Zoom Lens with Fixed Outer Groups for Aberration Control
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Solution Overview
Problem
Existing zoom lenses face challenges in achieving a wide angle and high magnification while minimizing size and maintaining favorable optical characteristics, particularly in suppressing aberrations during zooming.
Innovation Solution
A zoom lens configuration comprising five lens groups with specific refractive powers and movement strategies, where the first and fifth lens groups are fixed, and the second, third, and fourth lens groups are moved along the optical axis, with a negative lens closest to the object side in the second lens group and aspherical surfaces to control aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of lens groups is increased to achieve wide angle and high magnification, then the optical characteristics are improved, but the lens diameter and size increase
Solution Approach 1:
The zoom lens is divided into five lens groups (G1-G5) with specific refractive powers, where only three groups (G2-G4) move during zooming while G1 and G5 remain fixed. This segmentation allows achieving wide angle and high magnification with controlled size increase.
Solution Approach 2:
Instead of fixing the outer lens groups and moving inner groups, this patent fixes the first and fifth lens groups (outer groups) and moves the second, third, and fourth lens groups (inner groups). This inverted approach suppresses aberrations while controlling size.
2Adaptability or versatility
If lens groups are moved during zooming to achieve high magnification, then the zoom capability is improved, but aberrations increase
Solution Approach 1:
Each lens group is assigned a specific refractive power and movement characteristic: G1 and G5 have positive power and remain fixed, G2 has negative power and moves, G3 and G4 have positive power and move. This local differentiation optimizes aberration suppression at each position.
Solution Approach 2:
The patent specifies precise parameter ranges including focal length ratios (0.25≤f2/f21≤0.45, 0.30≤f4/f3≤0.50) and movement characteristics to maintain optimal optical performance throughout the zoom range, suppressing aberrations while achieving high magnification.
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 a wide angle and high magnification while reducing lens diameter and size, effectively suppressing aberrations and maintaining optical quality across the zoom range.
Implementation Method 1
a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, a third lens group G3 having a positive refractive power, a fourth lens group G4 having a positive refractive power, and a fifth lens group G5 having a positive refractive power
Implementation Method 2
a surface, on the image side, of the negative lens of the second lens group closest to the object side has an aspherical shape that has a refractive power lower than a refractive power in a paraxial region
Data Source
AI summary
A zoom lens consists of, in order from an object side, a positive first lens group, a negative second lens group, a positive third lens group, a positive fourth lens group, and a positive fifth lens group. During zooming, the first lens group and the fifth lens group are not moved, and the second lens group, the third lens group, and the fourth lens group are moved. The second lens group includes a negative lens closest to the object side. In a case where a focal length of the second lens group is denoted by f2 and a focal length of the negative lens of the second lens group closest to the object side is denoted by f21, the zoom lens satisfies 0.6<f2/f21<0.9.