Optical System Lens Shape Inversion for Eye Relief
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Solution Overview
Problem
Conventional head mount display (HMD) optical systems face challenges in securing sufficient eye relief at the periphery due to the protrusion of lens surfaces, which limits the field of view and optical performance.
Innovation Solution
The optical system includes a front group with a first lens having positive refractive power and a rear group with multiple lenses, featuring transmissive reflective surfaces to correct aberrations and ensure eye relief, with specific inequalities governing the sag amount and focal lengths to optimize performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a lens surface closest to the observation surface has a concave shape, then the outer periphery of the lens protrudes toward the observation side, but it becomes difficult to secure sufficient eye relief at the outer periphery
Solution Approach 1:
The patent inverts the conventional concave lens surface design by using a convex lens surface closest to the observation surface. This inversion allows the lens periphery to recede rather than protrude, thereby securing sufficient eye relief at the outer periphery while maintaining the desired optical shape characteristics
Solution Approach 2:
The patent changes the sag amount parameter of the lens surface to satisfy a specific inequality relationship (0.05 ≤ SagR1LF/F ≤ 0.30), where SagR1LF is the maximum sag amount of the lens surface closest to the observation surface and F is the focal length. This parameter optimization resolves the contradiction between lens shape and eye relief by controlling the degree of surface curvature
2Length of stationary object
If the lens outer periphery protrudes toward the observation side, then the lens can be made thinner, but sufficient eye relief cannot be secured at the periphery
Solution Approach 1:
The patent applies local quality by differentiating the lens surface characteristics at different locations. The lens surface closest to the observation surface is designed with specific convex curvature characteristics in the peripheral region, while maintaining appropriate thickness through the inequality constraint on sag amount, thereby achieving both thinness and sufficient eye relief at the periphery
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 achieves a wide field of view and high optical performance while ensuring sufficient eye relief, correcting aberrations and maintaining image quality across the entire viewing area.
Implementation Method 1
a front group having a first lens G1 having positive refractive power
Implementation Method 2
A surface closest to the pupil surface of the rear group is a first transmissive reflective surface HM1, and a surface closest to the display surface of the rear group is a second transmissive reflective surface HM2
Data Source
AI summary
An optical system is configured to guide a light beam from a display surface to a pupil surface. The optical system includes, in order from a pupil surface side to a display surface side, a front group having a first lens having positive refractive power, and a rear group having a plurality of lenses. A surface closest to the pupil surface of the rear group is a first transmissive reflective surface, and a surface closest to the display surface of the rear group is a second transmissive reflective surface. A predetermined inequality is satisfied.