controls stray waves in the 500nm-700nm wavelength range; a schematic diagram of the transmittance spectrum of the linear filter is shown below. Figure 4 As shown, a high transmittance of over 80% is achieved at a wavelength of 800nm.

[0016] This invention significantly improves the light transmission of the filter in the working band through the design of a multi-cavity FP resonant cavity, and the interference cutoff film system effectively reduces stray light interference in the non-working band, ensuring the stability and anti-interference performance of the imaging system.

[0017] The above description is only a preferred embodiment of the present utility model and is not a limitation on the design of this case. Therefore, any equivalent changes made to the above embodiments based on this case shall still fall within the scope of the technical solution of the present utility model.

Claims

1. A broadband linear filter, characterized in that, The system includes a substrate, a first film stack, and a second film stack. The first film stack is an interference cutoff film system deposited on the upper surface of the substrate. From the substrate side to the air side, the structure is as follows: 0.7185H 0.5871L 0.5691H 0.8087L 0.7490H 0.7540L 0.6878H 0.5385L 0.6240H 0.6856L 0.5649H 0.4486L 0.6627H 0.8362L 0.8090H 0.6661L 0.5519H 0.7209L 0.8280H 0.9860L 1.1647H 0.2128L 0.7158H 0.9387L 0.7636H 0.8026L. 1.0076H0.2011L 0.6343H 1.3744L 0.8048H 1.4480L 1.7920H 0.9787L 1.1192H 1.6497L1.2870H 3.3403L 1.2903H 1.6080L 1.2119H 1.1241L 1.7322H 1.2054L 1.8660H1.9613L 1.3980H 1.6883L 1.1872H 1.3143L 1.6700H 1.3981L 2.1605H 1.7928L1.6290H 1.2660L 1.6014H 0.6000L, where H is a high-refractive-index material layer with a thickness of 1 / 4 of the center wavelength, and L is a low-refractive-index material layer with a thickness of 1 / 4 of the center wavelength. The second film stack is a narrow-band filter film system deposited on the lower surface of the substrate. From the side closest to the substrate to the air side, the structure is sequentially 0.7356H 0.8506L 1.1479HL 2H(LH). 2 L(HL) 2 2H(LH) 2 L(HL) 2 2H(LH) 1.2098L 0.8054H 1.3691L, where (LH) represents a combination consisting of L and H layers. 2 (HL) indicates that the LH combination is repeated twice, and (HL) indicates a combination consisting of H layers and L layers. 2 The HL combination is repeated twice, where H is a high-refractive-index material layer with a thickness of 1 / 4 of the center wavelength, and L is a low-refractive-index material layer with a thickness of 1 / 4 of the center wavelength.

2. The broadband linear filter according to claim 1, characterized in that, The substrate is a B270 glass substrate.

3. The broadband linear filter according to claim 1, characterized in that, The preferred material layer for a high refractive index material layer is TiO2, and the preferred material layer for a low refractive index material layer is SiO2.

4. The broadband linear filter according to claim 1, characterized in that, The center wavelength is 800nm.

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