Si:NH Multilayer Infrared Band-Pass Filter for Angle Stability
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Solution Overview
Problem
Existing infrared band pass filters experience significant shifts in center wavelength when the incident angle changes, leading to unrecognizable or identification failures in 3D imaging systems due to large angle light reception.
Innovation Solution
The infrared band pass filter is designed with Si:NH layers having a refractive index greater than 3.5 and low refractive index layers with a difference of at least 0.5, alternately stacked to form a multilayer structure, maintaining a pass band between 800 nm and 1100 nm, with a center wavelength shift of less than 12 nm when the angle changes from 0 to 30 degrees.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional multilayer films with Ti3O5, Ta2O5, ZrO2, Nb2O5, TiO2 and MgF2 or SiO2 are used, then the filter structure is simple and manufacturing is easier, but the center wavelength shifts significantly (31-34 nm) when incident angle changes from 0 to 30 degrees
Solution Approach 1:
The patent changes the refractive index parameter of the high refractive index layer material from conventional values (Ti3O5, Ta2O5, etc. with n<3.0) to Si:NH material with refractive index greater than 3.5. This parameter change in material properties reduces the wavelength shift to less than 12 nm when incident angle changes from 0 to 30 degrees, while maintaining a similar multilayer structure configuration.
Solution Approach 2:
The patent uses Si:NH composite material which combines silicon with nitrogen and hydrogen elements to achieve a refractive index greater than 3.5. This composite material approach enables both the simplified structure (comparing to complex angle correction systems) and improved wavelength stability (shift <12 nm), resolving the contradiction between structural simplicity and wavelength precision.
2Manufacturing precision
If the refractive index difference between high and low refraction index layers is small, then the manufacturing process is simpler with conventional materials, but the wavelength shift exceeds acceptable limits for 3D imaging
Solution Approach 1:
The patent specifies a refractive index difference parameter of at least 0.5 between the high refractive index layer (Si:NH with n>3.5) and the low refractive index layer (MgF2 or SiO2 with n<3.0). This parameter specification ensures that the center wavelength shift is reduced to less than 12 nm for incident angles from 0 to 30 degrees, while maintaining manufacturability through well-established deposition processes for these specific materials.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enhances 3D imaging capabilities by minimizing wavelength shifts and maintaining high transmissivity and hardness, reducing warping, and improving image analysis in 3D imaging systems.
Implementation Method 1
The refraction index of each Si:NH layer is larger than 3.5 in the wavelength range between about 800 nm and 1100 nm... the refraction index of each low refraction index layer is smaller than 3... an difference value between the refraction index of the each Si:NH layer and the low refraction index layer is larger than 0.5
Data Source
AI summary
The present disclosure relates to an infrared band pass filter, which comprises a first multilayer film. The first multilayer film including a plurality of Si:NH layers and a low refraction index layer. The plurality of low refraction index layers are stacked with Si:NH layers alternatively; wherein the difference between the refraction index of Si:NH layer and the refraction index of the low refraction index layer is greater than 0.5. The infrared band pass filter has a pass band in a wavelength range of 800 nm and 1100 nm, and when the incident angle is changed from 0 degrees to 30 degrees, the center wavelength of the pass band is shifted less than 12 nm, and the infrared band pass filter of the present disclosure can be used to enhance the 3D image resolution when applied to a 3D imaging system.