Photo-Capacitance Sensor Layout for In-Display Fingerprint Detection
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Solution Overview
Problem
Existing fingerprint sensors are often separate from display areas, limiting flexibility in design and requiring additional space, and existing photo-detector-based technologies are less adaptable for in-display integration.
Innovation Solution
The use of photo-capacitance sensors, comprising an array of photo-capacitors that detect light reflected from an object, such as a fingerprint, integrated within a display stack-up, allowing for in-display fingerprint detection by measuring changes in capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing fingerprint sensors are placed separate from display areas, then they can function effectively for biometric authentication, but they limit design flexibility and require additional space
Solution Approach 1:
The patent merges the fingerprint sensor functionality with the display structure by integrating photo-capacitor arrays directly into the display stack-up. The photo-capacitors are positioned between the display substrate and the touch-sensitive layer, allowing the display to simultaneously serve as both visual output and biometric authentication interface, thereby eliminating the need for separate fingerprint sensor modules and enhancing design flexibility
2Measurement precision
If existing photo-detector-based technologies are used for fingerprint detection, then they can detect reflected light patterns, but they are less adaptable for in-display integration
Solution Approach 1:
The patent transitions from conventional photo-detector technology to photo-capacitor technology, changing the detection parameter from direct optical signal measurement to capacitance change measurement in response to light. This parameter change enables better integration with display structures because photo-capacitors can be fabricated using standard thin-film processes compatible with display manufacturing, and their capacitance changes can be read out through the same electrode structures used for touch sensing
3Adaptability or versatility
If photo-capacitance sensors are integrated within display stack-up, then design flexibility and space requirements are improved, but the device complexity increases
Solution Approach 1:
The patent implements a multi-functional design where the same electrode structures and control circuits serve multiple purposes: driving the display, sensing touch input, and detecting fingerprint patterns. The photo-capacitor arrays share readout circuits with the touch-sensing layer, and the display controller is configured to switch between different sensing modes, thereby reducing the need for additional dedicated components and mitigating the increase in device 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
Enables flexible integration of fingerprint sensors within display areas, enhancing design flexibility and reducing space requirements while maintaining effective biometric authentication capabilities.
Implementation Method 1
The photo-capacitance effect relates to a change in the spatial charge distribution of a material in response to illumination with light within a range of wavelengths. If that material is incorporated between the electrodes of a capacitor, the presence and/or intensity of illumination may be determined based on measuring a change in the capacitance of the capacitor.
Data Source
AI summary
A photo-capacitance sensor includes an input surface and one or more light sources arranged to illuminate a portion of the input surface. The photo-capacitance sensor also includes an array of photo-capacitors arranged to receive light from the one or more light sources which is reflected from an object in contact with, or proximate to, the illuminated portion of the input surface. The array of photo-capacitors is configured for detecting a reflective pattern of the object.