Five-Unit Optical System With Selective Lens Movement for Fast Autofocus
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Solution Overview
Problem
Existing optical systems face challenges in achieving a wide angle of view, large aperture ratio, reduced size, and high-speed focusing while maintaining high optical performance, particularly in autofocusing capabilities.
Innovation Solution
An optical system configuration with specific lens unit arrangements and movements, including a first, third, and fifth lens unit that do not move during focusing, and a second and fourth lens unit that move, with an aperture stop between the second and third or third and fourth units, adhering to specific focal length and distance inequalities to optimize aberration correction and weight reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a focus lens unit is moved during focusing, then focusing ability is improved, but device complexity increases
Solution Approach 1:
The optical system is divided into multiple lens units (first through fifth lens units) with different refractive powers, where only specific units (second and fourth) are designated as movable focus lens units. This segmentation allows selective movement of individual units during focusing, reducing the complexity compared to moving the entire lens assembly while maintaining fast focusing capability.
Solution Approach 2:
The patent implements a dynamic focusing mechanism where the second and fourth lens units can move along the optical axis during focusing operations. This dynamic adjustment enables high-speed autofocus by allowing selective movement of lens units with appropriate refractive powers to compensate for object distance changes, improving focusing speed while managing system complexity through controlled mobility.
2Volume of moving object
If the optical system size is reduced, then compactness is improved, but aberration correction becomes more difficult
Solution Approach 1:
Different lens units are assigned different refractive powers and functional roles tailored to their specific positions in the compact optical system. The first, third, and fifth lens units have positive refractive powers for specific optical functions, while the second and fourth units provide negative refractive powers for aberration correction. This local optimization of lens properties enables effective aberration correction within a reduced system size.
Solution Approach 2:
The patent employs specific focal length relationships and refractive power distributions among the lens units to optimize the compact optical design. By carefully selecting the focal lengths f1, f2, f3, f4, f5 and their relationships (such as f1/f2, f3/f4, f5/f6 ratios), the system achieves aberration correction in a compact configuration, resolving the contradiction between size reduction and optical performance.
3Illumination intensity
If aperture ratio is increased, then light gathering ability is improved, but depth of field decreases
Solution Approach 1:
The patent implements a dynamic focusing mechanism where the second and fourth lens units can move along the optical axis during focusing operations. This dynamic adjustment enables high-speed autofocus by allowing selective movement of lens units with appropriate refractive powers to compensate for object distance changes, improving focusing speed while managing system complexity through controlled mobility.
4Manufacturing precision
If multiple lens units move during focusing, then focusing performance is improved, but weight increases
Solution Approach 1:
The optical system is divided into multiple lens units (first through fifth lens units) with different refractive powers, where only specific units (second and fourth) are designated as movable focus lens units. This segmentation allows selective movement of individual units during focusing, reducing the complexity compared to moving the entire lens assembly while maintaining fast focusing capability.
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 solution enables an optical system with a reduced size, wide angle of view, large aperture ratio, and high-speed focusing ability, effectively correcting aberrations such as astigmatism and lateral chromatic aberration.
Implementation Method 1
a first lens unit L1 with positive refractive power, a second lens unit L2 with positive refractive power, a third lens unit L3, a fourth lens unit L4 with positive refractive power, and a fifth lens unit L5
Data Source
AI summary
An optical system includes, in order from an object side to an image side, a first lens unit with positive refractive power, a second lens unit with positive refractive power, a third lens unit, a fourth lens unit with positive refractive power; and a fifth lens unit. A distance between adjacent lens units changes during focusing. The optical system further comprises an aperture stop disposed between the second lens unit and the third lens unit or between the third lens unit and the fourth lens unit. For focusing, each of the first lens unit, the third lens unit, and the fifth lens unit does not move, and each of the second lens unit and the fourth lens unit moves. Predetermined inequalities are satisfied.