Lens System with Cemented Lenses for Aberration Correction
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Solution Overview
Problem
Existing lens systems for high-quality image capture, especially in macro photography, are cumbersome and difficult to handle due to their complexity and sensitivity to focusing adjustments, leading to fluctuations in aberrations and brightness.
Innovation Solution
A lens system comprising a negative-positive-positive-positive refractive power arrangement with cemented lenses and a meniscus lens configuration, where the fourth lens group is fixed relative to the image plane, and the second and third lens groups move to adjust focus, maintaining a constant overall length and minimizing F-number fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a complex lens system is used to correct aberrations, then image quality is improved, but device complexity and weight increase
Solution Approach 1:
The lens system is divided into four distinct lens groups with specific refractive power assignments. Each group is optimized for particular functions: the first group (negative refractive power) handles field curvature and distortion, the second group (positive refractive power) corrects spherical aberration, the third group (positive refractive power) manages chromatic aberration, and the fourth group (positive refractive power) corrects residual aberrations. This segmentation allows each group to be designed and manufactured independently with specialized optimization.
Solution Approach 2:
The lens system employs cemented lenses combining different glass types with complementary optical properties. Specifically, the second lens group uses a cemented lens with a positive meniscus element and a negative element, while the fourth group uses a cemented lens with a negative meniscus element and a positive element. These composite structures leverage the different refractive indices and dispersion characteristics of the glass materials to achieve superior aberration correction.
2Ease of operation
If the lens system is made more compact, then ease of operation is improved, but aberration correction performance may deteriorate
Solution Approach 1:
The lens groups are arranged in a nested configuration where the second and third lens groups are positioned between the first and fourth groups, creating a compact overall structure. The cemented lenses within each group further reduce the total length by eliminating air gaps between adjacent elements. This nested arrangement achieves compactness while preserving the optical path length necessary for aberration correction.
Solution Approach 2:
The lens system utilizes specific curvature radii and thickness parameters optimized for compactness. The fourth lens group includes a meniscus lens with a specific curvature radius ratio (R2/R1 between 0.4 and 2.0) that enables effective aberration correction in a compact form factor. Additionally, the distances between lens groups are carefully controlled to maintain optical performance while minimizing overall length.
3Adaptability or versatility
If the fourth lens group is made movable for focusing, then focus adjustment range is improved, but sensitivity to tolerances increases
Solution Approach 1:
The focusing mechanism is implemented by making the second and third lens groups movable relative to each other along the optical axis, while keeping the first and fourth lens groups fixed. This dynamic arrangement allows the focal length to be adjusted by changing the distance between the movable groups, providing focus adjustment range without requiring the entire lens system to be movable, thereby reducing tolerance sensitivity.
Solution Approach 2:
The third lens group acts as an intermediary between the second lens group and the fourth lens group. When the second lens group moves for focusing, the third lens group mediates the optical interaction, helping to maintain stable aberration characteristics. This intermediary role reduces the direct impact of focusing movements on tolerance-sensitive parameters.
4Adaptability or versatility
If the stop is moved for focusing, then focus adjustment is improved, but brightness fluctuation increases
Solution Approach 1:
The stop is extracted from the movable focusing mechanism and positioned fixedly in the fourth lens group, separate from the second and third lens groups that move for focusing. This extraction ensures that the stop aperture remains constant during focusing operations, preventing brightness fluctuations while still allowing focus adjustment through the movement of other lens groups.
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 allows for stable and easy handling of the lens system, effectively correcting aberrations and maintaining consistent brightness across the focusing range without moving the stop, resulting in high-quality images with reduced complexity and weight.
Implementation Method 1
a cemented lens disposed on the object side of the stop and whose image plane side-surface includes a surface that is concave on the object side, the fourth lens group includes, at a position closest to the object side, a cemented lens which is disposed closest to the image plane side of the stop, and whose object side surface includes a surface that is concave on the image plane side
Implementation Method 2
The fourth lens group may include a meniscus lens that has positive refractive power, is concave on the object side, and is disposed on the image plane side of the cemented lens disposed on the image plane side of the stop
Data Source
Figure 1(a)~1(b)
Figure 2~4
Figure 5(a)~5(b)
AI summary
A lens system (10) for imaging is provided. The lens system (10) includes, in order from the object side (11), a first lens group (G1) that has negative refractive power, a second lens group (G2) that has positive refractive power, a third lens group (G3) that has positive refractive power, a stop (St), and a fourth lens group (G4) that has positive refractive power. The third lens group (G3) includes, at a position closest to the image plane side (12), a cemented lens (B2) that is disposed on the object side (11) of the stop (St) and whose image plane-side (12) surface includes a surface that is concave on the object side (11). The fourth lens group (G4) includes, at a position closest to the object side (11), a cemented lens (B3) that is disposed on the image plane side (12) of the stop (St) and whose object-side surface includes a surface that is concave on the image plane side. A radius of curvature g3er of the surface that is concave on the object side and the radius of curvature g4fr of the surface that is concave on the image plane side satisfy the following condition. 2.5≤g4fr/g2er≤4.0