Fingerprint Sensor Light-Blocking Layer for Display Signal Noise
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Solution Overview
Problem
The challenge in display devices is the interference between signal lines of the display panel and the fingerprint sensor due to reduced thickness of the optical layer, leading to noise reflection in the fingerprint sensor's signals.
Innovation Solution
A fingerprint sensor design that includes a substrate with a light sensing element, a common electrode, a light-blocking conductive layer with light transmitting holes, and a light guide unit to guide light to the light sensing element, minimizing noise interference by blocking unwanted light and optimizing signal integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the thickness of the optical layer is reduced to prevent interference with other components, then the space for component arrangement is improved, but signal interference between display panel signal lines and light sensing layer signal lines increases
Solution Approach 1:
A light-blocking conductive layer is introduced as an intermediary between the display panel signal lines and the light sensing layer signal lines. This layer selectively blocks optical signals while allowing electrical signals to pass through, preventing noise coupling from the display panel to the fingerprint sensor without compromising the thin-form-factor design
Solution Approach 2:
The optical layer is segmented into multiple functional sub-layers including a light-blocking conductive layer with light transmitting holes, a light guide unit, and a light sensing layer. This segmentation allows each layer to perform its specific function independently, enabling the thin optical layer to simultaneously achieve signal blocking, light guiding, and fingerprint sensing while maintaining compact dimensions
2Device complexity
If the thickness of the optical layer is reduced, then device integration is improved, but noise reflection in sensing signals increases
Solution Approach 1:
The light-blocking conductive layer is configured with spatially varying properties: it contains light transmitting holes at positions corresponding to the light sensing elements to allow useful light signals to pass through, while blocking light in other regions to prevent noise reflection. This local differentiation of optical properties enables the thin structure to simultaneously transmit necessary light and block noise
Solution Approach 2:
The light guide unit acts as an intermediary optical component that directs light from the display panel through the light-blocking conductive layer to the light sensing elements. This intermediary structure ensures that useful light signals are properly guided while the light-blocking layer prevents noise from reflecting back to the sensors
3Reliability
If scan signals of display panel are coupled to sensing signals of light sensing layer, then electrical connectivity is improved, but noise in scan signals is reflected in sensing signals
Solution Approach 1:
The light-blocking conductive layer serves as an electromagnetic shielding intermediary that blocks optical noise from coupling between the display panel scan signals and the light sensing layer sensing signals. The layer's conductive nature provides electromagnetic shielding while its light transmitting holes maintain optical signal transmission, preventing noise reflection while preserving signal integrity
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 design effectively reduces noise reflection and enhances signal clarity for accurate fingerprint recognition while preventing interference from display panel signals, improving the overall performance of the fingerprint sensor.
Implementation Method 1
a light guide unit disposed on the light-blocking conductive layer
Implementation Method 2
a light-blocking conductive layer disposed on the common electrode and including light transmitting holes
Implementation Method 3
a light sensing element that includes a sensing electrode disposed on the substrate, a semiconductor layer disposed on the sensing electrode, and a common electrode disposed on the semiconductor layer
Data Source
AI summary
A fingerprint sensor including: a substrate; a light sensing element that includes a sensing electrode disposed on the substrate, a semiconductor layer disposed on the sensing electrode, and a common electrode disposed on the semiconductor layer; a light-blocking conductive layer disposed on the common electrode and including light transmitting holes; and a light guide unit disposed on the light-blocking conductive layer.