Ultra-thin Optical Fingerprint Scanner Using Light Guide Plate
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Solution Overview
Problem
Existing optical fingerprint and palmprint acquisition apparatuses are too large and costly, making them unsuitable for ultra-thin electronic products due to their bulky design and insufficient aesthetic appeal, while semiconductor-based systems lack sensitivity and durability.
Innovation Solution
An ultra-thin image acquisition apparatus using a light guide plate with a pinhole imaging plate and image sensor, where the light source is disposed on one side, and the image scanner is spaced apart, allowing for frustrated total internal reflection and reduced thickness, integrated into terminal devices and liquid crystal terminal devices with fewer components and lower costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional optical elements (prism, lens) are used to carry fingerprint and palmprint, then image acquisition function is achieved, but the vertical dimension of the apparatus becomes too large
Solution Approach 1:
The patent extracts the core imaging function from traditional bulky optical elements (prism and lens) and implements it using a simplified optical path with a light guide plate and image sensor positioned close to the light source. This extraction eliminates the need for large vertical spacing while maintaining imaging capability, directly resolving the contradiction between measurement precision and apparatus length.
Solution Approach 2:
The patent transitions from a traditional optical path requiring large vertical dimension to a compact design where the image sensor is positioned adjacent to the light source. By changing the spatial arrangement from vertical stacking to horizontal/adjacent positioning, the apparatus achieves fingerprint acquisition sensitivity without requiring large vertical dimension.
2Measurement precision
If more optical elements are used to improve image acquisition, then measurement capability is enhanced, but device complexity and overall size increase
Solution Approach 1:
The patent extracts only the essential imaging components (light guide plate and image sensor) while eliminating non-essential optical elements. This selective extraction maintains fingerprint acquisition sensitivity while significantly reducing device complexity by removing unnecessary optical components from the traditional prism-lens-mirror system.
Solution Approach 2:
The patent merges the light source and image sensor into a compact adjacent arrangement, eliminating the need for separate optical paths and multiple optical elements. This merging of components achieves the imaging function with minimal device complexity while preserving measurement precision.
3Adaptability or versatility
If larger prism surface is used to carry palmprint, then palmprint acquisition is enabled, but volume and cost of the apparatus increase
Solution Approach 1:
The patent extracts the imaging function from the large-volume prism and implements it using a flat light guide plate with adjacent image sensor. This extraction enables palmprint acquisition capability while eliminating the need for large prism volume, as the compact optical path can accommodate larger sensing areas without increasing overall apparatus volume.
Solution Approach 2:
The patent uses a thin light guide plate instead of a bulky prism to carry the imaging function. This thin-film approach enables palmprint acquisition capability across larger areas while maintaining minimal volume, as the light guide plate can be made thin and flexible to accommodate various sensing areas without proportionally increasing volume.
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 significantly reduces the size and thickness of the image acquisition module, enhances sensitivity, and integrates fingerprint and palmprint acquisition functions with improved aesthetics and lower costs, meeting the requirements of modern electronic products.
Implementation Method 1
a light guide plate; a light source for emitting light into the light guide plate
Implementation Method 2
the image scanner includes a pinhole imaging plate disposed to be spaced apart from the light guide plate, wherein the pinhole imaging plate is provided with at least one imaging pinhole
Data Source
AI summary
An image acquisition apparatus, a terminal device, a liquid crystal terminal device, and an image acquisition method are provided. The image acquisition apparatus (8) includes a light guide plate (1) and an image scanner (16) disposed to be spaced apart from the light guide plate (1), a light source (2) being disposed at a side of the light guide plate (1). The image acquisition apparatus (8) is integrated into the terminal device (7). The liquid crystal terminal device includes a LCD panel (11), a backlight element (12) and the image acquisition apparatus (8), an image scanner (16) of the image acquisition apparatus (8) being disposed in the backlight element (12). The image acquisition method includes: making at least part of light emitted by the light source (2) enter and propagate inside the light guide plate (1) through TIR, and acquiring an image of an object on the other side of the light guide plate (1) by an image scanner (16). An ultra-thin image acquisition apparatus (8), terminal device (7) and liquid crystal terminal device formed based on a waveguide principle and a multi-pinhole imaging principle significantly reduce the size and thickness of an image acquisition module in the device and greatly facilitate the implementation of mobile devices and embedded devices in which an image acquisition function is required.