Zoom Lens Four-Unit Configuration for High Ratio and Compact Size
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Solution Overview
Problem
Existing zoom lenses face challenges in achieving a high zoom ratio with a small size, wide angle of view, and low aberration, particularly in maintaining optical performance across the entire zoom range while minimizing the size of the system.
Innovation Solution
A zoom lens configuration with a first lens unit having positive refractive power, a second lens unit with negative refractive power, a third lens unit with positive refractive power, and a fourth lens unit with positive refractive power, where the second, third, and fourth lens units are moved during zooming, while the first lens unit remains stationary, and specific conditional expressions are satisfied to optimize the focal lengths and moving amounts of the lens units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a positive-lead four-unit zoom lens is used to achieve high zoom ratio, then the zoom ratio and system size are improved, but the optical performance and aberration correction become difficult to maintain
Solution Approach 1:
The patent applies parameter changes by precisely controlling the refractive power distribution among the four lens units and the movement amounts of each unit during zooming. The conditional expressions define specific parameter ranges for focal lengths and movement distances, transforming the qualitative design into a quantifiable parameter optimization problem that resolves the contradiction between high zoom ratio and optical performance
Solution Approach 2:
The zoom lens is segmented into four distinct lens units with specific refractive power assignments (positive, negative, positive, positive). This segmentation allows independent optimization of each unit's function: the first unit for wide angle coverage, the second for zoom ratio enhancement, the third for aberration correction, and the fourth for image plane stabilization, thereby achieving high zoom ratio while maintaining optical performance
2Productivity
If the second lens unit is moved significantly during zooming to increase zoom ratio, then the zoom ratio is improved, but the aberration correction becomes more difficult
Solution Approach 1:
The third lens unit acts as an intermediary that compensates for aberrations generated by the movement of the second lens unit. While the second unit's significant movement enables high zoom ratio, the third unit's coordinated movement and positive refractive power serve to correct the resulting spherical aberration and coma, mediating between the conflicting requirements of zoom ratio and aberration control
Solution Approach 2:
The patent employs composite optical design by combining lens units with different refractive powers and dispersion characteristics. The fourth lens unit, with its specific positive refractive power, complements the other units to provide composite correction of various aberrations while maintaining the high zoom ratio enabled by the second unit's movement
3Manufacturing precision
If the fourth lens unit is moved for image plane correction, then the image quality is improved, but the system complexity increases
Solution Approach 1:
The fourth lens unit is designed with multi-functionality: it corrects image plane changes during zooming, contributes to aberration correction across the zoom range, and maintains focus. This universal design allows a single lens unit to perform multiple functions that would otherwise require separate mechanisms, thereby improving image quality 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
This configuration enables a high zoom ratio with a small system size and reduced aberrations, ensuring favorable optical performance and a wide angle of view, while minimizing the total lens length and weight, and allowing for effective correction of image plane changes and aberrations.
Implementation Method 1
a first lens unit having positive refractive power, a second lens unit having negative refractive power, a third lens unit having positive refractive power, and a fourth lens unit having positive refractive power
Data Source
AI summary
A zoom lens includes a first lens unit having positive refractive power, a second lens unit having negative refractive power, a third lens unit having positive refractive power, and a fourth lens unit having positive refractive power, in order from an object side to an image side. During zooming, the first lens unit is not moved, and the second lens unit, the third lens unit, and the fourth lens unit are moved to change an interval between adjacent lens units. A moving amount m2 of the second lens unit during zooming from a wide angle end to a telephoto end, a focal length f2 of the second lens unit, and a focal length fw of a whole system at the wide angle end are each set appropriately.