Compact Projection Optics Layout for Head-Mounted Displays
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Solution Overview
Problem
Existing display apparatuses face challenges in reducing the overall size and complexity of their optical systems, particularly in head-mounted displays and augmented reality glasses, due to the large dimensions and arrangement of optical components like polarization beam splitters and prisms.
Innovation Solution
The proposed display apparatus incorporates an optical function unit with a width smaller than the effective modulation area of the display element, utilizing a positive refractive power lens closer to the display element, and strategically arranging optical elements to converge light beams, thereby reducing the size of the projection optical system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional optical systems use polarization beam splitters and prisms, then the optical path can be established, but the overall size and complexity of the optical system becomes large
Solution Approach 1:
The patent combines multiple optical functions (beam splitting, polarization separation, light guiding) into a single integrated optical function unit. This unit integrates the polarization beam splitter and light guiding functions, eliminating the need for separate prisms and reducing the overall number of optical components while maintaining reliable optical path establishment
Solution Approach 2:
The optical function unit is designed to perform multiple functions simultaneously: it acts as a polarization beam splitter, a light guide, and an optical path separator. This multi-functional design reduces device complexity by replacing multiple specialized components with a single universal optical unit
2Reliability
If conventional optical systems use large optical components, then the optical path can be established, but the width and length of the optical function unit become large
Solution Approach 1:
The patent reconfigures the optical path arrangement by utilizing the effective modulation area dimensions of the display element. The optical function unit is designed with width equal to or smaller than the effective modulation area width, and length equal to or smaller than the effective modulation area length, optimizing the spatial arrangement in both dimensions to reduce overall system size
3Volume of moving object
If the width of the optical function unit is reduced, then the device size is minimized, but the arrangement of optical elements becomes more constrained
Solution Approach 1:
The patent applies different optical properties to different regions of the optical function unit. The unit has a first region for guiding illumination light to the display element and a second region for guiding image light to the projection side, with each region optimized for its specific function. This local optimization allows compact arrangement while maintaining proper optical element positioning
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 more compact display apparatus by minimizing the width and length of the optical function unit and projection optical system, enhancing portability and reducing aberrations while maintaining image quality.
Implementation Method 1
an optical element having positive refractive power disposed closer to the display element than the optical function unit
Data Source
AI summary
A display apparatus includes a light source, a display element configured to modulate illumination light from the light source to generate image light, and an optical system including an optical function unit configured to guide the illumination light to the display element and guide the image light to a projection side. In a first direction parallel to an effective modulation area of the display element, a width of the optical function unit is smaller than or equal to a width of the effective modulation area.