Compact Zoom Lens System with Segmented Focusing Group

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Solution Overview

Problem

Existing zoom lens systems are cumbersome and difficult to handle due to their large size and weight, and they often suffer from aberration issues such as curvature of field, spherical aberration, and axial chromatic aberration, which complicates image acquisition, especially during zooming and focusing.

Innovation Solution

A compact and lightweight zoom lens system with a negative-positive-positive refractive power arrangement, where the third lens group is fixed, and the second lens group includes a sub-lens group with negative refractive power for focusing, allowing for simplified mechanisms and effective aberration correction by satisfying specific conditions for refractive power ratios between lens groups.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If multiple lens groups are moved during zooming and focusing, then aberration correction is improved, but device complexity and weight increase

Engineering Contradiction:

Improveaberration correctionVSAvoidmechanism complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The second lens group is segmented into a first sub-lens group (positive refractive power) and a second sub-lens group (negative refractive power). During zooming, both sub-groups move together, but during focusing, only the second sub-lens group moves independently. This segmentation allows aberration correction while simplifying the overall mechanism by dividing functions between fixed and movable components.

Inventive Principle:

Principle #1Segmentation

2Adaptability or versatility

If lens groups are moved during zooming, then zooming function is achieved, but weight and size increase

Engineering Contradiction:

Improvezooming functionVSAvoidlens system weight

Core Design Contradiction:

Adaptability or versatilityVSWeight of moving object

Solution Approach 1:

The third lens group with positive refractive power is fixed during zooming, which is unconventional as typically all groups move. This inversion of the typical zooming mechanism reduces the number of moving parts and overall system weight while still achieving the zooming function through coordinated movement of the first and second lens groups.

Inventive Principle:

Principle #13The other way round (Inversion)

3Device complexity

If the third lens group is fixed during zooming, then mechanism complexity is reduced, but aberration correction may be compromised

Engineering Contradiction:

Improvezooming mechanismVSAvoidaberration correction

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The third lens group is pre-positioned at optimal locations along the optical axis for both wide-angle and telephoto ends. During zooming, while the third group remains fixed, the first and second lens groups are moved to predetermined positions that maintain proper optical spacing. This preliminary positioning ensures aberration correction is achieved without requiring the third group to move.

Inventive Principle:

Principle #10Preliminary action

4Ease of operation

If a second sub-lens group with negative refractive power is added for focusing, then focusing capability is improved, but device complexity increases

Engineering Contradiction:

Improvefocusing capabilityVSAvoidlens group configuration

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The second sub-lens group with negative refractive power is merged with the first sub-lens group with positive refractive power to form the second lens group. During zooming, both sub-groups move together as a unit, but during focusing, the second sub-lens group moves independently. This merging allows the system to achieve both zooming and focusing functions while managing complexity through coordinated movement patterns.

Inventive Principle:

Principle #5Merging (Combining)

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 provides a compact, easy-to-handle zoom lens system that effectively corrects aberrations across the entire zoom range, simplifies the zooming and focusing mechanisms, and ensures stable image acquisition with minimal fluctuations in brightness.

Implementation Method 1

a first lens group G1 that has negative refractive power, a second lens group G2 that has positive refractive power, and a third lens group G3 that has positive refractive power

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS11378788B2Zoom lens system and imaging apparatus

Publication Date: 2022.07.05 NITTO OPTICAL CO LTD

AI summary

A zoom lens system (10) for imaging, includes, in order from an object side (11); a first lens group (G1) with negative refractive power that moves at the time of zooming; a second lens group (G2) with a positive refractive power that moves at the time of zooming, the second lens group including an aperture stop (St); a third lens group (G3) with a positive refractive power, the position of which is fixed relative to the image plane. The second lens group includes: a first sub-lens group (S1) with a positive refractive power arranged on the object side and having the aperture stop; and a second sub-lens group (S2) with a negative refractive power arranged on the image plane side and configured to move independently of the first sub-lens group at the time of focusing.