Zoom Lens Extender Unit Abbe Number Optimization
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Solution Overview
Problem
Zoom lenses with internal extender mechanisms for broadcasting television cameras face challenges in reducing secondary spectrum axial chromatic aberration, particularly as pixel density increases, leading to color bleeding due to axial chromatic aberration, and existing solutions lack guidance on selecting appropriate glass materials for partial dispersion ratios.
Innovation Solution
A zoom lens configuration that includes a master lens with specific refractive power units and an extender lens unit, where the extender lens unit is designed with a positive lens Gp made of material satisfying specific conditional expressions for Abbe number and partial dispersion ratio, effectively correcting secondary spectrum axial chromatic aberration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an extender lens unit is inserted to increase the focal length range, then the zoom ratio is improved, but secondary spectrum axial chromatic aberration increases causing color bleeding
Solution Approach 1:
The patent applies parameter changes by carefully selecting glass materials with specific Abbe numbers (νd) and partial dispersion ratios (θgF) that satisfy defined conditional expressions. This changes the optical parameters of the extender lens unit to correct secondary spectrum axial chromatic aberration while maintaining the extended focal length range
Solution Approach 2:
The patent uses composite materials by combining multiple glass types with different optical properties in the extender lens unit. Specifically, it employs a positive lens with particular νd and θgF values alongside other lens elements, creating a composite optical system that achieves both extended focal length and chromatic aberration correction
2Measurement precision
If the number of pixels in the image pickup element is increased to improve resolution, then image quality is improved, but color bleeding due to axial chromatic aberration becomes more conspicuous
Solution Approach 1:
The patent addresses this contradiction by changing the optical parameters of the extender lens unit, specifically selecting glass materials with Abbe numbers and partial dispersion ratios that satisfy defined conditional expressions. This corrects axial chromatic aberration at the optical level, preventing color bleeding even when high pixel density is used in the image pickup element
3Adaptability or versatility
If an extender lens unit is inserted to change the focal length range, then the zoom ratio is improved, but longitudinal aberration increases with a magnification equal to the square of the extender magnification
Solution Approach 1:
The patent applies parameter changes by selecting glass materials with specific optical properties (Abbe number and partial dispersion ratio) that satisfy defined conditional expressions. This optimization of material parameters helps control longitudinal aberration while maintaining the extended focal length range provided by the extender lens unit
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 effectively suppresses secondary spectrum axial chromatic aberration and achieves high optical performance by optimizing the partial dispersion ratio and Abbe number of the extender lens unit, improving image quality and reducing color bleeding.
Implementation Method 1
the positive lens Gp satisfies conditional expressions involving Abbe number νd and partial dispersion ratio θgF, where these parameters control the refractive properties of the lens material to correct chromatic aberration
Data Source
AI summary
A zoom lens includes: a master lens including in order from an object side: a positive first lens unit configured not to move for zooming; a negative second lens unit configured to move for zooming; at least one lens unit configured to move for zooming; and a positive relay lens unit arranged closest to the image side; and an extender lens unit configured to change a focal length range of the zoom lens by one of: being inserted in place of a lens unit arranged adjacent to the relay lens unit on the object side; and being inserted into a space adjacent to the positive relay lens unit on the object side, wherein the extender lens unit includes a positive lens Gp, and an Abbe number and a partial dispersion ratio of the positive lens Gp are suitably set.