Zoom Optical System With Dual Opposing Focusing Groups

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Solution Overview

Problem

Conventional zoom optical systems for photographic and video cameras suffer from insufficient weight reduction of focusing lens groups and significant fluctuations in aberrations, particularly spherical aberrations, when focusing from infinity to a short distance.

Innovation Solution

A zoom optical system comprising a first lens group with negative refractive power and a succeeding lens group, where the succeeding lens group includes a first focusing lens group with positive refractive power moving towards the object side and a second focusing lens group with positive refractive power moving towards the image side during focusing, along with specific conditional expressions to optimize lens movements and configurations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of moving object

If conventional zoom optical systems use focusing lens groups, then focusing from infinity to short distance is achieved, but weight reduction of focusing lens groups is insufficient and aberration fluctuations occur

Engineering Contradiction:

Improveweight of focusing lens groupsVSAvoidaberration fluctuations

Core Design Contradiction:

Weight of moving objectVSReliability

Solution Approach 1:

The succeeding lens group is divided into two separate focusing lens groups (first focusing lens group and second focusing lens group) that move in opposite directions. This segmentation allows each group to be optimized for specific functions and reduces the overall weight while maintaining aberration correction capability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The first focusing lens group moves toward the object side while the second focusing lens group moves toward the image side during focusing. This inverted movement pattern compared to conventional single-group focusing enables better aberration suppression and weight distribution

Inventive Principle:

Principle #13The other way round (Inversion)

2Speed

If focusing lens groups are made lighter for high-speed autofocus, then autofocus speed is improved, but aberration suppression becomes difficult

Engineering Contradiction:

Improveautofocus speedVSAvoidaberration suppression

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

By segmenting the focusing function into two lens groups with different movement characteristics, the system achieves both light weight for fast response and proper aberration correction through coordinated movement

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent specifies particular ranges for focal lengths and movement distances of the focusing lens groups to optimize the balance between autofocus speed and aberration suppression

Inventive Principle:

Principle #35Parameter changes

3Reliability

If zoom optical system configuration is optimized for aberration suppression, then image quality is improved, but device complexity increases

Engineering Contradiction:

Improveimage qualityVSAvoidoptical system configuration

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The first and second focusing lens groups serve multiple functions: they enable focusing from infinity to short distance, suppress aberrations, and contribute to the zoom function through their coordinated movement, reducing the need for additional dedicated components

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 reduces the weight of focusing lens groups, enables high-speed autofocus, and effectively suppresses aberration fluctuations during zooming and focusing, without increasing the size of the barrel, while maintaining excellent image quality.

Implementation Method 1

the first focusing lens group moves toward the object side and the second focusing lens group moves toward an image side upon focusing from infinity to a short distance

Methodology Applied

Scientific EffectFocusing: Focusing

Implementation Method 2

a distance between the adjacent lens groups changes upon zooming from a wide angle end to a telephoto end

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS12386159B2Zoom optical system, optical apparatus and method for manufacturing the zoom optical system

Publication Date: 2025.08.12 NIKON CORP

AI summary

A variable-power optical system (ZL) comprises a first lens group (G1) having a negative refractive power and a succeeding lens group (GR), which are disposed on an optical axis in that order from the object side. When varying magnification from wide angle to telephoto, the space between the adjacent lens groups changes. The succeeding lens group (GR) comprises: a first focusing lens group (G3) having a positive refractive power; and a second focusing lens group (G5) having a positive refractive power. When focusing from infinity to a proximate distance, the first focusing lens group (G3) moves toward the object side, and the second focusing lens group (G5) moves toward the image side.