Anamorphic Zoom Lens Design for Compact Diameter and Thermal Stability

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Anamorphic objective zoom lenses face challenges in providing a compact diameter with a useful zoom range from wide to narrow fields of view while maintaining aberration correction and thermal compensation, especially with the advent of digital cameras which are less tolerant of residual chromatic aberrations and thermal focus shifts.

Innovation Solution

The design incorporates a negatively powered spherical first lens group, an anamorphic second lens group, a positively powered spherical third lens group, a variable power spherical fourth lens group, and a positively powered spherical fifth lens group with an optical stop, featuring axially movable lens elements for zooming and thermal compensation, reducing residual chromatic aberration and astigmatism, and maintaining focus across temperature changes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a front anamorphic lens group configuration is used to achieve traditional anamorphic imaging characteristics, then oval bokeh and artistic look are produced, but the lens diameter becomes large and weight increases

Engineering Contradiction:

Improveanamorphic imaging characteristicsVSAvoidlens diameter and weight

Core Design Contradiction:

ReliabilityVSWeight of stationary object

Solution Approach 1:

The lens is divided into five distinct lens groups (G1-G5) with specific functions: G1 for focusing, G2 for anamorphic imaging, G3 and G5 for thermal compensation, and G4 for zooming. This segmentation allows each group to be optimized for its specific function, reducing the overall diameter compared to a monolithic design while maintaining anamorphic characteristics.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different lens groups have different optical properties: G1 has negative power, G2 has anamorphic power with cylindrical surfaces, G3 and G5 have positive power for thermal compensation. This local differentiation of optical qualities allows the system to achieve anamorphic effects without requiring a uniformly large diameter throughout the entire lens structure.

Inventive Principle:

Principle #3Local quality

2Adaptability or versatility

If zoom functionality is added to anamorphic lenses to provide wide to narrow fields of view, then versatility increases, but residual chromatic aberration and thermal focus shifts worsen

Engineering Contradiction:

Improvezoom rangeVSAvoidchromatic aberration and thermal focus shift

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

Lens groups G3 and G5 are positioned and configured in advance to provide thermal compensation before thermal expansion occurs. These groups are designed with positive power and are axially movable to preemptively counteract thermal focus shifts that would otherwise occur during temperature changes, thereby maintaining focus accuracy across varying temperatures while enabling zoom functionality.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The lens employs axial movement of lens groups G3, G5, and G4 to dynamically change optical parameters during zooming and thermal compensation. By adjusting the axial positions of these groups, the system maintains focus and reduces chromatic aberration across the zoom range from wide to narrow fields of view, adapting optical parameters to compensate for environmental changes.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If lens elements are made axially movable to enable zooming and thermal compensation, then functionality increases, but device complexity increases

Engineering Contradiction:

Improvezoom and focus controlVSAvoidmechanical complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Lens group G4 serves multiple functions: it provides zooming capability while also contributing to thermal compensation alongside groups G3 and G5. This multi-functionality reduces the need for separate dedicated mechanisms, thereby controlling complexity while maintaining versatility.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 low residual chromatic aberration, a traditional oval bokeh shape, and different depths of field, providing a medium fast full aperture and efficient imaging over a wide to narrow angle field of view with minimal breathing and thermal defocus, suitable for both film and digital cameras.

Implementation Method 1

The anamorphic second lens group has at least one cylindrical surface in a first direction and at least one other cylindrical surface in a substantially perpendicular direction to the first direction to enable a high degree of aberration correction over the whole image, whereby the residual longitudinal chromatic aberration and the residual lateral chromatic aberration are substantially reduced.

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 2

Lens elements of the spherical third and fifth lens groups are independently axially movable by active or passive or active and passive means while preferably maintaining the overall length of the anamorphic objective zoom lens to provide thermal compensation of defocus which is consistently small and has little astigmatism through focusing and zooming.

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS9841538B2Anamorphic objective zoom lens

Publication Date: 2017.12.12 COOKE OPTICS LTD

AI summary

The anamorphic objective zoom lens includes, along an optical axis and in order from an object space to an image space: at least a negative (−) power spherical first lens group; an anamorphic second lens group, spherical third lens group preferably having positive (+) power, a variable power spherical fourth lens group and a positive (+) power spherical fifth lens group. The aperture stop is located before, after or preferably within the spherical fifth lens group. All spherical lens groups contain spherical and piano refractive optical surfaces. The anamorphic second lens group contains cylindrical and plano optical surfaces with at least one cylindrical surface oriented at substantially 90 degrees about at least one other cylindrical surface. The spherical first lens group may provide focusing. The variable power spherical fourth lens group provides zooming. The spherical third and fifth lens groups may provide compensation for thermal defocus.