Imaging Lens Weight Reduction via Segmented Focusing Groups
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Solution Overview
Problem
Existing imaging lenses face challenges in achieving a balance between reducing the weight of focusing lens groups while maintaining a small F number and high performance, particularly in cinematic applications where the aperture is completely open, and in achieving fast focusing operations without compromising image quality.
Innovation Solution
The design incorporates a first lens group with fixed positive refractive power, a second lens group with moving positive refractive power, and a third lens group that is fixed during focusing, with specific configurations of lenses and conditional formulas to optimize focal lengths, Abbe's numbers, and stop positions to minimize weight and maximize performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the F number is reduced to achieve fast aperture, then imaging speed is improved, but sagittal comatic flare increases
Solution Approach 1:
The lens is divided into multiple lens groups (first lens group with positive refractive power, second lens group with negative refractive power, third lens group with positive refractive power) that can be independently optimized. Each group is designed to contribute specifically to correcting different types of aberrations while maintaining the fast aperture capability.
Solution Approach 2:
Different regions of the lens system are assigned different optical characteristics. The first lens group uses lenses with specific refractive indices and curvatures optimized for reducing comatic flare, while the second and third groups provide additional correction. Each lens element has tailored optical properties to address specific aberration issues in its location.
2Ease of operation
If focusing is performed by feeding out the entire system, then focusing capability is achieved, but the weight of focusing lens groups becomes heavy
Solution Approach 1:
The focusing function is isolated to a specific second lens group with negative refractive power, while the first and third lens groups remain stationary. This segmentation allows the focusing mechanism to be lightweight and localized rather than requiring the entire lens system to move.
Solution Approach 2:
The second lens group acts as an intermediary focusing element that can be moved independently to achieve focus adjustment. This intermediary group has optimized optical properties that allow effective focusing with minimal weight, serving as a mediator between the stationary lens groups and the imaging element.
3Weight of moving object
If a single cemented lens is used for focusing, then the weight is reduced, but the F number becomes slow (2.8)
Solution Approach 1:
The lens system is segmented into multiple groups with different refractive powers distributed across three lens groups. The first lens group provides positive refractive power for light convergence, the second group provides negative refractive power for focusing adjustment, and the third group provides additional positive refractive power. This distribution allows maintaining a fast F number while keeping individual lens groups lightweight.
Solution Approach 2:
The optical parameters including refractive indices, curvatures, and spacing between lens groups are optimized to achieve a balance between speed and weight. The specific combination of positive and negative lens groups with tailored optical properties enables fast aperture performance without requiring heavy focusing mechanisms.
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 results in a high-performance imaging lens with a small F number and reduced focusing lens group weight, enabling fast and high-quality focusing operations while minimizing spherical and chromatic aberrations.
Implementation Method 1
a first lens group having a positive refractive power which is fixed during focusing operations; a second lens group having a positive refractive power which moves during focusing operations
Data Source
AI summary
An imaging lens includes: a first lens group having a positive refractive power which is fixed during focusing operations; a second lens group having a positive refractive power which moves during focusing operations; and a third lens group which is fixed during focusing operations. The first lens group includes a 1a lens group having a positive refractive power, an aperture stop, and a 1b lens group having a positive refractive power. The 1a lens group includes a positive lens, a negative meniscus lens, a negative meniscus lens, a positive meniscus lens, a negative lens, a positive lens, a negative lens, and a cemented lens formed by a positive lens and a negative lens.