Five-Group Zoom Lens Aberration Correction and Back Focus
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Solution Overview
Problem
Conventional zoom lenses for high-definition and 4K cameras lack sufficient aberration correction and miniaturization, particularly in achieving a wide angle of view and long back focus while maintaining image quality.
Innovation Solution
A zoom lens configuration comprising five lens groups with specific refractive powers and movement ranges, where the first and fifth lens groups are fixed, and the second, third, and fourth lens groups move to adjust magnification, satisfying conditional formulas to ensure compactness, wide angle view, and effective aberration correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional zoom lens designs are used, then the lens can achieve wide angle of view, but aberration correction is insufficient
Solution Approach 1:
The zoom lens is divided into five distinct lens groups (G1-G5) with specific refractive powers, where each group serves a particular function in aberration correction and focal length adjustment. This segmentation allows independent optimization of each group to simultaneously achieve wide angle of view and excellent aberration correction.
Solution Approach 2:
Different lens groups are assigned different refractive powers (positive or negative) and specific optical characteristics to correct particular types of aberrations locally. For example, the third lens group with negative refractive power specifically addresses certain aberrations while the fourth lens group with positive refractive power addresses others, achieving comprehensive correction across the wide field of view.
2Manufacturing precision
If lens groups are increased to improve aberration correction, then optical performance improves, but device complexity increases
Solution Approach 1:
Each lens group is designed to serve multiple functions simultaneously. For instance, the moving lens groups (G2, G3, G4) not only correct aberrations through their specific refractive powers but also adjust focal length during zooming operations. This multi-functionality reduces the need for additional dedicated components, maintaining structural efficiency while achieving superior aberration correction.
Solution Approach 2:
The lens groups G2, G3, and G4 are designed to move relative to each other during zooming operations, dynamically adjusting their positions to maintain optimal optical performance across different focal lengths. This dynamic configuration allows the same five-group structure to effectively correct aberrations throughout the entire zoom range without requiring separate correction mechanisms for each focal length.
3Productivity
If lens groups move to adjust magnification, then zoom functionality is achieved, but back focus length decreases
Solution Approach 1:
The patent employs a specific arrangement where lens groups move primarily in the lateral dimension (perpendicular to the optical axis) rather than solely in the axial dimension. This lateral movement allows magnification adjustment while maintaining a longer back focus distance, as the image plane position remains relatively stable while the intermediate image positions of moving groups change to achieve zooming.
Solution Approach 2:
The fourth lens group with positive refractive power acts as an intermediary between the third lens group (negative power) and the image plane. This intermediate group helps to extend the back focus length by redistributing the optical power and adjusting the path of light rays, allowing zoom functionality to be achieved without compromising the distance from the last lens group to the image plane.
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
The solution enables a high-performance zoom lens with a long back focus, compact design, and excellent aberration correction, suitable for high-pixel cameras, providing high-quality wide-angle images.
Implementation Method 1
a first lens group G1 having a positive refractive power; a second lens group G2 having a positive refractive power; a third lens group G3 having a negative refractive power; a fourth lens group G4 having a negative refractive power; and a fifth lens group G5 having a positive refractive power
Data Source
AI summary
A zoom lens is constituted by, in order from the object side to the image side: a positive first lens group; a positive second lens group; a negative third lens group; a negative fourth lens group; and a positive fifth lens group. The first lens group and the fifth lens group are fixed with respect to an image formation plane while the second lens group, the third lens group, and the fourth lens group move to change the distances among adjacent lens group when changing magnification. Conditional Formula (1) below is satisfied.2.1<DL3/DL2<20 (1)