Under Display Optical Sensor Rotated to Shift Moiré Frequencies
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Solution Overview
Problem
Capacitive fingerprint sensors face challenges in detecting fine ridge and valley features through thick layers, such as cover glass, and optical fingerprint sensors under displays suffer from moiré effects due to periodicity mismatch between display and sensor components, interfering with fingerprint image analysis.
Innovation Solution
An optical fingerprint sensor is designed with sensor elements rotated relative to the display pixels to adjust the moiré pattern frequency outside the range of interest, mitigating image degradation and improving feature detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an optical sensor is placed under the display to enable under-display fingerprint sensing, then the sensor can be integrated in the active display area, but moiré effects occur due to periodicity mismatch between display and sensor components
Solution Approach 1:
The patent applies asymmetry by deliberately misaligning the periodicity of the optical sensor array with the periodicity of the display components. Instead of matching the sensor grid to the pixel grid, the sensor elements are positioned at non-integer multiples of the pixel pitch, creating an asymmetric relationship that eliminates moiré interference patterns while maintaining effective fingerprint capture
2Measurement precision
If capacitive sensors are used for fingerprint detection, then the sensing array can detect ridge and valley features, but the sensor requires the fingerprint to contact a sensing surface that is close to the sensing array, making it difficult to sense through thick cover glass
Solution Approach 1:
The patent replaces the capacitive sensing mechanism with an optical sensing mechanism. Instead of detecting electrical field changes through the cover glass, the system uses light to capture fingerprint images through the same cover glass, enabling fingerprint detection without requiring direct contact between the sensing array and the fingerprint
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 effectively reduces moiré effect amplitudes and shifts moiré frequencies away from the range of fingerprint features, enhancing the accuracy of fingerprint imaging and analysis.
Implementation Method 1
Optical fingerprint sensors image biometric objects for authenticating and/or verifying users
Implementation Method 2
an array of photosensors configured to capture light reflected from a finger placed on a display surface
Data Source
AI summary
A system and method for an electronic device for imaging a biometric object having structural features of interest is disclosed. The electronic device includes a display including rows of pixel elements, the rows of pixel elements being parallel a first primary direction along a first axis and an optical sensor mounted underneath the display, the optical sensor being parallel to a second primary direction along a second axis. The second axis is rotated at an angle relative the first axis to adjust a moiré pattern outside of a frequency range of the features of interest.