Zoom Lens Aberration Control via Segmented Groups
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Solution Overview
Problem
Conventional wide-angle zoom lens systems face challenges in minimizing aberration variation during focusing, particularly in mirrorless cameras, due to strong negative optical power in the first lens group leading to distortion and coma aberrations, and varying lateral chromatic aberration with focusing distance.
Innovation Solution
A zoom lens system with a specific optical power arrangement of negative, positive, positive, and negative lens groups, where the second lens group is divided into sub-groups with a positive and negative lens element, and the fourth lens group has negative optical power to correct aberrations without aspherical elements, and the focal length ratios are optimized to reduce aberration variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a retro-focus lens type with strong negative optical power in the first lens group is used to achieve wide-angle and long back focus, then wide-angle capability and long back focus are improved, but distortion aberration and coma aberration increase significantly
Solution Approach 1:
The lens system is divided into multiple lens groups (first through fourth lens groups) with alternating optical powers. The first lens group has negative optical power for wide-angle capability, while the second and fourth lens groups have positive optical power to correct aberrations. This segmentation allows each group to perform its specific function without compromising overall system performance.
Solution Approach 2:
Different lens groups are assigned specific optical power characteristics tailored to their functional requirements. The first lens group uses strong negative power for wide-angle field of view, while the fourth lens group uses positive power specifically for correcting distortion and coma aberrations. This local optimization of optical properties resolves the contradiction between wide-angle capability and aberration control.
2Object-affected harmful factors
If the last lens group has negative optical power to cancel distortion and coma aberration, then aberration correction is improved, but lateral chromatic aberration varies greatly during focusing from infinity to close distance
Solution Approach 1:
The second lens group is divided into two sub-groups (second-a lens group with positive power and second-b lens group with negative power). This segmentation allows the positive sub-group to focus on correcting lateral chromatic aberration while the negative sub-group assists in correcting distortion and coma aberrations, achieving balanced correction of multiple aberration types simultaneously.
Solution Approach 2:
The optical powers of the lens groups are carefully controlled within specific ranges. The fourth lens group's positive optical power is optimized to provide sufficient correction for distortion and coma aberrations while minimizing its impact on lateral chromatic aberration variation during focusing. This parameter optimization ensures consistent optical performance across different focusing distances.
3Object-affected harmful factors
If aspherical lens elements are added to correct distortion and coma aberration, then aberration correction is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
Instead of using aspherical lens elements to correct aberrations, the invention extracts the correction function and assigns it to the fourth lens group with positive optical power. This approach replaces complex aspherical surfaces with simpler spherical surfaces in a dedicated correction group, reducing manufacturing complexity while achieving effective aberration correction.
Solution Approach 2:
The fourth lens group serves multiple functions: it corrects distortion aberration, coma aberration, and contributes to overall focal length adjustment during zooming. By making this lens group multi-functional, the design eliminates the need for separate aspherical elements dedicated solely to aberration correction, thereby simplifying the overall system.
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 a high-performance, compact zoom lens system with reduced aberration variation during focusing, suitable for mirrorless cameras, achieving better optical performance and miniaturization while maintaining functionality.
Implementation Method 1
a zoom lens system includes, in order from an object side, a first lens group having a negative optical power, a second lens group having a positive optical power, a third lens group having a positive optical power, and a fourth lens group having a negative optical power
Data Source
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AI summary
A zoom lens system includes, in order from an object side: a first, negative, lens group; a second, positive, lens group; a third, positive, lens group; and a fourth, negative, lens group. From a wide angle end to a telephoto end, Gr1-Gr2 and Gr2-Gr3 distances are reduced and Gr3-Gr4 distance is increased, Gr representing lens group. The second lens group includes a second-a, positive, lens group and a second-b lens group, and the second-a lens group is moved toward an image side for focusing to a nearby object. Conditional formula, 0.6 < f4/f1 < 5.0, -2.0 < (1 - β2w2) × βrw2 < -0.1, is satisfied (β2w: a paraxial lateral magnification of the second-a lens group at the wide angle end; βrw: a composite paraxial lateral magnification of the second-b lens group and subsequent lens groups at the wide angle end; f1, f4: focal lengths of the first, fourth lens groups).