Optical Biometric Sensor Diffractive Elements Thick Cover Glass
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Solution Overview
Problem
Conventional capacitive fingerprint sensors face challenges in detecting fine ridge and valley features through thick layers, such as the cover glass in mobile devices, leading to bulky designs and compromised user experience due to the need for cutouts and mechanical buttons.
Innovation Solution
An optical sensor system incorporating a diffractive optical layer with binary zone plates, photon sieves, or Fresnel lenses between a cover layer and an image sensor array, which conditions light to direct only specific reflected beams to sensing elements, enabling clear imaging of biometric features without blurring and through thick cover layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional optical fingerprint sensors are used, then imaging capability is achieved, but sensor size becomes too bulky for mobile devices
Solution Approach 1:
The optical sensor is divided into multiple functional layers: cover layer, diffractive optical element layer, and sensor array layer. This segmentation allows each layer to perform a specific function, enabling miniaturization while maintaining imaging capability. The diffractive optical elements are distributed across the cover layer, creating a distributed optical system that reduces overall sensor bulk.
Solution Approach 2:
The patent transitions from conventional planar optical paths to three-dimensional light field manipulation using diffractive optical elements. By encoding angular information into spatial distribution of light rays and using multi-layer stacking, the system achieves high-resolution imaging in a compact volume, effectively adding dimensional complexity to overcome size constraints.
2Reliability
If capacitive sensing is used to detect through thick cover glass, then sensing capability is maintained, but device design requires cutouts and mechanical buttons
Solution Approach 1:
The diffractive optical elements embedded in the cover layer serve multiple functions simultaneously: they act as protective cover glass, optical focusing elements, and fingerprint sensing interfaces. This multi-functionality eliminates the need for separate cutouts and mechanical buttons, as the entire cover surface becomes both protective and functional for fingerprint authentication.
Solution Approach 2:
The patent merges the cover layer and sensing elements into an integrated structure where diffractive optical elements are embedded within the cover glass itself. This combining of protective and sensing functions into a single unified component eliminates the need for separate structural elements like cutouts and mechanical buttons, simplifying device design.
3Reliability
If capacitive sensors sense through thick layers, then fingerprint detection is achieved, but fine ridge and valley features cannot be detected
Solution Approach 1:
The diffractive optical elements are designed with locally optimized properties where each element's diffraction pattern is tailored to focus light from specific fingerprint regions onto corresponding sensor elements. This local optimization ensures that fine ridge and valley features maintain high contrast and resolution even when sensing through thick cover layers, as each local region is optimized for its specific detection task.
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 allows for a thinner, more efficient biometric image sensor that can detect fingerprints through thick cover layers, enhancing user experience by eliminating the need for cutouts and mechanical buttons, while maintaining high resolution and compatibility with various cover layer thicknesses.
Implementation Method 1
an optical layer, disposed below the cover layer, having a plurality of diffractive optical elements; and a sensing layer, having a plurality of sensing elements disposed below the optical layer, each of the sensing elements being configured to detect light from the biometric object. The plurality of diffractive optical elements of the optical layer are configured to direct light from the biometric object to the plurality of sensing elements.
Data Source
AI summary
An optical sensor for imaging a biometric object includes: a cover layer transparent to light reflected off the biometric object; an optical layer, disposed below the cover layer, having a plurality of diffractive optical elements; and a sensing layer, having a plurality of sensing elements disposed below the optical layer, each of the sensing elements being configured to detect light from the biometric object. The plurality of diffractive optical elements of the optical layer are configured to direct light from the biometric object to the plurality of sensing elements.