Wavelength-Tuned Varifocal Display for Compact VAC Reduction
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Solution Overview
Problem
Conventional varifocal displays increase the size and weight of head-mounted displays, which limits their applications and user experience due to vergence-accommodation conflict.
Innovation Solution
A combination of a diffractive optical element and a tunable light source that changes focal length based on wavelength, enabling compact and lightweight varifocal displays by redirecting light of different wavelengths to different focal planes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional varifocal displays are used to reduce vergence-accommodation conflict, then user experience is improved, but device size and weight increase
Solution Approach 1:
The patent combines multiple optical functions (varifocal adjustment and Vergence-Accommodation Conflict resolution) into a single integrated optical system using a diffractive optical element, eliminating the need for separate mechanical adjustment mechanisms and reducing overall device weight while maintaining user experience benefits
Solution Approach 2:
The patent replaces traditional mechanical varifocal adjustment mechanisms with a diffractive optical element that achieves focal length changes through wavelength-dependent diffraction, eliminating heavy mechanical components while providing the same varifocal functionality to reduce Vergence-Accommodation Conflict
2Ease of operation
If conventional varifocal displays are used to reduce vergence-accommodation conflict, then user experience is improved, but device dimensions increase
Solution Approach 1:
The diffractive optical element provides varifocal functionality through optical diffraction rather than mechanical movement, dramatically reducing the physical length of the optical path while maintaining the ability to adjust focal length for different viewing distances, thus improving user experience without increasing device dimensions
Solution Approach 2:
The patent changes the optical parameter (focal length) by utilizing wavelength-dependent diffraction through the diffractive optical element, allowing focal adjustment without physical movement of components, thereby maintaining compact device dimensions while providing varifocal capabilities to reduce Vergence-Accommodation Conflict
3Weight of moving object
If diffractive optical element with wavelength tuning is used, then device size and weight are reduced, but optical complexity increases
Solution Approach 1:
The diffractive optical element performs multiple functions simultaneously: it provides varifocal adjustment, resolves Vergence-Accommodation Conflict, and enables wavelength-based focal length control, consolidating what would otherwise require multiple separate optical components and reducing overall optical system complexity despite the advanced functionality
Solution Approach 2:
The patent utilizes the wavelength-dependent properties of the diffractive optical element to control focal length, transforming a potentially complex mechanical adjustment system into a simpler optical parameter control mechanism where focal length is determined by light wavelength rather than physical component movement
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
Reduces the size and weight of head-mounted displays while reducing vergence-accommodation conflict, enhancing user experience by allowing images to be perceived at varying distances without increasing device dimensions.
Implementation Method 1
A diffractive optical element redirects light of a first wavelength to a first focal plane and redirects light of a second wavelength to a second focal plane
Data Source
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AI summary
A display device includes a diffractive optical element and a tunable light source operable in different states including a first state and a second state. The tunable light source provides first light having a first wavelength while the tunable light source is in the first state and second light having a second wavelength, distinct from the first wavelength, while the tunable light source is in the second state. The first wavelength and the second wavelength correspond to a first color band. The diffractive optical element is positioned to receive and redirect the first light and receive and redirect the second light. The diffractive optical element has a first focal length for the first light and a second focal length, distinct from the first focal length, for the second light.