Retrofocus Wide-Angle Lens System Aberration Correction

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Solution Overview

Problem

Existing wide-angle lens systems face challenges in achieving both compactness and high optical quality due to difficulties in correcting aberrations such as lateral chromatic aberration and spherical aberration, often resulting in insufficient back focal distance and increased lens system length.

Innovation Solution

A retrofocus wide-angle lens system is designed with a specific arrangement of lens groups, including a negative first lens group with a negative meniscus lens element and a positive third lens group with cemented lens elements, optimized refractive power distribution, and aspherical surfaces to correct aberrations and maintain a long back focal distance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of stationary object

If a retrofocus lens system with a strongly negative lens group is used to secure back focal distance, then the back focal distance is sufficient, but the correcting of aberrations such as distortion and lateral chromatic aberration becomes difficult

Engineering Contradiction:

Improveback focal distanceVSAvoidaberration correction

Core Design Contradiction:

Length of stationary objectVSManufacturing precision

Solution Approach 1:

The negative lens group is divided into multiple lens groups (first negative lens group, second negative lens group, etc.) with different refractive powers. This segmentation allows each group to contribute differently to the overall optical function, enabling both sufficient back focal distance and improved aberration correction by distributing the corrective function across multiple elements rather than relying on a single strongly negative group

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different lens groups within the negative lens system are assigned different refractive powers and optical characteristics. The first negative lens group has a different refractive power than the second negative lens group, allowing each to perform specialized functions - some groups primarily providing the retrofocus effect while others focus on correcting specific aberrations like distortion or lateral chromatic aberration

Inventive Principle:

Principle #3Local quality

2Length of moving object

If refractive power is concentrated in the negative lens group to achieve wide angle, then the focal length is shortened, but the back focal distance cannot be sufficiently secured

Engineering Contradiction:

Improvefocal lengthVSAvoidback focal distance

Core Design Contradiction:

Length of moving objectVSLength of stationary object

Solution Approach 1:

The lens system is segmented into multiple groups including positive and negative lens groups arranged in a retrofocus configuration. This segmentation allows the negative groups to provide the wide-angle effect while the positive groups contribute to extending the back focal distance, distributing the optical functions across multiple elements rather than concentrating all refractive power in the negative groups

Inventive Principle:

Principle #1Segmentation

3Ease of manufacture

If the number of lens elements is reduced for cost performance, then the manufacturing cost decreases, but the correcting of aberrations becomes difficult

Engineering Contradiction:

Improvecost performanceVSAvoidaberration correction

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

Multiple lens elements are combined into cemented lens groups where adjacent lens elements are optically coupled. This merging reduces the total number of separate elements and air-glass interfaces, simplifying the overall structure and reducing manufacturing cost while maintaining the aberration correction capability through the integrated design of the cemented groups

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 achieves a high optical quality with a compact design, suitable for focusing from infinity to closer distances, while maintaining a desirable back focal distance and cost-effective performance with a small number of lens elements.

Implementation Method 1

The negative first lens group includes at least one aspherical surface

Methodology Applied

Scientific EffectAspherical surface:

Implementation Method 2

The negative second lens group includes cemented lens elements having a positive lens element and a negative lens element

Methodology Applied

Scientific EffectChromatic aberration correction: Refraction

Data Source

PatentUS7843651B2Wide-angle lens system

Publication Date: 2010.11.30 RICOH IMAGING COMPANY

AI summary

A wide-angle lens system includes a negative first lens group, a negative second lens group and a positive third lens group, in this order from the object.The first lens group includes a negative meniscus lens element having the convex surface facing toward the object, and a positive lens element having a convex surface facing toward the object, in this order from the object. The first lens group includes at least one aspherical surface.The second lens group includes a negative meniscus lens element having the convex surface facing toward the object, and cemented lens elements having a positive lens element and a negative lens element, in this order from the object.The third lens group includes cemented lens elements having a negative lens element and a positive lens element, and a positive lens element having a convex surface facing toward the image, in this order from the object.