Optical System with Single-Lens Focusing for Lightweight Telephoto Imaging
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Solution Overview
Problem
Conventional telephoto lenses with long focal lengths are heavy and require complex focusing systems, leading to high weight and difficulty in achieving high-speed focusing, while also experiencing significant aberration fluctuations during focusing.
Innovation Solution
An optical system comprising a first lens unit with a positive refractive power, a diaphragm, a second lens unit with a negative refractive power, and a third lens unit with a positive refractive power, where the second lens unit moves during focusing, and specific conditional expressions are satisfied to reduce weight and correct aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a telephoto lens with long focal length is designed, then the imaging capability is improved, but the lens becomes larger and heavier
Solution Approach 1:
The telephoto lens is divided into multiple lens units (first lens unit with positive refractive power, second lens unit with negative refractive power, and third lens unit with positive refractive power). This segmentation allows each unit to be optimized independently for weight and function, reducing the overall weight while maintaining long focal length imaging capability.
2Manufacturing precision
If a complex focusing unit with multiple lenses is used, then aberration correction is improved, but the weight increases and focusing speed decreases
Solution Approach 1:
The second lens unit with negative refractive power is extracted as the dedicated focusing unit, separate from the other lens units. This allows the focusing function to be isolated in a single lightweight unit, enabling high-speed focusing while maintaining aberration correction capability through its specific optical design.
Solution Approach 2:
The second lens unit is designed with specific parameter ranges: focal length f2 satisfying -0.50f < f2 < -0.20f, and refractive power φ2 satisfying -0.10 < φ2 < -0.05. These optimized parameters enable effective aberration correction during focusing while keeping the unit lightweight for high-speed operation.
3Manufacturing precision
If the second lens unit includes multiple lenses for aberration correction, then the aberration correction is improved, but the weight of the focusing unit increases
Solution Approach 1:
The second lens unit is designed with optimized parameter ranges: focal length f2 satisfying -0.50f < f2 < -0.20f, and refractive power φ2 satisfying -0.10 < φ2 < -0.05. These specific parameter values enable effective aberration correction while minimizing the number of lenses required, thereby reducing the focusing unit weight.
4Manufacturing precision
If a heavy focusing unit is used for aberration correction, then the aberration correction is improved, but the focusing speed decreases
Solution Approach 1:
The focusing function is extracted into a dedicated second lens unit that is mechanically separated from the other lens units. This isolated design with optimized negative refractive power allows the unit to be lighter and smaller, enabling high-speed focusing movement while maintaining effective aberration correction 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 optical system achieves a lightweight focusing unit with reduced aberrations and faster focusing speeds by optimizing lens unit distances and refractive powers, allowing for a compact and efficient imaging solution.
Implementation Method 1
a first lens unit (L1) having a positive refractive power
Implementation Method 2
a second lens unit (L2) having a negative refractive power
Implementation Method 3
a third lens unit (L3) having a positive 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 a positive refractive power, a diaphragm, a second lens unit having a negative refractive power, and a third lens unit having a positive refractive power. A distance between adjacent lens units is changed during focusing. The second lens unit is moved to the image side during focusing from an object at infinity to a short-distance object. The first lens unit includes a positive lens closest to an object and two or more negative lenses. The second lens unit consists of a single negative lens. A predetermined condition is satisfied.