Display Finger Sensing With Band-Edge Reflective Polarizer
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Solution Overview
Problem
Existing display systems lack effective methods for sensing a user's finger applied to the display, particularly in enhancing optical performance and reducing optical defects like moiré patterns and Newton's rings.
Innovation Solution
A display system incorporating a reflective polarizer with a structured outer surface, optically diffusive layers, and a structured mirror to enhance finger sensing capabilities while minimizing optical defects, utilizing a reflective polarizer with a band edge transmittance profile and optically diffusive layers to improve infrared sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional reflective polarizer is used in the display system, then the display can function with basic optical performance, but the system cannot effectively sense a user's finger and exhibits optical defects like moiré patterns and Newton's rings
Solution Approach 1:
The patent applies local quality by creating a structured outer surface with specific geometric features (protrusions and recesses) at particular locations on the reflective polarizer. This localized structural modification enables infrared light transmission for finger sensing while maintaining the reflective properties for display functionality, thereby resolving the contradiction between sensing capability and optical defect reduction.
Solution Approach 2:
The reflective polarizer is segmented into multiple functional layers with distinct purposes: a reflective layer for display optical performance, a structured outer surface with geometric features for infrared transmission, and an optically diffusive layer for light scattering. This segmentation allows each layer to optimize its specific function without compromising the others, enabling both finger sensing and reduction of optical defects.
2Measurement precision
If the reflective polarizer has high infrared transmittance for finger sensing, then finger sensing effectiveness is improved, but optical defects and interference patterns may increase
Solution Approach 1:
The patent introduces an optically diffusive layer as an intermediary between the structured outer surface and the display panel. This intermediate layer scatters infrared light to improve sensing accuracy while simultaneously reducing optical interference patterns and defects, thereby resolving the contradiction between sensing accuracy and optical quality.
Solution Approach 2:
The reflective polarizer is constructed as a composite structure combining multiple materials with different optical properties: a reflective material for display performance, a structured outer surface material with geometric features for infrared transmission, and an optically diffusive material for light scattering and interference reduction. This composite approach enables simultaneous optimization of infrared transmittance and reduction of optical defects.
3Ease of manufacture
If a simple reflective polarizer structure is used, then manufacturing is easier and device complexity is lower, but optical performance is degraded with visible defects
Solution Approach 1:
The patent applies parameter changes by modifying the geometric parameters of the outer surface (protrusion height, recess depth, feature spacing) and the optical parameters of the diffusive layer (scattering coefficient, thickness) to optimize both manufacturing feasibility and optical performance. These controlled parameter adjustments enable production of a reflective polarizer with reduced defects while maintaining reasonable manufacturing complexity.
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 system achieves high infrared transmittance and reduced optical defects, enabling effective finger sensing with improved optical performance and reduced damage to adjacent films.
Implementation Method 1
an optical transmittance of the reflective polarizer versus wavelength for a first polarization state includes a band edge, where: a best linear fit to the band edge correlating the optical transmittance to the wavelength at least across a wavelength range where the optical transmittance along the band edge increases from about 10% to at least about 70% has a slope of greater than about 2.5%/nm
Implementation Method 2
a sensing light source configured to emit a first light having a first wavelength W1 toward the finger of the user; and a reflective polarizer disposed between the display panel and the sensor. The sensor is configured to receive and detect at least a portion of the first light reflected by the finger
Implementation Method 3
utilizing a reflective polarizer with a band edge transmittance profile and optically diffusive layers to improve infrared sensing
Data Source
AI summary
A display system for sensing a finger of a user applied to the display system includes a display panel; a sensor for sensing the finger; a sensing light source configured to emit a first light having a first wavelength W1; and a reflective polarizer disposed between the display panel and the sensor. For a substantially normally incident light, an optical transmittance of the reflective polarizer versus wavelength for a first polarization state has a band edge such that for a first wavelength range extending from a smaller wavelength L1 to a greater wavelength L2 and including W1, where 30 nm≤L2−L1≤50 nm and L1 is greater than and within about 20 nm of a wavelength L3 corresponding to an optical transmittance of about 50% along the band edge, the optical transmittance has an average of greater than about 75%.