Zoom Lens Refractive Power Control for Compact High-Ratio Imaging
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Solution Overview
Problem
Existing zoom lenses with high zoom ratios and wide angles face challenges in achieving both high optical performance and reduced size, particularly when applied to larger image pickup elements, as they require precise settings of refractive powers and lens structures to correct aberrations and maintain performance across the zoom range.
Innovation Solution
A zoom lens configuration with specific refractive power arrangements and movements, including a first lens unit with positive power, a second lens unit with negative power that moves during zooming, and an N-th lens unit with positive power that does not move, satisfying conditional expressions for focal lengths and lateral magnifications to achieve high optical performance and reduced size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a four-unit zoom lens structure is used to achieve wide angle of field and high zoom ratio, then the zoom ratio and field angle are improved, but the lens size increases proportionally with larger image pickup elements
Solution Approach 1:
The patent applies parameter changes by precisely controlling the refractive powers of individual lens units and their relative positions. Specifically, it sets the refractive power of the first lens unit to satisfy 1.51 < f1/fw < 3.5 and the lateral magnification to satisfy -2.70 < βnw < 1.45, where f1 is the focal length of the first lens unit and fw is the focal length at wide angle end. These parameter optimizations allow the lens to achieve high zoom ratio and wide angle of field while maintaining compact size even when applied to larger image pickup elements.
2Manufacturing precision
If the refractive power and structure of the lens unit closest to the object side are optimized for high optical performance, then aberration correction is improved, but the lens size and complexity increase
Solution Approach 1:
The patent divides the lens system into multiple functional units with specific refractive power assignments. The first lens unit has positive refractive power and includes sub-lens units with negative and positive refractive powers for focusing. The second lens unit has negative refractive power for zooming, and the N-th lens unit has positive refractive power for image formation. This segmentation allows each unit to be optimized for its specific function while controlling overall complexity.
Solution Approach 2:
The patent applies local quality by assigning specific refractive power characteristics to specific lens units based on their functional requirements. The first lens unit closest to the object side has optimized refractive power (1.51 < f1/fw < 3.5) to correct aberrations from off-axis rays. The N-th lens unit closest to the image side has optimized lateral magnification (-2.70 < βnw < 1.45) to control the sizes of preceding lens units. This localized optimization achieves high optical performance without unnecessary complexity throughout the entire lens 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
The solution enables a zoom lens with a wide angle, high zoom ratio, and high optical performance over the entire zoom range, effectively correcting aberrations and maintaining a compact size, even when applied to larger image pickup elements.
Implementation Method 1
a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and an N-th lens unit having a positive refractive power
Data Source
AI summary
A zoom lens includes in order from object side to image side: a positive first lens unit that does not move for zooming; a negative second lens unit that moves during zooming; and a positive N-th lens unit that does not move for zooming, the N-th lens unit being arranged closest to the image side. The first lens unit includes, in order from object side to image side: a negative first sub-lens unit that does not move for focusing; a positive second sub-lens unit that moves along an optical axis during focusing; and a positive third sub-lens unit that does not move for focusing. Focal length of the first lens unit, focal length at wide angle end of the zoom lens, and lateral magnification at wide angle end satisfy predetermined conditions.