Contact Image Sensor With Switchable Grating Waveguide
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Solution Overview
Problem
Current contact image sensors are bulky, low in resolution, and unsuitable for field use, making them inadequate for immediate identity and background checks in law enforcement and security applications.
Innovation Solution
A portable, high-resolution, lightweight contact image scanner using a waveguiding structure with switchable Bragg gratings, electrodes, and a platen for optical contact, allowing for efficient capture and processing of fingerprint images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If traditional contact image sensor designs are used, then imaging function is achieved, but device bulkiness increases and portability decreases
Solution Approach 1:
The patent combines the illumination system, waveguiding structure, and detector array into a single integrated contact image sensor module. The waveguiding structure serves dual purposes as both light guide and structural support, eliminating the need for separate illumination housings and reducing overall device bulkiness while maintaining full imaging functionality
Solution Approach 2:
The waveguiding structure performs multiple functions simultaneously: it guides illumination light from the light source to the platen interface, supports the detector array, provides mechanical structure for the compact design, and enables optical coupling between components. This multi-functionality reduces the number of separate components needed, thereby reducing weight and complexity
2Measurement precision
If traditional imaging systems are used, then imaging capability is achieved, but resolution decreases
Solution Approach 1:
The patent employs a localized illumination approach where light is guided through waveguides to specific regions of the platen, enabling high-resolution imaging of fingerprint details. The detector array is positioned in direct optical contact with the waveguiding structure, providing high spatial resolution for capturing fine ridge and valley patterns while keeping the optical system relatively simple through direct coupling rather than complex lens systems
Solution Approach 2:
The patent replaces traditional mechanical focusing and optical routing mechanisms with a waveguiding-based optical system. Light is routed through the waveguiding structure using total internal reflection and evanescent wave coupling rather than mechanical mirrors or complex lens assemblies, thereby achieving high resolution with reduced mechanical complexity
3Adaptability or versatility
If current contact image sensors are used, then imaging function is provided, but portability for field use decreases
Solution Approach 1:
The contact image sensor is designed as a modular segmented system with distinct functional zones: illumination region with waveguiding structure, platen interface region for fingerprint contact, and detection region with detector array. This segmentation allows the device to be optimized for portability while maintaining full imaging capability for field deployment in law enforcement and security applications
Solution Approach 2:
The waveguiding structure incorporates switchable Bragg gratings that can dynamically control light propagation paths. This dynamic control allows the system to adapt to different imaging conditions and optimize performance for various field applications, enhancing versatility while the integrated design keeps overall complexity manageable for portable deployment
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 high-resolution, portable fingerprint scanning capable of immediate processing, suitable for field use, with improved image quality and reduced bulkiness compared to existing technologies.
Implementation Method 1
a waveguiding structure for propagating light in a first direction comprising, in series disposed in a layer sandwiched by transparent substrates, a first clad medium, a first core, a switchable grating clad, a second core, and a second clad medium
Implementation Method 2
Switchable grating regions overlapped by a first voltage-addressed electrode element are operative, in their diffracting state, to diffract TIR light from first core into a path leading to the outer surface of the platen
Implementation Method 3
Switchable gratings region overlapped by a second voltage-addressed electrode element are operative, in their diffracting state, diffract TIR light reflected from the platen into a TIR path to the detector along the second core
Data Source
AI summary
A contact image sensor having a waveguiding structure for propagating light in a first direction including, in series, a first clad medium, a first core, a switchable grating clad, a second core, and a second clad medium sandwiched by transparent substrates, patterned parallel electrode elements orthogonally traversing the waveguides, a light source, a platen and a detector. Switchable grating regions overlapped by a first voltage-addressed electrode element diffract TIR light from the first core towards the platen. Switchable grating region overlapped by a second voltage-addressed electrode element diffract TIR light reflected from the platen into a TIR path within the second core.