Fingerprint Sensing Device with Motion Detector
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Solution Overview
Problem
Conventional fingerprint sensing devices, particularly capacitive and optical types, face challenges in size constraints, electrostatic discharge, and image quality issues, making them unsuitable for small portable electronic devices, and require complex image processing.
Innovation Solution
A fingerprint sensing device with a capacitive-based motion detector and image processor that captures and processes fingerprint images as the finger is slid over a touch screen, using a light source and a linear sensor array to generate a processed fingerprint image, integrated within a small form factor for handheld devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a capacitive based sensor with two dimensional electrode array is used, then fingerprint detection capability is achieved, but the die size becomes large and electrostatic discharge damage occurs
Solution Approach 1:
The patent divides the fingerprint sensing function into two separate components: a linear array sensor for capturing fingerprint images and a motion detector for tracking finger movement. This segmentation allows each component to be optimized independently, with the linear array requiring minimal space while the motion detector uses the existing touch screen capacitive elements, thus reducing overall sensor die size while maintaining reliability
Solution Approach 2:
The patent makes the touch screen serve multiple functions: it acts as both the user interface and the motion detector for fingerprint capture. The capacitive sensing elements already present in the touch screen are reused to detect finger motion during fingerprint capture, eliminating the need for separate dedicated sensor components and reducing die size
2Reliability
If a capacitive based sensor is used, then fingerprint detection is enabled, but electrostatic discharge from human body can damage the electrode
Solution Approach 1:
The patent extracts the motion detection function from the fingerprint sensing function. By using the touch screen's capacitive elements solely for motion detection and a separate linear array for fingerprint capture, the system eliminates the need for large capacitive electrode arrays that are vulnerable to electrostatic discharge, thus protecting the sensing components while maintaining functionality
Solution Approach 2:
The patent introduces the motion detector as an intermediary component that mediates between the user's finger and the fingerprint sensor. The motion detector tracks finger movement and controls the capture timing, allowing the actual fingerprint sensor to remain small and protected from direct exposure to electrostatic charges from the user's body
3Ease of operation
If optical image sensing module with movement detector is used, then finger movement detection is achieved, but device size increases and structure becomes complex
Solution Approach 1:
The patent merges the motion detection function with the existing touch screen infrastructure. The capacitive sensing elements already present in the touch screen are utilized to detect finger motion during fingerprint capture, eliminating the need for separate optical image sensing modules and movement detectors, thus reducing device complexity and size while maintaining ease of operation
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 solution provides a compact, robust, and reliable fingerprint authentication system for small electronic devices, reducing the risk of electrostatic discharge and improving image quality while maintaining a sleek design.
Implementation Method 1
The motion detector comprising a capacitive sensing element which is coupled with a motion computing circuit, whereby the motion computing circuit determines the finger movement or displacement as the finger is slid over the capacitive sensing element
Implementation Method 2
Another conventional optical fingerprint sensing device is known to utilize light reflected from a surface of a finger placed on an image sensing module to obtain finger print images
Data Source
AI summary
A fingerprint sensing module for a touch screen device. The fingerprint sensing module includes a sensor, a light source, a motion detector, and an image processor. The sensor sets to capture portions for a fingerprint image as a finger is slid over the sensor. The motion detector determines a rate of the finger movement as the finger is slide over the touch screen device. The image processor reads fingerprint images from the sensor and the fingerprint motion data from the motion detector. The image processor subsequently combines portions of the fingerprint images into a complete fingerprint in accordance with the rate of the finger's movement.