Optical System with Cemented Lens for Lightweight Focusing
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Solution Overview
Problem
Conventional large-diameter imaging optical systems face challenges in achieving quick focusing and reducing the weight of the focus lens unit while maintaining high image quality, especially as the number of lenses increases.
Innovation Solution
The optical system consists of a first positive lens unit, a second positive lens unit with a cemented lens that includes a positive and negative lens, and a third negative lens unit, where the second lens unit moves during focusing, and specific conditional expressions are satisfied to optimize the radii of curvature and refractive indices of the lenses, allowing for weight reduction and improved aberration correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of lenses is increased to achieve higher image quality, then optical performance is improved, but the weight of the focus lens unit increases
Solution Approach 1:
The optical system is divided into three lens units (positive front, positive intermediate, negative rear) with the intermediate unit serving as the lightweight focus lens unit. This segmentation allows high image quality to be achieved through the overall configuration while keeping the moving focus unit relatively simple and light.
Solution Approach 2:
The patent applies specific conditional expressions for the cemented lens parameters (radii of curvature r1LAP, r2LAP, r1LAN, r2LAN) to optimize the optical performance. By carefully controlling these parameters, high image quality is achieved without requiring excessive lens elements in the focus unit, thus maintaining lightweight construction.
2Measurement precision
If the lens diameter is increased to achieve large-aperture imaging, then imaging performance is improved, but the driving force required for focusing increases
Solution Approach 1:
The optical system segments the large-diameter lenses into fixed units (front and rear) and a smaller moving intermediate unit. This allows large aperture imaging capability while the focus driving mechanism only needs to move the lighter intermediate unit, reducing the required driving force.
Solution Approach 2:
The heavy front and rear lens units are extracted from the focusing mechanism and kept fixed. Only the essential intermediate unit with the cemented lens is assigned to the focusing mechanism, thereby reducing the mass that requires driving force while maintaining large-aperture imaging capability.
3Speed
If the weight of the focus lens unit is reduced to achieve quick focusing, then focusing speed is improved, but the number of lenses must be decreased which reduces image quality
Solution Approach 1:
The optical system is segmented such that the focus lens unit (intermediate unit) contains only the essential cemented lens elements needed for focusing and aberration correction. The heavy elements are placed in fixed units, allowing the moving unit to be lightweight for fast focusing while the overall system maintains high image quality.
Solution Approach 2:
The patent optimizes the parameters of the cemented lens in the focus unit (radii of curvature, refractive indices) to achieve both lightweight construction and high optical performance. The conditional expressions ensure that the simplified focus unit still provides adequate aberration correction for high image quality.
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 a compact, high-quality, large-diameter optical system with quick focusing capabilities and reduced weight of the focus lens unit, effectively addressing the challenges of aberration correction and weight reduction.
Implementation Method 1
The second lens unit includes a cemented lens closest to an object. The cemented lens includes a positive lens and a negative lens disposed on the image side of the positive lens.
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 second lens unit having a positive refractive power, and a third lens unit having a negative refractive power. The second lens unit moves during focusing and a distance between adjacent lens units changes. The second lens unit includes a cemented lens closest to an object. The cemented lens includes a positive lens and a negative lens disposed on the image side of the positive lens. A predetermined condition is satisfied.