Five-Group Variable Magnification Optical System for Aberration Control

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Solution Overview

Problem

Conventional variable magnification optical systems suffer from large variations in aberrations, particularly spherical aberration and curvature of field, which affect image quality.

Innovation Solution

A variable magnification optical system comprising five lens groups, with the first lens group fixed and the others movable, and specific focal length ratios between lens groups to correct aberrations. The system includes conditional expressions to optimize lens configurations, ensuring superb correction of coma aberration, spherical aberration, and astigmatism.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional variable magnification optical system configurations are used, then the system can achieve variable magnification, but large variations in aberrations occur

Engineering Contradiction:

Improvevariable magnification capabilityVSAvoidaberration control precision

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The optical system is divided into five distinct lens groups with specific refractive power assignments (positive, negative, positive, positive, negative). Each lens group can be independently positioned, allowing separate optimization of aberration correction for each segment while maintaining overall variable magnification capability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Each lens group is assigned a specific refractive power characteristic (positive or negative) to address local optical requirements. The first lens group has positive refractive power for initial light convergence, the second has negative for divergence and aberration correction, and subsequent groups have alternating powers to locally correct specific aberrations at different positions in the optical path.

Inventive Principle:

Principle #3Local quality

2Adaptability or versatility

If multiple lens groups are made movable to achieve focusing and magnification variation, then optical functionality is enhanced, but device complexity increases

Engineering Contradiction:

Improvefocusing and magnification controlVSAvoidlens group movement mechanism

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The fourth lens group serves multiple functions simultaneously: it acts as the focusing lens group for distance adjustment and also contributes to magnification variation when its position is changed. This multi-functionality reduces the need for separate dedicated components, thereby simplifying the overall mechanism.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The optical system employs dynamic positioning of lens groups where the first lens group remains fixed during magnification variation while other lens groups move. This dynamic configuration allows the system to adapt its structure based on operational requirements (focusing vs. magnification adjustment) rather than requiring all components to be movable.

Inventive Principle:

Principle #15Dynamics

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 system effectively suppresses variations in aberrations across different magnification settings, maintaining high optical performance and enabling a compact, simplified lens barrel design.

Implementation Method 1

a first lens group having positive refractive power; a second lens group having negative refractive power; a third lens group having positive refractive power; a fourth lens group having positive refractive power; and a fifth lens group having negative refractive power

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS20250291163A1Variable magnification optical system, optical device, and method for manufacturing variable magnification optical system

Publication Date: 2025.09.18 NIKON CORP

AI summary

Comprising, in order from an object side: a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having positive refractive power, and a fifth lens group having negative refractive power; upon varying a magnification, the first lens group being fixed with respect to the image plane, and each distance between the neighboring lens groups being varied; upon focusing, at least a portion of the fourth lens group being moved; and predetermined conditional expression(s) being satisfied, thereby variations in various aberrations upon varying magnification being superbly suppressed.