Variable Magnification Optics With Fixed Front Group

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Solution Overview

Problem

Existing variable magnification optical systems face challenges in maintaining small size, suppressing centroid position changes, and ensuring favorable optical performance across the entire magnification range.

Innovation Solution

A variable magnification optical system is designed with specific conditional expressions governing lens group configurations and movements, including a front group with two or fewer positive refractive power groups, an intermediate group with two or fewer negative refractive power groups, and a subsequent group with multiple lens groups, where certain spacings and focal lengths are optimized to maintain optical performance and minimize centroid shifts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the optical system uses more lens groups to maintain optical performance, then the optical performance is improved, but the system size increases

Engineering Contradiction:

Improveoptical performanceVSAvoidsystem size

Core Design Contradiction:

ReliabilityVSVolume of moving object

Solution Approach 1:

The optical system is divided into three distinct groups (front group, intermediate group, subsequent group) with specific refractive power configurations. The front group contains two or fewer positive power lens groups, the intermediate group contains two or fewer negative power lens groups, and the subsequent group contains multiple lens groups. This segmentation allows each group to be optimized independently for its function while controlling overall system size.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies specific conditional expressions that define parameter ranges for focal lengths (ft, fw), back focus (Bfw), and total length (TLw, TLt) to optimize the balance between optical performance and system size. These parameter constraints ensure the system maintains favorable optical performance while keeping the physical dimensions compact.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If lens groups move during magnification change, then magnification adjustment is achieved, but the centroid position changes

Engineering Contradiction:

Improvemagnification change capabilityVSAvoidcentroid position stability

Core Design Contradiction:

Adaptability or versatilityVSStability of the object's composition

Solution Approach 1:

Different lens groups are assigned different movement characteristics during magnification change. The front group (closest to the object side) is fixed with respect to the image plane, while other lens groups move to achieve magnification adjustment. This localized differentiation of movement properties allows magnification change while minimizing centroid position shifts.

Inventive Principle:

Principle #3Local quality

3Stability of the object's composition

If the front group is fixed during magnification change, then centroid position stability is improved, but magnification adjustment becomes more difficult

Engineering Contradiction:

Improvecentroid position stabilityVSAvoidmagnification adjustment

Core Design Contradiction:

Stability of the object's compositionVSEase of operation

Solution Approach 1:

The optical system is segmented into fixed and movable portions during magnification change. The front group (with two or fewer positive power lens groups) remains fixed with respect to the image plane, while the intermediate group (with two or fewer negative power lens groups) and subsequent group contain the movable elements that enable magnification adjustment. This segmentation resolves the contradiction by isolating the fixed portion for stability while allowing other portions to move for adjustment.

Inventive Principle:

Principle #1Segmentation

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 compact design that stabilizes centroid position and maintains optical performance throughout magnification changes, meeting the increasing demands for smaller and more efficient imaging apparatuses.

Implementation Method 1

a front group (GF), an intermediate group (GM), and a subsequent group (GR) in order from the object side to the image side

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS20250306350A1Variable magnification optical system and imaging apparatus

Publication Date: 2025.10.02 FUJIFILM CORP

AI summary

A variable magnification optical system consists of, in order from an object side, a front group, an intermediate group, and a subsequent group. The front group consists of two or fewer lens groups having a positive refractive power. The intermediate group consists of two or fewer lens groups having a negative refractive power. The subsequent group consists of a plurality of lens groups. A lens group of the subsequent group closest to the object side is a first subsequent lens group having a positive refractive power. Two or fewer focusing groups that move along an optical axis during focusing are disposed in the subsequent group. During magnification change, a lens group of the front group closest to the object side is fixed with respect to an image plane.