Three-Group Optical Layout for Compact Close-Range Focusing
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Solution Overview
Problem
Existing optical systems in imaging devices struggle to achieve compact size while maintaining the ability to focus at closer distances, often resulting in increased variations in aberrations and overall length during focusing.
Innovation Solution
An optical system comprising a first lens group with positive refractive power, a second lens group with positive refractive power that moves during focusing, and a third lens group with negative refractive power, configured to satisfy specific conditional expressions that optimize focal length ratios and lens distributions, reducing aberrations and overall length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the optical system uses a conventional lens group configuration to achieve compact size, then the overall length is reduced, but the ability to focus at closer distances deteriorates
Solution Approach 1:
The optical system is divided into three distinct lens groups (first lens group with positive refractive power, second lens group with positive refractive power, and third lens group with negative refractive power). This segmentation allows each group to have specialized functions: the first group provides overall positive power, the second group enables focusing by moving relative to the image plane, and the third group corrects aberrations. This segmentation resolves the contradiction by allowing compact overall length while maintaining close-distance focusing capability through coordinated movement of the second lens group.
Solution Approach 2:
Each lens group is assigned specific local optical properties: the first lens group has positive refractive power for overall convergence, the second lens group has positive refractive power optimized for focusing movement, and the third lens group has negative refractive power for aberration correction. The second lens group specifically includes lenses with particular Abbe numbers and refractive powers to optimize focusing performance. This local quality assignment allows the system to maintain compact size while achieving superior focusing capability at close distances.
2Productivity
If the optical system moves multiple lens groups during focusing, then focusing speed is improved, but the variations in aberrations increase
Solution Approach 1:
The focusing function is extracted and assigned specifically to the second lens group, which moves relative to the image plane during focusing. The first and third lens groups remain stationary with respect to the image plane. This extraction allows high-speed focusing through movement of only the second lens group while the stationary first and third groups maintain stable aberration correction, thereby resolving the contradiction between focusing speed and aberration stability.
Solution Approach 2:
The second lens group acts as an intermediary between the stationary first lens group and the image plane. It has positive refractive power and is specifically designed with lenses having particular Abbe numbers to correct spherical aberration and other aberrations during its movement. This intermediary role allows the second lens group to enable fast focusing while simultaneously maintaining aberration correction, resolving the contradiction between focusing speed and aberration variation.
3Manufacturing precision
If the optical system uses more lenses to correct aberrations, then aberration correction is improved, but the overall length increases
Solution Approach 1:
The third lens group combines multiple lenses with negative refractive power into a compact arrangement that provides effective aberration correction. The conditional expressions specify that the third lens group has negative refractive power and is positioned to correct spherical aberration and other aberrations introduced by the first and second lens groups. This merging of correction functions into a compact third group allows effective aberration correction without significantly increasing the overall length of the optical system.
Solution Approach 2:
The patent specifies particular parameter ranges for the lenses in the third lens group, including negative refractive power and specific Abbe numbers, to optimize aberration correction efficiency. By carefully controlling these parameters, the third lens group achieves effective aberration correction with a compact configuration, resolving the contradiction between aberration correction quality and overall system length.
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 high-speed focusing with reduced variations in aberrations and overall system length, allowing for compact imaging devices with improved focusing capabilities.
Implementation Method 1
an optical system includes a first lens group having positive refractive power, a second lens group having positive refractive power, and a third lens group
Data Source
AI summary
The optical system includes a first lens group having positive refractive power, a second lens group having positive refractive power, and a third lens group, the first, second, and third lens groups being arranged in order from an object side to an image side. The second lens group is configured to move relative to an image plane in an optical axis direction during focusing, and the first and third lens groups are configured to remain stationary with respect to the image plane during focusing. The first lens group includes three negative lenses that are consecutively arranged in the optical axis direction and located closest to an object plane. The second lens group includes two or more lenses.