Inner Focus Imaging Lens with Moving Negative Group
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Solution Overview
Problem
Existing inner focus type imaging lenses face challenges in achieving high-speed focusing while effectively correcting various aberrations, with either large lens groups leading to slow focusing or single lens movements resulting in inadequate aberration suppression.
Innovation Solution
An inner focus type imaging lens configuration comprising a first lens group with positive refractive power, a second lens group with negative refractive power, and a third lens group with positive refractive power, where only the second lens group moves during focusing, and specific conditional expressions are satisfied to optimize refractive powers, Abbe numbers, and partial dispersion ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple lenses are moved during focusing, then fluctuations in various aberrations can be corrected, but focusing speed decreases
Solution Approach 1:
The patent divides the lens system into three distinct lens groups (first with positive refractive power, second with negative refractive power, and third with positive refractive power). During focusing, only the second lens group moves while the first and third groups remain stationary. This segmentation allows the moving portion to be minimized for high-speed focusing while the combined optical power of all three groups works together to correct various aberrations effectively.
2Speed
If only one lens is moved during focusing, then focusing speed increases, but fluctuations in various aberrations cannot be suppressed
Solution Approach 1:
The patent assigns specific optical properties to each lens group: the first and third lens groups have positive refractive power while the second lens group has negative refractive power. The second lens group is specifically designed as the focusing element with optimized refractive power to minimize aberration fluctuations during movement. This local optimization of optical properties allows effective aberration control with minimal lens movement.
3Reliability
If various aberrations are corrected at higher level, then imaging quality improves, but device complexity increases
Solution Approach 1:
The patent combines three lens groups with different refractive powers (positive, negative, and positive) into a unified optical system. The first, second, and third lens groups work together synergistically to correct multiple types of aberrations simultaneously. This merging approach achieves high-level aberration correction without requiring each individual group to be overly complex, as the collective optical power distribution handles the correction tasks efficiently.
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 enables high-speed focusing while satisfactorily correcting various aberrations, ensuring high-quality video capture by minimizing lens movement and aberration fluctuations.
Implementation Method 1
a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a third lens group G3 having a positive refractive power. During focusing from an object at infinity to a closest object, only the second lens group G2 moves in a direction of an optical axis
Data Source
AI summary
The imaging lens includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power. During focusing, only the second lens group moves in the direction of the optical axis. A lens closest to the object side in the first lens group and a lens adjacent to the lens on the image side have positive refractive powers, and the second lens group includes two or three lenses. Further, predetermined Conditional Expressions (1), (2), (3a), and (3b) are satisfied.