Zoom Lens Aberration Control via Negative-lead Segmentation
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Solution Overview
Problem
Existing zoom lenses with wide angles face challenges in achieving high optical performance and small size while maintaining low variation in imaging magnification during focusing, which leads to issues like aberration correction and background objects entering or leaving the frame during focusing.
Innovation Solution
A zoom lens configuration with a first negative refractive power unit, a second positive refractive power unit, a middle lens group including a focus lens unit with negative refractive power that moves towards the image, and a final positive refractive power unit, along with an aperture stop on the object side, optimized by specific conditional expressions to control focal lengths and transverse magnifications, ensuring reduced aberration variation and compact size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a negative-lead type zoom lens configuration is used to achieve wide angle of view and compact size, then the system size is reduced and wide angle capability is improved, but aberration correction becomes difficult and optical performance deteriorates
Solution Approach 1:
The zoom lens is divided into multiple lens units with specific refractive powers (first negative, second positive, third negative, fourth positive) that can move independently during zooming and focusing operations. This segmentation allows each unit to be optimized for specific functions while maintaining overall compact size and correcting aberrations through coordinated movement.
Solution Approach 2:
The patent employs an asymmetric lens configuration with alternating negative and positive refractive power units in a negative-lead arrangement. This asymmetric design enables wide angle of view while using smaller lens elements, and the asymmetric movement patterns during focusing help correct aberrations that would otherwise be difficult to control in compact wide-angle systems.
2Speed
If inner focus type focusing is implemented using a small lightweight lens unit to achieve high speed focusing, then focusing speed is improved, but variation in aberration during focusing increases
Solution Approach 1:
The third lens unit with negative refractive power serves as an intermediary focusing unit that moves toward the image side during focusing. This intermediate unit helps compensate for aberration variations introduced by the focusing action of other units, maintaining optical performance while enabling high-speed focusing through the lightweight third unit.
Solution Approach 2:
The patent optimizes the refractive power parameters and movement distances of the lens units to maintain aberration correction during focusing. By carefully controlling the change in position parameters of the third lens unit and coordinating it with other units, the system achieves high-speed focusing while minimizing aberration variation.
3Adaptability or versatility
If refractive powers of focus lens unit and final lens unit are not appropriately configured, then design flexibility is improved, but it becomes difficult to achieve reduction in size while maintaining wide angle of view and high optical performance
Solution Approach 1:
The patent establishes specific relationships between the refractive powers of lens units through conditional expressions. The third lens unit has negative refractive power within a specific range relative to the fourth lens unit's positive refractive power, and the focal lengths are constrained to maintain wide angle capability. These parameter constraints enable compact size while the coordinated movement of units provides design flexibility for different zoom ratios and focal length ranges.
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
The solution effectively corrects various aberrations, reduces the size of the focus lens unit, and minimizes variation in image magnification during focusing, enabling high-speed focusing and maintaining optical performance across the zoom range.
Implementation Method 1
a first lens unit having a negative refractive power; a second lens unit having a positive refractive power; a middle lens group including at least one lens unit; and a final lens unit having a positive refractive power
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A zoom lens includes, in order from an object side to an image side: first and second lens units having negative and positive refractive powers, respectively; a middle lens group; and a final lens unit having a positive refractive power, wherein the middle lens group comprises a focus lens unit that has a negative refractive power and moves toward the image side during focusing from infinity to a short distance, the intervals between adjacent lens units vary during at least one of zooming and focusing, and wherein the focal length fimg of the final lens unit, the focal length ff of the focus lens unit, and the focal length fw of the entire system at the wide angle end are appropriately configured.