Switchable Bragg Waveguide Projection for Thin Structured Illumination
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Solution Overview
Problem
Current display technologies for mobile devices face challenges in miniaturization, achieving high resolution, mechanical robustness, and correcting laser speckle, especially for compact projection displays needed in portable applications.
Innovation Solution
A compact solid-state high-resolution projection display using switchable Bragg gratings (SBGs) with transparent substrates as light guides, coupled with independently switchable transparent electrodes to diffract light and form images, and optionally incorporating infrared sources for object detection and structured illumination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional flat panel display technologies (LCD or DLP) are used for picoprojectors, then image quality can be achieved, but device volume and thickness cannot be sufficiently miniaturized
Solution Approach 1:
The display device is segmented into multiple functional layers: light guide layer, Bragg grating layer, and electrode layer. Each layer performs a specific function, allowing independent optimization and miniaturization while maintaining overall system performance
Solution Approach 2:
The patent replaces mechanical scanning systems (MOEMS) with a static planar display architecture using Bragg gratings and light guides. This substitution eliminates complex moving parts and mechanical synchronization requirements, enabling significant miniaturization while maintaining high resolution
2Volume of moving object
If MOEMS scanning systems are used to reduce size, then device volume decreases, but mechanical robustness and image quality deteriorate
Solution Approach 1:
The patent replaces the mechanical MOEMS scanning system with a static planar light field display architecture. The image is formed by spatially modulating light propagation through Bragg gratings rather than by mechanical scanning, eliminating moving parts and associated reliability issues
Solution Approach 2:
The patent uses dynamically switchable Bragg gratings that can change their diffraction properties in response to applied voltages. This dynamic optical control replaces mechanical scanning motion, achieving the same functionality without mechanical components
3Illumination intensity
If laser light sources are used for high brightness, then illumination intensity improves, but laser speckle noise increases
Solution Approach 1:
The patent segments the light field into multiple discrete rays using the light guide structure. This spatial segmentation of the laser beam breaks up the coherent speckle pattern while maintaining the high brightness advantage of laser illumination
Solution Approach 2:
The light guide acts as an intermediary between the laser source and the display surface. It redistributes the laser light spatially, transforming the coherent beam into a distributed light field that produces images without speckle noise
4Manufacturing precision
If high resolution imaging is achieved, then image quality improves, but device thickness increases
Solution Approach 1:
The patent transitions from volumetric optical paths to a planar two-dimensional light field architecture. High resolution is achieved through spatial modulation in the planar Bragg grating layer rather than through thick optical paths, enabling thin-form-factor high-resolution displays
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 image projection with a thin form factor, overcoming miniaturization and mechanical robustness challenges while reducing laser speckle, and providing full-color imaging and structured illumination capabilities.
Implementation Method 1
The first wavelength light undergoes total internal reflection within the first light guide
Implementation Method 2
Each SBG element in first SBG device diffracts first wavelength light to form an image region on an image surface when subjected to an applied voltage via the transparent electrodes
Data Source
AI summary
A projection display device comprising a light source and an SBG device having a multiplicity of separate SBG elements sandwiched between transparent substrates to which transparent electrodes have been applied. The substrates function as a light guide. A least one transparent electrode comprises a plurality of independently switchable transparent electrode elements, each electrode element substantially overlaying a unique SBG element. Each SBG element encodes image information to be projected on an image surface. Light coupled into the light guide undergoes total internal reflection until diffracted out to the light guide by an activated SBG element. The SBG diffracts light out of the light guide to form an image region on an image surface when subjected to an applied voltage via said transparent electrodes.