Negative-Lead Zoom Lens With Compact Inner-Focus Aberration Correction
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Solution Overview
Problem
Negative lead type zoom lenses face challenges in correcting aberration fluctuations during focusing, particularly in inner focus types, and struggle with miniaturization of the focus lens unit while maintaining high optical performance.
Innovation Solution
The zoom lens design includes a first lens unit with three or more negative lenses, a second lens unit with a single positive lens that moves during focusing, and a rear group with multiple lens units, adhering to specific refractive power and distance ratios to minimize aberrations and lens size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a negative lead type zoom lens is used to achieve wide angle of view and long back focus, then the angle of view and back focus are improved, but aberration correction becomes difficult and optical performance deteriorates
Solution Approach 1:
The patent applies asymmetry by configuring the first lens unit with multiple negative lenses (including at least one meniscus lens with convex surface toward object) and the second lens unit with multiple positive lenses, creating an asymmetric power distribution that corrects aberrations while maintaining wide angle of view. This asymmetric configuration balances the negative lead structure's inherent aberrations.
Solution Approach 2:
The patent changes parameters by specifying precise focal length ratios (0.45 < fL1/fL2 < 0.55), curvature radius ratios (0.85 < R1/R2 < 1.15), and Abbe number constraints (20 < νdG1P < 40). These parameter changes optimize the optical system to correct aberrations while maintaining the negative lead configuration's wide angle benefits.
2Volume of moving object
If the focus lens unit is miniaturized to reduce size, then the lens size is reduced, but aberration correction capability deteriorates
Solution Approach 1:
The patent segments the focusing function by dedicating the second lens unit (with multiple positive lenses) specifically for focusing operations, while the first lens unit handles wide angle correction. This segmentation allows the focus lens unit to be miniaturized without compromising overall aberration correction, as the first lens unit compensates for aberrations.
Solution Approach 2:
The patent changes parameters by constraining the focal length ratio (0.45 < fL1/fL2 < 0.55) and curvature radius ratio (0.85 < R1/R2 < 1.15), which allows the second lens unit to be miniaturized while maintaining its aberration correction capability through optimized optical parameters.
3Speed
If inner focus mechanism is used for high-speed focusing, then focusing speed is improved, but aberration fluctuations increase
Solution Approach 1:
The patent segments the optical system into a first lens unit for wide angle correction and a second lens unit for focusing. This segmentation isolates the focusing operation to the second lens unit, allowing high-speed inner focusing without causing aberration fluctuations in the entire system, as the first lens unit stabilizes the optical path.
Solution Approach 2:
The patent changes parameters by optimizing the focal length ratio (0.45 < fL1/fL2 < 0.55) and curvature radius ratio (0.85 < R1/R2 < 1.15), which stabilizes aberrations during high-speed focusing by creating a balanced power distribution that compensates for focusing-induced aberration changes.
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 a compact, high-performance zoom lens with wide angle of view and effective aberration correction, allowing for miniaturization and improved optical characteristics.
Implementation Method 1
a second lens unit having positive refractive power and including a positive lens GP that moves from the object side to the image side during focusing from infinity to a close distance
Implementation Method 2
a first lens unit having negative refractive power and including, in order from the object side to the image side, three or more negative lenses... a second lens unit having positive refractive power
Data Source
AI summary
A zoom lens includes, in order from an object side to an image side, a first lens unit having negative refractive power, a second lens unit having positive refractive power, and a rear group including one or more lens units. Distances between adjacent lens units change during zooming. The first lens unit includes, in order from the object side to the image side, three or more negative lenses. The second lens unit consists of a positive lens configured to move from the object side to the image side during focusing from infinity to a close distance. A predetermined condition is satisfied.