Folded Optical Module Layout for Low Field Curvature in HMDs
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Solution Overview
Problem
Existing optical modules in augmented and virtual reality devices face challenges in achieving clear imaging in both central and peripheral fields of view due to stringent requirements for miniaturization, leading to difficulties in eliminating field curvature and maintaining imaging quality.
Innovation Solution
A three-lens optical module design with controlled optical path differences between peripheral and central optical paths, incorporating a beam splitter, phase retarder, and polarization reflection film, to ensure simultaneous clear imaging on the same image plane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the display size is reduced to achieve miniaturization, then the device size and weight are reduced, but the optical module must provide larger focal power and bending angle which deteriorates imaging quality in peripheral field of view
Solution Approach 1:
The optical module is divided into multiple lens groups (first lens group with positive focal power, second lens group with negative focal power, third lens group with positive focal power) that work together to correct optical aberrations. This segmentation allows each group to contribute differently to the overall optical function, enabling correction of field curvature while maintaining compact form factor
Solution Approach 2:
Different regions of the optical system are assigned different functions: the first lens group handles central field imaging with positive focal power, while the second and third lens groups provide negative and positive focal power respectively to correct peripheral field curvature. This local differentiation of optical properties enables simultaneous optimization of central and peripheral imaging quality
2Adaptability or versatility
If the focal power and bending angle are increased to accommodate smaller display, then the field of view is maintained, but field curvature becomes difficult to eliminate which deteriorates peripheral imaging quality
Solution Approach 1:
The patent optimizes specific optical parameters including the focal powers of different lens groups (positive, negative, and positive), the optical path difference ratio (controlling it to be 0.25-0.5 times the central optical path), and the arrangement of polarization components. These parameter changes enable correction of field curvature while maintaining the required field of view angle
Solution Approach 2:
The beam splitter and polarization components (polarization beam splitter, phase retardation film) act as intermediaries that manipulate the optical path of light rays. These components enable precise control of light propagation, allowing correction of peripheral field curvature by adjusting the optical path difference between central and peripheral rays
3Length of stationary object
If a two-lens folded optical path solution is used, then the optical path is compact, but it is difficult to achieve simultaneous clear imaging in both central and peripheral fields of view
Solution Approach 1:
The optical system is segmented into three distinct lens groups with alternating positive and negative focal powers, arranged in a folded configuration. This segmentation provides enough degrees of freedom to correct both central and peripheral field imaging, achieving clear simultaneous imaging that a two-lens system cannot provide
Solution Approach 2:
The patent employs a folded optical path design where the light path bends back on itself using beam splitters and polarization components. This dimensional manipulation of the optical path allows compact arrangement of multiple lens groups in a limited space, achieving complex optical correction functions within a compact form factor
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 design achieves low field curvature and enhanced imaging quality, providing a better visual experience by ensuring clear imaging in both central and peripheral fields of view.
Implementation Method 1
a beam splitter is provided between the second lens and the first lens
Implementation Method 2
a first phase retarder and a polarization reflection film are provided on either side of the third lens
Implementation Method 3
a first phase retarder and a polarization reflection film are provided on either side of the third lens
Data Source
AI summary
Embodiments of the present disclosure provide an optical module and a head mounted display; wherein, the optical module comprises a first lens, a second lens, and a third lens provided sequentially, a beam splitter is provided between the second lens and the first lens, and a first phase retarder and a polarization reflection film provided on either side of the third lens. The first lens is configured for transmitting incident light and an optical path difference between an optical path at a 1.0 aperture of the first lens and a central optical path of the first lens is 0.25˜0.5 times of the central optical path.