Zoom Lens Design for Mirrorless Cameras

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Solution Overview

Problem

Existing zoom lenses for mirrorless cameras fail to achieve a balance between downsizing, large aperture, and high resolution performance, as they are not optimized for the reduced flange back distance of these cameras, leading to difficulties in reducing the total lens length and correcting aberrations.

Innovation Solution

A zoom lens configuration comprising a front lens unit with positive refractive power that does not move, multiple magnification-varying lens units with negative refractive power that move, and a rear lens unit with positive refractive power that does not move, satisfying specific conditional expressions to achieve a compact design with a large aperture and high resolution, while ensuring effective aberration correction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If existing zoom lens designs are used to achieve large aperture, then aperture ratio is improved, but total lens length increases and is not compatible with mirrorless camera downsizing

Engineering Contradiction:

Improveaperture ratioVSAvoidtotal lens length

Core Design Contradiction:

Illumination intensityVSLength of moving object

Solution Approach 1:

The zoom lens is divided into multiple lens units with specific refractive powers (positive, negative, negative, positive) that can move independently during zooming. This segmentation allows each unit to contribute differently to the overall optical path, enabling compact design while maintaining large aperture capability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The lens units are arranged in a nested configuration where inner lens units move within the structure formed by outer lens units. The magnification-varying lens units move relative to the fixed lens units, creating a compact nested structure that reduces total lens length while preserving aperture performance

Inventive Principle:

Principle #7Nested doll (Nesting)

2Length of moving object

If lens units are reduced in size for mirrorless camera compatibility, then total lens length is reduced, but aberration correction capability deteriorates

Engineering Contradiction:

Improvetotal lens lengthVSAvoidaberration correction

Core Design Contradiction:

Length of moving objectVSManufacturing precision

Solution Approach 1:

Different lens units are assigned specific refractive powers (positive or negative) and movement characteristics (fixed or movable) to address different aberration types at different positions in the optical system. The negative refractive power units specifically address certain aberrations while the positive units compensate for others, achieving comprehensive correction in a compact form

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The zoom lens uses an asymmetric configuration with two negative refractive power units and two positive refractive power units arranged in a specific sequence. This asymmetric design allows optimized aberration correction for the reduced flange back distance of mirrorless cameras while maintaining compact dimensions

Inventive Principle:

Principle #4Asymmetry

3Length of moving object

If flange back distance is reduced for mirrorless camera compatibility, then device size is reduced, but optical performance and aberration correction become more difficult to achieve

Engineering Contradiction:

Improveflange back distanceVSAvoidoptical performance

Core Design Contradiction:

Length of moving objectVSReliability

Solution Approach 1:

The zoom lens incorporates magnification-varying lens units that move dynamically during zooming to maintain optimal optical performance across different focal lengths. This dynamic adjustment compensates for the challenges posed by the reduced flange back distance, ensuring consistent aberration correction and image quality throughout the zoom range

Inventive Principle:

Principle #15Dynamics

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 proposed zoom lens design achieves a compact size compatible with mirrorless cameras, maintains a large aperture, and provides high resolution performance across the entire zoom range by optimizing the movement and refractive powers of the lens units, thereby addressing the limitations of existing designs.

Implementation Method 1

a zoom lens consists of in order from an object side to an image side: a front lens unit having a positive refractive power, a plurality of magnification-varying lens units including two magnification-varying lens units having negative refractive powers, and a rear lens unit having a positive refractive power

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS11275235B2Zoom lens and image pickup apparatus

Publication Date: 2022.03.15 CANON KK

AI summary

Provided is a zoom lens consisting of, in order from an object side to an image side: a positive front lens unit configured not to move for zooming; a plurality of magnification-varying lens units including two magnification-varying lens units having negative refractive powers configured to move for zooming; and a positive rear lens unit configured not to move for zooming, in which a focal length of the front lens unit, a focal length of a magnification-varying lens unit having a negative refractive power and arranged closest to the object side in the plurality of magnification-varying lens units, a focal length of a magnification-varying lens unit having a negative refractive power and arranged closest to the image side in the plurality of magnification-varying lens units, and a focal length of the rear lens unit are suitably set.