FTIR Contact Image Acquisition Device for Compact Fingerprint Sensing
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Solution Overview
Problem
Existing optical fingerprint acquisition devices are bulky, costly, and complex, making them unsuitable for mobile electronic devices due to their large volume, high cost, and complex structure, and they struggle to meet requirements for low cost, small volume, and ultrathin thickness.
Innovation Solution
A contact image acquisition device utilizing frustrated total internal reflection (FTIR) technology with a light guide plate, light emitters, and light receivers arranged in a matrix, eliminating the need for mechanical components and allowing for a thin, low-power, and long-lasting fingerprint and touch sensing solution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical systems with image acquisition prisms and lenses are used to capture fingerprint images, then fingerprint image acquisition capability is achieved, but the device volume and thickness increase significantly
Solution Approach 1:
The patent extracts and removes the image acquisition prism from the optical system, retaining only the essential light guide plate and light receiver components. This extraction eliminates the need for complex optical paths while maintaining fingerprint acquisition capability through frustrated total internal reflection at the light guide plate's surface.
Solution Approach 2:
The patent replaces the mechanical optical imaging system (prism + lens) with an optical phenomenon-based system utilizing frustrated total internal reflection. This substitution eliminates mechanical optical components and achieves imaging through the interaction of light with the light guide plate and finger surface.
2Measurement precision
If image acquisition prisms and lenses are used in the optical system, then fingerprint imaging is achieved, but the manufacturing cost increases
Solution Approach 1:
The patent replaces expensive, precision-optical components (prisms and lenses) with a simple light guide plate and light receiver assembly. The light guide plate can be a standard optical waveguide material, and the light receivers are conventional photodetectors, significantly reducing component costs while maintaining imaging functionality.
Solution Approach 2:
The patent substitutes the expensive mechanical optical system with an optical phenomenon-based system. The frustrated total internal reflection effect occurs naturally at the interface between the light guide plate and the finger, eliminating the need for costly precision optical components.
3Measurement precision
If a camera is placed under the light guide plate to capture images in existing touch screen technology, then image capture is achieved, but the device structure becomes complex and cannot acquire fingerprint images
Solution Approach 1:
The patent makes the light guide plate serve multiple functions: it acts as both the optical waveguide for light transmission and the imaging surface for fingerprint acquisition. The same light guide plate structure enables both touch sensing and fingerprint imaging without requiring separate camera systems, achieving multi-functionality with a single component.
Solution Approach 2:
The patent replaces the camera-based imaging system with a light receiver array that detects light intensity variations caused by frustrated total internal reflection. This substitution simplifies the structure by eliminating the camera while enabling fingerprint image capture through optical detection at the light guide plate interface.
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 provides a compact, low-cost, and energy-efficient device capable of simultaneous fingerprint acquisition and touch sensing, suitable for integration into mobile devices like smartphones and tablets, with precise response to finger touches and easy maintenance.
Implementation Method 1
The contact image acquisition device is implemented based on the principle of frustrated total internal reflection (FTIR)
Implementation Method 2
The contact image acquisition device is implemented based on the principle of frustrated total internal reflection (FTIR)
Data Source
AI summary
The present invention discloses a contact image acquisition device (11), a touch screen, a fingerprint acquisition device and an electronic device (101), wherein the contact image acquisition device includes: a light guide plate (1); a plurality of light emitters (2) configured for emitting at least a part of light beams into the light guide plate (1), wherein the plurality of light emitters (2) are disposed on at least one side of the light guide plate (1) or under the light guide plate (1); and a plurality of light receivers (3) configured for receiving the light beams emitted into the light guide plate (1) by the light emitters (2), wherein the plurality of light receivers (3) are arranged in a matrix. The touch screen, the fingerprint acquisition device and the electronic device (101) all include one or more of the contact image acquisition devices (11). The contact image acquisition device (11), the touch screen and the electronic device (101) all have a fingerprint acquisition function, and the fingerprint acquisition device, the touch screen and the electronic device (101) may be made into thin films, and they all have the advantages of low cost, low power consumption and long service life.