Zoom Lens Design for High Variable Power Ratio and Aberration Correction
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Solution Overview
Problem
Conventional zoom lenses for television and video cameras face challenges in achieving high variable power ratios while maintaining small size and excellent optical performance, particularly in correcting chromatic aberrations across the entire zoom range, which degrades image quality.
Innovation Solution
A zoom lens design comprising a stationary group with a specific power arrangement of negative and positive lens groups, including a first lens group with a negative meniscus lens and positive lenses, and a variable power group that moves along the optical axis, optimized to correct chromatic aberrations using Abbe number criteria and focal length ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the focal length of each lens group is made shorter to reduce size, then the camera size is reduced, but a large aberration variation is caused by variable power making it difficult to obtain high optical performance
Solution Approach 1:
The patent applies parameter changes by carefully controlling the focal length ratios between lens groups (specifically f1/f2 and f3/f4) and adjusting the refractive powers and Abbe numbers of individual lenses. This allows the system to achieve compact size while maintaining high optical performance across the zoom range through optimized optical parameters rather than simply making all focal lengths short.
Solution Approach 2:
The patent uses composite lens groups with different refractive indices and Abbe numbers (combining positive and negative lenses with different glass types) to correct chromatic aberrations. The first lens group uses a negative meniscus lens with high refractive power and specific Abbe number, while the second lens group uses a positive lens with different optical characteristics, creating a composite system that balances size and performance.
2Volume of moving object
If the focal length of the first group is made shorter to reduce size, then the camera size is reduced, but the residual secondary spectrum of longitudinal chromatic aberration abruptly increases near the telescopic end
Solution Approach 1:
The patent converts the harmful effect of short focal length (which causes increased chromatic aberration) into a benefit by using the first lens group with negative meniscus lens and high refractive power to specifically correct chromatic aberrations. The short focal length of the first group is compensated by its special lens configuration and the presence of the second lens group with positive lens, turning what would be a harmful factor into a corrective mechanism.
Solution Approach 2:
The patent changes the optical parameters by specifying precise focal length ratios (f1/f2 and f3/f4) and Abbe numbers for different lens groups. This parameter optimization allows the system to maintain compact size while controlling the residual secondary spectrum of chromatic aberration through mathematical relationships between the lens parameters rather than simply reducing focal lengths.
3Adaptability or versatility
If a zoom lens with high variable power ratio is designed, then the adaptability is improved, but the aberration correction becomes more difficult to maintain across the entire zoom range
Solution Approach 1:
The patent segments the zoom lens into multiple functional groups: the first lens group (with negative meniscus lens) for chromatic aberration correction, the second lens group (with positive lens) for additional aberration control, and the variable power group for zoom functionality. This segmentation allows each group to specialize in specific functions, making it possible to achieve high variable power ratio while maintaining aberration correction across the entire range.
Solution Approach 2:
The patent employs composite lens configurations with multiple glass types having different refractive indices and Abbe numbers. The combination of negative meniscus lens with high refractive power and positive lens in specific arrangements creates a composite optical system that can correct various types of aberrations simultaneously across the full zoom range, enabling high adaptability without sacrificing optical performance.
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 design achieves a high variable power ratio of 20 times or more with reduced size, effectively correcting residual secondary spectrum and chromatic aberrations across the zoom range, ensuring high optical performance and image quality.
Implementation Method 1
a first lens group having a positive refractive power, a second lens group having a positive refractive power and disposed on an image side of the first lens group, a third lens group having a negative refractive power and disposed on an image side of the second lens group, and a fourth lens group having a positive refractive power and disposed on an image side of the third lens group
Data Source
AI summary
A zoom lens comprises: a stationary group that is stationary at the time of variable power; and a variable power group, disposed on an image side of the stationary group, that makes a variable power operation by moving in an optical axis direction at the time of variable power, wherein the stationary group comprises: a first lens group including a negative meniscus lens and a positive lens and having a positive refractive power as a whole; and a second lens group, disposed on the image side of the first lens group, including: a negative lens group including a negative meniscus lens and a positive lens; and a positive lens group including at least one positive lens, in order from an object side, the second lens group having a positive refractive power as a whole.