Zoom Lens Aberration Correction via Segmented Groups

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Solution Overview

Problem

Conventional large magnification factor zoom lenses face challenges in correcting aberrations, particularly at the telephoto end, when the magnification ratio exceeds 13, leading to increased sensitivity to manufacturing errors and optical performance deterioration, due to difficulties in refractive power distribution and aspherical surface corrections.

Innovation Solution

A zoom lens configuration with specific refractive power distributions and conditional expressions for the focal lengths of its groups, including a first lens group with positive refractive power, a second lens group with negative refractive power, and a third lens group with positive refractive power, optimized to satisfy focal length ratios that allow effective aberration correction across the entire magnification range while maintaining a compact size.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the magnification ratio is increased to about 13, then the zoom lens achieves higher magnification capability, but aberration correction becomes difficult and sensitivity to manufacturing errors increases

Engineering Contradiction:

Improvemagnification ratioVSAvoidaberration correction

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The zoom lens is divided into four distinct lens groups (positive, negative, positive, positive) with specific refractive power distributions. This segmentation allows each group to contribute differently to aberration correction, enabling effective control of spherical and chromatic aberrations across the entire magnification range including the high magnification ratio of about 13.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Aspherical surfaces are selectively applied to specific lenses within the lens groups rather than uniformly across all lenses. This local quality approach corrects spherical aberrations at critical positions while maintaining manufacturing feasibility, enabling aberration correction at high magnification ratios without excessive complexity.

Inventive Principle:

Principle #3Local quality

2Manufacturing precision

If aspherical surfaces are introduced to correct aberrations, then aberration correction improves, but manufacturing complexity and cost increase

Engineering Contradiction:

Improveaberration correctionVSAvoidmanufacturing complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

Aspherical surfaces are applied selectively to only certain lenses within the lens groups rather than all lenses. This localized application provides effective spherical aberration correction where most needed while significantly reducing manufacturing complexity and cost compared to applying aspherical surfaces throughout the entire lens system.

Inventive Principle:

Principle #3Local quality

3Manufacturing precision

If refractive powers of lens groups are decreased to correct aberrations, then aberration correction improves, but lens group displacement increases and zoom mechanism becomes complicated

Engineering Contradiction:

Improveaberration correctionVSAvoidlens group displacement

Core Design Contradiction:

Manufacturing precisionVSLength of moving object

Solution Approach 1:

The lens system is segmented into four groups with optimized refractive power distribution. This segmentation allows each group to have appropriate refractive power for its function, correcting aberrations effectively without requiring excessive displacement of any single group, thus simplifying the zoom mechanism.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The refractive powers of the lens groups are optimized within specific ranges rather than simply decreased. This parameter optimization enables effective aberration correction while controlling the displacement distances of lens groups during zoom operation, avoiding overly complicated mechanisms.

Inventive Principle:

Principle #35Parameter changes

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 large magnification ratio of about 13 with improved aberration correction and reduced sensitivity to manufacturing errors, maintaining high optical performance and a wider angle of view in a compact form, effectively addressing the limitations of previous zoom lens designs.

Implementation Method 1

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

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS7746563B2Large magnification factor zoom lens

Publication Date: 2010.06.29 TAMRON CO LTD

AI summary

This large magnification factor zoom lens includes, in an order arranged from an object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power. The third lens group includes, in an order arranged from the object side, a positive lens, a positive lens, a positive meniscus lens having a larger radius of curvature on an image surface side, and a negative lens. The positive lens has an aspherical surface on an object side.