Multi-level Optical Diffuser for Infrared Clarity
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Solution Overview
Problem
Standard optical diffuser films scatter light in both visible and near-infrared wavelengths, causing distortion in fingerprint images and compromising the functionality of fingerprint sensors, which require clear infrared light for identification.
Innovation Solution
An optically diffusive film with a structured surface featuring substantially parallel, planar surfaces at varying height levels is designed to create a 'band edge' between visible and near-infrared light, providing low clarity in visible wavelengths and high clarity in infrared wavelengths, ensuring sufficient diffusion for displays while maintaining image clarity for fingerprint sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a standard optical diffuser film is used to provide light diffusion for display uniformity, then visible light diffusion is improved, but near-infrared light clarity deteriorates causing fingerprint sensor distortion
Solution Approach 1:
The optical diffuser film is designed with wavelength-selective properties where different regions of the electromagnetic spectrum experience different optical treatments. Visible light (400-700 nm) undergoes strong diffusion through the structured surface features, while near-infrared light (700-2000 nm) maintains high transmission with minimal scattering. This local quality differentiation in optical response resolves the contradiction by providing display uniformity through visible light diffusion while preserving fingerprint sensor functionality through infrared light clarity.
Solution Approach 2:
The film's optical properties are optimized by controlling specific parameters including the height, spacing, and geometry of surface structures to create a spectral transition point. By adjusting these structural parameters, the film achieves high diffusion efficiency for visible wavelengths while maintaining low diffusion for near-infrared wavelengths. This parameter optimization enables simultaneous achievement of display uniformity and fingerprint sensor compatibility.
2Illumination intensity
If the film structure is optimized for high visible light diffusion, then display quality is improved, but infrared light scattering increases reducing fingerprint identification accuracy
Solution Approach 1:
The optical spectrum is segmented into two distinct regions: visible light (400-700 nm) and near-infrared light (700-2000 nm). The film structure is designed with features whose dimensions are comparable to visible light wavelengths, creating strong diffusion for this segment while being sub-wavelength for infrared light, allowing it to pass through with minimal interaction. This spectral segmentation resolves the contradiction by treating different wavelength ranges differently.
Solution Approach 2:
The solution adds a spectral dimension to the optical diffusion process. Instead of uniform diffusion across all wavelengths, the film introduces wavelength-dependent diffusion characteristics by designing surface structures with specific dimensional relationships to different parts of the electromagnetic spectrum. This dimensional differentiation in the optical response resolves the contradiction between display quality and fingerprint accuracy.
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
The film achieves the necessary diffusion in visible wavelengths for display uniformity while maintaining high optical clarity in near-infrared wavelengths, allowing for effective fingerprint identification without distorting images.
Implementation Method 1
Multi-level optical diffuser with high near infrared clarity
Implementation Method 2
standard optical diffuser films scatter light in both visible and near-infrared wavelengths
Data Source
AI summary
An optically diffusive film includes a structured first major surface with a plurality of substantially parallel, substantially planar first surfaces arranged across the first major surface at a plurality of different first height levels. A height difference between any two of the first surfaces is S times Hmin, where S is a number within 15% of an integer and Hmin is a height difference between lowest and next-lowest first surfaces. For a substantially collimated incident light and for a first wavelength in a human-visible wavelength range, the optically diffusive film has an optical haze, Hv, and an optical clarity, Cv, and for a second wavelength in an infrared wavelength range, the optically diffusive film has an optical haze, Hi, and an optical clarity, Ci, such that the ratio Hv/Hi is greater than or equal to 1.5 and the ratio Ci/Cv is greater than or equal to 1.5.