Variable Magnification Optical System Lightweight Focusing Group

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Solution Overview

Problem

Existing variable magnification optical systems are not optimized for reducing the weight of the focusing group sufficiently, which hinders high-speed focusing operations and effective aberration correction.

Innovation Solution

A variable magnification optical system comprising a first lens group with positive refractive power, a second lens group with negative refractive power, and a rear group with positive refractive power, where the first lens group moves towards the object side upon magnification change, and the distances between these groups are varied, with specific refractive power conditions and aperture stop placement to achieve lightweight focusing and improved aberration correction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the focusing group weight is reduced to enable high-speed focusing, then focusing speed is improved, but aberration correction capability deteriorates

Engineering Contradiction:

Improvefocusing speedVSAvoidaberration correction capability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The rear group is segmented into multiple lens groups (A group with positive refractive power and B group with negative refractive power) that can move independently. This segmentation allows the focusing group to be lightweight for high-speed focusing while other groups correct aberrations, resolving the contradiction between focusing speed and aberration correction capability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different lens groups within the rear group have different refractive powers and movement characteristics optimized for their specific functions. The A group with positive refractive power and B group with negative refractive power are positioned and configured to provide local aberration correction while the focusing group maintains lightweight construction for high-speed operation

Inventive Principle:

Principle #3Local quality

2Adaptability or versatility

If the first lens group is moved toward the object side upon magnification change, then magnification variation is achieved, but the overall system length increases

Engineering Contradiction:

Improvemagnification variation capabilityVSAvoidoptical system length

Core Design Contradiction:

Adaptability or versatilityVSLength of stationary object

Solution Approach 1:

The distances between lens groups are made variable rather than fixed. The distance between the first lens group and second lens group, and the distance between the second lens group and rear group are both varied during magnification change, allowing compact configuration while achieving wide magnification range

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

Multiple lens groups are arranged in a nested configuration where the first lens group (positive refractive power), second lens group (negative refractive power), and rear group (positive refractive power) are positioned sequentially with variable spacing, enabling compact overall structure while maintaining adaptability for magnification variation

Inventive Principle:

Principle #7Nested doll (Nesting)

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 achieves a lightweight focusing group capable of high-speed focusing while effectively correcting various aberrations, including coma and spherical aberrations, across different magnification states.

Implementation Method 1

a first lens group disposed at a most object side and having positive refractive power, a second lens group disposed at an image side of the first lens group and having negative refractive power, and a rear group disposed at an image side of the second lens group and having positive refractive power

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS10816782B2Variable magnification optical system, optical apparatus, imaging apparatus and method for manufacturing variable magnification optical system

Publication Date: 2020.10.27 NIKON CORP

AI summary

A variable magnification optical system comprising a positive first lens group G1 disposed at a most object side, a negative second lens group G2 disposed at an image side of the first lens group G1 and a positive rear group GR disposed at an image side of the second lens group G2, upon varying magnification from an wide angle end state to a telephoto end state, the first lens group G1 being moved toward the object side, a distance between the first lens group G1 and the second lens group G2 and a distance between the second lens group G2 and the rear group GR being varied, and the rear group GR comprising a focusing group that is moved upon focusing, an A group having positive refractive power and a B group satisfying a given conditional expression with respect to the A group and having negative refractive power. Thus, the variable magnification optical system has excellent optical performance and the focusing group reduced in weight in order to attain high speed focusing operation.