Negative-Lead Zoom Lens Structure for Wide-Angle Chromatic Correction
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Solution Overview
Problem
Negative lead type zoom lenses face challenges in correcting aberrations while achieving a compact optical system and wide angle of view, particularly with significant magnification chromatic aberrations at the wide-angle range.
Innovation Solution
A zoom lens configuration with a first lens unit having negative refractive power, a middle group with cemented lenses convex toward the object side, and a last lens unit with positive refractive power, adhering to specific focal length and distance ratios to correct aberrations and ensure a wide angle of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the refractive power of the first lens unit is increased to achieve a wide angle of view, then the angle of view is widened, but magnification chromatic aberrations occur significantly
Solution Approach 1:
The patent introduces a middle group containing cemented lenses with specific convex surfaces as intermediary elements between the first lens unit and the image plane. These cemented lenses act as mediators to correct the magnification chromatic aberrations generated by the high refractive power of the first lens unit, while maintaining the wide angle of view capability.
Solution Approach 2:
The patent specifies precise parameter ranges for the focal lengths and distances of various lens units through inequalities (1)-(7). By optimizing these parameters, the system achieves wide angle of view while controlling chromatic aberrations through mathematical relationships between focal lengths (f1, f2, f3, fm, fl) and distances (L1s, Lsn, Ls).
2Object-affected harmful factors
If lens units are added to correct aberrations in the middle group and last lens unit, then optical performance is improved, but the complexity of lens configuration increases
Solution Approach 1:
The patent divides the zoom lens into distinct functional segments: a first lens unit with negative refractive power for wide angle, a middle group with cemented lenses for aberration correction, and a last lens unit with positive refractive power. This segmentation allows each group to specialize in specific functions, improving overall performance while managing complexity through modular design.
Solution Approach 2:
The patent employs cemented lenses in the middle group, which combine multiple lens materials with different refractive indices and Abbe numbers. This composite approach enables effective correction of chromatic aberrations by utilizing the complementary optical properties of different materials cemented together, achieving superior aberration correction without proportionally increasing system complexity.
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 configuration achieves high optical performance with a compact size and wide angle of view by effectively correcting aberrations such as magnification chromatic aberration, field curvature, and distortion.
Implementation Method 1
a first negative lens, a second negative lens, and a third negative lens that are arranged in the order from the object side to the image side
Data Source
AI summary
A zoom lens L0 consists of a first lens unit L1 having negative refractive power, a middle group Lm including one or more lens units, and a last lens unit having positive refractive power. The first lens unit L1 includes a first negative lens, a second negative lens, and a third negative lens that are arranged sequentially in an order from an object side to an image side. The number of negative lenses included in the first lens unit L1 is four or less. The middle group Lm includes a plurality of cemented lenses each having a cemented surface that is convex toward the object side, and includes a lens element Ln that is disposed closest to the image side among lens elements having negative refractive power included in the middle group Lm. The zoom lens L0 satisfies a predetermined inequality.