Backlit Finger Feature Structure With Lateral Illuminant Layout
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Solution Overview
Problem
Conventional backlit fingerprint recognition modules face challenges in reducing thickness due to the stacking of multiple circuit boards, which can cause damage and reliability issues, and the flexible printed circuit board (FPC) often blocks the light path.
Innovation Solution
A backlit finger feature recognition structure is designed with a feature sensor that is cut to form a retreat space for the illuminant, allowing the illuminant to be positioned without overlapping the sensor in the stacking direction, and using a light guide member formed by flat plates to guide light emission along the stacking direction, facilitating space utilization and manufacturability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple circuit boards are stacked by bending or folding the FPC to address the light path blockage, then the light path is unblocked, but the module thickness cannot be smoothly reduced and reliability problems occur due to small bending radius
Solution Approach 1:
The patent changes the spatial arrangement from vertical stacking (multiple layers in stacking direction) to lateral arrangement (side-by-side in plane view). The illuminant and feature sensor are positioned adjacent to each other in the plane view rather than overlapping in the stacking direction, eliminating the need for FPC bending while maintaining light path transmission.
2Illumination intensity
If multiple circuit boards are stacked to address the light path blockage, then the light path is unblocked, but the module thickness increases making thinning design difficult
Solution Approach 1:
The patent transitions from a vertical stacking architecture to a lateral arrangement where the illuminant is positioned beside the feature sensor in plane view. This dimensional reconfiguration allows light to reach the sensor without passing through multiple stacked circuit boards, thereby reducing module thickness while maintaining illumination effectiveness.
Solution Approach 2:
The patent extracts the illuminant from the stacked circuit board structure and positions it separately in the retreat space formed by the non-quadrilateral cut of the feature sensor. This separation allows the illuminant to be positioned without requiring additional stacked layers, thus reducing overall module thickness.
3Illumination intensity
If the FPC is bent or folded to stack multiple circuit boards, then the light path is unblocked, but the bending radius is small causing damage to components or circuits
Solution Approach 1:
The patent extracts the illuminant from the FPC stacking structure and positions it independently in the retreat space of the feature sensor. This eliminates the need for FPC bending or folding, thereby removing the harmful mechanical stress and small bending radius issues that cause component damage.
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
The design effectively reduces the overall thickness of the module, improves space utilization, and enhances manufacturability without affecting sensing functionality or electrical connections, while reducing the risk of component damage.
Implementation Method 1
the light guide member guides light emitted from the illuminant to be emitted along the stacking direction
Data Source
AI summary
A backlit finger feature recognition structure includes a feature sensor configured to sense a finger feature, a light guide member disposed surrounding the finger sensor, a circuit board assembly disposed corresponding to the light guide member and electrically connected to a lower side of the feature sensor, and an illuminant electrically connected to the circuit board assembly, wherein in a stacking direction, the illuminant does not overlap the feature sensor, and the light guide member guides light emitted from the illuminant to be emitted along the stacking direction.