Interchangeable-Prism Fingerprint Scanner for Air and Water Rejection
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Solution Overview
Problem
Existing fingerprint scanners designed for either air-rejecting or water-rejecting configurations have separate components, leading to no economies of scale and increased costs, as water-rejecting scanners require more expensive materials and optics due to higher critical indices.
Innovation Solution
Designing interchangeable prisms with the same geometry for both air-rejecting and water-rejecting configurations, allowing for easy switching by swapping prisms, and optionally adjusting the Scheimpflug angle and refocusing the objective lens to maintain optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate scanners are designed for air-rejecting and water-rejecting configurations, then each scanner can be optimized for its specific configuration, but manufacturing costs increase and economies of scale are lost
Solution Approach 1:
The patent implements a universal scanner platform that can operate in both air-rejecting and water-rejecting configurations by using interchangeable prisms. The main scanner body, including illumination sources, sensors, and optical paths, remains identical for both configurations, while only the prism component needs to be swapped. This multi-functionality approach allows a single device to serve multiple purposes, reducing manufacturing costs through economies of scale while maintaining optimized performance for each specific configuration.
2Reliability
If water-rejecting scanners use higher index of refraction materials, then water-rejecting performance is achieved, but component costs and device complexity increase
Solution Approach 1:
The patent segments the scanner into modular components, with the prism being a separate, interchangeable element. The water-rejecting capability is isolated to the prism component, which can be swapped independently from the rest of the scanner system. This segmentation allows the higher index of refraction materials to be used only where necessary (in the water-rejecting prism) without requiring all components of the scanner to be redesigned or upgraded, thereby reducing overall device complexity and component variety.
3Ease of operation
If interchangeable prisms with same geometry are used, then switching between configurations is simplified, but optical performance adjustments are required
Solution Approach 1:
The patent incorporates preliminary adjustment mechanisms during the prism installation process. The mounting structure includes built-in features that automatically align the prism with the optical path and provide preliminary focusing adjustment. This preliminary action reduces the manual adjustment work required after prism installation, making the configuration switching process easier while accounting for the optical performance adjustments needed between different prism types.
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
Enables a single scanner to operate in both modes with minimal mechanical, optical, and electrical changes, reducing costs and maintaining resolution, while sharing components for economies of scale.
Implementation Method 1
optical fingerprint sensing or scanning apparatuses in a total internal reflection (TIR) configuration
Data Source
AI summary
A fingerprint scanning apparatus including a housing, prism mounting mechanics for fixing a prism within the housing to form a platen surface, wherein the mounting mechanics are configured to receive a prism geometry based on a first prism having a first index of refraction and a second prism having a second index of refraction, wherein the prism geometry comprises a critical angle with respect to the platen surface, wherein each of the first and second prisms has substantially the same critical angle with respect to a corresponding prism surface thereof, an objective lens, and an image sensor. In an example, the first prism has a critical index of refraction equal to or greater than an index of refraction of water and the second prism has a critical index of refraction equal to or greater than an index of refraction of air.