Observation Optical System Aberration Control
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Solution Overview
Problem
Conventional observation optical systems for head mount displays face challenges in maintaining high optical performance with a wide field of view while minimizing aberration variation as eye relief changes, often resulting in increased field curvature and astigmatism, especially when the pupil rotates.
Innovation Solution
The proposed observation optical system consists of a first lens with positive refractive power, a second lens with negative refractive power, and a third lens with positive refractive power, where the focal lengths satisfy the conditional expression 0.40 < f1 - f2 × f3 < 0.80, which helps in mildly bending peripheral light flux and correcting field curvature and astigmatism, ensuring realism is maintained even when the eye relief changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the observation optical system uses a strong telephoto configuration to bend peripheral light flux strongly, then the refractive power is increased, but field curvature and astigmatism increase in wide field of view portions
Solution Approach 1:
The observation optical system is divided into multiple lens units (first through fourth lens units) with alternating positive and negative refractive powers. Each lens unit contributes differently to light bending, allowing the system to achieve high refractive power while distributing and correcting optical aberrations across multiple elements rather than relying on a single strong lens.
Solution Approach 2:
The patent specifies precise focal length relationships between lens units (0.40 < f1/|f2| < 0.80 and 0.50 < f3/|f4| < 1.50) to optimize the balance between refractive power and aberration control. By carefully controlling the ratio of focal lengths and arranging lens units at specific intervals, the system maintains high power while correcting field curvature and astigmatism.
2Power
If the observation optical system increases refractive power at high incidence height positions, then light gathering ability is improved, but variation of field curvature and astigmatism increases when eye relief changes
Solution Approach 1:
The optical system is designed to dynamically adapt to different eye relief conditions through its multi-lens configuration. The alternating positive and negative lens units work together to maintain stable optical performance across a range of eye relief distances, reducing sensitivity to changes in observer position.
Solution Approach 2:
The negative refractive power lens units act as intermediaries that counterbalance the strong light-bending effect of positive lens units. This intermediary action stabilizes the optical path, reducing variation in field curvature and astigmatism when eye relief changes, while still maintaining high overall refractive power.
3Device complexity
If the observation optical system uses fewer lenses to reduce weight, then device complexity is reduced, but lateral chromatic aberration and field curvature are not sufficiently corrected
Solution Approach 1:
The system segments the optical function across four lens units rather than using a single complex lens or fewer elements. This segmentation allows each lens unit to be optimized for specific functions (positive for convergence, negative for divergence and aberration correction), achieving superior optical performance with a manageable number of elements.
Solution Approach 2:
The optical system uses a composite arrangement of lens materials with different refractive properties (positive and negative refractive power lens units). This composite structure enables effective correction of lateral chromatic aberration and field curvature by combining the optical effects of different lens types in a coordinated configuration.
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 high optical performance with a wide field of view and reduces aberration variation, enhancing the realism of the observed image by adequately correcting field curvature and astigmatism, even when the pupil rotates.
Implementation Method 1
a first lens having a positive refractive power; a second lens having a negative refractive power; and a third lens having a positive refractive power
Data Source
AI summary
In order to obtain an observation optical system which has high optical performance while having a wide field of view, and can easily reduce variation of aberration at the time when an eye relief has changed, the present invention provides an observation optical system which is used for an observer to observe an image displayed on an image display surface, and includes in order from an observation side to an image displaying surface side: a first lens having a positive refractive power; a second lens having a negative refractive power; and a third lens having a positive refractive power, wherein a focal length f1 of the first lens, a focal length f2 of the second lens and a focal length f3 of the third lens are each appropriately set so as to satisfy the conditional expression of:0.40<f1-f2×f3<0.80.