Eyepiece Lens Groups for Aberration Correction and Eye Relief
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Solution Overview
Problem
Existing ocular lenses face challenges in providing a sufficient eye relief and effective aberration correction for large angle of view while maintaining compactness and avoiding increased lens diameter and overall length.
Innovation Solution
The ocular lens design includes a first lens group with a meniscus form, a second lens group with a convex surface facing the viewing eye side, and a third lens group with positive refractive power, where the object-side focal plane of the third lens group is positioned between the second and third lens groups, and specific conditions are met for the focal lengths and refractive powers of these groups to ensure adequate aberration correction and compactness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the apparent field of view of an ocular lens is increased, then the viewing angle is improved, but the eye relief becomes insufficient and aberrations worsen
Solution Approach 1:
The ocular lens is divided into multiple lens groups (first lens group with negative refractive power, second lens group with positive refractive power, and third lens group with positive refractive power) arranged in sequence. This segmentation allows each group to contribute differently to the overall optical performance, enabling large apparent field of view while maintaining adequate eye relief and correcting aberrations.
Solution Approach 2:
Each lens group is designed with specific local optical properties: the first lens group has negative refractive power to expand the field of view, the second lens group has positive refractive power to correct aberrations, and the third lens group has positive refractive power to maintain eye relief. The focal lengths and positions of these groups are optimized to achieve local quality improvements that collectively resolve the contradiction.
2Ease of operation
If the focal length of the positive lens group on the viewing eye side is increased to secure sufficient eye relief, then the eye relief is improved, but the lens diameter increases due to the divergence effect of the negative lens component
Solution Approach 1:
The positive refractive power needed for eye relief is segmented between the second lens group and the third lens group. The second lens group (with positive refractive power) is positioned to correct aberrations, while the third lens group (also with positive refractive power) is positioned to maintain eye relief. This segmentation allows the focal length of individual positive lens groups to be optimized without requiring excessive diameter, as the positive refractive power is distributed across multiple groups rather than concentrated in one large lens.
3Manufacturing precision
If the ratio of the focal length of the negative lens group to the positive lens group is closer to 1:1, then the Petzval sum is reduced and field curvature aberration is corrected, but the apparent field of view is limited to at most about 60 degrees
Solution Approach 1:
The ocular lens is divided into three lens groups with different refractive power characteristics. The first lens group (negative refractive power) and second lens group (positive refractive power) can be designed with focal lengths having a ratio close to 1:1 to reduce the Petzval sum and correct field curvature aberration. The third lens group (positive refractive power) is then added to extend the apparent field of view beyond the 60-degree limitation, achieving both good aberration correction and large field of view.
Solution Approach 2:
Different lens groups are assigned different local optical functions: the first and second lens groups focus on correcting field curvature aberration through their 1:1 focal length ratio, while the third lens group focuses on expanding the apparent field of view. This local quality differentiation allows the system to achieve multiple objectives simultaneously.
4Ease of operation
If the focal length of the entire ocular lens is increased, then the eye relief is improved, but the overall length and lens diameter increase, losing compactness
Solution Approach 1:
The positive refractive power required for adequate eye relief is segmented between the second lens group and the third lens group. This segmentation allows the ocular lens to achieve sufficient eye relief without requiring a single long-focal-length lens that would increase the overall length. The distributed positive refractive power enables compact design while maintaining eye relief.
Solution Approach 2:
The third lens group is specifically designed with positive refractive power to provide the local optical function of extending eye relief. By concentrating this function in a dedicated lens group rather than increasing the focal length of the entire ocular lens, the design achieves adequate eye relief while maintaining compact overall dimensions.
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 design enables ocular lenses to provide a large angle of view with sufficient eye relief while preventing increases in lens diameter and overall length, effectively correcting aberrations and maintaining compactness.
Implementation Method 1
a first lens group G1 having a negative refractive power
Implementation Method 2
a second lens group G2 having a positive refractive power
Implementation Method 3
a third lens group G3 having a positive refractive power
Data Source
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AI summary
The invention provides an ocular lens well corrected for aberrations through a sufficiently large angle of view and having a sufficient eye relief while ensuring avoidance of increasing the overall length and suppression of an increase in lens diameter, and provides an optical device including this ocular lens. An ocular lens 3 includes, in order from an object side, a first lens group G1 including a first lens component G1A in meniscus form having a convex surface facing the object side, a second lens group G2 including a lens component L21 having a convex surface facing a viewing eye side, and a third lens group G3 having a positive refractive power. An object-side focal plane I of the third lens group G3 is positioned between the second lens group G2 and the third lens group G3. When f represents the focal length of the entire system; and f12 represents the combined focal length of the first lens group G1 and the second lens group G2, a condition shown by the following expression: is satisfied.