Polarized Illumination Micro-Display Substrate
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Solution Overview
Problem
Existing display devices, such as image projectors, face challenges in miniaturization due to the large size of polarizing beam splitters, making it difficult to incorporate them into slim mobile devices while maintaining image quality and polarization preservation.
Innovation Solution
A polarization-preserving light distributing device using a substrate with total internal reflections and out-coupling features, such as diffractive grooves, to confine and direct light, allowing for a more compact design and improved polarization control, enabling the use of smaller light sources and reduced back focal length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a polarizing beam splitter is used to form polarized illuminating light, then the polarization state is controlled, but the device size becomes large making it difficult to incorporate into slim mobile devices
Solution Approach 1:
The patent combines the light distribution function and polarization control function into a single substrate with out-coupling features, eliminating the need for separate polarizing beam splitters. The substrate integrates total internal reflection for light guiding and diffractive out-coupling features for polarization-selective light extraction, merging multiple optical functions into one compact component.
Solution Approach 2:
The substrate acts as an intermediary optical element that receives light from the light source, confines it via total internal reflection, and selectively couples out polarized light to the display element. This intermediary structure replaces the traditional polarizing beam splitter while maintaining polarization control functionality in a miniaturized form.
2Volume of moving object
If the distance between display element and imaging optics is reduced, then the device becomes more compact, but the back focal length is reduced limiting optical parameter selection
Solution Approach 1:
The patent utilizes the third dimension (substrate thickness) to provide optical path length and focusing capability. The out-coupling features are positioned at specific depths within the substrate, creating effective optical paths that maintain adequate back focal length equivalent while reducing the physical distance between display element and imaging optics.
Solution Approach 2:
The patent changes the optical parameters by using diffractive out-coupling features with specific geometries (period, depth, profile) that control the phase and direction of extracted light. By adjusting these parameters, the system maintains proper focusing capability and optical path length equivalent even with reduced physical spacing.
3Volume of moving object
If a compact light distribution device is used, then the device size is reduced, but the polarization preservation capability must be maintained
Solution Approach 1:
The substrate has different local properties: the bulk substrate provides total internal reflection with high polarization preservation, while the localized out-coupling features provide selective light extraction. The out-coupling features are designed with specific geometries that preferentially couple out one polarization state while maintaining the polarization state of guided light, achieving both compactness and polarization preservation.
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 allows for a more compact display device with increased freedom in optical parameter selection, improved contrast, and the ability to project images with high polarization preservation, suitable for mobile devices.
Implementation Method 1
wherein the in-coupled light beam is confined to the substrate by total internal reflections
Implementation Method 2
a plurality of out-coupling features to form an illuminating light beam by diffracting light of the in-coupled light beam out of the substrate
Implementation Method 3
a display element having a plurality of reflective polarization-rotating pixels arranged to form reflected light beams by reflecting light of the illuminating light beam
Data Source
AI summary
A display device comprises a light source to provide an input light beam, a substrate having an input surface to form an in-coupled light beam by receiving light of the input light beam, wherein the in-coupled light beam is confined to the substrate by total internal reflections, the substrate further comprising a plurality of out-coupling features to form an illuminating light beam by diffracting light of the in-coupled light beam out of the substrate, a display element having a plurality of reflective polarization-rotating pixels arranged to form reflected light beams by reflecting light of the illuminating light beam, and imaging optics to form an image by focusing or collimating light of the reflected light beams transmitted through the out-coupling features.