Eyepiece Optical System Aspherical Surface Design
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Solution Overview
Problem
Existing eyepiece optical systems have limitations in providing a wide viewing angle and maintaining a thin, lightweight design while ensuring proper diopter adjustment and image quality in head-mounted displays.
Innovation Solution
The eyepiece optical system includes a first lens element with a polarizing reflective surface and a second lens element with a partial reflection surface, where the first lens element has an aspherical surface with a convex region on the pupil side, satisfying the condition 0.05 < SagH/BF < 0.25, and a ¼ wave plate for phase delay, facilitating a wide viewing angle and diopter adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If a conventional eyepiece optical system is used, then the overall length can be kept short and thin, but the viewing angle is limited and visual field is restricted
Solution Approach 1:
The patent applies an aspherical surface design to the first lens element, where the sagitta (SagH) satisfies the condition 0.05 < SagH/BF < 0.25. This curved aspherical surface enables light rays from different angles to converge properly at the display surface, achieving a wide viewing angle while maintaining a compact overall length. The aspherical curvature allows the optical system to fold light paths effectively without requiring excessive length.
Solution Approach 2:
The patent introduces a polarizing reflective surface on the first lens element that selectively reflects or transmits light based on polarization state. This adds a dimensional control mechanism that manages light paths in three-dimensional space, enabling the system to achieve wide viewing angles by directing light rays through different spatial dimensions while keeping the physical structure compact.
2Weight of moving object
If the eyepiece optical system is made thinner and lighter, then portability is improved, but diopter adjustment capability and image quality deteriorate
Solution Approach 1:
The first lens element is designed to perform multiple functions simultaneously: it acts as a protective cover, provides diopter adjustment capability through its aspherical surface geometry, enables wide viewing angles, and incorporates polarization control via the polarizing reflective surface. By making this single component multi-functional, the patent achieves reliable diopter adjustment and image quality while maintaining a thin, lightweight structure without requiring additional separate components.
3Area of moving object
If the aspherical surface condition 0.05 < SagH/BF < 0.25 is satisfied, then viewing angle and visual field are improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent establishes a specific parameter range for the aspherical surface sagitta (0.05 < SagH/BF < 0.25) that balances manufacturing feasibility with optical performance. By defining this optimized range rather than requiring extreme precision, the patent enables wide viewing angles and visual field while keeping manufacturing precision requirements at achievable levels. The parameter optimization allows standard manufacturing capabilities to produce the desired 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
This configuration enables a thin, lightweight eyepiece optical system with a wide viewing angle and effective diopter adjustment, enhancing the visual field and image quality in head-mounted displays.
Implementation Method 1
a polarizing reflective surface on a display side, the polarizing reflective surface reflecting or transmitting an incident light beam according to polarization of the incident light beam
Implementation Method 2
a partial reflection surface reflecting a part of the incident light beam and transmitting a remaining part of the incident light beam
Implementation Method 3
The first lens element has an aspherical surface including a convex region on a pupil side, the convex region having a convex shape toward a side opposite to the polarizing reflective surface
Data Source
AI summary
An eyepiece optical system has an optical axis for guiding a light beam between a pupil of a user and a display surface, and includes: a first lens element having, on a display side, a polarizing reflective surface reflecting or transmitting an incident light beam according to polarization of the incident light beam; and a second lens element disposed between the first lens element and the display surface, and having a partial reflection surface reflecting a part of the incident light beam and transmitting a remaining part thereof. The first lens element has, on a pupil side, an aspherical surface including a convex region having a convex shape opposite to the polarizing reflective surface with the optical axis being positioned therein. The aspherical surface satisfies 0.05<SagH/BF<0.25 with a sag amount SagH at a maximum image height of the display surface and a back focus BF of the eyepiece optical system.