Zoom Lens Aberration Correction via Aspherical Second Unit
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Solution Overview
Problem
Existing zoom lenses with high zoom ratios face challenges in achieving high optical performance over the entire zoom range while being compact, due to increased aberrations caused by high refractive power in the second lens unit, which is difficult to correct using conventional aspherical lenses without appropriate configuration.
Innovation Solution
A zoom lens configuration with a first positive refractive power unit, a second negative refractive power unit, and a rear lens group with at least two positive refractive power units, where the second unit includes two successively arranged negative lenses with specific aspherical surface amounts to correct aberrations, and the intervals between lens units change during zooming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the refractive power of the second lens unit is increased to achieve downsizing and higher zoom ratio, then the zoom ratio and compactness are improved, but various aberrations are increased making it difficult to obtain high optical performance
Solution Approach 1:
The patent applies aspherical surfaces to the second lens unit, specifically configuring at least one of the object-side and image-side surfaces of each negative lens to be aspherical. This curvature modification enables effective correction of spherical aberration, coma, and other monochromatic aberrations that arise from the high refractive power required for compact high-zoom-ratio design, thereby resolving the contradiction between achieving high zoom ratio and maintaining high optical performance.
Solution Approach 2:
The patent carefully controls the aspherical surface amounts within specific ranges (0.0003 < |Ar1/Ea1×Nd1| < 0.003 and 0.0003 < |Ar2/Ea2×Nd2| < 0.003) to optimize aberration correction. By adjusting these aspherical parameters, the design achieves effective aberration control while maintaining the high refractive power needed for compact high-zoom-ratio performance, thus resolving the technical contradiction.
2Manufacturing precision
If aspherical lenses are used to correct aberrations, then optical performance is improved, but simply using aspherical lenses is insufficient without appropriate configuration of position, lens type, and surface amount
Solution Approach 1:
The patent applies aspherical surfaces specifically to the second lens unit, which has the strongest magnification-varying action and generates the most significant aberrations. By concentrating the aspherical correction where it is most needed rather than applying it uniformly across all lens units, the design achieves effective aberration correction while minimizing overall system complexity.
Solution Approach 2:
The patent divides the aspherical correction function across multiple surfaces within the second lens unit, configuring at least one aspherical surface on each negative lens. This segmentation of the correction function allows for more precise and flexible aberration control compared to using a single aspherical element, thereby achieving high optical performance with manageable configuration complexity.
3Length of moving object
If the second lens unit has high refractive power for compact design, then lens length is reduced, but distortion and astigmatism vary rapidly during zooming
Solution Approach 1:
The aspherical surfaces in the second lens unit effectively suppress the rapid variation of distortion and astigmatism during zooming by providing continuous aberration correction across the zoom range. The specific aspherical configurations counteract the aberration changes caused by the high refractive power, maintaining stable optical performance from wide-angle to telephoto positions while keeping the lens compact.
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 effectively reduces aberrations and achieves high optical performance over the entire zoom range while maintaining a compact size by dispersing the correction effect across multiple aspherical surfaces, suppressing rapid variation in distortion and astigmatism during zooming.
Implementation Method 1
a first lens unit having a positive refractive power; a second lens unit having a negative refractive power... the object-side lens surface of the first negative lens is an aspherical lens surface having a positive aspherical surface amount
Data Source
AI summary
A zoom lens, includes, in order from an object side: a positive first lens unit; a negative second lens unit; and a rear lens group that includes at least two lens units and is positive as a whole over an entire zoom range, intervals between adjacent lens units changing during zooming. The second lens unit includes at least two negative lenses successively arranged including a first negative lens arranged closest to the object side and a second negative lens, an object-side surface of the first negative lens includes an aspherical surface having a positive aspherical surface amount; and an image-side surface of the first negative lens and surfaces of the second negative lens include a surface having an aspherical surface having a positive aspherical surface amount and a surface having an aspherical surface having a negative aspherical surface amount.