Double Faceted Optics for Lightweight HMDs
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Solution Overview
Problem
Traditional head-mounted display (HMD) devices are bulky and heavy due to the use of a single conventional refractive optical element, which results in inefficiencies as much of the generated light does not reach the eye box, making it difficult to achieve a high-quality, wide field of view image in a lightweight and cost-effective design.
Innovation Solution
Employing two or more optical sub-assemblies, where the first sub-assembly focuses light and the second sub-assembly, comprising multiple planarly arranged micro lenses, collimates the light to provide a large field of view and high resolution images, while conserving resources and reducing weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single conventional refractive optical element is used, then the device structure is simple, but the device becomes heavy and bulky
Solution Approach 1:
The patent divides the optical assembly into multiple discrete optical elements (first lens, second lens, third lens) arranged in sequence. Each lens has a specific function: the first lens focuses light, the second lens collimates light, and the third lens forms the final image. This segmentation allows each element to be optimized for its specific function, reducing the overall weight and size compared to a single large lens while maintaining optical performance.
2Device complexity
If a single lens is used to both focus and collimate light, then the device is simpler, but light efficiency decreases as much light never reaches the eye box
Solution Approach 1:
The patent separates the focusing and collimating functions into distinct optical elements. The first lens focuses light from the display, the second lens collimates the focused light, and the third lens forms the final image in the eye box. This functional segmentation ensures that light is efficiently directed through each stage, maximizing the amount of light that reaches the eye box compared to a single lens design where light paths are less controlled.
3Device complexity
If a single large lens is used, then the optical functionality is integrated, but the device becomes physically bulky
Solution Approach 1:
The patent replaces a single large lens with multiple smaller lenses arranged in a compact sequence. Each lens has a smaller individual aperture, allowing them to be positioned closer together and reducing the overall volume of the optical assembly. The segmented design maintains the necessary optical path length for focusing and collimating while minimizing the physical footprint of the device.
4Ease of manufacture
If traditional optical assemblies are used, then the design is conventional and easier to manufacture, but the field of view and image quality are limited
Solution Approach 1:
The patent uses multiple standard lens elements that can be manufactured using conventional techniques, maintaining ease of manufacture. However, the specific arrangement and optical properties of each lens (focusing, collimating, image-forming) are optimized to achieve superior field of view and image quality compared to traditional single-lens designs. The segmented approach allows for better control of optical parameters while using manufacturable components.
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 configuration allows for a lightweight, cost-effective HMD device that delivers high-quality images with a large field of view and eye box, optimizing light delivery and reducing the physical bulk of the device.
Implementation Method 1
a first sub-assembly positioned proximate to the light engine and configured to focus the light toward an eye box
Implementation Method 2
a second sub-assembly positioned distal to the light engine and configured to collimate at least some of the light toward the eye box to form an image in the eye box
Data Source
AI summary
This document relates to head mounted display devices. In one example the head mounted display device includes a light engine including an array of individually controllable pixels that can be energized to emit light. The example also includes an optical assembly physically aligned with the light engine and including a set of focusing elements facing toward the light engine and a different set of focusing elements facing away from the light engine.