Single-Focus Optical System with Segmented Lens Groups

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Solution Overview

Problem

Conventional single-focus optical systems for solid-state imaging elements face challenges in reducing size while maintaining high performance, as they often increase the optical burden, are sensitive to errors, and suffer from decreased F-number and longer closest focusing distance, along with issues like dust attachment during mass production.

Innovation Solution

A single-focus optical system configuration comprising a first lens group, a second lens group, and a third lens group, where the first and third lens groups are fixed, and the second lens group is moved to focus, incorporating positive and negative lenses, aspherical surfaces, and specific conditional expressions to ensure optimal performance and compactness, reducing dust attachment and production defects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the conventional whole lens focusing method is used, then the focusing function is achieved, but the size of the drive device is increased and the entire lens unit cannot be reduced

Engineering Contradiction:

Improvesize of lens unitVSAvoiddrive device size

Core Design Contradiction:

Volume of moving objectVSDevice complexity

Solution Approach 1:

The patent divides the lens system into multiple lens groups (first lens group, second lens group, third lens group) where only the second lens group is movable for focusing. This segmentation allows the focusing function to be achieved with a smaller drive device by moving only a portion of the lens system rather than the entire lens unit.

Inventive Principle:

Principle #1Segmentation

2Reliability

If the conventional whole lens focusing method is used, then the focusing function is achieved, but dust generated in the drive section causes adverse effect on image quality

Engineering Contradiction:

Improveimage qualityVSAvoiddust generation

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent extracts the focusing function from the entire lens system by isolating the second lens group as the only movable element. This extraction minimizes the drive section size and reduces dust generation in the drive mechanism, thereby preventing dust from degrading image quality while maintaining the focusing function.

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If the conventional whole lens focusing method is used, then the focusing function is achieved, but eccentric error of the drive device decreases image quality

Engineering Contradiction:

Improveimage qualityVSAvoideccentric error sensitivity

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

By segmenting the lens system and designating only the second lens group as movable, the patent reduces the complexity of the drive mechanism. This segmentation minimizes eccentric errors in the drive device since fewer components are involved in the focusing motion, thereby maintaining image quality.

Inventive Principle:

Principle #1Segmentation

4Reliability

If optical systems with extended lens groups are used, then focusing performance is enhanced, but the total optical length is increased

Engineering Contradiction:

Improvefocusing performanceVSAvoidoptical length

Core Design Contradiction:

ReliabilityVSLength of stationary object

Solution Approach 1:

The patent segments the lens system into three groups with only the second group movable. This segmentation allows for compact optical length by moving a smaller lens group (second group with focal length 50-150mm) rather than extending the entire lens system, while still achieving effective focusing performance.

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 solution achieves a compact, high-performance optical system that maintains image quality, corrects spherical and chromatic aberrations, and reduces dust issues, enabling efficient mass production without adverse effects on F-number or closest focusing distance.

Implementation Method 1

the third lens group includes at least a lens having at least an aspherical surface with positive optical power in the periphery

Methodology Applied

Scientific EffectAspherical surface aberration correction: Lens

Implementation Method 2

a first lens group, a second lens group, and a third lens group... the first lens group includes at least a positive lens and at least a negative lens

Methodology Applied

Scientific EffectLight refraction: Refraction

Data Source

PatentUS8654242B2Single-focus optical system, image pickup device, and digital apparatus

Publication Date: 2014.02.18 KONICA MINOLTA ADVANCED LAYERS INC

AI summary

Provided is a single-focus optical system which is configured, in order from the object side to the image side, of a first to third lens groups and in which the first lens group and the third lens group are fixed with respect to a predetermined imaging surface, and the second lens group is moved in the optical axis direction to focus, wherein the first lens group comprises at least one positive lens and at least one negative lens, the second lens group comprises at least one positive lens, the third lens group comprises at least one lens having at least one aspheric surface and having a positive optical power at a peripheral portion thereof and 5<|Deltav1|<70 is satisfied where Deltav1 is a maximum value of the Abbe number difference between the positive lens and the negative lens in the first lens group.