Fingerprint Recognition IC with Variable Reference ADC
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Solution Overview
Problem
Fingerprint recognition devices face challenges when integrated into displays, particularly with capacitive methods having poor sensing distance, ultrasonic methods being costly and power-intensive, and optical methods being vulnerable to environmental conditions.
Innovation Solution
A fingerprint recognition device with a display, a touch sensor panel, and a fingerprint recognition integrated circuit (FPIC) that includes a pixel with a photoelectric element, a low noise amplifier, and an analog-to-digital converter with a variable reference voltage generator, comparator, and counter, allowing for efficient fingerprint scanning and image processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If capacitive method is used for fingerprint recognition on display, then integration with display is achieved, but sensing distance characteristic deteriorates
Solution Approach 1:
The patent replaces the capacitive sensing mechanism with an optical sensing mechanism. The optical method uses light emission and detection to capture fingerprint images, substituting the electrical field-based capacitive sensing with photons-based optical detection, thereby achieving both display integration and adequate sensing distance.
Solution Approach 2:
The patent changes the fundamental sensing parameter from electrical capacitance to optical properties (light reflection and absorption). By using different physical parameters (optical instead of electrical), the system achieves both display compatibility and sufficient sensing distance characteristics.
2Measurement precision
If ultrasonic method is used for fingerprint recognition, then sensing distance is improved, but device cost and power consumption increase
Solution Approach 1:
The patent employs inexpensive optical components (light emitters and photodetectors) instead of costly ultrasonic transducers. The optical method uses readily available LED and photodiode technologies, significantly reducing sensor cost while maintaining adequate sensing distance for fingerprint recognition.
Solution Approach 2:
The patent substitutes the mechanical ultrasonic vibration-based sensing system with an optical system using light emission and detection. This replacement eliminates the need for complex ultrasonic generators and piezoelectric materials, reducing both cost and device complexity.
3Measurement precision
If optical method is used for fingerprint recognition, then sensing distance and cost are improved, but environmental vulnerability increases
Solution Approach 1:
The patent implements dynamic adaptation by using multiple wavelengths of light and adjusting the optical parameters based on environmental conditions. The system can dynamically select appropriate light wavelengths and detection parameters to compensate for variations in temperature, humidity, and lighting conditions.
Solution Approach 2:
The patent uses multiple optical parameters (different wavelengths, intensities, and timing) to create a robust sensing system that can adapt to environmental variations. By changing and combining multiple optical parameters, the system maintains reliability across different environmental conditions.
4Measurement precision
If high resolution fingerprint scanning is implemented, then measurement precision is improved, but internal complexity increases
Solution Approach 1:
The patent divides the fingerprint sensing area into multiple pixel elements arranged in an array. Each pixel independently captures light reflection from a specific region, and the collective data from all pixels forms the complete high-resolution fingerprint image. This segmentation enables high resolution without requiring a single complex sensing element.
Solution Approach 2:
The patent transitions from a single-point or linear sensing approach to a two-dimensional pixel array configuration. By adding the spatial dimension with multiple rows and columns of photodetectors, the system achieves high resolution through spatial distribution rather than through complex single-element design.
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 reduces internal complexity and enhances resolution, enabling efficient fingerprint recognition on displays while minimizing power consumption and environmental vulnerabilities.
Implementation Method 1
a pixel including a photoelectric element for receiving light reflected by the fingerprint
Data Source
AI summary
A fingerprint recognition device includes a display, a touch sensor panel (TSP) which senses a touch, and a fingerprint recognition integrated circuit (FPIC) which scans a fingerprint. The FPIC includes a pixel including a photoelectric element which receives light reflected by the fingerprint, a low noise amplifier (LNA) which outputs a signal voltage by converting an electric charge received from the photoelectric element, and an analog-to-digital converter (ADC) which converts the signal voltage into a digital signal. The ADC includes a variable reference voltage generator which provides a variable reference voltage, a comparator which adds the variable reference voltage to the signal voltage, performs correlated double sampling on the result of the addition, and outputs a comparison signal by comparing the result of the correlated double sampling with a ramp voltage, and a counter which outputs the digital signal by counting the comparison signal.