Optical Filter With Alternating Polymeric Layers For Sharp Visible Infrared Band Edge
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Solution Overview
Problem
Existing optical filters fail to achieve high transmission in visible wavelengths while maintaining high optical density in infrared wavelengths, and they are often thicker than desired for display applications.
Innovation Solution
The development of an optical filter with alternating polymeric layers and optional dye/pigment layers that achieves greater than 50% average transmission in the visible range (420 nm to 550 nm) and optical density greater than 1.5 in the infrared range (650 nm to 800 nm) with a sharp band edge, using a thin film structure (no more than 60 micrometers thick).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional optical filters are used to block infrared light, then infrared blocking is achieved, but visible light transmission is reduced and the filter becomes thicker
Solution Approach 1:
The optical filter is divided into multiple alternating layers of polymer materials with different refractive indices. Each layer is designed with specific thickness to create constructive and destructive interference patterns that selectively block infrared wavelengths while transmitting visible wavelengths, thereby resolving the contradiction between infrared blocking and visible light transmission.
Solution Approach 2:
The filter uses composite structures combining organic polymer layers with inorganic hard coating layers. This composite approach enables the filter to achieve high infrared optical density while maintaining good visible light transmission and mechanical durability, overcoming the limitations of single-material filters.
2Object-affected harmful factors
If optical density in infrared range is increased, then infrared blocking improves, but filter thickness increases
Solution Approach 1:
The filter design optimizes the thickness of each alternating layer to be a fraction (typically quarter-wavelength) of the target infrared wavelength. By precisely controlling these layer thickness parameters and the refractive index contrast between layers, the filter achieves high infrared optical density with minimal overall thickness, avoiding the need for thick single-layer filters.
Solution Approach 2:
The alternating layer structure creates continuous optical interference effects across the infrared spectrum. Each interface between layers contributes to the overall blocking effect, allowing the filter to achieve high infrared density through multiple thin layers rather than requiring a single thick layer, thus maintaining thin overall profile.
3Measurement precision
If sharp band edge is achieved between visible and infrared ranges, then wavelength selectivity improves, but manufacturing precision requirements increase
Solution Approach 1:
The sharp band edge is achieved by segmenting the filter into multiple alternating layers, where each layer contributes to the overall interference pattern. The cumulative effect of many thin layers creates a steep transmission edge with better tolerance to individual layer variations compared to a single thick layer design.
Solution Approach 2:
The filter employs materials with high refractive index contrast at specific interfaces to enhance the sharpness of the band edge. By optimizing the local optical properties (refractive indices) of alternating layers, the design achieves superior wavelength selectivity while maintaining practical manufacturing tolerances.
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 solution significantly improves the signal-to-noise ratio in optical systems by effectively transmitting visible light and blocking near-infrared ambient light, enhancing the performance of optical sensors like fingerprint detectors in display systems.
Implementation Method 1
Optical films can include alternating polymeric layers and can be used to transmit or reflect light in desired wavelength ranges
Implementation Method 2
the second optical filter can include dye(s) and/or pigment(s) to provide an absorption peak
Data Source
AI summary
An optical filter has an average optical transmission of greater than about 50% in a visible wavelength range (e.g., wavelengths from about 420 nm to about 550 nm) and an optical density greater than about 1.5 in an infrared wavelength range (e.g., wavelengths from about 650 nm to about 800 nm). The optical filter can have a sharp band edge between the visible and infrared ranges. For example, a change in percent transmission of at least about 30% can occur over a wavelength range not greater than about 10 nm wide and/or the slope of the band edge can be greater than about 5%/nm. An optical system includes the optical filter disposed between an emissive display and an optical sensor.