Zoom Lens Segmentation Reduces Focus Breathing
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Solution Overview
Problem
Existing zoom lenses face challenges in reducing the size and weight of moving lens units while minimizing focus breathing and maintaining optical performance, especially in telephoto zoom lenses with large aperture diameters.
Innovation Solution
The zoom lens design includes a front group with a first lens unit having positive refractive power and intermediate lens units with negative refractive power, along with a rear group containing an aperture stop and focus lens units. During zooming, the first lens unit and the final lens unit in the rear group are fixed, and the intermediate lens units move towards the image side, optimizing the distance between lens units and reducing weight and focus breathing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the diameter of the first lens unit is kept small to achieve a compact and lightweight zoom lens, then the overall size and weight are reduced, but a one-sided aperture state occurs causing focus breathing to increase when the aperture is narrowed
Solution Approach 1:
The zoom lens is divided into multiple lens units (first lens unit, second lens unit, third lens unit, fourth lens unit) with different functions. The first lens unit has positive refractive power and is fixed during zooming, while the other lens units move during zooming. This segmentation allows the first lens unit to be kept small without causing the entire lens to become unstable, and the movement of subsequent lens units compensates for the one-sided aperture effect to reduce focus breathing.
Solution Approach 2:
The second lens unit with negative refractive power acts as an intermediary between the first lens unit and the remaining lens units. By positioning and moving this negative power lens unit, the optical path is adjusted to counterbalance the one-sided aperture state caused by the small first lens unit, thereby reducing focus breathing when the aperture is narrowed.
2Adaptability or versatility
If lens units are made to move during zooming and focusing, then the zoom ratio and focusing capability are improved, but the weight of moving lens units increases and torque for driving them increases
Solution Approach 1:
The lens system is segmented into four distinct lens units, each with specific refractive powers and movement characteristics. The first lens unit remains fixed during zooming, while the second, third, and fourth lens units move. This segmentation distributes the movement requirements across multiple lighter units rather than requiring a single heavy moving unit, thereby reducing the overall weight and driving torque while maintaining zoom and focusing capabilities.
Solution Approach 2:
The lens units are designed with dynamic movement characteristics where the second, third, and fourth lens units move during zooming, and the third and fourth lens units additionally move during focusing. This dynamic configuration allows the system to achieve high zoom ratio and focusing capability with individual lens units that are lighter and require less driving torque compared to a static or single-moving-unit design.
3Weight of moving object
If the first lens unit is fixed for rear focusing, then the weights of moving lens units are reduced, but focus breathing becomes more noticeable when the aperture is narrowed in a one-sided aperture state
Solution Approach 1:
The lens system is divided into four lens units with the first lens unit fixed during both zooming and focusing operations. The second, third, and fourth lens units are configured to move during zooming, and the third and fourth lens units additionally move during focusing. This segmentation allows the heavy first lens unit to remain stationary, reducing the weight of moving components, while the coordinated movement of the other lens units compensates for the one-sided aperture effect to minimize focus breathing.
Solution Approach 2:
The second lens unit with negative refractive power serves as an intermediary that moves during zooming to counterbalance the one-sided aperture state. This intermediary unit adjusts the optical path to reduce focus breathing when the aperture is narrowed, while the third and fourth lens units provide additional adjustment during focusing operations.
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 design achieves a compact and lightweight zoom lens with reduced focus breathing and improved optical performance throughout the zoom range, while maintaining a small size and weight for the moving lens units.
Implementation Method 1
a first lens unit having positive refractive power
Implementation Method 2
a plurality of intermediate lens units, the plurality of intermediate lens units including one or more lens units having negative refractive power
Data Source
AI summary
A zoom lens includes, in order from an object side to an image side, a front group consisting of a first lens unit having positive refractive power and a plurality of intermediate lens units, the plurality of intermediate lens units including one or more lens units having negative refractive power, and a rear group consisting of an aperture stop and lens units. During zooming, the first lens unit and the lens unit closest to an object in the rear group are fixed and each intermediate lens unit moves toward the image side, a distance between adjacent lens units among lens units included in the front group and the lens unit closest to the object in the rear group changes. The rear group includes first and second focus lens units that move moving during focusing. Predetermined inequalities are satisfied.