Imaging Lens Compact Design via Movable Second Group
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Solution Overview
Problem
There is a demand for an imaging lens with a short total length that maintains favorable optical performance, which existing lens systems fail to achieve effectively.
Innovation Solution
The proposed imaging lens configuration consists of a first lens group, a stop, a second lens group with positive refractive power, and a third lens group, where the second lens group moves during focusing, and the third lens group remains stationary, incorporating specific lens arrangements and conditional expressions to optimize refractive powers and curvatures, ensuring reduced total length and improved optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the lens system uses a conventional configuration to maintain optical performance, then the total length of the lens system becomes long, but if the total length is reduced, optical performance deteriorates
Solution Approach 1:
The lens system is divided into four distinct lens groups (G1, G2, G3, G4) with specific refractive power configurations. The second lens group G2 is further segmented to include at least two negative lenses, allowing independent optimization of each segment's contribution to aberration correction and focal length control, enabling compact design without sacrificing optical performance
Solution Approach 2:
The patent applies specific parameter constraints including conditional expressions for focal length ratios (e.g., -0.5 < f2/f1 < -0.1, 0.6 < f2R/f2 < 1.4), radius of curvature ratios (e.g., -0.3 < (R2rB-R2rA)/(R2rB+R2rA) < 0.3), and Abbe number relationships. These parameter optimizations enable the compact lens configuration to achieve desired optical performance by precisely controlling refractive powers and material properties
2Ease of operation
If the second lens group moves during focusing, then focusing capability is achieved, but the mechanical complexity and potential alignment issues increase
Solution Approach 1:
The focusing function is extracted and assigned specifically to the second lens group G2, which contains at least two negative lenses. By isolating the focusing mechanism to this specific group rather than moving the entire lens system or multiple groups, the mechanical complexity is reduced while maintaining effective focusing capability
Solution Approach 2:
The second lens group G2 is designed as a movable unit that shifts along the optical axis during focusing operations, while the other lens groups remain stationary. This dynamic configuration allows the lens system to adapt its focal plane position without requiring complex multi-group coordination mechanisms
3Device complexity
If the third lens group remains stationary during focusing, then the structure is simplified, but the ability to correct aberrations across different focus distances may be limited
Solution Approach 1:
The aberration correction function is merged into the stationary third lens group G3, which consists of one negative lens and one positive lens. This group works in conjunction with the movable second lens group to provide continuous aberration correction across different focus distances, even though G3 itself does not move during focusing
Solution Approach 2:
The third lens group G3 is optimized with specific parameter constraints including focal length ratios (e.g., -0.8 < f3/f < 0.2, 0.5 < f3p/f3 < 1.0) and radius of curvature relationships (e.g., -0.2 < (R3nB-R3nA)/(R3nB+R3nA) < 0.2). These parameter optimizations enable the stationary group to effectively correct aberrations across varying focus positions
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 allows for a significant reduction in the lens system's total length while maintaining excellent optical performance by effectively correcting aberrations and optimizing refractive powers, resulting in a compact and high-performance imaging lens.
Implementation Method 1
a second lens group having a positive refractive power... During focusing, at least the second lens group moves along an optical axis
Implementation Method 2
a first lens group having a negative refractive power... a second lens group having a positive refractive power... a third lens group consisting of one negative lens and one positive lens
Data Source
AI summary
An imaging lens consists of, in order from the object side, a first lens group, a stop, a positive second lens group, and a third lens group. During focusing, at least the second lens group moves and the third lens group does not move. The second lens group includes at least two negative lenses. The third lens group consists of one negative lens and one positive lens.