Photo-Capacitance Fingerprint Sensing Through Display Screens
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Solution Overview
Problem
Existing fingerprint detection technologies face challenges in integrating fingerprint sensors within display screens without sacrificing display area and in differentiating between live human skin and spoofed patterns.
Innovation Solution
The development of photo-capacitance sensors that utilize an array of photo-capacitors with disordered materials capable of absorbing sub-gap photon energies, integrated into display screens to detect reflective patterns, including fingerprints, and differentiate between live human skin and spoofed patterns using infrared and red light reflection analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If fingerprint sensors are integrated within display screens, then device functionality is improved, but display area is reduced
Solution Approach 1:
The patent combines the fingerprint sensor array with the display screen structure, integrating both functions into a single component. The sensor array is positioned behind the display screen, allowing the display to serve dual purposes: visual output and biometric authentication, thereby improving device functionality without sacrificing display area.
2Measurement precision
If photo-capacitors with disordered materials are used to detect sub-gap photon energies, then detection capability is improved, but device complexity is increased
Solution Approach 1:
The patent utilizes disordered materials with specific bandgap properties that enable detection of sub-gap photon energies. By changing the material parameters (using disordered semiconductor materials with appropriate bandgaps), the sensor achieves enhanced detection capability for infrared and red light wavelengths without requiring complex additional components.
3Measurement precision
If multiple light sources are used to illuminate the input surface, then detection accuracy is improved, but energy consumption is increased
Solution Approach 1:
The patent employs multiple light sources emitting at different wavelengths (infrared and red) that can be activated periodically or selectively. The controller illuminates specific wavelengths based on the detection requirements, achieving high detection accuracy while managing energy consumption by not continuously operating all light sources at full power.
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 the integration of fingerprint detection within display screens without area compromise and effectively differentiates between live human skin and spoofed patterns, enhancing security and usability.
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.
Implementation Method 2
Each photo-capacitor may include, or be formed from, a material including trap states in a bandgap of the material which are able to absorb sub-gap photon energies.
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.