Imaging Lens Compact Size Fast Focusing Speed
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Solution Overview
Problem
There is a demand for an imaging lens that is compact in size, offers excellent optical performance, and facilitates faster focusing speeds.
Innovation Solution
The imaging lens is configured with a first lens group having a positive refractive power, a second lens group with a negative refractive power that moves during focusing, and a third lens group. This configuration satisfies specific conditional expressions regarding focal lengths, refractive indices, and Abbe numbers to achieve the desired optical performance and size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the lens system is designed to be compact, then the size is reduced, but the focusing speed may deteriorate
Solution Approach 1:
The lens system is divided into three lens groups (G1, G2, G3) with different functions. The second lens group G2 containing the negative lens is designated as the focusing group that moves independently, while the first and third lens groups remain stationary. This segmentation allows the compact overall structure to maintain fast focusing by moving only the necessary portion.
Solution Approach 2:
The patent implements dynamic focusing by making the second lens group G2 movable along the optical axis while keeping the other lens groups fixed. This dynamic configuration enables rapid focusing adjustment within a compact form factor, resolving the contradiction between small size and fast focusing speed.
2Volume of moving object
If the lens system is designed to be compact, then the size is reduced, but the optical performance may deteriorate
Solution Approach 1:
Each lens group is assigned specific optical characteristics: G1 with positive refractive power for initial light convergence, G2 with negative refractive power for focusing adjustment, and G3 with positive refractive power for final image formation. This local optimization of optical properties ensures high optical performance within the compact structure.
Solution Approach 2:
The patent optimizes specific parameters including the focal length ratio (0.3 < f2/f < 1.0), refractive indices (1.8 < Nn < 2.2 for the negative lens), and Abbe numbers (20 < vn < 40) to achieve excellent optical performance. These parameter constraints ensure minimal aberrations and high image quality in the compact lens design.
3Speed
If the lens system uses multiple lens groups for focusing, then the focusing speed is improved, but the device complexity increases
Solution Approach 1:
The patent extracts the focusing function into a dedicated second lens group G2 that is separated from the other lens groups. This extracted focusing group can move independently, enabling fast focusing while simplifying the control mechanism compared to moving the entire lens system or using complex internal focusing mechanisms.
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 proposed imaging lens achieves a compact size while maintaining high optical performance and enabling faster focusing speeds, as demonstrated by the satisfaction of conditional expressions and aberration diagrams.
Implementation Method 1
a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a third lens group G3 having a positive refractive power. During focusing, the first lens group G1 and the third lens group G3 remain stationary with respect to an image plane Sim, and the second lens group G2 moves
Data Source
AI summary
An imaging lens consists of, in order from the object side to the image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group. During focusing, only the second lens group moves. The imaging lens satisfies a conditional expression: −0.5<f/f3<0.38 regarding the focal length f of the imaging lens and the focal length f3 of the third lens group in a state where an object at infinity is in focus.