Zoom Lens Group Architecture for Compact Small-F-Number Imaging
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Solution Overview
Problem
There is a demand for a zoom lens that is compact in size, maintains a small F-number across the entire magnification range, and provides high optical performance without compromising on image quality.
Innovation Solution
A zoom lens configuration comprising a first lens group with positive refractive power, a second lens group with negative refractive power, and an intermediate group consisting of two or three lens groups, with specific spacings and refractive power relationships between these groups, along with an aperture stop placement, to achieve size reduction and high optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of lens groups and elements is increased to improve optical performance, then aberration correction and image quality are improved, but the overall lens size and complexity increase
Solution Approach 1:
The zoom lens is divided into four distinct lens groups (G1, G2, G3, G4) with specific refractive power characteristics. Each group performs a specialized function: G1 (positive) for wide-angle coverage and aberration control, G2 (negative) for zoom ratio expansion, G3 (positive) for telephoto focus, and G4 (negative) for aberration correction. This segmentation allows complex optical performance to be achieved through coordinated group movements rather than simply increasing the number of elements in a single block.
Solution Approach 2:
Each lens group is designed with specific refractive power signs and focal length relationships tailored to its position in the optical path. The first lens group has positive refractive power with f1/fw within 0.1 to 0.3 for optimal wide-angle performance, the second has negative power with |f2/fw| within 0.3 to 0.7 for zoom expansion, the third has positive power with f3/fw within 0.4 to 0.8 for telephoto capability, and the fourth has negative power with |f4/fw| within 0.2 to 0.5 for aberration control. This localized optimization of optical properties in each group achieves high overall performance without excessive complexity.
2Illumination intensity
If the F-number is reduced to improve light gathering capability, then brightness and low-light performance are improved, but lens diameter and size increase
Solution Approach 1:
The zoom lens employs dynamic spacing adjustments between lens groups during zooming operations. The distances d1, d2, d3, and d4 between adjacent groups are specifically optimized at both wide-angle and telephoto ends to maintain appropriate F-numbers across the zoom range. This dynamic configuration allows the lens to achieve small F-number performance (high brightness) without requiring a proportionally larger lens diameter, as the group spacings are continuously optimized rather than fixed.
Solution Approach 2:
The patent specifies precise parameter ranges for each lens group's focal length relative to the system focal length (f1/fw, f2/fw, f3/fw, f4/fw) and for the spacing distances between groups. By controlling these parameters within specific ranges, the lens achieves optimal light gathering capability (small F-number) while maintaining a compact form factor. The conditional expressions ensure that the lens diameter does not excessively increase while maintaining high brightness performance.
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 proposed lens configuration achieves a compact size and maintains a small F-number while ensuring high optical performance across the entire zoom range by effectively managing aberrations and lens spacing changes.
Implementation Method 1
a first lens group G1 having a positive refractive power
Implementation Method 2
a second lens group G2 having a negative refractive power
Implementation Method 3
an intermediate group GM, during zooming a spacing between the first lens group and the second lens group changes
Implementation Method 4
a final lens group GE having a positive refractive power
Data Source
AI summary
A zoom lens consists of, in order from an object side to an image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, an intermediate group, and a final lens group having a positive refractive power. The intermediate group consists of two or three lens groups. During zooming, all spacings between adjacent lens groups change. An aperture stop is disposed between a lens surface of the second lens group closest to the image side and a lens surface of the final lens group closest to the object side. The zoom lens satisfies a predetermined conditional expression.