Folded Optical Lens Assembly for Lightweight Head-Mounted Displays
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Solution Overview
Problem
Current head-mounted displays are heavy and have poor image quality.
Innovation Solution
An optical lens assembly with a configuration of lenses and optical elements that fold the light path, reducing the number of lenses and improving image quality by optimizing lens parameters such as focal lengths, radii of curvature, and thicknesses, while using absorptive and reflective polarizers and phase retarders to enhance image quality and field of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple lenses are used to improve image quality, then image quality is improved, but device weight and size increase
Solution Approach 1:
The patent combines multiple optical functions into fewer lens elements. Specifically, it uses only three lenses (first lens with positive refractive power, second lens with negative refractive power, and third lens with positive refractive power) while integrating polarizing filters and phase retarders into the optical path to achieve both image quality improvement and weight reduction compared to conventional multi-lens designs.
Solution Approach 2:
The patent introduces a folded optical path design where light reflects off a reflective polarizer, effectively adding an optical dimension without increasing physical device size. This allows complex optical processing to occur within a compact form factor, improving image quality without proportionally increasing device volume.
2Reliability
If multiple lenses are used to improve image quality, then image quality is improved, but device size increases
Solution Approach 1:
The patent merges multiple optical functions into three lenses plus auxiliary optical elements (polarizing filters, phase retarders). This consolidation achieves superior image quality through optimized light control while maintaining a compact device volume, avoiding the need for numerous separate lens elements that would increase size.
Solution Approach 2:
The folded optical path using reflective polarizer allows the light to traverse a longer effective optical path within a shorter physical distance. This dimensional optimization enables complex image quality enhancement without proportionally increasing device volume.
3Weight of moving object
If the number of lenses is reduced to decrease weight, then device weight is reduced, but image quality deteriorates
Solution Approach 1:
The patent carefully optimizes specific parameters of the three lenses including refractive power signs (positive, negative, positive), radii of curvature (R1, R2, R5, R6), thicknesses (CT1, CT2, CT3), and focal lengths (f1, f2, f3) to achieve superior image quality with fewer elements. These parameter optimizations compensate for the reduced number of lenses while maintaining light control effectiveness.
Solution Approach 2:
The patent introduces intermediate optical elements (absorptive polarizer, reflective polarizer, phase retarder) that mediate light processing between the three lenses. These intermediaries enhance image quality by controlling polarization and phase properties of light, compensating for the reduced lens count while keeping device weight low.
4Reliability
If optical elements are added to improve image quality, then image quality is improved, but device complexity increases
Solution Approach 1:
The patent designs the three lenses to perform multiple optical functions simultaneously (focusing, field of view control, aberration correction) rather than requiring separate dedicated elements for each function. The polarizing filters and phase retarders also serve multiple purposes including polarization control, light path folding, and image quality enhancement, reducing overall system complexity despite adding optical elements.
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 reduces the weight and size of the device while providing better image quality and a larger field of view, addressing the issues of heaviness and image quality in existing head-mounted displays.
Implementation Method 1
an absorptive polarizer (that is, a first absorptive polarizer)
Implementation Method 2
a reflective polarizer
Implementation Method 3
a phase retarder (that is, a first phase retarder)
Implementation Method 4
a first lens with positive refractive power
Implementation Method 5
a second lens with negative refractive power
Implementation Method 6
a third lens with positive refractive power
Data Source
AI summary
An optical lens assembly includes, an optical element group; and in order from a visual side to an image source side: a first lens with positive refractive power, a second lens with refractive power, a third lens with refractive power, and an image source-side surface of the third lens being convex in a paraxial region thereof, and a partial-reflective-partial-transmissive element. Wherein the optical element group is disposed between the first lens and the third lens, and includes, in order from the visual side to the image source side: an absorptive polarizer, a reflective polarizer and a phase retarder. The optical lens assembly may become lightweight and have good image quality when satisfying a specific condition.