Spatially Multiplexed Lens for Multi-Depth HMD Displays
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Solution Overview
Problem
Conventional optical systems in Head Mounted Displays (HMDs) are limited by size, weight, field of view, and efficiency, which restrict their practical and leisure applications due to their inability to effectively present computer-generated images in a wide field of view and multiple depths simultaneously.
Innovation Solution
The use of spatially multiplexed lenses, such as off-axis spatially multiplexed lenses (OASMLs) that incorporate multiple sub-lenses with different focal lengths to direct image light towards the same eyeward region, allowing for the presentation of multiple images at different depths within a wider field of view, while maintaining transparency to allow external scene light to reach the user's eye.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional optical systems are used in HMDs, then the device structure is simple, but the field of view is limited and multiple depths cannot be presented simultaneously
Solution Approach 1:
The optical combiner is divided into multiple discrete optical elements (first optical element, second optical element, third optical element) with different focal lengths, each responsible for directing light at different depths. This segmentation allows the system to present multiple virtual images at different depths simultaneously while maintaining a compact form factor, resolving the contradiction between expanded field of view and device complexity.
Solution Approach 2:
The patent introduces the focal length dimension as an additional degree of freedom by using optical elements with varying focal lengths (first focal length, second focal length, third focal length). This dimensional approach enables the system to encode depth information in the focal length parameter, allowing multiple depths to be presented within the same physical space without increasing overall device complexity.
2Loss of information
If multiple images at different depths are presented, then depth perception is enhanced, but the device size and weight increase
Solution Approach 1:
Multiple optical elements with different focal lengths are merged into a single integrated optical combiner assembly that fits within the HMD frame. This consolidation allows the system to provide enhanced depth perception through multiple virtual images at different depths while avoiding the weight penalty of separate, distributed optical components, thus resolving the contradiction between depth perception and device weight.
3Loss of information
If multiple images at different depths are presented, then depth perception is enhanced, but the device size increases
Solution Approach 1:
The multiple optical elements are nested within the HMD frame structure, with each optical element positioned to utilize the available space efficiently. The first optical element, second optical element, and third optical element are arranged in a nested configuration that maximizes the use of internal volume while maintaining the focal length differentiation needed for multi-depth presentation, thus resolving the contradiction between depth perception and device volume.
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
This solution enhances the field of view and depth perception in HMDs, enabling the presentation of multiple images at different depths within a wider field of view without increasing the size or weight of the display, thereby improving the user's experience in augmented reality applications.
Implementation Method 1
a first sub-lens of the spatially multiplexed lens has a first focal length and is configured to receive image light from the display module and direct a first portion of the image light toward an eyeward region of a user
Data Source
AI summary
An optical combiner includes an off-axis spatially multiplexed lens optically coupled to receive image light and direct the image light in an eye-ward direction. The off-axis spatially multiplexed lens includes a first sub-lens multiplexed with a second sub-lens. The first sub-lens and the sub-lens are configured to direct the image light to designated eyeward-regions.