Rear Glass Touch Sensor for Fingerprint Recognition
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Solution Overview
Problem
Existing touch sensors on smartphone front panels face issues with visibility and fingerprint recognition due to the placement of fingerprint sensors, which can lead to decreased recognition rates and visibility problems caused by front cover glass and polarizing plates.
Innovation Solution
A touch sensor system is integrated into the rear glass of a portable terminal, featuring a sensing cell part with high and low resolution areas, including a curved sensing cell part, and using conductive metal for increased sensitivity and space utilization, without visibility concerns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the fingerprint sensor is placed on the front panel above the polarizing plate, then visibility is maintained, but the fingerprint recognition rate decreases due to increased thickness
Solution Approach 1:
The patent inverts the conventional placement location by moving the fingerprint sensor from the front panel to the rear glass of the portable terminal. This inversion allows the sensor to be positioned in a location with smaller thickness (behind the rear glass) while maintaining good fingerprint recognition rate, thereby resolving the contradiction between visibility and recognition rate that exists on the front panel
2Measurement precision
If the fingerprint sensor is placed on the front panel under the polarizing plate, then fingerprint recognition rate increases, but visibility deteriorates
Solution Approach 1:
The patent resolves this contradiction by inverting the placement location to the rear glass, where the sensor operates behind the rear glass with minimal thickness interference, achieving high fingerprint recognition rate without any negative impact on front panel visibility since the sensor is now located on the opposite side of the device
3Measurement precision
If conductive metal is used in the sensing cell part on the front panel, then touch sensitivity increases, but visibility is affected
Solution Approach 1:
The patent applies inversion by relocating the sensing cell part to the rear glass, where conductive metal can be freely used to form the sensing electrode without any visibility concerns. This allows the front panel to maintain excellent visibility while the rear glass housing the metal-based sensor achieves high touch sensitivity
Solution Approach 2:
The patent segments the device into distinct functional zones: the front panel dedicated to display and visibility, and the rear glass dedicated to sensing functions. This segmentation allows each part to be optimized independently - the front panel for visual clarity and the rear glass for tactile sensitivity using conductive metals
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 configuration significantly enhances fingerprint recognition rates and touch sensitivity while maintaining visibility, as the rear placement allows for the use of conductive metals without affecting front panel visibility, and expands the function key area.
Implementation Method 1
the capacitive type uses a transparent substrate on which a conductive thin film is formed. When a user touches a surface of a coated transparent substrate with a certain amount of current flowing through the surface of the transparent substrate, the amount of current changes at the contact surface.
Data Source
AI summary
A touch sensor includes a sensing cell part having a plurality of sensing cells, a wiring part having a plurality of wires for transmitting a sensing signal of the sensing cell part, and a pad electrode part having a plurality of pad electrodes for transmitting the sensing signal received from the wiring part to an flexible printed circuits board (FPCB), and is coupled to a rear glass of a portable terminal.