Ocular Optical System Forming Gate Mark Positioning
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Solution Overview
Problem
Head-mounted displays (HMDs) using ocular optical systems with polarized light suffer from optical distortion due to birefringence, particularly near the forming gate of resin lenses, leading to reduced light efficiency and image quality issues.
Innovation Solution
The ocular optical system includes a forming gate mark positioned at the apex of the image display region relative to the optical axis, with a non-optical effective region between the optical effective region and the forming gate, reducing the impact of birefringence by distancing the forming gate from the optical path and increasing the cross-sectional area of the forming gate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a resin lens is used to reduce weight, then the weight of the ocular optical system is reduced, but birefringence occurs near the forming gate causing degradation in image quality
Solution Approach 1:
The patent extracts the harmful forming gate region from the optical effective region by positioning the forming gate outside the optical effective region. This separation removes the source of birefringence-induced image quality degradation while preserving the lightweight advantage of resin lenses.
Solution Approach 2:
The patent applies local quality by creating a non-optical effective region with different properties between the optical effective region and the forming gate. This region acts as a buffer zone that isolates the optical effective region from birefringence effects while maintaining overall system lightweight design.
2Manufacturing precision
If the forming gate is positioned away from the optical effective region, then birefringence impact is reduced, but the forming gate may still be in a direction of maximum field angle causing image quality degradation
Solution Approach 1:
The patent applies asymmetry by strategically positioning the forming gate in a specific angular direction (within ±30 degrees from the vertical direction in the horizontal cross-section) that corresponds to regions of lower visual sensitivity. This asymmetric placement minimizes the impact of residual birefringence on the observer's visual experience.
3Manufacturing precision
If a non-optical effective region is provided between the optical effective region and forming gate, then birefringence is reduced in the optical effective region, but the ocular optical system becomes more complex
Solution Approach 1:
The patent merges the non-optical effective region with the existing lens structure by integrating it into the lens periphery rather than adding a separate component. This approach creates the necessary buffer zone for birefringence isolation while maintaining a compact, unified optical system structure.
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 minimizes the influence of birefringence on image quality, reducing light unevenness and ghost light, while maintaining a lightweight and thin ocular optical system capable of displaying wide-angle images effectively.
Implementation Method 1
ocular optical systems in which optical paths are folded using polarized light
Implementation Method 2
birefringence at the time of forming (hereinafter referred to as birefringence for simplicity) may occur
Data Source
AI summary
To provide an image display device that is advantageous in terms of a reduction in deterioration in image quality due to birefringence in an optical element of an ocular optical system in which polarized light is used, the image display device includes an ocular optical system including a polarization element and configured to guide light from an image display element toward an eyeball of an observer. The ocular optical system includes at least one optical element that has a forming gate mark in a part of an outer periphery. The forming gate mark is disposed in a direction of an apex of an image display region of the image display element with respect to a point on an optical axis of the ocular optical system in a cross section perpendicular to the optical axis of the ocular optical system.