Freeform Head Mounted Display Optical System Design
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Solution Overview
Problem
Conventional head-mounted displays (HMDs) are limited by cost, size, weight, field of view, and efficiency due to their optical systems, which restrict their practical and leisure applications.
Innovation Solution
A freeform head-mounted display system incorporating a microdisplay, field lenses, and a freeform combiner, where the optical system is designed to provide high-resolution images with adjustable settings and a compact profile using materials like EP5000 and Zeonex E8R for the lenses, and a reflective or holographic combiner for efficient image delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional optical systems are used in HMDs, then the system structure is well-established and manufacturable, but the device suffers from limited field of view, increased weight, and reduced efficiency
Solution Approach 1:
The optical system is divided into multiple specialized components: a microdisplay unit, freeform lenses with specific curvature profiles, and a combiner element. Each segment is optimized for its specific function, allowing the overall system to achieve a wider field of view without proportionally increasing weight.
Solution Approach 2:
Freeform lenses with non-spherical, aspheric surfaces are employed to correct optical aberrations and expand the effective field of view. The curved surfaces enable light routing that flat or simple spherical lenses cannot achieve, providing broader angular coverage while maintaining compact form factor.
2Productivity
If conventional optical systems are used in HMDs, then the design is simpler and easier to manufacture, but the device efficiency and resolution are limited
Solution Approach 1:
Freeform aspheric lenses replace conventional spherical lenses to correct optical aberrations and improve image quality across the entire field of view. The complex curved surfaces enable more efficient light routing and higher resolution imaging, compensating for the increased manufacturing complexity.
Solution Approach 2:
The patent replaces complex mechanical adjustment mechanisms with optically engineered freeform surfaces that inherently correct for viewing angle and focus variations. This substitution of mechanical complexity with optical design complexity improves efficiency while maintaining manufacturability.
3Volume of moving object
If conventional optical systems are used in HMDs, then the device structure is compact, but the overall system size and weight remain excessive for practical applications
Solution Approach 1:
The optical components are arranged in a nested configuration where the microdisplay is positioned within the focal length of the freeform lenses, and the combiner element integrates with the eyepiece structure. This nesting allows multiple optical functions to be packed into a minimal volume while using lightweight materials.
Solution Approach 2:
The combiner element is implemented as a thin, partially transparent reflective surface that can be integrated into lightweight eyepiece structures. This thin-film approach replaces bulk optical components, reducing both volume and weight while maintaining optical performance.
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 system offers improved efficiency, reduced weight, and enhanced field of view, enabling more versatile applications while maintaining user interaction with the real world, such as in augmented reality and tactical displays.
Implementation Method 1
a reflective or holographic combiner for efficient image delivery
Implementation Method 2
a reflective or holographic combiner for efficient image delivery
Implementation Method 3
one or more field lenses positioned to receive the image light from the microdisplay and form a curved intermediate image
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
An optical apparatus for a near-eye display (100) includes a microdisplay (101, 201) to emit image light and one or more field lenses (103, 105, 203, 205) positioned to receive the image light from the microdisplay (101, 201). The one or more field lenses (103, 105, 203, 205) have a combined optical power to form a curved intermediate image (207). A freeform combiner (209), having an eyeward side and an external side, is positioned to receive the image light from the one or more field lenses (103, 105, 203, 205) and reflect the image light. The curved intermediate image (207) is formed between the freeform combiner (209) and the one or more field lenses (103, 105, 203, 205).