Switchable Bragg Grating Contact Image Sensor for Compact Biometrics

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Solution Overview

Problem

Current contact image sensors are bulky, low in resolution, and unsuitable for field use, particularly in law enforcement and security applications where immediate identity and background checks are needed.

Innovation Solution

A portable, high-resolution contact image sensor is developed using parallel optical layers with a stack configuration including a collimated beam illumination system, switchable Bragg grating arrays, and a waveguiding structure to capture images directly from a subject's finger, enabling efficient image generation in the field.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If traditional contact image sensor designs are used, then imaging function is achieved, but device size becomes bulky and portability is reduced

Engineering Contradiction:

Improvesensor sizeVSAvoidimaging quality

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The sensor is divided into multiple functional layers including waveguide layer, Bragg grating layers, and detector array, with each layer performing a specific function. This segmentation allows optimization of each component independently while maintaining overall system performance, enabling compact design without sacrificing imaging quality

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent transitions from traditional bulk optical components to planar integrated photonic circuits and waveguide structures. By moving to a two-dimensional integrated layout with light propagating through guided modes rather than free space, the system achieves high-resolution imaging in a thin, compact form factor suitable for portable applications

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Measurement precision

If traditional imaging systems are used, then imaging capability is provided, but resolution remains low

Engineering Contradiction:

Improveimage resolutionVSAvoidsystem structure

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces traditional mechanical focusing systems with photonic crystal and Bragg grating-based optical path control. The periodic structures provide wavelength-selective reflection and guidance, enabling high-resolution imaging through optical interference effects rather than mechanical lens focusing, thereby improving resolution while managing system complexity

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system utilizes changes in refractive index through electro-optic or thermo-optic effects in the photonic crystal structures to dynamically control light propagation paths. By modulating optical parameters rather than physical positions, the system achieves high resolution with reduced mechanical complexity

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If conventional sensor designs are used, then basic imaging is achieved, but field usability is poor

Engineering Contradiction:

Improvefield usabilityVSAvoidsensor weight

Core Design Contradiction:

Ease of operationVSWeight of moving object

Solution Approach 1:

The sensor employs composite photonic structures combining photonic crystals, Bragg gratings, and waveguide materials in a single integrated platform. This composite approach consolidates multiple optical functions into one lightweight component, improving field usability while minimizing weight compared to assemblies of separate optical elements

Inventive Principle:

Principle #40Composite materials

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, high-resolution imaging capability, allowing for immediate image processing and identity verification in field settings, enhancing the usability of contact image sensors for biometric applications.

Implementation Method 1

switchable Bragg grating arrays

Methodology Applied

Scientific EffectBragg diffraction: Bragg Diffraction

Implementation Method 2

waveguiding structure

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 3

detector comprising at least one photosensitive element

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentUS11256155B2Contact image sensor using switchable Bragg gratings

Publication Date: 2022.02.22 DIGILENS INC

AI summary

A contact image sensor comprises: a light source providing a collimated beam; a detector and a switchable grating array comprising first and second transparent substrates sandwiching an array of switchable grating elements with transparent electrodes applied to said substrates, said substrates together providing a total internal reflection light guide. A first transmission grating layer overlays said first substrate. A second transmission grating layer overlays said second substrate. A quarter wavelength retarder layer overlays said second transmission grating layer. A platen overlays said quarter wavelength retarder layer; a polarization-rotating reflecting layer overlaying said first transmission grating layer. An input coupler for directing light from said light source into said light guide and an output coupler for extracting light out of said light guide towards said detector are also provided.