Edge Sensor Fingerprint Reader Using Sequential Display Illumination
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Solution Overview
Problem
Current fingerprint reader technologies require a dedicated sensor area on the display screen, which limits the size and reliability of fingerprint sensors on devices like cellphones, as they need to be in direct contact with the user's finger, leading to increased costs and complexity, and existing full-screen fingerprint solutions involve adding layers and high-density sensor arrays that are not practical.
Innovation Solution
A remote sensing fingerprint reader system that uses an array of energy emitting pixels on the display screen, with a sensor located at the edge, illuminating pixels sequentially to capture fingerprint images through reflected energy, allowing the sensor to be placed under the cover glass without disrupting the display function.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a dedicated sensor array is placed across the entire display screen to enable fingerprint sensing anywhere on the screen, then fingerprint sensing capability is improved, but device complexity and manufacturing cost increase significantly
Solution Approach 1:
The patent extracts the sensing function from a full-screen sensor array and concentrates it at the edge of the display. Instead of embedding sensors across the entire screen, a single sensor is positioned at the edge to detect light reflected from the fingerprint, thereby reducing device complexity while maintaining fingerprint sensing capability.
Solution Approach 2:
The display pixels serve multiple functions: they provide visual display output and simultaneously act as light sources for fingerprint illumination. This multi-functionality eliminates the need for separate illumination sources and reduces overall device complexity while maintaining versatile fingerprint sensing capability.
2Measurement precision
If a high-density sensor array is used to capture fingerprint details accurately, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent segments the fingerprint imaging function into two parts: illumination provided by display pixels and detection provided by a single edge sensor. This segmentation allows high measurement precision to be achieved through sequential illumination of different pixel regions rather than through high-density sensor arrays, thereby reducing device complexity.
Solution Approach 2:
The patent transitions from a spatial solution (high-density sensor arrays in the plane of the screen) to a temporal solution (sequential illumination of pixels over time). By using time-multiplexed illumination with a single sensor, the system achieves high measurement precision without increasing device complexity.
3Measurement precision
If capacitive sensors are placed close to the display surface to improve sensing effectiveness, then measurement precision is improved, but the sensor array interferes with the display function and requires unrealistic material thicknesses
Solution Approach 1:
Instead of placing sensors close to the display surface from the front, the patent inverts the approach by positioning the sensor at the edge of the display and using reflected light paths. This inverted configuration maintains sensing effectiveness while eliminating interference with the display function and avoiding the need for unrealistic material thicknesses.
Solution Approach 2:
The patent introduces reflected light as an intermediary between the display pixels and the edge sensor. This light reflection mechanism enables effective fingerprint sensing without requiring physical proximity between sensors and the display surface, thereby avoiding interference with display function and complex material requirements.
4Ease of manufacture
If the sensor is placed at the edge of the display rather than under the cover glass, then ease of manufacture is improved, but the sensor cannot directly contact the fingerprint surface
Solution Approach 1:
The patent uses reflected light from display pixels as an intermediary to bridge the gap between the edge sensor and the fingerprint surface. This allows the sensor to be easily placed at the edge while maintaining measurement precision through optical mediation rather than direct physical contact.
Solution Approach 2:
The patent replaces the mechanical contact-based sensing approach with an optical sensing approach. Instead of requiring direct mechanical contact between the sensor and fingerprint, the system uses light reflection from display pixels to enable the edge sensor to detect fingerprint characteristics, thereby improving ease of manufacture while maintaining measurement precision.
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 reduces the number of required sensors, allows for larger fingerprint scanning areas, and maintains display functionality by using existing display pixels for illumination, enhancing security and reliability without the need for additional layers or high-density sensor arrays.
Implementation Method 1
A remote sensing fingerprint reader system that uses an array of energy emitting pixels on the display screen, with a sensor located at the edge, illuminating pixels sequentially to capture fingerprint images through reflected energy
Data Source
AI summary
A fingerprint reader includes a display screen composed of an array of energy emitting pixels covered by a transparent cover, at least one sensor coupled along an edge of the display screen, a display driver directing the array of energy emitting pixels of the display screen to illuminate in a predetermined sequence, and a microprocessor in communication with the display driver and the at least one sensor. The microprocessor knows the location of the energy emitting pixel being illuminated and the specific time at which the illumination occurs. In use, and when at least one finger is placed on the transparent cover and the display driver is activated, energy from each energy emitting pixel sequentially illuminated is reflected off the fingerprint to the at least one sensor. The energy received at the at least one sensor is at different intensity levels depending upon the ridges and valleys of the at least one fingerprint. The at least one sensor sends a signal to the microprocessor regarding the energy intensity level, from which the microprocessor creates a fingerprint image as the energy emitting pixels are sequentially illuminated.