Alvarez Lens and Diffractive Optical Element for Dynamic Depth in AR
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Solution Overview
Problem
Existing augmented reality (AR) systems face challenges in presenting 3D virtual content at varying depths, leading to discomfort due to fixed depth planes, which do not mimic the natural human eye's focus changes when viewing objects at different distances.
Innovation Solution
The AR system employs a diffractive optical element (DOE) and an Alvarez lens with transmissive plates having specific surface sag profiles, allowing for the generation of collimated light rays that appear to come from varying depth planes by lateral translation of the DOE relative to the lens assembly, and an eye-tracking module to adjust based on the user's vergence, ensuring virtual content is projected at depths that align with the user's focus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fixed depth planes are used in AR systems, then system complexity is reduced, but user comfort deteriorates due to inability to mimic natural eye focus changes
Solution Approach 1:
The patent applies the Dynamics principle by implementing a variable focus mechanism that allows the optical system to dynamically adjust the focal plane of virtual content. The Alvarez lens assembly enables continuous variation of optical power, allowing the system to mimic natural eye accommodation by shifting focus between different depth planes, thereby improving user comfort without requiring complete system redesign
Solution Approach 2:
The patent employs parameter changes by modifying the optical power of the Alvarez lens assembly through lateral translation of its components. By changing the relative position of the lens elements, the system varies the focal length and optical characteristics to deliver content at different depths, enabling dynamic focus adjustment while maintaining a relatively simple overall system architecture
2Ease of operation
If variable focal planes are implemented to mimic natural eye focus, then user comfort is improved, but device complexity increases
Solution Approach 1:
The system uses a dynamic Alvarez lens assembly where lateral translation of lens components enables continuous focus adjustment. This dynamic mechanism allows the system to adapt to different viewing conditions and content depths, providing natural eye accommodation without requiring multiple discrete optical systems
Solution Approach 2:
The Alvarez lens assembly serves multiple functions: it acts as both a focusing element and a depth control mechanism. By laterally translating the lens components, the same optical assembly can deliver virtual content at various depths and adjust for different user prescriptions, reducing the need for separate specialized components
3Measurement precision
If Alvarez lens with cubic function surfaces is used, then optical precision for collimated light generation is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent uses parameter changes by laterally translating the Alvarez lens components to adjust the optical path and compensate for manufacturing variations. By varying the relative position of the cubic surface elements, the system can optimize the collimation of light rays and achieve precise focal plane delivery despite tolerances in surface sag fabrication
Solution Approach 2:
The system incorporates feedback mechanisms including eye tracking and vergence sensing that provide real-time information about user viewing conditions. This feedback enables dynamic adjustment of the Alvarez lens position to compensate for both manufacturing variations and individual user differences, ensuring optimal optical precision in actual use
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 approach provides a more realistic and comfortable AR experience by allowing virtual content to be perceived at varying depths, reducing user discomfort and enhancing the 3D perception by aligning virtual content with the user's natural focus, making the system less bulky and aesthetically pleasing.
Implementation Method 1
a diffractive optical element (DOE) to receive the light associated with the one or more frames of image data and direct the light to the user's eyes
Implementation Method 2
the first side being a plano side, and the second side being a shaped side, the second side of the first transmissive plate comprising a first surface sag based at least in part on a cubic function
Data Source
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AI summary
Configurations are disclosed for presenting virtual reality and augmented reality experiences to users. The system may comprise a lens assembly comprising two transmissive plates, a first of the two transmissive plates comprising a first surface sag based at least in part on a cubic function, and a DOE to direct image information to a user's eye; wherein the DOE is placed in between the two transmissive plates of the lens assembly, and wherein the DOE is encoded with the inverse of the cubic function corresponding to the surface sag of the first transmissive plate; such that a wavefront created by the encoded DOE is compensated by the wavefront created by the first transmissive plate, thereby collimating light rays associated with virtual content delivered to the DOE.