Substrate-Guided Optical System for Wide Field-of-View Displays
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Solution Overview
Problem
Conventional compact optical systems for displays, such as head-mounted and head-up displays, face limitations in achieving wide field-of-view and compactness, leading to bulkiness, sensitivity to eye movements, and high manufacturing complexity, while also suffering from chromatic dispersion issues with high-quality holographic displays.
Innovation Solution
The design incorporates a light-transmitting substrate with multiple partially reflecting surfaces that allow for total internal reflection and selective reflection properties, enabling a compact optical system with a wide field-of-view and large eye-motion-box, accommodating large eye movements and supporting high-quality images, and allowing for a compact display source attached to the substrate, reducing chromatic dispersion and enabling operation with wide spectral sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If conventional free-space optical modules are used to increase field-of-view, then the field-of-view increases, but the system becomes larger, heavier and bulkier
Solution Approach 1:
The patent combines multiple optical functions (collimating lens, combiner, beam expander) into a single integrated optical element with multiple surfaces. Each surface performs a specific optical function, allowing the system to achieve wide field-of-view while maintaining compact size and lightweight construction, directly resolving the contradiction between FOV and system weight/size
Solution Approach 2:
The optical element serves multiple functions simultaneously: it acts as a collimating lens on one surface, a combiner on another surface, and a beam expander through its overall structure. This multi-functionality eliminates the need for separate optical components, reducing system weight and size while maintaining wide field-of-view capability
2Duration of action of moving object
If conventional optical designs are used to achieve wide field-of-view, then the field-of-view increases, but the eye-motion-box becomes very small and the system becomes sensitive to eye movements
Solution Approach 1:
By integrating the collimating lens and combiner functions into a single optical element with specifically designed surfaces, the patent creates an optical path that maintains a large eye-motion-box. The integrated design ensures that the optical functions work together to accommodate large eye movements, reducing sensitivity to eye position while maintaining wide field-of-view
3Duration of action of moving object
If conventional HUD designs are used to ensure full combiner illumination, then the field-of-view is adequate, but the display source must be offset a significant distance from the combiner making the system bulky
Solution Approach 1:
The patent merges the display source and combiner into a closely integrated configuration by incorporating the light source directly onto or near the optical element. The optical element's design ensures that light from the closely-positioned source is properly collimated and directed to illuminate the entire combiner surface, eliminating the need for large offset distances while maintaining adequate field-of-view
Solution Approach 2:
The patent utilizes the third dimension (depth/thickness of the optical element) to achieve compact integration. By designing the optical element with specific surface curvatures and thickness variations, it can collimate and direct light from a close-proximity source to cover the entire combiner area, effectively using vertical space to compensate for reduced horizontal/longitudinal distance
4Duration of action of moving object
If high-quality holographic displays are used to achieve wide field-of-view, then the field-of-view increases, but chromatic dispersion becomes a significant issue
Solution Approach 1:
The patent changes the optical parameters of the surfaces (curvature, orientation, reflectivity) to control the path and focus of different wavelengths. By carefully designing these surface parameters, the system achieves wide field-of-view while compensating for chromatic dispersion, ensuring that different colors focus at appropriate points without significant color fringing or distortion
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 results in a highly compact and lightweight optical system with improved image quality and flexibility, capable of accommodating large eye movements and wide field-of-view, while minimizing chromatic dispersion, thus enhancing the practicality and performance of displays in various applications, including head-mounted and head-up displays.
Implementation Method 1
optical means for coupling light into said substrate by total internal reflection
Implementation Method 2
a plurality of partially reflecting surfaces carried by said substrate
Data Source
AI summary
There is provided an optical system, including a mechanical body (110), a light-transmitting substrate (20) having two major surfaces and edges, embedded in the mechanical body, an optical element (90) for coupling light into the substrate by total internal reflection and a plurality of partially reflecting surfaces (22) carried by the substrate, wherein the partially reflecting surfaces are parallel to each other and are not parallel to any of the edges of the substrate. The system also includes an image capturing device (112), a display source (4), and an image-processing unit (114). The image-capturing device (112) is connected via the image-processing unit (114) to the display source (4).