Four-Element Lens System Aberration Control
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Solution Overview
Problem
Conventional compact optical lens systems, such as those with a three-element or four-element lens structure, fail to meet the increasing demands for high resolution and better image quality in portable electronic devices like smartphones and PDAs, particularly due to issues with peripheral image quality and total track length.
Innovation Solution
A four-element image capturing lens system with specific refractive powers and surface profiles for each lens element, including aspheric surfaces, is designed to optimize image quality by controlling aberrations and reducing the total track length, featuring a first lens with positive refractive power, a second lens with negative refractive power for astigmatism correction, a third lens with positive refractive power for sensitivity reduction, and a fourth lens with negative refractive power for back focal length reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional three-element lens structure is used, then the device maintains a compact size, but the image quality and resolution cannot satisfy high-end requirements
Solution Approach 1:
The lens system is divided into four distinct lens elements with specific refractive powers and surface profiles, allowing each element to contribute to correcting different types of aberrations and improving overall image quality while maintaining a compact form factor
Solution Approach 2:
Different regions of the lens surfaces (paraxial region vs. peripheral region) are designed with different curvatures and profiles. Specifically, the second and fourth lens elements have surfaces that change from concave at the paraxial region to convex at the peripheral region, enabling localized correction of aberrations in different field regions
2Manufacturing precision
If an optical lens system with four-element lens structure is used to improve image quality, then better image quality is obtained, but the total track length becomes too long to maintain a compact size
Solution Approach 1:
The lens elements are designed with specific refractive power parameters and surface curvature parameters that allow for compact spacing. The fourth lens element with negative refractive power and specific surface profile reduces the back focal length, thereby shortening the total track length while maintaining image quality
Solution Approach 2:
The lens elements employ asymmetric surface profiles, particularly the second and fourth elements whose surfaces change curvature sign from paraxial to peripheral regions. This asymmetric design enables compact total track length while correcting aberrations across the field
3Ease of manufacture
If the image-side surface of the second lens element is designed with conventional profile, then manufacturing is simplified, but the image quality of the peripheral region becomes hard to control
Solution Approach 1:
The image-side surface of the second lens element is designed with different curvature characteristics for different regions: concave at the paraxial region for basic focusing and convex at the peripheral region for correcting peripheral aberrations, enabling control of peripheral image quality while remaining manufacturable
Solution Approach 2:
The lens surfaces, particularly the second and fourth elements, employ complex curved profiles that change from concave to convex across the surface. These aspheric surfaces with varying curvature enable precise control of light rays from different field angles, improving peripheral 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
The system achieves improved image quality, reduced sensitivity, and a compact size by effectively distributing refractive power and correcting aberrations, while allowing for flexible material choices between glass and plastic, thus enhancing manufacturing efficiency and cost-effectiveness.
Implementation Method 1
four lens elements with refractive power, in order from an object side to an image side, a first lens element, a second lens element, a third lens element and a fourth lens element
Data Source
AI summary
An image capturing lens system includes four lens elements with refractive power, in order from an object side to an image side, a first lens element, a second lens element, a third lens element and a fourth lens element. The positive first lens element has a convex object-side surface at a paraxial region. The negative second lens element has a concave object-side surface at a paraxial region and an image-side surface changing from concave at a paraxial region to convex at a peripheral region, wherein the surfaces of the second lens element are aspheric. The positive third lens element has a concave object-side surface at a paraxial region and a convex image-side surface at a paraxial region. The negative fourth lens element has an image-side surface changing from concave at a paraxial region to convex at a peripheral region, and the surfaces of the fourth lens element are aspheric.