Microlens Optical Filter Structure for Angle-Selective IR Rejection
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Solution Overview
Problem
Existing optical constructions face challenges in effectively filtering ambient light noise, particularly infrared light, especially at high incident angles, leading to cross-talk and reduced performance in applications like fingerprint sensing.
Innovation Solution
An optical construction comprising a lens layer with microlenses, an optically opaque mask layer, a low index layer, and an optical filter, designed to utilize total internal reflection and angular-dependent light transmission properties to block or transmit light based on incident angle, reducing ambient light interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional optical filter is used to block infrared light, then infrared light transmission is reduced, but the filter fails to effectively block infrared light at high incident angles
Solution Approach 1:
The patent applies local quality by creating an optical filter with spatially varying properties - the filter thickness and/or refractive index change across the surface to account for angular dependence. This allows the filter to maintain effective infrared blocking performance across different incident angles, resolving the contradiction between general infrared blocking and angle-specific reliability.
Solution Approach 2:
The patent changes physical parameters of the optical filter, specifically varying thickness and/or refractive index across the filter surface. This parameter variation enables the filter to adapt its optical properties to different incident angles, maintaining effective infrared light blocking across the full angular range rather than failing at high angles.
2Object-affected harmful factors
If an optical filter is added to block ambient light noise, then light filtering performance is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple functions into a single integrated optical filter that simultaneously blocks both visible and infrared light. By combining filtering functions in one component rather than using separate filters for different wavelength ranges, the patent reduces overall device complexity while maintaining comprehensive ambient light noise filtering performance.
Solution Approach 2:
The optical filter is designed with multi-functionality to handle multiple wavelength ranges (visible and infrared) simultaneously. This universal filter approach eliminates the need for separate specialized filters, reducing component count and assembly complexity while providing broad-spectrum ambient light rejection.
3Object-affected harmful factors
If multiple polymeric layers are used to create the optical filter, then optical transmission control is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent utilizes parameter changes by varying the thickness and refractive index of polymeric layers to achieve desired optical transmission characteristics. By optimizing these parameters during design, the patent achieves precise optical control while maintaining manufacturability - the layer thickness variations are within standard manufacturing capabilities while still achieving the required angular-dependent filtering performance.
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 solution enhances the ability to reject unwanted light, minimizing cross-talk and improving the performance of optical systems by selectively transmitting or reflecting light based on its angle of incidence, particularly in fingerprint sensing applications.
Implementation Method 1
The low index layer can have a sufficiently low index of refraction at the second wavelength so that light having the second wavelength and incident on the low index layer at the second incident angle undergoes total reflection.
Implementation Method 2
for a first wavelength in a wavelength range extending from about 420 nm to about 550 nm, a second wavelength in a wavelength range extending from about 600 nm to about 1500 nm, and for each of first and second orthogonal polarization states, the optical filter has: an optical transmission of greater than about 50% for the first wavelength for each of a first incident angle of less than about 10 degrees and a second incident angle of greater than about 30 degrees
Data Source
AI summary
An optical construction includes a lens layer having a structured first major surface including a plurality of microlenses; an optical filter disposed on the lens layer; an optically opaque mask layer disposed between the lens layer and the optical filter and defining a plurality of openings therein; and a low index layer disposed on the optical filter. For a first wavelength in a visible wavelength range, a second wavelength that can be in an infrared wavelength range, the optical filter has: an optical transmission of greater than about 50% for the first wavelength for each of a first incident angle of less than about 10 degrees and a second incident angle of greater than about 30 degrees, and for the second wavelength, an optical transmission of less than about 15% for the first incident angle and of greater than about 30% for the second incident angle.