Substrate-Guided Imaging Lens for Wide Field-of-View Displays
Solution Overview
Problem
Conventional compact optical display devices for head-mounted and head-up displays are bulky, impractical, and suffer from limited field-of-view and eye-motion-box constraints, leading to poor performance and manufacturability issues, especially in applications requiring wide spectral sources and high-quality imaging.
Innovation Solution
A compact optical system utilizing a light-transmitting substrate with a polarizing beam-splitter, collimating reflecting optical elements, and a quarter-wavelength retardation plate, allowing for total internal reflection and efficient coupling of light waves, which enables a wide field-of-view and large eye-motion-box while maintaining a compact form factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional free-space optical modules are used for head-mounted displays, then the system can achieve basic imaging function, but the system becomes larger, heavier, and bulkier
Solution Approach 1:
The patent combines multiple optical functions (collimation, reflection, beam splitting, polarization control) into a single integrated optical element. The collimating lens incorporates reflecting surfaces, beam-splitting functionality, and polarization plates within one compact structure, eliminating the need for separate conventional optical modules and achieving both compactness and high performance
Solution Approach 2:
The patent transitions from conventional three-dimensional free-space optical paths to a two-dimensional planar integrated structure. By embedding optical functions within a planar substrate, the system achieves compact form factor suitable for head-mounted displays while maintaining imaging quality
2Adaptability or versatility
If the field-of-view of the system is increased, then the viewing capability is improved, but the optical module becomes larger and bulkier
Solution Approach 1:
The patent employs an aspheric collimating lens design that dynamically optimizes light ray paths across different viewing angles. The aspheric surfaces and strategically positioned reflecting surfaces enable the lens to maintain collimation quality across a wide field-of-view without requiring increased physical size
Solution Approach 2:
The patent changes the geometric parameters of the collimating lens, specifically using aspheric surfaces with carefully controlled curvatures and positions. This allows the lens to handle a wide range of incident angles from the display panel while maintaining compact dimensions
3Volume of moving object
If compact optical solutions are implemented, then the form factor is reduced, but the eye-motion-box becomes very small and performance becomes sensitive to movements
Solution Approach 1:
The patent uses aspheric curvatures in the collimating lens to expand the eye-motion-box. The carefully designed curved surfaces redirect light rays to maintain a larger acceptable viewing area, allowing sufficient pupil motion for comfortable reading while keeping the overall module compact
Solution Approach 2:
The patent performs preliminary optimization of the optical path design, with the aspheric collimating lens pre-configured to accommodate eye movements. The lens surfaces are designed in advance to redirect rays appropriately across the expected range of eye positions, eliminating sensitivity to small movements
4Ease of manufacture
If conventional optical modules are used, then basic imaging is achieved, but the system is impractical for head-mounted applications due to weight and bulk
Solution Approach 1:
The patent integrates multiple optical components into a single manufacturable element, combining the collimating lens with reflecting surfaces and beam-splitting functionality. This integration simplifies manufacturing processes and reduces the total weight compared to assembling multiple separate conventional optical 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
The solution provides a compact, high-quality imaging system with a wide field-of-view and large eye-motion-box, accommodating large eye movements and supporting wide spectral sources, including conventional white-light, thus enhancing the performance and practicality of head-mounted and head-up displays.
Implementation Method 1
an optical element for coupling light waves into said substrate by total internal reflection
Implementation Method 2
at least one quarter-wavelength retardation plate, wherein said quarter-wavelength retardation plate is located between at least a portion of said major surface of said substrate and said reflecting optical element
Implementation Method 3
said reflecting surface reflects light waves which are coupled inside said substrate into said collimating reflecting optical element
Data Source
Figure 1~3
Figure 4a~4c
Figure 5~6
AI summary
There is provided an optical system, including a substrate having a major surface and edges, an optical element for coupling light into the substrate by total internal reflection, a reflecting surface carried by the substrate, a retardation plate and a reflecting optical element. The retardation plate is located between a portion of the major surface of the substrate and the reflecting optical element. A second light-transmitting substrate having two major surfaces parallel to each other and two edges is including a second optical element for coupling light waves into said second substrate by internal reflection and at least one partially reflecting surface located in said second substrate, which surface is non-parallel to the major surfaces of said second light-transmitting substrate. Said second light-transmitting substrate is being positioned adjacent to said first substrate such that optical light waves which are coupled out of the first substrate are coupled by said second optical element into said second substrate by total internal reflection.