Zoom Lens with Aspherical Second Unit for Compact High-Performance Imaging
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Solution Overview
Problem
Existing zoom lenses face challenges in achieving high image quality with a small minimum F-number and wide angle capabilities while maintaining a compact size, as they struggle to correct aberrations and variations in magnification, particularly at the telephoto end.
Innovation Solution
A zoom lens configuration with a first lens unit having positive refractive power, a second lens unit with negative refractive power and at least two aspherical surfaces, and a third lens unit with adjustable refractive power, where the first lens unit does not move during zooming, and the intervals between lens units change, satisfying specific conditional expressions to control movement and focal lengths for optimal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of pixels in the solid-state image pickup element is increased to achieve high definition, then image quality is improved, but the sensor size must be increased which causes the entire camera to become larger
Solution Approach 1:
The zoom lens is divided into multiple lens units (first lens unit with positive refractive power, second lens unit with negative refractive power, third lens unit with positive refractive power, and fourth lens unit with positive refractive power), allowing each segment to contribute differently to the overall optical performance. This segmentation enables high image quality through precise aberration control while maintaining a compact form factor by distributing optical functions across multiple smaller components rather than requiring a single large sensor
Solution Approach 2:
The patent employs dynamic movement of lens units during zooming operations. The second lens unit moves along the optical axis to vary focal length, while the third and fourth lens units move to correct image plane displacement and maintain focus. This dynamic configuration allows the lens to achieve high magnification ratios (wide-angle to telephoto) without requiring a proportionally large sensor size, thereby maintaining compact camera dimensions while delivering high-definition image quality across the zoom range
2Adaptability or versatility
If the zoom ratio is increased to achieve high magnification, then magnification-varying ratio is improved, but it becomes difficult to correct spherical aberration and coma at the telephoto end
Solution Approach 1:
The zoom lens is divided into multiple lens units (first lens unit with positive refractive power, second lens unit with negative refractive power, third lens unit with positive refractive power, and fourth lens unit with positive refractive power), allowing each segment to contribute differently to the overall optical performance. This segmentation enables high image quality through precise aberration control while maintaining a compact form factor by distributing optical functions across multiple smaller components rather than requiring a single large sensor
Solution Approach 2:
The patent employs dynamic movement of lens units during zooming operations. The second lens unit moves along the optical axis to vary focal length, while the third and fourth lens units move to correct image plane displacement and maintain focus. This dynamic configuration allows the lens to achieve high magnification ratios (wide-angle to telephoto) without requiring a proportionally large sensor size, thereby maintaining compact camera dimensions while delivering high-definition image quality across the zoom range
3Manufacturing precision
If aspherical surfaces are added to correct aberrations, then optical performance is improved, but device complexity increases
Solution Approach 1:
The patent applies aspherical surfaces selectively to specific lens elements within the second lens unit rather than to all lens surfaces. This local application of aspherical geometry targets the specific regions where aberration correction is most needed, particularly for controlling spherical aberration and coma at the telephoto end. By limiting aspherical surfaces to only where necessary, the design achieves superior optical performance while avoiding the complexity and manufacturing costs associated with making all lens surfaces aspherical
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 enables a zoom lens with a small minimum F-number, good optical performance, and high magnification while keeping the entire optical system compact, effectively correcting spherical aberration, coma, and field curvature across various focal lengths.
Implementation Method 1
at least two lens surfaces, among lens surfaces of lenses included in the second lens unit except for a lens arranged closest to the object side, have aspherical shapes
Data Source
AI summary
Provided is a zoom lens, including, in order from object side: a positive first unit; a negative second unit; a third unit having a positive or positive refractive power; and a rear group including at least one unit, in which: the first unit is not moved for zooming, and intervals between adjacent units are changed during zooming; the first unit includes three lenses, and the second unit includes three lenses; at least two lens surfaces, among lens surfaces of lenses included in the second unit except for a lens arranged closest to the object side, have aspherical shapes; and focal lengths of the zoom lens at a wide angle end and at a telephoto end, movement amounts of the second and third units during zooming from the wide angle end to the telephoto end are appropriately set.