Compact Edge-Illuminated Diffractive Display for Mobile Projection
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Solution Overview
Problem
Current display technologies for mobile devices, such as picoprojectors, face challenges in miniaturization, achieving high resolution, mechanical robustness, and correcting laser speckle, while also requiring a thin form factor for integration into portable devices.
Innovation Solution
A compact solid-state high-resolution data projection display using switchable Bragg grating (SBG) devices with transparent substrates as light guides, coupled with independently switchable transparent electrodes to diffract light and form images, and optionally incorporating infrared sources and sensors for enhanced functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional flat panel display technologies (LCD or DLP) are used, then display resolution and image quality are improved, but device size and volume cannot be miniaturized sufficiently
Solution Approach 1:
The patent replaces conventional mechanical display structures (LCD panels, DLP chips) with a holographic projection system that uses light field modulation. The holographic display creates images through optical interference patterns that can be projected at a distance, eliminating the need for bulky display panels while achieving high resolution through the holographic encoding of image information.
Solution Approach 2:
The patent transitions from two-dimensional display surfaces to three-dimensional optical field manipulation. By encoding images as holograms that utilize the third dimension (depth/projection distance), the system achieves high resolution without requiring a proportionally large display area, thereby reducing device volume.
2Volume of moving object
If MOEMS scanning technology is used to reduce display size, then device compactness is improved, but mechanical robustness and scanning speed requirements become excessively high
Solution Approach 1:
The patent eliminates mechanical scanning components by using a static holographic display that projects images directly. Instead of mechanically scanning a small display surface, the system uses optical field modulation to create the complete image at once, thereby removing mechanical moving parts and improving reliability while maintaining compact size.
3Illumination intensity
If laser illumination is used for projection, then image brightness is improved, but laser speckle artifacts increase
Solution Approach 1:
The patent addresses laser speckle by using a diffractive optical element that intentionally creates a controlled scattering pattern. This scattering mechanism, which normally causes harmful speckle artifacts, is instead used to create the holographic image itself, thereby converting the harmful effect into the desired imaging function while maintaining high brightness.
4Length of stationary object
If display thickness is reduced for thin form factor, then ease of integration into mobile devices is improved, but optical path length for image formation is reduced
Solution Approach 1:
The patent resolves the thickness constraint by utilizing the third dimension (projection distance) for optical path length. Instead of requiring a long optical path within the display thickness, the system projects holograms at a distance, effectively extending the optical path in the depth dimension rather than requiring increased physical thickness of the display device.
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 enables high-resolution image projection with a thin form factor, addressing the challenges of miniaturization and mechanical robustness, while also providing effective correction of laser speckle and integration into mobile devices.
Implementation Method 1
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
Implementation Method 2
a compact edge-illuminated projection display based on switchable Bragg gratings
Implementation Method 3
The first wavelength light undergoes total internal reflection within the first light guide
Implementation Method 4
transparent substrates sandwiching the SBG device, said substrates together functioning as a first light guide
Data Source
AI summary
There is provided a projection display device comprising: a light source, an SBG device comprising a multiplicity of separately SBG elements sandwich between transparent substrate to which transparent electrodes have been applied. The substrates function as a light guide. A least one transparent electrode comprises plurality of independently switchable transparent electrodes 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.