Folded Optical Path for Compact Head-Mounted Display
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Solution Overview
Problem
Conventional head-mounted display devices are limited by their size and weight, which restricts their application and user satisfaction.
Innovation Solution
The design incorporates a display module with a first optical element that receives and transmits image light, and a second optical element that receives the transmitted light and sends it back, creating a folded optical path to prevent light leakage and enhance optical performance in a compact form factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a conventional head-mounted display device is designed with standard optical components, then the optical function is achieved, but the device size and weight increase
Solution Approach 1:
The patent introduces a folded optical path that bends light at angles rather than using a straight linear path. The optical path folds back on itself multiple times within the compact housing, allowing the optical components to be arranged in a three-dimensional configuration that reduces the overall device footprint and weight while maintaining full optical functionality
Solution Approach 2:
The patent arranges optical components in a nested configuration where the folded optical path allows multiple optical elements to be positioned within each other's spatial envelopes. The light path enters and exits optical elements in a sequence that enables compact nesting, with each component efficiently utilizing the space created by the folded path geometry
2Volume of moving object
If the display module emits light in directions other than perpendicular to the optical element, then compact form factor is achieved, but light leakage may occur
Solution Approach 1:
The patent tilts the backlight at a predetermined angle relative to the optical element surface normal. This intentional misalignment, which could cause light leakage in conventional designs, is converted into a benefit by the folded optical path configuration. The folded path captures and redirects these angled rays through multiple reflections and refractions, ensuring they ultimately reach the correct exit pupil position while preventing direct leakage to the user's eye
Solution Approach 2:
The folded optical path acts as an intermediary system between the tilted backlight and the final image output. By introducing multiple optical interfaces (reflections, refractions) along the folded path, the system mediates the angled light rays from the tilted backlight, transforming their direction and ensuring they contribute to the intended image rather than causing leakage
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 results in a thinner and lighter head-mounted display device with improved optical efficiency and reduced optical artifacts, enhancing user experience and application versatility.
Implementation Method 1
a first optical element positioned relative to the display module for receiving the first image light from the display module and transmitting the first image light
Implementation Method 2
a second optical element separate from and positioned relative to the first optical element so that the second optical element receives the first image light transmitted through the first optical element and sends the received first image light back toward the first optical element
Implementation Method 3
The display module includes at least a first region from which the first image light is provided in one or more directions other than a direction perpendicular to the first optical element
Implementation Method 4
This allows the light from the backlight to illuminate the second optical element at a pre-tilted angle, which can prevent or reduce any light leaked by the second optical element from propagating toward an eye of a viewer
Data Source
AI summary
A display device includes a display module for providing first image light. The display device also includes a first optical element for receiving and transmitting the first image light from the display module. The display module includes a region from which the first image light is provided in directions other than a direction perpendicular to the first optical element. The display device further includes a second optical element so that the second optical element receives the first image light transmitted through the first optical element and sends the received first image light back toward the first optical element as second image light. The first optical element receives the second image light from the second optical element and sends the second image light back toward the second optical element, and the second optical element receives and transmits the second image light from the first optical element.