Zoom Lens High-Speed Autofocusing via Third Group Extraction
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Solution Overview
Problem
Conventional zoom lenses face challenges in achieving high-speed auto focusing (AF) and downsizing while maintaining resolution corresponding to imaging elements with over 10 million pixels, due to large and heavy focusing groups that increase the size and weight of the lens barrel, leading to increased load and focusing time.
Innovation Solution
A zoom lens configuration with a five-group structure, including a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with negative refractive power, a fourth lens group with positive refractive power, and a fifth lens group with positive refractive power, where the third lens group is constituted by a single negative meniscus lens, and an aperture stop between the fourth and fifth groups, optimizing the intervals between lens groups and using specific conditions for curvature radii, focal lengths, and Abbe's number to reduce weight and size while maintaining aberration control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the second lens group is used as the focusing group, then the focusing function is achieved, but the motor and actuator sizes increase and the lens barrel diameter increases due to the large weight of the second lens group
Solution Approach 1:
The patent extracts the focusing function from the heavy second lens group and assigns it to the third lens group instead. This allows the second lens group to remain stationary during focusing, eliminating the need for large motors and actuators, and reducing the lens barrel diameter while maintaining effective focusing capability.
Solution Approach 2:
The patent changes the parameter of which lens group performs focusing from the second lens group to the third lens group. This parameter change enables high-speed AF and reduces lens barrel diameter because the third lens group has more favorable weight and size characteristics for the focusing operation.
2Manufacturing precision
If the third lens group is constituted by multiple lenses, then the optical performance is improved, but the weight of the focusing group increases and the AF speed decreases
Solution Approach 1:
The patent uses a single negative lens for the third lens group instead of multiple lenses, accepting a simpler design that reduces weight and complexity. This single-lens configuration achieves sufficient optical performance while enabling high-speed AF by minimizing the focusing group weight and inertia.
Solution Approach 2:
The patent changes the structural parameter of the third lens group from multiple lenses to a single negative lens. This parameter change reduces the focusing group weight and moment of inertia, enabling high-speed AF while maintaining acceptable optical performance through proper lens design and positioning.
3Length of moving object
If the entire length of lenses is reduced, then the zoom lens is downsized, but the resolution corresponding to high-megapixel imaging elements cannot be achieved
Solution Approach 1:
The patent employs dynamic interval adjustment between lens groups during zooming and focusing operations. By dynamically optimizing the spacing between the five lens groups, the system maintains high resolution across the entire zooming area while keeping the overall lens length reduced, achieving both compactness and high imaging performance.
Solution Approach 2:
The patent changes multiple parameters including the intervals between lens groups, the focal lengths of individual groups, and the refractive indices of lens materials. These parameter optimizations enable the lens to achieve high resolution for 10 million pixels or more imaging elements while maintaining a reduced entire length suitable for compact cameras.
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 high-speed AF, reduced lens barrel diameter, and silent focusing, while achieving a compact design with improved aberration correction and resolution across the entire zooming area, suitable for high-end digital cameras with high-magnification ratios and large pixel imaging elements.
Implementation Method 1
a first lens group (I) having a positive refractive power, a second lens group (II) having a negative refractive power, a third lens group (III) having a negative refractive power, a fourth lens group (IV) having a positive refractive power, a fifth lens group (V) having a positive refractive power
Data Source
Figure 1
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Figure 4
AI summary
A zoom lens includes, in order from an object side in an optical axis a first lens group (I) having a positive refractive power, a second lens group (II) having a negative refractive power; a third lens group (III) having a negative refractive power, a fourth lens (IV) group having a positive refractive power, a fifth lens group (V) having a positive refractive power, and an aperture stop (S) arranged between the third lens group (III) and the fourth lens group (IV), an interval between the first lens group (I) and the second lens group (II) being increased, an interval between the second lens group (II) and the third lens group (III) being varied, an interval between the third lens group (III) and the fourth lens group (IV) being decreased, and an interval between the fourth lens group (IV) and the fifth lens group (V) being decreased when changing a magnification from a wide-angle end to a telephoto end. Focusing is performed by moving the third lens group (III) whose optical power fulfills a specific condition in order to provide a high-speed autofocusing zoom lens.