Zoom Lens System with Segmented Groups for Compact Autofocus
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Solution Overview
Problem
Existing zoom lens systems face challenges in achieving a balance between size reduction, performance enhancement, and increased diameter while supporting a long focal-length range for proper focusing, particularly in standard-range zoom lenses with a wide angle and high-power zoom lenses.
Innovation Solution
A zoom lens system configuration with a six or seven-group arrangement, including a front lens group with positive, negative, and negative refractive power groups, and a rear lens group with positive refractive power, where the third lens group serves as the focus lens group, moving during focusing to decrease size and weight, and optimize autofocus speed and quietness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a zoom lens system uses a conventional configuration with limited lens groups, then the structure is simpler, but the focal length range is insufficient and the lens appears dark with high F-numbers
Solution Approach 1:
The zoom lens system is divided into five distinct lens groups (G1, G2, G3, G4, G5) with alternating positive and negative refractive powers. This segmentation allows each group to perform specific functions: G1 and G2 control wide-angle to telephoto transition, G3 serves as the focus group for close-up shooting, G4 corrects aberrations, and G5 adjusts back focus. This segmented structure enables a versatile focal length range from wide-angle to high-power zoom while maintaining manageable complexity through functional specialization.
2Area of stationary object
If the lens system is designed to be compact with small filter diameter, then the size is reduced, but the F-number increases making the lens dark
Solution Approach 1:
The lens system achieves a low F-number (F<3) despite compact dimensions by optimizing the refractive powers and spacing of the five lens groups. The alternating positive-negative configuration allows for efficient light transmission paths, while the specific power distribution across groups enables maintaining large effective aperture in a compact form factor. The focus group G3's negative refractive power is specifically optimized to control light convergence while minimizing aperture reduction.
3Reliability
If the focus group has large size and weight, then the focusing function is robust, but the autofocus speed decreases and operating sound increases
Solution Approach 1:
The focus group G3 is designed with localized optimal properties: it uses a negative refractive power configuration with specifically selected focal length and glass materials to achieve high focusing efficiency. The group's compact design with optimized element spacing minimizes moving mass while maintaining sufficient focusing authority. This localized optimization of G3's optical properties enables fast, quiet autofocus without compromising focusing reliability.
4Adaptability or versatility
If the lens system is designed for close-up shooting with shooting distance of 0.3m, then close-up capability is achieved, but the overall system size increases
Solution Approach 1:
The lens system achieves close-up shooting capability at 0.3m distance through dynamic focusing mechanism where the negative-powered focus group G3 moves along the optical axis. This dynamic adjustment of G3's position changes the effective focal length and enables close focusing without requiring a fundamentally larger optical structure. The compact system size is maintained because the focusing motion is achieved through precise displacement of the optimized G3 group rather than expanding the overall lens barrel.
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 results in a compact, high-performance zoom lens system with improved autofocus speed and reduced noise, maintaining proper focusing across a wide zoom range while ensuring back-focus amount and correcting aberrations effectively.
Implementation Method 1
a third lens group G3 having a negative refractive power... serving as a focus lens group
Data Source
Figure 1A~1C
Figure 2A~2C
Figure 3A~3C
AI summary
A zoom lens system satisfies Conditional Expression (1) as follows: −20<Twt/Twm<1, where Twt is a moving amount of the second lens group (G2) during zooming from the short focal-length end to the long focal-length end, a moving amount to the object side being indicated by a positive sign, a moving amount to an image side being indicated by a negative sign, and Twm is a moving amount of the second lens group (G2) during zooming from the short focal-length end to an intermediate focal length, the intermediate focal length being expressed by fm = (fw·ft)1/2, where fw is a focal length of a whole system at the short focal-length end, and ft is a focal length of the whole system at the long focal-length end.