Fresnel Lens Dynamic Draft Reducing Optical Artifacts
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Solution Overview
Problem
Conventional head-mounted display devices are bulky and heavy due to complex optics, and Fresnel lenses, while lighter, suffer from diffractions and optical artifacts, limiting their use in imaging applications.
Innovation Solution
A lens with a dynamic draft Fresnel structure design, where the draft angle of each Fresnel structure varies based on its distance from the lens center, reducing interaction with incoming light and minimizing optical artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If Fresnel lenses are used to reduce size and weight, then the lens becomes lighter and more compact, but optical artifacts and diffractions increase
Solution Approach 1:
The patent applies local quality by making the draft angle of Fresnel structures vary based on their radial distance from the lens center. Peripheral structures have different draft angles compared to central structures, allowing each region to be optimized for its specific optical requirements. This gradient approach reduces diffraction artifacts while preserving the lightweight Fresnel design.
Solution Approach 2:
The patent changes the geometric parameter (draft angle) of the Fresnel structures dynamically based on radial position. By varying this parameter across different regions of the lens, the invention optimizes light transmission characteristics to minimize optical artifacts while maintaining the overall lightweight structure.
2Object-generated harmful factors
If conventional lenses are used to minimize optical artifacts, then image quality improves, but device size and weight increase
Solution Approach 1:
Instead of using a uniform conventional lens design, the patent applies local quality by implementing variable draft angles in different radial zones. This allows the lens to achieve conventional-level optical performance in critical regions while maintaining the weight advantages of Fresnel structures in peripheral areas.
Solution Approach 2:
The patent introduces dynamics by making the draft angle parameter vary continuously or in steps across the lens surface based on radial distance. This dynamic parameter adjustment allows the lens to adapt its optical characteristics to local requirements, achieving a balance between artifact reduction and weight minimization.
3Ease of manufacture
If uniform draft angle is used in all Fresnel structures, then manufacturing is simplified, but optical performance degrades due to increased diffraction
Solution Approach 1:
The patent applies local quality by implementing different draft angles for Fresnel structures at different radial positions. This differentiation optimizes optical performance by reducing diffraction artifacts in peripheral regions while maintaining manufacturability through a systematic gradient approach rather than complete complexity.
Solution Approach 2:
The patent introduces dynamics to the manufacturing process by varying the draft angle parameter across the lens surface. This dynamic parameter change, while increasing manufacturing complexity slightly, significantly improves optical performance and justifies the additional manufacturing effort through enhanced image quality.
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 compact, lightweight head-mounted display devices with reduced optical artifacts, enhancing user experience by minimizing the visibility of optical imperfections and improving image quality.
Implementation Method 1
The draft angle of the respective Fresnel structure is between a first angle and a second angle, the first angle corresponding to a direction of a ray, in the first medium, transmitted from a reference off-axis position through the respective Fresnel structure toward a reference pupil and the second angle corresponding to a direction of the ray, in the optically transparent substrate, transmitted from the reference off-axis position through the respective Fresnel structure toward the reference pupil
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
A lens includes an optically transparent substrate having a first lens surface and a second lens surface opposite to the first lens surface. The first lens surface includes a plurality of Fresnel structures. A respective Fresnel structure of the plurality of Fresnel structures includes a slope facet and a draft facet. The respective Fresnel structure of the plurality of Fresnel structures is characterized by a representative pitch. The representative pitch of the respective Fresnel structure is based on a distance of the respective Fresnel structure from a reference axis of the lens. A display device that includes the lens and an electronic display coupled with the lens for outputting light through the lens and a method for transmitting light from an electronic display toward the lens are also described.