Zoom Lens With Negative Front Group and Independent Aperture Stop

Solution Overview

Problem

Conventional zoom lenses with negative and positive optical power combinations often result in a large, heavy, and costly first positive lens group, especially when wide fields of view and focusing are required, leading to significant weight and cost contributions, as well as focus breathing issues.

Innovation Solution

A zoom lens configuration comprising a negatively powered first lens group, an aperture stop, and positively powered second and third lens groups, with a fourth lens group for telecentric light delivery to the image sensor, minimizing the diameter and weight of the first lens group and maintaining high relative illumination across the zoom range.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a conventional zoom lens uses a positively powered front lens group to provide focusing and wide field of view, then the lens can achieve focusing capability and wide field of view, but the first positive lens group becomes large in diameter, weight and cost

Engineering Contradiction:

Improvefocusing capabilityVSAvoidweight of first lens group

Core Design Contradiction:

Ease of operationVSWeight of stationary object

Solution Approach 1:

The patent inverts the conventional optical power arrangement by placing a negatively powered lens group at the front instead of a positively powered one. This inversion allows the front lens group to provide focusing capability through its negative power while significantly reducing its diameter and weight compared to conventional positive-powered front groups.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the optical power parameter of the front lens group from positive to negative. This parameter change fundamentally alters the lens group's properties, enabling it to achieve focusing capability with reduced diameter and weight while maintaining the required optical performance.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If a conventional zoom lens uses a positively powered front lens group to provide wide field of view, then the lens achieves wide field of view, but the first positive lens group requires several lens elements contributing 50% of total weight and cost

Engineering Contradiction:

Improvewide field of viewVSAvoidweight of first lens group

Core Design Contradiction:

Adaptability or versatilityVSWeight of stationary object

Solution Approach 1:

The patent inverts the conventional optical power arrangement by placing a negatively powered lens group at the front instead of a positively powered one. This inversion allows the front lens group to provide focusing capability through its negative power while significantly reducing its diameter and weight compared to conventional positive-powered front groups.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the optical power parameter of the front lens group from positive to negative. This parameter change fundamentally alters the lens group's properties, enabling it to achieve focusing capability with reduced diameter and weight while maintaining the required optical performance.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If a conventional zoom lens uses a positively powered front lens group, then the lens structure is conventional and easy to manufacture, but the first lens group contributes 50% of the weight and cost of the entire optical system

Engineering Contradiction:

Improveconventional structureVSAvoidweight of first lens group

Core Design Contradiction:

Ease of manufactureVSWeight of stationary object

Solution Approach 1:

The patent changes the optical power parameter of the front lens group from positive to negative. This parameter change fundamentally alters the lens group's properties, enabling it to achieve focusing capability with reduced diameter and weight while maintaining the required optical performance.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent inverts the conventional optical power arrangement by placing a negatively powered lens group at the front instead of a positively powered one. This inversion allows the front lens group to provide focusing capability through its negative power while significantly reducing its diameter and weight compared to conventional positive-powered front groups.

Inventive Principle:

Principle #13The other way round (Inversion)

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

This configuration achieves a compact front diameter, reduced weight, and cost while minimizing focus breathing and maintaining high image quality and relative illumination, suitable for electronic sensors.

Implementation Method 1

a first lens group with negative (−) power

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 2

an aperture stop

Methodology Applied

Scientific EffectGeometric optics: Light

Implementation Method 3

a second lens group having positive (+) power, a third lens group having positive (+) power

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 4

deliver the radiation passing through the zoom lens and on to the image sensor with nearly telecentric light paths

Methodology Applied

Scientific EffectTelecentric light paths: Light

Data Source

PatentUS9250422B2Zoom lens with forward-located aperture stop

Publication Date: 2016.02.02 NEIL IAIN A

AI summary

A zoom lens including, along an optical axis and in order from an object space to an image space: first lens group with negative power; an aperture stop; a second lens group with positive power; a third lens group with positive power; and a fourth lens group. The second and third lens groups and the aperture stop are axially movable for zooming. At least one lens element in the first lens group is moveable to provide for focusing. The aperture stop moves independently of the lens groups during zooming and has a clear aperture that changes size during zooming.