Near-Eye Projection Optics With Nested Light-Field Layout
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Solution Overview
Problem
Existing light-field image projection systems are bulkier and not suitable for wearable devices due to the required volume of optical elements, leading to lower image quality and higher compensation needs, which is a challenge for applications like smart glasses.
Innovation Solution
A near-eye image projection system with a pin-light source, spatial light modulator (SLM), and optimized illumination and imaging optics that utilize a combination of collimating, deflecting, and waveguide elements to create a compact design capable of forming foveal and peripheral pin-light images, allowing for foveation capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional light-field projection systems use multiple optical elements separated by sufficient volume of transparent medium, then the required characteristics of structured incident light and projected light-field image are achieved, but the device becomes bulkier and unsuitable for wearable applications
Solution Approach 1:
The patent implements a nested optical architecture where the illumination optics and imaging optics are integrated in a compact configuration. The SLM is positioned within the optical paths of both illumination and imaging systems, allowing multiple optical functions to be nested within a minimal volume. This nesting enables the system to achieve light-field projection with high image quality while maintaining a form factor suitable for wearable devices.
Solution Approach 2:
The patent utilizes freeform optical surfaces that operate in three-dimensional space to achieve optical transformation in a compact footprint. By employing freeform illumination optics and freeform imaging optics with complex curved surfaces, the system accomplishes light field shaping and image projection without requiring linear separation of optical elements, effectively utilizing spatial dimensions to reduce overall device volume while maintaining optical performance.
2Volume of moving object
If higher power optical elements such as lenses with shorter focal length are used to shrink the optics, then the device size is reduced, but the quality of illumination light structure deteriorates and higher compensation requirements arise due to optical artifacts
Solution Approach 1:
The patent employs freeform optical surfaces with precisely controlled surface profiles that allow for compact focal lengths while maintaining high illumination quality. By changing the geometric parameters of the optical surfaces from traditional spherical or aspherical shapes to freeform configurations, the system achieves short focal lengths without the optical artifacts and image degradation that would normally result from such compact design.
Solution Approach 2:
The patent replaces traditional mechanical optical element arrangements (multiple separated lenses and mirrors requiring linear space) with a integrated freeform optical system where the optical surfaces are directly formed on compact substrates. This substitution eliminates the need for substantial separation volume between optical elements while maintaining the required illumination structure quality through precise freeform surface engineering.
3Reliability
If traditional optical elements are used, then sufficient volume for light propagation is available, but the device form factor becomes too large for wearable applications
Solution Approach 1:
The patent employs sequential spatial light modulation where the SLM dynamically changes the illumination pattern for different views over time. This dynamic approach allows the system to achieve light-field projection with sufficient light propagation distance for high image quality while keeping the physical optical path length short, as the different view directions are generated temporally rather than requiring simultaneous spatial separation.
Solution Approach 2:
The patent segments the light field into multiple discrete views that are sequentially modulated by the SLM. Each view receives optimized illumination and imaging with sufficient propagation distance for high quality, while the overall device maintains a short form factor because the different views are generated in sequence rather than requiring simultaneous spatial accommodation of all view paths.
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 system achieves a small form factor suitable for wearable devices while maintaining high image quality by using a compact design that supports foveation, enabling applications in augmented and mixed reality glasses.
Implementation Method 1
a pin-light source generating a plurality of incident light beams
Implementation Method 2
a SLM configured to modulate said plurality of incident light beams and generate a plurality of modulated light beams
Implementation Method 3
The illumination optics defines a first optical path followed by the incident light beams in a direction from the first plane to the second plane, and a second optical path followed by the incident light beams in a direction from the third plane to the fourth plane
Implementation Method 4
The imaging optics defines a third optical path followed by the modulated light beams in a direction from the second plane to the first plane, and a fourth optical path followed by the modulated light beams in a direction from the first plane to the second plane
Implementation Method 5
the optical combiner comprises a foveal combiner configured to reflect the foveal modulated light beams and project foveal image light beams towards a foveal eye-box
Implementation Method 6
the optical combiner comprises a foveal combiner configured to reflect the foveal modulated light beams and transmit natural light from the real world towards the eye-box
Data Source
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Figure 1c
AI summary
Near-eye image projection system comprising a pin-light source generating incident light beams; a SLM generating modulated light beams forming pin-light images at a first plane; illumination optics, in a third plane, delivering the incident light beams from the pin-light source to the SLM; and imaging optics delivering the modulated light beams along a projection axis, in a fourth plane, to an eye-box region in a second plane parallel to the first plane. The third and fourth planes being substantially perpendicular to the first plane. The illumination optics defines a first optical path from the first plane to the second plane and a second optical path from the third plane to the fourth plane. The imaging optics defines a third optical path from the second plane to the first plane and a fourth optical path from the first plane to the second plane. A wearable device comprising the near-eye image projection system is also described.