Freeform Waveguide Prism for Wider-Field Light Field HMDs
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Solution Overview
Problem
Conventional head-mounted displays (HMDs) suffer from visual discomfort due to vergence-accommodation conflicts, lacking correct focus cues and causing conflicts between accommodation and convergence cues.
Innovation Solution
A high-performance HMD based on integral imaging that incorporates a freeform waveguide prism and a vari-focal element to achieve high lateral and longitudinal resolutions, large depth of field, and increased viewing angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a 2D microdisplay is used as the image source, then the device complexity is reduced, but the visual comfort deteriorates due to vergence-accommodation conflicts
Solution Approach 1:
The patent transitions from a 2D microdisplay to a 3D light field display using a microlens array. Each microlens element creates multiple virtual images at different depths by refracting light from the 2D display, adding the depth dimension to the display. This allows the system to maintain the simplicity of a 2D display while achieving 3D rendering capabilities that resolve vergence-accommodation conflicts by providing correct focus cues at various depths.
Solution Approach 2:
The microlens array acts as an intermediary between the 2D microdisplay and the user's eye. It processes the light from the 2D display by refracting it through multiple lenses, creating multiple virtual images at different depths. This intermediary component enables the system to provide depth information and correct focus cues without requiring a complex 3D display hardware, thus resolving the contradiction between device simplicity and visual comfort.
2Manufacturing precision
If conventional HMD optics are used, then the manufacturing precision is easier to achieve, but the field of view is limited
Solution Approach 1:
The patent divides the display into multiple independent microlens elements, each responsible for a specific portion of the field of view. Each microlens creates its own virtual image, effectively segmenting the overall display into multiple smaller display units. This segmentation allows each microlens to be manufactured with standard precision while collectively providing an expanded field of view, as the sum of all individual microlens fields covers a broader area than a single conventional lens could provide.
3Device complexity
If a fixed virtual image plane is used, then the optical system is simpler, but the adaptability deteriorates because focus cues cannot be rendered at multiple distances
Solution Approach 1:
The patent creates a dynamic display system where the virtual image plane is not fixed but can be positioned at multiple different depths. By using the microlens array to refract light from the 2D display, the system can dynamically adjust the perceived depth of virtual images based on the content being displayed. This dynamic capability allows the optical system to adapt to different viewing scenarios and provide appropriate focus cues at various distances without requiring a completely complex variable focal length optical system.
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 provides a HMD with improved visual comfort by accurately rendering focus cues, addressing vergence-accommodation conflicts, and enhancing the viewing experience with increased field of view and resolution.
Implementation Method 1
a first freeform optical surface disposed to receive and refract light into the body of the prism
Implementation Method 2
a second freeform optical surface disposed to receive the refracted light from the first freeform optical surface and reflect the light into the body of the prism to provide an intermediate image within the body of the prism
Implementation Method 3
a third freeform optical surface disposed to receive the light from the intermediate image and total internally reflect the light into the body of the prism
Data Source
AI summary
Freeform waveguide prism with compound surface and use with head-mounted light field display with integral imaging and relay group.