Hybrid Optical Capacitive Fingerprint Sensor for Compact Devices
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Solution Overview
Problem
Conventional fingerprint sensors face challenges in providing robust and reliable fingerprint recognition in mobile devices due to thickness limitations, which affect spatial resolution and fidelity, especially with capacitive sensors and the integration of optical fingerprint sensors in compact devices.
Innovation Solution
The development of hybrid fingerprint sensors that combine optical and capacitive sensing technologies within each pixel, allowing for both optical and capacitive sensing functions, and the use of ultrathin optical fingerprint sensors with photodiode arrays positioned strategically to enhance fingerprint detection and live finger verification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional capacitive sensors are used in mobile devices, then the device can provide fingerprint sensing capability, but the thickness limitations reduce spatial resolution and fingerprint detection fidelity
Solution Approach 1:
The patent combines optical sensing components (light source, optical waveguide, photodetector) with capacitive sensing electrodes within the same sensor structure. This integration allows the sensor to capture both optical reflectance patterns and capacitive signals from the fingerprint, achieving high spatial resolution without increasing overall sensor thickness.
Solution Approach 2:
The patent introduces optical sensing as an additional dimension of detection beyond traditional capacitive sensing. By incorporating light interaction (optical reflectance) into the fingerprint detection process, the system achieves enhanced spatial resolution and fidelity without being constrained by the thickness limitations of purely capacitive approaches.
2Reliability
If optical fingerprint sensors are integrated into compact mobile devices, then fingerprint recognition capability is provided, but the device thickness and complexity increase
Solution Approach 1:
The sensor structure performs multiple functions simultaneously: the light source provides illumination for optical sensing, the optical waveguide directs light through the fingerprint, and the photodetector captures reflected light patterns. This multi-functional integration enhances fingerprint recognition reliability while managing device complexity through shared structural components.
Solution Approach 2:
The patent nests the optical sensing components within the existing capacitive sensor structure. The light source, optical waveguide, and photodetector are integrated into the same footprint as the capacitive electrodes, allowing optical fingerprint sensing to be added without proportionally increasing overall device complexity or thickness.
3Adaptability or versatility
If hybrid optical-capacitive sensors are used, then both optical and capacitive sensing functions are achieved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent segments the sensing functions into distinct modular components: capacitive sensing electrodes, optical sensing elements (light source, waveguide, photodetector), and signal processing circuits. This segmentation allows each component to be optimized and manufactured separately using established processes, then integrated into the final hybrid sensor assembly.
Solution Approach 2:
The patent utilizes parameter changes in material properties and structural dimensions to enable both optical and capacitive sensing functions. By adjusting layer thicknesses, material refractive indices, and electrode configurations, the sensor achieves dual functionality while maintaining compatibility with standard semiconductor manufacturing processes.
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 approach enables improved fingerprint recognition with enhanced spatial resolution and live finger verification, overcoming the thickness limitations of conventional sensors and integrating effectively into compact devices.
Implementation Method 1
an optical sensor module located below the touch screen to receive light that is returned from the top transparent layer
Implementation Method 2
the illumination light undergoes total optical reflection at a top surface of the top transparent layer to direct the totally reflected light to the optical detector array
Implementation Method 3
an optical detector array of photodetectors positioned to receive at least a portion of the returned light to detect a fingerprint
Implementation Method 4
an array of optical collimators located between the touch screen and the optical detector array to direct the received portion of the returned light to the photodetectors through the optical collimators
Data Source
AI summary
In one aspect, a fingerprint sensor device includes a touch panel with an integrated touch sensor module. The integrated touch sensor module includes sensing circuitry to generate a sensor signal responsive to detecting a contact input associated with a fingerprint. The sensing circuitry includes a fingerprint sensor to detect the contact input and generate a signal indicative of an image of the fingerprint, and a biometric sensor to generate a signal indicative of a biometric marker different form the fingerprint. The generated sensor signal includes the signal indicative of the image of the fingerprint and the signal indicative of the biometric marker different from the fingerprint. The sensing circuitry includes processing circuitry communicatively coupled to the sensing circuitry to process the generated sensor signal to determine whether the contact input associated with the fingerprint belongs to a live finger. In another aspect, a device includes a touch screen and an optical sensor module located below the touch screen to provide optical fingerprint sensing.