Zoom Lens Configuration for Compact Design and Aberration Control
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Solution Overview
Problem
Existing zoom lenses for image pickup apparatuses face challenges in achieving a compact design with high focusing performance, small aberration variation, and optimal optical performance across the entire zoom range, particularly due to limitations in lens unit configuration and refractive power distribution, which affect the total lens length, diameter, and image magnification variation during focusing.
Innovation Solution
A zoom lens configuration comprising a first lens unit with positive refractive power, a second lens unit with negative refractive power, and a third lens unit with negative refractive power, where the interval between the second and third lens units increases at the telephoto end, and the third lens unit is moved during focusing, satisfying specific conditional expressions to optimize focal lengths and back focus for reduced lens length and weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the refractive power of lens units is enhanced to reduce total lens length and achieve high focusing performance, then the lens barrel diameter and mass increase, but the focusing performance and compactness are improved
Solution Approach 1:
The lens system is divided into multiple lens units with specific refractive powers (positive and negative) arranged in sequence. The first lens unit has positive refractive power, the second has negative refractive power, and the third has negative refractive power. This segmentation allows the system to achieve compactness through optimized refractive power distribution while controlling weight through selective lens unit configuration.
Solution Approach 2:
Different lens units are assigned specific refractive power characteristics tailored to their positions in the optical system. The first lens unit uses positive refractive power for initial light convergence, while the second and third units use negative refractive power to control aberrations and adjust focal length. This local optimization of refractive quality enables compact design without excessive weight.
2Object-generated harmful factors
If the focus lens unit is appropriately selected and positioned to reduce lens diameter and movement amount, then the aberration variation during focusing is reduced, but the focusing speed and image magnification stability are affected
Solution Approach 1:
The lens units are designed to move dynamically during focusing operations. The second and third lens units (with negative refractive power) are positioned to move along the optical axis during focusing, allowing the system to maintain compact diameter while reducing aberration variation. This dynamic positioning enables fast focusing without sacrificing optical performance.
Solution Approach 2:
The second and third lens units with negative refractive power act as intermediary elements between the first lens unit and the image plane. These units mediate the focusing process by moving to adjust the focal plane while maintaining a compact overall diameter and minimizing aberration introduction, thus enabling fast focusing with stable optical performance.
3Object-generated harmful factors
If the interval between lens units is increased at the telephoto end to optimize optical performance, then the aberration variation is reduced, but the total lens length and device complexity increase
Solution Approach 1:
The intervals between lens units are made variable rather than fixed. At the telephoto end, the interval between the second and third lens units is larger to optimize optical performance and reduce aberrations. At the wide angle end, the interval is smaller to maintain compactness. This dynamic interval adjustment is achieved through the movement of lens units during zooming, reducing the need for complex mechanical structures.
Solution Approach 2:
The optical parameters (intervals between lens units) are changed dynamically during zooming from wide angle to telephoto. The interval between the second and third lens units increases at the telephoto end to reduce aberrations and improve optical performance. This parameter change is achieved through the relative movement of lens units, avoiding the need for complex additional mechanical components.
4Object-generated harmful factors
If the third lens unit is moved during focusing to reduce image magnification variation, then the optical performance is improved, but the lens diameter and movement amount increase
Solution Approach 1:
The focusing function is divided between multiple lens units rather than relying on a single large moving unit. The second and third lens units (both with negative refractive power) work together to control image magnification during focusing. This segmentation allows the system to reduce image magnification variation while keeping individual lens unit diameters and movement amounts minimized.
Solution Approach 2:
The second and third lens units are specifically designed with negative refractive power and positioned to move during focusing. This local optimization of lens quality and positioning allows the system to control image magnification variation effectively while minimizing the diameter and movement amount of individual lens units compared to using a single large focus lens unit.
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 compact zoom lens with reduced aberration variation and high optical performance across the zoom range, while minimizing the lens diameter and movement amount, thus addressing the challenges of image magnification and focusing speed.
Implementation Method 1
a first lens unit having a positive refractive power; a second lens unit having a negative refractive power; a third lens unit having a negative refractive power
Implementation Method 2
The third lens unit is moved during focusing
Data Source
AI summary
Provided is a zoom lens including a plurality of lens units, in which an interval between each pair of adjacent lens units is changed during zooming. The plurality of lens units consist of, in order from an object side to an image side: a first lens unit having a positive refractive power; a second lens unit having a negative refractive power; a third lens unit having a negative refractive power; and a rear lens group including at least one lens unit. An interval between the second lens unit and the third lens unit becomes larger at a telephoto end than at a wide angle end. The third lens unit is moved during focusing. Focal lengths of the second lens unit and the third lens unit, a focal length of the zoom lens at the wide angle end, and a back focus at the wide angle end are appropriately set.