Integrated Capacitive Optical Fingerprint Sensor Pin Hole
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Solution Overview
Problem
Conventional fingerprint detection methods in slim electronic devices face challenges due to insufficient fingerprint capture area and residual fingerprint issues, leading to compromised verification accuracy and increased complexity and cost, especially in capacitive and optical sensors used in mobile phones.
Innovation Solution
Integration of a capacitive sensor with a non-focusing optical sensor using a single pin hole opening within a ring electrode, allowing for non-contact fingerprint detection and verification without the need for a cutout or thick cover modifications, utilizing capacitive proximity to trigger optical sensing for maximum resolution and avoiding finger contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacitive sensor is placed under a thin overlay (e.g., on/off button) to increase capacitive sensitivity, then capacitive sensitivity is improved, but the fingerprint capture area becomes insufficient for proper verification
Solution Approach 1:
The patent combines capacitive sensing and optical imaging into a single integrated sensor system. The capacitive sensor array and optical image sensor share the same physical location and functional integration, allowing the system to leverage both capacitive proximity detection and optical fingerprint capture within the same limited space, thereby resolving the contradiction between sensitivity and capture area
Solution Approach 2:
The integrated sensor serves multiple functions: it performs capacitive proximity sensing to detect finger approach, triggers optical imaging for fingerprint capture, and provides anti-spoofing verification. This multi-functionality allows a single compact component to replace what would traditionally require separate sensors, maintaining both sensitivity and sufficient capture area
2Area of stationary object
If an optical sensor uses an array of pin holes with corresponding display pixels to capture sufficient fingerprint area, then fingerprint capture area is improved, but device complexity and manufacturing cost significantly increase
Solution Approach 1:
The patent extracts the pin hole array and micro-lens array from the traditional optical sensor design, eliminating these complex optical components. Instead, it uses a single optical image sensor that directly captures reflected light from the fingerprint, removing the need for intricate optical path management while maintaining sufficient fingerprint capture area
Solution Approach 2:
The patent uses the capacitive sensor array pattern as a template to guide the optical sensor design. By copying the capacitive sensor layout and integrating optical sensing at corresponding locations, the system achieves coordinated sensing without requiring separate complex optical components for each pixel
3Measurement precision
If a non-focusing optical sensor uses an array of pin holes to capture fingerprint image, then optical resolution is improved, but finger contact on the cover is required which leaves residual fingerprints
Solution Approach 1:
The capacitive sensor detects finger proximity and triggers the optical imaging before actual contact occurs. This preliminary detection allows the system to capture the fingerprint image at the optimal moment when the finger is close but not yet touching, preventing residual fingerprint deposition while maintaining imaging capability
Solution Approach 2:
The system uses capacitive sensing as feedback to monitor finger approach in real-time. When the capacitive signal indicates the finger has reached the optimal imaging distance, the optical sensor is triggered to capture the image, providing continuous feedback control that eliminates the need for physical contact
4Measurement precision
If a focusing optical sensor is used to achieve high resolution fingerprint capture, then optical resolution is improved, but device thickness increases due to long optical path requirements
Solution Approach 1:
The patent replaces the mechanical optical focusing system (lenses, prisms, long optical paths) with an electronic/capacitive sensing approach. The capacitive sensor array provides proximity detection and triggering without requiring physical optical focusing components, thereby maintaining thin device profile while achieving sufficient imaging resolution through integrated sensing
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 efficient and accurate fingerprint verification with improved sensitivity and reduced manufacturing costs, providing dual security anti-spoofing features and enhanced optical resolution, while maintaining a slim device form factor.
Implementation Method 1
the capacitive sensor is configured to detect capacitance resulting from proximity of a finger to the sensor
Implementation Method 2
Optical image sensors typically convert optical signals, such as light that can be either invisible or visible, into electrical signals
Data Source
AI summary
An electronic device and method are provided having an optical image sensor and a capacitive proximity sensor. A pin hole opening within a ring electrode of the capacitive proximity sensor is integrated into and used by the optical sensor. Inner and outer electrodes of the ring electrode can be centered about the pin hole opening and spaced apart to perform capacitive proximity detection of a live finger. When brought in proximity to the ring electrode, the finger can be imaged using the present integrated capacitive proximity sensor with an optical sensing mechanism that utilizes the pin hole to not only allow for micro-imaging of an object, such as a finger, but also to provide high resolution fingerprint comparison and blood oxyhemoglobin saturation comparison for biometric control and access to an electronic device, such as a mobile phone.