Five-Lens-Unit Optical System with Split Focus Groups for Aberration Control
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Solution Overview
Problem
Optical systems with long focal length and large aperture ratio face challenges in correcting various aberrations, especially when weight reduction is necessary for faster autofocus, leading to difficulty in suppressing aberration fluctuations during focusing.
Innovation Solution
An optical system comprising five lens units with specific refractive powers and movements during focusing, including a first positive lens unit, a second negative lens unit, a third positive or negative lens unit, a fourth positive lens unit, and a fifth negative lens unit, where the first, third, and fifth lens units remain stationary during focusing, while the second and fourth move, adhering to specific focal length and refractive power ratios to correct aberrations and reduce weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the weight of the focus lens unit is reduced for faster AF, then autofocus speed is improved, but aberration fluctuations during focusing become difficult to suppress
Solution Approach 1:
The optical system divides the focusing function across multiple lens units (second and fourth lens units move during focusing) rather than relying on a single heavy focus lens unit. This segmentation allows each moving lens unit to be lighter while collectively maintaining aberration correction capability throughout the focusing range from infinity to close-up shots.
Solution Approach 2:
The patent specifies precise parameter ranges for focal lengths (f1, f2, f3, f4, f5) and their ratios to control aberration fluctuations. By optimizing these parameters, the system achieves stable optical performance during focusing without requiring excessive lens unit weight, thus enabling fast AF while suppressing aberration changes.
2Measurement precision
If optical systems have long focal length and large aperture ratio, then imaging performance is improved, but correcting various aberrations becomes difficult
Solution Approach 1:
The patent combines multiple lens units with specific refractive powers (+−++− configuration) into a unified optical system. The second and fourth lens units serve dual purposes: they contribute to the overall long focal length and large aperture ratio while simultaneously correcting aberrations through their coordinated movement during focusing, thus merging imaging performance and aberration correction functions.
Solution Approach 2:
The optical system employs dynamic aberration correction where the second and fourth lens units move during focusing to adaptively compensate for aberration fluctuations. This dynamic adjustment mechanism allows the system to maintain high imaging performance across the entire focusing range from infinity to close-up, without requiring overly complex static correction elements.
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 system achieves high-speed autofocus with high optical performance, small size, and large aperture ratio by effectively correcting aberrations and reducing the focus lens unit's weight and size, maintaining image quality across the focus range.
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 or negative refractive power, a fourth lens unit having positive refractive power, and a fifth lens unit having negative refractive power
Data Source
AI summary
An optical system includes, in order from an object side to an image side, a first lens unit having positive refractive power, a second lens unit having negative refractive power, a third lens unit having positive or negative refractive power, a fourth lens unit having positive refractive power, and a fifth lens unit having negative refractive power. During focusing from infinity to the shortest distance, the second lens unit and the fourth lens unit move, the first lens unit, the third lens unit, and the fifth lens unit do not move. A predetermined condition is satisfied.