Fingerprint Sensor Micro-Lens Spacer Layer Design
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Solution Overview
Problem
Fingerprint sensing devices face challenges in achieving high sensing resolution due to uneven finger pressure causing air gap variations and micro-lens crushing, which result in optical focus point and light acceptance angle variations.
Innovation Solution
A fingerprint sensing device is designed with a micro-structure layer including micro-lens and dummy structures, and a spacer layer with main and sub-spacers to maintain a stable spacing, preventing micro-lens crushing and improving optical focus and light acceptance angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light collimation is implemented to overcome light reflection from adjacent peaks/valleys, then light reflection is reduced, but uneven finger pressure causes air gap variation and micro-lens crushing, resulting in optical focus point variation and light acceptance angle variation
Solution Approach 1:
The patent introduces a spacer layer with spacers positioned between the micro-lens array and the fingerprint surface to preemptively compensate for uneven finger pressure. The spacers act as cushioning elements that maintain a stable air gap, preventing micro-lens crushing before it occurs and ensuring consistent optical focus and light acceptance angles across the sensing area.
Solution Approach 2:
The spacer layer serves as an intermediary element between the fingerprint surface and the micro-lens array. It mediates the interaction by providing a controlled air gap that decouples the micro-lenses from direct contact with the fingerprint, thereby stabilizing the optical path while still allowing light to pass through for collimation.
2Reliability
If a spacer layer is added to maintain stable spacing, then micro-lens crushing is prevented, but device complexity increases
Solution Approach 1:
The spacer layer is implemented as a thin film structure with integrated spacers, combining the functions of spacing and protection in a single lightweight layer. This approach maintains spacing stability while minimizing the increase in device complexity and thickness compared to adding separate rigid spacer components.
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 solution enhances sensing resolution by stabilizing the spacing between the micro-structure and sensing elements, improving light collimation and reducing light loss, thereby improving the overall performance of the fingerprint sensing device.
Implementation Method 1
fingerprint sensors need to be designed with light collimation to overcome the problem of light reflection from adjacent peaks/valleys of the fingerprint
Implementation Method 2
a spacer layer located between the second substrate and the sensing element layer, and including multiple main spacers
Data Source
AI summary
A fingerprint sensing device includes a first substrate, a sensing element layer, a second substrate, a micro-structure layer, and a spacer layer. The sensing element layer is located on the first substrate and includes multiple sensing elements. The second substrate is located on the sensing element layer. The micro-structure layer is located between the second substrate and the sensing element layer, and includes multiple micro-lens structures and multiple dummy structures. Orthogonal projections of the micro-lens structures on the first substrate overlap orthogonal projections of the sensing elements on the first substrate. The spacer layer is located between the second substrate and the sensing element layer, and includes multiple main spacers. Each of the main spacers covers at least one of the dummy structures.