Fingerprint Detector With Isolated Light Emitting Structures
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Solution Overview
Problem
Fingerprint detectors face accuracy issues due to uneven light distribution from the backlight module affecting the interpretation of surface features, as the sensing array is disposed above the backlight module, leading to non-uniform light incidence on the object.
Innovation Solution
The fingerprint detector employs two isolated light emitting structures (LES) that are coplanar and do not affect each other, with a driving circuit, sensing array, gate driving circuit, reading circuit, and time sequence control circuit to provide power and control the emission of scanning light, ensuring uniform light distribution and accurate feature interpretation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the sensing array is disposed above the backlight module, then the device structure is simplified, but the light distribution becomes uneven affecting reading accuracy
Solution Approach 1:
The patent divides the light emitting structure into multiple independent light emitting elements (first LES, second LES, third LES, fourth LES) arranged in a matrix pattern. Each element can be independently controlled to emit scanning light, ensuring uniform light distribution across the sensing array while maintaining a simplified overall device structure.
Solution Approach 2:
The patent employs time-division multiplexing where light emitting elements are activated in periodic sequences. During specific time periods, certain LES elements emit scanning light while others remain inactive, allowing the sensing array to read light sensing voltages without interference from high-voltage AC signals, thus improving reading accuracy.
2Illumination intensity
If high-voltage AC is provided to the light emitting structure, then the light emission intensity is sufficient, but the voltage affects accuracy of reading light sensing voltage
Solution Approach 1:
The patent implements periodic activation of light emitting elements combined with time-division multiplexing. High-voltage AC is applied to LES elements only during specific time periods when they need to emit light, while the sensing array reads light sensing voltages during periods when LES elements are inactive. This temporal separation ensures sufficient light emission intensity while preventing voltage interference with reading accuracy.
Solution Approach 2:
The patent segments the light emitting structure into multiple independent elements that can be controlled separately. This allows the driving circuit to apply high-voltage AC to only the currently active LES element while other elements remain inactive, isolating the high-voltage signals from the sensing array and preventing voltage interference during reading operations.
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 enhances the accuracy of reading fingerprint features by ensuring uniform light incidence and reducing errors caused by high-voltage ACs, improving the overall performance of the fingerprint detection process.
Implementation Method 1
When a voltage is applied to an LES, the LES emits scanning light
Implementation Method 2
the plurality of light sensing elements 122 generate corresponding light sensing voltages according to the scanning light reflected by the finger
Data Source
AI summary
A fingerprint detector includes a driving circuit, a sensing array, a gate driving circuit, a reading circuit, a first light emitting structure and a second light emitting structure. The first and the second light emitting structures are isolated from one another. The driving circuit provides power to the first and the second light emitting structures. The sensing array includes a plurality of first light sensing elements disposed under the first light emitting structure and a plurality of second light sensing elements disposed under the second light emitting structure. Each of the light sensing elements generates a light sensing voltage according to scanning light received. The gate driving circuit drives a plurality of rows of the light sensing elements sequentially through a plurality of gate lines. The reading circuit sequentially or synchronously reads the light sensing voltages generated by light sensing elements in different columns of a same row driven by the gate driving circuit.