Inner Focus Lens with Moving Second Group for Compact Size
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Solution Overview
Problem
There is a demand for an inner focus type imaging lens with small size and favorable optical performance, which existing lens systems have not adequately addressed.
Innovation Solution
The proposed solution involves an inner focus type imaging lens configuration comprising a first lens group with positive refractive power, a second lens group with positive refractive power that includes at least four lenses and a stop, and a third lens group, where only the second lens group moves during focusing, satisfying specific conditional expressions to ensure compact size and optimal optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional lens systems are used, then optical performance can be maintained, but the lens size becomes large
Solution Approach 1:
The lens is divided into three distinct lens groups (first lens group with positive refractive power, second lens group with positive refractive power, and third lens group), where only the second lens group moves during focusing. This segmentation allows the lens to achieve compact size while maintaining optical performance by optimizing the movement characteristics of each group independently.
Solution Approach 2:
The patent applies specific conditional expressions that define parameter ranges for the lens configuration, including relationships between total optical length TL, focal length f, maximum image height Y, and the positions of lens groups. By controlling these parameters within specified ranges, the lens achieves both small size and favorable optical performance.
2Length of moving object
If the total optical length is shortened, then compactness is improved, but aberration suppression becomes difficult
Solution Approach 1:
The second lens group, which moves during focusing, is configured with at least four lenses including specific positive and negative lenses with defined refractive powers. This local optimization of the focusing group's structure enables effective aberration suppression even when the total optical length is shortened, as the specific lens configuration within the moving group compensates for aberrations.
Solution Approach 2:
The patent implements an inner focus mechanism where only the second lens group moves during focusing, while the first and third lens groups remain stationary. This dynamic configuration allows the lens to maintain short total optical length while the moving second lens group actively corrects aberrations through its movement and specific optical design.
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 an imaging lens with a small size and favorable optical performance, effectively suppressing aberrations and achieving a short total optical length, suitable for applications in digital cameras and other imaging devices.
Implementation Method 1
a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3. During focusing from an object at infinity to a closest object, only the second lens group G2 moves
Data Source
AI summary
The imaging lens consists of, in order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a positive refractive power, and a third lens group. During focusing, only the second lens group moves. The second lens group includes at least four lenses. The imaging lens satisfies predetermined conditional expressions.